Abstract In this study, the roles of tannic acid and gelatin in Zn electrowinning were investigated. The results indicated that the addition of 10 mg/L of gelatin promoted Zn electrowinning and increased its current efficiency (CE) from 89.55% to 91.8%. However, the CE was only 77.47% when the electrolyte contained 50 mg/L of gelatin. As the concentration of tannic acid in the electrolyte increased from 10 mg/L to 400 mg/L, the CE decreased from 85.73% to 72.09%, which represented declines of 4.27% and 19.5%, respectively, compared with that of normal Zn electrowinning conditions in the absence of tannic acid. With increase in the concentrations of tannic acid and gelatin, the cell voltage increased and CE decreased sharply, which eventually resulted in a significant increase in the unit consumption of direct current (DC). The mechanisms by which tannic acid and gelatin inhibited the kinetics of Zn plating were additionally researched using electrochemical methods. The results showed that tannic acid and/or gelatin in high concentrations in the electrolyte significantly inhibited the deposition of Zn on the cathode by increasing the overpotential, reducing the deposition rate, and covering the electrode surface, which led to the appearance of agglomerates and needle-like structures on the surfaces of the Zn sheets.

中文翻译：

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单宁酸和明胶在锌电积中的作用及其电化学方法研究的抑制机制

摘要 本研究考察了单宁酸和明胶在锌电积中的作用。结果表明，添加 10 mg/L 的明胶促进了 Zn 电积，并将其电流效率 (CE) 从 89.55% 提高到 91.8%。然而，当电解液中含有 50 mg/L 的明胶时，CE 仅为 77.47%。随着电解液中单宁酸浓度从10mg/L增加到400mg/L，CE从85.73%下降到72.09%，与普通锌电积相比分别下降4.27%和19.5%在没有单宁酸的条件下。随着单宁酸和明胶浓度的增加，电池电压升高，CE急剧下降，最终导致直流（DC）单位消耗量显着增加。使用电化学方法进一步研究了单宁酸和明胶抑制镀锌动力学的机制。结果表明，电解液中高浓度的单宁酸和/或明胶通过增加过电位、降低沉积速率和覆盖电极表面，显着抑制锌在阴极上的沉积，导致团块和针状物的出现。 Zn 片材表面的类似结构。