Improving cathode morphology at a copper electrowinning plant by optimizing Magnafloc 333 and chloride concentrations

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.

Effect of Cd2+ on Electrodeposition of Copper in Cyclone Electrodeposition

“…When the concentration of H + decreased It can be seen from Figure 6a that the microscopic morphology of the cathode copper sheet produced in a stage of electrodeposition without adding Cd 2+ was comprised of polyhedral nodules [33] on the cathode. During the electrodeposition, the copper crystal spread all over the polyhedral nodules and produced a dense copper surface with a few remaining visible cracks and pores [34]. After adding a small amount of Cd 2+ , a small number of visible cracks and pores were generated in the crystallization bonding part of each curved surface based on this microscopic morphology (Figure 6b).…”

“…With the increase of the addition amount of Cd 2+ , the copper crystals became no longer compact but formed an uncompact and nonhomogeneous structure [35], and the generated cracks and pores also became larger (Figure 6c). According to the image (Figure 6d) of the cathode copper sheet obtained by adding 4 g/L Cd 2+ , it can be seen that its morphology generated polyhedral crystals with shape edges [34] and spread across the whole cathode. The addition of Cd 2+ made the irregular polyhedral crystals smaller in volume, and it could be seen that its crystallization rule was covered by copper layer by layer of crystal, thus generating the stepped shape in the picture (Figure 6e).…”

“…The crystallization mode of its microscopic morphology was observed by SEM, as shown in Figure 8. The micro-morphology of cathode copper obtained by the electrodeposition of copper electrolyte without adding Cd 2+ showed that the copper crystal nuclei were one-byone spherical nodules [34] without any cracks and pores (Figure 8a). With the addition of Cd 2+ , some clear grain refinements [36] were generated based on the spherical nodules [34].…”

“…The higher the addition amount of Cd 2+ , the longer the end time of the electrodeposition and the lower the rate of the whole electrodeposition. The addition of Cd 2+ weakened the electrochemical reaction of Cu 2+ on the cathode and reduced the attenuation rate of Cu 2+ in the solution, the ability The micro-morphology of cathode copper obtained by the electrodeposition of copper electrolyte without adding Cd 2+ showed that the copper crystal nuclei were one-by-one spherical nodules [34] without any cracks and pores (Figure 8a). With the addition of Cd 2+ , some clear grain refinements [36] were generated based on the spherical nodules [34].…”

“…The addition of Cd 2+ weakened the electrochemical reaction of Cu 2+ on the cathode and reduced the attenuation rate of Cu 2+ in the solution, the ability The micro-morphology of cathode copper obtained by the electrodeposition of copper electrolyte without adding Cd 2+ showed that the copper crystal nuclei were one-by-one spherical nodules [34] without any cracks and pores (Figure 8a). With the addition of Cd 2+ , some clear grain refinements [36] were generated based on the spherical nodules [34]. The more Cd 2+ that was added, the finer the sediments that were generated on the compact surface and the larger the pores between each crystal (Figure 8b-f).…”