1、文章编号:摇 1007鄄8827(2019)06鄄0539鄄07自组装 CoMn2O3. 5鄄RGO 微米立方体类 Fenton 催化剂及其染料降解性能曲江英,摇 于志强,摇 臧云浩,摇 顾建峰,摇 金具涛,摇 高摇 峰(东莞理工学院 生态环境与建筑学院, 广东 东莞 523808)摘摇 要:摇 采用水热法及热处理技术制备得到 CoMn2O3. 5鄄石墨烯(CoMn2O3. 5鄄RGO)复合材料,其中尺寸为 300 nm 左右的CoMn2O3. 5自组装成 2 滋m 左右的立方体结构并镶嵌在石墨烯片层间。 所得 CoMn2O3. 5鄄RGO 复合物作为类 Fenton 催化剂对亚甲基蓝(MB)
2、、罗丹明 B (RhB) 和二号橙(OGII)等多种染料均展现了良好的降解性能。 在 5 mg CoMn2O3. 5鄄RGO 催化剂的作用下,10 mL 50 mg L-1的上述染料分别在50、70、80 min 内完全降解。 这种降解功效主要归功于 RGO 中 仔鄄仔 共轭结构对染料的强烈吸附和纳米 CoMn2O3. 5高效催化协同作用。关键词: 摇 石墨烯; CoMn2O3. 5; Fenton 催化剂; 染料降解中图分类号: 摇 TB33文献标识码: 摇 A基金项目:国家自然科学基金(U1610114);东莞理工学院科研启动专项经费(GB200902鄄31, GC300501鄄072).
3、通讯作者:高摇 峰,副教授. E鄄mail: fenggao2003163. com作者简介:曲江英,博士. E鄄mail: qujianggaofeng163. comA CoMn2O3. 5鄄RGO hybrid as an effective Fenton鄄likecatalyst for the decomposition of various dyesQU Jiang鄄ying,摇 YU Zhi鄄qiang,摇 ZANG Yun鄄hao,摇 GU Jian鄄feng,摇 JIN Ju鄄tao,摇 GAO Feng(School of Environment and Civil Eng
4、ineering, Dongguan University of Technology, Dongguan523808, China)Abstract: 摇 A reduced graphene oxide (RGO)鄄supported CoMn2O3. 5composite (CoMn2O3. 5鄄RGO) was synthesized by a copre鄄cipitation method in a GO suspension using Co(NO3)2 6H2O and MnSO4H2O as Co and Mn sources, respectively, followed b
5、yheat treatment at 600 益 for 0. 5 h. Results indicate that CoMn2O3. 5particles with an average diameter of about 300 nm decorated theRGO sheets and self鄄organized into microcubes. The CoMn2O3. 5鄄RGO as a Fenton鄄like catalyst exhibited the high activities for thedecomposition of various dyes includin
6、g methylene blue (MB), rhodamine B (RhB) and golden orange II (OGII). 10 mL solu鄄tions of the OGII, MB and RhB dyes (50 mg L-1) are 100% decolorized with 5 mg of the CoMn2O3. 5鄄RGO in 50, 70 and 80 min,respectively. The high activity of the catalyst is closely related to a synergistic effect of RGO
7、and CoMn2O3. 5, where the dyes areadsorbed on the surface of RGO by鄄interaction and retained in close proximity to the active sites of CoMn2O3. 5.Key words:摇 Graphene; CoMn2O3. 5; Fenton鄄like catalyst; Dye decompositionReceived date: 2019鄄10鄄01;摇 Revised date: 2019鄄12鄄03Foundation item: National Nat
8、ural Science Foundation of China (U1610114); Start鄄up Scientific Research Foundation in DongguanUniversity of Technology (GB200902鄄31, GC300501鄄072).Corresponding author: GAO Feng, Associate Professor. E鄄mail: fenggao2003163. comAuthor introduction: QU Jiang鄄ying, Ph. D. E鄄mail: qujianggaofeng163. c
9、omEnglish edition available online ScienceDirect (http:蛐蛐www. sciencedirect. com蛐science蛐journal蛐18725805).DOI: 10. 1016/ S1872鄄5805(19)60030鄄21摇 IntroductionThe pollution of water resources by the organicdyes as the serious environmental problem has attrac鄄ted much attention1鄄5. Fenton爷s reagent (H
10、2O2/ Fe2+or Fe3+) with the low cost and environmental benigni鄄ty is reported to be a potential method for the treat鄄ment of wastewater containing non鄄biodegradable or鄄ganic pollutants6. However, Fenton process usuallysuffers several drawbacks including the limited pHrange (pH = 2-3), the difficulty
11、of recovering ironafter the catalytic treatment, and the catalyst deactiva鄄tion by some iron complexing agents7. To overcomethese drawbacks, several studies have been made tofind efficient heterogeneous systems such as FeOx,MnOx, and MMnOx(M = metal) for the degradation摇第 34 卷摇 第 6 期2019 年 12 月新摇 型摇
12、 炭摇 材摇 料NEW CARBON MATERIALSVol. 34摇 No. 6Dec. 2019摇of the organic dyes mainly because of their great bio鄄compatibility and low cost1,8,9. For example, ourgroup found that both MnO2and Mn3O4were goodFenton鄄like catalysts for the decomposition of methyl鄄ene blue (MB)9,10. Yang reported MnFe2O4with ap
13、ore flake structure for the effective removal of MBand Congo red in single and binary dye systems7. Inspite of these efforts, numerous reported heterogene鄄ous Fenton鄄like catalysts are commonly dye鄄selec鄄tive12鄄14, and new catalysts need to be found to effi鄄ciently degrade different kinds of dyes.As
