Mineral-based treatment strategies for wastes and effluents

Potential treatments for local wastes (such as bag-filter dust and brine ash) containing soluble heavy metals and salts using a synthetic mineral immobilization technology are reviewed. The formation of metal hydroxyl salts, ettringite, zeolite, sodalite, apatite and spinel mineral phases from these wastes allows for the undesirable components to be contained in reservoir-type minerals that form an internal barrier, and the treated waste thus develops its own sealing property. These principles are illustrated by a few examples: the solid stabilization of incinerator ash and ferrochrome bag-filter dust, lime treatment of an industrial effluent, and the use of natural zeolites to minimize the emission of ammonia from agricultural wastes.