Arsenic stability in arsenopyrite-rich cemented paste backfills: A leaching test-based assessment

• Published in: Journal of hazardous materials Vol. 185; no. 2; pp. 1467 - 1476
• Main Authors: Coussy, Samuel, Benzaazoua, Mostafa, Blanc, Denise, Moszkowicz, Pierre, Bussière, Bruno
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 30.01.2011; Elsevier
• Subjects: Applied sciences; Arsenic; Arsenic - chemistry; Arsenicals - chemistry; Arsenopyrite; Binders; Cemented paste backfill; Cementing; Chemical engineering; Crystallization, leaching, miscellaneous separations; Exact sciences and technology; General treatment and storage processes; Iron Compounds - chemistry; Leaching; Microscopy, Electron, Scanning; minerals; Minerals - chemistry; neutralization; Other industrial wastes. Sewage sludge; oxidation; Particle Size; Pastes; Pollution; Quebec; Reactors; risk; Soil Pollutants - chemistry; Solubility; Sulfides; Sulfides - chemistry; sulfur; Tailings; Wastes; weathering; Canada; Quebec; Cemented paste backfill; Arsenic; Leaching; Tailings; Arsenopyrite; Stabilization; Waste treatment; Material weathering; Transport process; Fly ash; Weathering; pH; Lixiviation; Oxidation; Diffusion; Hydraulic binder; Chemical reactivity; Stability; Solubility; Portland cement; Dissolution; Industrial waste; Storage; Solid waste; Slag; Mining waste
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2010.10.070

Arsenic (As) is a toxicant in tailings from sulphur deposits. It represents an environmental risk because of its high solubility. Tailings can be mixed with water (typically 25%) and a low proportion of hydraulic binder (3–7%) to produce a cemented paste backfill (CPB), stored in underground mine openings. CPB is a tailings storage technique, but it could also provide environmental advantages by stabilization of polluting elements such as As. Tailings from Casa Berardi mine (QC, Canada) contain As (3800 ppm), mainly in arsenopyrite form. For this study, three different CPBs were synthesized in laboratory using Casa Berardi tailings and three different binders. These pastes were submitted to various leaching tests after 28 days of curing. The results indicate that As is released at higher concentration for a fly ash-based CPB than for slag- and Portland cement-based CPB. However, at lower pH, As is better stabilized in fly ash-based samples. These differences can be explained by a variation of solubility of As-compounds in each CPB. Several mechanisms of As release occur, as diffusion and/or dissolution/precipitation. The accelerated weathering test results show that sulphide reactivity is buffered by the neutralizing minerals contained in CPB, and influence the As release behaviour by decreasing the oxidation of As-bearing sulphides.