rGO-Fe3O4 合成

Chem. Res. Chin. Univ., 2015, 31(4), 508―513doi: 10.1007/s40242-015-4487-6———————————*Corresponding author. E-mail: zhouwei@ Received December 15, 2014; accepted April 8, 2015.Supported by the National Natural Science Foundation of China(Nos.51438011, 51102005), the Foundation for the Author of National Excellent Doctoral Dissertation of China(No.201331) and the Program for New Century Excellent Talents in University, China(No.NCET-13-0032).© Jilin University, The Editorial Department of Chemical Research in Chinese Universities and Springer-Verlag GmbHOne-pot Hydrothermal Synthesis of rGO-Fe 3O 4 HybridNanocomposite for Removal of Pb(II) viaMagnetic SeparationCAO Wei, MA Yiran, ZHOU Wei * and GUO LinSchool of Chemistry and Environment, Beihang University, Beijing 100191, P. R. ChinaAbstract The reduced graphene oxide-Fe 3O 4(rGO-Fe 3O 4) hybrid nanocomposite was prepared via a one-pot facile hydrothermal method for adsorption of heavy metal ions. The results of compositional and morphological characteri-zations show that the Fe 3O 4 NPs with an average diameter of 20 nm have been uniformly dispersed in rGO sheets. Due to the higher specific surface area of rGO and the magnetic properties of Fe 3O 4 nanoparticles, the prepared rGO-Fe 3O 4 hybrid nanosheets showed good adsorption capacity for the removal of Pb(II) from wastewater by simple magnetic separation. The result of control tests show that the adsorption capacity of rGO-Fe 3O 4 can be influenced by the ratio of ferric chloride(FeCl 3) to graphene oxide(GO) during the process of sample preparation and the initial concentration of Pb(II). A better adsorption capacity was 30.68 mg/g at n (FeCl 3)/m (GO) ratio of 1:5(mmol:mg) at pH=7.0 with the initial concentration of Pb(II) ions of 80 mg/L, and the experimental data were well fitted with the Langmuir adsorption model. The composite with absorbed Pb(II) can be easily collected by magnetic separation from wastewater because of the excellent magnetism of Fe 3O 4 NPs. The rGO-Fe 3O 4 hybrid nanocomposite provides an ef-fective and environment-friendly absorbent with great application potential in water purification. Keywords Graphene; Nanocomposite; Adsorption; Magnetic separation1 IntroductionEnvironmental contamination has become an urgent issue nowadays, especially the pollution of heavy metal ions from metal plating, alloy manufacturing, metallurgy, chemical ma- nufacturing and mining and battery industries. Heavy metal ions are easy to accumulate in living organisms but hard to biodegrade, which can cause mass mortality of aquatic lives and cancers even death of human beings. Tremendous efforts have been devoted to degrading heavy metal ions with various methods including chemical precipitation [1], adsorption [2], membrane filtration [3] and photocatalytic degradation [4], etc. Among these methods, adsorption is a widely used traditional method because of its high efficiency, low cost, ease of opera-tion and regeneration [5]. And various adsorbents, such as silica gel [6], activated alumina [7], fly ash [8], coconut shell [9], sugarcane bagasse [10] and many kinds of carbon materials have been deve- loped.As a new type of two-dimensional carbon-based nano- material with one-atom thickness, graphene arouses global attention because of its superior performances in many fields. Due to its large specific surface area(2630 m 2/g)[11], graphene has been considered as an ideal absorbent for water purifica- tion. However, graphene composing of carbon atoms