Highly Photocatalytic Activity of Novel CuFe 2 O 4 /GO Nano Composite in the Degradation of Phenol from Aqueous Solution

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1 Physicl Chemistry 217, 7(1): 8-16 DOI: /j.pc Highly Photoctlytic Activity of Novel CuFe 2 O 4 /GO Nno Composite in the Degrdtion of Phenol from Aqueous Solution Ging H. Le 1, Quyet T. Ngo 1, Tun T. Nguyen 1,2, Qung K. Nguyen 1, Trng T. T. Qun 1, Tun A. Vu 1,2,* 1 Institute of Chemistry, Vietnm Acdemy of Science nd Technology (VAST), 18 Hong Quoc Viet, Cu Giy District, Hnoi, Vietnm 2 Grdute University of Science nd Technology, Vietnm Acdemy of Science nd Technology, 18 Hong Quoc Viet, Cu Giy District, Hnoi, Vietnm Astrct The CuFe 2 O 4 /Grphene oxide (GO) composite ws successfully synthesized y co-precipittion in situ using FeCl 3.6H 2 O nd CuCl 2.2H 2 O s iron nd copper sources on GO nd followed y therml reduction. The product ws chrcterized y XRD, XPS, TEM, BET nd FTIR. From the XRD nd XPS results, it revels the formtion of copper ferrites spinel CuFe 2 O 4 on GO surfce. From TEM imges, it showed tht CuFe 2 O 4 /GO composite hs prticle size of 2-3 nm nd uniform size distriution. The s-prepred CuFe 2 O 4 /GO nno composite ws used to test the photoctlytic degrdtion of phenol from queous solution. After 9 minutes of rection, the conversion (clculted ccording COD) reched to the vlue of 9%, indicting highly photoctlytic ctivity of this ctlyst. Moreover, fter three recycles, the photoctlytic ctivity ws lmost unchnged s compred to tht of fresh ctlyst, indicting the reltively high stility nd it cn e reused. Additionlly, this CuFe 2 O 4 /GO composite showed highly mgnetic property so it cn e esily recovered y pplying the mgnetic field out side. Keywords Nnocomposite CuFe 2 O 4 /GO, Simulted sun-light irrdition, Photoctlytic phenol degrdtion 1. Introduction In recent yers, grphene sed mterils (grphene nd grphene oxide) hve received specil ttention due to its unique structure nd physicl chemicl properties s well s their utiliztion in vriety of pplictions such s electrode in tteries nd super cpcitors, conductive mtrix, support mteril nd dsorents in environment [1]. Grphene, two-dimensionl nno mteril with severl lyers of sp 2 hyridixed cron toms rrnging in six-memered rings, hs showed unique properties including, high Young s modulus (c. 11 GP), high strength (125 GPA), high therml (5 W.m -1.K -1 ) nd electricl (,96 x 1-6 W -1.m -1 ) conductivities t room temperture, high specific surfce re (theoreticl vlue 263 m 2.g -1 ) nd high chemicl stility [1, 2-c]. Due to its cn e used excellent electric conductivity nd high surfce re, grphene sed mterils s suitle mteril used s two-dimensionl pltform to ccept nd spred photogenerted electron hole pirs from semiconductor upon light irrdition, enhncing the photodegrdtion efficiency of semiconductor in * Corresponding uthor: vunhtun.vst@gmil.com (Tun A. Vu) Pulished online t Copyright 217 Scientific & Acdemic Pulishing. All Rights Reserved photodegrdtion rection [3, 4]. The spinel structured ferrites hve the generl formul MFe 2 O 4 (M: Fe, Co, Ni, Zn, Cu, etc.). The properties of the ferrite cn e vried y chnging the identity of the divlent M 2+ ction. Among the ferrites, copper ferrite nnoprticles (CuFe 2 O 4 ) hs received