Chemically bonded phosphate ceramics for low-level mixed waste stabilization

Abstract

Novel chemically bonded phosphate ceramics (CBPCs) are being developed and fabricated for low-temperature stabilization and solidification of mixed waste streams which are not amenable to conventional high-temperature stabilization processes due to presence of volatiles such as heavy metal chloride and fluorides and/or pyrophorics in the wastes. Phosphates of Mg, Mg-Na and Z r are being developed as candidate matrix materials. In this paper, we present the fabrication procedures of phosphate waste forms using surrogates compositions of three typical mixed wastes streamsash, cement sludges, and salts. The performance of the final waste forms such as compression strength, leachability of the contaminants, durability in aqueous environment were conducted. In addition, parameteric studies have been conducted to establish the optimal waste loading in a particular binder system. Based on the results, we present potential applications in the treatment of various mixed waste streams.-* Work supported by US. Department of Energy, Office of Technology Development, as part of the Mixed Waste Integrated Program, under Contract W-3 1-109-Eng-38.

Erosion of Magnesium Potassium Phosphate Ceramic Waste Forms

“…Resultant composite products, which can incorporate ash, slag, low-level nuclear wastes, or other hazardous inorganic or organic materials, have been subjected to tests of stability in aqueous media [15,16] and found to be highly resistant to leaching [2][3][4][5][6], For these studies, we fabricated 2-cm-diameter MKP-based test samples that incorporated 50 or 60 wt.VO Class C or Class F fly ash, or 65 wt. 'Mo steel-mill slag.…”

“…For example, approximately one-third of the ash produced by utilities is recycled as an additive to cements [1]. Phosphate-based cements have advantages over Portland cements because they can incorporate substantially higher ash loadings and can form strong products from ash having wide ranges of chemical compositions [2][3][4][5][6].…”

“…Final ash-containing Ceramicrete products exhibit high strength and little open porosity. They are therefore suitable for many potential applications [2][3][4][5][6].…”

Improvement of ground granulated blast furnace slag on stabilization/solidification of simulated mercury-doped wastes in chemically bonded phosphate ceramics

“…Addition of a small amount (<1 wt.%) of sulfide like K 2 S in the binder mixture was recommended to get a better stabilization performance [2,17]. From Fig.…”

Stabilization of NaCl-containing cuttings wastes in cement concrete by in situ formed mineral phases

“…The ability of phosphate ceramics to form at low temperature is of great interest, since volatile components such as chlorides, fluorides and heavy metals present in waste cannot be brought up to the usually high temperatures required in classical stabilization and solidification processes [13]. Nzihou et al have developed a process of fly ash stabilization consisting in a chemical treatment with phosphate followed by a thermal treatment [14], leading to a pyromorphitelike compound.…”