The Study Of Using Siderite Catalyzed Double Oxidation To Remove1,2-dichloroethane In Groundwater And The Influnence Of Organic Acid On The System

1,2-dichloroethane(1,2-DCA) is a potential carcinogenic,teratogenic,mutagenicvolatile chlorinated organic pollutant.It is widely used in industry,agriculture and ourdaily life.Its production ranked first of all chlorinated aliphatic hydrocarbons. Becausethe density of1,2-DCA is greater than water and it has the high solubility and thedifficulty to be adsorbed,it can cause a wide range of groundwater contamination.One kind of in situ chemical oxidation technique to remove1,2-DCA is studiedin this paper—using siderite-catalyzed hydrogen peroxide and persulfate to remove1,2-DCA.The catalyzed hydrogen peroxide and persulfate can produce strongoxidizing free radical to oxidize1,2-DCA.This paper compares the1,2-DCA removalefficiency of different oxidant system and analyzes the reaction kinetics andthermodynamics. Since the influnence mechanism of the organic acids on fenton andFenton-like system are poorly understood,and there is no study on the influence ofnatural organic acids to the double oxidation system, so this study is trying todetermine some new mechanistic clues about the influnence of organic acids toour systems.The main research results are as follows:Experimental results show that catalyzed hydrogen peroxide and persulfate bysiderite can remove the1,2-DCA effectively.The removal rate was over95%.Theremoval rate of Fenton-Like system is20%.The persulfate system can’t remove1,2-DCA.The lower pH,higher concentration of Fe2+,higher concentration of radicalsand oxidant leaded to the higher removal rate in the double oxidation system than thatin Fenton-Like system.The chlorine derived from1,2-DCA did not reach balance atfirst but reached balance at last, indicating that intermediates generated in the processbut dechlorinated completely at the end of the reaction.The influnence of simple organic acid--benzoic acid to the doule oxidationsystem is discussed in this paper.The result shows that different concentrations ofbenzoic acid have different impacts on system.When C(BA)<0.08mmol/L,withbenzoic acid concentration increases,the rate of degradation slow down,but does notaffect the final removal rate.When0.08mmol/L<C(BA)<2mmol/L,benzoic acid completely inhibites the degradation of1,2-DCA.When C(BA)>2.5mmol/L,withbenzoic acid concentration increases,the rate of degradation increase.The majorimpact mechanism is that benzoic acid can change the pH of the system,and thenaffect the disslove of siderite.The impact of HA on system is similar to the benzoic acid.When0mg/L<C(HA)<20mg/L,with HA concentration increases,the rate of degradation slowsdown,but does not affect the final removal rate.When20mg/L<C(HA)<500mg/L,HA inhibites the degradation of1,2-DCA and the removal rate of1,2-DCA is30%~50%. The major impact mechanism is similar to benzoic acid--HA can changethe pH of the system,and then affect the disslove of siderite.