Abstract
Recovery of zinc from low grade zinc oxide ore is attempted with ammonia and ammonium citrate solutions augmented by microwave roasting and ultrasound radiation. The influence of the ammonia-ammonium ratio, roasting temperature, ultrasound power, and leaching time were assessed on the recovery of zinc. A maximum zinc recovery of 88.57% could be achieved at a roasting temperature of 673 K, leaching temperature of 298 K, stirring speed of 300 rpm, total ammonia concentration of 5 mol/L with an ammonium citrate concentration of 1.2 mol/L, liquid to solid ratio of 5:1, the ultrasound power was 600 W and the leaching time was 120 min. The enhancement in recovery with increases in the roasting temperature up to 673 K was attributed to the conversion of ZnCO3 to ZnO. The phases of mineral samples and the reaction residues were characterized by X-ray diffraction (XRD).
Highlights
With the availability of zinc sulfide ores dwindling, the need to identify alternative ores is imperative [1,2]
The complicated zinc ore received from Yunnan province of China, was crushed and ground
Effect of Microwave Roasting on % Leaching of Zinc
Summary
With the availability of zinc sulfide ores dwindling, the need to identify alternative ores is imperative [1,2]. The recent efforts in literature indicate utilization of an alkali such as ammonia for leaching metals like cobalt, nickel and copper due to the formation of stable metal amine complexes, leading to higher solubility in most cases. Other harmful impurities, such as Fe, Pb, Ca, and Mg precipitate as hydroxides due to their poor complexability with ammonia [8]. Reports on the process of optimization of the ammonia leaching process for the separation of zinc ores are not available, necessitating such an effort in the field of hydrometallurgy
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