IMMOBILIZATION MECHANISMS OF Cr AND Pb IN CEMENT SOLIDIFIED MUNICIPAL SOLID WASTE INCINERATION FLY ASH

摘要

The objective of this study is to investigate the mechanisms of solidification/stabilization on municipal solid waste incinerator (MSWI) fly ash using cement. The process was conducted on samples prepared from MSWI fly ash, cement and water (water/solid weight ratio = 0.31), among which cement replaced the MSWI fly ash at the ratio of 20% by dry weight. Then, the specimen was subject to Toxicity Characteristic Leaching Procedure and X-ray diffraction. It was shown that the solidified MSWI fly ash can meet the landfill standard imposed by US EPA after 7 days of curing, and the main hydration products were C-S-H phases and ettringite, which have a positive effect on heavy metals retention. Finally, the possible solidification/ stabilization mechanisms of Pb and Cr were confirmed by sequential chemical extraction and continuous acid extraction.