Biosorption of Toxic Zn(ll) Ion from Water Using Ion Imprinted Interpenetrating Polymer Networks

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赛特尔-诺夫耶尔高级生物资源：酶浓度和酶活性：实验计划表说明书

ENZYME CONCENTRATIONS AND ENZYME ACTIVITY: PLANNING SHEETPurpose∙To investigate how enzyme concentration can affect the initial rate of reaction.∙To develop practical skills.SAFETYWear eye protection, lab coats and disposable gloves.All enzymes are potential allergens and skin contact should be avoided. Any spillages ontothe skin should be washed off immediately. Asthma sufferers may be particularly sensitive,so alert your teacher.Hydrogen peroxide is corrosive. Use with great care avoiding contact with eyes, skin andclothing. Any spillages onto the skin should be washed off immediately.Use the knife with care, cutting on a secure surface.Reducing concentrationIf someone’s pancreatic duct becomes blocked it reduces or prevents the release of pancreatic enzymes into the small intestine. The aim of this activity is to investigate the effect of a reduction in enzyme concentration on the initial rate of reaction. The pancreas releases several enzymes, including proteases, which could be used to investigate the effect of enzyme concentration on initial rate of reaction. Other enzymes, including catalase, could be used to investigate the effect of enzyme concentration on initial rate of reaction. Catalase is not released by the pancreas: it occurs in most cells to break down toxic hydrogen peroxide, the by-product of various biochemical reactions.Why do we measure the initial rate of reaction?At the start of an enzyme experiment in the lab there will be a fixed amount of substrate in the test tube and no product. As the reaction proceeds, the amount of substrate decreases and the amount of product increases. Therefore the chance of a substrate molecule colliding with an enzyme goes down, so the rate of reaction is slower than at the start. For this reason, when carrying out enzyme catalysed reactions, it is the initial rate of the reaction that is the most valid measurement to take; it will give the rate of the reaction under the desired conditions.1 Scientific questions and information researchMilk powder contains a white protein called casein. A white suspension of milk powder clears on the addition of the enzyme trypsin. Hydrogen peroxide is broken down by the enzyme catalase, forming water and oxygen gas.Research relevant information and decide what you think the relationship will be between the enzyme concentration and the initial rate of reaction. Make sure that you understand and explain why we are only interested in the initial breakdown of the substrate. Write down your idea as a hypothesis that you can test. Use scientific ideas to support your prediction.2 Planning and experimental designYou are provided with the following equipment:●Standard acidified protease solution or a cylinder of potato tissue (a source of catalase).●Milk powder or hydrogen peroxide solution (the substrate).●Standard laboratory glassware and apparatus including a ruler, stopclock and thermometer.● A colorimeter and cuvette.NB: Casein will hydrolyse in acid conditions without addition of the enzyme.Plan an experiment that will test your hypothesis. Make sure your plan:∙includes a hypothesis about enzyme concentration and the breakdown of substrate, with a scientific explanation to support your ideas∙includes a procedure that uses suitable apparatus to produce measurements that will validly test your hypothesis∙includes a method that allows you to assess the initial rate of reaction∙identifies the dependent and independent variables and, where possible, controls or allows for other variables∙has a control and replicates, and that you have explained why these are necessary∙says exactly what measurements you will make and how they will be made∙says how you will make sure the results are valid, accurate, precise and repeatable∙identifies any possible sources of error∙includes a risk assessment with any safety precautions you will take.Refer to the Developing Practical Skills Framework in Practical Skills Support for guidance on planning an experiment.Have your plan checked by your teacher/lecturer before starting the experiment.On completion of the experiment make sure you have presented your results in the most appropriate way, and identified and explained any trends or patterns in your results, supporting your statements with evidence from your data. Also, using biological knowledge, you should have commented on any variation and possible errors within the data, and proposed changes to your procedure that would improve the experimental results.The effect of substrate concentrationHaving successfully completed the practical work to determine the effect of enzyme concentration, modify your experimental procedure to show how you would investigate the effect of substrate concentration on initial rate of enzyme reaction.ENZYME CONCENTRATIONS AND ENZYME ACTIVITYPurpose∙ To investigate how enzyme concentration can affect the initial rate of reaction.∙ To develop practical skills.SAFETYEnsure eye protection, lab coats and disposable gloves are worn throughout.All enzymes are potential allergens and skin contact should be avoided. Any spillages ontothe skin should be washed off immediately. If enzyme solutions are made up from solids thisshould not be done by students and precautions should be taken to avoid raising dust.Asthma sufferers may be particularly sensitive.Hydrogen peroxide is corrosive. Directly supervise its use ensuring it is handled with care,avoiding contact with the skin, eyes and clothing. Any spillages onto the skin should be washedoff immediately.Ensure knives are used with care on secure surfaces. Demonstrate a safe method for cutting materials.Notes on the procedureStudents should be given the opportunity to plan this experiment themselves. A planning sheet is provided. The experimental work is placed in the context of the reduced enzyme secretions from the pancreatic duct, which occurs with cystic fibrosis (CF). The use of a protease enzyme would strengthen this link, but there are different enzymes and methods that can be used in this experiment. Students will require some guidance before they start planning, regarding the type of enzyme and substrate to use and a method of assessing the initial rate of reaction. Students could be shown the type of equipment available and a class discussion about what should be included in the practical plan is appropriate. The Developing Practical Skills support provides a framework for the steps in completing an investigation. This can be used to guide students through the process. Once the investigation has been completed students could use the Developing Practical Skills Self-evaluation Sheet to reflect on what they have done in this practical.Two possible methods (A and B) are given below. The methods provided are not fully comprehensive, but provide a starting point if required. Students need to measure initial rate of reaction. This is done by measuring the slope of the time-course graph at each concentration and plotting a summary graph of initial rate against enzyme concentration.Either individually or in pairs students could complete an agreed procedure for one of the concentrations and then share results to complete the summary graph.Some centres have reported very good results for the dried milk experiment, while for others the dried milk powder did not break down. It is always best to check the enzyme activity in advance.In the ICT support there is a datalogging sheet on monitoring an enzyme-catalysed reaction.The Core Practical requires investigation of enzyme and substrate concentration. Having completed the practical investigating enzyme concentration, students can plan how to investigate substrate concentration, which would use a similar procedure with the enzyme concentration remaining the same but varying the substrate concentration. If time is available students could complete this in addition to completing the planning activity.You need:● Milk powder solution● Test tubes, flat-bottomed tubes or conical flasks● Test tube holder● Stopclock ● Standard protease solution 1% ● 5 cm 3 pipettes, syringe or measuring cylinder ● Glassware for diluting enzymesPurpose∙To investigate how enzyme concentration can affect the initial rate of reaction. ∙ To develop practical skills. What do you think will be the effect of reducing the concentration of the protease enzyme on theinitial rate of breakdown of the protein found in milk powder? Use scientific ideas to support your idea (hypothesis).SAFETYWear eye protection, lab coats and disposable gloves.All enzymes are potential allergens and skin contact should be avoided. Any spillages ontothe skin should be washed off immediately. Asthma sufferers may be particularly sensitive,so alert your teacher.Procedure1Pipette 2 cm 3 of protein solution into a cuvette. 2 Pipette 2 cm 3 of the protease solution into the cuvette. Mix thoroughly and immediately put thiscuvette into the colorimeter and start the stopclock.3 Measure absorbance at suitable time intervals for 5 minutes or until there is little change inreaction.4 Discard the content of the cuvette and rinse with distilled water.5 Plot a graph of absorbance against time. Use the graph to determine the initial rate of reaction.This is the initial gradient of the graph and should be the steepest part. Calculate the initial rate bydividing the change in they-axis by the change in the x -axis values and use the units you haveplotted on your y - and x -axes.6 Repeat steps 1 to 5 of the experiment using a range of different enzyme concentrations, ensuringthat other conditions are unchanged. Plot a separate absorbance against time graph for eachenzyme concentration and calculate an initial rate of reaction from each one.7 Present your results in the most appropriate way.8 Identify any trends in your results.9 Explain any trends or patterns, supporting your statements with evidence from your data andusing biological knowledge.10 State a clear conclusion to your work, summarising what you have found out and comment on thevalidity of your conclusion.Comment on the accuracy and precision of your results. Suggest any modifications to your procedure that would improve the experiment.The effect of substrate concentrationHaving successfully completed the practical work to determine the effect of enzyme concentration, modify your experimental procedure to show how you would investigate the effect of substrateconcentration on initial rate of enzyme reaction.You need● Cylinders of potato tissue● Hydrogen peroxide solution● Buffer solution pH 7.2● Distilled water● Boiling tube● Bung and delivery tube● 250 cm 3 beakers● Small beaker● 10 cm 3 syringe barrel● 2 ⨯ 10 cm 3 syringes or graduated pipettes● Short piece of rubber tubing ● Screw clip ● Cork borer ● Measuring cylinder ● Thermometer ● Stopclock ● Glass rod ● Sharp knife ● White tile ● Forceps ● Water bathPurpose∙To investigate how enzyme concentration can affect the initial rate of reaction. ∙ To develop practical skills.Catalase is an enzyme that occurs in most plant and animal cells. It catalyses the reaction:2H2O 2 → 2H 2O + O 2What do you think will be the effect of reducing the concentration of catalase on the initial rate ofbreakdown of the substrate, hydrogen peroxide? Use scientific ideas to support your idea (hypothesis). The initial rate of reaction can be measured by determining the volume of oxygen gas produced in a unit of time using the apparatus shown in Figure 1. Potato tissue provides a source of catalase.SAFETYWear eye protection, lab coats and disposable gloves.Hydrogen peroxide is corrosive. Use with great care avoiding contact with eyes, skin andclothing. Any spillages onto the skin should be washed off immediately.Use the knife with care, cutting on a secure surface. Demonstrate a safe method for cuttingmaterials.Procedure1Set up the apparatus as shown in Figure 1, with the collecting tube filled with water and the screw clip closed. 2Cut 10 discs of potato, each 0.2 mm thick. Place these in the boiling tube with 5 cm 3 of buffer solution. 3 Add 5 cm 3 of hydrogen peroxide solution to the potato discs. Immediately place the bung anddelivery tube firmly into the boiling tube. Place the other end of the delivery tube under thecollecting tube.4 Start a stopclock as soon as the first bubble of oxygen enters the collecting tube from the deliverytube. Collect any gas produced at suitable time intervals for 5 minutes or until there is littlechange in the volume. Shake the boiling tube gently throughout the reaction period to keep thecontents well mixed. Measure the volume of oxygen produced by raising the collecting tube sothat the water level in the tube is level with the surrounding water level in the beaker. Wash outthe boiling tube thoroughly.5Plot a graph of volume of gas produced against time. Use the graph to determine the initial rate ofreaction. This is the initial gradient of the graph and should be the steepest part. Calculate theinitial rate by dividing the change in the y -axis by the change in the x -axis values and use the unitsyou have plotted on your x - and y -axes.6 Repeat steps 1 to 5 of the experiment using a range of numbers of potato discs, ensuring that otherconditions are unchanged. Open the screw clip to refill the collecting tube and then tighten again.Plot a separate volume of gas produced against time graph for each enzyme concentration and calculate an initial rate of reaction from each one.7 Present your results in the most appropriate way.8 Identify any trends in your results.9 Explain any trends or patterns, supporting your statements with evidence from your data andusing biological knowledge.10 State a clear conclusion to your work, summarising what you have found out and comment on thevalidity of your conclusion.11 Comment on the accuracy and precision of your results. Suggest any modifications to yourprocedure that would improve the experiment.Figure 1 Apparatus for investigating catalase activity.The effect of substrate concentrationHaving successfully completed the practical work to determine the effect of enzyme concentration, modify your experimental procedure to show how you would investigate the effect of substrate concentration on initial rate of enzyme reaction.ENZYME CONCENTRATIONS AND ENZYME ACTIVITYPurpose∙To investigate how enzyme concentration can affect the rate of reaction.∙To develop practical skills.SAFETYWear eye protection, lab coats and disposable gloves.All enzymes are potential allergens and skin contact should be avoided. Enzyme powdersare irritants and potential allergens. If enzyme solutions are made up from solids this shouldnot be done by students and precautions should be taken to avoid raising dust. Avoid inhalation of powder and wear eye protection and gloves when handling powders. Rinsewith lots of water if you come in contact with the enzymes. All spills should be moistenedand wiped up immediately. Asthma sufferers may be particularly sensitive. Hydrogen peroxide is corrosive; use with great care and avoid contact with skin, eyes and clothing.The requirements for this practical will depend on whether the students undertake the planning themselves or are guided. Two basic experimental procedures are provided as a starting point and possible requirements are detailed below. Note that the requirements are given per student per concentration investigated. Students are likely to want to investigate five concentrations each. Procedure A: Using milk and trypsinRequirements per student orgroup of studentsNotesFor each concentration studentsinvestigate, they will need:5 cm3 casein or milk powder suspension (5%) To make milk suspension use 5 g milk powder in 100 cm3 water. Marvel® has been found to be the best milk powder to use: it is almost fat-free.5 ml trypsin solution Mix 0.5 g trypsin powder in 100 cm3 water. Add enough alkali (forexample, dilute sodium hydroxide) while mixing it up to produce a pHof 9. It is recommended to use a buffer solution to produce a morestable pH. If making up enzyme solutions do not heat to dissolve.Students will also need to dilute this standard solution to give 0.1%,0.2%, 0.3% and 0.4% solutions.Test tubes, flat-bottomed tubes, orconical flasksTest tube holderStopclockTwo 5 cm3 pipettes syringes ormeasuring cylinders50 cm3 beakerEye protectionProcedure B: Using catalase and hydrogen peroxideNotesRequirements per student orgroup of studentsCylinder of potato tissue Students can cut these for themselves using a cork borer and whitetile.Hydrogen peroxide solution 20 volume.Buffer solution pH 7.2Distilled waterBoiling tubeBung and delivery tube250 cm3 beakersSmall beaker10 cm3 syringe barrel To collect the oxygen evolved, a small measuring cylinder could beused as an alternative, but the syringe barrel with a rubber tube andscrew clip allows the collecting tube to be filled with water very easilyby loosening the screw clip.2 10 cm3 syringes or graduatedpipettesShort piece of rubber tubingScrew clipMeasuring cylinderThermometerStopclockGlass rodCork borer To cut cylinders of potato.Sharp knifeWhite tileForcepsWater bath Beaker of water to maintain the reaction tube at a constanttemperature would be adequate.。

