Extraction and kinetic analysis of Pb and Sr from the leaching residue of zinc oxide ore
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Extraction and kinetic analysis of Pb and Sr from the leaching residue of zinc oxide ore Xiao-yi Shen 1), Yuan-yong Liang 1), Hong-mei Shao 2), Yi Sun 1), Yan Liu 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 (Received: 13 November 2019; revised: 17 December 2019; accepted: 20 December 2019)
Abstract: NH4HCO3 conversion followed by HCl leaching was performed and proven to be effective in extracting Pb and Sr from zinc extracted residual. The mechanism and operating conditions of NH4HCO3 conversion, including molar ratio of NH4HCO3 to zinc extracted residual, NH4HCO3 concentration, conversion temperature, conversion time, and stirring velocity, were discussed, and operating conditions were optimized by the orthogonal test. Experimental results indicate that NH4HCO3 conversion at temperatures ranging from 25 to 85°C follows the shrinking unreacted core model and is controlled by inner diffusion through the product layer. The extraction ratios of Pb and Sr under optimized conditions reached 85.15% and 87.08%, respectively. Moreover, the apparent activation energies of Pb and Sr were 13.85 and 13.67 kJ·mol−1, respectively. Keywords: zinc extraction residual; NH4HCO3 conversion; HCl leaching; Pb; Sr; reaction mechanism; kinetics
1. Introduction Pb and its compounds are used in several applications, including Pb batteries, pyrotechnics, X-ray absorptive coatings, and Pb glasses, but the heavy metal is a hazardous element in the environment because of its toxicity to organisms [1]. The pollution generated by Pb has become a global issue [2]. Anthropogenic discharge of Pb should be strictly restricted. Because of the gradual depletion of Pb sulfide ores and the heavy pollution brought about by pyrometallurgical processes, exploitation of Pb oxidized minerals, including lowgrade Pb–Zn ore, lead–acid-battery paste, and its secondary smelting residues, using hydrometallurgical routes employing various agents, such as acids, chlorides, and NaOH, has been paid increased attention [3–7]. Sr shows the lowest abundance among alkaline earth metals, and Sr compounds, such as Sr(NO3)2 and SrCl2, are usually prepared from SrCO3 obtained by celestite mineral [8–11]. SrCO3, as one of the more important Sr compounds currently available, has been widely used in a variety of fields, including cathode ray tubes for TV imaging, photocatalysts for degradation of organic pollutants, and advanced ceramic materials [8,12]. Wellknown extraction processes for Sr include the black ash and
direct conversion methods [8,12–14]. Unfortunately, the high energy consumption required by the black ash method, as well as the heavy pollution it causes, has led to a loss of interest in its use [10,12–14]. Metallo
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