The aim of this study was to recover Sc as the main product and Fe as a by-product from Hungarian bauxite residue/red mud (RM) waste material by solvent extraction (SX). Moreover, a new technique was developed for the selective separation of Sc and Fe from real RM leachates. The presence of high Fe content (∼38%) in RM makes it difficult to recover Sc because of the similarity of their physicochemical properties. Pyrometallurgical and hydrometallurgical methods were applied to remove the Fe prior to SX. Two protocols based on organophosphorus compounds (OPCs) were proposed, and the main extractants were evaluated: bis(2-ethylhexyl) phosphoric acid (D2EHPA/P204) and tributyl phosphate (TBP). The results showed that SX using diethyl ether and tri-n-octylamine (N₂₃₅) was efficient in extracting Fe(III) from the HCl leachate as HFeC1₄. Over 97% of Sc was extracted by D2EHPA extractant under the following conditions; 0.05 mol/L of D2EHPA concentration, A/O phase ratio of 3:1, pH 0–1, 10 min of shaking time, and a temperature of 25 °C. Sc(OH)₃ as a precipitate was efficiently obtained by stripping from the D2EHPA organic phase by 2.5 mol/L of NaOH with a stripping efficiency of 95%. In the TBP system, 99% of Sc was extracted under the following conditions: 12.5% vol of TBP, an A/O phase ratio of 3:1, 10 min of shaking time, and a temperature of 25 °C. The Sc contained in the TBP organic phase could be efficiently stripped by 1 mol/L of HCl with a stripping efficiency of 92.85%.

本研究的目的是通过溶剂萃取 (SX) 从匈牙利铝土矿残渣/赤泥 (RM) 废料中回收作为主要产品的 Sc 和作为副产品的 Fe。此外，还开发了一种从真正的 RM 渗滤液中选择性分离 Sc 和 Fe 的新技术。RM 中高铁含量（~38%）的存在使得难以回收 Sc，因为它们的物理化学性质相似。在 SX 之前，应用火法冶金和湿法冶金方法去除 Fe。提出了两种基于有机磷化合物 (OPCs) 的方案，并对主要萃取剂进行了评估：双 (2-乙基己基) 磷酸 (D2EHPA/P2O4) 和磷酸三丁酯 (TBP)。结果表明，SX使用乙醚和三正辛胺（N ₂₃₅) 在从 HCl 浸出液中以 HFeC1 ₄形式提取 Fe(III) 方面是有效的。D2EHPA萃取剂在以下条件下萃取了97%以上的Sc；D2EHPA 浓度 0.05 mol/L，A/O 相比 3:1，pH 0-1，振荡时间 10 分钟，温度 25 °C。用 2.5 mol/L 的 NaOH 从 D2EHPA 有机相中反萃取出Sc(OH) ₃沉淀物，反萃取效率为 95%。在 TBP 系统中，99% 的 Sc 在以下条件下被提取：12.5% vol 的 TBP、3:1 的 A/O 相比、10 分钟的振荡时间和 25°C 的温度。TBP有机相中所含的Sc可被1 mol/L HCl高效汽提，汽提效率为92.85%。