Zinc electrowinning from acidic sulphate solutions Part IV 1: effects of perfluorocarboxylic acids

This study investigates the effects of perfluorobutyric acid, perfluoroheptanoic acid, and perfluorooctanoic acid during the electrowinning of zinc from acidic sulphate solutions, both in the presence and absence of antimony(III). The research aims to understand how these perfluorocarboxylic acids influence cathodic current efficiency, power consumption, and the polarization behavior of the cathode. By conducting analyses on surface morphology and crystallographic orientations of zinc deposits, we find that the addition of any of the tested acids leads to increased current efficiency, decreased power consumption, and improved surface morphologies of the zinc deposits. Voltammetric studies reveal that the polarization efficiency of the electrode follows the trend: PFOA > PFHA > PFBA. Furthermore, the nature of electrode reactions is examined through exchange current densities, Tafel slopes, and transfer coefficients, showcasing that perfluorocarboxylic acids serve as effective additives for zinc electrodeposition, particularly in the absence of Sb(III) in the zinc electrolyte.