Study On Elution Of Heavy Metals And Brominated Flame Retardants In Compound Contaminated Soil

With the development of society and economy,the generation of large amounts of electronic waste and its improper recycling have caused a large amount of heavy metals and polybrominated diphenyl ethers to enter the soil environment,causing compound pollution.The compound pollution of soil will directly or indirectly cause great harm to the ecological environment and human health,so it is of great research significance to carry out the compound pollution remediation of heavy metals and organic pollutants in the soil.The chemical leaching repair technology has a relatively short period,significant effect,and low cost,and has been maturely applied in actual site repair.In this study,several surfactants were used as the eluent,and the heavy metal Cu and the bromine flame retardant BDE209 were used as the removal objects.The eluent that can elute the heavy metal and the bromine flame retardant at the same time was selected through a balanced oscillation experiment.In order to provide a reference basis for the remediation of compound contaminated soil,the main research results are as follows:(1)Brij35,humic acid,Triton 100,LED3A,and saponin have a certain elution effect on Cu and BDE209 composite contaminated soil.When the concentration of the eluent is 10 g/L,The elution rates of Brij35,Humic Acid,Triton 100,LED3A,and Saponin to Cu were 60.13%,67.16%,77.09%,59.23%,and 55.42%respectively,and the elution rates to BDE209 were 50.68%and 28.23,respectively.%,46.4%,44.24%,26.65%.Taken together,LED3A has the best elution effect on compound contaminated soil.LED3A is a derivative of chelating agent EDTA,but the chelating ability of LED3A to heavy metals is superior to that of EDTA.(2)The adsorption kinetics of LED3A on Quzhou red soil is characterized by two stages of fast adsorption stage and slow adsorption stage,and the adsorption tends to balance after 12 h.The kinetic equation fitting results show that the adsorption process of LED3A on soil is most consistent with the quasi-second-order kinetic model.The elution process of LED3A for single Cu pollution,single BDE209 pollution and Cu-BDE209 composite pollution all conforms to the quasi-second-order kinetic equation,indicating that the elution process of LED3A for single Cu,single BDE209 and Cu-BDE209 composites is a chemical reaction process.The morphological analysis of the heavy metals in the soil before and after elution revealed that the percentage of acid extractable state in the soil after LED3A elution decreased significantly,from 75.98%to 38.23%,and the residue state increased significantly,from 12.54%to 49.56%.(3)The elution rate of Cu and BDE209 in the compound contaminated soil increases with the concentration of LED3A.The optimal elution concentration is 5 g/L.At this time,the elution rates of Cu and BDE209 are 80.12%and 46.45%respectively.The pH value has a greater influence on the elution rate of BDE209,and the pH value has a smaller influence on the elution rate of Cu.At pH values 8 and 12,the elution effect is better.The elution rates are Cu 79.16%and BDE209 49.80%,and Cu 72.49%,BDE209 49.80%.The increase of the water-soil ratio and the increase of temperature are beneficial to the increase of the elution rate of Cu and BDE209.The optimal water-soil ratio is 1:40 and the optimal temperature is 35?.