Fenton Pre-oxidation Followed By Microbial Degradation To Remove Crude Oil From Contaminated Soil

Petrochemical industry is one of the important energy industries in the development of national economy.However,in the long-term process of mining,transportation,storage and transportation,accidents such as "running,risking,dripping,leaking" have caused soil and groundwater pollution,endangering human health and ecological environment.It has been pointed out that chemical oxidation followed by microbial degradation of crude oil contaminated soil can achieve good remediation effect.However,how to further optimize the technical parameters of chemical oxidation and microbial remediation has not been explored.In this paper,sodium percarbonate(Na2CO3·1.5H2O2)was used to replace hydrogen peroxide(H2O2)in traditional Fenton reagent to explore its degradation effect on crude oil contaminated soil,and the slow release mechanism of Na2CO3·1.5H2O2 was explored by EPR.The effects of Fenton oxidation on the community structure and functional genes of soil microorganisms were also analyzed.Finally,crude oil degrading bacteria were screened out from crude oil contaminated soil,and then the soil with different oxidation degree was biodegraded to the same degree,and the correlation between the physicochemical properties of oxidized soil and the properties of residual crude oil and the subsequent biodegradation rate was analyzed.This paper provides some theoretical support for Fenton oxidation followed by microbial technology to remediate crude oil contaminated soil,and achieves the following results:1.The degradation rate of crude oil by Fenton reagent formed by H2O2 is 55.07%,while that of crude oil by Fenton reagent formed by Na2CO3·1.5H2O2 containing the same amount of H2O2 is 72.64%2.The free radicals in Fenton reagent formed by two oxidants were tested by EPR.The results showed that OH existed in Fenton reagent formed by two oxidants,and OH formed by H2O2 disappeared within 30 minutes,while OH formed by Na2CO3·1.5H2O2 still existed at 60 minutes.3.The structure and functional genes of microbial community in soil oxidized by Fenton reagent showed that the abundance of indigenous microbial community in soil oxidized by Fenton reagent decreased,but the diversity index changed little,and the dominant population in soil oxidized by Fenton reagent changed from Actinobacteria to Proteobacteria.At the same time,the total number of genes in soil decreased after oxidation,but the proportion of various pathway genes changed little.4.Through the correlation analysis between the subsequent microbial degradation rate and the physical and chemical properties of the oxidized soil and the oil properties,the order of correlation is as follows:the ratio of TOC to NH4+-N(R2=0.9513)>the ratio of light oil component to the heavy oil component(R2=0.9095)>the percentage of<C23 hydrocarbons(R2=0.8259)>crude oil contents(R2=0.7603)>pH(R2=0.7492)>number of microorganisms(R2=0.6506).