Nickel recovery from electronic waste II Electrodeposition of Ni and Ni–Fe alloys from diluted sulfate solutions

• Ni can be recovered from EG wastes as pure Ni or as Ni–Fe alloys.
• The control of the experimental conditions gives a certain alloy composition.
• Unusual deposits morphology shows different nucleation mechanisms for Ni vs Fe.
• The nucleation mechanism was progressive for Ni and instantaneous for Fe and Ni–Fe.

This study focuses on the electrodeposition of Ni and Ni–Fe alloys from synthetic solutions similar to those obtained by the dissolution of electron gun (an electrical component of cathode ray tubes) waste. The influence of various parameters (pH, electrolyte composition, Ni2+/Fe2+ ratio, current density) on the electrodeposition process was investigated. Scanning electron microscopy (SEM) and X-ray fluorescence analysis (XRFA) were used to provide information about the obtained deposits’ thickness, morphology, and elemental composition. By controlling the experimental parameters, the composition of the Ni–Fe alloys can be tailored towards specific applications. Complementarily, the differences in the nucleation mechanisms for Ni, Fe and Ni–Fe deposition from sulfate solutions have been evaluated and discussed using cyclic voltammetry and potential step chronoamperometry. The obtained results suggest a progressive nucleation mechanism for Ni, while for Fe and Ni–Fe, the obtained data points are best fitted to an instantaneous nucleation model.