only haspoorly solubility in water, thus graphene oxide(GO) and re-duced graphene oxide(rGO) with oxygen-groups on their sur-faces are used as adsorbents instead. But the separation was rather difficult when GO or rGO sheets were used as their light-weight thin layers [12]. Therefore, magnetic NPs could be introduced to form (r)GO-magnetic NPs hybrid adsorbents and simple magnetic separation could be achieved.Magnetite(Fe 3O 4) is an excellent ferromagnetic material with high saturation magnetization and good biocompatibili-ty [13] and has been used as added components of adsorbents for magnetic separation with an external magnet and without cen-trifugation or filtration. There are lots of ways to synthesize Fe 3O 4 nanoparticles with different sizes and morpholo-gies [14―16]. For the above reasons, rGO-Fe 3O 4 would be an ideal absorbent combining the merits of adsorption properties of rGO with the easy separation of magnetic nanoparticles.In this work, we presented a one-pot facile method to produce the rGO-Fe 3O 4 hybrid nanocomposite for the removal of Pb(II) ions. The Fe 3O 4 nanoparticles with an average diame-ter of 20 nm were loaded on the both sides of rGO sheets through in situ reduction of FeCl 3. The adsorption of Pb(II) ions and the magnetic separation were carried out to confirm the good adsorption capacity and the easy magnetic separation of hybrid sheets.No.4CAO Wei et al.5092 Experimental2.1 MaterialsAll the chemicals were analytical grade and used without further purification. The ultrapure water(Milli-Q) was used throughout the adsorption experiments.2.2 Synthesis of GOGO was prepared from natural graphite powder(325 meshes) via a modified Hummers method [17]. In brief, 15 mL of concentrated sulfuric acid was mixed with 3.0 g of graphite powder, 2.5 g of K 2S 2O 8 and 2.5 g of P 2O 5. The mixture was kept stirring for 6 h at 80 °C, and then poured into 500 mL of deionized water under stirring. After centrifugation and drying, the black product was mixed with 115 mL of concentrated sul-furic in an ice bath. After that, 15 g of KMnO 4 was slowly added and the mixture was stirred for 2 h at 35 °C. Deionized water of 250 mL was added to the mixture and the solution was stirred for another 2 h at 20 °C. An additional of 700 mL of deionized water was added, followed by 10 mL of H 2O 2(30%, mass fraction) added. Finally, the mixture was centrifuged and washed with HCl(10%, mass fraction) and deionized water, respectively, until the solution was neutral. The condensed GO aqueous solution, which could remain stable for several months, was stored for further use.2.3 Synthesis of rGO-Fe 3O 4 NanocompositeThe rGO-Fe 3O 4 hybrid nanocomposite was prepared through one-pot hydrothermal method. In a typical synthesis process, 3 mmol of FeCl 3 was dissolved in 20 mL of ethylene glycol(EG) and sonicated for 30 min, followed by 1 mL of hydrazine(80%, mass fraction) added under stirring. Subse-quently, 10 mL of GO(1.50 mg/mL) was dispersed in the solu-tion under sonication. Finally, 10 mmol of urea was added un-der continuous stirring. The mixture was then transferred into a 40 mL Teflon-lined stainless steel autoclave at 180 °C and kept for 10 h. Then the autoclave was cooled to room temperature. The obtained black product was washed with deionized water and ethanol, separately, several times and dried at 60 °C in an oven. Fe 3O 4 NPs were synthesized in the same procedure without adding GO for comparison.2.4 CharacterizationThe morphology and structure of the hybrid