Efficacy of polyacrylamide and protein flocculants in preventing anode depassivation induced Pb-contamination of copper electrowinning cathodes

The paper discusses the efficacy of Jaguar M50, Guarfloc 64, Superfloc N100, Separan NP10 and Floerger 912H flocculant additives in preventing contamination of Cu electrowinning cathodes by impurities like Pb. This was investigated in sulphate acid solutions at 60 °C. Results showed that mixing flocculants with Mersolat, a foaming-emulsifier (sodium alkane sulfonate) used to prevent corrosive emanations in electrowinning, minimises the volume of additive solutions. Washing the cathode surfaces using water at 60 °C is also seen to reduce Pb contents in electro-deposited copper metal.Although all these flocculant additives can be used to limit copper cathode contamination by Pb, one also needs to consider the economic implications when selecting the appropriate flocculant for a given industrial application. This is because it was observed, in this study, that the best flocculant in limiting this contamination also adversely introduced higher cathode overpotentials, resulting in higher electrolysis specific energy consumption.

Research Highlights
► Contamination of copper electrowinning cathodes by the dissolved or transported Pb from the Pb-Sb anodes was evaluated.
► Efficacy of five flocculants and a mixture of Jaguar with Mersolat in preventing the contamination were analysed.
► All these flocculants limited the contamination of the electrodeposited metal by Pb.
► It was observed that the best flocculants in preventing Pb-contamination introduced higher cathode overpotentials, hence it is suggested that economic considerations, such as electrolysis specific energy consumption, be taken into account in selecting the appropriate flocculant additives.