The Characteristics Of Organically Complex Heavy Metals In Leachate And Their Removal Techniques By Breaking Complexes

The increasing living standards have led to the generation of a large amount of household waste,while the majority of household waste is still treated using traditional landfill methods,resulting in the generation of a large amount of leachate.The composition characteristics of leachate change with different landfill time,landfill methods,and types of landfill waste,with the most important influencing factor being landfill time.Heavy metals are non-negligible pollutants in leachate,with carcinogenic,teratogenic,and mutagenic properties,and cannot be biodegradable.At the same time,due to the presence of various functional groups in the dissolved organic matter in the leachate,heavy metals can complex with it to form organic complex heavy metals.Compared to free heavy metals,organic complex heavy metals have higher mobility and are more difficult to remove by traditional heavy metal removal processes.In order to effectively remove complex heavy metals from leachate,this study investigated the composition characteristics of landfill leachate at different landfill times and their complexation behavior with heavy metals.Finally,a green and pollution-free manganese based material was developed to remove complex heavy metals.The main content and innovative points of this study are as follows:（1）Taking landfill leachate from different landfill times around Beijing as the research object,the evolution laws of organic components in leachate were elucidated using techniques such as UV visible spectroscopy,synchronous fluorescence spectroscopy,three-dimensional fluorescence spectroscopy,and Fourier transform infrared spectroscopy,combined with two-dimensional correlation spectroscopy analysis and parallel factor analysis.It was found that with the increase of landfill time,the macromolecular protein substances in the leachate were decomposed into small molecule humic acid substances and further mineralized,and the degree of aromaticity and humification of the leachate was further reduced.（2）Conduct quenching titration experiments on heavy metals and soluble organic matter in landfill leachate at different landfill times to explore the complexation behavior characteristics of soluble organic matter and heavy metals in landfill leachate at different landfill times.It was found that with the increase of landfill time,the priority binding degree between organic matter and Cu（II）in the leachate gradually weakens,while the susceptibility of protein like substances slightly increases;In fresh and middle aged leachate,microbial humus preferentially binds to Cu（II）,and in aged leachate,proteoid preferentially binds to Cu（II）;The order of binding between functional groups and Cu（II）in leachate DOM is dissociated hydroxyl group>lactone group>phenolic hydroxyl group（3）Silicon regulated manganese based materials were prepared by hydrothermal method using silicon containing precursors to efficiently remove complex heavy metals.Compared to traditional manganese based materials,silicon regulated manganese based materials have smaller particle sizes and better catalytic performance.The catalytic performance of silicon regulated manganese based material activated PMS（persulfate）for removing Cu-EDTA was improved by 150%,and 12.8 mg/L of Cu-EDTA could be completely removed within 50 minutes.The successful preparation of silicon regulated manganese based materials was demonstrated through SEM and XRD.The higher electron donating ability of silicon regulated manganese based materials was verified through CV cyclic voltammetry testing and electrochemical impedance testing.The good stability of Si Mn O2 was demonstrated through the dissolution of manganese ions in the reaction system and cycling experiments.By measuring the XPS of silicon regulated manganese based materials before and after the reaction,it was found that there is an electron transfer process on the surface of manganese based materials during the reaction process.Through free radical masking experiments,EPR,etc.,it has been proven that in the process of removing Cu-EDTA from PMS activated by Si-Mn O₂,the main role is played by ¹O₂and^·O^2-.The mechanism of silicon regulating the persulfate system of manganese based materials is mainly non free radical mechanism.