A New Approach to Nickel Recycling from Zinc Plant Residue: A Morphological and Crystallographic Study on the Effects of Zinc Impurity on the Electrowinning of Nickel

Nickel-bearing zinc plant residues (cold filtercake, CFC) cause a serious threat to the environment. In this research, nickel deposits from an electrowinning from a nickel sulfate electrolyte containing a high concentration of zinc as an impurity were studied in two sections. In the first, effects of four parameters including Ni2+ concentration, pH, temperature and current density have been studied in a synthetic sulfate electrolyte, and based on current efficiency (CE) and morphological characterizations of the deposits, the optimum conditions were chosen as 30 g/L Ni2+, pH 3.5, 45 degrees C and 200 A/m(2). Subsequently, the effect of zinc impurity in the range of 0-600 mg/L was studied in terms of CE and morphology, purity and texture of the nickel deposits. The CE decreased as well as the deposit surface quality and purity by increasing the zinc concentration. Field emission scanning electron microscopy (FESEM) analysis revealed that when the Zn2+ concentration in the electrolytes increased from 0 mg/L to 75 mg/L, a continuous decrease in the nickel particle size was detected.

Automated summary

Nickel-bearing zinc plant residues pose a serious environmental threat. This research focuses on nickel deposits from an electrowinning process, where a nickel sulfate electrolyte with high zinc impurity concentration was used. The effects of Ni2+ concentration, pH, temperature, and current density were studied, and the optimal conditions were determined. Furthermore, the influence of zinc impurity concentration on the deposit characteristics was investigated, showing a decrease in current efficiency and the quality of the deposits with increasing zinc concentration.