Mechanism Of Biochar Composite In Collaborationwith Microbial Dechlorination Of Groundwater

Chlorinated hydrocarbon pollution is an increasingly serious problem in groundwater pollution.In situ enhanced bioreduction technology is a cheap,efficient and promising technology.The restoration material is an important factor affecting the reduction and degradation of this technology,so the development of new technology has become a hot issue in this fieldIn this study,poly(lactic acid)and nano zero-valent iron were loaded onto biochar by solution intercalation method and liquid phase reduction method,and sodium lentisulfonate was used as modifier to prepare a composite material containing slow-release carbon source.The ratio of poly(lactic acid)to nano zero-valent iron and its application conditions were optimized.Through DNA-SIP technology and extinction dilution experiment,the mechanism and response of the microbial community to the degradation of chlorinated hydrocarbons in groundwater were discussed.The main conclusions of this paper are as follows:(1)By solution intercalation method and liquid phase reduction method,polylactic acid and nano zero-valence iron are evenly distributed on the surface of biochar without affecting the surface morphology and structure of biochar.At the same time,the functional modification of sodium linosulfonate improves the hydrophilicity of biochar based composite material,making the composite disperse in the reaction system more lasting.(2)According to the optimization experiment of composite components,the ratio of nano zero-valent iron,biochar and polylactic acid in the composite is 2:8:1,and the pH of the optimal application of the composite is 7.Under the optimal culture conditions,the maximum degradation rate of the composite in the degradation system with iron-dissimilar reducing microorganisms is 94.37%.The composite can remove1,2-TCA at different concentrations and has good degradation effect after 30 days of natural placement(86.15%).(3)DNA-based SIP was used to study the removal of 1,2-TCA functional microorganisms by composite materials in coordination with groundwater medium microorganisms.The results show that at the initial stage of the reaction,the composite material can rapidly remove 1,2,TCA in the reaction system through the reductive property of zero-valent iron nanoparticles.At the same time,the iron oxide layer covered on the surface of the composite material is converted to the adsorbed state of Fe(Ⅱ)due to the dissimilar iron reduction microbial action,so that the zero-valent iron nanoparticles covered by the iron oxide layer are exposed.And it goes on to react with 1,2-TCA.At the middle and late stage of the reaction,a large number of dechlorinated respiratory bacteria grew in the system and continued to remove 1,2-TCA from the reaction system through dechlorination respiration.