gret interest nd is widely used in electronics, nd ctlysis [5, 6, 7]. CuFe 2 O 4 is one of the iron-sed cuic spinel series showing dvntges of nrrow nd gp (1.9eV) for high sorption efficiency of sunlight, high photochemicl stility, nd excellent ferromgnetic properties for ctlyst recovery y pplying mgnetic field [7]. However, CuFe 2 O 4 nnomteril used s photoctlyst in the degrdtion of pollutnts is still lredy investigted. However, the CuFe 2 O 4 nnoprticles re tended to ggregte due to the ferromgnetic properties, forming lrge prticles. Moreover, ecuse of the nrrow nd-gp resulted in the rpid recomintion of electrons nd hole it cused the fst decresed of their photo ctlytic ctivity. To overcome this recent yers, different mgnetic iron oxides grphene nno composites, hve een synthesized nd it climed tht the dispersion nd ttchment of metl oxide prticles cn e improved, resulting in enhnce of photoctlytic performnce in the degrdtion of orgnic compounds s compred with metl oxide itself or pristine grphene [3, 8, 9]. The improvement of photoctlytic

2 Physicl Chemistry 217, 7(1): performnce cn e explined due to the specil ility of grphene, GO which cn ct s electron cceptor/shuttle photogenerted from metl oxide upon light irrdition. This mkes life spn of photoexcited electron- hole pirs longer, therey hindering the electron-hole recomintion nd enhncing photoctivity of mterils. Additionlly, grphene oxide hs undnt oxygented functionl groups such s hydroxyl, epoxides nd croxyl groups, esily formed the covlent ond with metl ions nd cn e more suitle to disperse CuFe 2 O 4 nno prticles on GO surfce. In this pper, we report two-step synthesis of CuFe 2 O 4 /GO composites through co-precipittion in situ nd therml reduction nd photo fenton ctivity in the degrdtion of Phenol. Effects of ph, ctlyst dosge s well s stility of the ctlysts investigted. 2. Experimentl 2.1. Synthesis of GO Grphene oxide is synthesized y chemicl oxidtion nd exfolition of nturl grphite using modified Hummers method [1]. GO powders were exfolited y the tretment in microwve oven (Model MWO-G2SA) in mient conditions t 7 W for one minute [11]. Upon microwve irrdition, the volume expnsion of the GO powders much is lrger thn the exfolited y using the common method (ultrsonic tretment) 2.2. Synthesis of Fe 3 O 4 /GO Nno Composite Mgnetic iron oxide - grphene oxide composites (Fe 3 O 4 /GO) were prepred y co-precipittion using FeCl 3.6H 2 O nd FeCl 2.4H 2 O s ion-contining sources nd deposited on GO surfce. Suspension of GO ws diluted with distilled wter under vigorous stirring. After tht, the mixture of FeCl 3 nd FeCl 2 (rtio Fe 3+ /Fe 2+ :2/1) ws slowly dded to the GO mixture. The mixture ws djusted solution ph vlue y dding 15 ml NH 4 OH 3% to rech the ph vlue of 1. The otined gels were mintined t 8 C for 45 minute. The product ws repetedly wshed y distilltion wter nd ethnol until ph vlue of 7. The finl product ws dried in vcuum oven t 6 C efore use. The rtio of mgnetite to GO (in weight) is 1: Synthesis of CuFe 2 O 4 /GO Nno Composite Nnocomposite CuFe 2 O 4 /GO ws synthesized y co-precipittion in situ using FeCl 3.6H 2 O nd CuCl 2.2H 2 O s iron nd copper sources on GO nd followed y the therml reduction. Firstly, 225 mg GO ws dded into 11 ml of distilled wter, ethnol