Optimization of microwave roasting for dechlorination of CuCl residue from zinc hydrometallurgy

Removal of chlorine (Cl) from the CuCl residue in the process of zinc hydrometallurgy is of great importance to improve the process economics. The current processing methods result in generation of large quantities of polluted discharge necessitating waste treatment systems. The present work attempts to de-chlorinate the CuCl residue through thermal treatment with the application of microwave energy. Relationship between explanatory and response variables was explored by response surface methodology (RSM) technique searching to optimize the dechlorination efficiency. The effect of three major parameters such as temperature, duration of heating, and particle size of samples were assessed and the optimal process conditions were identified. Analysis of variance (ANOVA) was utilized to identify the suitable model and to eliminate the insignificant model parameters. The optimized process conditions for maximizing the dechlorination efficiency are identified to be a roasting temperature of 426 ºC, heating time 125 min, and particle size of samples 0.12 mm. A dechlorination efficiency of 93% could be achieved at the optimal process conditions, and validated through repeat experimental runs at the optimized process conditions. The optimized process samples are characterized utilizing XRD and SEM/EDS to validate the dechlorination efficiency.