Statistical evaluation and optimization of zinc electrolyte hot purification process by Taguchi method

Abstract

The neutral zinc sulfate solution obtained from hydrometallurgical process of Angouran zinc concentrate has cadmium, nickel and cobalt impurities, that must be purified before electrowinning. Therefore, cadmium and nickel are usually cemented out by addition of zinc dust and remained nickel and cobalt cemented out at second stage with zinc powder and arsenic trioxide. In this research, a new approach is described for determination of effective parameters and optimization of zinc electrolyte hot purification process using statistical design of experiments. The Taguchi method based on orthogonal array design (OAD) has been used to arrange the experimental runs. The experimental conditions involved in the work are as follows: the temperature range of 70−90 °C for reaction temperature (T), 30−90 min for reaction time (t), 2−4 g/L for zinc powder mass concentration (M), one to five series for zinc dust particle size distributions (S1-S5), and 0.1−0.5 g/L (C) for arsenic trioxide mass concentration. Optimum conditions for hot purification obtained in this work are T4 (85 °C), t4=75 min, M4=3.5 g/L, S4 (Serie 4), and C2=0.2 g/L.