composite were studied by means of scanning electron microscopy(SEM, Quanta 250 FEG ）and transmission electron microscopy(TEM, JEOL JEM-2100F). TEM specimens were obtained by dipping carbon-capped copper grids into the solution. The structure and composition of the as-prepared product was characterized on a Rigaku Dmax2200 X-ray diffractometer with Cu K α radia-tion(λ=0.15416 nm). The XRD specimen was prepared by flat-tening the powder on small slides. The magnetic measurement was performed on an MPMS-XL SQUID magnetometer at 300 K. Raman spectroscopy measurements were performed on aLabRAM HR800 system with an excitation wavelength of 633 nm and the silicon peak at 520 cm –1 as a reference. Fourier transform infrared(FTIR) spectra were obtained on a Thermo Nicolet iN10MX instrument. The adsorption experiment was performed in a water bath oscillator(SHZ-82A), and the con-centration of heavy metal ions in the aqueous solution was analyzed via an inductively coupled plasma optical emission spectrometer(ICP-OES, Agilent 710).2.5 Adsorption ExperimentsThe adsorption experiments were carried out by adding 40 mg of the rGO-Fe 3O 4 nanocomposite to the Pb(II) aqua-solutions with different initial concentrations in 100 mL conical flasks. The initial concentrations varied from 20 mg/L to 100 mg/L while the pH maintained at 7.0. The mixture was put on a shaking table at room temperature and shaken for 10 h. After reaching the equilibrium, the adsorbent was separated from the solution via a permanent magnet. The equilibrium concentration of Pb(II) in the supernatant was analyzed by means of ICP-OES. The amount of Pb(II) adsorbed by rGO-Fe 3O 4 was revealed as different values between the initial and the equilibrium concentrations of Pb(II). The adsorption capacity of adsorbent for Pb(II)(q e , mg/g) was calculated accor- ding to the following equation:q e =(c i –c e )V /m (1)where c i and c e are the initial and the final concentrations of Pb(II)(mg/L), respectively; V is the volume of Pb(II) solu-tion(mL); m is the mass of the absorbent(mg).3 Results and DiscussionThe morphology of the rGO-Fe 3O 4 hybrid nanocomposite was studied by means of SEM and TEM. Fig.1(A) and (B) display the low and high magnified SEM images of the sample, respectively, which show that NPs are well dispersed on the 2D crumpled rGO sheets because rGO sheets could prevent the Fe 3O 4 NPs from aggregation. TEM image in Fig.1(C) also shows that NPs with an average diameter of 20 nm have beenFig.1 Low(A) and high(B) magnification SEMimages, TEM(C) and HRTEM(D) images of the rGO-Fe 3O 4 hybrid composite(D) corresponds to the marked frame in (C).510Chem. Res. Chin. Univ.Vol.31loaded on the thin layers. The HRTEM image in Fig.1(D) cor-responding to the marked frame in Fig.1(C), shows the particle with a lattice spacing of 0.24 nm, which could be ascribed to the (222) planes of Fe 3O 4.Fig.2(A) shows the XRD pattern of the rGO-Fe 3O 4 hybrid nanocomposite. GO has a strong peak at 2θ=10.1°, corres-ponding to the (001) plane with interplanar spacing of 0.87nm [18], which couldn’t be observed here. Instead, fromFig.2(A), the broad peak around 2θ=24.6° marked with asterisk shows up, indicating GO has been reduced to rGO [19]. The diffraction peaks of the as-synthesized product at 2θ=18.5°, 30.3°, 35.8°, 37.4°, 43.5°, 53.9°, 57.5°, 63.1°, 71.7° and 74.7° can be assigned to the crystalline planes of (111), (220), (311), (222), (400), (422), (511), (440), (620) and (533) of Fe 3O 4, in agreement with the component