Institute TOMS, Irkutsk, Russia

A. E. Senchenko, CEO, e-mail: senchenko@tomsmineral.ru
A. V. Aksenov, Head of the Metallurgy Laboratory, Candidate of Technical Sciences, e-mail: aksenov@tomsmineral.ru
S. G. Rybkin, Senior Researcher, Candidate of Technical Sciences, e-mail: rybkin@tomsmineral.ru

Processing of concentrates from gravity and flotation enrichment of refractory gold-bearing ores using the technology of arsenatizing roasting with subsequent cyanidation of cinders allows, along with high extraction of precious metals into the target product, to radically reduce the volumes of formed sulfur oxides (SO₂, SO₃) and arsenic (As₂O₃) and reduce the costs of their neutralization. The technology includes roasting concentrates in a mixture with lime and calcium chloride at a temperature of 600–700 °C and access to atmospheric oxygen. During this process, the carbonaceous substance contained in the concentrate burns, the sulfide components are transformed into calcium sulfate CaSO₄ and calcium arsenate Ca₃(AsO₄)₂, and iron transforms into hematite Fe₂O₃. The flotation concentrate cinder is processed using the method of sorption cyanide leaching. The gravity concentrate cinder is enriched on a shaking table to obtain a primary gold concentrate and tails. The primary gold concentrate is melted to form ligature gold, and the table tailings are sent to sorption cyanide leaching. It has been established that during cyanidation of cinders from arsenatizing roasting of concentrates containing calcium arsenate, the arsenic content in solutions is within 0.5–3.0 mg/dm³, which does not correspond to the reference data on the solubility of Ca₃(AsO₄)₂ in water, which is 130 mg/dm³. Studies have been conducted on the synthesis of calcium arsenate by a hydrometallurgical method – precipitation from an arsenic acid solution with calcium hydroxide and by a thermal method – sintering crystalline arsenic acid with calcium hydroxide. It has been shown that the solubility in water of calcium arsenate obtained by a thermal method is an order of magnitude lower than for the compound synthesized by a hydrometallurgical method. This ensures safer utilization of cyanidation tailings from arsenatizing roasting concentrates of refractory gold-bearing ores. It is assumed that the significant difference in solubility in water for calcium arsenate synthesized by hydrometallurgical and thermal methods is explained by the higher energy of the crystal lattice of the compound obtained by the sintering method.

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