solution mixture ws treted in ultrsonic ch for 3 minute. After tht, 53.5 mg of CuCl 2.2H 2 O nd mg of FeCl 3.6H 2 O were dded to 11 ml of distilled wter nd ethnol under stirring condition for 15 min. t room temperture. The ove two mixtures were put together nd stirred for 3 min. After tht, the mixture ws djusted to ph vlue of 1 y dding 15 ml NH 4 OH 3% solution nd stirred for 3 h. The otined products were repetedly wshed y distilltion wter until ph of 7 nd then freeze dried. Finlly, the otined product ws clcined y heting t 65 C for 2 h in nitrogen tmosphere. The rtio of CuFe 2 O 4 /GO (in weight %) is 1: Chrcteriztion The powder X-ry diffrction (XRD) ptterns of the smples were recorded on Shimdzu XRD-61 nlyzer with Cu K rdition (l¼ A). Trnsmission electron microscopy (TEM) using JEOL 11 instrument operting t 8 kv with mgnifiction of 25, 1,. The X-ry photoelectron spectroscopy (XPS) mesurement ws performed on the ESCAL MKII spectrometer using Mg K α rdition. A virting-smple mgnetometer (VSM, PPMS6, Quntum Design) ws used to study the mgnetic properties of mgnetite nno prticles. The FT-IR spectr of the smples were mesured y the KBr pellet method (BIO-RAD FTS-3). Surfce Are of smples ws determined on Quntchrome Instruments version 3. t 77 K nd using nitrogen dsored. Energy-dispersive X-ry spectroscopy (EDX) of smples were mesured using JEOL JED-23 spectrometer Photo-Fenton Rection Pyrex glss ottles, in which 1 ml liquot of ech phenol solution with initil concentrtions of 1 mg/l ws dded. Photoctlytic degrdtion of phenol from queous solution ws crried out in ch rector t the following conditions: photoctlyst conc. of g/l nd H 2 O 2 conc. of 136 mg/l. Photo-Fenton rection of phenol ws performed under stirring condition, t room temperture nd ph in the rnge of The ph vlue of rectnt solution ws djusted with HCl.1 M or NOH.1 M solution. The smples were collected t diffirent rection time. Simulted sunlight source ws used UV-A rnge lmps (4 lmps, power of 15W for ech lmp). The emission spectrum etween 4 nd 8 nm follows the solr spectrum. Before strting the illumintion,ech rection mixture ws stirred for 25 minute in the drk in order to rech the dsorption desorption equilirium etween the phenol nd the ctlysts. Concentrtions of phenol nd the intermedites formed the processes were determined y using high performnce liquid chromtogrphy (HPLC Agilent 11) with detector DAD (Agilent - US). The ssessment of the photodegrdtion ws lso exmined y chemicl oxygen demnd (COD). The COD ws mesured y potssium dichromte titrimetric method y using Lmd 35 UV-vis spectrophotometer intensities of the nd t 61 nm. The COD removl efficiency (H %) ws clculted s following eqution: CODo CODt COD removl efficiency H% x1 COD o

3 1 Ging H. Le et l.: Highly Photoctlytic Activity of Novel CuFe 2 O 4 /GO Nno Composite in the Degrdtion of Phenol from Aqueous Solution Where COD o is the COD initil of phenol nd COD t is the COD fter the different time. 3. Results nd Discussion 3.1. X-ry Diffrction (XRD) nd Fourier Trnsform Infrred Spectroscopy (FTIR) Anlysis The X-ry diffrction pttern of the CuFe 2 O 4 /GO composite ws shown in Fig. 1. The diffrction peks (3.1, 35.4, 43.3, 57.2, 62.7 ) of CuFe 2 O 4 /GO corresponded to the (22), (311), (4), (511), (44) plnr of fce-centered