Remediation Of Petroleum-Contaminated Soil By Sodium Persulfate Activated By Carbon-Supported Bimetallic

Petroleum is a mixture of mainly hydrocarbon elements that can enter the soil and accumulate in the human body through various pathways,seriously endangering the ecological environment and human health.PS-based chemical oxidation techniques are favored by researchers for their high stability,strong oxidation,low toxicity,more friendly reaction products,and easy transportation of the agents.The commonly used zero-valent iron nanoactivators have a high ability to activate PS,but their agglomeration and passivation phenomena limit their application.The purpose of this study is to solve the agglomeration and passivation problems of nano-zero-valent iron by carbon loaded bimetals to fully utilize the activation potential of nano-zero-valent iron and further improve its activation ability.Therefore,in this study,an carbon-loaded bimetallic material with high activation efficiency was screened,to analyze the degradation mechanism of soil petroleum by Fe-Mn@AC/PS system,and the risk evaluation of the remediated soil by Fe-Mn@AC/PS system was carried out.Firstly,by comparing the degradation effect of four carbon-loaded bimetallic activation PS systems on soil petroleum,the Fe-Mn@AC material with higher activation efficiency was obtained.Next,the materials were optimized,and it was found that the Fe-Mn@AC/PS system had the best degradation effect on soil petroleum when the carbon loading rate of Fe-Mn@AC material was 15%and the ratio of Fe-Mn bimetal was 1:1.The characterization results such as SEM,XPS and FTIR showed that the Fe-Mn bimetal was successfully loaded onto the AC surface and had good dispersion.Secondly,the reaction conditions of Fe-Mn@AC/PS system were optimized,and it was found that when the PS dosage was 10%,Fe-Mn@AC material dosage was 3%,the water-soil ratio was 3:1,the initial pH of the reaction system was 5,and after 4 d of reaction,the degradation rate of soil petroleum by Fe-Mn@AC/PS system reached 85.69%.At the same time,the effect of common salt ions in the soil environment on the reaction system was investigated,and it was found that after adding 1%NaCl,Na₂CO₃ and Na₂SO₄,the soil petroleum degradation rate decreased by 13.53%,10.54%and 24.91%,respectively.The degradation effect of Fe-Mn@AC/PS system on soil petroleum could be further improved by four additions of PS with the same overall addition amount.Thirdly,the degradation mechanism of soil petroleum by Fe-Mn@AC/PS system was analyzed,and it was found that the free radical mechanism contributed the most to the degradation of soil petroleum compared to the non-radical mechanism,which was 43.13%.Among the hydroxyl radicals and sulfate radicals,the contribution of sulfate radicals to the degradation of soil petroleum was higher than that of hydroxyl radicals.After the oxidation of Fe-Mn@AC/PS system,the percentage of petroleum degrading bacteria genus in the soil increased by 23%.Finally,the effect of Fe-Mn@AC/PS system on soil environment was evaluated,and it was found that Fe-Mn@AC/PS system had lower effect on soil microbial diversity compared with Fe/PS and Fe@AC/PS systems.Compared with the contaminated soil,the percentage of Actinobacteria and Firmicutes in the restored soil increased by 24.33%and 18.5%,respectively.And the germination rate of wheat seeds in the remediated soil（87.5%）was close to that in the original soil（92.5%）,indicating that the remediated soil was less toxic to plants.