Enhancing Metal Separations by Liquid–Liquid Extraction Using Polar Solvents

Li, Zheng; Zhang, Zidan; Smolders, Simon; Li, Xiaohua; Raiguel, Stijn; Nies, Erik; Vos, Dirk De; Binnemans, Koen

doi:10.1002/chem.201901800

Cited by 35 publications

(33 citation statements)

References 33 publications

(69 reference statements)

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“…The preferred solvent pairs must have (i) low environmental impact, (ii) low mutual solubility, (iii) rapid phase disengagement, (iv) good solubility of the extractant in the less-polar phase, and (v) good solubility of the to-be-extracted metal salts in the more-polar phase . Recent studies on NASX have shown that selectivity can be quite different from that observed in conventional extraction from aqueous feed solutions. − …”

Section: Introductionmentioning

confidence: 99%

Solvometallurgical Recovery of Platinum Group Metals from Spent Automotive Catalysts

Nguyen

Riaño

Aktan

et al. 2020

ACS Sustainable Chem. Eng.

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Extraction and separation of platinum group metals (PGMs) from secondary raw materials are usually carried out via hydrometallurgical processes. These processes use strongly oxidizing acidic solutions, such as aqua regia or hydrochloric acid in the presence of chlorine gas, which may have negative environmental impacts and are dangerous. In this paper, a solvometallurgical approach was developed for the sustainable recovery of PGMs from spent automotive exhaust catalysts. The PGMs were leached using FeCl3 or CuCl2 as oxidizing agents in the organic solvents dimethyl sulfoxide (DMSO) or acetonitrile (CH3CN). Palladium was quantitatively dissolved in CuCl2/CH3CN, CuCl2/DMSO, and FeCl3/DMSO with only 10–20% codissolution of Pt and Rh. By adjusting the concentration of the oxidizing agent in CH3CN, Pd was selectively leached with 0.01 mol L–1 FeCl3, whereas Pt and Rh could be dissolved in a more concentrated FeCl3 solution (0.3 mol L–1). The solvoleaching of PGMs was investigated in depth by UV–vis spectra and electrochemical properties (i.e., cyclic voltammograms and formal reduction potentials of the Fe3+/Fe2+ and Cu2+/Cu+ couples in DMSO and CH3CN). After leaching, CH3CN was easily recovered by distillation. The Pd-containing residue was dissolved in water, from which Pd sponge was produced by reduction with formic acid. Meanwhile, the residue containing the solid chloride salts of Fe(III), Pt(IV), and Rh(III) was redissolved in ethylene glycol or DMSO for further purification by nonaqueous solvent extraction (NASX). The ionic liquid Aliquat 336 diluted in p-cymene showed selective extraction of Fe(III) and Pt(IV) while leaving Rh(III) in the raffinate. The loaded ionic liquid was recycled after selective stripping of Fe(III) with water and Pt(IV) with a thiourea solution. A flow sheet comprising solvoleaching and NASX is proposed. The closed-loop solvoleaching of PGMs with less-hazardous chemicals (FeCl3/CH3CN) avoids the emission of toxic or flammable gases (Cl2, H2, and NO x ) while reducing the consumption of acids and bases and limiting the generation of waste water. In addition, NASX with an ionic liquid may be a more sustainable alternative for the conventional separation of PGMs.

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Section: Introductionmentioning

confidence: 99%

Solvometallurgical Recovery of Platinum Group Metals from Spent Automotive Catalysts

Nguyen

Riaño

Aktan

et al. 2020

ACS Sustainable Chem. Eng.

