Deleterious impacts of triethylenetetramine and sodium metabisulphite on gold flotation during pyrrhotite depression

The synergistic application of sulfites and polyamines has led to a significant advancement in the selective depression of pyrrhotite during pentlandite and chalcopyrite flotation, yet their efficacy in the flotation of gold-copper ores remains unexplored. Herein, the effect of sodium metabisulphite (SMBS) and triethylenetetramine (TETA) on gold recovery during the selective depression of pyrrhotite in gold-copper ore flotation was investigated. Flotation results revealed that while the SMBS+TETA mixture markedly reduced pyrrhotite recovery from 65 % (baseline recovery) to 22 % without compromising chalcopyrite flotation, it concurrently decreased gold recovery from 82 % to 50 %. Employing TETA alone also decreased gold recovery to 55 %, while the flotation of pyrrhotite and chalcopyrite remained unaffected. The flotation data indicated that the reduction in gold recovery was primarily due to the addition of TETA. Consequently, a series of electrochemical methods were employed to explore the interaction mechanism between TETA and the gold surface. It was found that xanthate collector had a stronger affinity to gold than TETA but that TETA could still interact with the gold surface which was coated with xanthate. TETA could not only adsorb on the surface of gold to render the surface hydrophilic but also inhibit chemisorption and oxidation of xanthate to dixanthogen, leading to the reduced floatability of gold. The findings indicate that the functional groups of chelating agents should be taken into account when pyrrhotite is depressed during the flotation of gold-copper ores, especially in the presence of free gold.