Study On Remediation Of Arsenic And PAHs Contaminated Soil In Relocation Site Of A Chemical Fiber Plant

The arsenic and polycyclic aromatic hydrocarbons?PAHs?contaminated site left after the relocation of a chemical fiber plant needed urgent repair.First,the site pollution status was investigated and the current site pollution status was analyzed.Then,the remediation experiments of arsenic and PAHs contaminated soil were conducted,and suitable and cost-effective repair agents were screened out,and construction technology routes were designed respectively.Finally,the construction process of the project was followed up,and the soil of the site after the restoration was tested and analyzed.The main research results are as follows:?1?According to the analysis of the site pollution status,the content of arsenic in the soil of the arsenic-contaminated area was between 63.11-673.08 mg/kg,which was 3.15 to 33.65 times higher than the quality target?20 mg/kg?,with an average value of 354.33 mg/kg The pollution range was 0-1m,and the degree of pollution increased with the increase of soil depth.The PAHs pollution range was between0-0.5m,and there were four kinds of PAHs pollution.The content of benzo[b]fluoranthene was 1.24mg/kg;the content of benzo?a?pyrene was 0.89mg/kg;the content of indeno[1,2,3-cd]pyrene was 0.58mg/kg;The content of dibenzo[a,h]anthracene was 0.29 mg/kg,and the pollution levels were 2.19,4.45,1.03,and 5.12times the quality targets,respectively.?2?Fe SO₄,Fe S,Ca O,bentonite and sepiolite were used as stabilizing remediation agents to study the stabilization of arsenium-contaminated soil,Fe SO₄and Fe S showed similar stabilizing effects.Fe SO₄ had high remediation efficiency and could meet the requirements for soil remediation.Ca O had a better stabilization efficiency for arsenic in the soil.But it would significantly increase the p H of the soil.Sepiolite and bentonite had a certain stabilizing effect on arsenic in the soil,and the effect of sepiolite was slightly better than that of bentonite.Based on comprehensive consideration,4.31g of Fe SO₄ in 500g of soil was selected as a stabilizing repairing agent,but Fe SO₄ would significantly reduce the p H of the soil,leading to soil acidification.By adding different amounts of Ca O to adjusted the p H,it was found that adding 0.8g Ca O was the most suitable.The p H value reached 7.37,and the fixation efficiency of arsenic in soil was the highest.After the amount of the material was determined,a compound repairing agent was configured,and the concentration was determined by comparing the arsenic fixation efficiency at different soil water contents.The results showed that the soil water content was 25%as the best.For each500g of contaminated soil,the ratio of compound repairing agent to be added was4.31g Fe SO4,0.8g Ca O,and 125g deionized water.The fixation efficiency of arsenic in soil was 90.66%.?3?Fenton reagent was selected as the remediation agent for PAHs-contaminated soil.In order to explore the optimal ratio of Fenton reagent catalyst Fe SO₄ to 27%oxidant H₂O₂,3g H₂O₂ and different amounts of Fe SO₄ were added to each 500g of soil.The results showed that 0.3g Fe SO₄ had the best effect on soil remediation.The ratio of Fe SO₄ to H₂O₂ was 1:10.The removal rate of benzo[b]fluoranthene was55.64%,and the removal rate of benzo?a?pyrene was 84.44%.The removal rates of indene[1,2,3-cd]pyrene and dibenzo[a,h]anthracene reached 100%.After determining the optimal ratio of Fenton reagent,the amount of Fenton reagent required for every 500 g of soil was explored.The results showed that after adding6.6g Fenton reagent to every 500g of contaminated soil,all four PAHs contained in the soil could be oxidized and removed to achieve the restoration goal.?4?The arsenic-contaminated soil remediation route was designed to be excavated for transportation.The ectopic repair technology was adopted.After passing the self-inspection,it was fired into a kiln to make ceramsite.The PAHs-contaminated soil remediation route was as follows:the contaminated soil was mixed with the repairing agent and mixed in place,and then excavated and transported to the conservation area for off-site conservation.After the construction of the project is completed,the soil after inspection and repair will be tested,the test results were as follows:A total of 23 arsenic-contaminated remediation points were sampled.The p H of the arsenic-contaminated site was 7.21 to 7.65 after the remediation.The soil arsenic content ranged from 11.4 mg/kg to 19.5 mg/kg.The average arsenic content at the site was 15.1 mg/kg.No samples were found to exceed the quality targets,and the project was successfully repaired.Eleven arsenic-contaminated soil-stabilized samples were taken for leaching toxicity analysis.Seven of them had no arsenic concentration detected,three samples had arsenic concentrations of 0.01 mg/L,and one sample had arsenic concentrations of 0.02 mg/L.All sample concentrations were lower than the arsenic leaching concentration mass target,and the engineering repair was successful.5 soil samples were taken from the PAHs site.No pollutants were detected in the two samples,and the benzo[b]fluoranthene content was 0.2mg/kg in the other three samples.The contents of indeno[1,2,3-cd]pyrene were 0.2 mg/kg and 0.1 mg/kg,respectively.All of 5 samples met the quality target and the engineering repair was successful.