Process Decisions Focused on the Prevention of AMD Formation on Beneficiating Sulfide Minerals

Abstract

Acid Mine Drainage (AMD) from voluminous sulfide-bearing wastes contributes to the environmental burden of mineral processing. To diminish burden and its time frame of risk, the disposal of sulfidic waste materials is re-examined through the valuable distinction between reactive or active gangue materials contributing to AMD generation and largely unreactive passive gangue. In an example process for disposal of tails from mineral sulfide beneficiation, a proof of concept is provided for inclusion of a non-selective sulfide float preceding or following selective separation of the desired mineral sulfide. The environmental benefit of subsequent reduction of sulfide in the tailings from 3.7 to 0.2% on AMD generation potential is quantified through a combination of methodologies including MPA, ANC, NAPP, NAG and microbial testing. Sulfide reduction from 4 to 1% reduces AMD generation. Further reduction below 1% S yields diminishing returns. The environmental benefit of separating ‘active’ and ‘passive’ gangue material prior to disposal is shown, and the reduced active gangue fraction determined through material balance.