Dogan Paktunc,
CanmetMINING, Natural Resources Canada

Arsenic, a known human carcinogen, occurs in elevated concentrations in some gold and base metal ores. Mining and metallurgical processing of such ores results in solid wastes and effluents containing high concentrations of arsenic. These wastes form an important source of anthropogenic arsenic in the environment. The form and speciation of arsenic in wastes are complex and highly variable including occurrences as adsorbed species on Fe(III)-oxyhydroxides and as structural species in a wide range of compounds and minerals. In order to improve our understanding of the nature of the arsenical compounds forming from effluents and tailings pore-waters, a series of synthesis experiments were carried out in the Fe(III)-AsO4-SO4, Fe(III)-Ca-AsO4-NO3,Fe(III)-SO4 and Fe(III)-NO3 systems and the precipitates were characterized at the molecular scale by X-ray absorption spectroscopy and nanoscales by high-resolution transmission electron microscopy techniques. The characteristics of the precipitates and kinetics of their formation are fundamental to controlling and stabilization of arsenic in mine wastes and to developing efficient effluent treatment technologies. Characteristics of these compounds and their natural analogs will be presented along with implications on the stability of arsenic in mine wastes.