Experimental Study On The Remediation Of Hexachlorobenzene Contaminated Soil By Dielectric Barrier Discharge

Due to the development of industrialization and urbanization in past decades,soil pollution problems have gradually emerged,leading to the rapid deterioration of environmental quality and posing a threat to the health of human beings and other organisms.The structure of persistent organic pollutants(POPs)is stable,which is difficult when POPs contaminated in soil.Traditional technologies,such as physical,biological and chemical,have the limitations of pollutants remove in soil.Non-thermal plasma(NTP),as an advanced oxidation technology with no selectivity,high efficiency,has attracted much attention in the treatment of pollutants.In this paper,dielectric barrier discharge(DBD)was used to generate non-thermal plasma for remediation of hexachlorobenzene(HCB)contaminated soil.The soil was fixed and fluidized in DBD reactor,and confirmed the feasibility of NTP technology on remediating POPs contaminated soil.HCB is the target pollutant in the full text.The main content and conclusions are as follows:(1)Using pulsed dielectric barrier discharge/TiO2 to synergistically remediate HCB contaminated soil,the results showed that pulsed discharge plasma has high efficiency on the remediation of HCB contaminated soil.Using a fixed-bed DBD reactor,the removal efficiency of HCB was 88.9%at the energy density of 242.2 J/L.The energy density of fluidized-bed DBD reactor was 172.5 J/L,the removal efficiency of HCB reached 97.3%.After the introduction of the TiO2,the removal efficiency of HCB in the two reactor structures was increased.(2)This work studied the effects of discharge parameters,carrier gas parameters and soil characteristic parameters in the process of DBD remediation of HCB contaminated soil.The results showed that:the increase of discharge voltage,air flow rate,soil alkalinity and the appropriate soil moisture content were all beneficial to the degradation of HCB.Increased the power frequency and the initial concentration of pollutants would cause the degradation of HCB to decrease.(3)The remediation effects of fixed-bed and fluidized-bed reactors on actual contaminated soil were compared,and the results showed that the concentration of high-carbon compounds in the soil decreased significantly after remediation,and the compounds with longer carbon chains were break into multiple short carbon chain compounds.The degradation effect of the fluidized-bed DBD reactor was better than that fixed-bed repair.(4)The effect of DBD on the soil morphology and the degradation process of HCB was studied.The experimental results showed that the NTP would not change the soil surface morphology,but the average particle size of the soil increased after the treatment.The reaction of NTP degradation of HCB conformed to first-order kinetics,and the degradation process was dominated by direct dechlorination/hydroxylation reactions.