Effect Of Addition Methods Of Persulfate On The Removal Of Gasoline BTEX/ethanol From Groundwater

Persulfate?Abbreviation PS?oxidation technology has been widely used to treat organic pollutants in soil and groundwater,to explore the effect of different addition methods of persulfate on the removal of gasoline BTEX/ethanol from groundwater,the indoor micro-component experiment was carried out with a fixed molar ratio of Na₂S₂O₈:BTEX=20,Na₂S₂O₈:Fe²⁺=8.The effect of persulfate on the removal of BTEX and ethanol was studied,and the effect of persulfate on microorganisms was investigated,persulfate caused changes in water chemistry.Compared with the one-time addition and the batch addition to analyze whether the batch addition was more helpful to improve the removal effect of BTEX and ethanol.The experiment was carried out in two parts,non-sterilized and sterilized,each part included a control group(no PS and Fe²⁺added),an oxidation group?only PS added?,an activated oxidation group(added PS and Fe²⁺),and the activated oxidation group was a one-time,batch-added method.From the experimental results,drew the following conclusions:?1?Experimental results showed PS could effectively remove BTEX and ethanol pollutants in groundwater,but it also directly inhibited microbial activity.When the total concentration of BTEX was relatively low?15 mg/L in this experiment?,biodegradation was better than persulfate oxidation,therefore,in the cold region where the microbial activity was low and BTEX cannot be degraded,persulfate oxidation technology could be prioritized.PS could preferentially oxidize and remove BTEX when ethanol was present,and ethanol did not hinder PS oxidation of BTEX.?2?The total amount of PS and Fe²⁺in the experiment was constant,and the amount added in batches was added as a percentage of the total amount.The results showed unsterilized batch addition was better than one-time addition,in order to gradually increase the amount of addition:17%,33%,50%,BTEX achieved the best removal effect.Persulfate in situ repair technology,using batch addition could increase the removal rate of pollutants,and gradually increasing the amount of addition was the best way.?3?When using the method of addition on persulfate in batches,it was found that para-xylene was preferentially oxidized by the first-order kinetic decay rate constant,and the reaction rate of benzene was the slowest.Benzene was the most difficult to be oxidatively degraded when PS was used to remove BTEX.?4?The pH and Eh values of the activated group changed significantly,while the unactivated PS had less effect on the pH and Eh values in groundwater,persulfate oxidation products increased the salinity of groundwater,and the conductivity EC of each group remained basically the same,a large amount of SO₄^2-was produced during the persulfate oxidation process,and a large accumulation of SO₄^2-increased the salinity in the water.