Mechanism Of Immobilized Bacteria Based On Biochar Strengthen Remediation Of Polycyclic Aromatic Hydrocarbon Contaminated Soil

Polycyclic Aromatic Hydrocarbons(PAHs)are frequently detected organic pollutants that exceed the screening value in contaminated soil in China,microbial strengthen remediation of PAHs has received much attention now.Among them,the viability and degradation activity of microorganisms with degrading function in actual contaminated soil are the key to the success of bio-remediation.This study is based on a PAHs high-efficiency degradation bacteria Martelella sp.AD-3.By comparing the physical and chemical properties of different types of biochar,selecting the carrier of immobilized microorganisms.Based on the effect of biochar immobilized microorganisms and the degradation rate of PAHs,the preparation of biochar immobilized bacteria agent was optimized.And the prepared biochar immobilized bacteria agent was used to strengthen the remediation of PAHs contaminated soil to achieve efficient bio-remediation of PAHs contaminated soil.The main conclusions are as follows:(1)The physicochemical properties of rice husk,cotton stalk,straw,Chinese fir and bamboo charcoal were compared,including element content,surface functional groups,persistent free radicals,specific surface area and pores.We found that rice husk biochar(DK)and cotton stalk biochar(MG)Zeta potential is higher than other three types:-19.20 mV and-36.00 mV respectively,which is beneficial to the adsorption of microorganisms.The specific surface area and pores of rice husk and cotton stalk biochar are also larger:51.34 m2/g,0.032 cm3/g and 25.22 m2/g,0.018 cm3/g respectively,which is suitable for the growth and development of microorganisms;therefore,preliminary selecting rice husk and cotton stalk as carriers for immobilized microorganisms.By comparing the results of microscopic examination and degradation rate of biochar immobilized bacterial under different preparation conditions,the best preparation conditions of loading most microorganisms and best degradation effec were:30?80 mesh biochar,immobilization temperature 30?,the inoculation volume was 2.9×108 CFU/mL,3%LB was used as the immobilization medium,and the immobilization time was 2 days.The degradation rates of phenanthrene prepared by cotton stalk and rice husk biochar immobilized bacteria under these conditions was 92.40%and 64.09%respectively within 16 h.(2)The cotton stalk and rice husk biochar immobilized bacteria agents were stored at 4?for 21 days,the degradation rate of phenanthrene was basically not reduced,which was 89.50%and 60.70%respectively.After storage at room temperature for 21 days,the degradation rate of phenanthrene by cotton stalks and rice husks reduced to 52.98%and 35.60%respectively.This indicates that the biochar immobilization bacteria agent has prolonged the survival time of microorganisms to a certain extent.(3)Compared with biochar,immobilized bacteria has faster degradation rate and the better degradation effect.The degradation rate of immobilized bacteria based on cotton stalk biochar for phenanthrene and anthracene was 11.63 mg/(L·h)and 3.19 mg/(L·h)respectively,the removal rates of phenanthrene and anthracene was 45.44%and 30.91%higher than cotton stalk biochar respectively.The degradation rate of phenanthrene and anthracene by rice hull biochar immobilized bacteria was 7.92 mg/(L·h)and 1.87 mg/(L·h)respectively after 16 hours of application,the removal rates of phenanthrene and anthracene was 40.16%and 24.43%higher than rice husk biochar respectively(4)The degradation effects of different remediation experiments on artificially contaminated soil(RG)and Tianjin actual site soil(TJ)are as follows:immobilization bacteria based on cotton stalk biochar>immobilization bacteria based on rice husk biochar>cotton stalk biochar>rice husk biochar>free bacteria,and the degradation effect of RG soil is slightly higher than that of TJ soil,and the removal rate of phenanthrene in soil was higher than that of anthracene.The degradation rate of phenanthrene and anthracene in RG soil remedied by cotton stalk biochar immobilized bacteria was 39.94%and 29.47%respectively,the degradation rate of phenanthrene and anthracene was 42.54%and 18.33%in 42 days of TJ soilThis paper studies the preparation and optimization of biochar immobilized bacteria,which provides data support and theoretical basis for the efficient application of biochar immobilized bacteria in soil.The biochar immobilized bacteria was applied to the PAHs contaminated soil,which verified that the biochar immobilized bacteria still has degradation activity in the actual soil environment,and provided good bio-remediation functional materials for the restoration of polycyclic aromatic hydrocarbon contaminated soil.