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A review of thermodynamic data for lanthanum, iron, and thorium applied to rare earth extraction
Hydrometallurgy ( IF 4.7 ) Pub Date : 2022-08-12 , DOI: 10.1016/j.hydromet.2022.105951
Vitor L. Gontijo , Leandro Augusto V. Teixeira , Daniel Majuste , Virginia S.T. Ciminelli

A consolidated and revised database for thermodynamic simulation of lanthanum (representing the rare earth elements), iron, and thorium in water, sulfate, and phosphate systems was built. Thermodynamic parameters (∆Gf°, ∆Hf°, and Sf°) collected from the original sources were compared with those reported in thermochemical software databases. The inconsistencies found in the latter were mainly ascribed to typographical errors, incorrect unit conversions, and errors generated by combining data from different sources. The Eh-pH diagrams illustrate the significant effects of data discrepancies on the stability regions of aqueous and solid species. The results obtained with the revised database helped the identification of operating windows for the selective precipitation of common impurities (e.g., Fe and Th) in rare earth extraction. In the presence of sulfate, the complex LaSO4+(aq) is the only stable species up to pH = 8 and then La(OH)3(s) is formed. In phosphate solutions, lanthanum salts precipitate at lower pH. The precipitation pH varies with the nature and crystal features of the different lanthanum phosphate phases. Under oxidizing conditions, wide operational windows favor the selective precipitation of Fe2O3(s) or FePO4.2H2O(s) at pH 1–5. Thorium hydroxide is formed at pH 4. The inclusion of phosphate complexes in the simulation expands the thorium solubility region from pH 4 to 6.5 (approximately), depending on phosphate concentration.



中文翻译:

用于稀土提取的镧、铁和钍的热力学数据综述

建立了水、硫酸盐和磷酸盐体系中镧(代表稀土元素)、铁和钍的热力学模拟综合和修订数据库。热力学参数(ΔG f °、ΔH f °和 S f°) 从原始来源收集的数据与热化学软件数据库中报告的数据进行比较。在后者中发现的不一致主要归因于印刷错误、不正确的单位转换以及组合来自不同来源的数据产生的错误。Eh-pH 图说明了数据差异对水性和固体物质稳定性区域的显着影响。使用修订后的数据库获得的结果有助于确定稀土萃取中常见杂质(例如 Fe 和 Th)的选择性沉淀操作窗口。在硫酸盐存在下,复杂的 LaSO 4 + (aq)是唯一稳定的物质,直到 pH = 8,然后是 La(OH) 3(s)形成了。在磷酸盐溶液中,镧盐在较低的 pH 值下沉淀。沉淀 pH 值随不同磷酸镧相的性质和晶体特征而变化。在氧化条件下,宽操作窗口有利于在 pH 1-5下选择性沉淀 Fe 2 O 3(s)或 FePO 4 .2H 2 O(s)。氢氧化钍在 pH 4 时形成。在模拟中加入磷酸盐络合物可将钍溶解范围从 pH 4 扩大到 6.5(大约),具体取决于磷酸盐浓度。

更新日期:2022-08-12
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