Zinc extraction from zinc oxidized ore using (NH4)2SO4 roasting-leaching process

An improved method of (NH4)2SO4 roasting followed by water leaching to utilize zinc oxidized ores was studied. The operating parameters were obtained by investigating the effects of the molar ratio of (NH4)2SO4 to zinc, roasting temperature, and holding time on zinc extraction. The roasting process followed the chemical reaction control mechanism with the apparent activation energy value of 41.74 kJ·mol−1. The transformation of mineral phases in roasting was identified by X-ray diffraction analysis combined with thermogravimetry-differential thermal analysis curves. The water leaching conditions, including the leaching temperature, leaching time, stirring velocity, and liquid-to-solid ratio, were discussed, and the leaching kinetics was studied. The reaction rate was obtained under outer diffusion without product layer control; the values of the apparent activation energy for two stages were 4.12 and 8.19 kJ·mol−1. The maximum zinc extraction ratio reached 96% while the efficiency of iron extraction was approximately 32% under appropriate conditions. This work offers an effective method for the comprehensive use of zinc oxidized ores.