Chemically bonded phosphate ceramics for low‐level mixed‐waste stabilization

Abstract

Novel chemically bonded phosphate ceramics are being developed and fabricated for low‐temperature stabilization and solidification of mixed‐waste streams that are not amenable to conventional high‐temperature stabilization processes because volatiles, such as heavy‐metal chlorides and fluorides, and/or pyrophorics are present in the wastes. Phosphates of Mg, Mg‐Na, and Zr are being developed as candidate matrix materials. In this paper, we present the fabrication procedures for phosphate waste forms with surrogate compositions of three typical mixed‐waste streams, namely ash, cement sludges, and salts. This study was focused, but not limited to, magnesium phosphate‐ash wastestream final waste form. The performance of the final waste forms, such as compression strength, leachability of the contaminants, and durability in aqueous environments were conducted. In addition, parametric studies have been conducted to establish the optimal ash waste loading in the magnesium phosphate binder system. Based on the results, we present potential applications of phosphate‐bonded ceramics in the treatment of various mixed‐waste streams.