Separation of precious metals by split-anion extraction using water-saturated ionic liquids,Green Chemistry

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Separation of precious metals by split-anion extraction using water-saturated ionic liquids
Green Chemistry ( IF 9.3 ) Pub Date : 2020-11-06 , DOI: 10.1039/d0gc02356f
Viet Tu Nguyen _{1,

2,

3,

4} , Sofía Riaño _{1,

2,

3,

4} , Koen Binnemans _{1,

2,

3,

4}

Affiliation

A split-anion solvent extraction process was developed for the separation of precious metal ions Au(III), Pt(IV), Pd(II) and Rh(III) from aqueous chloride media using water-saturated ionic liquids. The metal extraction and stripping behavior of the chloride form [A336][Cl], bromide form [A336][Br] and the iodide form [A336][I] of the quaternary ammonium ionic liquid Aliquat 336 were compared. The three ionic liquids extracted Au(III), Pd(II) and Pt(IV) quantitatively in most cases, whereas the co-extraction of Rh(III) was strongly dependent on the acidity and the chloride concentration. Among the studied ionic liquids, [A336][I] achieved the highest separation factors between Pd(II)/Rh(III), Pt(IV)/Rh(III), and Au(III)/Rh(III) at 6 mol L⁻¹ Cl⁻. Additionally, the selective stripping of the individual metal ions Pd(II), Au(III), and Pt(IV) was only possible from loaded [A336][I] using ammonia solution (NH₄OH), sodium thiosulfate (Na₂S₂O₃), and thiourea ((NH₂)₂CS), respectively. A closed-loop flow sheet was designed for the recovery of the precious metals from chloride media using split-anion extraction with [A336][I]. The integrated process was demonstrated to be suitable for the purification of Rh(III), Pt(IV) and Pd(II) from a complex metal feed such as the leachate of spent automotive catalysts. The ionic liquid-based split-anion extraction process is simple, selective and effective for the sustainable separation of the precious metals, using only one green extractant [A336][I], which can be regenerated for consecutive extraction-stripping cycles.

中文翻译：

使用水饱和离子液体的分离阴离子萃取分离贵金属

开发了一种分离阴离子溶剂萃取工艺，该工艺使用水饱和离子液体从氯化物水溶液中分离贵金属离子Au（III），Pt（IV），Pd（II）和Rh（III）。比较了季铵离子液体Aliquat 336的氯化物形式[A336] [Cl]，溴化物形式[A336] [Br]和碘化物形式[A336] [I]的金属萃取和汽提行为。在大多数情况下，这三种离子液体可定量萃取Au（III），Pd（II）和Pt（IV），而Rh（III）的共萃取）在很大程度上取决于酸度和氯化物浓度。在研究的离子液体中，[A336] [I]在6时达到了Pd（II）/ Rh（III），Pt（IV）/ Rh（III）和Au（III）/ Rh（III）之间最高的分离系数摩尔大号^-1氯^-。此外，只有使用氨溶液（NH ₄ OH），硫代硫酸钠（Na ₂）从负载的[A336] [I]中选择性剥离单个金属离子Pd（II），Au（III）和Pt（IV）S ₂ O ₃）和硫脲（（NH₂）₂ CS）。设计了一种闭环流程图，用于使用[A336] [I]的分离阴离子萃取法从氯化物介质中回收贵金属。事实证明，该集成方法适用于从复杂的金属进料（例如废旧汽车催化剂的浸出液）中纯化Rh（ III），Pt（ IV）和Pd（ II）。基于离子液体的分裂阴离子萃取工艺简单，选择性且有效地可持续分离贵金属，仅使用一种绿色萃取剂[A336] [I]，即可将其再生以进行连续的萃取-汽提循环。

更新日期：2020-11-06

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