Patterns of heavy metal immobilization by MSW during the landfill process

Simulated landfill was established and operated for 507 days to explore the pattern of heavy metal immobilization by municipal solid waste (MSW) in the landfill process. The results showed that 45.6 mg of Cu, 3.16 mg of Pb, and 44.2 mg of Zn were immobilized by 25 kg of MSW during the whole landfill process. The immobilization of Cu, Pb and Zn followed different patterns. Two peaks were found for the immobilization of Cu in the landfill process, which occurred at the initial stage and the acidification stage. The immobilization of Cu by MSW was more affected by the feed concentration than pH, and physical adsorption may control the immobilization. One peak was observed for the immobilization of Pb, which occurred at the initial stage of the landfill. The fluctuation of Pb concentration was similar to that of Cu. However, the immobilization of Pb was restricted due to the low feed concentration. No immobilization of Zn was observed at the initial stage of the landfill. The peak immobilization was observed from days 44 to 143 and at the acidification stage. Compared with Cu and Pb, the immobilization of Zn was more affected by pH, which might be due to their different speciation in the leachate, resulting from different affinities to dissolved organic matter. These results help to understand the migration of heavy metals in a landfill, which could provide insights for heavy metal pollution control in the landfill.