of Fe 3O 4(JCPDS No.75-0449).Fig.2 XRD patern(A), FTIR spectra(B) and Ramanspectrum(C) of rGO-Fe 3O 4 nanocomposite(B) a . rGO-Fe 3O 4; b . Fe 3O 4; c . GO.FTIR spectra of GO, Fe 3O 4 and rGO-Fe 3O 4 nanocompo-sites are shown in Fig.2(B). The spectrum of GO shows O ―H stretching vibration in the region of 3000―3400 cm –1, C =O(carbonyl and carboxylic groups) stretching vibration at 1735 cm –1, C =C stretching peak(unoxidized sp 2 C hybridiza-tion) at 1610 cm –1, O ―H bend vibration at the peaks at 1406 cm –1 as well as C ―O(epoxy), C ―O(alkoxy) stretching and C ―O(epoxy) bend vibrations at 1232, 1048 and 870 cm –1,respectively [20]. For Fe 3O 4, the peak at 572 cm –1 is a characte-ristic peak corresponding to the stretching vibration of Fe ―O [21]. While rGO-Fe 3O 4 shows two peaks at 1526 and 1192 cm –1, which correspond to the aromatic C =C stretch and C ―O stretch, respectively, indicating the successful reduction of GO to rGO. Also, the band intensity of Fe ―O vibration increases and shifts, indicating the formation of Fe ―O bond between rGO and Fe 3O 4, and a high iron loading in rGO-Fe 3O 4.Raman spectroscopy has been proved to be an essential tool to study the ordered/disordered crystal structures of carbo-naceous materials. The structural change of GO to rGO during the reaction was further investigated by Raman spectroscopy. As shown in Fig.2(C), two prominent peaks at 1330 and 1590 cm –1 correspond to the well documented D band and G band, respectively. Usually, G band can be assigned to the E 2g phonon of sp 2 bonds of carbon atoms, and D band is associated with local defects and disorders, especially the defects located at the edges. Thus, the intensity ratio of D band to G band(I D /I G ) is usually used as a measure of the disorder. For GO, the intensity of G band is higher than that of D band with I D /I G <1, while opposite result could be got after reduction [22]. As for our rGO-Fe 3O 4 composite, the ratio of I D /I G was 1.83, indicating the reduction of GO to rGO after the reaction process.Fig.3(A) and (B) show the magnetization properties of the rGO-Fe 3O 4 nanocomposite and pure Fe 3O 4 NPs under applied magnetic field ranging from –2 T to 2 T at 300 K, respectively. Fe 3O 4 NPs were synthesized following the preparation proce-dure of rGO-Fe 3O 4 composite without adding GO. The mor-phology of Fe 3O 4 NPs is shown in Fig.3(C).The values of saturation magnetization(M s ) of Fe 3O 4 NPs and rGO-Fe 3O 4 composite are 68.03 and 60.00 A·m 2/kg, re-spectively. The small decrement of the saturation magnetization of the rGO-Fe 3O 4 composite might be due to the lessened quan-tity of Fe 3O 4 in the composites. That is, the rGO sheets have no obvious effect on the magnetism of the loaded Fe 3O 4 NPs. Be-sides, the value of M s for the as-synthesized composite is higher than those of other rGO-Fe 3O 4 nanocomposites reported [23,24], which might depend on the loading amount of Fe 3O 4 NPs on rGO sheets.When the rGO-Fe 3O 4 composite is used as the adsorbent for heavy metal ions, it is considered the most adsorption ca-pacity comes from rGO while Fe 3O 4 mainly provides magne- tism. The adsorption capacity can be improved by adding more GO in the reaction system, thus a series of composites with different ratios of n (FeCl 3):m (GO) was synthesized. But the data shown in Fig.4 reveal an opposite result. At the same initial concentrations of 80 mg/L of Pb(II), the adsorption of Pb(II) can be affected by the ratio of the two substances. When the ratio of n (FeCl 