An Alternative to Calcium Sulfoaluminate System for Immobilization of Heavy Metals

Kwang-Suk You 1) , Dong-Yun Han 1), Gi-Chun Han 1), Nam-il Um 1),

Ji-Whan Ahn 1), and Hee-Chan Cho 2)

1. Minerals and Materials Processing Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 305-350, Korea

2. Department of Civil, Urban and Geosystem Engineering, Seoul National University , Seoul , 139-701, Korea

The calcium sulfoaluminate phase is used as civil or construction material. The hydration of calcium sulfoaluminate with calcium hydroxide, calcium sulfate and water forms ettringite as hydration product. E ttringite is a hydrate with many advantages in a solid solution of heavy metals, because e ttringite possesses the ability to behave as a host for metallic pollutants to immobilize both cationic and anionic waste ions through sorption, phase mixing and substitution; the ions available for substitution are Ca 2+ , Al 3+ , SO 4 2- and OH - .

In the previous study, a pretreatment process and optimal combination for raw material was developed to a measure of synthesis technology related to a synthesis of calcium sulfoaluminate phase from inorganic wastes. In this study, the effects of trace elements and heavy metals possibly held in the waste on the properties of calcium sulfoaluminate was examined, and the solid solution(solidification) behavior of heavy metals in calcium sulfoaluminate hydration reaction, which forms the ettringite, was investigated in order to evaluate its applicability as a solidifier for a second solidification of other types hazardous waste,