cuic structure of CuFe 2 O 4 s reported in the literture [8, 12]. The sence of the pek t 2θ of 11 (fig. 1) which is chrcteristic for GO structure, indicted the intercltion of CuFe 2 O 4 nnoprticles within GO lyers. Additionlly, nno CuFe 2 O 4 prticles generted on the GO surfce prevent the restcking of GO sheets to form regulr nd periodic lyered structure of grphite [13]. However, no typicl pek of grphene t 2θ of 23-26,3 ws oserved, suggesting tht the grphene sheets were exfolited [14]. The FTIR spectrum of CuFe 2 O 4 /GO ws presented in Fig. 1c. The nd t 3419 cm 1 is ttriuted to the stretching virtion of O H. Strong nds in the region of cm -1 correspond to the C=C stretching virtion, the C O H deformtion virtion, respectively. The nd with low intensity t 2342 cm -1 ssigned to CO 2 GO ending virtions [15]. The new nds t 53 cm 1 nd 437 cm -1, ppered indicting the interction etween CuFe 2 O 4 nd the grphene oxide sheets through metl-cronyl coordintion [8] Trnsmission Electron Microscopy (TEM) nd Energy-dispersive X-ry Spectroscopy (EDX) Anlyses The imge of CuFe 2 O 4 ws shown in Fig. 2. As oserved in Fig. 2 CuFe 2 O 4 nnoprticles nchored on GO sheets nd reltively well distriuted. It could e noted in Fig.2 tht the size of the CuFe 2 O 4 on GO ws round 2 3 nm with reltively nrrow size distriution nd certin extent of prticles ggregtion. The elementl composition of the hyrid ws exmined y EDX spectroscopy nd the results were present in Fig. 2. From nlysis result, it shows tht CuFe 2 O 4 /GO contined 43.79% C in weight, 27.51% O in weight, 22.87% Fe in weight nd 5.84% Cu in weight, while the Fe 3 O 4 /GO contined 4.89% C in weight, 34.75% O in weight nd 24.2% Fe in weight, respectively. This reveled tht CuFe 2 O 4 nd Fe 3 O 4 hve the similr composition. 6 Fculty of Chemistry, HUS, VNU, D8 ADVANCE-Bruker - Smple CuFe2O4-EG 5 4 d=2.487 Lin (Cps) 3 d=2.981 d=2.591 d=2.417 d=2.183 d=2.53 d=1.663 d=1.584 d=1.491 d= Thet - Scle File: Cnh VH mu CuFe2O4-EG.rw - Type: 2Th/Th locked - Strt: 2. - End: Step:.3 - Step time: 1. s - Temp.: 25 C (Room) - Time Strted: 12 s - 2-Thet: 2. - Thet: ) Left Angle: Right Angle: Left Int.: 251 Cps - Right Int.: 239 Cps - Os. Mx: d (Os. Mx): Mx Int.: 385 Cps - Net Height: 141 Cps - FWHM:.26 - Chord Mid.: 36 c Figure 1. XRD ptterns of CuFe 2 O 4 /GO (); GO () nd (c) FT-IR spectr of CuFe 2 O 4 /GO

4 Mgnetiztion (emu/g) Physicl Chemistry 217, 7(1): Elements C O Fe Cu CuFe 2 O 4 /GO (wt %) Fe 3 O 4 /GO (wt %) Figure 2. TEM imges () nd EDX spectr () of CuFe 2 O 4 /GO 4 3 CuFe2O4/GO Applied mgnetic field (Oc) Figure 3. Mgnetiztion curve of CuFe 2 O 4 /GO Figure 4. N 2 dsorption desorption isotherms of CuFe 2 O 4 /GO () nd GO () 3.3. Mgnetiztion of CuFe 2 O 4 /GO Fig. 3 shows the mgnetiztion hysteresis loop of the the CuFe 2 O 4 /GO nnostructures. The mgnetic hysteresis loops were Slike curves. The results showed no remnence or coercivity in the hyrids suggesting tht there ws no remining mgnetiztion when externl mgnetic field ws removed nd the mgnetic composites were

