二氧化锰氧化降解五氯酚

以二氧化锰为氧化剂,研究了pH 4.12的水溶液中五氯酚氧化降解的反应动力学,并讨论了反应溶液的pH对反应动力学的影响.结果表明,五氯酚对二氧化锰的氧化作用具有较强的反应感受性.在pH一定和二氧化锰充分过量的条件下,随着反应的进行,五氯酚的降解速度变慢,遵循的不是简单的准一级反应动力学而是复合的反应动力学.此外,随溶液pH由3.5升高6.6,五氯酚的降解速度发生显著地下降.运用溶剂萃取和气质联用仪的分析方法,检测到2个主产物和1个次产物.其中,次产物是由四氯-1,4-氢醌与四氯儿茶酚组成的混合物;2个主产物是由五氯酚氧自由基偶合而成的二聚体,且是同分异构体.在观测到的表面反应动力学和降解产物的基础上,提出了五氯酚被二氧化锰氧化降解的反应流程图.

Oxidation of Pentachlorophenol by Manganese Dioxide

This study examined the oxidative transformation kinetics of pentachlorophenol(PCP) by manganese dioxide(MnO_2) at pH 4.12 solution using manganese dioxide as an oxidant.This study also discussed the influence of pH on the reaction kinetics.Results show that PCP has highly susceptible to oxidation by manganese dioxide.The loss of PCP slows as the reaction progresses and deviates from the simple pseudo-first-order kinetics but follows complex reaction kinetics when experiments were performed at a constant pH and with an enough excess of MnO_2.Furthermore,the reaction rate of PCP decreases significantly as the pH of the reaction mixture increases from 3.5 to 6.6.Using solvent extraction and GC-MS analysis,one minor and two major products were detected.The minor product is the mixture of tetrachloro-1,4-hydroquinone and tetrachlorocatechol,and the two major products are dimeric products that formed by coupling of pentachlorophenoxy radicals.Furthermore,the two major products are structural isomers,resembling each other except for the position of nine chloride atoms on the aromatic ring.On the basis of the surface reaction kinetics and product identification observed in this study,the reaction scheme for PCP oxidation by manganese dioxide is tentatively proposed.