Effect of additives on monovalent copper electrodeposition in ammoniacal alkaline solutions

In order to reduce the surface roughness of a copper deposit from cuprous ions in ammoniacal alkaline solutions, optimization of the electrolytic conditions was attempted, and the surface roughness was somewhat improved. Because the improvement was insufficient, the addition of gelatin or polyethylene glycol (PEG) to the electrolyte was then examined. It was revealed that both additives effectively polarized during copper electrodeposition and that the extent of the polarization increased with the molecular weight of the additives. As a result, both surface roughness and crystal size of the copper deposit were reduced. In the case of PEG, however, nodules tended to form and gelatin was concluded to be superior to PEG as an additive for the present electrolysis. The influence of gelatin on the impurity content of the copper deposit was also investigated, and the addition of gelatin was found to have a positive effect on reducing the lead content. This is important because lead is the most important impurity in the authors' copper recycling process employing the present electrolysis.

► Copper electrodeposition from ammoniacal alkaline solutions was investigated.
► The copper deposit became rough in the absence of additives with no agitation.
► Gelatin and polyethylene glycol reduced the surface roughness of the copper deposit.
► Polyethylene glycol tended to cause nodule formation.
► Gelatin was found to be a potential additive for the present electrolysis.