Fundamental mechanisms of phosphate stabilization in granular waste materials
- Univ. of New Hampshire, Durham, NH (United States)
Phosphate minerals are known to be both geochemically stable and very insoluble. Consequently, orthophosphate has been considered to be an excellent chemical stabilization agent for immobilizing divalent metal cations in waste materials. We are presently involved in fundamental research on one commercial system used for a variety of wastes. A number of bulk and surface spectroscopic techniques were used to identify reaction mechanisms and reaction products. The Dutch Availability Leaching test was used to generate leached solids. pH-dependent leaching and the geochemical thermodynamic equilibrium model MINTEQA2 was used to model solid phase control of leaching. For lime-based dry scrubber residues from a U.S. waste-to-energy facility, the data suggests that the immobilization mechanisms are surface-based or discrete solid precipitation rather than surface sorption/ion exchange. Results to date also show that apatite family minerals (for Ca, Cd, and Pb) and tertiary metal phosphates (for Zn, Cu, and Cd) are dominant reaction products; these insoluble phases remain after aggressive leaching. Research is continuing on slags, contaminated soils, furnace dusts, and smelter dusts.
- OSTI ID:
- 370028
- Report Number(s):
- CONF-960376--
- Country of Publication:
- United States
- Language:
- English
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