Effects of certain impurities on zinc electrowinning in high-purity synthetic solutions

• Published in: Journal of applied electrochemistry 1988-07, Vol.18 (4), p.583-589
• Main Authors: AULT, A. R, FRAZER, E. J
• Format: Article
• Language: English
• Subjects: Adsorption; Chemistry; Electrochemistry; Electrodeposition; Exact sciences and technology; General and physical chemistry; Study of interfaces; Transport phenomena
• ISSN: 0021-891X; 1572-8838
• DOI: 10.1007/bf01022254

The individual effects of Pb, Cu, Ni, cobalt and Sb on Zn electrowinning were evaluated by measurements in high-purity synthetic solutions, free from additives. The coulombic efficiency (QE) of Zn electrodeposition was determined over 2 h under mass transfer-controlled conditions at a temperature of 35 deg C and a current density of 400 Am exp --2 in a solution of 0.8 M ZnSO sub 4 + 1.07 M H sub 2 SO sub 4 . Antimony had a very detrimental effect on QE causing decreases of approx 5 and 50% at 4 and 14 mu g 1 exp --1 , respectively. Antimony also exerted a strong grain-refining effect and changed the deposit orientation from random to (112) to (004) with increasing concentration. Lead has a small beneficial effect on QE at the electrode rotation rate employed (20s exp --1 ). It also exerted a grain-refining effect and changed the deposit orientation from random to (102), (103), (104), to strong basal (004), (002) with increasing concentration. Copper, Ni and Co had minor effects on QE, with reductions at 5 mg 1 exp --1 of 0.8, 0.3%, respectively. The effects of Cu on morphology and orientation were very concentration dependent, but with a general trend towards grain-refining and random orientation. Nickel promoted coarse-grained deposits and changed the orientation from random to (114), (102) to (204), (102) with increasing concentration. Cobalt had the lest effect on the morphology of the deposit, although it gradually increased the basal plane orientation with increasing concentration. 43 ref.--AA