Abstract:
Electrowinning circuits normally use a number of additives in the electrolyte to promote smooth, compact
deposits. These cathodes have the best levels of purity. When electrowinning is coupled to a solvent
extraction operation, it is important to minimize the amount of surface-active additives used, as their
presence tends to increase phase-disengagement times. In the present work the effects of Magnafloc 333
and chloride concentration were studied with the aim of minimizing the amounts currently being added,
while producing an acceptable copper cathode morphology. Magnafloc 333 is a non-ionic polyacrylamide
that promotes the plating of smooth, dense copper deposits with minimal impurities. Chloride is added
to promote the growth of dense, fine-grained, low-impurity copper deposits on the cathode. A Hull
cell was used for the test work. Optimum Magnafloc 333 and chloride concentrations for a synthetic
plant electrolyte were found to be 0.01 g/L and 0.025 g/L, respectively. These concentrations were then
used to plate laboratory-scale copper cathodes from synthetic and plant electrolytes. Scanning electron
microscopy was used to analyse the morphology of the cathodes plated. Many polyhedral crystals were
deposited from the synthetic electrolytes, but deposits from the plant electrolytes tended to be spherical,
with a large degree of porosity at the lower Magnafloc 333 concentration of 0.01 g/L. Polyhedral deposits
were associated with high-quality, smooth plated cathodes.
