Precipitation Process

Precipitation Process 

a refining process in which the sulfides of a metal ore react with a precipitating agent—metallic iron.

The precipitation process is the most commonly used method for refining antimony ores in the USSR. Antimony is reduced by iron in the reaction Sb₂S₃ + 3Fe = 2Sb + 3FeS, which at 1000°-1100°C is an irreversible process. The precipitating agent is added to the reaction mixture in the form of steel or cast-iron chips. When antimony is present in the ore as an oxide, a reducing agent, such as coal or coke, is added to prevent oxidation and loss of the antimony in the gaseous phase. Low-melting fluxes are used to lower the melting point and reduce the loss of antimony.

A precipitation electrorefining process for antimony ore has been introduced that permits more vigorous treatment of the ore with high-melting slags; limestone replaces a portion of the low-melting fluxes, and ferrous oxide is almost completely eliminated from the slags. This process is being successfully used to replace the precipitation process in reverberatory furnaces. The products of the precipitation process are crude metals that require further refining; slag, which is considered a waste product; and dust from the furnace gases, which is then treated by reduction smelting.