Formation and Durability of Dithiocarbamic Metals in Stabilized Air Pollution Control Residue from Municipal Solid Waste Incineration and Melting Processes

Abstract

In Japan, chemical stabilization of metals using a chelating agent composed of dithiocarbamic salt is the prevailing technique for the final disposal of air pollution control (APC) residue from municipal solid waste (MSW) incineration and melting processes. The objective of this study is to quantitatively evaluate the formation and durability of dithiocarbamic metals (DCM) in treated APC residue. In this research, sodium N,N--diethyldithiocarbamate trihydrate was used as a chelating agent. An extraction method using n-butyl acetate was developed to separate DCM from residue. This method elucidated the competitive formation of DCM among Cu, Pb, Cd, and Zn. The metal fraction forming DCM was about 70 and 90% of the total content of Pb in APC residue from incineration and melting, respectively. Regarding durability in the environment, 240 day curing of the chelate-treated APC residue showed that air-contact conditions induced degradation of DCM with time. On the other hand, sealed conditions did not bring about a decrease over the course of the experiment. These results imply that DCM degradation proceeds when the treated residue comes into contact with air in actual landfills.