REMOVAL OF ARSENIC FROM ENARGITE RICH COPPER CONCENTRATES

Abstract

Arsenic is a troublesome impurity in copper concentrates where it is usually present as enargite (CU3AsS4). When the enargite content is high in the concentrates, they cannot be treated by direct smelting processes because of the high risk of arsenic emissions to the atmosphere. In this work, some experimental results are presented on a novel alternative process to remove selectively the arsenic from an enargite rich copper concentrate. The process includes an alkaline (Na2S-NaOH) baking step followed by leaching with water. The experimental results showed that temperature and Na2S concentration are important variables in the baking step for efficient arsenic removal. In experiments using a chalcopyritic copper concentrate containing 2.2% arsenic as enargite. 94% of the arsenic was removed when the concentrate was baked at 85°C for 10 min by using 2.5 times the stoichiometric Na2S requirement for arsenic dissolution. Copper dissolution was negligible under these conditions.