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The role of natural and synthetic zeolites as feed additives on the prevention and/or the treatment of certain farmanimal diseases:A reviewD.Papaioannou,P.D.Katsoulos,N.Panousis *,H.KaratziasClinic of Productive Animal Medicine,School of Veterinary Medicine,Aristotle University of Thessaloniki,54124Thessaloniki,GreeceReceived 4April 2005;received in revised form 12May 2005;accepted 12May 2005Available online 28June 2005AbstractThe present review comments on the role of the use of zeolites as feed additives on the prevention and/or the treatment of certain farm animal diseases.Both natural and synthetic zeolites have been used in animal nutrition mainly to improve performance traits and,based on their fundamental physicochemical properties,they were also tested and found to be eﬃcacious in the prevention of ammonia and heavy metal toxicities,poisonings as well as radioactive elements uptake and metabolic skeletal defects.During the last decade,their utilization as mycotoxin-binding adsorbents has been a topic of considerable interest and many published research data indicate their potential eﬃcacy against diﬀerent types of mycotoxins either as a primary material or after speciﬁc modiﬁcations related to their surface properties.Ingested zeolites are involved in many biochemical processes through ion exchange,adsorption and catalysis.Recent ﬁndings support their role in the prevention of certain metabolic diseases in dairy cows,as well as their shifting eﬀect on nitrogen excretion from urine to faeces in monogastric animals,which results in lower aerial ammonia concentration in the conﬁnement facilities.Moreover,new evidence provide insights into potential mechanisms involved in zeolites supporting eﬀect on animals suﬀered from gastrointestinal disturbances,including intestinal parasite infections.All the proposed mechanisms of zeolites Õeﬀects are summarized in the present review and possible focus topics for further research in selected areas are suggested.Ó2005Elsevier Inc.All rights reserved.Keywords:Zeolites;Animal health;Prevention;Treatment1.IntroductionZeolites are crystalline,hydrated aluminosilicates of alkali and alkaline earth cations,consisting of three-dimensional frameworks of SiO 4À4and AlO 5À4tetrahedra linked through the shared oxygen atoms.Both natural and synthetic zeolites are porous materials,character-ized by the ability to lose and gain water reversibly,to adsorb molecules of appropriate cross-sectional diame-ter (adsorption property,or acting as molecular sieves)and to exchange their constituent cations without majorchange of their structure (ion-exchange property)[1,2].The exploitation of these properties underlies the use of zeolites in a wide range of industrial and agricultural applications and particularly in animal nutrition since mid-1960s [3].Many researchers have proved that the dietary inclu-sion of zeolites improves average daily gain and/or feed conversion in pigs [1,4–13],calves [1,7],sheep [7,14–16],and broilers [17–19].Zeolites also enhance the reproduc-tive performance of sows [1,20,21],increase the milk yield of dairy cows [22,23]and the egg production of laying hens [24,25]and have beneﬁcial eﬀects on egg weight and the interior egg characteristics [24–26].How-ever,the extent of performance enhancement eﬀects is related to the type of the used zeolite,its purity and1387-1811/$-see front matter Ó2005Elsevier Inc.All rights reserved.doi:10.1016/j.micromeso.2005.05.030*Corresponding author.Tel.:+302310994501;fax:+302310994550.E-mail address:panousis@vet.auth.gr (N.Panousis)./locate/micromesoMicroporous and Mesoporous Materials 84(2005)161–170physicochemical properties,as well as to the supplemen-tation level used in the diets.Besides,the particle size of the zeolitic material,crystallite size and the degree of aggregation,as well as the porosity of individual parti-cles determine the access of ingestaﬂuids to the zeolitic surface during passage across gastrointestinal tract and strongly aﬀect its ion exchange,adsorption and catalytic properties.Table1summarizes the possible mechanisms by which zeolites may exert their performance promot-ing properties in farm animals.Apart from the positive eﬀects on animalsÕperfor-mance,dietary supplementation of zeolites appears to represent an eﬃcacious,complementary,supportive strategy in the prevention of certain diseases and the improvement of animalsÕhealth status.The aim of the present review article is to address the data concerning the inﬂuence of the in-feed inclusion of natural and syn-thetic zeolites on certain diseases of farm animals,to summarize the proposed mechanisms of zeolitesÕeﬀects and to suggest possible focus topics for further research in selected areas.2.Ameliorative eﬀect on the consequences of mycotoxicosesIn the recent years,high incidence rates of contami-nation of cereal grains and animal feed with mycotoxins are reported worldwide[38].One of the latest ap-proaches to this global concern has been the use of nutritionally inert adsorbents in the diet that sequester mycotoxins,thus reducing intestinal absorption and, additionally,avoiding toxic eﬀects for livestock and the carry-over of toxin compounds to animal products. For this purpose,phyllosilicates such as hydrated sodium calcium aluminosilicates(HSCAS)and benton-ite––which consist of layered crystalline structures and possess similar physicochemical properties with zeo-lites––have beenﬁrst used successfully in poultry,pig, sheep,cattle and laboratory animals[33,34,39–47].Apart from phyllosilicates,the use of zeolites has shown,lately,very promising results as well.In general, adsorption process on binders is strongly related to charge distribution,pore dimensions and accessible sur-face area of the adsorbent,as well as to polarity,solubil-ity and molecular dimensions of the certain mycotoxin which is to be adsorbed[46].Molecular sizes of aﬂatox-ins range from5.18A˚(B1and B2)to6.50A˚(G1and G2) and only zeolites with entry channels wide enough to permit the diﬀusion of aﬂatoxin molecules to the intra-crystalline structure are capable of demonstrating a clear sequestering eﬀect.Clinoptilolite,a natural zeolite,has high adsorption indexes in vitro,more than80%,for aﬂatoxins B1[48,49]and G2[48]and the adsorption pro-cess begins with a fast reaction whereby most of the toxin is adsorbed within theﬁrst few minutes[48].On the contrary,Lemke et al.[50]conducted a variety of in vitro adsorption studies and reported a limited degree of clinoptilolite ability to bind aﬂatoxin B1eﬀectively. According to them,adsorbent materials should be checked through a multi-tiered system of in vitro tests in order potential interactive factors,such as intestinal physicochemical variables and feed components,to be precluded.Indeed,a previous in vitro study had demon-strated average aﬂatoxin retention in natural zeolites of 60%,but also a nitrogen compound-related adsorbent eﬀectiveness,when liquid media quality parameters had been taken into account[51].The in vivo eﬃcacy of zeolites to ameliorate the consequences of aﬂatoxico-sis,mainly in poultry,has also been veriﬁed in many cases(Table2).In the case of phyllosilicates,the results of in vitro mycotoxin–clay interaction tests suggest the existence of areas of heterogenous adsorption aﬃnities onto sur-face,the presence of diﬀerent adsorption mechanisms or both[57].Nevertheless,the formation of strong bonds by chemisorption and the interaction of b-car-bonyl group of aﬂatoxin B1with the uncoordinated edge site aluminum ions in these adsorbents have been suggested as the binding mechanism which interprets their well-established high aﬃnity for aﬂatoxin B1 [39,58,59].Although the exact binding mechanisms of zeolites on aﬂatoxins have not been determined the pos-sibility to act through similar with phyllosilicates mech-anism cannot be precluded and should be investigated.As far as other mycotoxins are concerned,mineral adsorbents exert a lower eﬃcacy against mycotoxins containing less polar functional groups,which are required for eﬃcient chemisorption on hydrophilic negatively charged mineral surfaces to occur.This limi-tation can be overcome by the use of chemically modi-ﬁed clays.Modiﬁcations consist of alterations ofTable1Proposed mechanisms involved in animalsÕperformance promoting properties of the dietary use of zeolitesMechanismsAmmonia binding eﬀect Elimination of toxic eﬀects of NHþ4produced by intestinal microbial activity[8,10]Fecal elimination of p-cresol Reduction of the absorption of toxic products of intestinal microbial degradation,such as p-cresol[27] Retarding eﬀect on digesta transit Slower passage rate of digesta through the intestines and more eﬃcient use of nutrients[1,25,28] Enhanced pancreatic enzymes activity Favorable eﬀect on feed components hydrolysis over a wider range of pH,improved energy and protein retention[29,30]Aﬂatoxin sequestering eﬀect Elimination of mycotoxin growth inhibitory eﬀects[31–37]162 D.Papaioannou et al./Microporous and Mesoporous Materials84(2005)161–170surface properties resulting in an increased hydropho-bicity,by exchange of structural charge-balance cations with high molecular weight quaternary amines.In vitro results have veriﬁed the binding eﬃcacy of modiﬁed montmorilonite and clinoptilolite against zearalenone and ochratoxin A[60,61].However,naturally occurring clays also exert a moderate binding eﬃcacy against mycotoxins,other than aﬂatoxins,as evidenced for zearalenone and ochratoxin A by in vitro[57]andﬁeld trials[62,63],as well as for cyclopiazonic acid in exper-iments with broilers[45].Remarkable conclusions related to zeolitesÕeﬃcacy against zearalenone toxicosis have also been drawn by in vivo studies.Feeding zearalenone to rats,Smith[64] demonstrated that the dietary use of a synthetic anion exchange zeolite could alter the faecal and urinary excre-tory patterns of zearalenone due to the elimination of its intestinal absorption.Recently,the dietary use of a clin-optilolite-rich tuﬀwas also eﬀective in decreasing zearal-enone and a-zearalenole excretion in pigs fed diets contaminated with500ppb zearalenone[65].Addition-ally,in aﬁeld-case of zearalenone toxicosis with mean concentrations of660ppb,Papaioannou et al.[20] reported that the supplementation of a clinoptilolite rich tuﬀat the rate of2%in the ration of pregnant sows im-plied a rather protective role against the consequences of zearalenone ingestion,as evidenced by the improvement of indicative performance traits.Similar results were also obtained in swine with the dietary use of a modiﬁed clinoptilolite–healandite rich tuﬀat0.2%and with zea-ralenone concentration exceeding3.5ppm[66].Apart from surface interactions,the in vivo eﬃcacy of mineral adsorbents against zearalenone could also re-sult from other implicating mechanisms.The entero-he-patic circulation of zearalenone and its derivatives in pigs retards their elimination and enhances the duration of adverse eﬀects[67].Whether certain types of zeolites are able to aﬀect the entero-hepatic cycling of zearale-none,thus counteracting the toxic eﬀects of its biological action,is a hypothesis that awaits further research, although there is evidence of Ca-enriched clinoptiloliteÕs high aﬃnity to the bile acids in the intestinal tract[68].3.Supportive eﬀect on diarrhoea syndromeThere is an abundance of published data which indi-cate that the dietary use of natural zeolites reduces the incidence and decreases the severity and the duration of diarrhoea in calves[1,69–72]and pigs[1,5,13,72–75]. The exact mechanism of zeolitesÕeﬀect is not quite clear so far,although there is evidence that the use of zeolites may eliminate various predisposing and/or causative fac-tors which are associated in the culmination of intestinal disturbances in an interactive way.Apart from zeolitesÕretarding eﬀect on intestinal passage rate[1]and their water adsorption property,which leads to the appear-ance of drier and more compact faeces,as in the case of phillipsite[75]or clinoptilolite[76],Vrzgula et al.[71]also proposed that the ameliorative eﬀect on diar-rhoea syndrome of calves might result from either the alteration of metabolic acidosis,through eﬀects on os-motic pressure in the intestinal lumen,or the increased retention of the enteropathogenic Escherichia coli.As far as we know,there is no evidence in the available lit-erature for retention of enteropathogenic E.coli on the outer surface of zeolite particles.However,clinoptilolite and mordenite are capable to adsorb and partially inac-tivate the thermo-labile(LT)E.coli enterotoxin in vitro, thus constricting its attachment to the intestinalTable2In vivo studies concerning the eﬀect of the dietary use of zeolites during aﬂatoxicosesType of zeolite Dietary inclusion rate(%)Animal model ObservationsClinoptilolite1Broilers Growth depression caused by2.5ppm aﬂatoxin(aﬂ)was alleviated by15%[31] Clinoptilolite5Geese Prophylactic eﬀect on growth rate and liver enzymatic activity[32]Mordenite0.5Broilers Reducing eﬀect on toxicity of aﬂ(3.5mg kgÀ1diet)as indicated byweight gain and changes in uric acid and albumin concentrations[33] Clinoptilolite0.5Weaned piglets Growth inhibitory eﬀects and alterations of liver enzyme activity inducedby500ppb aﬂwere prevented[34]Synthetic zeolite0.5Broilers No signiﬁcant eﬀect on biochemical or haematological indexes whenadministered simultaneously with2.5mg aﬂkgÀ1diet[52]Clinoptilolite0.5Pregnant rats No eﬀect on maternal and developmental toxicities of aﬂ(2mg kgÀ1body weight)[53]Clinoptilolite5Quail chicks Growth inhibitory eﬀects of2mg kgÀ1diet diminished by70%[35] Clinoptilolite 1.5Broilers Growth inhibitory eﬀects of100ppb aﬂdiminished over a studyperiod of42days[36]Clinoptilolite 1.5–2.5Broilers Adverse eﬀects of2.5mg kgÀ1diet on biochemical and haematologicalproﬁles were reduced[54]Zeolite NaA1Broilers Protection against growth inhibitory eﬀects of2.5mg kgÀ1diet[37] Clinoptilolite 1.5–2.5Broilers Moderate to signiﬁcant decrease of incidence and severity of certaintarget-organs degenerative changes induced by2.5mg aﬂkgÀ1diet[55] Clinoptilolite2Laying hens Signiﬁcant decrease in liver mycotoxin concentration and liver weightduring aﬂatoxicosis caused by2.5mg kgÀ1diet[56]D.Papaioannou et al./Microporous and Mesoporous Materials84(2005)161–170163cell-membrane receptors[77].Furthermore,the adsorp-tion capacity of clinoptilolite and mordenite has been proved to be higher than94%for virions of bovine rota-virus and coronavirus,although infectivity level of zeolite–virus complex seems to remain unchanged[78]. Interactions among virions and the outer surface of adsorbent particles have been proposed,since the former have dimensions considerably larger(60–80nm and 60–220nm for rota-and coronavirus particles,respec-tively)than the entry channels of the aforementioned zeolites.In a more recent study of Rodrigues-Fuentes et al.[68],dealing with the development and the properties of an anti-diarrhoeic drug for humans based on clinop-tilolite,zeolite had no eﬀect on rate of passage of inges-ta,neither acted as a water adsorbent.Instead,they proposed that the anti-diarrhoeic eﬀect of clinoptilolite is due to the adsorption of(i)bile acids,‘‘one of the endogenic causes of diarrhoea’’,(ii)aﬂatoxin B1,‘‘a mycotoxin that produces severe toxicity in animals and humans’’and(iii)glucose,‘‘whose high content in intes-tinalﬂuid acts as an irritant factor and whose transport through the intestinal cells is reversed during diarrhoea’’.Concerning the newborn animals,the administration of zeolites appears to reduce the incidence of diarrhoea through the enhancement of passive immunity,as they increase the net absorption of colostrum immunoglobu-lins in calves[71,79,80]and pigs[81].Intestinal hypersensitivity to feed antigens or the mal-absorption syndrome,induced by a low enzyme activity, can both predispose to post-weaning infectious enteritis in pigs.According to Papaioannou et al.[13],clinoptil-olite has the ability to adsorb dietary substances,which may result in intestinal hypersensitivity phenomena[82], or to support the maintenance and even the restoration of the digestive enzyme activity in newly weaned piglets. This should also be evaluated in future studies as an additional explanation for clinoptilolitesÕminimising ef-fect on diarrhoea syndrome.4.Prevention of metabolic diseases in dairy cowsMilk fever and ketosis are of the most common metabolic diseases in high producing dairy cows.In the recent years,a number of experiments have been con-ducted in order to control these diseases using zeolites as feed additives.The results of these experiments are very promising but further investigation is required to deﬁne the exact mechanisms of zeolitesÕaction.k feverInitially,a series of experiments has been conducted in order to study the potential use of synthetic zeolite A for the prevention of milk fever in dairy cows.The objective of these experiments was to reduce the bio-availability of dietary Ca in the gastrointestinal tract by the administration of synthetic zeolite A,based on the evidence that one of the best ways to prevent milk fever is to feed cows with low calcium diets during the dry period[83–87].The results obtained were satisfac-tory as the administration of synthetic zeolite A,either as an oral drench or supplemented to the total mixed ra-tion,during the dry period reduced the bioavailability of dietary Ca and eﬃciently protected against milk fever, by stimulating Ca-homeostatic mechanisms prior to par-turition[88–93].Furthermore,Thilsing-Hansen et al.[92]proposed that the best ratio zeolite/Ca for the pre-vention of milk fever was10–20and that zeolite had the same eﬃciency either administrated for the last4 or2weeks of the dry period.More recently,Katsoulos et al.[94]showed that clin-optilolite was eﬀective in the prevention of milk fever as well.The incidence of milk fever was signiﬁcantly lower in cows that were receiving a concentrate supplemented with clinoptilolite at the level of2.5%(5.9%)during the last month of the dry period and the onset of lactation compared to the animals in the control group(38.9%), which were not receiving clinoptilolite,whereas was not signiﬁcantly diﬀerent than those that were receiving 1.25%clinoptilolite(17.6%)with the concentrates at the same period.The authors suggested that clinoptilolite might have had similar eﬀect with zeolite A in activating Ca homeostatic mechanisms prior to parturition.As a consequence,the animals receiving2.5%clinoptilolite responded faster and more eﬃciently in the drop of serum Ca observed at the day of calving and did not show any clinical signs of milk fever the following days. However,the exact mechanism for this positive eﬀect of clinoptilolite is currently unknown and should be fur-ther investigated.4.2.KetosisThe best strategy to prevent ketosis in dairy cows is to improve the energy uptake both in the dry period and the onset of lactation[95].According to Katsoulos et al.[23],the use of clinoptilolite has been shown to be eﬀective in improving the energy balance at this critical period as they observed that feeding dairy cows on a diet supplemented with clinoptilolite at the level of2.5%of the concentrate feed,resulted in signiﬁcantly lower incidence of ketosis(5.9%)during theﬁrst month after parturition,compared to the control group(38.9%) and the group of the animals receiving a concentrate supplemented with1.25%clinoptilolite(35.3%).These researchers suggested that clinoptilolite improved the energy status of the cows,either via prepartum enhance-ment of propionate production in rumen or through the improvement of the post-ruminal digestion of starch.164 D.Papaioannou et al./Microporous and Mesoporous Materials84(2005)161–1705.Protective role in intoxications and poisonings5.1.Ammonia toxicityWhite and Ohlrogge[96]ﬁrst stated that ammonium ions formed by the enzyme decomposition of non-pro-tein nitrogen were immediately ion exchanged into the zeolite structure and held there for several hours until released by the regenerative action of Na+,entering the rumen in saliva during the after-feeding fermenta-tion period.From both in vitro and in vivo experimentsthey found that up to15%of the NHþ4in the rumencould be taken up by the zeolite.These observations were the causation for the conduction of many experi-ments in order to determine the inﬂuence of zeoliteson rumen NHþ4concentration and their potential usefor the counteraction of the toxic eﬀects of urea inclu-sion in ruminantsÕrations.Hemken et al.[97]showed that supplementation of 6%clinoptilolite,in the ration of dairy cows containing urea,signiﬁcantly reduced rumen NH3concentration. The same trend was observed by the dietary addition of5%clinoptilolite in steers[98]and lambs[99].Fur-thermore,clinoptilolite was eﬀective in reducing rumen ammonia concentration even when no urea was present in the ration of steers receiving a high concentrate diet, and that this reduction was linearly associated to the percentage of clinoptilolite inclusion[100].Nestorov [101]referred that simultaneous administration of clin-optilolite and urea in sheep protects rumenﬂora from toxic eﬀects of ammonia by inhibiting the reduction of microbiota population.In contrast to the former observations,Bergero et al.[102]and Bosi et al.[103]found that daily administration of250g or200g of clinoptilolite, respectively,in dairy cows did not aﬀect rumen NHþ4 concentration.The same result had the dietary inclu-sion of2%synthetic zeolite A in dairy cows ration [104]and5%clinoptilolite in steers receiving a high roughage diet[98].The binding of NHþ4to zeolites has been noted in pigsas well,and many researchers suggested this action as the possible mechanism for the observed improved per-formance of the animals receiving zeolites.There are evi-dences that clinoptilolite elevates nitrogen excretion in feces[8,105]and reduces the ammonia concentration in blood serum[8,10,106],when supplemented to the basal diets of pigs.Furthermore,Pond et al.[10]and Yannakopoulos et al.[12]found that clinoptilolite reduced the weight of the organs involved in the metab-olism of ammonia(liver and kidneys),as the conse-quence of the reduced ammonia concentration in the gastrointestinal tract.Such observations result fromthe direct binding of NHþ4to zeolites,as clinoptilolitehas no adverse eﬀect on the ureolytic bacteria of the large intestine and urease activity[107]anophosphate poisoningThe dietary use of clinoptilolite appears to be eﬀective in the prevention of organophosphates poisoning. Experiments in sheep have shown that the oral adminis-tration of clinoptilolite at the dose of2g/kg of body weight,earlier or simultaneously with an organophos-phate(VX),partially protects from poisoning by inhib-iting the decrease in cholinesterase activity[108]and by protecting rumenﬂora[109].The protective eﬀect of clinoptilolite on cholinesterase activity has been ob-served in mice receiving higher doses of organophos-phates as well[110,111].5.3.Heavy metal toxicity and adsorption of radioactive elementsZeolites,due to their high ion-exchange capacity, have been used eﬀectively for the prevention of heavy metal toxicity in animals.Pond et al.[112]found that clinoptilolite protects growing mice from lead(Pb)tox-icity when added to their ration in such quantities that the ratio clinoptilolite/Pb to be10/1.According to Pond et al.[113],similar protection is provided in swine as well.The selectivity of clinoptilolite for cadmium(Cd) and Pb has been studied in vitro in order to be investi-gated whether its use reduces the levels of these elements in rumen and abomasalﬂuid.The experiments showed that clinoptilolite bent the91%of Pb and the99%of Cd in rumenﬂuid within24h,and in the abomasalﬂuid the94%of Pb within less than1h[114].The toxic eﬀects of long-term ingestion of Cd(100ppm CdCl2)on female rats and their progeny were not diminished by the simul-taneous feeding of a clinoptilolite-rich tuﬀat5%in the diet[115].Adversely,the eﬃcacy of clinoptilolite against Cd toxicity has been proved in pigs by the same authors who observed that3%clinoptilolite supplementation prevented the cadmium-induced iron deﬁcient anemia in growing swine that were receiving150ppm CdCl2 [116].The results of these experiments suggest the feasi-bility of using zeolites and mainly clinoptilolite as a feed additive in the prevention of certain types of heavy metal intoxications in farm animals or in aquatic biolog-ical systems,as is the case in the study of Jain[117], where is ascertained the capacity of zeolite to enhance the removal of Pb from water,thus decreasing its avail-ability to the teleostﬁsh Heteropneustes fossilis.Apart from heavy metals,zeolites can also bind radioactive elements,thus being suggested as a means of altering their uptake and excretion from the body. Zeolitic matrix exchanges radio-nuclides in the gastroin-testinal tract and is excreted by normal processes,there-by eliminating radioactive elementsÕassimilation into the body.Arnek and Forsberg[118]proved the selectiv-ity of some natural zeolites such as clinoptilolite, chabazite and modernite for cesium and GomonajD.Papaioannou et al./Microporous and Mesoporous Materials84(2005)161–170165et al.[119]the selectivity of clinoptilolite for strodium and zirconium.Phillippo et al.[120]showed that the dietary use of clinoptilolite may constitute a simple and cost-eﬀective method for minimizing the adsorption of radioactive cesium by sheep grazing contaminated pastures,although there might be no eﬀect on cesium already been built-up in the body due to a previous exposure.Furthermore,Forsberg et al.[121]observed that the administration of mordenite in sheep and goats increased the excretion of cesium with feces and reduced its accumulation in tissues.On the other hand,Rachu-bik and Kowalski[122]demonstrated that synthetic zeolite-enriched diets exerted an inconsistent pattern of radiostrontium assimilation in the bone tissue and liver or kidneys of rats intragastrically dosed with an aqueous solution of90SrCl2.5.4.Copper toxicityIvan et al.[123]observed that the inclusion of ben-tonite,a phyllosilicate,in the ration of sheep at the rate of0.5%signiﬁcantly reduced the Cu concentration in liver and suggested the use of this material in order to prevent copper poisoning.In contrast,clinoptilolite does not seem to be eﬀective,as Pond[124]found that the addition of2%clinoptilolite to the basal diet of sheep containing10or20ppm Cu did not protect against the toxic signs of Cu and increased the mortality in lambs fed the diet with20ppm Cu.A lack of any ef-fect on liver Cu accumulation was also found in growing pigs which were on diets supplemented with0.5%syn-thetic zeolite A and250ppm Cu[125].Clinoptilolite was expected to exchange Cu in the lumen of the intes-tine,thereby decreasing the toxicity of excess Cu for sheep,whose tolerance for Cu is low compared with that of other food animals.However,such action was not observed probably due to a shift in ion-exchange relativeto Cu and NHþ4or to some other complex interaction,which resulted in a net increase in Cu available for absorption from the intestinal tract[124].The optimum ratio of clinoptilolite to Cu in the diet for reducing the intestinal absorption of the latter has not been deter-mined,but such information,according to Pond[126], is needed in order to establish appropriate levels of die-tary clinoptilolite supplementation.6.Impact on parasite infectionsConsidering the potential eﬃcacy of zeolites against parasite infections,the results of the experimentsﬁrst conducted in rats were encouraging for their use in other animal species as well.According to Wells and McHugh [127],the administration of clinoptilolite at the rate of 10%of a conventional diet facilitated the removal of parasites from the intestinal lumen of rats infected with the nematode Nippostrongylus brasiliensis.Furthermore, Wells and Kilduﬀ[128]observed a more accelerated intestinal a-D-glucosidase and aminopeptidase activity restitution in rats fed a commercial diet supplemented with clinoptilolite(5%)and recovering from N.brasilien-sis infection.Conﬁrming the observations in rats,Deli-giannis et al.[129]recently proved the eﬃcacy of clinoptilolite against parasite infections in growing lambs.They showed that feeding lambs,primarily infected with a single dose of gastrointestinal(GI) nematodes,with a concentrate mixture containing3% clinoptilolite signiﬁcantly decreased their total worm burden and faecal egg counts per capita fecundity and demonstrated that clinoptilolite supplementation re-duced the establishment of GI nematodes and resulted in a good performance of the animals.Interestingly,zeolites have also been tested as anthel-mintic loaded carriers,through retarding drug release and prolonging its therapeutic action.Sustained-release mechanism implies a slow desorption of the drug mole-cules from the external surface and the internal zeolitic cavities,as they are progressively replaced by host pro-teins and water molecules,respectively,during the intes-tinal transport of the drug-zeolite compound.Promising results were obtained,atﬁrst,as regards tetramisole-loaded synthetic zeolite Y[130]and recently,pyrantel-and fenbendazole-loaded synthetic zeolite Y in rats infested with N.brasiliensis and dichlorvos-loaded zeo-lite Y in pigs infected with Ascaris suum[131].In the case of tetramisole and dichlorvos,anthelmintic mole-cules are small enough toﬁt through the entry channels of zeolite Y(windows of7.4A˚),while fenbendazole loading requires an initial partial dealumination of the zeolitic carrier and large pyrantel molecules allow only outer surface loading to occur.7.Prevention of metabolic skeletal defectsThe dietary inclusion of synthetic zeolite A(at the rates of0.75%or1.5%)in broilers which are on a diet with inadequate or marginal levels of calcium results in an increase of bone ash content along with a reduc-tion of rachitic lesions[132].Accordingly,the incorpora-tion of zeolite A in the same diets at1%exerts a clear beneﬁcial eﬀect in reducing the incidence of tibial dys-chondroplasia[132–134].Although tibial dyschondro-plasia is a metabolic cartilage disease which represents the endpoint of several mechanisms,the incidence is in-creased when high dietary levels of phosphorus are used [135]or when dietary calcium is lower than0.85%[136]. Similarly,the beneﬁcial eﬀect of zeolite A is inconsistent and largely depends on the dietary level of calcium. According to Watkins and Southern[137],the dietary use of0.75%zeolite A in broilers is accompanied by alterations in mineral absorption and tissue distribution,166 D.Papaioannou et al./Microporous and Mesoporous Materials84(2005)161–170。

