Abstract In this study, a novel hydrometallurgical process consisting of hydrochloric acid three-stage countercurrent leaching and solvent extraction was proposed to recover rare earth oxide (REO) from the rare earth polishing powder waste (REPPW). The effects of HCl concentration, liquid–solid ratio (L/S ratio), temperature and time on the leaching yields of rare earths (in REO) and aluminum (in Al2O3) were studied. The result shows that the leaching yields of REO and Al2O3 are 90.96% and 43.89% respectively under the optimum leaching parameters of HCl concentration = 8.00 mol/L, L/S ratio = 4 mL/g, leaching temperature = 353 K and leaching time = 180 min. Meanwhile, the leaching kinetics of REO and Al2O3 were investigated in this study. The leaching behaviors of REO and Al2O3 follow a shrinking sphere/core model and the general leaching process is controlled by the surface chemical reaction. The leaching activation energies of REO and Al2O3 are 9.86 and 13.68 kJ/mol, respectively. The leaching yield of each substance in three-stage countercurrent leaching is improved substantially compared with single-stage leaching, with a change from 90.96% to 95.38% for REO and from 43.89% to 46.22% for Al2O3, respectively. Especially, the total concentration of REO in three-stage countercurrent leaching solution is greatly increased to above 300 g/L, and the acidity of which is decreased to ca. pH = 2, which is conducive to subsequent solvent extraction directly. High purity REO (99.92%) is obtained by solvent extraction separation, oxalate precipitation and calcination. The total recovery yield of REO is 85.13%.

中文翻译：

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盐酸浸出抛光粉废料中稀土和铝的动力学研究

摘要 在本研究中，提出了一种由盐酸三段逆流浸出和溶剂萃取组成的湿法冶金新工艺，用于从稀土抛光粉废料 (REPPW) 中回收稀土氧化物 (REO)。研究了 HCl 浓度、液固比（L/S 比）、温度和时间对稀土（在 REO 中）和铝（在 Al2O3 中）浸出率的影响。结果表明，在HCl浓度=8.00 mol/L、L/S比=4 mL/g、浸出温度=353 K和浸出时间的最佳浸出参数下，REO和Al2O3的浸出率分别为90.96%和43.89% = 180 分钟。同时，本研究还研究了 REO 和 Al2O3 的浸出动力学。REO 和 Al2O3 的浸出行为遵循收缩球/核模型，一般浸出过程由表面化学反应控制。REO和Al2O3的浸出活化能分别为9.86和13.68 kJ/mol。三段逆流浸出各物质的浸出率较单段浸出有大幅度提高，REO分别从90.96%提高到95.38%，Al2O3从43.89%提高到46.22%。特别是三级逆流浸出液中REO的总浓度大大提高到300g/L以上，酸度降低到约300g/L。pH=2，有利于后续溶剂直接提取。通过溶剂萃取分离、草酸盐沉淀和煅烧得到高纯度REO（99.92%）。