A leaching process for removing arsenic from enargite-bearing copper concentrates

摘要

A process for leaching enargite with ClO~- media is presented, which can selectively remove arsenic from copper concentrates at room temperature, low reagent concentrations (0.2-0.7 M ClO~-, pH 12-12.5) and very low residence times ( < 30 min). The process is described by the following reaction: Cu_3AsS_4 + 11OH~- + 35/2 ClO~- → 3 CuO + AsO_4~(3-) + + 4SO_4~(2-) + 11/2 H_2O + 35/2 Cl~- While copper remains in the solid residue as CuO, arsenic forms soluble arsenate, which can subsequently stabilized by precipitation. This process has been applied on an enargite/chalcopyrite concentrate (34% Cu, 2% As, 31% S, 26% Fe); the most favourable conditions were: pH 12-12.5, [ClO~-] 0.13-0.33 M, do < 25 μm and 25-40℃, leaving < 0.3% As in the residue, This process was also applied to a Mansa Mina concentrate (Chuquicamata, Chile) (18% Cu, 3.6% As, 6.1% Fe) formed by pyrite, enargite and chalcocite as majority phases and tennantite and few amounts of chalcopyrite as minority components. The best conditions were similar to those found for the enargite-chalcopyrite concentrate. The amount of arsenic in the residue was 0.85%. This paper reports on the behaviour of several minerals, commonly found in copper concentrates, when subjected to the proposed leaching process. Selenium and tellurium forming copper sellenides and Au/Ag tellurides also dissolved, and this facilitates obtaining pure copper or silver/gold concentrates.