Correlation between mass transfer and operating parameters in zinc electrowinning

Abstract

The effects of antimony additions, acid concentration, and current density on mass transfer and deposition morphology were examined. The mass transfer coefficients of zinc were calculated using a codeposition method with cadmium as a tracer. The experiments were carried out for vertical electrodes in a Hull cell. The results indicate that the mass transfer coefficients increase with increasing antimony additions, acid concentration, and current density. Zinc dissolution is more severe at low current density and higher antimony levels than at higher current densities and lower antimony levels. A mass transfer correlation for pure zinc electrolyte data is $$Sh = 12.47\left( {ReSc} \right)^{0.45} $$ whereSh, Re, andSc are the Sherwood, Reynolds, and Schmidt numbers, respectively. The correlation fits very well with the experimental data. A correlation for electrolytes containing antimony was also obtained and has an exponent of 0.42. The correlations cover a wide range of operating parameters and provide a fast quantitative estimation of the change in mass transfer in zinc electrowinning.