A review of pyrrhotite flotation chemistry in the processing of PGM ores

The chemistry of pyrrhotite flotation using xanthate collectors is reviewed with respect to the processing of PGM ores and the recent results from captive bubble contact angle measurements at the University of Utah are presented. In some cases a low flotation recovery of PGM may be due to the surface state of pyrrhotite particles under conventional flotation conditions (open to air and pH 9.0). Thermodynamically pyrrhotite is not stable and reacts relatively quickly with its environment. Natural/collectorless flotation of pyrrhotite is observed only under a low oxidation potential in acidic solution. Its surface is easily oxidized to ferric hydroxide/oxide under conventional flotation conditions, creating a hydrophilic state at the pyrrhotite surface and low flotation recovery even though xanthate collectors can be adsorbed. Under these conditions, activation by copper is not easily achieved. These observations reported in the literature have been confirmed by captive bubble contact angle measurements. Based on the analysis of previous research, conditions for improved pyrrhotite flotation and increased PGM recovery are suggested. (C) 2005 Published by Elsevier Ltd.