外研版英语初二上学期试题及解答参考(2024年)

2024年外研版英语初二上学期复习试题及解答参考一、听力部分（本大题有20小题，每小题1分，共20分）1、Listen to the conversation and choose the best answer to the question you hear. Question: What is the weather like today?A. SunnyB. RainyC. CloudyD. WindyAnswer: AExplanation: The woman says, “It’s a sunny day today,” which indicates that the weather is sunny.2、Listen to the dialogue and complete the following sentence with the missing word you hear.Question: The man is planning to___________this weekend.A. go to the beachB. stay at homeC. visit a friendD. go shoppingAnswer: CExplanation: The man says, “I’m planning to visit a friend this weekend,”which is the missing word in the sentence.3、You are listening to a conversation between two students in the library.A. The man is borrowing a book.B. The woman is returning a book.C. They are discussing a book they recently read.D. The man is asking for help finding a book.Answer: DExplanation: In the conversation, the man says, “Excuse me, could you help me find the book on ancient civi lizations?” This indicates that he is asking for help finding a book, making option D the correct answer.4、You are listening to a short dialogue at a bookstore.A. The woman is looking for a novel.B. The man is recommending a non-fiction book.C. The woman is asking for help with a school project.D. The man is suggesting a book for a gift.Answer: BExplanation: The woman says, “I need a book on environmental issues for my science class.” The man responds by recommending, “How about ‘The Green Planet’? It’s a great overview of environmental science.” This shows that the man is suggesting a non-fiction book, making option B the correct answer.5.You are listening to a conversation between a student and a teacher.Student: Hello, Miss White. How was your weekend?Teacher: Oh, it was quite busy. I went hiking with my friends. How about you? Student: I stayed at home and watched some movies. I watched a comedy and a horror movie. Which one did you like more?Teacher: I preferred the comedy because it was funny and relaxing.Question: What did the teacher prefer to do during the weekend?A) Watch moviesB) Go hikingC) Stay at homeD) Visit a friendAnswer: B) Go hikingExplanation: The teacher mentioned that she went hiking with her friends, so the correct answer is B) Go hiking.6.You are listening to a radio program about healthy eating habits.Host: Today, we’re discussing the importance of eating a balanced diet. Dr. Smith, can you explain why it’s important to include fruits and vegetables in our daily meals?Dr. Smith: Absolutely. Fruits and vegetables are rich in vitamins, minerals, and antioxidants. They help boost our immune system, improve digestion, and reduce the risk of chronic diseases like heart disease and cancer.Question: What are the main benefits of eating fruits and vegetables according to Dr. Smith?A) Boosting the immune system and improving digestionB) Losing weight and reducing stressC) Increasing energy levels and improving memoryD) Enhancing physical appearance and reducing the risk of chronic diseasesAnswer: A) Boosting the immune system and improving digestionExplanation: Dr. Smith explained that fruits and vegetables help boost the immune system and improve digestion, so the correct answer is A) Boosting the immune system and improving digestion.7、Listen to the conversation and choose the best answer to complete the sentence.A) They are discussing the weather.B) They are planning a trip.C) They are talking about a book.Question: What are the speakers mainly talking about?Answer: BExplanation: The conversation is about planning a trip, which is indicated by the phrases like “We should go there in the summer” and “It’s a great place to visit.”8、Listen to the dialogue and answer the question.Question: Why does the man suggest visiting the museum?A)He thinks it’s a waste of time.B)He believes it will be an educational experience.C)He doesn’t want to go anywhere else.Answer: BExplanation: The man suggests visiting the museum because he mentions that it will be “a good opportunity to learn something new,” indicating that it’s an educational experience.9、You are listening to a conversation between two friends, Tom and Lily. They are talking about their weekend plans.Tom: Hey Lily, do you have any plans for this weekend?Lily: Well, actually, I’m planning to go hiking with a group of friends. How about you, Tom?Tom: That sounds fun! I was thinking of visiting the city museum. What do you think?Lily: That’s a great idea! Maybe we can go together after your visit to the museum.Question: What is Lily planning to do this weekend?A. Visit the city museum.B. Go hiking with friends.C. Go shopping.D. Watch a movie.Answer: BExplanation: In the conversation, Lily says, “Well, actually, I’m planning to go hiking with a group of friends.” This means that she is planning to go hiking this weekend.10、You are listening to a news report about a new research study.News Anchor: According to a recent research study, scientists have discovered a new way to treat cancer. This new treatment has shown promisingresults in early trials.Interviewer: That’s amazing! Can you tell us more about this new treatment?Scientist: Sure, this new treatment involves using a combination of natural substances to target and destroy cancer cells. It’s a non-toxic approach that has fewer side effects compared to traditional treatments.Question: What is the main topic of the news report?A. A new way to treat cancer.B. The benefits of natural substances.C. The history of cancer research.D. The side effects of traditional treatments.Answer: AExplanation: The news report starts with the statement, “According to a recent research study, scientists have di scovered a new way to treat cancer.” This clearly indicates that the main topic of the report is about a new way to treat cancer.11.W: Hi, John! Are you ready for the English test this week?M: Yeah, I’ve been studying hard for it. I think I’m prepared.Q: What does John think about the English test?A: He thinks he is prepared for the test.B: He is worried about the test.C: He doesn’t think he’s ready for the test.Answer: AExplanation: John says, “I’ve been studying hard for it. I think I’m prepared,”which means he believes he is ready for the test.12.M: Hi, Lily! Have you heard about the school trip next month?W: Yes, I have. We’re going to the countryside. It’s going to be so much fun! Q: Where is the school trip going to be?A: It’s going to be i n the city.B: It’s going to be in the countryside.C: It’s going to be at the beach.Answer: BExplanation: Lily answers, “We’re going to the countryside,” which indicates that the school trip is planned for the countryside.13.Listen to the dialogue and answer the question.W: Hi, John. How was your vacation in Beijing?M: It was great! I visited the Forbidden City and the Summer Palace. The scenery was beautiful, and the people were friendly.Question: What did John visit in Beijing?A) The Great WallB) The Forbidden City and the Summer PalaceC) Tiananmen SquareD) The Beijing ZooAnswer: B) The Forbidden City and the Summer PalaceExplanation: The question asks about the places John visited in Beijing.According to the dialogue, John visited the Forbidden City and the Summer Palace, so the correct answer is B) The Forbidden City and the Summer Palace.14.Listen to the passage and answer the question.The moon is Earth’s only natural satellite. It is about 384,400 kilometers away from Earth. The moon is about one-quarter the size of Earth and it takes about 27 days to complete one orbit around Earth.Question: How long does it take for the moon to complete one orbit around Earth?A) 24 hoursB) 27 daysC) 1 monthD) 365 daysAnswer: B) 27 daysExplanation: The question asks about the time it takes for the moon to complete one orbit around Earth. According to the passage, the moon takes about 27 days to complete one orbit around Earth, so the correct answer is B) 27 days.15.W: Hi, John. How was your science project?M: It was quite challenging, but I learned a lot about renewable energy sources.Q: What did John learn about in his science project?A: Renewable energy sources.B: Chemistry.C: Biology.D: Physics.Answer: AExplanation: The question asks what John learned about in his science project. In the dialogue, John mentions that he learned a lot about renewable energy sources, so the correct answer is A.16.M: Have you seen the new movie “Inception”? I heard it’s really amazing. W: Yes, I saw it last weekend. The story is so intriguing that I couldn’t stop thinking about it even after the movie ended.Q: What did the woman think about the movie “Inception”?A: It was boring.B. It was a waste of time.C. It was intriguing.D. It was predictable.Answer: CExplanation: The question asks what the woman thought about the movie “Inception”. In the dialogue, the woman says the story is so intriguing that she couldn’t stop thinking about it, which means she found it interesting and captivating. Therefore, the correct answer is C.17.You hear a conversation between two students, Alex and Sarah, about their weekend plans.A. Alex is going to visit his grandparents in the country.B. Sarah is planning to go hiking in the mountains.C. Both Alex and Sarah are going to a music festival.Answer: BExplanation: The conversation indicates that Sarah is excited about her hiking trip in the mountains, making option B the correct answer. Alex mentions that he will stay in town, implying that he has other plans.18.You hear a news report about a new eco-friendly initiative in your city.A. The city is implementing a new recycling program.B. The government is offering tax incentives for electric vehicle purchases.C. Local businesses are required to use solar energy.Answer: BExplanation: The news report specifically mentions the government’s tax incentives for electric vehicle purchases, which aligns with option B. The report does not mention a recycling program or the requirement for solar energy use, making options A and C incorrect.19.You are listening to a conversation between two students in a library.Student A: Hey, have you seen the new science book we need for our project? Student B: __________.A. Yes, i t’s right over there on the shelf.B. No, I haven’t, but I saw it on the list.C. I’ve read it, but I don’t think it’s available now.D. It’s not on the list, but I can help you find it.Answer: BExplanation: Student B responds that they haven’t seen the book but saw it on the list, indicating they are aware of the book but haven’t physically seen it in the library. The correct answer is B.20.You are listening to a radio announcement about a local event.Announcer: __________.A. The city park will host a free concert this weekend starting at 6 PM.B. All libraries will be closed next Monday for a staff training day.C. The local museum is offering free entry to students this month.D. The school sports day has been postponed due to the weather.Answer: AExplanation: The radio announcement is about a free concert happening at the city park this weekend. The correct answer is A. The other options refer to different events or announcements.二、阅读理解（30分）Reading ComprehensionPassage:In the small town of Willow Creek, there was a local library that had been a cornerstone of the community for over a century. The library was known for its quaint charm and the friendly atmosphere that made every visitor feel welcome. One of the most beloved features of the library was its old, wooden reading room where people could sit and enjoy a good book in peace.One sunny afternoon, a young girl named Emily entered the library for the first time. She was immediately drawn to the reading room, where she noticed an elderly woman sitting at a table, surrounded by stacks of books. Emily approached the woman, who was named Mrs. Thompson, and struck up a conversation.“Good afternoon, Mrs.Thompson,” Emily said with a smile. “I’ve never been in this room before. It’s so peaceful here.”Mrs. Thompson smiled warmly. “Yes, it is. This room has seen many generations of people come and go. I’ve been coming here since I was a child.”Emily was curious. “Do you have a favorite book from this room?”Mrs. Thompson paused for a moment, then re plied, “Oh, yes. It’s a book called ‘The Timeless Garden.’ It’s a story about a young girl who discovers a magical garden hidden behind her house. The book has taught me so much about life and friendship.”As Emily listened, she felt a sense of wonder. She knew she had to find this book and read it herself. She promised Mrs. Thompson she would return soon to discuss the story with her.Questions:1.What is the main feature of the reading room in the library?A. It has modern technology.B. It is surrounded by books.C. It is very quiet and peaceful.D. It is filled with children’s books.2.Who is the young girl that enters the library for the first time?A. Mrs. ThompsonB. The librarianC. EmilyD. The author3.What is the title of the book that Mrs. Thompson mentioned?A. ‘The Magical Library’B. ‘The Timeless Garden’C. ‘The Library’s Secret’D. ‘Emily’s Adventure’Answers:1.C2.C3.B三、完型填空（15分）Title: A Day in the Life of a TreeLast weekend, I went on a nature walk with my friends. It was a beautiful day, and we decided to go to the nearby forest to observe the plants and animals. While we were walking, one of our friends suggested that we should spend some time observing a single tree to understand how it lives through a day.The tree we chose was a big oak, its branches reaching out like open arms welcoming us. As we sat down at the base of the tree, we noticed that the leaves were rustling softly in the wind. The sun was shining brightly, and we could see how the tree was enjoying the warmth, as if it were drinking up the sunlight with every 1.After a while, we noticed tiny insects crawling up and down the trunk of the tree. They seemed to be collecting sap, which is the tree’s way of providing food for itself and its inhabitants. We realized that the tree is not just standing still; it’s very much alive and 2.As the day progressed, clouds started to gather in the sky, and soon it began to rain lightly. The raindrops fell gently onto the leaves and trickled down to the ground, soaking into the soil. This water would be absorbed by the roots and transported to all parts of the tree, helping it grow stronger and taller. The tree appeared to be drinking the rainwater greedily, as though it were 3 after a long period of drought.By late afternoon, the rain had stopped, and the sun came out again. The leaves glistened with water droplets that sparkled like little diamonds. Birds started to sing their evening songs from the branches, and the air was filled with a sense of peace and calm. Our friend remarked that just like the tree needs water and sunlight to live, we too need nourishment and warmth to grow and thrive. The tree serves as a reminder of the 4cycle of life and the importance of being connected to nature.As we got up to leave, we felt a deep sense of gratitude towards the tree for teaching us so much about itself and life in general. We left the forest feeling more connected to the natural world than ever before. The experience made us realize that even something seemingly static and silent as a tree hasa 5 story to tell.1.__________(A. leaf B. branch C. pore D. root)2.__________(A. dormant B. thriving C. stationary D. sleeping)3.__________(A. blooming B. wilting C. thirsting D. blossoming)4.__________(A. constant B. unchanging C. continuous D. ceaseless)5.__________(A. silent B. vivid C. motionless D. tranquil)Key:1.C. pore2.B. thriving3.C. thirsting4.C. continuous5.B. vividThis exercise aims to test the student s’ vocabulary knowledge, reading comprehension skills, and their ability to deduce contextually appropriate words based on the overall meaning of the passage.四、语法填空题（本大题有10小题，每小题1分，共10分）1、The students were asked to write a short story about their summervacation,_____________they had just experienced.A. whichB. whereC. whenD. what答案：C解析：此题考查定语从句的关系词。