14、 we all know, the synthesis of heterogeneousFenton鄄like catalysts often causes their aggregation insolutions, which has negative effects on their catalyticperformance15. Alternatively, an appropriate sur鄄factant plays a highly significant role in preventing theaggregation of the catalysts16.Graphene
15、 oxide(GO) produced by the modified Hummers method isan amphiphile with hydrophilic edges and a hydropho鄄bic basal plane, which can act as the surfactant for theorganization of functional nanomaterials17. Further鄄more, the reduced GO (RGO) with a giant 仔鄄conju鄄gation system and 2D planar structure h
16、as good ad鄄sorption performance for dyes in solutions by promo鄄ting electron transfer during the catalytic reaction14.In this field, graphene鄄based catalysts show highercatalytic activities in comparison with bare Fenton鄄likecatalysts9,10,19, which can prevent the aggregation ofmetal oxide nanoparti
17、cles efficiently, thus increase thenumber of their active sites.Herein, we present an easy and general methodto prepareaCoMn2O3. 5鄄RGO compositecatalystusing the hydrothermal reaction followed by the heattreatment in the presence of GO.The obtainedCoMn2O3. 5鄄RGO composite catalyst has a great po鄄ten
18、tial for effective decomposition of several organiccontaminants in water.2摇 Experimental2. 1摇 Preparation of CoMn2O3. 5鄄RGO compositesGO was synthesized by the modified Hummersmethod according to our previous work9,10. All rea鄄gents used were of analytical grade. Firstly, 50 mg ofGO was dissolved in
19、 42 mL of distilled water, fol鄄lowed by adding 20 mL of the mixture aqueous solu鄄tion of 120. 7 mg of Co(NO3)2 6H2O and 140 mg ofMnSO4 H2O in water. Next, 20 mL of the 82. 55 mgmL鄄1(NH4)2SO4solution and 88 mL of the 12. 5 mgmL鄄1NH4HCO3solution were successively added intothe above system. The whole
20、process was conductedunder vigorous stirring. Finally, the mixed solutionwas heated at 50 益 for 9 h, and the black precipitatewas collected by filtration, washed thoroughly withdistilled water, and dried at 60 益. The as鄄synthe鄄sized precipitate was further heated from room tem鄄perature to 600 益 with
21、 a temperate ramp of 4 益min鄄1and kept at 600 益 for 0. 5 h in nitrogen atmos鄄phere. The black powder named as the CoMn2O3. 5鄄RGO composite was harvested and used as the catalystfor the degradation of several dyes.2. 2 摇Characterization and analysis of hydroxylradical ( OH)The measurement of OH was ca
22、rried out by thesimilar procedure as described in references20,21.Typically, 5 mg of the as鄄synthesized catalyst wasdispersed in a 50 mL aqueous solution containing 5伊10鄄4mol L鄄1of terephthalic acid (TA) and 2 伊10鄄3mol L鄄1of NaOH. Subsequently, 5 mL of 30 wt%H2O2solution was added. The reactions wer
23、e per鄄formed under continuous stirring at room temperature.A sample (5 mL) was removed in a 5 min interval,and the catalyst was separated from the solution withcentrifugation. The remaining clear liquid was usedfor fluorescence spectrum measurements. Photolumi鄄nescence (PL) spectra of generated 2鄄hy
24、droxytereph鄄thalic acid were measured at 446 nm excited by 325nm light.2. 3摇 Test of the catalytic activityThecatalyticperformancesofas鄄synthesizedCoMn2O3. 5鄄RGO composite for the degradation ofseveral dyes including methylene blue (MB), rhoda鄄mine B (RhB) and golden orange II (OGII) wereevaluated a
25、nd compared with that of CoMn2O3. 5parti鄄cles as the reference. The catalytic reaction was per鄄formed in a 50 mL glass beaker, which contained10 mL of a 50 mg L鄄1dye solution, 5 mg of the cata鄄lyst and 5 mL of a 30 wt% H2O2solution. The mix鄄ture was allowed to react under continuous stirring atroom
