Rejection of antimony and bismuth in sulphide flotation – a literature review

ABSTRACT Rejection of deleterious impurity minerals containing antimony and bismuth from sulphide deposits by flotation has been reviewed. The key antimony minerals of commercial interest to remove are stibnite, tetrahedrite, and jamesonite, while the main bismuth mineral is bismuthinite. The most promising methods for separating antimony and bismuth minerals from sulphide ores are based on pH and/or pulp potential adjustments or the use of starvation levels of collector. Stibnite has been floated with xanthate, dithiophosphates and thionocarbamates in acidic conditions, but floatability decreased with increasing pH. Antimony minerals are activated with lead and copper salts and depressed with an oxidant (e.g. H2O2 or Na2Cr2O7). Bismuth minerals can float strongly between pH 3 and 7 with a xanthate collector but floatability decreased sharply at pH values above pH 7. Molybdenite is separated from bismuth minerals by depressing them with reducing agents such as sodium sulphide, while cyanide depresses chalcopyrite.