Study On Catalytic Decomposition Of P-nitrophenol By Electro-Fenton-Like Reaction

In this study,in allusion to the existing deficiencies of traditional electrochemical techniques using in wastewater treatment,a Electro-Fenton-Like reaction system was constructed,which and using heterogeneous catalyst as filler in a electrolytic cell. Combination of electrochemistry with heterogeneous catalysis is realized.The H₂O₂, produced in the side electrolysis reaction,was catalyzed by the heterogeneous catalyst to oxidize the organic compounds in p-nitrophenol wastewater and strengthen the degradation effect.The mechanism of p-nitrophenol degradation was investigated using the composition of organic in the effluent.The Fe₂O₃/7-Al₂O₃ catalyst was prepared by dipping method using two ferric salt solutions as the precursor aqueous solution.The preparation parameters were optimized using the p-nitrophenol removal efficiency as the evaluation criteria,which oxidized by catalyzing H₂O₂ under room temperature and atmospheric pressure.The structure of catalyst was characterized.The results showed that the catalyst with 0.1mol/L Fe(NO₃)₃/0.7%oxalic acid mixture solution as the precursor aqueous solution,dipped at 30℃for 10 hours and calcined at 350℃for 2 hours has the highest catalytic activity.The operation condition of electrochemical degradation of p-nitrophenol was optimized by pure-electrolytic experiments in a non-membrane electrolytic reactor,a better result was obtained after 5 hours electrolysis under current intensity to 400mA, initial pH value to 2.5 and the concentration of Na₂SO₄ to 1000mg/L.Under this condition,added the catalyst into a non-membrane electrolytic reactor to establish the catalytic-aeration packed bed reactor,some blank tests were carried out simultaneously. The results showed that p-nitrophenol solution(100mg/L) with pH value to2.5 was electrolyzed for 5h in this system,the treatment efficiency significantly enhanced comparing with other blank control experiments,the removal rate of p-nitrophenol and COD were 89.38%and 47.26%,respectively,the degrading process of p-nitrophenol was a pseudo first-order reaction,and the reaction rate constant was 0.782,increased by 67.4%compared with the pure electrolytic system.The BOD₅/COD rate was promoted to 0.506 from 0.13 of the pure electrolytic system.Through UV-VIS and HPLC analysis the intermediate products was a spot of benzoquinone and other aromatic compounds in the outflow of electro-Fenton-like reaction system,while some short chain fatty acids were the major organics in the effluent.The H₂O₂ produced by electrolytic side effects was changed into·OH by the Fe₂O₃/γ-Al₂O₃ catalyst,coupled with the direct electrochemical reaction,then markedly enhanced the treatment effect.The intermediate products in different cells of a membrane electrolytic reactor were detected,the oxidation pathway and reduction pathway of p-nitrophenol were speculated and the mechanism of p-nitrophenol degradation was investigated combining with the intermediate products in pure-electrolytic system and electro-fenton-like reaction system.