THE ELECTROCHEMICAL DISSOLUTION OF GOLD IN BROMINE MEDIUM

Galvanic interactions between gold and associated substances are among st the many factors that could influence the rate of dissolution of go ld in a bromine medium. Some of these galvanic influences were investi gated in order to understand the electrochemistry behind the dissoluti on of gold in bromine medium. Two rotating disc electrodes, either in the same container or in two separate containers linked by a salt-brid ge were 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 t he formation of a film on the gold surface. Copper, iron and galena ca use the largest decrease in the rate of leaching when in contact with gold. This can be mainly attributed to the galvanic interaction betwee n the two substances. Sphalerite strongly enhances the dissolution rat e 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 format ion on the gold surface which probably increased its conductivity. Gol d in contact with pyrite also enhances the gold dissolution rate signi ficantly.