Optimisation of gold recovery by selective gold flotation for copper-gold-pyrite ores

Gold flotation is often overlooked as a processing option as the precious m etal is viewed as being associated with the sulphide particles present in t he ore, even when a proportion of the gold is free. Gold does float readily , however, and the free gold can be selectively floated away from an ore co ntaining sulphides. This may be an alternative treatment route for gold roo m applications where fine gold losses can occur when treating gravity conce ntrates with pyrite and copper sulphides present. Floating gold from the su lphides could produce a directly smeltable product. Copper sulphides are se lectively floated from pyrite ores at high pH's in excess of II. It is less clear how the free gold behaves under these conditions. In addition, for e xtra gold recovery, further collectors are added, such as the monothiophosp hates, which are known to be selective gold collectors. What form does this additional gold recovery take? These are some of the questions left unansw ered from the literature. To answer some of these questions, the effect of collector type, and variou s operating variables, including pH, grind size and collector additions on gold flotation performance were investigated. At high pH, selectivity of gold against pyrite was possible with a number o f collectors. However, there was no selectivity against chalcopyrite in the flotation tests performed. Increasing the pH using lime showed no gold dep ression. Fine gold was easily floated while some coarse gold reported to th e flotation tail. (C) 2001 Published by Elsevier Science Ltd. All rights re served.