Synthesis And Performance Of Cerium-Modified Carbon Based Fe₃O₄ Mimic Enzyme Catalyst

Large amounts of dyes produced annually are applied in many different industries,including the textile,cosmetic,paper,leather,pharmaceutical,and food industries.There are more than 100,000 kinds of commercially available dyes with an estimated annual yield of over 700,000 tons,of which 15%are lost during the dyeing process.The release of dye wastewater is a remarkable source of aesthetic pollution,eutrophication,and perturbace in aquatic environment,with the characteristics of toxic,carcinogenic,mutagenic,or teratogenic to various microorganisms and fish species.Because of component complexity,high concentration and biodegradation resistant in dye wastewater,prevailing advanced treatment technologies are hard to solve the contaminants economically with high efficiency,easy operation and infrequent secondary pollution in wastewater.Therefore,it is necessary to seek a novel technology that is high efficient,low cost,and environmental friendly for the advanced treatment of industrial dye wastewater.In this paper,Fe₃O₄ was supported on cerium-impregnated coke by the method of precipitation to prepare a novel cerium-modified carbon based Fe₃O₄（Ce/Fe₃O₄/MC）mimic enzyme catalyst.The preparation of Ce/Fe₃O₄/MC mimic enzyme catalyst and its adsorption,degradation and mechanism of dye wastewater were investigated.The main conclusions of this dissertation were shown as follows:（1）The modified coke made was prepared with the conditions of alkali carbon ratio of 4:1,the activation temperature was 750℃,and the activation time was 1 h.Then,the Ce-modified coke（Ce/MC）composites were prepared by the impregnation method.The optimum preparation conditions were as follows:the immersion concentration was 0.02mol/L,the immersion time was 2 h,the calcination temperature was 300℃,and the calcination time was 2 h.The prepared Ce/MC had good adsorption to rhodamine B;Under the conditions of the initial solution pH value was 4.0,Ce/MC content was 800 mg/L,H₂O₂ content 30 mmol/L,reaction temperature was 25℃and reaction time was 2 h,the removal rate of rhodamine B in 100 mg/L rhodamine B wastewater was 18.1%.The characterizations of Ce/MC by FTIR,SEM and EDS showed that there were abundant hydroxyl functional groups on the surface of Ce/MC,and the modified coke had layered structure.The EDS data could show that cerium could successfully modify coke.（2）The Ce/Fe₃O₄/MC mimic enzyme catalyst prepared by coprecipitation method using Ce/MC as a template had a zero point of 7.73 and a saturation magnetization of 27.01emu/g,which was to magnetically separation.The degradation of rhodamine B through the catalysis of Ce/Fe₃O₄/MC mimic enzyme catalyst was implemented to determine the optimal loading conditions of Fe₃O₄ as follows:the iron concentration was 0.035 mol/L,the ratio of the amount of Fe²⁺:Fe³⁺was 3:4,the pH value was 11,reaction temperature was 70℃,crystallization time was 60 min,that could gain the highest degradation efficiency of rhodamine B.The data of FTIR of Ce/Fe₃O₄/MC mimic enzyme catalyst showed that there were a large number of oxygen-containing functional groups on the surface of Ce/Fe₃O₄/MC mimic enzyme catalyst with good organic affinity.The spherical particles could be clearly seen on the surface of Ce/Fe₃O₄/MC mimic enzyme in the SEM spectrum.EDS indicated that it could contain Fe,Ce,C,O and other elements.There were diffraction peaks of Fe₃O₄ and CeO₂ in the XRD spectra,and the grain size decreased from61.39 nm to 40.22 nm.The XPS spectra further proved that the iron oxide in the catalyst was Fe₃O₄,and the oxide of cerium was mainly in the form of CeO₂,and cerium ions existed in the form of Ce⁴⁺and Ce³⁺ions.In summary,Fe₃O₄ and CeO₂ were successfully loaded on modified coke,and the doping of CeO₂ was conducive to reducing the size of Fe₃O₄ and enhancing the activity of Fe₃O₄.The Ce/Fe₃O₄/MC mimic enzyme catalyst had excelent degradation ability of rhodamine B dye.（3）The adsorption process of rhodamine B by Ce/Fe₃O₄/MC mimic enzyme catalyst was in accordance with the quasi second order kinetic equation.The saturated adsorption capacity of Ce/Fe₃O₄/MC mimic enzyme catalyst was 45.7 mg/g at 25℃.Langmuir isotherm adsorption model could preferably reflect its adsorption process of rhodamine B on Ce/Fe₃O₄/MC mimic enzyme catalyst.The Ce/Fe₃O₄/MC mimic enzyme catalyst had a high adsorption capacity for rhodamine B in a wide pH range.When the dosage was 3.0g/L,the adsorption removal rate could reach 97.06%.（4）The optimum conditions for the degradation of rhodamine B by the Ce/Fe₃O₄/MC mimic enzyme catalyst were as follows:dosage of Ce/Fe₃O₄/MC imimic enzyme catalyst was 0.8 g/L,initial concentration of H₂O₂ was 30 mmol/L,the initial pH value was 4.0,the temperature was 35℃.Under this condition,the removal rate of rhodamine B within120 min was up to 97.24%.In the H₂O₂-Ce/Fe₃O₄/MC system,the adsorption-catalytic synergy among Fe₃O₄,CeO₂ and MC significantly improved the catalytic performance of Ce/Fe₃O₄/MC mimic enzyme catalyst,in which rhodamine B could be degraded effectively.In addition,Ce/Fe₃O₄/MC mimic enzyme catalyst could have the characteristics of low dissolution of Fe,easy magnetic separation recovery and reuse.