修饰Sorption

ReviewRemoval of heavy metal ions from wastewater by chemicallymodiﬁed plant wastes as adsorbents:A reviewW.S.Wan Ngah *,M.A.K.M.HanaﬁahSchool of Chemical Sciences,Universiti Sains Malaysia,11800Penang,Malaysia Received 3April 2007;received in revised form 18June 2007;accepted 18June 2007Available online 27July 2007AbstractThe application of low-cost adsorbents obtained from plant wastes as a replacement for costly conventional methods of removing heavy metal ions from wastewater has been reviewed.It is well known that cellulosic waste materials can be obtained and employed as cheap adsorbents and their performance to remove heavy metal ions can be aﬀected upon chemical treatment.In general,chemically modiﬁed plant wastes exhibit higher adsorption capacities than unmodiﬁed forms.Numerous chemicals have been used for modiﬁcations which include mineral and organic acids,bases,oxidizing agent,organic compounds,etc.In this review,an extensive list of plant wastes as adsorbents including rice husks,spent grain,sawdust,sugarcane bagasse,fruit wastes,weeds and others has been compiled.Some of the treated adsorbents show good adsorption capacities for Cd,Cu,Pb,Zn and Ni.Ó2007Elsevier Ltd.All rights reserved.Keywords:Adsorption;Plant wastes;Low-cost adsorbents;Heavy metals;Wastewater treatment1.IntroductionHeavy metals have been excessively released into the environment due to rapid industrialization and have cre-ated a major global concern.Cadmium,zinc,copper,nickel,lead,mercury and chromium are often detected in industrial wastewaters,which originate from metal plating,mining activities,smelting,battery manufacture,tanneries,petroleum reﬁning,paint manufacture,pesticides,pigment manufacture,printing and photographic industries,etc.,(Kadirvelu et al.,2001a;Williams et al.,1998).Unlike organic wastes,heavy metals are non-biodegradable and they can be accumulated in living tissues,causing various diseases and disorders;therefore they must be removed before discharge.Research interest into the production of cheaper adsorbents to replace costly wastewater treatment methods such as chemical precipitation,ion-exchange,elec-troﬂotation,membrane separation,reverse osmosis,elec-trodialysis,solvent extraction,etc.(Namasivayam andRanganathan,1995)are attracting attention of scientists.Adsorption is one the physico-chemical treatment pro-cesses found to be eﬀective in removing heavy metals from aqueous solutions.According to Bailey et al.(1999),an adsorbent can be considered as cheap or low-cost if it is abundant in nature,requires little processing and is a by-product of waste material from waste industry.Plant wastes are inexpensive as they have no or very low eco-nomic value.Most of the adsorption studies have been focused on untreated plant wastes such as papaya wood (Saeed et al.,2005),maize leaf (Babarinde et al.,2006),teak leaf powder (King et al.,2006),lalang (Imperata cylindrica )leaf powder (Hanaﬁah et al.,2007),rubber (Hevea brasili-ensis )leaf powder (Hanaﬁah et al.,2006b,c ),Coriandrum sativum (Karunasagar et al.,2005),peanut hull pellets (Johnson et al.,2002),sago waste (Quek et al.,1998),salt-bush (Atriplex canescens )leaves (Sawalha et al.,2007a,b ),tree fern (Ho and Wang,2004;Ho et al.,2004;Ho,2003),rice husk ash and neem bark (Bhattacharya et al.,2006),grape stalk wastes (Villaescusa et al.,2004),etc.Some of the advantages of using plant wastes for wastewa-ter treatment include simple technique,requires little pro-0960-8524/$-see front matter Ó2007Elsevier Ltd.All rights reserved.doi:10.1016/j.biortech.2007.06.011*Corresponding author.Tel.:+6046533888;fax:+6046574854.E-mail address:wsaime@usm.my (W.S.Wan Ngah).Available online at Bioresource Technology 99(2008)3935–3948cessing,good adsorption capacity,selective adsorption of heavy metal ions,low cost,free availability and easy regen-eration.However,the application of untreated plant wastes as adsorbents can also bring several problems such as low adsorption capacity,high chemical oxygen demand(COD) and biological chemical demand(BOD)as well as total organic carbon(TOC)due to release of soluble organic compounds contained in the plant materials(Gaballah et al.,1997;Nakajima and Sakaguchi,1990).The increase of the COD,BOD and TOC can cause depletion of oxygen content in water and can threaten the aquatic life.There-fore,plant wastes need to be modiﬁed or treated before being applied for the decontamination of heavy metals. In this review,an extensive list of adsorbents obtained from plant wastes has been compiled and their methods of mod-iﬁcation were discussed.A comparison of adsorption eﬃ-ciency between chemically modiﬁed and unmodiﬁed adsorbents was also reported.2.Chemically modiﬁed plant wastesPretreatment of plant wastes can extract soluble organic compounds and enhance chelating eﬃciency(Gaballah et al.,1997).Pretreatment methods using diﬀerent kinds of modifying agents such as base solutions(sodium hydroxide,calcium hydroxide,sodium carbonate)mineral and organic acid solutions(hydrochloric acid,nitric acid, sulfuric acid,tartaric acid,citric acid,thioglycollic acid), organic compounds(ethylenediamine,formaldehyde,epi-chlorohydrin,methanol),oxidizing agent(hydrogen perox-ide),dye(Reactive Orange13),etc.for the purpose of removing soluble organic compounds,eliminating colour-ation of the aqueous solutions and increasing eﬃciency of metal adsorption have been performed by many research-ers(Hanaﬁah et al.,2006a;Reddy et al.,1997;Taty-Cos-todes et al.,2003;Gupta et al.,2003;Namasivayam and Kadirvelu,1997;Sˇc´iban et al.,2006a;Min et al.,2004; Kumar and Bandyopadhyay,2006;Baral et al.,2006;Acar and Eren,2006;Rehman et al.,2006;Abia et al.,2006; Shukla and Pai,2005a,Low et al.,1995;Azab and Peter-son,1989;Lazlo,1987;Wankasi et al.,2006).The types of chemicals used for modifying plant wastes and their maximum adsorption capacities are shown in Table1. 2.1.Rice husks/rice hullsRice husk consists of cellulose(32.24%),hemicellulose (21.34%),lignin(21.44%)and mineral ash(15.05%)(Rah-man et al.,1997)as well as high percentage of silica in its mineral ash,which is approximately96.34%(Rahman and Ismail,1993).Rice husk is insoluble in water,has good chemical stability,has high mechanical strength and pos-sesses a granular structure,making it a good adsorbent material for treating heavy metals from wastewater.The removal of heavy metals by rice husk has been extensively reviewed by Chuah et al.(2005).Among the heavy metal ions studied include Cd,Pb,Zn,Cu,Co,Ni and Au.Rice husk can be used to treat heavy metals in the form of either untreated or modiﬁed using diﬀerent modiﬁcation methods.Hydrochloric acid(Kumar and Bandyopadhyay, 2006),sodium hydroxide(Guo et al.,2003;Kumar and Bandyopadhyay,2006),sodium carbonate(Kumar and Bandyopadhyay,2006),epichlorohydrin(Kumar and Ban-dyopadhyay,2006),and tartaric acid(Wong et al.,2003a; Wong et al.,2003b)are commonly used in the chemical treatment of rice husk.Pretreatment of rice husks can remove lignin,hemicellulose,reduce cellulose crystallinity and increase the porosity or surface area.In general,chem-ically modiﬁed or treated rice husk exhibited higher adsorption capacities on heavy metal ions than unmodiﬁed rice husk.For example,Kumar and Bandyopadhyay (2006)reported that rice husk treated with sodium hydrox-ide,sodium carbonate and epichlorohydrin enhanced the adsorption capacity of cadmium.The base treatment using NaOH for instance appeared to remove base soluble mate-rials on the rice husk surface that might interfere with its adsorption property.Tarley et al.(2004)found that adsorption of Cd increase by almost double when rice husk was treated with NaOH.The reported adsorption capaci-ties of Cd were7and4mg gÀ1for NaOH treated and unmodiﬁed rice husk,respectively.Meanwhile,most of the acids used for treatment of plant wastes were in dilute form such as sulfuric acid, hydrochloric acid and nitric acid.According to Esteghla-lian et al.(1997),dilute acid pretreatment using sulfuric acid can achieve high reaction rates and improve cellulose hydrolysis.Concentrated acids are powerful agents for cel-lulose hydrolysis but they are toxic,corrosive and must be recovered(Sivers and Zacchi,1995).However,in some cases,hydrochloric acid treated rice husk showed lower adsorption capacity of cadmium than the untreated rice husk(Kumar and Bandyopadhyay,2006).When rice husk is treated with hydrochloric acid,adsorption sites on the surface of rice husk will be protonated,leaving the heavy metal ions in the aqueous phase rather than being adsorbed on the adsorbent surface.Wong et al.(2003a)carried out an adsorption study of copper and lead on modiﬁed rice husk by various kinds of carboxylic acids(citric acid,sali-cylic acid,tartaric acid,oxalic acid,mandelic acid,malic and nitrilotriacetic acid)and it was reported that the high-est adsorption capacity was achieved by tartaric acid mod-iﬁed rice husk.Esteriﬁed tartaric acid modiﬁed rice husk however signiﬁcantly reduced the uptake of Cu and Pb. The maximum adsorption capacities for Pb and Cu were reported as108and29mg gÀ1,respectively.Eﬀect of che-lators on the uptake of Pb by tartaric acid modiﬁed rice husk was also studied.It was reported that higher molar ratios of chelators such as nitrilotriacetic acid(NTA)and ethylenediamine tetraacetic acid(EDTA)caused signiﬁcant suppressing eﬀect on the uptake of Pb.Dyestuﬀtreated rice hulls using Procion red and Procion yellow for the removal of Cr(VI),Ni(II),Cu(II),Zn(II),Cd(II),Hg(II)and Pb(II) were studied by Suemitsu et al.(1986).More than80%of3936W.S.Wan Ngah,M.A.K.M.Hanaﬁah/Bioresource Technology99(2008)3935–3948W.S.Wan Ngah,M.A.K.M.Hanaﬁah/Bioresource Technology99(2008)3935–39483937 Table1Summary of modiﬁed plant wastes as adsorbents for the removal of heavy metal ions from aqueous solutionAdsorbent Modifying agent(s)Heavy metal Q max(mg gÀ1)SourceRice husk Water washed Cd(II)8.58Kumar and Bandyopadhyay(2006) Sodium hydroxide20.24Sodium bicarbonate16.18Epichlorohydrin11.12Rice husk Tartaric acid Cu(II)31.85Wong et al.(2003b)Pb(II)120.48Sawdust(cedrus deodar wood)Sodium hydroxide Cd(II)73.62Memon et al.(2007)Sawdust(S.robusta)Formaldehyde Cr(VI) 3.6Baral et al.(2006)Sawdust(Poplar tree)Sulfuric acid Cu(II)13.95Acar and Eren(2006)Sawdust(Dalbergia sissoo)Sodium hydroxide Ni(II)10.47Rehman et al.(2006)Sawdust(Poplar tree)Sodium hydroxide Cu(II) 6.92Sˇc´iban et al.(2006a)Zn(II)15.8Sawdust(Fir tree)Cu(II)12.7Zn(II)13.4Sawdust(Oak tree)Hydrochloric acid Cu(II) 3.60Argun et al.(2007)Ni(II) 3.37Cr(VI) 1.74Sawdust(Pinus sylvestris)Formaldehyde in Sulfuric acid Pb(II)9.78Taty-Costodes et al.(2003)Cd(II)9.29Walnut sawdust Formaldehyde in sulfuric acid Cd(II) 4.51Bulut and Tez(2003)Ni(II) 6.43Pb(II) 4.48Sawdust Reactive Orange13Cu(II)8.07Shukla and Pai(2005b)Ni(II)9.87Zn(II)17.09Peanut husk Sulfuric acid Pb(II)29.14Li et al.(2006a)Cr(III)7.67Cu(II)10.15Cr(VI)11.4Dubey and Gopal(2006) Groundnut husk Sulfuric acid followed by silverimpregnationCassava waste Thioglycollic acid Cd(II)NA Abia et al.(2006)Cassava tuber bark waste Thioglycollic acid Cd(II)26.3Horsfall Jr.et al.(2006)Cu(II)90.9Zn(II)83.3Wheat bran Sulfuric acid Cu(II)51.5O¨zer et al.(2004)Wheat bran Sulfuric acid Cd(II)101O¨zer and Pirinc¸c¸i(2006)Juniperﬁbre Sodium hydroxide Cd(II)29.54Min et al.(2004)Indian barks Hydrochloric acid Cu(II)Reddy et al.(1997)–sal51.4–mango42.6–jackfruit17.4Juteﬁbres Reactive Orange13Cu(II)8.40Shukla and Pai(2005a)Ni(II) 5.26Zn(II) 5.95Hydrogen peroxide Cu(II)7.73Ni(II) 5.57Zn(II)8.02Unmodiﬁed Cu(II) 4.23Ni(II) 3.37Zn(II) 3.55Banana pith Nitric acid Cu(II)13.46Low et al.(1995)Banana stem Formaldehyde Pb(II)91.74Noeline et al.(2005)Spent grain Hydrochloric acid Cd(II)17.3Low et al.(2000)Sodium hydroxide Pb(II)35.5(continued on next page)Cd(II),Pb(II)and Hg(II)ions were able to be removed by the two types of treated adsorbents,while Cr(VI)recorded the lowest percentage removal(<40%).2.2.Spent grainSpent grain obtained from brewery can be used to treat Pb(II)and Cd(II)ions as demonstrated by Low et al.,2000.Treatment of spent grain with NaOH greatly enhanced adsorption of Cd(II)and Pb(II)ions,whereas HCl treated spent grain showed lower adsorption than the untreated spent grain.The increase in adsorption of heavy metal ions after base treatment could be explained by the increase in the amount of galactouronic acid groups after hydrolysis of O-methyl ester groups.The best pH range for metal adsorption was4–6.Kinetic study reveals that the equilib-Table1(continued)Adsorbent Modifying agent(s)Heavy metal Q max(mg gÀ1)SourceCork powder Calcium chloride Cu(II)15.6Chubar et al.(2004)Sodium chloride19.5Sodium hydroxide18.8Sodium hypochlorite18.0Sodium iodate19.0Corncorb Nitric acid Cd(II)19.3Leyva-Ramos et al.(2005)Citric acid55.2Imperata cylindrica leaf powder Sodium hydroxide Pb(II)13.50Hanaﬁah et al.(2006a) Alfalfa biomass Sodium hydroxide Pb(II)89.2Tiemann et al.(2002)Azollaﬁliculoides (aquatic fern)Hydrogen peroxide–MagnesiumchloridePb(II)228Ganji et al.(2005)Cd(II)86Cu(II)62Zn(II)48Carrot residues Hydrochloric acid Cr(III)45.09Nasernejad et al.(2005)Cu(II)32.74Zn(II)29.61Sugarcane bagasse Sodium bicarbonate Cu(II)114Junior et al.(2006)Pb(II)196Cd(II)189Ethylenediamine Cu(II)139Pb(II)164Cd(II)189Triethylenetetramine Cu(II)133Pb(II)313Cd(II)313Sugarbeet pulp Hydrochloric acid Cu(II)0.15Pehlivan et al.(2006)Zn(II)0.18Bagasseﬂy ash Hydrogen peroxide Pb(II) 2.50Gupta and Ali(2004)Cr(III) 4.35Nipah palm shoot biomass Mercaptoacetic acid Pb(II)52.86Wankasi et al.(2006)Cu(II)66.71Groundnut shells Reactive Orange13Cu(II)7.60Shukla and Pai(2005b)Ni(II)7.49Zn(II)9.57Terminalia arjuna nuts ZnCl2Cr(VI)28.43Mohanty et al.(2005)Coirpith ZnCl2Cr(VI)NA Namasivayam and Sangeetha(2006)Ni(II)Hg(II)Cd(II)Kula et al.(2007)Sulfuric acid and ammonium persulphate Hg(II)154Namasivayam and Kadirvelu(1999) Cu(II)39.7Namasivayam and Kadirvelu(1997) Hg(II)NA Kadirvelu et al.(2001a)Pb(II)Cd(II)Ni(II)Cu(II)Ni(II)62.5Kadirvelu et al.(2001b)NA–not available.3938W.S.Wan Ngah,M.A.K.M.Hanaﬁah/Bioresource Technology99(2008)3935–3948rium time of adsorption was120min for both metal ions and adsorption followed pseudo-second-order model.The maximum adsorption capacity for lead was two times higher than cadmium.The eﬀect of organic ligands (EDTA,nitrilotriacetic acid and salicylic acid)on adsorp-tion eﬃciency was assessed and adsorption was greatly reduced by EDTA and nitrilotriacetic acid at molar ratio of1:1(metal:ligand).EDTA and nitrilotriacetic acid could chelate the heavy metal ions,therefore more metal ions would remain in the solutions rather than being adsorbed (Jeon and Park,2005).Salicylic acid on the other hand slightly reduced the percentage of cadmium adsorption but did not aﬀect adsorption of lead.2.3.Sugarcane bagasse/ﬂy ashJunior et al.