The depression of pyrite in selective flotation by different reagent systems – A Literature review

•Pyrite floats readily in acid and neutral conditions with xanthate as collector.•Inorganic, organic reagents and non-xanthate collectors are used to depress pyrite.•Inorganic depressants act by inhibiting xanthate adsorption.•Organic depressants act by adsorption on pyrite forming a hydrophilic layer.•Non-xanthate collectors ensure selectivity towards valuables against pyrite. Pyrite is a gangue mineral widely associated with valuable minerals. It is problematic to deal with in differential flotation because it easily reports to flotation concentrates. Pyrite may float due to natural or self-induced hydrophobicity or collector-induced hydrophobicity. Its flotation can also be enhanced by the activation of copper or lead ions emanating from other minerals. Depressants are generally required to selectively depress pyrite. In this article, a comprehensive review of the fundamental studies of depression mechanisms and effectiveness of commonly used reagent systems to depress pyrite is presented. It includes inorganic reagents (hydroxyl ions, oxygen conditioning, cyanide, sulfoxyl reagents, etc.), organic reagents such as polysaccharides (starch, dextrin, carboxymethyl cellulose etc.), polyacrylamides, wood-extracted biopolymers, diethylenetriamine and a combination of these methods. Overall, the action of pyrite depressants is either to desorb the collector or activator from pyrite surface, deactivate the activating ions, prevent collector adsorption on pyrite, or make the pyrite surface hydrophilic. The mechanisms of some non-xanthate collectors such as dithiophosphate, dithiophosphinate and thionocarbamate in rejecting pyrite were also briefly reviewed.