3):m (GO) is 1:5(mmol:mg), the adsorption capacity of the composite reaches the maximum value of 30.68 mg/g, while a higher and a lower ratio of n (FeCl 3) to m (GO) can both lead to a decrement of adsorption capacity. The phe-nomenon could be attributed to the Fe 3O 4 NPs anchored on rGO, which keeps layered rGO from stacking, and thus gives the composite smaller adsorption surfaces and active sites. The composites can stack easily and can form thick layers with lower specific surface areas when more GO sheets are addedNo.4 CAO Wei et al.511 Fig.3 Magnetization curves of Fe3O4(a) and rGO-Fe3O4(b) nanocomposites at 300 K(A), theenlarged partial magnetization curve ofrGO-Fe3O4 composites(B) and SEM image ofpure Fe3O4 NPs(C)Fig.4 Adsorption of Pb(II) on a series of rGO-Fe3O4nanocomposites prepared by adding differentratios of FeCl3 and GOExperiment conditions: initial Pb(II) concentration: 80 mg/L; pH=7.0;temperature: (25±2) °C; contact time: 10 h.during the composite preparation. While at higher ratios ofFeCl3, serious agglomerations of Fe3O4 NPs occur, and also dothe too lower content of rGO as main adsorbent, which can leadto a lower adsorption capacity. Thus, a ratio of n(FeCl3):m(GO)of 1:5(mmol:mg) matches best to obtain the maximum adsorp-tion. That is, Fe3O4 NPs provide magnetic properties and areused as structure stabilizer for the hybrid nanocomposite.The adsorption isotherm of Pb(II) on the rGO-Fe3O4composite with n(FeCl3):m(GO) ratio of 1:5(mmol:mg) isshown in Fig.5. The initial concentrations of Pb(II) ions rangefrom 20 mg/L to 100 mg/L. It is clearly observed that the Pb(II)adsorption increases rapidly with the initial Pb(II) concentra-tions less than 80 mg/L. At an initial concentration(c0) of 80mg/L, adsorption capacity reaches a maximum of 30.68 mg/g.The inset of Fig.5 shows the digital photos of the magneticresponse of the nanocomposites towards an exterior magneticfield. It can be seen that the rGO-Fe3O4 composite after ad-sorbing Pb(II) has been quickly separated from the solution bya magnet. It is essentially important for the convenient recy-cling of the rGO-Fe3O4 nanocomposite.Fig.5 Adsorption isotherm of Pb(II) on therGO-Fe3O4 hybrid compositeExperiment conditions: pH=7.0, temperature: (25±2) °C, contact time: 10 h.Insect photos of the rGO-Fe3O4 composite responding to a magnet in Pb(II)solution before(left) and after(right) adsorption.The adsorption capacities of various adsorbents for theremoval of Pb(II) ions are summarized in Table 1. Comparedwith activated carbon[25], CNTs[26] or graphene[27], the as pre-pared rGO-Fe3O4 shows higher adsorption capacity because theFe3O4 NPs can prevent the composite sheets from stacking(providing more specific surface area) and more oxygen-containing functional groups on the surfaces(providing moreadsorption sites via electrostatistic interaction for positivecharge heavy metal ions). However, compared to those adsor-bents, such as Fe3O4-poly(L-cysteine/2-hydroxyethyl acry-late)[28], thiol-functionalized CNTs/Fe3O4[29] and Fe3O4/cyclo-dextrin polymer[30], the adsorption capacity of our product isrelative lower. It can be ascribed to those functionalized adsor-bents with much more functional groups, which can bind moreheavy metal ions. But the synthesizing procedures of theabove adsorbents are more comparable with that of ourone-pot hydrothermal method. Obviously, the organicTable 1 Comparison of adsorption capacities of dif-ferent adsorbents for the removal of Pb(II)Type of adsorbentAdsorption capacityof