26、temperature. For a given time interval, 4 mL ofthe mixture solution was centrifuged at 7 000 r/ minfor 2 min to get a supernatant liquid, leaving the cata鄄lysts as the precipitate. The dye concentration was de鄄termined by the peak intensity at 485 nm for OGII,664 nm for MB and 554 nm for RhB by UV鄄v
27、is spec鄄troscopy.2. 4摇 Characterization and analysis of the samplesThe morphologies and structures of the sampleswere examined using a field emission scanning elec鄄tron microscopy (SEM, Hitachi Ltd SU8010), pow鄄der X鄄ray diffraction (XRD, a Rigaku D/ max鄄2 500diffractometer with Cu K琢 radiation), X鄄
28、ray photoe鄄lectron spectroscopy (XPS, a Thermo VG ScientificSigma Probe spectrometer), thermogravimetric analy鄄ses (TGA, a Perkin鄄Elmer Diamond TG analyzer),UV鄄vis spectroscopy (a Shimazu UV鄄3 150 spectro鄄045摇新摇 型摇 炭摇 材摇 料第 34 卷scope), inductively coupled plasma emission spec鄄troscopy (ICP, Perkin E
29、lmer, an Optima 2 000DV),and photoluminescence spectra (PL, Hitachi, a F鄄7000 fluorescence spectro photometer). The Brunau鄄er鄄Emmett鄄Teller (BET) surface area of the sampleswas determined by physisorption of N2at 77 K using aMicromeritics ASAP 2020 analyzer.3摇 Results and discussionX鄄ray diffraction
30、 (XRD) was used to identifythe crystalline properties of theCoMn2O3. 5鄄RGOcompositeascomparedwiththatofindividualCoMn2O3. 5, as shown in Fig. 1a. It is observed thatthe CoMn2O3. 5is consisted of two kinds of phases,MnO and MnCo2O4. The diffraction peaks of (111),(200), (220), (311),(222) can be assi
31、gned toMnO ( JCPDS Card No.07鄄0230 ) and ( 311 ),(400) to MnCo2O4(JCPDS Card No. 23鄄1 237) .The MnO/ MnCo2O4ratio determined by ICP analysisis 3 颐1, which agrees well with the theoretical valueand TGA analysis (Fig. 3a). The diffraction peak ofthe CoMn2O3. 5鄄RGO composite is similar with that ofthe
32、CoMn2O3. 5.Fig. 1摇 (a) XRD patterns of bare CoMn2O3. 5andthe CoMn2O3. 5鄄RGO composite.Fig. 2摇 (a) SEM and (b) high magnified SEM images of the CoMn2O3. 5鄄RGO composite, the inset exhibits the cracked part.(c) SEM image of the CoMn2O3. 5synthesized in the absence of GO.摇摇The morphologies of the as鄄ma
33、de CoMn2O3. 5鄄RGO composite and bare CoMn2O3. 5were observedby the typical SEM images (Fig. 2a鄄c). It is ob鄄served that the CoMn2O3. 5鄄RGO composite is self鄄or鄄ganized into uniform microcubes with the size ofabout 2 滋m. Each CoMn2O3. 5microcube is composedof numerous particles with the size of 300 n
34、m (Fig.2a insert image), and the cracked parts of the typicalmicrocube indicate the hollow interiors between theindividual particle within the whole CoMn2O3. 5micro鄄cubes. Such hollow structures are beneficial for thedipping of dye solutions into the surface of theCoMn2O3. 5. It is also observed tha
35、t the CoMn2O3. 5鄄RGO microcubes are uniformly decorated and firmlyanchored on the wrinkled RGO layers. For compari鄄son, the bare CoMn2O3. 5was synthesized by a similarprocedureaccordingtothesynthesisoftheCoMn2O3. 5鄄RGO composite in the absence of GO(Fig. 2c). It is observed that aggregation of massi
36、veparticles occurs, which indicates that GO can play asa surfactant on the self鄄organization of CoMn2O3. 5mi鄄crocube.The thermal stability and CoMn2O3. 5content ofas鄄prepared CoMn2O3. 5鄄RGO composite were furtherdetermined by TGA (Fig. 3a). The experiment wasperformed from room temperature to 650 益
37、in airflow at a heating rate of 10 益min鄄1.For theCoMn2O3. 5鄄RGO composite,thegraduallossofweight under below 200 益 is due to the removal ofphysically adsorbed water in the heating process. Theweight rebound could be attributed to the reaction ofCoMn2O3. 5with O2in air in the temperature range of300鄄
38、420 益. The loss of weight above 420 益 is at鄄tributed to the removal of carbon sketch by burning鄄off of RGO. As a result, CoMn2O4( JCPDS CardNo. 77鄄0471) with a weight percent of 81. 74% is leftat 650 益 when RGO is burned up (evidenced byXRD analysis in Fig. 3b). Accordingly, the mass145第 6 期QU Jiang
