Theoretical limiting concentration for mineralization of trichloromethane and dichloromethane in aqueous solutions by AOPs  

作　　者：JI YuanHui HUANG WenJuan LU XiaoHua YANG ZhuHong FENG Xin 

机构地区：[1]State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, Nanjing 210009, China

出　　处：《Science China Chemistry》2011年第3期559-564,共6页中国科学（化学英文版）

基　　金：supported by the Chinese National Key Technology Research and Development Program(2006AA03Z455);NSFC-RGC(20731160614);Program for Changjiang Scholars and Innovative Research Team in Univer-sity(IRT0732);National Basic Research Program of China(2009CB226103);the National Natural Science Foundation of China(20976080)

摘　　要：It is widely stated that most organic contaminants could be completely mineralized by Advanced Oxidation Processes(AOPs). This statement means that the concentration of the organic contaminant at equilibrium(limiting concentration,LC)is low enough to be neglected.However,for environmental safety,especially drinking water safety,this statement needs to be verified from chemical engineering thermodynamic analysis.In this paper,trichloromethane(CHCl3)and dichloromethane(CH2Cl2) are selected as the model systems,and the equilibrium concentration(theoretical limiting concentration,TLC)for the mineralization of chlorinated methanes in aqueous solutions at the different initial concentrations of chlorinated methanes,pH values and·OH concentrations by AOPs are investigated by thermodynamic analysis.The results in this paper show that the TLC for the mineralization of CHCl3 and CH2Cl2 with·OH increases with increasing initial concentrations of CHCl3 and CH2Cl2,decreases with increasing concentration of·OH,and the TLC for the mineralization of CHCl3 decreases with increasing pH values except that the pH value changes from 3.0 to 3.5.For the mineralization of CH2Cl2 with·OH,at the concentrations of·OH obtained from the literature,there is no obvious change of the TLC with pH values,while as the concentrations of·OH increase by 10 and 100 times,the TLC decreases with the increasing pH values from 2.0 to 3.0 and from 3.5 to 4.5,and increases with the increasing pH values from 3.0 to 3.5 and from 4.5 to 5.0.The investigations in this paper imply that high concentration of·OH,a bit higher pH values(4.0–5.0)in acid environment and low initial concentrations of the organic contaminants are beneficial for the complete mineralization of chlorinated methanes by AOPs.It is widely stated that most organic contaminants could be completely mineralized by Advanced Oxidation Processes（AOPs）. This statement means that the concentration of the organic contaminant at equilibrium（limiting concentration,LC）is low enough to be neglected.However,for environmental safety,especially drinking water safety,this statement needs to be verified from chemical engineering thermodynamic analysis.In this paper,trichloromethane（CHCl3）and dichloromethane（CH2Cl2） are selected as the model systems,and the equilibrium concentration（theoretical limiting concentration,TLC）for the mineralization of chlorinated methanes in aqueous solutions at the different initial concentrations of chlorinated methanes,pH values and·OH concentrations by AOPs are investigated by thermodynamic analysis.The results in this paper show that the TLC for the mineralization of CHCl3 and CH2Cl2 with·OH increases with increasing initial concentrations of CHCl3 and CH2Cl2,decreases with increasing concentration of·OH,and the TLC for the mineralization of CHCl3 decreases with increasing pH values except that the pH value changes from 3.0 to 3.5.For the mineralization of CH2Cl2 with·OH,at the concentrations of·OH obtained from the literature,there is no obvious change of the TLC with pH values,while as the concentrations of·OH increase by 10 and 100 times,the TLC decreases with the increasing pH values from 2.0 to 3.0 and from 3.5 to 4.5,and increases with the increasing pH values from 3.0 to 3.5 and from 4.5 to 5.0.The investigations in this paper imply that high concentration of·OH,a bit higher pH values（4.0–5.0）in acid environment and low initial concentrations of the organic contaminants are beneficial for the complete mineralization of chlorinated methanes by AOPs.

关 键 词：thermodynamic analysis chemical equilibrium theoretical limiting concentration organic contaminant mineralization degree advanced oxidation processes chlorinated methane 

分 类 号：X703[环境科学与工程—环境工程] TV143.6[水利工程—水力学及河流动力学]