B. C. Tripathy

Zinc electrowinning from acidic sulfate solutions: Part I: Effects of sodium lauryl sulfate

The effects of sodium lauryl sulphate(SLS) in the presence and absence of antimony(iii) on the current efficiency, power consumption and polarization behaviour of zinc were determined. The surface morphologies and deposit crystallographic orientations were also evaluated. The results were compared with glue as the addition agent. The addition of sodium lauryl sulfate to the zinc sulfate solution increased current efficiency, reduced power consumption and improved the surface morphology. Maximum current efficiency and minimum power consumption were achieved on addition of 0.02mgdm−3 Sb with 1mgdm−3 sodium lauryl sulfate.

Zinc electrowinning from acidic sulphate solutions. Part III: Effects of quaternary ammonium bromides

The effects of the organic additives cetyltrimethylammonium bromide (CTABr) and tetrabutyl ammonium bromide (TBABr) on the electrowinning of zinc from acidic sulphate solutions were studied in the presence and absence of trace amounts of antimony(iii). The results indicated that CTABr has similar properties to the commonly used industrial additive glue with respect to current efficiency, power consumption, polarization behaviour, and the crystallographic orientation and surface morphology of the zinc deposits. TBABr was generally less useful with respect to all these properties. Voltammetric studies indicate that polarisation for zinc electrodeposition decreased in the order CTABr > glue > TBABr. The nature of the electrode reactions were investigated through measurements of exchange current densities, Tafel slopes and transfer coefficients.

Zinc electrowinning from acidic sulphate solutions Part II: Effects of triethylbenzylammonium chloride

The effects of triethylbenzylammonium chloride (TEBACl) on the electrowinning of zinc from acidic sulfate solutions have been studied in the presence and absence of antimony(iii). The factors considered included the current efficiency (CE), power consumption, polarisation behaviour, and the crystallographic orientations and surface morphology of the deposits. Compared with the traditional industrial additive, glue, the addition of TEBACl increased CE, reduced power consumption and improved the surface morphology. Maximum CE and minimum power consumption were obtained at 2mgdm−3 TEBACl and 0.01mgdm−3 Sb(iii). The exchange current density, Tafel slope and transfer coefficient were determined to elucidate the nature of the electrode reactions involved.

Effect of Cr3+ on the electrodeposition of nickel from acidic sulfate solutions

The effect of Cr3+ on the cathodic current efficiency (CE), deposit morphology, crystallographic orientations and polarisation behaviour during nickel electrodeposition from acidic sulfate solutions containing boric acid was investigated. A progressive decrease in CE was seen with increase in Cr3+ concentration showing a maximum decrease in CE of ∼10-13% at concentration ∼100 mg dm-3. The presence of Cr3+ did not change the fcc structure of the electrodeposited nickel but affected the peak intensities of the crystal planes. Polarisation of the cathode was seen in the presence of Cr3+ in the electrolyte along with a shift in the electroreduction potential of nickel (II) ion towards more negative values. The effect of Cr3+ on the electrokinetic parameters: Tafel slope (b), transfer coefficient (α) and exchange current density (i0) has also been investigated.