Reduction-enhancing Effect Of Composting DOM On Heavy Metals

DOM is the most active part of compost organic matter.It has a variety of redox functional groups,which enable it to have electron transfer capabilities.It can be used to repair and improve soil,accelerate the transformation of pollutants and improve soil physicochemical properties.characteristic.In this study,different compost samples（chicken manure,pig manure,cassava residue,kitchen waste,sludge,silkworm excrement）were collected to analyze their physical and chemical properties,and the composition and structure of DOM were characterized by spectroscopy,and the electron transfer ability was electrochemically characterized.,the reduction capacity characterizes the reduction enhancement effect on heavy metals,and the key factors affecting the reduction effect of heavy metals are analyzed by correlation.Compared with lignin-rich DOM（cassava residue,kitchen waste）,animal manure DOM（chicken manure,pig manure,silkworm excrement）has higher SUVA₂₅₄,SUVA₂₈₀,SUVA₄₃₆,lower E₂₅₀/E₃₆₅,E₂₈₀/E₄₇₂,Higher maturity and more oxygen-containing functional groups.Peat DOM contained more carboxyl groups,and sludge DOM contained more hydroxyl groups.DOM can be divided into 3 types of humus components and 1 type of protein components,among which the content of humus-like substances in pig manure DOM is the highest.The EDC of cassava residue DOM was the highest at 231.55μmol e^-/（g C）,and the EAC of sludge DOM was the highest at-338.86μmol e^-/（g C）.Pig manure DOM had the highest NRC and CRC,while cassava residue DOM had the lowest NRC and CRC.Sludge and silkworm excrement DOM have a better reduction and strengthening effect on Cr⁶⁺and Fe³⁺in the early stage.Correlation analysis showed that the heavy metal reducing ability of DOM was significantly positively correlated with SUVA₂₅₄,SUVA_280,SUVA₄₃₆,and significantly negatively correlated with E₂₈₀/E₄₇₂.With the progress of the composting process,the SUVA₂₅₄,SUVA₂₈₀,and SUVA₄₃₆ of the sludge DOM continued to increase,the content of quinone groups increased,the content of polysaccharides continued to decrease,the protein components decreased with the composting process,and the humus-like components increased.Increase,indicating that the maturity is deepening.The EDC of DOM is decreasing,the EAC is increasing,and the ETC is increasing.The NRC and CRC of sludge DOM decreased first and then increased.The removal rate of Cr⁶⁺by MR-1 and DOM is increasing,and the initial material DOM has the best effect.Correlation analysis showed that the heavy metal reduction ability of sludge DOM was related to E₂₈₀/E₄₇₂and E253/E203.Similar to the situation of sludge DOM,the overall trend of SUVA254,SUVA280 and SUVA₄₃₆ of silkworm excrement DOM in the four stages increased again,the content of polysaccharides and hydroxyl groups continued to decrease,and the protein components decreased with the composting process,while the humus-like group The points are increasing,and the silkworm excrement DOM maturity is deepening.The EDC of silkworm excrement DOM is on the rise,the EAC is on the decline,and the ETC is decreasing.The general trend of NRC and CRC of silkworm excrement DOM is similar,showing an increasing trend.The reduction rate of Cr⁶⁺by MR-1 and DOM increased continuously,and the effect of DOM was the best during the heating period.Correlation analysis showed that DOM’s ability to reduce heavy metals was related to SUVA₂₅₄,SUVA₂₈₀,SUVA₄₃₆,3430 cm^-1/1620 cm^-1.