(2006)reported the use of succinic anhy-dride modiﬁed sugarcane bagasse for treatment of Cu, Cd and Pb from aqueous solutions.Sugarcane bagasse consists of cellulose(50%),polyoses(27%)and lignin (23%).The presence of these three biological polymers causes sugarcane bagasse rich in hydroxyl and phenolic groups and these groups can be modiﬁed chemically to pro-duce adsorbent materials with new properties.The authors reported that the hydroxyl groups in sugarcane bagasse could be converted to carboxylic groups by using succinic anhydride.The carboxylic groups were later reacted with three diﬀerent chemicals mainly NaHCO3,ethylenediamine and triethylenetetramine to produce new properties of adsorbent materials which showed diﬀerent adsorption capacities for metal ions.It was found that sugarcane bagasse treated with ethylenediamine and triethylenetetra-mine shows a remarkable increase in nitrogen content com-pared to untreated sample,and triethylenetetramine modiﬁed sugarcane bagasse has a higher increasing extent. The presence of amide group was also detected in ethylene-diamine and triethylenetetramine modiﬁed sugarcane bag-asses as a result of the reaction between–COOH and–NH2groups.Kinetic studies showed that equilibrium time for adsorption of Cu,Cd and Pb onto tethylenediamine and triethylenetetramine modiﬁed sugarcane bagasses were slower than that for adsorbent modiﬁed with NaHCO3. Triethylenetetramine modiﬁed sugarcane bagasse was the best adsorbent material for removal of Cd and Pb since the adsorption capacities for both metals are two times higher than unmodiﬁed sugarcane bagasse.This was prob-ably caused by the higher number of nucleophilic sites introduced in triethylenetetramine modiﬁed sugarcane bagasse.When sugarcane bagasse was modiﬁed with meth-anol,however,the resulting adsorbent did not show a good uptake of cadmium as the maximum adsorption capacity was6.79mg gÀ1(Ibrahim et al.,2006).The performance of hydrogen peroxide treated bagasse ﬂy ash,a solid waste of sugar industry for removal of lead and chromium was explored by Gupta and Ali(2004). Hydrogen peroxide is a good oxidizing agent and used to remove the adhering organic matter on the adsorbent.It was found that hydrogen peroxide treated bagasseﬂy ash was able to remove chromium in a shorter period of time (60min)compared to lead(80min).The isotherm study also revealed maximum adsorption capacity for chromium was higher than lead.However,the recorded values of maximum adsorption capacities for both metals were low (2.50and4.35mg gÀ1for Pb and Cr,respectively).The detail mechanism of adsorption by the treated bagasseﬂy ash was not discussed,but it was thought that adsorption was controlled byﬁlm diﬀusion at lower metal concentra-tion and particle diﬀusion at higher concentration of metal ions.2.4.SawdustSawdust,obtained from wood industry is an abundant by-product which is easily available in the countryside at negligible price.It contains various organic compounds (lignin,cellulose and hemicellulose)with polyphenolic groups that could bind heavy metal ions through diﬀerent mechanisms.An experiment on the eﬃciency of sawdust in the removal of Cu2+and Zn2+ions was conducted by Sˇc´i-ban et al.(2006a).Two kinds of sawdust,poplar andﬁr wood were treated with NaOH(ﬁbre-swelling agent)and Na2CO3solutions and the adsorption capacities were com-pared with the untreated sawdusts.For unmodiﬁed saw-dust,both types of woods showed higher uptakes of Cu2+ions than Zn2+ions,and adsorption followed Lang-muir isotherm model.Equivalent amounts of adsorption capacities were recorded by both types of sawdust for Zn2+and Cu2+ions,although these two adsorbents have diﬀerent anatomical structure and chemical composition. After treating with NaOH,a marked increase in adsorption capacity was observed for both heavy metal ions,especially for Zn2+ions(2.5times for Cu2+and15times for Zn2+). The adsorption capacities shown by Langmuir model were 6.92mg gÀ1(poplar sawdust)and12.70mg gÀ1(ﬁr saw-dust)for Cu2+,and15.83mg gÀ1(poplar sawdust)and 13.41mg gÀ1for Zn2+(ﬁr sawdust),respectively.In another experiment,Sˇc´iban et al.(2006b)found that the leaching of coloured organic matters during the adsorption can be eliminated by pretreatments with formaldehyde in acidic medium,with sodium hydroxide solution after form-aldehyde treatment,or with sodium hydroxide only. According to Sˇc´iban et al.(2006a),NaOH improved the adsorption process by causing the liberation of new adsorption sites on the sawdust surface.An increase in the concentration of NaOH for modiﬁcation purpose how-ever did not cause a signiﬁcant increase of the adsorption capacity.The authors suggest that no greater than1%of concentration of NaOH solution should be used for mod-iﬁcation.The temperature of modiﬁcation was also not a signiﬁcant factor for the main increase of adsorption capacities of modiﬁed sawdusts.It was observed that only a slight increase in Cu2+and Zn2+adsorption occurred when theﬁr sawdust was treated with NaOH at higher tem-perature(80°C).The study on adsorption capacity byW.S.Wan Ngah,M.A.K.M.Hanaﬁah/Bioresource Technology99(2008)3935–39483939treatment with Na2CO3revealed the modiﬁed sawdusts had two times higher adsorption for Cu2+ions and six times higher for Zn2+ions compared to unmodiﬁed saw-dusts.The application of Na2CO3for chemical modiﬁca-tion is less eﬃcient than the use of NaOH.This is due to higher number of Na+ions in1g of NaOH compared to 1g of Na2CO3.In general,three possible reasons for the increase in adsorption capacities of heavy metal ions were given by the authors:(i)Changes on wood surface-increase in surface area,average pore volume and pore diameter after alkaline treatment.The surface area and average pore diame-ter increased about1.5–2times after modiﬁcation. (ii)Improvement in ion-exchange process especially with Na+ions.(iii)Microprecipitation of metal hydroxides–Cu(OH)2 and Zn(OH)2in the pores of sawdust.Although the work on adsorption of copper and zinc ions onto sawdust of poplar tree was reported by Sˇc´iban et al.(2006a),they did not carry out a detail experiment on the kinetic of adsorption.The eﬀect of sulfuric acid treatment on sawdust of pop-lar tree was studied by Acar and Eren(2006).Sulfuric acid poplar sawdust possessed good removal of92.4%Cu2+at pH5,while untreated sawdust could only removed47%. The kinetic of copper binding indicated that it is a rapid process and about70–80%of copper ions removed from the solution in10min.The percent of copper removal how-ever decreases as the metal concentration increases.The increase in percent of adsorption with adsorbent dose could be due to the increase in surface area and availability of more active sites.The treated poplar sawdust showed maximum adsorption capacity of13.945mg gÀ1against 5.432mg gÀ1for untreated sawdust which followed Lang-muir isotherm model.The maximum adsorption capacity for sulfuric acid treated poplar sawdust is higher than to the value recorded by NaOH treated poplar sawdust reported by Sˇc´iban et al.(2006a).Concentrated sulfuric acid was also used to modify coconut tree sawdust for removing mercury and nickel(Kadirvelu et al.,2003).It was reported that100%removal of mercury was achieved compared to81%for nickel and adsorption occurred in 1h.Rehman et al.(2006)reported the removal of Ni2+ions by using sodium hydroxide treated sawdust of Dalbergia sissoo,a byproduct of sawmills.The treatment of sawdust with NaOH results in the conversion of methyl esters which are the major constituents in cellulose,hemicellulose and lignin to carboxylate ligands.The adsorption time study revealed that nickel ions were removed fast in theﬁrst 20min due to extra-cellular binding.The maximum adsorp-tion capacity of Ni2+ions was found to be10.47mg gÀ1at 50°C.Adsorption was more favourable at higher tempera-ture and adsorption followed both Langmuir and Freund-lich isotherm models.A comparative study on the adsorption eﬃciency of untreated and NaOH treated sawdust of cedrus deodar wood was conducted by Memon et al.(2007).They reported that cedrus deodar sawdust mainly consists of acid detergentﬁbre(cellulose and lignin),hydroxyl groups (tannins)and phenolic compounds.The acidimetric–alkali-metric titration study revealed that sawdust has four major groups responsible for cadmium binding which were car-boxylic,phosphoric,amines and phenolic.Cadmium removal was more favoured by NaOH treated sawdust as the value of adsorption capacity was four times greater than untreated sawdust.Maximum removal of cadmium occurred at pH above4for both types of adsorbents.When the pH of the solution is greater than4,carboxylic groups will be deprotonated and the adsorbent surface will be neg-atively charged resulting in higher adsorption of cadmium. However;at pH less than3,carboxylic groups become pro-tonated and adsorption sites are unable to attract Cd2+ ions.NaOH treated sawdust also shows good settling prop-erty,making it easy toﬁlter or separate the adsorbent from the solution.Ion-exchange was considered as the predom-inant mechanism of cadmium adsorption as the values of adsorption energy(E)determined from Dubinin–Radushk-evic plots are in the range of9–16kJ molÀ1.Maximum adsorption capacity recorded at temperature of20°C was73.62mg gÀ1.A detail analysis on the ideal concentration of NaOH for modifying juniperﬁbre for adsorption of cadmium ions was carried out by Min et al.(2004).Sodium hydroxide treatment of lignocellulosic materials can cause swelling which leads to an increase in internal surface area,a decrease in the degree of polymerization,a decrease in crys-tallinity,separation of structural linkages between lignin and carbohydrates and disruption of the lignin structure. Sodium hydroxide is a good reagent for saponiﬁcation or the conversion of an ester group to carboxylate and alco-hol,as shown in the equation below:RCOOR0þH2O!OHÀRCOOÀþR0OHð1ÞBased on the FTIR analysis,it was found that as the con-centration of NaOH increases(from0to 1.0M),the amount of carboxylate was also increased.A maximum concentration of0.5M of NaOH was suitable to carry out saponiﬁcation process.After base treatment,the max-imum adsorption capacity of cadmium increased by about three times(from9.18to29.54mg gÀ1)compared to un-treated juniperﬁbre despite a decrease in speciﬁc surface area for the treated adsorbent.Data obtained from pseu-do-second-order kinetic study also revealed that base trea-ted juniperﬁbre had higher values of adsorption capacity, q e(mg gÀ1)and initial adsorption rate constant,h (mg gÀ1minÀ1)when compared to untreated adsorbent.Hexavalent chromium adsorption by formaldehyde treated sawdust was studied by Baral et al.,2006.Formal-dehyde is a common compound used to immobilize colour and water soluble compounds from sawdust(Garg et al.,3940W.S.Wan Ngah,M.A.K.M.Hanaﬁah/Bioresource Technology99(2008)3935–39482004).The adsorption capacity of Cr(VI)determined from Langmuir isotherm was low(3.60mg gÀ1)and equilibrium adsorption time took about5h.Adsorption process was strongly aﬀected by several physico-chemical parameters such as pH,adsorbent dose,temperature and initial con-centration of chromium solution.Maximum adsorption occurred at pH range3–6and reduced signiﬁcantly beyond pH6.The percentage adsorption of Cr(VI)increased with increase in adsorbent dose,but decreased with increase in metal concentration and temperature.Adsorption rate tends to increase with increase in adsorbent dose due to higher number of available adsorption sites.As concentra-tion of Cr(VI)increases withﬁxed amount of adsorbent dose,more Cr(VI)ions will remain in the aqueous phase, thus percentage adsorption will be small.The decrease in adsorption rate with increase in temperature indicates exo-thermic nature of adsorption,in which adsorption is more favourable at lower temperatures.According to Taty-Costodes et al.(2003),treatment with formaldehyde induces a stabilization of the hydrosol-uble compounds of adsorbent by creating covalent bonds on the constitutive units.This could eliminate the problem associated with the release of polyphenolic compounds which could cause an increase in COD in wastewater.A research on the adsorption of Pb(II)and Cd(II)onto form-aldehyde treated sawdust of Pinus sylvestris shows that the two metal ions were successfully removed in less than 20min at low concentrations(<10mg lÀ1).It was reported that metal ions could form complexes with the oxygen atom on carbonyl and hydroxyl groups(acting as a Lewis base).The maximum adsorption capacities of Pb(II)and Cd(II)were9.78and9.29mg gÀ1,respectively.Adsorption kinetic indicates that pseudo-second-order model was bet-terﬁtted than pseudo-ﬁrst-order and intraparticle diﬀusion is one of the rate determining steps.Nickel,cadmium and lead adsorption by walnut sawdust treated with formalde-hyde in sulfuric acid was studied and it was found that adsorption is dependent on contact time,metal concentra-tion and temperature(Bulut and Tez,2003).Equilibrium time was established in about60min for all heavy metals. The kinetic study reveals that adsorption followed pseudo-second-order model better than pseudo-ﬁrst-order.The maximum adsorption capacities were 6.43, 4.51and 4.48mg gÀ1for Ni,Cd and Pb,respectively.Based on tem-perature study,adsorption was favaourable at higher tem-peratures as the values of D G°become more negative.Chubar et al.(2004)studied the performance of various kinds of chemically treated cork powder obtained from cork oak tree for the removal of Cu,Zn and Ni.Treatment of cork powder with salts such as NaCl and CaCl2causes the conversion of active binding sites from the H+form to Na+and Ca2+form.The salt modiﬁed cork powder shows greater adsorption capacity than the unmodiﬁed cork especially at higher heavy metal concentrations.It was also noted that the Na+form cork recorded a higher adsorption capacity value than the Ca2+form.This obser-vation can be explained in terms of the diﬀerent charge of cations whereby the interaction of cork powder binding sites with divalent calcium ions is stronger than the mono-valent sodium ions.Hence,the biosorption reaction of cop-per will be hindered.Treatment of cork powder with an alkaline solution(NaOH)at high temperature increased the sorption capacity toward heavy metals by about33%.A high concentration of NaOH however causes a decrease in copper removal due to the destruction of the biomass. Besides NaCl,CaCl2and NaOH,modiﬁcation of cork powder could be carried out using commercial laundry detergent and the amount of copper removed was found to increase,probably due to the exposure of new binding sites.The use of NaClO and NaIO3will increase the num-ber of active binding sites by oxidation of the some of func-tional groups of cork to carboxylic groups,hence more copper ions could be sorbed.An increase of70–80%in cork capacity for copper was achieved after treating cork powder with NaClO containing7%of active chlorine. 2.5.Wheat branWheat bran,a by-product of wheat milling industries proved to be a good adsorbent for removal of many types of heavy metal ions such as Pb(II),Cu(II)and Cd(II).The application of a strong dehydrating agent like sulfuric acid (H2SO4)can have a signiﬁcant eﬀect on the surface area of the adsorbent,which eventually results in better eﬃciency of adsorption of copper ions as reported by O¨zer et al. (2004).It was found that upon treatment with sulfuric acid, wheat bran had a much higher surface area.The authors suggested that acid treatment caused changes in surface area by increasing the conversion of macropores to microp-ores.Maximum adsorption capacity for Cu(II)ions was reported as51.5mg gÀ1(at pH5)and equilibrium time of adsorption was achieved in30min.O¨zer and Pirinc¸c¸i (2006)conducted a study on the removal of lead ions by sulfuric acid treated wheat bran.It was reported that max-imum lead removal(82.8%)occurred at pH6after2h of contact time.Three isotherm models were analyzed for determining the maximum adsorption capacity of wheat bran particularly Langmuir,Freundlich and Redlich-Peter-son.Based on the non-linear plots,it was found that adsorptionﬁtted well to the Redlich-Peterson than Lang-muir and Freundlich models.The Langmuir plots indicate that maximum adsorption capacities increased with an increase in temperature(79.37mg gÀ1at60°C and 55.56mg gÀ1at25°C).The decrease in the values of D G°suggests that adsorption was more favourable at higher temperatures and adsorption was endothermic in nature. The kinetic study showed that lead adsorption could be described well with n th-order kinetic model.O¨zer(2006) also examined the sulfuric acid treated wheat bran for cad-mium ion removal from aqueous solution.After4h of con-tact time,the maximum adsorption capacity that could be achieved for cadmium was101mg gÀ1at pH5.Therefore, in general the order of maximum removal of the above three metals follows:Cd(II)>Pb(II)>Cu(II).W.S.Wan Ngah,M.A.K.M.Hanaﬁah/Bioresource Technology99(2008)3935–39483941。

