Blocking of harmful effect of bismuth ions during electroextraction of zinc from sulphate electrolytes

Abstract

Binary and ternary (Pb–Bi and Pb–Ag–Bi) cast and rolled alloys have been investigated. These alloys are intended for use as anodes in the electroextraction (electrowinning) of zinc from sulphate electrolytes. Characterisation of the alloys has been performed by means of quantitative inductively coupled plasma atomic emission spectroscopy (ICP-AES). This analytical technique has also been employed to determine the quantity of dissolved bismuth in the sulphate electrolytes. The electrochemical behaviour of the investigated alloys has been evaluated by galvanostatic studies and their surface morphology has been examined by scanning electron microscopy. It has been established that addition of inhibitors and complexants leads to an increase of the current efficiency of zinc electrowinning and blocks significantly the harmful effect of bismuth ions on the reaction of zinc deposition.

Keywords:

• Zinc electrowinning
• Lead–bismuth alloys
• Inhibitors
• Complexants

The authors extend their sincere gratitude to their colleagues from IPC-BAS: T. Tsacheva (physicist) for the EDS and SEM analysis, and G. Avdeev (research scientist) for the XRD analysis of the anodes under test.