Effect And Characteristic Of Different Valence Forms Of Iron On2,4,6-trichlorophenol Degradation By Anaerobic Microorganism

Our team has devoted to the degradation of chlorophenols by an integrated “Fe0-microorganism” system and has made great progress, while the conversion and effectsbetween Fe0, Fe2+and Fe3+under this system were complicated, it’s hard to understandthe influence of different valence forms of iron on chlorophenols degradation byanaerobic microorganism. Therefore, batch tests in the laboratory were conducted, aimingat studying the influences of different valence forms of iron on anaerobic biodegradationof2,4,6-trichlorophenol(2,4,6-TCP), under the condition of initial pH value=7.0. Thestudy about the influences of different initial pH value on2,4,6-TCP degradationefficiency, the changes of system real time pH value, iron ion concentration andmicrobial activity was further investigated; through measuring and analysing theintermediate products of2,4,6-TCP, the degradation pathway of2,4,6-TCP by differentsystems was discussed. The results were demonstrated below:(1) Iron element in different valence state had different influence on2,4,6-TCPdegradation of anaerobic microorganisms. When the initial pH value was7.0,“Fe2+-microorganism” system and “Fe0-microorganism” system can degrade30mg/L2,4,6-TCP completely within120h and144h respectively, while the degradationefficiency of2,4,6-TCP by microorganism system and “Fe3+-microorganism” system onlycan achieve69.56%and53.23%within144h respectively.(2) When the initial pH value was neutral or acidic, the Fe2+-microorganism systemcould exert a better accelerative effect on the2,4,6-TCP degradation than the others,however, when the initial pH value was alkalic, the “Fe0-microorganism” system hadbetter performances on the2,4,6-TCP degradation than the others.(3) Each of the “Fe0/Fe2+/Fe3+-microorganism” system had the ability to adjust pH,among which, the “Fe0-microorganism” system performs the best.(4) In the condition of different initial pH value, the influence of different valenceiron on anaerobic microbial activity and2,4,6-TCP degradation remains the same. Whenthe initial pH value was neutral or acidic, the different of dehydrogenase activity (DHA)between “Fe2+-microorganism” system and “Fe0-microorganism” system was little, theDHA of these two systems were twice larger than the “Fe3+-microorganism” system;when the initial pH value was alkali, the different of DHA between “Fe2+-microorganism”system and “Fe3+-microorganism” system was little, the DHA of “Fe0-microorganism”system was three times than that of “Fe2+-microorganism” system. (5)2,4-DCP and4-CP were the main intermediate products of2,4,6-TCP degradatedby “Fe0/Fe2+/Fe3+-microorganism” system through analyzing the results of HPLC andGC-MS, and these systems had the ability to degrade intermediate products, moreover,when the initial pH value was neutral or acidic, intermediate products were easier to bedegraded, what’s more, the Fe2+-microorganism system could exert a better accelerativeeffect on the intermediate products degradation than the others.(6)“Fe0/Fe2+/Fe3+-microorganism” system had the same degradation pathway of2,4,6-TCP, but had different degree of degradation, the2,4,6-TCP degradation pathway of“Fe0/Fe2+-microorganism” system was:2,4,6-TCP�'2,4-DCP�'4-CP�'phenol, whilethe2,4,6-TCP degradation pathway of “Fe3+-microorganism” system was:2,4,6-TCP�'2,4-DCP�'4-CP.