Absorption And Distribution Of Toxicants

The amphipathic (两性分子) nature of the membrane produces a barrier for ionized, highly polar compounds although not an absolute barrier.
The importance of nonionic, lipid-soluble characteristics of a xenobiotic is discussed in the following sections.
In addition, toxicants may be metabolized, either activated or detoxified, by the target tissue itself (如肝肺).
7
In summary
8
2.2 Membranes (生物膜)
Toxicants must pass through a number of barriers during entry into the body as well as when entering tissues, cells, and cellular compartments. Similar passages occur also when toxicants or metabolites are excreted from the body.
For example, alkaloids (生物碱), such as strychnine（士的宁）, that are ionized as a result of introduction into the strongly acid stomach do not show toxic effects. However, when such alkaloids are allowed to pass to the more alkaline intestine, where they became nonionized, toxicity becomes apparent because the toxic alkaloid is more easily absorbed.

基于反奖赏系统探究药物成瘾的神经调控机制

基于反奖赏系统探究药物成瘾的神经调控机制*邓雨钧，庆宏，全贞贞△（北京理工大学生命学院，北京 100081）Neural mechanism of drug addiction based on anti -reward systemDENG Yujun ， QING Hong ， QUAN Zhenzhen △（School of Life Science ， Beijing Institute of Technology ， Beijing 100081， China. E -mail ： qzzbit 2015@ ）［ABSTRACT ］ Drug addiction is a type of chronic recurrent brain disease with extremely complicated pathogene⁃sis ， which is often manifested as spontaneous and compulsive drug seeking and using behavior. The anti -reward system plays an extremely important role in the occurrence and development of drug addiction -related symptoms. This article pro⁃vides a brief overview of the formation process ， symptom representation ， neural mechanism and motivational/behavioralchanges of drug addiction and their adversarial process theory ， as well as the anatomical structure of the anti -reward sys⁃tem and evidence for its involvement in regulating the occurrence and development of drug addiction. This work helps bet⁃ter understand the neural mechanism of drug addiction through the view of anti -reward system and provides insights for thetreatment of related diseases and drug abuse.［关键词］药物成瘾；反奖赏系统；泛杏仁核；缰核［KEY WORDS ］ drug addiction ； anti -reward system ； extended amygdala ； habenula［中图分类号］ R338.2； R742； R363.2 ［文献标志码］ Adoi ： 10.3969/j.issn.1000-4718.2023.07.018药物成瘾是一类由大脑相关结构改变引起的，发病机制极为复杂的慢性、易复发性脑疾病，常表现为自发地、强迫性地寻求并使用药物，无法控制药物的使用量［1］，以及在不能满足药物需求时出现负面情绪［2］。

有机磷杀虫剂药理学

22
1、乙酰胆碱酯酶及其功能

It is critical to note that most studies of the neuromuscular junction in insects have shown clearly that there is no cholinesterase there and that transmission at the synapse does not involve acetylcholine. It probably involve glutamate instead.
12
三、有机磷杀虫剂的中毒

2、Symptoms of organophosphorus poisoning in mammals (1) defecation(通便), urination, (2)muscular twitching, and muscular weakness (3) prostration (4) clonic, convulsions
8
二、有机磷杀虫剂的主要品种

2、Trichlorfon (敌百虫) A white to pale yellow crystalline powder Soluble in water, alcohols, and ketones Dehydrochlorinated in mild alkali to form DDVP Control of endo- and ectoparasites of livestock
23
1、乙酰胆碱酯酶及其功能

AChE isozymes differed measurable in their sensitivity to inhibition by anticholinesterase in vitro.

