Recovery of pyrite from copper tailings by flotation

Tailings that are generated in the copper concentrate production contain great amount of sulfide mineral, in particular pyrite. Pyrite in contact with water and oxygen might oxidize spontaneously and originates a serious environmental problem. In this article the recovery of pyrite before storing it in the tailing deposit to produce pyrite concentrates of economic interest, and to avoid the generation of acid mine drainage-AMD when transforming an acid tailing into a neutral tailing is proposed. The effect of conditioning time, pH, collector and frother dosage, and a number of flotation stages on grade and recovery of pyrite were studied at laboratory scale, using a fresh tailing sample collected in a concentrator plant from the Atacama Region, Chile. Furthermore, a continuous flotation circuit at laboratory scale was designed, which was evaluated on an industrial scale. The flotation circuit was designed using mathematical simulation by means of the “Split Factor” technique. The results obtained both at laboratory and industrial scale showed that it is possible to produce concentrates with a pyrite grade over 90% and recoveries over 70% in a flotation circuit that includes rougher–scavenger–cleaner and recleaner stages. To achieve this grade and recovery of pyrite, it is only necessary to condition the fresh tailings with 30 g/t of collector, 20 g/t of frother, 10 min of conditioning time, adjust the pH to 8 and set the flotation time for the rougher–scavenger–cleaner and recleaner stages in 10, 10, 10, and 5 min, respectively.