| The objective of this research was to explore an efficient process to recover cyanide and copper from barren gold cyanide solution. The research work described here concerns an investigation into fundamental and practical aspects of two options for electrowinning copper from cyanide solution. These two options are: (a) the use of an alternative anode reaction to limit the electro-oxidation of cyanide in concentrated cyanide solutions and (b) the use of a graphite fibre cathode to electrowin copper from dilute cyanide solution.; Direct copper electrowinning from dilute cyanide solutions was conducted in a membrane cell. The accumulation of deposited copper on the graphite felt as the plating proceeds significantly improves the conductivity of the graphite felt, increases the specific surface area and benefits copper deposition.; Copper electrowinning from concentrated copper cyanide solution (70 g L−1 Cu) was conducted using four sacrificial species (sulphite, methanol, thiocyanate and ammonia) at 40 to 60°C. Only sulphite can decrease the anodic current efficiency of cyanide oxidation from ∼100 to 10–20% over the current density range of 250–500 Am −2. With increasing CN:Cu mole ratio from 3 to 4.5, the anodic current efficiency of cyanide oxidation increased and the copper deposition current efficiency decreased.; The anodic oxidation of copper cyanide has been studied using a graphite rotating disk with reference to cyanide concentration (0.05–4 M), CN:Cu mole ratio (3–12), temperature (25–60°C) and hydroxide concentration (0.01–0.25 M). Copper had a significant catalytic effect on cyanide oxidation. In the low polarization region, cuprous, cyanide is oxidized to cupric cyanide complexes which further react to form cyanate. In the high polarization region cuprous cyanide complexes were oxidized to copper oxide and cyanate.; Sulphite oxidation is enhanced by the presence of copper cyanide. The effect of sulphite on limiting the oxidation of copper cyanide decreases with increasing mole ratio of cyanide to copper. This is related to the shift in the discharged species from Cu(CN)32− to Cu(CN) 43− with increasing mole ratio of cyanide to copper. (Abstract shortened by UMI.)... |
