Biochar Supported Nano Iron Activated Persulfate For Petroleum Soil Remediation And Bioremediation Reaction Mechanism

As a kind of industrial raw material widely used in the world,petroleum hydrocarbons has been leaking into the environment in the course of inappropriate transportation and industrial use.Soil,as a sink of all pollutants,has been heavily polluted,especially in the industrial site.At present,sodium persulfate(PS)activated by nano iron(nZVI),as one of advanced oxidation method has became the most important methods for soil remediation polluted by petroleum hydrocarbons.However,due to its own vulnerability to oxidation,carrier is necessary with nZVI to improve its reactive activity.In the study,biochar was used as carriers to supported nZVI to improve the remediation efficiencies of PS for petroleum hydrocarbons soil,as well as the improvement of the soil physical and chemical properties and protection for microbial activity.Therefore,the application of both PS and BC-nZVI could theoretically achieve the goal for in situ combied remediation of petroleum hydrocarbons polluted soil.The main results of this study are as follows:(1)BC-nZVI and nZVI was synthesized using liquid phase reduction method.The optimum conditions for PS activation system were screened to improve the efficiencies of petroleum degradatioin.The optimum conditions in the PS activation system was determined as 15%PS dosage ratio,nZVI/PS molar ratio of 1:1,BC/nZVI mass ratio of 5:1.It was found that BC-nZVI could increase the efficiency of petroleum hydrocarbon degradation after 60 days remediation.Among the experiment period,the soil degradation efficiencies showed two different stages of remediation processes:rapid degradation during 0-6 days and slow degradation after that.(2)The mechanism of chemical and microbial degradation in the remediation process of BC-nZVI group was analyzed.With the consuming of the PS oxidant,combined with the microbial metabolic activity,the petroleum hydrocarbons degradation in the BC-nZVI group could be divided into two stages:chemical oxidation and microbial degradation,which were during 0-6 d and 7-60 days,respectively.The chemical degradation and microbial degradation processes were both in line with the pseudo first-order degradation kinetic equation,and the kinetic coefficients were ABC-nZVI=1.056 day-1 and 0.02 day-1,respectively.The chemical degradation rate was higher than that of the microbial degradation rate.The carbon sources of C8-C20 generated in the chemical degradation stage were further transformed in the microbial degradation stage.However,carbon sources of C20-C30 were refractory for further transformed.(3)The addition of BC improved the soil properties of BC-nZVI group,enhanced the microbial carbon metabolism capacity,and improved the microbial abundance and community structure.The pH of soil in BC-nZVI group increased from 5.62 to 6.22 during the experiment,while the nZVI group only increased from 3.17 to 4.59.The metabolic capacity of carbon source in the BC-nZVI group decreased first and then increased,while the nZVI group showed complete inhibition.During the experiment period,soil microbial abundance and structure changed greatly,but the microbial abundance of BC-nZVI group was significantly higher than that of nZVI group,especially on 60th day,when Acinetobacter,as a kind of hydrocarbon degrading bacterium,became the dominant bacterium.