5 12 Ging H. Le et l.: Highly Photoctlytic Activity of Novel CuFe 2 O 4 /GO Nno Composite in the Degrdtion of Phenol from Aqueous Solution superprmgnetic. The sturted mgnetiztion of the superprmgnetic ws nerly 35 emu/g which gurnteed ctlyst seprtion y pplying mgnetic field out side N 2 Adsorption Desorption Isotherms (BET) Anlysis N 2 dsorption desorption isotherms of CuFe 2 O 4 /GO composites nd GO re shown in figure 4. The N 2 dsorption-desorption curve of CuFe 2 O 4 /GO composites displyed type IV with hysteresis corresponding to the cpillry condenstion which is typicl for mesoporous mteril [16]. Thus, mesopore volume of composite rech 99% of totl pore volume (.524 cm 3 /g). This indictes tht in the pore distriution, micropore volume is only minor. The pore texture prmeters nd surfce re were listed in tle 1. CuFe 2 O 4 /GO composites nd GO hd pore dimeter of 8.8 to 21 nm nd surfce re of 183 m 2 /g nd 331 m 2 /g, respectively. Note tht GO hs min contriution of mesopore volume lger surfce. CuFe 2 O 4 /GO prticles were well dispersed on GO surfce nd consequently prticles size is smller (i.e surfce re of prticles is higher) due to the suppressing prticles ggregtion. However, the deposition nd intercltion of CuFe 2 O 4 prticles within GO lyers cused the decrese of surfce re nd pore volume s compred to tht of the pure GO. Tle 1. Textul chrcteristics of CuFe 2 O 4 /GO nd GO Smples Specific surfce re S BET (m²/g) Micro-pore volume (cm 3 /g) Totl pores Volume (cm³/g) Pore dimeter (nm) CuFe 2 O 4 /GO GO The X-ry Photoelectron Spectroscopy (XPS) Anlysis XPS spectr of CuFe 2 O 4 /GO were show in fig. 5. c d Figure 5. XPS spectr of CuFe 2 O 4 /GO

6 COD removl (%) COD removl H(%) Physicl Chemistry 217, 7(1): The widely scn of the CuFe 2 O 4 /GO showed photoelectron lines t inding energy of 285 ev, 53 ev, nd 711 ev correspond to the C1s, O1s, nd Fe2p, respectively (Fig. 5). The deconvolution of the C1s pek ws consisted of three peks t ev, ev nd ev, which were scried to the C-C, C-O, nd C(O)O in GO sheets. In the cse of XPS spectr of C1s, the pek ppered t 291 ev ws ssigned to the π-π * ond of rgo, GO [17]. Additionly the pek t 291 ev is ttriuted to the onding stte etween electron pirs nd holes in GO nd rgo structures [18]. The inding energy of Fe2p 3/2 of the hyrid ws locted t 711 ev while the pek of Fe2p 1/2 ppered t 725 ev. As oeserved in figure 5d, no pek t 932 ev nd 941 ev which re chrcteristic for individul existence of Cu + nd Cu 2+ indicted tht no copper oxides were seprtely formed. The high-resolution XPS spectr of Cu2p nd Fe2p (Figure 5c,d) indicted tht oxidtion stte of Cu nd Fe eing Cu 2+ nd Fe 3+, respectively in the CuFe 2 O 4 nnocomposite [19] Photoctlytic Activity / Effect of ctlyst dosge ,6 Figure 6. Effect of ctlyst concentrtion on degrdtion of phenol, [Phenol] = 1 mg/l, [H 2 O 2 ]= 136 mg/l ph = 3; T = 33 K The effect of different of ctlyst concentrtions on phenol degrdtion CuFe 2 O 4 /GO is shown in Fig. 6. The removl efficiency increses from 5.6% to 9.4% with incresing of CuFe 2 O 4 /GO concentrtion from.5 g/l to.3 g/l. However, no significnt difference in removl of phenol y further incresing concentrtion of CuFe 2 O 4 /GO from.1 to.3 g/l ws oserved. As expected, the mount of ctive sites on CuFe 2 O 4 /GO rose with incresing dosge of ctlyst, which promoted the genertion of rdicls, nd the higher rection rte is chieved. This cn e explined tht OH. rdicls decomposed more rpidly, ut the rection occurred not rpid enough to consume the OH. rdicls generted [9]. Therefore, the use of higher ctlyst concentrtion of.1 g/l is not necessry. / Effect of ph 74,7 9,2 89,9 9,1 9,4,5,7,1,15,2,3 Ctlytic dosge (g/l) As seen from Fig. 7, ph hs n importnt influence on the degrdtion of phenol due to its role in controlling the ctivity of the oxidnt gents nd the sustrtes, the domintion of iron species, nd the stility of hydrogen peroxide. The COD removl efficiency of phenol degrdtion over Fe 3 O 4 /GO ws lmost 62% t ph vlue of 3, when ph of phenol solution incresed to higher thn 5, the COD removl efficiency ws less thn 2%. While, the initil ph vlue difference hrdly ffects on the degrdtions of Phenol on CuFe 2 O 4 /GO. The optimum ph ws found to e 3, where the rte of the rection is the fstest. This cn e rtionlized tht ph incresed ove 5, the rection rte decresed shrply possily due to the formtion of inctive ferryl ion FeO 2+ (the lower oxidtion potentil of hydroxyl rdicls), cusing the dectivtion of ctlyst [8, 2] ph Figure 7. Influence of ph vlues on phenol degrdtion over Fe 3 O 4 /GO nd CuFe 2 O 4 /GO composites c/ Photo-Fenton degrdtion CuFe2O4/GO Fe3O4/GO In this study, the ctlytic ctivities of two smples were tested under different rection conditions re presented in Fig. 8. The experiments were crried out t: ph: 3, H 2 O 2 concentrtion: 136 mg/l, ctlyst dosge:.1 g/l, Phenol initil concentrtion: 1 mg/l. From Figure 8, it is oserved tht fter 9 minutes of rection under the simulted sunlight irrdition, the conversion (clculted ccording COD) reched 9% for CuFe 2 O 4 /GO nd 62% for ctlyst Fe 3 O 4 /GO. To figure out the difference in photo-fenton nd fenton ctivity, phenol degrdtion of CuFe 2 O 4 /GO ws investigted. Under the sme rection conditions ut no light irrdition, the conversion reched to the vlue of 75%. Photoctlytic ctivity on phenol degrdtion over CuFe 2 O 4 /GO higher thn Fe 3 O 4 /GO cn e explined s follows: the iron oxide Fe 3 O 4 with the nd gp energy of ev, GO sustrte contriutes to the electron trnsfer from the conduction nd of the semiconductor, limited recomintion electrons nd holes. For CuFe 2 O 4, due to the electronics configurtion chnges the nd gp energy of ev is smller thn tht of Fe 3 O 4 incresing the ility to generte OH rdicls. Moreover, the presence of Cu ion in CuFe 2 O 4 cn reduce Fe 3+ to Fe 2+ ion which incresed OH. rdicl genertion, leding to increse the photo-fenton rection rte [21, 22].

7 COD removl efficiency (%) COD removl (%) mau 14 Ging H. Le et l.: Highly Photoctlytic Activity of Novel CuFe 2 O 4 /GO Nno Composite in the Degrdtion of Phenol from Aqueous Solution 1 Fe3O4/GO Photo-Fenton rection 2 Phenol 1 mg/l 8 CuFe2O4/GO Fenton rection CuFe2O4/GO Photo-Fenton rection cid croxylic Time (min.) 5 Fe3O4/GO - Phenol fter 9 min. 25 CuFe2O4/GO -Phenol fter 9 min Time (min.) Figure 8. () Comprison of the photoctlytic degrdtion of phenol solution under different conditions. () HPLC digrm of phenol degrdtion over CuFe 2 O 4 /GO 1 1st run 2nd run 3rd run Irrdition time (min) Figure 9. The cycling runs of phenol degrdtion over CuFe 2 O 4 /GO composite under simulted solr irrdition, experimentl conditions: [Phenol] = 1 mg/l, [H 2 O 2 ] = 136 mg/l, ctlyst dosge =.1 g/l, ph = 3, T= 33K Figure 8 showed tht fter 9 minutes, lmost phenol ws converted to CO 2 nd H 2 O. HPLC