| The main characteristics of dye wastewater are high chroma,high organic content,poor biodegradability,"three causes" effect,and great harm to the environment and human body.Therefore,it is very important to seek efficient dye wastewater treatment technology.In recent years,the high-efficiency degradation of refractory dyes by heterogeneous Fenton technology using iron-based solid materials as the main catalysts in advanced oxidation technology has attracted widespread attention from scholars.Although pH range of heterogeneous Fenton catalysts has been broadened to neutral at present,it still can not meet the needs of wastewater treatment under alkaline conditions.Therefore,it is necessary to continue to research and develop high-efficiency heterogeneous Fenton catalysts under alkaline conditions.In this paper,Fe-Cu-Co and Fe-Cu-Co/zeolite heterogeneous Fenton catalysts were prepared by the sol-gel method,the preparation conditions were optimized,and a series of characterization analyses were performed on the prepared catalysts.The single-factor experiment was conducted to investigate the catalytic degradation performance of Fe-Cu-Co/zeolite on methylene blue under alkaline conditions.The optimal value of the experimental parameters was further determined by the response surface method,and the stability of the catalyst was verified.Finally,the catalytic mechanism of Fe-Cu-Co/zeolite heterogeneous Fenton catalyst under alkaline pH was studied.Through the experiment of optimizing the preparation conditions of the catalyst,it can be obtained that when the molar ratio of iron,copper and cobalt is 2:0.7:0.3,the molar ratio of metal zeolite is 1:1,and the calcination temperature and time are 400℃ and 3 h,respectively,the preparation The iron-copper-cobalt/zeolite catalyst had the best performance.Through a series of characterization and analysis of the catalyst,it can be seen that the Fe-Cu-Co/zeolite had an amorphous structure,with small particle size,compact distribution,good pore structure,large specific surface area,and the Fe,Cu and Co were successfully loaded onto zeolite.Through the single factor experiment,it can be obtained that when the concentration of the pollutant methylene blue solution was 100 mg/L,the pH was 10,the reaction temperature was 30℃,the catalyst dosage was 0.8 g/L,the H2O2 concentration was 60 mM,and the oxidation reaction was 3 h,The decolorization rate of the Fe-Cu-Co/zeolite catalyst for methylene blue was 93%,and the catalytic degradation effect was good.The reaction system was added with a buffer to maintain the alkalinity of the solution so that the solutions before and after the reaction were alkaline,indicating that the application of the Fe-Cu-Co/zeolite heterogeneous Fenton catalyst under alkaline conditions is feasible.The optimal values of the experimental parameters for the catalytic degradation of methylene blue by Fe-Cu-Co/zeolite were obtained by response surface method:the dosage of the catalyst was 1.00 g/L,the concentration of H2O2 was 80 mM,and the actual decolorization rate was 95.78%after 2 h of catalytic oxidation reaction,and after 3 h of oxidation reaction,the TOC removal rate of methylene blue was 35%.After the Fe-Cu-Co/zeolite was reused for 5 times,the decolorization rate of methylene blue remained above 80%,and the amount of Fe-Cu-Co ions eluted was small,indicating that the Fe-Cu-Co/zeolite catalyst has good stability.The study on the catalytic mechanism of Fe-Cu-Co/zeolite heterogeneous Fenton catalyst on methylene blue at alkaline pH showed that the active substances in the reaction system are OH and ·OOH,and OH plays a major role,while OOH plays a minor role.First,methylene blue and H2O2 were adsorbed on the surface of the catalyst,and then the Fe,Cu and Co on the catalyst activate H2O2 to generate OH and OOH.The two free radicals attacked methylene blue to decolorize and degrade it.The synergistic effect of Fe,Cu and Co in the reaction system is beneficial to promote the redox cycles of Fe3+/Fe2+,Co3+/Co2+and Cu2+/Cu+,thereby enhancing the catalytic activity of Fe-Cu-Co/zeolite. |
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