Pb(II) /(mg·g–1)ReferencePowdered activated carbon 26.90 [25]Multiwalled carbon nanotubes 3.00 [26]Magnetic graphene 6.00 [27]Fe3O4-poly(L-cysteine/2-hydroxyethyl acrylate)38.69 [28]Thiol-functionalized CNTs/Fe3O465.40 [29]Fe3O4/cyclo-dextrin polymer 64.50 [30]512 Chem. Res. Chin. Univ. Vol.31molecules-functionalized materials provide higher adsorptioncapacity, which would be the key point of our further work.The experimental data for the Pb(II) adsorption on therGO-Fe 3O 4 composite were further analyzed via the Langmuir and Freundlich adsorption isotherm models. The equations ofthese two isotherm models are displayed in Eqs.(2) and (3), respectively.e m e e L m11c q c q K q =+ (2) e F e lg lg 1/lg q K n c =+ (3)where c e is the equilibrium concentration of Pb(II)(mg/L), q e isthe adsorption capacity of Pb(II) on adsorbent at equilibrium state(mg/g), q m is the maximum adsorption capacity(mg/g), K L is the Langmuir binding constant, which is related to the energy of adsorption [31]. K F and n are Freundlich constants that are related to adsorption energy and adsorption intensity, respec-tively. The Langmuir isotherm is based on the assumptions that the sorption is a monolayer coverage, the surface of the absor-bent is homogenous, on which can only one adsorbed atom be accommodated, and every adsorption site has equal adsorbate affinity and is independent with its neighboring sites [32]. Freun-dlich model is an empirical equation that is applicable to highly heterogeneous surfaces [31].Fig.6 showed the Langmuir and Freundlich isotherms for the adsorption of Pb(II) ions on the rGO-Fe 3O 4 composite. The results show that the R 2 value for the adsorption of Langmuir and Freundlich isotherm models are 0.998 and 0.918, respec-tively, indicating the adsorption behavior fitted to the Langmuir isotherm model well. In addition, the value of the q max obtained from the Langmuir model has good agreement with the expe-rimental data(30.68 mg/g). The results reveal that the adsorp-tion process is mainly a monolayer adsorption, that is, aFig.6 Langmuir(A) and Freundlich(B) isothermmodels for the adsorption of Pb(II) ions on the rGO-Fe 3O 4 nanocomposite larger specific surface area would lead to a better adsorption. From the Langmuir isotherm model, the essential charac-teristics can be expressed by a separation factor, R L , which can be obtained from the following equation: L L e11R K c =+ (4)where c e is the equilibrium concentration of Pb(II)(mg/L), K L is the Langmuir binding constant, which is related to the energy of adsorption. The value of R L represents the shape of the Langmuir isotherm and the nature of the adsorption process, which is considered to be a favorable one when the value is within the range of 0―1[33]. In this work, the calculated value of the R L is in the range of 0.466―0.911, which proves that the adsorption of Pb(II) by the rGO-Fe 3O 4 composite is favorable.4 ConclusionsThe rGO-Fe 3O 4 hybrid nanocomposite was synthesized via a one-pot facile hydrothermal method. The results of the SEM, TEM and XRD characterizations of the composite show that approximately spherical Fe 3O 4 nanoparticles with about 20 nm in diameter have been deposited on the surfaces of rGO sheets. The adsorption experiments of Pb(II) ions on the rGO-Fe 3O 4 composite show that the adsorption capacity was influenced by the amount of Fe 3O 4 nanoparticles in the hybrid material, which could prevent rGO sheets from stacking. The adsorption capacity was also related to the initial concentration