Effect of antimony(III) on the electrocrystallisation of zinc from sulphate solutions containing SLS

A detailed investigation has been carried out to determine the effect of antimony(III) on the electrocrystallisation of zinc from sulphate solutions containing sodium lauryl sulphate (SLS). The results indicated that addition of Sb(III) at trace level to the electrolysis bath without sodium lauryl sulphate decreased the current efficiency (CE) and deteriorated the quality of the zinc electrodeposits. However, its addition to the bath containing sodium lauryl sulphate increased the current efficiency and also improved the surface morphology of the zinc electrodeposits. There was no trace of antimony found in any of the deposits. Cathodic polarisation curves were traced and analysed to determine the kinetic parameters, exchange current density, Tafel slopes and transfer coefficients so as to elucidate the nature of the electrode reactions. Presence of Sb(III) alone in the electrolyte depolarised the cathode and SLS alone polarised it; however, presence of both gave a balanced condition suitable for zinc electrowinning.