Effect Optimization and Mechanism Analysis of Multi-component Chelating Agent for Typical Heavy Metals in Fly Ash.

In view of the high concentration of heavy metal in fly ash produced by a municipal solid waste incineration plant in Shenzhen, this paper based on the screening of various chelating agent components, and the response surface methodology was used to design the experiment. The effects of complex chelator on the chelation of Zn, Pb and Cd were evaluated by model fitting and variance analysis, and the chelating mechanism was analyzed by SEM, FTIR and XPS. The results showed that the combination of 2.5%(w) calcium superphosphate + 3%(w) sodium dimethyldithiocarbamate water agent, supplemented by 0.074%(w) sodium dodecyl benzene sulfonate, could achieve the best chelating effect and applicability for multiple batches of high concentration fly ash. Calcium superphosphate and sodium dimethyldithiocarbamate water agent had significant effects on the chelation of Zn and Cd, respectively, while Pb was affected by the antagonism of the two components. During the chelation and aging process, the components of heavy metals in the original ash were dissolved, crystallized and fixed: Zn was combined with phosphate, but aging at high temperature would reduce its chelating stability, Pb formed a stable compound with high valence, while Cd was mainly coated by the cross-linking group of organic chelating agent. [ABSTRACT FROM AUTHOR]