39、鄄ying et al: A CoMn2O3. 5鄄RGO hybrid as an effective Fenton鄄like摇percentage of CoMn2O3. 5in the CoMn2O3. 5鄄RGOcomposite is estimated to be 78. 93%.摇 摇The CoMn2O3. 5鄄RGO composite exhibits a typeIV sorption isotherm (Fig. 4a) indicating its meso鄄porous structure.The pore size distribution of theCoMn2
40、O3. 5鄄RGO centers at 5, 9, 29 and 25 nm(Fig. 4b), and its BET surface area is 24 m2g鄄1.摇 摇 XPS has also been performed to further illustratethe reduction of the GO into RGO, as shown in Fig.5. Fig. 5a. shows the C 1s deconvolution spectra ofRGO in the CoMn2O3. 5鄄RGO composite. The C 1s詤詤can be decon
41、voluted to the peaks ofCC / CC inaromatic rings, CO ( epoxy and alkoxy), and詤詤COgroups at 284. 6, 285. 9, and 288. 4 eV, re鄄spectively. Compared with GO (Fig. 5b. ), the in鄄tensity of the peak of C詤詤C/ CC (284. 6 eV) be鄄comes predominant, while the ones of CO and詤詤COdecrease dramatically. Such resul
42、ts indicatethat most of the oxygen鄄containing functional groupsof the CoMn2O3. 5鄄RGO composite are removed afterthe heat treatment.Fig. 3摇 (a) TGA of the CoMn2O3. 5鄄RGO composite, (b) XRD pattern of the corresponding product(CoMn2O4) after thermal treatment of the CoMn2O3. 5鄄RGO at 650 益 in air atmo
43、sphere.Fig. 4摇 (a) Nitrogen adsorption and desorption isotherms and (b) pore size distribution curve of the CoMn2O3. 5鄄RGO.Fig. 5摇 C 1s XPS spectra of (a) the CoMn2O3. 5鄄RGO composite and (b) GO.摇摇The application of as鄄synthesized CoMn2O3. 5鄄RGO composite was studied for decomposition ofMB, RhB and
44、OGII in the presence of H2O2at roomtemperature. At a certain reaction interval, the UV鄄245摇新摇 型摇 炭摇 材摇 料第 34 卷vis spectra of the three dyes in aqueous solutions weremeasuredaftercatalysisreactionswiththeCoMn2O3. 5鄄RGO composite, as shown in Fig. 6a鄄c.The characteristic peaks of 485, 664 and 554 nm a
45、reobserved from the starting solution of OGII,MB andRhB, respectively. After both the CoMn2O3. 5鄄RGOand H2O2were added into the above dye solutions,the intensities of their typical absorption peaks de鄄creased with the prolonged time and the dye solutionsturned colorless gradually (shown in the inset
46、 of Fig.6a鄄c). The relationship between the decompositionrate of the three dyes and reaction time is shown inFig. 6d with the CoMn2O3. 5鄄RGO composite as thecatalyst as compared with individual CoMn2O3. 5. Foreach dye, the degradation rate of the CoMn2O3. 5鄄RGO composite is similar in the early 10 m
47、in butgradually higher than that of individual CoMn2O3. 5with increasing the reaction time. It is found that theCoMn2O3. 5鄄RGO composite exhibits different degra鄄dation efficiencies for OGII, RhB and MB. For ex鄄ample, the 100% decomposition of OGII, MB andRhB with the CoMn2O3. 5鄄RGO as the catalyst
48、was re鄄alized within 50, 70 and 80 min, respectively. Whenthe 100% decomposition occurred, the degradationrate forindividualCoMn2O3. 5reaches 96. 24%,43. 98% , and 50% for OGII , MB and RhB ,Fig. 6摇 Absorption spectra of (a) OGII, (b) MB, (c) RhB solutions (50 mg L鄄1, 10mL) in the presence of the Co
49、Mn2O3. 5鄄RGOcomposite for the same time interval, the insets are the photo images, (d) time profiles of three dyes colorizations with the varioussamples under different conditions, (e) PL spectra changed with UV light irradiation time on the CoMn2O3. 5鄄RGOcomposite and (f) PL spectra of the various
50、samples in a basic solution of TA under UV light irradiation in the fixed time of 50 min.345第 6 期QU Jiang鄄ying et al: A CoMn2O3. 5鄄RGO hybrid as an effective Fenton鄄like摇respectively. Accordingly, the synergistic effect ofCoMn2O3. 5and RGO plays an important role in en鄄hancing the degradation perfor
