Recovery of lead and silver from zinc acid-leaching residue via a sulfation roasting and oxygen-rich chlorination leaching method

Abstract

A large amount of acid-leaching residue is produced during the conventional Zn hydrometallurgy process, and this residue has a large concentration of a variety of valuable metals. The purpose of this study was to evaluate the ability of a procedure that entails the use of sulfation roasting, water leaching, and chlorination leaching (blowing oxygen technique) to recover Pb and Ag, followed by cooling crystallization and the replacement of Ag with lead sheet, to realize the full recovery of all valuable metals from zinc acid-leaching residue; consequently, good results were achieved. The best results were obtained under the following conditions: a sulfuric acid at 70% of the raw material quality, roasting temperature of 300 °C and roasting time of 2 h, followed by the process of leaching the roasted residue for 1 h by applying a water-to-solid ratio of 5:1 at room temperature. The recovery rates of Zn and Fe were 98.69% and 92.36%, respectively. The main parameters of the chlorine salt leaching system were as follows: Cl⁻ concentration of 300 g/L, Fe³⁺ concentration of 25 g/L, acid concentration of 2 mol/L, liquid-to-solid ratio of 9 mL:1 g, temperature of 90 °C, and leaching time of 0.5 h; this leaching process was followed by filtration separation. These conditions resulted in high extents of leaching for Pb and Ag (i.e., 98.87% and 96.74%, respectively). Finally, the kinetics of the process of Ag leaching using Cl⁻ ions in an oxygen-rich medium was investigated. It was found that the leaching process was controlled by the diffusion of the product layers, and the activation energy was 19.82 kJ/mol.

摘要

常规湿法炼锌过程中会产生大量的酸浸渣, 该残渣含有大量各种有价值的金属. 本研究的目的是评估使用硫酸熟化、 水浸和氯化浸出(吹氧技术)回收铅和银的能力, 接着通过冷却结晶并用铅片置换出银, 实现酸浸锌渣中所有有价金属的全面回收, 该工艺取得了良好的效果. 条件实验研究得出最佳工艺条件如下: 硫酸用量为原样质量的 70%, 焙烧温度 300 °C, 焙烧时间 2 h, 焙烧渣按液固比 5:1 室温水浸 1 h, 此时锌、 铁的浸出率最高(锌: 98.69%, 铁: 92.36%). 氯化浸出系统主要参数如下: Cl⁻浓度 300 g/L, Fe³⁺浓度 25 g/L, 酸浓度 2 mol/L, 液固比 9 mL:1 g, 温度 90 °C, 浸出时间 0.5 h, 该条件下铅和银浸出率分别高达 98.87%和 96.74%; 最后, 对在富氧介质下使用 Cl⁻浸出银进行动力学研究, 发现浸出过程受内扩散控制, 活化能为 19.82 kJ/mol.