On the effects of antimony and glue on zinc electrocrystallization behaviour

Abstract

An investigation has been made to determine the effects that additions of glue and antimony have on the electrowinning of zinc from acid sulphate solutions. In particular, the zinc crystal growth and cathode current efficiencies were studied in an attempt to establish a correlation between morphology and the nature of the additives. Operating conditions of 55 A ft^−2#x002A; and 35°C were used for most of the experiments with electrolyte concentrations of approximately 55 gl⁻¹ zinc and 150 gl⁻¹ H₂SO₄. Additional runs were made at 40,75 and 100 Aft⁻² at 30,40 and 50°C in order to verify certain trends. Primarily by means of scanning electron microscopy (SEM) techniques, it was possible to categorize deposit morphologies according to the type and concentration of the additives. The general effect of antimony was to refine the grain size and cause the basal plane platelets to lie parallel to the substrate. Glue also caused some refinement, but caused the platelets to become aligned perpendicular to the substrate. Level deposits were obtained in the latter case, which would effectively prevent dendritic growths. A relationship between the relative amounts of glue and antimony in solution and the current efficiency was also obtained.