digrm of CuFe 2 O 4 /GO showed the only single intermedite compound with very low intensity (retention time RT of 1.5 minutes). These intermedites my e croxylic with short cron chin [23-25]. Such ctlysts CuFe 2 O 4 /GO is highly ctive in the decomposition of phenol in phenolic concentrtion conditions first 1 mg/l, the concentrtion of ctlyst.1 g/l, H 2 O 2 concentrtion 136 mg/l, ph vlue of 3 using lights simulte irrdition. d/ Stility of CuFe2O4/GO composite In ech test, the photoctlyst ws seprted from the equilirium solution y mgnet, wshed with enthnol, nd vcuum dried t 6 o C for 6 h. As oserved in fig. 9, fter the first regenertion cycle, the COD removl efficiency ws 9 %. After the third cycle, the COD removl efficiency of CuFe 2 O 4 /GO ws 84 %. The decrese of ctlyst ctivity my e due to the CuFe 2 O 4 leching into the solution nd/or incomplete desorption of sustrtes from the ctlyst surfce. However, fter the third rection run, ctlytic ctivity decresed due to its mgnetic property. Moreover, it cn e esily cn e recovered due to its mgnetic property. 4. Conclusions CuFe 2 O 4 /GO composite ws successfully synthesized y co-precipittion in situ using FeCl 3.6H 2 O nd CuCl 2.2H 2 O s iron nd copper sources on GO nd followed y therml reduction. From the XRD, XPS results, it reveled the formtion of spinel CuFe 2 O 4 on GO surfce. From TEM imges, it showed tht CuFe 2 O 4 composite hs prticle size of 2-3 nm nd uniform size distriution. CuFe 2 O 4 /GO composite exhiited high photo fenton ctivity (COD removl 9% fter 9 min. rection). The high ctlytic ctivity of present nno CuFe 2 O 4 prticles cn e scried to high ctlytic surfce re (due to smll sized CuFe 2 O 4 nd GO sheets),

8 Physicl Chemistry 217, 7(1): excellent synergistic coupling of Cu/Fe species nd presence of grphene sheets which holds the orgnic species y π π interctions. Additionlly, this CuFe 2 O 4 /GO composite showed high mgnetism so it cn e esy recovered y pplying the mgnetic field out side. ACKNOWLEDGMENTS The uthors thnks the Institute of Chemistry nd Vietnm Acdemy of Science nd Technology -VAST for finncil support. REFERENCES [1] Shmik Chowdhury, Rjsekhr Blsurmnin, 214, Recent dvnces in the use of grphene-fmily nnodsorents for removl of toxic pollutnts from wstewter, Advnces in Colloid nd Interfce Science, 24, 35. [2] / Ro CN, Sood AK, Surhmnym KS, Govindrj A., 29, Grphene: the new two-dimensionl nnomteri, Angew Chem Int Ed., 48, / A. K. Geim & K. S. Novoselov, 27, The rise of grphene, Nture Mterils, 6, c/ Sungjin Prk & Rodney S. Ruoff, 29, Chemicl methods for the production of grphenes, Nture Nnotechnology 4, [3] Rvi Knt Updhyy, Nvneet Soin nd Susnt Sinh Roy, 214, Role of grphene/metl oxide composites s photoctlysts, dsorents nd disinfectnts in wter tretment: review, RSC Adv., 4, [4] Xinjun Liu, Likun Pn, Qingfei Zho, Tin Lv, Gung Zhu, Tiqing Chen, Ting Lu, Zhuo Sun, Chngqing Sun, 212, UV-ssisted photoctlytic synthesis of ZnO reduced grphene oxide composites with enhnced photoctlytic ctivity in reduction of Cr(VI), Chemicl Engineering Journl, 183, [5] Jie Feng, Li Su, Ynhu M, Cuiling Ren, Qing Guo, Xingguo Chen, 213, CuFe 2 O 4 mgnetic nnoprticles: A simple nd efficient ctlyst for the reduction of nitrophenol, Chemicl Engineering Journl, 221(1), [6] Yong Feng, Chngzhong