Effect Of Persulfate On BTEX/Ethanol Of Gasoline In Sandy/Limestone Aquifer Media

Benzene,toluene,ethylbenzene and xylene in gasoline are collectively referred to asBTEX,which can cause“cancer,teratogenic and mutation”effect.BTEX are highly toxicpollutants and great threats to human health and environmental ecological balance once entered into the groundwater.With the promotion of ethanol gasoline,a series of new environmental problems are inevitable.As a new oxidant with high efficiency and ideal treatment effect,persulfate has been widely used in the remediation of petroleum organic contaminated soil and groundwater.However,the study of remediation in ethanol-gasoline contaminated groundwater is seldom reported.In this paper,in order to explore the feasibility of the in-situ chemical oxidation of persulfate for remedication ethanol-gasoline contaminated soil and groundwater,traditional gasoline and ethanol-gasoline contaminated groundwater were selected as the object of study,BTEX and ethanol were selected as pollutants,sandy and limestone were selected as aquifer media.We investigated experiments of removal of ethanol in sandy aquifer media by persulfate oxidation and treatment of BTEX/ethanol in the limestone aquifer media by persulfate oxidation to explore the removal effect of BTEX and ethanol in groundwater by persulfate oxidation,and explored the degradation law and evaluated the influence of persulfate oxidation on hydrochemical characteristics?dissolved oxygen,pH,redox potential,conductivity,etc?.The results of this study can provide a reference for chemical oxidation of persulfate in the remediation of ethanol-gasoline contaminated groundwater.After analyzing the experiment results,the following conclusions were obtained:?1?Persulfate can effectively induce ethanol in groundwater,and its intermediate product mainly is acetate;Ethanol removal process was found to follow a pseudo-first-order reaction kinetics equation,and the rate constant of ethanol removal was 0.3447 d^-1;Batch injection of persulfate should be timely supplemented to avoid the removal rate of ethanol due to insufficient persulfate.The temperature was a key factor in the chemical oxidation of ethanol by persulfate,and it played a role of thermal activation of persulfate.?2?Persulfate and persulfate activated by Fe²⁺have a relatively ideal removal effect on BTEX in the gasoline dissolved phase,and the removal rate can reach more than 89.3%,among which benzene was the most difficult to be oxidatively degraded,and the oxidation removal effect of ethanol was not ideal,the removal rate was 34.3%?38.0%.After Fe²⁺activates persulfate,the oxidation effect was better,the removal rate of toluene,ethylbenzene and xylene was 100%.The removal rate of benzene could be increased by 16.1%?28.3%,was56.8%?69.3%;persulfate and persulfate activated by Fe²⁺can reduce the release of BTEX from gasoline into the groundwater and effectively reduce the BTEX of the pollution source area.The decrease in the BTEX concentration in the groundwater was observed in 50 days,but then the concentration would rebound due to the consumption of oxidant and the failure of Fe²⁺activation effect,which did not show a long-term decrease.?3?BTEX were oxidized and removed by persulfate before ethanol.Ethanol can accelerate the decomposition of persulfate and increase the consumption of persulfate,and reduce the degradation rate of BTEX by 1.315?1.464 mg/L/d.The removal effect of BTEX was reduced by the consumption of a large amount of persulfate in limestone aquifer media.?4?In the early stage of oxidation,the chemical oxidation of persulfate caused the decrease of dissolved oxygen and pH value of water and caused increase of redox potential and conductivity of water.With the increase of reaction time,persulfate decomposition caused the increase of dissolved oxygen in water,and the pH value of water gradually stabilized between 7 and 8 under the good p H value buffer and regulation ability of limestone.