Environmental Aspects of Cu Recovery from Evaporative Solids on the Surface of Old Weathered Tailings: Sarcheshmeh Mine, SE Iran

Abstract

The enormous amount of water-soluble evaporative solids (about 150 t/ha) that has formed on the old weathered tailings in the semi-arid climate of the Sarcheshmeh area, in SE Iran, stores acidity and potentially toxic elements, such as Cd (8.8 ± 3.7 mg/kg), Co (242 ± 43 mg/kg), Cu (11,220 ± 3500 mg/kg), Mn (8400 ± 3400 mg/kg), Ni (176 ± 38 mg/kg), S (12.82 ± 1.01%), and Zn (2670 ± 880 mg/kg). We assessed the potential of recovering Cu from these evaporative solids and the likely environmental aspects of doing so. The total Cu concentrations ranged from 7380 to 17,850 mg/kg. The mean Cu concentration in the produced pregnant leach solution (PLS) was 13,210 mg/L, which after cementation reached 94.40 mg/L, corresponding to a Cu recovery efficiency of 99.2%. During the cementation process, the Fe concentration increased in the final barren solution (FBS). In addition to the positive environmental role of Fe in the co-precipitation of potentially hazardous trace elements, the pH range of FBSs was 4.02–4.17, which was higher than the pH range of the initial PLSs (pH 3.25–3.40). Thus, collecting evaporative solids from the surface of old-weathered tailings can provide valuable Cu and improve the quality of the tailings pond recycling water by reducing the risk of diminishing of water quality, especially during heavy rainfall events.