Insights on the effect of pyrite liberation degree upon the acid mine drainage potential of sulfide flotation tailings

摘要

A new insight into the way in which the mineralogical composition and texture (liberation) of sulfides govern the geochemical behavior of the tailings in terms of acid mine drainage (AMD) generation is presented. Two samples were taken from Dundee Precious Metals Chelopech (DPM-Ch) tailings management facility (TMF). They were likewise subjected to flotation to recover reactive (liberated and partially liberated) pyrite whilst the unreacted (locked) pyrite was kept in the tailings fraction. Geochemical (static and kinetic) tests were performed on the collected samples and tailings after flotation. A scanning electron microscope based automated mineralogy system was used to characterize them in terms of modal mineralogy, liberation degree and particle size. The absolute acid-generating potential (AP) defined by the Sobek method most likely overestimates the effective AP when pyrite is locked into non-reactive gangue minerals. Hence, the locked pyrite may unfavorably lead to increased tailings management costs. Therefore, the automated mineralogy data was used to calculate the effective AP of the tailings taking into account pyrite grade and its liberation degree. Based on these findings, it could be assumed that the amount of lime required to neutralize the acidity produced by pyrite oxidation would be considerably reduced (in the studied case nearly 4 times) if environmental desulfurization by flotation is practiced and the liberation degree of the acid-producing minerals is taken into account.