Phosphate stabilization of municipal solid waste combustion residues: geochemical principles
T. Taylor Eighmy, J. Dykstra Eusden, Jr., 2004. "Phosphate stabilization of municipal solid waste combustion residues: geochemical principles", Energy, Waste and the Environment: a Geochemical Perspective, R. Gieré, P. Stille
Download citation file:
The use of orthophosphate as a chemical stabilization agent for municipal solid waste (MSW) combustion residues is widespread in Japan and North America. The application of this technology to MSW ashes generally parallels its use with other metal contaminated wastes (e.g., soils, sediments, smelter dusts, slags, wire chopping wastes, mine tailings), especially Pb-contaminated soils. The technology relies on the fact that forms very insoluble and stable minerals for a variety of divalent metal cations (e.g., Pb, Cd, Cu, and Zn). Extensive data from phosphate-treated contaminated soil systems suggest that stabilization involves surface immobilization reactions involving sorption, heterogeneous nucleation and surface precipitation, and/or solution phase precipitation involving homogeneous nucleation and precipitation. A geochemical basis for use of in ash systems is presented with a focus on the wide theoretical pH distribution, pH-pE predominance and redox stability of Cd, Cu, Pb, and Zn phosphates within complex bottom ash pore water systems. Stabilization mechanisms in bottom ashes, scrubber residues, and vitrification dusts are similar to those observed in soil systems. Some longer term leaching behaviour of phosphate-stabilized ashes are presented. The roles of Ostwald ripening, solid solutions (e.g., (Pb,Ca)5(PO4)3OH), and kinetically controlled reaction pathways probably are more important than what is presently envisioned in phosphate-stabilized ash systems.
Figures & Tables
This book provides incentives for further development of sustainable fuel cycles through a novel and interdisciplinary approach to an Earth science-related topic. The main focus is on geochemical concepts in immobilizing, isolating or neutralizing waste derived from energy production and consumption. The book also addresses the issue of using some types of energy-derived waste as alternative raw materials. Moreover, it highlights research on how certain wastes can be used for energy production, an increasingly important aspect of modern integrated waste management strategies. The main objectives are to: (a) identify the most serious environmental problems related to various types of power generation and associated waste accumulation; (b) present strategies, based on natural analogue materials, for the immobilization of toxic and radioactive waste components through mineralogical barriers; (c) discuss modern procedures for reuse of waste or certain waste components; and (d) review the importance of geochemical modelling in describing and predicting the interaction between waste and the environment.