a process in nonferrous metallurgy in which oxides or metals are converted into sulfide form to facilitate their subsequent extraction.
The method is most commonly used in the production of nickel; during shaft smelting of nickel oxide ore, small amounts of nickel and cobalt (~1 percent Ni and ~0.025 percent Co in the ore) are removed from the gangue by converting them into relatively enriched mattes (up to 22 percent Ni). The consumed sulfidizing agents, gypsum (CaSO4·2H2O) and pyrite (FeS2), make up 5–7 percent (by weight) of the charge.
The sulfidizing method is also used to remove copper from crude lead and in ore dressing to prepare oxide ores for flotation. In the first case the sulfidizing agent is elemental sulfur; in the second, sodium sulfide, Na2S, is used.
V. IA. ZAITSEV