湿法冶金

针对甘肃某湿法炼锌热酸浸出液存在的高铁、高酸及伴生铟损失问题，研究了采用还原—氧化赤铁矿法除铁，考察了还原终点、初始自由酸质量浓度、氧化温度、反应时间和氧分压对除铁行为的影响。试验结果表明：ρ(Fe²⁺)/ρ(TFe)控制在0.85～0.90可避免Fe³⁺非均匀水解并促进赤铁矿晶化；初始自由酸浓度过低会加剧细粒沉淀及Zn、In夹带，过高则抑制水解、残铁升高；酸平衡核算显示终酸浓度受初始酸和沉铁量共同控制；在ρ(Fe²⁺)/ρ(TFe) =0.85、初始自由酸质量浓度18 g/L、氧化温度180 ℃、氧分压0.6 MPa、反应时间2 h优化条件下，除铁率达99.0%，溶液中残铁质量浓度0.26 g/L，Zn、In损失率分别控制在1.1%和4.2%。XRD/SEM分析结果表明，沉铁渣以赤铁矿为主，杂质相减少，颗粒长大(D₅₀由3.2 μm增至12.7 μm)，过滤比阻由8.2×10¹¹ m/kg降至2.5×10¹¹ m/kg。该法可实现高效除铁、酸平衡调控及有价金属损失控制，为复杂锌浸出体系中除铁工艺的优化及有价金属回收提供参考。

To address the problems of high iron concentration， high acidity， and associated indium loss in a hot acid leaching solution from a zinc hydrometallurgical plant in Gansu Province， iron removal by the reduction－oxidation hematite process was investigated. The effects of reduction endpoint， initial free acid concentration， oxidation temperature， reaction time， and oxygen partial pressure on iron removal behavior were systematically examined. The results showed that controlling the ρ(Fe²⁺)/ρ(TFe) ratio at 0.85-0.90 could suppress non-uniform hydrolysis of Fe³⁺ and promote hematite crystallization. An excessively low initial free acid concentration intensified the formation of fine precipitates and the entrainment losses of Zn and In， whereas an excessively high acid concentration inhibited Fe³⁺ hydrolysis and increased the residual iron concentration. Acid-balance calculations indicated that the final acid concentration was jointly controlled by the initial acid concentration and the amount of iron precipitated. Under the optimized conditions of ρ(Fe²⁺)/ρ(TFe) = 0.85， initial free acid concentration of 18 g/L， oxidation temperature of 180 ℃， oxygen partial pressure of 0.6 MPa， and reaction time of 2 h， the iron removal rate reached 99.0%， with a residual iron concentration of 0.26 g/L， while the Zn and In loss rates were controlled at 1.1% and 4.2%， respectively. XRD and SEM analyses showed that the iron precipitate was mainly composed of hematite， with reduced impurity phases and increased particle size. The D₅₀ increased from 3.2 μm to 12.7 μm， while the filtration specific resistance decreased from 8.2 × 10¹¹ to 2.5 × 10¹¹ m/kg. The results demonstrate that the reduction-oxidation hematite process can achieve efficient iron removal， effective acid-balance regulation， and reduced valuable-metal losses， providing a reference for the optimization of iron removal and valuable-metal recovery from complex zinc leaching solutions.