Carbonation of municipal solid waste incineration electrostatic precipitator fly ashes in solution

摘要

Carbonation was applied to a Pb- and Zn-contaminated fraction of municipal solid waste incineration electrofilter fly ashes in order to reduce heavy metal leaching. Carbonation tests were performed in solution, by Na_2CO_3 addition or CO_2 bubbling, and were compared with washing (with water only). The injection of CO_2 during the washing did not modify the mineralogy, but the addition of Na_2CO_3 induced the reaction with anhydrite, forming calcite. Microprobe analyses showed that Pb and Zn contamination was rather diffuse and that the various treatments had no effect on Pb and Zn speciation in the residues. The leaching tests indicated that carbonation using Na_2CO_3 was successful because it gave a residue that could be considered as non-hazardous material. With CO_2 bubbling, Pb and Zn leaching was strongly decreased compared with material washed with water alone, but the amount of chromium extracted became higher than the non-hazardous waste limits for landfilling.