Lio, Kimin Shih, 216, Copper-promoted circumneutrl ctivtion of H 2 O 2 y mgnetic CuFe 2 O 4 spinel nnoprticles: Mechnism, stoichiometric efficiency, nd pthwy of degrding sulfnilmide, Chemosphere, 154, [7] Chin Kui Cheng&Zi Ying Kong&Mksudur R. Khn, 215, Photoctlytic-Fenton Degrdtion of Glycerol Solution over Visile Light-Responsive CuFe 2 O 4, Wter Air Soil Pollut., 226, 327. [8] Peng Chen, Xing Xing, Huifng Xie, Qi Sheng, Hongxi Qu, 216, High ctlytic ctivity of mgnetic CuFe 2 O 4 /grphene oxide composite for the degrdtion of orgnic dyes under visile light irrdition, Chemicl Physics Letters, 66, [9] Yito Zho, Gungyu He, Wen Di, nd Hiqun Chen, 214, High Ctlytic Activity in the Phenol Hydroxyltion of Mgneticlly Seprle CuFe 2 O 4 Reduced Grphene Oxide, Ind. Eng. Chem. Res., 53(32), [1] W.S. Hummers Jr., R.E. Offermn, 1958, Preprtion of grphitic oxide, J. Am. Chem. Soc., 8, [11] Ynwu Zhu, Shnthi Murli, Meryl D. Stoller, Arun Velmknni, Richrd D. Piner, Rodney S. Ruoff, 21. Microwve ssisted exfolition nd reduction of grphite oxide for ultrcpcitors, Cron, 48(7), [12] M Kngrj, P Sthishkumr,G Kli Selvn, I Phee Kokil & S Arumugm, 214, Structurl nd mgnetic properties of CuFe 2 O 4 s-prepred nd thermlly treted spinel nnoferrites, Indin Journl of Pure & Applied Physics, 52, [13] X.D. Hung, X.F. Zhou, K. Qin, D.Y. Zho, Z.P. Liu, C.Z. Yu, 212, A mgnetite nnocrystl/grphene composite s high performnce node for lithium-ion tteries, J. Alloys Compd., 514, [14] Li D, Muller MB, Gilje S, Kner RB, Wllce GG, 28, Processle queous dispersions of grphene nnosheets, Nt Nnotechnol., 3, [15] Rjsekhr Blsurmnin nd Shmik Chowdhury, 215, Recent dvnces nd progress in the development of grphene-sed dsorents for CO 2 cpture, J. Mter. Chem. A, 3, [16] Bo Yng, Zhng Tin, Li Zhng, Yopeng Guo, Shiqing Yn, 215, Enhnced heterogeneous Fenton degrdtion of Methylene Blue y nnoscle zero vlent iron (nzvi) ssemled on mgnetic Fe 3 O 4 /reduced grphene oxide, Journl of Wter Process Engineering, 5, [17] Jeongho Prk, Tyson Bck, Willim C. Mitchel, Steve S. Kim, Sid Elhmri, John Boeckl, Steven B. Firchild,Rjesh Nik, nd Andrey A. Voevodin, 215, Approch to multifunctionl device pltform with epitxil grphene on trnsition metl oxide, Sci Rep., 5, [18] Crl Bittencourt, Adm P Hitchock, Xioxing Ke, Gustf Vn Tendeloo, Chris P Ewels, nd Peter Guttmnn, Guttmnn, 212, X-ry sorption spectroscopy y full-field X-ry microscopy of thin grphite flke: Imging nd electronic structure vi the cron K-edge, Beilstein J Nnotechnol., 3, [19] Nedkov, I., Vndenerghe, R. E., Mrinov, T., Thilhdes, Ph., Merodiisk, T., Avrmov, I., 26, Mgnetic structure nd collective Jhn Teller distortions in nnostructured prticles of CuFe 2 O 4, Appl. Surf. Sci., 253, [2] Avik De, Asim K. De, Gouri Snkr Pnd & Sndip Hldr, 216, Synthesis of iron-sed nnoprticles nd comprison of their ctlytic ctivity for degrdtion of phenolic wste wter in smll-scle tch rector, Deslintion nd WterTretmen, 57(52), [21] Nguyen Tri Kho, Soon Wook Kim, Don Vn Thun, Huynh Ngoc Tien, Seung Hyun Hur, Eui Jung Kim nd Sung Hong Hhn, 215, Fst nd effective electron trnsport in Au grphene ZnO hyrid for enhnced photocurrent nd photoctlysis, RSC Adv., 5, [22] Ritu Dhnd nd Mzhir Kidwi, 216, Mgneticlly

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