Stabilization/Solidification of Hazardous Metals from Solid Wastes into Ceramics

Safe management of hazardous metals deriving from solid wastes constitutes an important environmental challenge. In the present study, recent progress in the stabilization/solidification of heavy metals from various solid wastes into ceramics and glass-ceramic materials is reviewed. Coal/lignite-fired power plant fly and bottom ashes, steel industry by-products, metallurgical and urban/municipal wastewater sludge, and pharmaceutical wastes are included. The environmental behavior of the ceramics produced is studied via several leaching tests and ecotoxicological analyses. The goal is to assess the potential of these materials for retention of pollutants into their microstructure, for safe use as building materials. These objectives are in line with green chemistry and sustainable development principles. Moreover, the aim of turning waste into useful feedstock for another industrial sector towards symbiosis, ample coordination, and circular economy, is strongly encouraged by current environmental policies. Such secondary resources can be considered as substitute materials in ceramics production, as they contain useful oxides. However, the presence of heavy metals remains a significant environmental issue. Possible leaching of pollutants caused by rain from construction materials incorporating solid wastes would lead to contamination of surface and subsurface water, thus raising critical environmental concerns. Inertization of potentially hazardous metals into environmentally-friendly ceramics and glass-ceramics is shown to be feasible, as concentrations of these elements in the leachates remain within acceptable limits. Certainly, this also depends on the leaching method employed and system parameters. In conclusion, stabilization of these elements into ceramic matrices can be an effective and beneficial alternative for protecting human health and the environment.