Geochemical stability of vitrified glass prepared from arsenic trioxide roaster waste from the Giant Gold Mine (Yellowknife, NT)

Abstract

This study evaluated the geochemical stability of three ATRW-based glasses, containing 5 wt.% As (G5), 10 wt.% As (G10), and 15 wt.% As (G15), using selective extraction protocols. Micro X-ray fluorescence (µ-XRF) maps incorporated with micro-X-ray absorption near edge spectroscopy (µ-XANES) and bulk XANES across the As K-edge were collected to determine the distributions and oxidation number of As within the glasses. Antimony K-edge XANES were collected to determine oxidation number of Sb within the glasses. Uncrushed or crushed subsamples were immersed into solutions to target the potential for dissolution of the vitrified glasses under different environmental characteristics, including phases associated with water-soluble, cation/anion exchangeable, weak-acid extractable, amorphous-to-poorly crystalline, oxidizable, and strong-acid leachable. No discrete particles of ATRW were observed in the µ-XRF maps. Results of XANES analysis across the As K-edge and the Sb K-edge suggests G5 mainly contains oxidized As and Sb phases, whereas G10 and G15 contain up to 30% of As(III) and Sb(III), respectively. Water-soluble extractable As concentrations from the glasses (<0.001 g L^-1) were all ¹0⁴ times lower than from the ATRW in water at 25 °C (10 g L^-1). Limited As release (<0.025 mg g^-1 per mass of glass) from the glasses occurs in solutions targeting exchangeable phases. Release of As increases in more acidic solutions (pH< 3), especially in solutions targeting amorphous-to-poorly-crystalline phases. Crushed glasses leach commensurately higher masses of As. The results of this study indicate that vitrifying ATRW decreases its solubility and associated As release.