17 - Flotation of Gold Ores

Abstract

In spite of the lack of basic research on flotation of gold-bearing ores, the flotation technique is used not only for upgrading of low-grade gold ore for further treatment, but also for beneficiation and separation of difficult-to-treat gold ores. This chapter focuses on treatment methods for gold-bearing ores. Flotation is the best method for recovery of gold from base metal ores and gold-containing PGM (platinum group metal ores. Excluding gravity preconcentration, flotation remains the most cost-effective beneficiation method. During flotation of gold-bearing massive sulphide ores, the emphasis is generally placed on the production of base metal concentrates and gold recovery becomes a secondary consideration. In some cases, where significant quantities of gold are contained in base metal ores, the gold is floated from the base metal tailings. The flotation of gold-bearing ores is classified according to ore type (i.e., gold ore, gold copper ore, gold antimony ores, etc.), because the flotation methods used for the recovery of gold from different ores is vastly different. In flotation of gold-containing base metal ores, a number of modifiers normally used for selective flotation of copper lead, lead zinc, and copper lead zinc have a negative effect on the floatability of gold. Such modifiers include ZnSO4·7H2O, SO2, Na2S2O5, and cyanide when added in excessive amounts. The adsorption of collector on gold and its floatability is considerably improved by the presence of oxygen.