Zinc extraction from zinc oxidized ore using (NH 4 ) 2 SO 4 roasting-leaching process
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Zinc extraction from zinc oxidized ore using (NH4)2SO4 roasting−leaching process Xiao-yi Shen 1), Hong-mei Shao 2), Ji-wen Ding 3), Yan Liu 1), Hui-min Gu 1), and Yu-chun Zhai 1) 1) Key Laboratory for Ecological Utilization of Multimetallic Mineral of Ministry of Education, School of Metallurgy, Northeastern University, Shenyang 110819, China 2) School of Environmental and Chemical Engineering, Shenyang Ligong University, Shenyang 110159, China 3) School of Computer Science and Engineering, Northeastern University, Shenyang 110819, China (Received: 12 December 2019; revised: 11 February 2020; accepted: 12 February 2020)
Abstract: 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. Keywords: zinc oxidized ore; ammonium sulfate roasting, water leaching; kinetics; mechanism; extraction ratio
1. Introduction Zinc is an important nonferrous metal that is extensively applied to galvanization, alloys, batteries, and other fields. Sulfide ores have long been the main raw material in zinc metallurgy [1−2]. However, due to the overexploitation of sulfide ores and the increased zinc demand, much attention has been paid to the reasonable exploitation of zinc oxidized ores [2−9]. As the largest resources bearing zinc [4−5,10], zinc oxidized ores usually exist as oxidized carbonate or silicate minerals, such as smithsonite (ZnCO3), willemite (ZnSiO4), and hemimorphite (Zn4Si2O7(OH)2·H2O) [4,11−14]; in addition, they usually contain high-grade silica [7,15]. Extensive studies have been carried out to explore the treatment of zinc oxidized ores. Flotation has been applied to zinc oxidized ores, but its use is difficult because of the fine intergrowth, complex phase compositions, and high gangue content of zinc oxidized ores [3,16−17]. Pyrometallurgical and hydrometallurgical routes are adopted to utilize zinc oxidized ores. Tra
ditional pyrometallurgical processes are not highly competitive because of their h
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