Study On The Degradation Of Pentachlorophenol Promoted By Landfill Humus

Landfill is the most important way to dispose of municipal solid waste(MSW)in the world today.In the process of municipal solid waste landfill,a large number of mineralized wastes will be accumulated in the landfill,and its sieve contains a large number of humus substances.Humus has redox ability because of its active functional groups.It can be used as an electronic shuttle to promote the degradation of organic pollutants,and then change the existing form of pollutants in the microenvironment and reduce its toxicity.However,at present,the composition and structure evolution of humus in different landfill stages and its ability to degrade pollutants are not clear,especially the study of landfill solid humus and mixed humus is less.In order to solve the above problems,domestic waste with different landfill years was collected,three different forms of humus were extracted and prepared,and the chemical structure of landfill humus was characterized by elemental analysis,fluorescence,infrared and nuclear magnetic resonance.The evolution of humus composition and structure during landfill was observed.The characteristics of landfill humus promoting PCP reduction and degradation were studied,the efficiency of PCP reduction and transformation of municipal solid waste landfill humus was explored,and the influence of landfill humus composition and structure on PCP reduction and transformation ability was analyzed.The research results are helpful to analyze the environmental effects of landfill humus on pollutants,and provide scientific basis for identifying the environmental risks of landfills and landfill humus as cheap soil remediation materials.The following results have been obtained:(1)The evolution rule of composition and structure of landfill humus was analyzed.it was found that the aromaticity of dissolved humus decreased and the molecular weight decreased with the increase of landfill depth in the initial stage of landfill,and the aromaticity increased with the increase of landfill depth in the intermediate and old stage of landfill.The landfill solid humus contains protein substances,fulvic-like acid substances and humic-like acid substances,and contains more aliphatic substances,carboxyl/carbonyl groups and humus-like substances at the initial stage of landfill.In the intermediate and old stage,aromatic structure and protein-like substances were dominant.The main carbon components in humic soil are alkyl carbon and aromatic carbon.The contents of protein-like substances and alkyl carbon are high in the initial stage of landfill,while humus-like substances,aromatic carbon and carboxyl carbon mainly appear in the intermediate and old stage of landfill.(2)Landfill humus can be used as an electron mediator to mediate the transfer of electrons between MR-1 and the final electron receptor,thus effectively promoting thereduction of PCP.Landfill humus has the ability of PCP reduction and transformation because its structure contains hydroxyl carboxyl quinone and other electron transfer functional groups.The content of landfill humus will affect the efficiency of PCP reductive dechlorination.Compared with the initial stage of landfill,dissolved humus and solid humus in the intermediate and old landfill can promote the deep dechlorination of PCP more effectively.The reason why landfill refuse can promote the microbial reductive dechlorination of PCP is the interaction of inorganic minerals and organic matter in landfill refuse,in which ferrous oxide,iron minerals and silicate minerals are the main inorganic minerals that affect the dechlorination of PCP.In this study,the effects of different forms of landfill humus composition and structure changes on the dechlorination of PCP were discussed,which promoted our understanding of the ability of landfill humus to degrade PCP.It provides a scientific basis for identifying the environmental risks of landfills and landfill humus as a cheap soil remediation material.