Treatment Of Nitrophenol And Chlorophenol Wastewater By Electro-Fenton Method

Wastewater containing phenols is toxic to microorganism, so traditionalbiochemical methods are not fit. It is of great value to develop an alternativemethod to degrade the water. As an advanced oxidation process,electro-Fenton method has been studied in recent years. In this article, simulated nitrophenol and chlorophenol wastewater weretreated by electro-Fenton method. Firstly, anodic Fenton method wasinvestigated to degrade simulated nitrophenol wastewater using activatedcarbon fibers(ACF) as cathode and Fe as anode with the introduction ofaeration. The optimal electrolysis conditions were found to be 3.6g/L NaCl,pH3.0 and 10v electrolysis voltage, the corresponding removal of 4NP andCODCr were 82.8% and 72.0% respectively. Zero-order reaction kinetics wasobserved, the degradation pathway and energy consumption were alsodiscussed. In the second part, pentachlorophenol(PCP) was treated byelectro-Fenton method, which employed graphite as cathode and Pt as anodewith the addition of Fe ion. In the optimal conditions of 5v electrolysisvoltage, 0.14mol/L Na2SO4 and pH2.5, addition of Fe ions could absolutelyaccelerate the process. Reaction mechanism was analyzed detailedly by thedetermination of intermediates and chloride. Intermediate products like1,2-tetrachlorocatchaol, 1,4-tetrachlorocatchaol and tetrachloro-p-hydroquin-one were detected by GC/MS. Pseudo first-order reaction kinetics appeared inthe fist stage and the constant was 0.019min-1. Finally, in the optimalconditions of electro-Fenton system, various chlorophenols were treated toresearch the relationship between chlorine content and degradation rate. Thesequence of rate constant was obtained to be: 2,4-dichlorophenol(2,4-DCP)>2,4,6-trichlorophenol(2,4,6-TCP)>PCP>4-chlorophenol(4-CP). Using either ACF or graphite as cathode to electro-generate Fenton'sreagent to treat wastewater containing phenols has not been reported. And the Irelationship between chlorine content and degradation rate was never studiedby electro-Fenton method. This study is significative to the development ofelectro-Fenton method.