Effect of calcium and thiosulfate ions on flotation selectivity of nickel–copper ores

Effect of calcium and thiosulfate ions on flotation of a Ni–Cu ore was investigated. The ions improved the flotability of sulfides at the normal process pH after grinding in steel mill. Calcium activated especially nickel and copper sulfides when the galvanic effect of mill iron was effective. The UV/Vis measurements showed that calcium ions increased xanthate adsorption on the sulfides. The effect of thiosulfate was different. It was concluded that thiosulfate reduced the effect of hydrophilic compounds on sulfide particles, and in that way improved their flotation.