Flotation in acid mine drainage control: Beneficiation of concentrate

This paper is focused on recovering residual sulfide minerals by flotation from the tailing of the Pyhäsalmi Cu-Zn mine in Finland. The tailing contains 4–8% sulfide sulfur and according to the static test it is strongly acid producing, having a low ratio of neutralization potential to acid production potential (NP/AP < 1). The NP/AP ratio could be markedly improved (> 1) by flotation treatment of the tailing. Fine pyrite caused sulfide losses in the flotation while incomplete liberation had only a minor effect on the acid production potential. The cleaner concentrate obtained during the flotation of the tailing contained 33% sulfur, 1% zinc, 0.7% copper, 2.8 g/t gold, and 40 g/t silver. Potential process options are available today for partial beneficiation of the concentrate but further development work is needed for recovering all the valuable elements and eliminating the waste pile.