Dechlorination of zinc oxide dust derived from zinc leaching residue by microwave roasting in a rotary kiln

The dechlorination efficiency of zinc oxide dust using microwave roasting was investigated capitalizing on the different microwave absorbing capacities of the compounds such as chlorine, lead, and zinc oxide. The associated dechlorination reactions were discussed in detail and the effect of all the influencing parameters such as the air flow rate, steam flow rate, the roasting temperature, roasting duration, and the mixing rate were assessed to identify the optimal conditions. The results indicated that a near 93% dechlorination of zinc oxide dust could be achieved, which would satisfy the requirements of the wet smelting electrolysis process. The optimal process parameters were identified to be an air flow of 300 L/h, a steam flow of 8 mL/min, a stirring speed of 60 rpm, a roasting temperature of 650 °C, and a roasting duration of 60 min. Water vapor has an enhanced effect on dechlorination by microwave roasting.