The electrochemical dissolution of gold in bromine medium
Galvanic interactions between gold and associated substances are amongst the many factors that could influence the rate of dissolution of gold in a bromine medium. Some of these galvanic influences were investigated in order to understand the electrochemistry behind the dissolution of gold in bromine medium. Two rotating disc electrodes, either in the same container or in two separate containers linked by a salt-bridgewere used in this investigation. The leaching behaviour of gold in contact or in association with various minerals depends largely on the galvanic interaction between gold and the mineral, and partially on the formation of a film on the gold surface. Copper, iron and galena cause the largest decrease in the rate of leaching when in contact with gold. This can be mainly attributed to the galvanic interaction between the two substances. Sphalerite strongly enhances the dissolution rate due to the action of dissolved Zn2+ ions on the surface of the gold. When these Zn2+ are prevented from coming into contact with the gold, sphalerite still enhances the gold leaching rate owing to film formation on the gold surface which probably increased its conductivity. Gold in contact with pyrite also enhances the gold dissolution rate significantly. © 1993.