The influence of chalcopyrite, galena and pyrite on the selective extraction of zinc from base metal sulphide concentrates

Multi-mineral complex sulphide ores would, typically, not respond well to conventional single mineral flotation due to their fine grained nature. Thus, many complex ore deposits remain undeveloped due to a lack of alternative economic treatment scenarios. The selective leaching process that has been explored is capable of selectively extracting zinc from concentrates containing both sphalerite and chalcopyrite. Unfortunately, many complex sulphide concentrates may also contain appreciable levels of pyrite and galena. Understanding the influence of these mineral on the leaching system is critical to developing a selective leaching process that is easily adapted to a wide variety of concentrate materials. Based on these considerations the selective extraction of zinc using pressure oxidation from multi-mineral concentrates was investigated. Concentrates were artificially produced from pure minerals and ranged in composition of: 25-100% by weight sphalerite, 5-75% chalcopyrite, 0-75% pyrite and 0-75% galena. Zinc was selectively extracted from several Cu/Zn concentrates by utilizing various combinations of temperature and oxygen concentration in the pressure leaching process and the influence of the additions of pyrite and galena was defined. It was discovered that addition of only 5% by weight galena to the selective leaching system retarded the dissolution of sphalerite by up to 13%. Alternatively, a 10% pyrite addition increased zinc extractions while simultaneously decreasing the copper extractions, however, increased concentrations resulted in increased copper extraction and thus, decreased zinc selectivity. (C) 1997 Published by Elsevier Science Ltd. All rights reserved.