Accurate measurement of polarization potentials during electrodeposition of nickel metal from sulphate electrolytes

Abstract

Extraction of nickel from either laterite or sulphide ores involves various complex hydrometallurgical processes, the final step of which is often electrowinning to produce pure nickel metal. Methods to investigate, monitor, and control the electrowinning process are therefore of importance for producing nickel metal of desirable quality and purity. The significance of potential measurements during the electrowinning process is well established. Many potential measurement methods, however, are not sufficiently accurate or repeatable, and it is therefore often difficult to monitor and control the electrodeposition process accurately. The relationship between nucleation (deposition of the first nickel clusters to the cathode surface) and growth (as more and more nickel clusters deposit) during electrodeposition is paramount for controlling the formation and quality of the nickel metal electrodeposit. A need therefore still exists for accurate measurement of both nucleation and plating overpotentials during the early stages of electrodeposition. In this investigation, a polarization measurement technique was developed for nickel electrodeposition from sulphate electrolytes under typical commercial electrowinning conditions. This method is repeatable and accurate within approximately 10 mV, and enables the quick and concise monitoring of both nucleation and plating during nickel electrodeposition.