of Pb(II). At low concentration, adsorption capacity was proportional to the initial concentration and reached a maxi-mum value at a concentration of 80 mg/L. The maximum adsorption capacity was 30.68 mg/g, which was obtained at n (FeCl 3)/m (GO) ratio of 1:5(mmol:mg) at pH=7.0. The data fitted well with the Langmuir model. Besides, the magnetic nanocomposite after adsorbing Pb(II) ions could be easily se-parated under a magnet. The results showed that the simply prepared rGO-Fe 3O 4 hybrid nanocomposite was an effective and environment friendly absorbent in water purification.References[1] Blowes D. W., Ptacek C. J., Jambor J. L., Environ. Sci. Technol.,1997, 31(12), 3348[2] Babel S., Kurniawan T. A., J. Hazard. Mater., 2003, 97, 219[3] Gao H. N., Sun Y . M., Zhou J. J., Xu R., Duan H. W., ACS Appl.Mater. Interfaces , 2013, 5, 425[4] Fu F. L., Wang Q., J. Environ. Manag., 2011, 92, 407[5] Aguado J., Arsuaga J. M., Arencibia A., Lindo M., Gascón V ., J. Ha-zard. Mater., 2009, 163, 213[6] Gupta V . K., Carrott P. J. M., Ribeiro Carrott M. M. L., Suhas, Crit.Rev. Env. Sci. Tec., 2009, 39, 783[7] Parida S. K., Dash S., Patel S., Mishra B. K., Adv. Colloid InterfaceSci., 2006, 121, 77[8] Lin T. F., Wu J. K., Water Res., 2001, 35, 2049[9] An H. K., Park B. Y ., Kim D. S., Water Res., 2001, 35, 3551 [10] Amuda O. S., Giwa A. A., Bello I. A., Biochem. Eng. J., 2007, 36,174[11] Zhou Y ., Jiang L., Yan J. W., Wang C. L., Xiao N., Chem. J. ChineseUniversities , 2014, 35(3), 619No.4 CAO Wei et al. 513[12]Paredes J. I., Rodil S. V., Alonso A. M., Tascon J. M. D., Langmuir,2008, 24, 10560[13]Huang C. C., Bai H., Li C., Shi J. Q., Chem. Commun., 2011, 47,4962[14]Hua M., Zhang S. J., Pan B. C., Zhang W. M., Lü L., Zhang Q. X., J.Hazard. Mater., 2012, 211, 317[15]Li F., Du X. Y., Yang R. C., Chem. J. Chinese Universities, 2011,32(8), 1688[16]Zubir N. A., Yacou C., Motuzas J., Zhang X. W., Diniz da Costa J. C.,Sci. Rep., 2014, 4, 4594[17]Hummers J. W. S., Offeman R. E., J. Am. Chem. Soc., 1958, 80, 1339[18]Xu C., Wang X., Small, 2009, 5, 2212[19]Zhang W. X., Cui J. C., Tao C. A., Wu Y. G., Li Z. P., Ma L., Wen Y.Q., Li G. T., Angew. Chem. Int. Ed., 2009, 48, 5864[20]Tian Y., Yu B. B., Li X., Li K., J. Mater. Chem., 2011, 21, 2476[21]Thomas H. R., Marsden A. J., Walker M., Wilson N. R., Rourke J. P.,Angew. Chem. Int. Ed., 2014, 53, 7613[22]Chandra V., Park J., Chun Y., Lee J. W., Hwang I. C., Kim K. S., ACSNano, 2010, 4(7), 3979[23]Zhang Y., Chen B., Zhang L. M., Huang J., Chen F. H., Yang Z. P.,Yao J. L., Zhang Z. J., Nanoscale, 2011, 3, 1446 [24]Yang X., Chen C. L., Li J. X., Zhao G. X., Ren X. M., Wang X. K.,RSC Adv., 2012, 2, 8821[25]Reddad Z., Gerente C., Andres Y., Cloirec P. L., Environ. Sci. Tech-nol., 2002, 36(9), 2067[26]Abraham T. N., Kumar R., Misra R. K., Jain S. K., J. Appl. Polym.Sci., 2012, 125, 670[27]Gollavelli G., Chang C. C., Ling Y. C., ACS Sustainable Chem. Eng.,2013, 1(5), 462[28]Hua R., Li Z. K., Chem. Eng. J., 2014, 249, 189[29]Zhang C., Sui J. H., Li. J., Tang Y. L., Cai W., Chem. Eng. J., 2012,210, 45[30]Badruddoza A. Z. M., Shawon Z. B. Z., Tay D. W. J., Hidajat K.,Uddin M. S., Carbohyd. Polym., 2013, 91, 322[31]Madadrang C. J., Kim H. Y., Gao G., Wang N., Zhu J., Feng H., Gor-ring M., Kasner M. L., Hou S., ACS Appl. Mater. Interfaces, 2012, 4(3), 1186[32]Fan L. L., Luo C. N., Li X. J., Lu F. G., Qiu H. M., Sun M., J. Ha-zard. Mater., 2012, 215, 272[33]Yang Y. F., Xie Y. L., Pang L. C., Li M., Song X. H., Wen J. G., ZhaoH. Y., Langmuir, 2013, 29, 10727。