Current efficiency studies of the zinc electrowinning process on aluminum rotating cylinder electrode (RCE) in sulfuric acid medium: Influence of different additives

This work studies the effect of three additives, sodium lauryl sulfate (SLS), cetyltrimethylammonium bromide (CTABr) and arabic gum (AG) on zinc electrowinning on aluminum in a solution of 85 g L⁻¹ Zn(II) (1.3 M) in 108 g L⁻¹ H₂SO₄ (1.1 M). The influence of these three additives is analyzed during the different stages of the reduction process using chronopotentiometric techniques on an aluminum rotating disk electrode (RDE). Potential ranges (−1.05 < E < −0.85 V versus SHE) and current density (−51 < i < −0.2 mA cm⁻²) within which zinc electrodeposition takes place in the presence of the three different additives were established. These parameters were used to determine current efficiencies (Φ), evaluated by electrolysis on an aluminum rotating cylinder electrode (RCE); the zinc deposition efficiency in the presence of SLS, CTABr and AG, was 95%, 96% and 99%, respectively, were all greater than the efficiency obtained without any additive (WA), Φ = 84%. The homogeneity of the deposits at the end of electrolyses implied that the (RCE) promotes uniform current density on the electrode surface and, hence, can be considered a model cell to evaluate current efficiencies.