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“…Over the last decades the interest in developing sustainable chemical processes has grown, and with it the need for new solvents that follow the fundamentals of green chemistry [1] . For example liquid‐liquid – i. e. solvent – metal extraction offers a number of advantages compared to other techniques, [2] but the employed solvents are often toxic and expensive to dispose of. The last few years have seen an increasing demand of novel sustainable solvents for metal ions extraction [3] .…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Bonding and Vaporization Thermodynamics in Hexafluoroisopropanol‐Acetone and ‐Methanol Mixtures. A Joined Cluster Analysis and Molecular Dynamic Study

et al. 2021

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Binary mixtures of hexafluoroisopropanol with either methanol or acetone are analyzed via classical molecular dynamics simulations and quantum cluster equilibrium calculations. In particular, their populations and thermodynamic properties are investigated with the binary quantum cluster equilibrium method, using our in-house code Peacemaker 2.8, upgraded with temperature-dependent parameters. A novel approach, where the final density from classical molecular dynamics, has been used to generate the necessary reference isobars. The hydrogen bond network in both type of mixtures at molar fraction of hexafluoroisopropanol of 0.2, 0.5, and 0.8 respectively is investigated via the molecular dynamics trajectories and the cluster results. In particular, the populations show that mixed clusters are preferred in both systems even at 0.2 molar fractions of hexafluoroisopropanol. Enthalpies and entropies of vaporization are calculated for the neat and mixed systems and found to be in good agreement with experimental values.

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“…9 Recently, a series of non-aqueous SX systems have been investigated and several enhanced separations have been obtained. [10][11][12][13][14][15] The substitution of water by polar organic solvents changes the solvation of metal cations in the polar solvent, and the relative solubility of the complexes between the two immiscible phases also affects the extraction equilibrium. 15 The extraction of metals from polar organic solvents can be significantly altered by changing polar solvents.…”

Section: Introductionmentioning

confidence: 99%

“…The use of polar solvents instead of water in the extraction of metals is called non‐aqueous solvent extraction (NASX) 9 . Recently, a series of non‐aqueous SX systems have been investigated and several enhanced separations have been obtained 10‐15 . The substitution of water by polar organic solvents changes the solvation of metal cations in the polar solvent, and the relative solubility of the complexes between the two immiscible phases also affects the extraction equilibrium 15 .…”

Section: Introductionmentioning

confidence: 99%

Ethylammonium nitrate enhances the extraction of transition metal nitrates by tri‐n‐butyl phosphate (TBP)

Zhang

Onghena

et al. 2021

AIChE Journal

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Several molecular polar solvents have been used as solvents of the more polar phase in the solvent extraction (SX) of metals. However, the use of hydrophilic ionic liquids (ILs) as solvents has seldomly been explored for this application. Here, the hydrophilic IL ethylammonium nitrate (EAN), has been utilized as a polar solvent in SX of transition metal nitrates by tri-n-butyl phosphate (TBP). It was found that the extraction from EAN is considerably stronger than that from a range of molecular polar solvents. The main species of Co(II) and Fe(III) in EAN are likely [Co(NO 3) 4 ] 2− and [Fe(NO 3) 4 ] − , respectively. The extracted species are likely Fe(TBP) 3 (NO 3) 3 and a mixture of Co(TBP) 2 (NO 3) 2 and Co(TBP) 3 (NO 3) 2. The addition of H 2 O or LiCl to EAN reduces the extraction because the metal cations coordinate to water molecules and chloride ions stronger than to nitrate ions. This study highlights the potential of using hydrophilic ILs to enhance SX of metals.

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Enhancing Metal Separations by Liquid–Liquid Extraction Using Polar Solvents

Cited by 35 publications

References 33 publications

Solvometallurgical Recovery of Platinum Group Metals from Spent Automotive Catalysts

Solvometallurgical Recovery of Platinum Group Metals from Spent Automotive Catalysts

Hydrogen Bonding and Vaporization Thermodynamics in Hexafluoroisopropanol‐Acetone and ‐Methanol Mixtures. A Joined Cluster Analysis and Molecular Dynamic Study

Ethylammonium nitrate enhances the extraction of transition metal nitrates by tri‐n‐butyl phosphate (TBP)

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