Sulfide leaching of high-grade arsenic copper concentrates

Abstract

Such factors as lower-grade copper ores, more demanding mining and technical conditions, and higher implementation costs for new development projects are typical for the Ural region in general and for the Uchalinsky Mining and Processing Plant (Uchalinsky GOK), developing tennantite-containing copper-sulfide ore reserves, in particular. Depending on the process flow design and the mineral composition of the ore, 10–70 % of arsenic is transferred into copper concentrates. The mass fraction of arsenic in the resulting copper concentrates may reach 2 %, significantly reducing the concentrate grade. Sulfide-alkaline leaching has been studied as a promising conditioning method for flotation copper concentrate. It ensures more effective arsenic removal and compliance of the final product with the requirements for further pyrometallurgical processing. The studies were carried out using a low-grade high-arsenic concentrate sample from the Uchalinsky GOK containing 16.04 wt. % Cu, 5.30 wt. % Zn, 1.36 wt. % As, and 0.19 wt. % S. It has been established that iron is predominantly occurring in the form of pyrite, with chalcopyrite and sphalerite unevenly distributed in its mass. The concentrate had high concentrations of fahlore minerals (tennantite, etc.). Studies were conducted to assess the effects of changes in the sulfide leaching process parameters (temperature, raw material size, NaOH and Na2S concentrations, solid-liquid ratio, duration) on the transfer of arsenic into the alkaline solution. The specific conditions have been established (t = 95 °C; Cm(NaOH) = 3.5 M, Cm(Na2S) = 1.5 M; solidliquid ratio = 5; duration of three hours or more) that ensure almost complete removal of arsenic from the flotation concentrate to obtain a conditioned copper product meeting the requirements of GOST R 52998-2008.