文外翻译原文

ReviewAgricultural waste material as potential adsorbent for sequesteringheavy metal ions from aqueous solutions –A reviewDhiraj Sud *,Garima Mahajan,M.P.KaurSant Longowal Institute of Engineering and Technology,Department of Chemistry,Longowal 148106,India Received 15October 2007;received in revised form 22November 2007;accepted 22November 2007Available online 14February 2008AbstractHeavy metal remediation of aqueous streams is of special concern due to recalcitrant and persistency of heavy metals in environment.Conventional treatment technologies for the removal of these toxic heavy metals are not economical and further generate huge quantity of toxic chemical sludge.Biosorption is emerging as a potential alternative to the existing conventional technologies for the removal and/or recovery of metal ions from aqueous solutions.The major advantages of biosorption over conventional treatment methods include:low cost,high eﬃciency,minimization of chemical or biological sludge,regeneration of biosorbents and possibility of metal recovery.Cellulosic agricultural waste materials are an abundant source for signiﬁcant metal biosorption.The functional groups present in agri-cultural waste biomass viz.acetamido,alcoholic,carbonyl,phenolic,amido,amino,sulphydryl groups etc.have aﬃnity for heavy metal ions to form metal complexes or chelates.The mechanism of biosorption process includes chemisorption,complexation,adsorption on surface,diﬀusion through pores and ion exchange etc.The purpose of this review article is to provide the scattered available information on various aspects of utilization of the agricultural waste materials for heavy metal removal.Agricultural waste material being highly eﬃcient,low cost and renewable source of biomass can be exploited for heavy metal remediation.Further these biosorbents can be mod-iﬁed for better eﬃciency and multiple reuses to enhance their applicability at industrial scale.Ó2007Elsevier Ltd.All rights reserved.Keywords:Agricultural wastes;Biosorption;Industrial eﬄuents;Heavy metal remediation;Adsorbent1.IntroductionToxic heavy metal ions get introduced to the aquatic streams by means of various industrial activities viz.min-ing,reﬁning ores,fertilizer industries,tanneries,batteries,paper industries,pesticides etc.and posses a serious threat to environment (Celik and Demirbas,2005;Friedman and Waiss,1972;Kjellstrom et al.,1977;Pastircakova,2004).The major toxic metal ions hazardous to humans as well as other forms of life are Cr,Fe,Se,V,Cu,Co,Ni,Cd,Hg,As,Pb,Zn etc.These heavy metals are of speciﬁc con-cern due to their toxicity,bio-accumulation tendency and persistency in nature (Friberg and Elinder,1985;Garget al.,2007;Randall et al.,1974).Several past disasters due to the contamination of heavy metals in aquatic streams are Minamata tragedy in Japan due to methyl mer-cury contamination and ‘‘Itai-Itai ”due to contamination of cadmium in Jintsu river of japan (Friberg and Elinder,1985;Kjellstrom et al.,1977).Various regulatory bodies have set the maximum prescribed limits for the discharge of toxic heavy metals in the aquatic systems.However the metal ions are being added to the water stream at a much higher concentration than the prescribed limits by industrial activities,thus leading to the health hazards and environmental degradation (Table 1).Conventional methods for removal of metal ions from aqueous solutions include chemical precipitation,ion exchangers,chemical oxidation/reduction,reverse osmosis,electro dialysis,ultra ﬁltration etc (Gardea-Torresdey et al.,1998;Patterson,1985;Zhang et al.,1998).However these0960-8524/$-see front matter Ó2007Elsevier Ltd.All rights reserved.doi:10.1016/j.biortech.2007.11.064*Corresponding author.Tel.:+911672284698;fax:+911672284840.E-mail address:suddhiraj@ (D.Sud).Available online at Bioresource Technology 99(2008)6017–6027conventional techniques have their own inherent limita-tions such as less eﬃciency,sensitive operating conditions, production of secondary sludge and further the disposal is a costly aﬀair(Ahluwalia and Goyal,2005a).Another powerful technology is adsorption of heavy metals by acti-vated carbon for treating domestic and industrial waste water.(Horikoshi et al.,1981;Hosea et al.,1986).However the high cost of activated carbon and its loss during the regeneration restricts its application.Since1990’s the adsorption of heavy metal ions by low cost renewable organic materials has gained momentum(Bailey et al., 1999;Orhan and Bujukgungor,1993;Rao and Parwate, 2002;Vieira and Volesky,2000).The utilization of sea-weeds,moulds,yeasts,and other dead microbial biomass and agricultural waste materials for removal of heavy met-als has been explored(Bailey et al.,1999;Haung and Haung,1996;Sudha and Abraham,2003;Zhou and Kiﬀ, 1991).Recently attention has been diverted towards the biomaterials which are byproducts or the wastes from large scale industrial operations and agricultural waste materials. The major advantages of biosorption over conventional treatment methods include:low cost,high eﬃciency,mini-mization of chemical or biological sludge,no additional nutrient requirement,and regeneration of biosorbents and possibility of metal recovery.Agricultural materials particularly those containing cel-lulose shows potential metal biosorption capacity.The basic components of the agricultural waste materials bio-mass include hemicellulose,lignin,extractives,lipids, proteins,simple sugars,water hydrocarbons,starch con-taining variety of functional groups that facilitates metal complexation which helps for the sequestering of heavy metals(Bailey et al.,1999;Hashem et al.,2005a,b,2007). Agricultural waste materials being economic and eco-friendly due to their unique chemical composition,avail-ability in abundance,renewable,low in cost and more eﬃcient are seem to be viable option for heavy metal reme-diation.Studies reveal that various agricultural waste materials such as rice bran,rice husk,wheat bran,wheat husk,saw dust of various plants,bark of the trees,ground-nut shells,coconut shells,black gram husk,hazelnut shells, walnut shells,cotton seed hulls,waste tea leaves,Cassiaﬁs-tula leaves,maize corn cob,jatropa deoiled cakes,sugar-cane bagasse,apple,banana,orange peels,soybean hulls, grapes stalks,water hyacinth,sugar beet pulp,sunﬂower stalks,coﬀee beans,arjun nuts,cotton stalks etc has been tried(Annadurai et al.,2002;Cimino et al.,2000;Hashem et al.,2006a,b;Macchi et al.,1986;Maranon and Sastre, 1991;Mohanty et al.,2005;Orhan and Bujukgungor, 1993;Reddad et al.,2002;Tee and Khan,1988).These promising agricultural waste materials are used in the removal of metal ions either in their natural form or after some physical or chemical modiﬁcation.The present review article deals with the utilization of agricultural waste mate-rials as biosorbents for removal of toxic heavy metal ions from aqueous streams.2.Mechanism of biosorptionThe removal of metal ions from aqueous streams using agricultural materials is based upon metal biosorption (Volesky and Holan,1995).The process of biosorptionTable1Permissible limits and health eﬀects of various toxic heavy metalsMetal contaminant Permissible limits for industrial eﬄuent discharge(in mg/l)Permissiblelimits byinternationalbodies(l g/l)Health hazardsInto inland surfacewaters IndianStandards:2490(1974)Into publicsewers IndianStandards:3306(1974)On land forirrigation IndianStandards:3307(1974)WHO USEPAArsenic0.200.200.201050Carcinogenic,producing liver tumors,skin andgastrointestinal eﬀectsMercury0.010.01–0102Corrosive to skin,eyes and muscle membrane,dermatitis,anorexia,kidney damage and severemuscle painCadmium 2.00 1.00–0305Carcinogenic,cause lungﬁbrosis,dyspnea andweight lossLead0.10 1.00–1005Suspected carcinogen,loss of appetite,anemia,muscle and joint pains,diminishing IQ,causesterility,kidney problem and high blood pressure Chromium0.10 2.00–50100Suspected human carcinogen,producing lungtumors,allergic dermatitisNickel 3.0 3.0–––Causes chronic bronchitis,reduced lung function,cancer of lungs and nasal sinusZinc 5.0015.00–––Causes short-term illness called‘‘metal fume fever”and restlessnessCopper 3.00 3.00––1300Long term exposure causes irritation of nose,mouth,eyes,headache,stomachache,dizziness,diarrhea 6018 D.Sud et al./Bioresource Technology99(2008)6017–6027involves a solid phase(sorbent)and a liquid phase(solvent) containing a dissolved species to be sorbed.Due to high aﬃnity of the sorbent for the metal ion species,the latter is attracted and bound by rather complex process aﬀected by several mechanisms involving chemisorption,complexa-tion,adsorption on surface and pores,ion exchange,chela-tion,adsorption by physical forces,entrapment in inter and intraﬁbrillar capillaries and spaces of the structural poly-saccharides network as a result of the concentration gradi-ent and diﬀusion through cell wall and membrane(Basso et al.,2002;Sarkanen and Ludwig,1971;Qaiser et al., 2007)(Fig.1).Agricultural waste materials are usually composed of lignin and cellulose as the main constituents.Other compo-nents are hemicellulose,extractives,lipids,proteins,simple sugars,starches,water,hydrocarbons,ash and many more compounds that contain a variety of functional groups present in the binding process.Cellulose is a crystalline homo-polymer of glucose with b1?4glycosidic linkage and intra-molecular and intermolecular hydrogen bonds (Demirbas,2000a,b).Hemicellulose is a heteropolymer of mainly xylose with b1?4glycosidic linkage with other substances of acetyl feruoyl and glycouronyl groups(Garg et al.,in press).Lignin is three dimensional polymer of aro-matic compounds covalently linked with xylans in hard-woods and galactoglucomannans in softwoods(Garg et al.,2007;Sjo¨tro¨m,1981)The functional groups present in biomass molecules acetamido groups,carbonyl,pheno-lic,structural polysaccharides,amido,amino,sulphydryl carboxyl groups alcohols and esters(Beveridge and Mur-ray,1980;Gupta and Ali,2000).These groups have the aﬃnity for metal complexation.Some biosorbents are non-selective and bind to a wide range of heavy metals with no speciﬁc priority,whereas others are speciﬁc for certain types of metals depending upon their chemical composi-tion.The presence of various functional groups and their complexation with heavy metals during biosorption pro-cess has been reported by diﬀerent research workers usingD.Sud et al./Bioresource Technology99(2008)6017–60276019spectroscopic techniques(Ahluwalia and Goyal,2005a; Garg et al.,2007;Tarley and Arruda,2004).3.Absorption modelsPredicting the rate at which adsorption takes place for a given system is probably the most important factor in adsorption system design,with adsorbate residence time and the reactor dimensions controlled by the system’s kinet-ics.Numerous kinetic models have described the reaction order of adsorption systems based on solution concentra-tion.These includeﬁrst-order and second-order reversible ones,andﬁrst-order and second-order irreversible ones, pseudo-ﬁrst-order and pseudo-second-order.The sorption isotherms represent the relationship between the amount adsorbed by a unit weight of solid sorbent and the amount of solute remaining in the solution at equilibrium(Park et al.,2006).Both Langmuir and Freundlich isotherm mod-els have been shown to be suitable for describing short-term and mono component adsorption of metal ions by diﬀerent biosorbents(Aksu et al.,1999;Ho et al.,2002).On the other hand,reaction orders based on the capacity of the adsor-bent have also been studied,such as Lagergren’sﬁrst-order equation,Redlich Peterson model and BET model(Ho and Mckay,1998).Langmuir and Freundlich isotherm models are frequently used isotherm models for describing short-term and mono component adsorption of metal ions by diﬀerent materials(Aksu et al.,1999;Yu et al.,2001).4.Thermodynamic parametersThe free energy change of sorption can be calculated by Eq.(1).D G0¼ÀRT ln Kð1Þwhere D G0is standard free energy change,R is the univer-sal gas constant(8.314J/mol/K),T is the absolute temper-ature and K is equilibrium constant.The apparentequilibrium constant of the biosorption,K0C is obtainedfrom Eq.(2).K0C¼CðbiosorbentÞeq=CðsolutionÞð2Þwhere C(biosorbent)eq and C(solution)eq are the metal ion concentrations on the biosorbent and in the solution at equilibrium.5.Performance of agricultural waste materials as biosorbents for the removal of heavy metalsRemoval of heavy metal ions from the aqueous streams by agricultural waste materials is an innovative and prom-ising technology.The eﬃciency of the waste material depends upon the capacity,aﬃnity,and speciﬁcity includ-ing physico-chemical nature of it.Scattered research has already been done on the variety of biosorbents for the removal of metal ions as Cr,Cu,Ni,Pb,Cd,As,Hg etc. The adsorbents are taken either in the natural form,or modiﬁed by chemical and thermal treatment for increasing their sorption capabilities.5.1.Removal of chromiumChromium is a toxic heavy metal being released in the environment by applications like tanning,wood preserva-tion and pigments,dyes for plastic,paints,and textiles. Chromium occurs in a number of oxidation states,but chromium(VI)and chromium(III)are of main environ-mental concern(Yu et al.,2000).Extensive work has been reported for the removal of chromium employing waste agricultural materials.A number of agricultural wastes like,hazelnut shells, orange peels,maize cobs,peanut shells,soyabean hulls, jack fruit,soyabean hulls in natural or modiﬁed forms has been explored and signiﬁcant removal eﬃciency was reported(Kurniawan et al.,2006).Diverse plant parts such as coconutﬁber pith,coconut shellﬁber,plant bark(Aca-cia arabica,Eucalyptus),pine needles,cactus leaves,neem leave powder have also been tried for chromium removal showing eﬃciency more than90–100%at optimum pH (Dakiky et al.,2002;Manju and Anirudhan,1997;Mohan et al.,2006a;Sarin and Pant,2006;Venkateswarlu et al., 2007).The utilization of rice bran and wheat bran as an adsorbent are found to be less eﬀective as only50% removal eﬃciency was reported(Farajzadeh and Monji, 2004;Oliveira et al.,2005).Gardea-Torresdey et al. (2000)reported Avena monida(whole plant biomass) showed90%removal eﬃciency of Cr VI at optimum pH 6.0.Rice husk in natural form as well as activated rice husk carbon was used for the removal of chromium(VI)and results were also compared with commercial activated car-bon and other adsorbents.