Abstract Rare earth elements (REEs) possess distinctive physical and chemical properties and are mainly extracted from several rare earth (RE) and ion-absorbing type RE ores. Traditional RE sources are unable to meet the global demand, making it necessary to explore other resources for the extraction of rare REEs. While this is possible, the recovery of REEs from the leach residue of such resources is uneconomical due to the enormous consumption of mineral acids. H2SO4–H3PO4 mixed acid decomposition is an effective method for leaching tungsten from scheelite and is evaluated in this study for its efficient extraction of tungsten and REEs from the same mineral. The scheelite used in this study contains REEs such as lanthanum, cerium, and neodymium. The properties of the REs in the leaching system are used to evaluate our method. Additionally, the effects of the reaction conditions on the leaching of tungsten and REEs are investigated. The results show that increasing the reaction temperature and H2SO4 concentration favors the leaching process. However, high H2SO4 concentration also promotes the transformation of gypsum from CaSO4·2H2O to CaSO4, which affects the leaching process negatively. Further, excessive H3PO4 concentration increases the viscosity of the leaching solution. Increasing the liquid–solid ratio is beneficial for the dissolution of scheelite. The addition of an appropriate amount of CaSO4·2H2O promotes the leaching of tungsten and REEs but the addition of PEG-400 does not. In terms of the experimental conditions used in this study, the leaching efficiency of W, La, Ce, and Nd can reach approximately 100%, 96.6%, 66.6%, and 57.1%, respectively. After the circulation leaching process, the concentrations of tungsten and the REEs in the leach liquor are increased, which proves these materials can be efficiently leached from scheelite using the H2SO4–H3PO4 mixed acid.

中文翻译：

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H2SO4-H3PO4混酸分解从白钨矿中浸出钨和稀土元素

摘要 稀土元素（REEs）具有独特的理化性质，主要从几种稀土（RE）和离子吸收型稀土矿中提取。传统稀土资源无法满足全球需求，需要探索其他资源来提取稀有稀土。虽然这是可能的，但由于矿物酸的大量消耗，从这些资源的浸出残渣中回收 REE 是不经济的。H2SO4–H3PO4 混合酸分解是从白钨矿中浸出钨的有效方法，本研究评估了其从同一矿物中有效提取钨和稀土元素的方法。本研究中使用的白钨矿含有稀土元素，如镧、铈和钕。浸出系统中 RE 的特性用于评估我们的方法。此外，研究了反应条件对钨和稀土元素浸出的影响。结果表明，提高反应温度和 H2SO4 浓度有利于浸出过程。然而，高浓度的 H2SO4 也促进了石膏从 CaSO4·2H2O 向 CaSO4 的转化，从而对浸出过程产生负面影响。此外，过高的 H3PO4 浓度会增加浸出液的粘度。提高液固比有利于白钨矿的溶解。适量的CaSO4·2H2O的加入促进了钨和稀土元素的浸出，而PEG-400的加入则没有。就本研究使用的实验条件而言，W、La、Ce 和 Nd 的浸出效率分别可达到约 100%、96.6%、66.6% 和 57.1%。