Study On In Situ Remediation Of Aniline Contaminated Ground Water By Activated Persulfate

As an important organic chemical raw material and product,aniline（AN）is widely used in dye production,pharmaceutical manufacturing and other industries.In the production process of aniline,leakage often occurs,resulting in groundwater pollution.Activated persulfate oxidation is currently the most commonly used method for in-situ chemical oxidation remediation of organically polluted groundwater.Different activated persulfate systems have been extensively studied in the treatment of organic wastewater and even in the remediation of organically polluted groundwater,but there are still the following shortcomings:First,relevant studies mainly investigate the oxidation efficiency of different reaction systems to organic pollutants,and little attention is paid to the environmental risks of activated persulfate oxidation in situ remediation.Second,the tailing and rebound problems of pollutants are common in practical remediation projects.Optimizing the injection method and slow-releasing oxidant is an important way to solve this problem,but it has not received sufficient attention.Therefore,there is an urgent need for efficient,cheap,safe and long-term remediation technology for organically polluted groundwater.In this study,AN was used as the target pollutant,and a one-dimensional simulation device was used to study the in-situ remediation efficiency and mechanism of different activated persulfate reaction systems.Firstly,the three most commonly used activated persulfate systems,including alkali（Na OH）,iron(Fe²⁺),and strong oxidant（H₂O₂）,and their effects and environmental risks in remediating AN-contaminated groundwater under different injection methods were investigated.Secondly,for the problem of tailing and rebounding of organic pollutants.Using stearic acid（SA）as a binder,PS capsules and Fe SO₄capsules were prepared as Permeable reactive barrier（PRB）media,respectively,and a combined PRB of PS and Fe SO₄（referred to as PS-Fe SO₄-PRB）was constructed.The release rule of active substances in PRB and the degradation efficiency,mechanism and environmental effect of combined PRB on AN were studied.Third,in view of the cost of activators,petroleum-contaminated soil（PCS）was used as raw material,and ferrate pretreatment and co-pyrolysis were used to convert to persulfate activators carbonated soil（CS）and iron modified carbonated soil（Fe–CS）as PRB media.The remediation effect and mechanism of filling CS and Fe–CS activated persulfate on AN-contaminated groundwater were also studied.The main research results are as follows:（1）In the in situ injection experiment,H₂O₂-activated PS treatment had the best effect on AN removal.The oxidant waste problem of constant concentration injection was overcome during the injection of decreasing concentration,and the cumulative degradation rate of AN reached 83%within 4 days.The acute toxicity of water quality in different treatments was higher than that before treatment,mainly due to the residual sulfate after the decomposition of sodium persulfate,which made the groundwater saturated zone after restoration to form a high-salt area.（2）The cumulative removal rate of AN in PS-Fe SO₄-PRB treatment was 69.74%,and the repair effect was significantly higher than that in direct injection treatment.The treatment can keep the p H value and Eh of the reaction system relatively stable,the acute toxicity to groundwater is lower,and the risk of secondary pollution is lower.（3）CS and Fe–CS were prepared by pyrolysis using PCS as raw material,and their activation effects on PS degradation of AN were investigated.The results showed that both CS and Fe–CS could effectively activate PS to degrade AN.After 8h,the AN degradation rates were 86.45%and 98.58,and the TOC removal rates were59.67%and 66.30%,respectively.When CS and Fe–CS were used as PRB catalyst filling media in groundwater pollution treatment,the cumulative removal rate of AN within 4 days reached 67%and 90%,respectively,and the removal of AN in groundwater was achieved.