(Bishnoi et al.,2004;Mehrotra and Dwivedi,1988;Srinivasan et al.,1988).Saw dust of Indian rose wood prepared by treatment with formaldehyde and sulphuric acid showed eﬃcient removal of chromium(VI)(Garg et al.,2004).Beech saw dust and rubber wood saw dust was also tried for chro-mium removal(Acar and Malkoc,2004;Karthikeyan et al.,2005).Sugarcane bagasse was used in natural as well as modiﬁed form and eﬃciency for both the forms was compared for the removal of Cr.(Gupta and Ali,2004; Krishanani et al.,2004;Rao and Parwate,2002).Utiliza-tion of mustard oil cake has been reported with signiﬁcant removal eﬃciency and the results of activated carbon of sugar industry waste and commercial granular activated carbon for sequestering of heavy metal ions from aqueous solutions were compared(Ajmal et al.,2005;Fahim et al., 2006).Recently sugar cane baggase,maize corn cob and jatropha oil cake as such were used for removal of chro-mium under optimized conditions(Garg et al.,2007).Most of the studies showed that the chromium biosorp-tion by agricultural waste materials is quite high and varies from50to100%.Mostly biosorption occurs in acidic range particularly at pH2.0.Thus chromium speciation plays the dominant role in deciding the removal eﬃciency as at pH26020 D.Sud et al./Bioresource Technology99(2008)6017–6027chromium is present as chromium(III).Table2summa-rizes the work reported in literature for the removal of chromium by using agricultural waste materials.5.2.Removal of leadThe major source of lead in the environment is from plastics,ﬁnishing tools,cathode ray tubes,ceramics,sol-ders,pieces of leadﬂashing and other minor product,steel and cable reclamation.Lead can result in the wide range of biological eﬀects depending upon the level and duration of exposure(Friberg and Elinder,1985).In the environment lead binds strongly to particles such as oil,sediments and sewage sludge so its removal is of great concern.Diﬀerent agricultural wastes viz.rice straw,soybean hulls,sugarcane bagasse,peanut shells and walnut shells in their natural form have been used for removal of lead has been reported98%(Johns et al.,1998).Bankar and Dara(1985)conducted studies on Febrifuga tree bark in its natural form.Petioler felt sheath palm(PFP),agro waste of black gram husk,ﬂowers of Humulus lupulus, waste tea leaves and water hyacinth were studied for removal of lead and eﬃciency of these materials varies from70to98%(Ahluwalia and Goyal,2005a;Gardea-Torresdey et al.,2002;Iqbal et al.,2002,2005;Kamble and Patil,2001;Saeed et al.,2005b).Lee et al.(1999)investigated removal of lead and other metal ions by apple residues modiﬁed with phosphorous (V)oxychloride in both batch and column studies and com-pared the results.Rose petals pretreated with NaOH,cal-cium treated sargassum and sugarcane modiﬁed with succinic anhydride has also been utilized for signiﬁcant removal of lead.(Karnitz et al.,2007;Nasir et al.,2007;Tsui et al.,2006).Activated carbon prepared from agricultural waste was also explored by diﬀerent workers and high eﬃ-ciency for removal of lead has been reported.(Gajghate et al.,1991;Kadirvelu et al.,2001;Vaughan et al.,2001;Wil-son et al.,2006).Gupta et al.(1999)used bagasseﬂy ash for removal of lead with65%removal eﬃciency.Saw dust of maple(Zhang et al.,1998),Pinus sylvestries(Taty-Costodes et al.,2003)and rubber wood saw dust(Raji et al.,1997)has shown85–90%removal eﬃciency but results show that modiﬁcation did not enhance the removal eﬃciency for lead. Literature studies revealed that optimized value for biosorp-tion of lead is found around pH5–6(Table3).5.3.Removal of cadmiumCadmium and Cadmium compounds as compared to other heavy metals are relatively water soluble therefore mobile in soil and tends to bioaccumulate.The long life time PVC-window frames,plastics and plating on steel are the basic sources of cadmium in the environment.Cad-mium accumulates in the human body especially in kid-neys,thus leading to disfunction of the kidney(Volesky and Holan,1995).Potential use of rice bran and wheat bran was tried for sequestering cadmium and signiﬁcant removal eﬃciency was reported(Montanher et al.,2005;Farajzadeh and Monji,2004;Singh et al.,2005).Studies were also con-ducted on use of rice polish,rice husk and black gram husk in their natural as well as modiﬁed form for the removal of cadmium and their relative eﬃciency was reported(Iqbal et al.,2005;Kumar and Bandyopadhyay, 2006;Singh et al.,2005;Tarley and Arruda,2004).Bark of the plants such as Pecia glehnii and Abies sachalinensis and dried plant biomass of parthenium was tried for the removal of cadmium(Ajmal et al.,2006;Seki et al., 1997).Use of other parts of the plants such as peels of peas,ﬁg leaves,broad beans,orange peels,medlar peels and jack fruits as adsorbents have been reported to show high removal eﬃciency at acidic pH(Benaissa,2006).Table2Summary of work done by various researchers using low cost agricultural waste materials for the removal of chromiumAgricultural waste Metal ion Results ReferenceOat biomass Cr(III),Cr(VI)>80%Gardea-Torresdey et al.(2000) Formaldehyde treated saw dust Indian rosewood Cr(VI)62–86%Garg et al.(2004)Beech saw dust Cr(VI)100%Acar and Malkoc(2004) Chemically treated bagasse Cr(VI)50–60%Krishanani et al.(2004) Formaldehyde treated rice husk Cr(VI)88.88%Bishnoi et al.(2004) Bagasseﬂy ash Cr(VI)96–98%Gupta and Ali(2004)Wheat bran Cr(VI)>82%Farajzadeh and Monji(2004) Coconut shellﬁbers Cr(VI)>80%Mohan et al.(2006a) Commercial granular Cr(VI)93–98%Fahim et al.(2006)activated carbon(C2&C3)and AC of waste from sugar industry(C1)C1>C2>C3Eucalyptus bark Cr(VI)Almost100%Sarin and Pant(2006)Neem leaf powder Cr(VI)>96%Venkateswarlu et al.(2007) Rubber wood saw dust Cr(VI)60–70%Karthikeyan et al.(2005) Pretreated bagasse with NaOH and CH3COOH Cr(VI),Ni(II)90%,67%Rao et al.(2002)Modiﬁed bagasseﬂy ash Cr(VI)67%Gupta et al.(1999)Activated carbon from bagasse(carbonization&gasiﬁcation)Cr(VI)Signiﬁcant metal uptake Valix et al.(2006) Sugarcane bagasse,maize corn cob,jatropha oil cake Cr(III)Upto97%Garg et al.(2007)Raw rice bran Cr(VI),Ni(II)40–50%Oliveira et al.(2005)D.Sud et al./Bioresource Technology99(2008)6017–60276021Adsorption experiments conducted on hazelnut shells, peanut hulls,walnut shells,and green coconut shells gave signiﬁcant results for removal of cadmium(Johns et al., 1998;Kurniawan et al.,2006).Studies were conducted on activated carbon of bagasse pith,coir pith,peanut shells and dates and their removal eﬃciency varies from 50to98%(Kadirvelu et al.,2001;Kannan and Rengas-amy,2005;Krishnan and Anirudhan,2003;Mohan and Singh,2002;Srivastva et al.,1996;Wafwoy et al.,1999). Research has also been carried out by using chemically treated agricultural waste materials like base treated rice husk,treated juniperﬁbers,and corncob modiﬁed with citric acid,modiﬁed peanut shells,succinic anhydride trea-ted sugarcane etc.(Karnitz et al.,2007;Min et al.,2004; Vaughan et al.,2001).Most of the studies showed that agricultural waste either in natural form or modiﬁed form is highly eﬃcient for the removal of cadmium metal ions.Summary of research work done has been compiled in Table4.5.4.Removal of nickelNickel and its compounds have no characteristic odor or taste.The sources of nickel to the environment are nickel plating,colored ceramics,batteries,furnaces used to make alloys or from power plants and trash incinerators.The most harmful health eﬀect of nickel is the allergic reactions (Akhtar et al.,2004).Experiments on removal of nickel were conducted on Cassiaﬁstula biomass in its natural form and results show99–100%removal eﬃciency(Hanif et al.,2007). Waste tea leaves were also tried for sequestering of nickel from aqueous solutions(Ahluwalia and Goyal, 2005a).Saw dust of maple,oak and black locust have been reported as promising biosorbent for removal of nickel(Sciban et al.,2006;Shukla et al.,2005).Agricul-tural wastes such as peanut,pecan,walnut,hazelnut and groundnut shells in natural or modiﬁed form were also utilized for biosorption(Demirbas et al.,2002;Johns et al.,1998;Kurniawan et al.,2006;Shukla and Pai, 2005).Other agricultural waste materials as modiﬁed coir ﬁbers,cotton seeds,soyabeans and corncobs have also been explored for removal of nickel(Marshall and Johns, 1996;Shukla et al.,2005;Vaughan et al.,2001).Sugar cane bagasse in its natural form showed more than 80%removal eﬃciency(Garg et al.,2007).Table5is a compilation of research work done on the removal of nickel.Table3Summary of work done by various researchers using variety of agricultural waste materials for the removal of LeadAgricultural waste Metal ion Results ReferenceOriza sativa husk Pb(II)98%Zulkali et al.(2006) Agricultural by product Humulus lupulus Pb(II)75%Gardea-Torresdey et al.(2002) Chemical modiﬁed apple residue waste Pb(II)Upto80%Lee et al.(1999)Agro waste of black gram husk Pb(II)Upto93%Saeed et al.(2005b) Febrifuga bark Pb(II)100%Bankar and Dara(1985) Chemically modiﬁed saw dust of rubberwoodPb(II)85%Raji and Anirudhan(1998) Coconut char based activated carbon Pb(II)100%Gajghate et al.(1991)Rose biomass pretreated with NaOH Pb,Zn(II)75%Nasir et al.(2007)Rice bran Pb(II),Cd(II),Cu(II),Zn(II)>80.0%Montanher et al.(2005)Saw dust of Pinus sylvestris Pb(II),Cd(II)96%,98%Taty-Costodes et al.(2003) Maple saw dust Pb(II),Cu(II)80–90%Yu et al.(2001)60–90%Water hyacinth Pb(II),Cu(II),Co(II),Zn(II)70–80%Kamble and Patil(2001)Low cost sorbents(bark,dead biomass,chitin,sea weed,algae,peat moss,leafmould,moss,zeolite,modiﬁed cotton)etc.Pb(II),Cd(II),Cr(VI),Hg(II)Good results Bailey et al.(1999)Waste tea leaves Pb(II),Fe(II),Zn(II),Ni(II)92%,84%,73%Ahluwalia and Goyal(2005b) Activated carbon from coir pith Pb(II),Hg(II),Cd(II),Ni(II),Cu(II)Hg-100%Kadirvelu et al.(2001)Pb-100%Cu-73%Ni-92%Cd-!00%Rice straw,soybean hulls,sugarcane bagasse,peanut shells,pecan and walnut shells Pb(II),Cu(II),Cd(II),Zn(II),Ni(II)Pb>Cu>Cd>Zn>Ni Johns et al.(1998)PFP(petiolar felt sheath palm)-peelings from trunk of palm tree Pb(II),Cd(II),Cu(II),Zn(II),Ni(II),Cr(VI)>70%Pb>Cd>Cu>Zn>Ni>CrIqbal et al.(2002)Activated carbon of peanut shells Pb(II),Cd(II),Cu(II),Ni(II),Zn(II)Upto75%Wilson et al.(2006)6022 D.Sud et al./Bioresource Technology99(2008)6017–6027Table4Summary of work done by various researchers using variety of agricultural waste materials for the removal of cadmiumAgricultural waste Metal ion Results ReferencePeels of peas,ﬁg leaves,broad beans,medlar peel Cd(II)70–80%Benaissa(2006)Wheat bran Cd(II)87.15%Singh et al.(2005)Three kinds treated rice husk Cd(II)80–97%Kumar and Bandyopadhyay(2006)Rice polish Cd(II)>90%Singh et al.(2005)Steam activated sulphurised carbon(SA–S–C) from bagasse pith Cd(II)98.8%Krishnan and Anirudhan(2003)Base treated juniperﬁber Cd(II)High removal capacity Min et al.(2004)Husk of black gram Cd(II)99%Saeed and Iqbal(2003) Straw,saw dust,datesnut Cd(II)>70%Dried parthenium powder Cd(II)>99%Ajmal et al.(2006) Bagasseﬂy ash Cd(II),Ni(II)65&42%Srivastava et al.(2007) Bagasse Cd(II),Zn(II)90–95%Mohan and Singh(2002) Bagasseﬂy ash Cd(II),Ni(II)90.0%Gupta et al.(2003)Rice bran Cd(II),Cu(II),Pb(II),Zn(II)>80.0%Montanher et al.(2005) Wheat bran Cd(II),Hg(II),Pb(II),Cr(VI),Cu(II),Ni(II)>82%except Ni Farajzadeh and Monji(2004)Hazelnut shell,orange peel,maize cob,peanut hulls,soyabean hulls treated with NaOH&jack fruits Cd(II),Cr(VI),Cu(II),Ni(II),Zn(II)High metal adsorption Kurniawan et al.(2006)Papaya wood Cd(II),Cu(II),Zn(II)98,95,67%Saeed et al.(2005a)Rice straw,soybean hulls,sugarcane bagasse, peanut shells,pecan and walnut shells Cd(II),Pb(II),Cu(II),Zn(II),Ni(II)Pb>Cu>Cd>Zn>Ni Johns et al.(1998)Poplar wood saw dust Cd(II),Cu,Zn(II)Cu>Zn>Cd Sciban et al.(2007) Chemically modiﬁed sugarcane with succinicanhydrideCd(II),Cu(II),Pb(II)>80%Karnitz et al.(2007) Powder of green coconut shell Cd(II),Cr(II),As(II)98%Pino et al.(2006)Bark of Abies sachalinensis&Pecia glehnii Cd(II),Cu(II),Zn(II),Ag(II),Mn(II),Ni(II)Upto63%Seki et al.(1997)Table5Summary of work done by various researchers using variety of agricultural waste materials for the removal of nickelAgricultural waste Metal ion Results ReferenceHazelnut shell activated carbon Ni(II)Eﬀective removal Demirbas et al.(2002)Casiaﬁstula biomass Ni(II)100%Hanif et al.(2007)Maple saw dust Ni(II)75%Shukla et al.(2005) Sugarcane bagasse Ni(II)>80%Garg et al.(2007)Tea waste Ni(II)86%Malkoc and Nuhoglu(2005) Defatted rice bran,chemically treatedsoybean&cottonseed hullsNi(II),Zn(II),Cu(II)57%,87%Marshall and Johns(1996) Waste tea leaves Ni(II),Pb(II),Fe(II),Zn(II)92%,84%,73%Ahluwalia and Goyal(2005a) Saw dust of oak and black locust hardwood(modiﬁed&unmodiﬁed)Ni(II),Cu(II),Zn(II)70–90%Sciban et al.(2006)Hazelnut shell,orange peel,maize cob, peanut hulls,soyabean hulls treated with NaOH&jack fruits Ni(II),Cr(II),Cu(II),Cd(II),Zn(II)High metal adsorption Kurniawan et al.(2006)Mustard oil cake Ni(II),Cu(II),Zn(II),Cr(II),Mn(II),Cd(II),Pb(II)Upto94%Ajmal et al.(2005) Coirﬁber chemically modiﬁed withhydrogen peroxideNi(II),Zn(II),Fe(II)>70%Shukla et al.(2005) Dye loaded groundnut shells and sawdustNi(II),Cu(II),Zn(II)Up to90%Shukla and Pai(2005)PFP(petiolar felt sheath palm)-peelings from trunk of palm tree Ni(II),Pb(II),Cd(II),Cu(II),Zn(II),Cr(VI)>70%Pb>Cd>Cu>Zn>Ni>CrIqbal et al.,2002Agro waste of black gram husk Ni(II),Pb(II),Cd(II),Cu(II),Zn(II)Upto93%Saeed et al.(2005b)Modiﬁed&unmodiﬁed kenaf core,kenaf bast,sugarcane bagasse,cotton,coconut coir,spruce Ni(II),Cu(II),Zn(II)Upto88%Sciban et al.(2007)D.Sud et al./Bioresource Technology99(2008)6017–60276023。

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