M.T. Coll

Liquid-Liquid Extraction of Ir, Ru, and Rh from Chloride Solutions and Their Separation Using Different Commercially Available Solvent Extraction Reagents

Abstract The extraction of Ir, Ru, and Rh from their chloride solutions was carried out using different commercially available solvent extraction reagents. The extractants studied were Alamine 300, Alamine 336, Aliquat 336, Cyanex 921, Cyanex 923, Cyanex 471, Cyanex 272, LIX 54, LIX 860N‐I and tributyl phosphate (TBP). The distribution coefficients for the metals were determined under different concentrations of Cl− and H+ ions in the aqueous phase. The extraction data relating to the consecutive steps of stripping the metal species from the loaded organic phase were also recorded. The results showed that more than 90% of the Ir can be extracted using Alamine 300, Alamine 336, and Aliquat 336 when less than 0.2 M Cl− is present in the aqueous phase, and that quantitative stripping of Ir can be performed. For higher concentrations of Cl− in the aqueous phase, Cyanex 921 was found to be the best extractant for Ir, although the mixed extractants such as Alamine 336+LIX 54, Aliquat 336+LIX 54, and Cyanex 921+TBP were also found to be useful for the extraction of Ir from high concentration chloride solutions. For Ru, mixtures of extractants such as Alamine 336+LIX 54 and Aliquat 336+LIX 54 were found to be more effective for extraction, as well as better stripping of Ru was obtained from Ru loaded in such organic phases. The extraction of Rh proved to be difficult, and a maximum of only 31% extraction was achieved using Alamine 300 in the organic phase and a freshly prepared solution of the rhodium chloro complex in 1 M HCl in the aqueous phase. On the basis of these observations, a complete scheme for the individual separation of Ir, Ru, and Rh was proposed and tested with synthetic solutions of these metal chlorides. This resulted also in the development of a method for the separation and recovery of Ir, Ru, and Rh from hydrochloric acid solutions containing a high concentration of Cl− ions.

Studies on the Selective Separation of Ir(IV), Ru(III) and Rh(III) from Chloride Solutions using Alamine 336 in Kerosene

Abstract The liquid–liquid extraction of Ir(IV), Ru(III), and Rh(III) from chloride solution was studied under different conditions of aqueous‐ and organic‐phase component concentrations using Alamine 336 (A336) as an extractant. The differences obtained in the extraction of individual metals at different concentrations of A336 and HCl in the organic and aqueous phases respectively were used to mutually separate the three metals. A two‐step separation scheme was proposed. In the first step, Ir(IV) was selectively extracted using a solvent comprised of 0.1% A336 and 10% TBP in kerosene. In the second step, Ru(III) was quantitatively extracted using a solvent comprised of 5% A336 and 10% TBP in kerosene (all % v/v). Rh(III) was selectively left behind in the raffinate. Under controlled experimental conditions, we were able to eliminate the base metal ions commonly associated with Ir, Ru, and Rh during the extraction and the stripping process.

Transport of Zn(II), Fe(II), Fe(III) across polymer inclusion membranes (PIM) and flat sheet supported liquid membranes (SLM) containing phosphonium ionic liquids as metal ion carriers

ABSTRACT In this work transport of Zn(II), Fe(II) and Fe(III) ions from chloride aqueous solutions across polymer inclusion membranes (PIMs) and supported liquid membranes (SLMs) containing one of three phosphonium ionic liquids: trihexyl(tetradecyl)phosphonium chloride (Cyphos IL 101), trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate (Cyphos IL 104) and tributyl(tetradecyl)phosphonium chloride (Cyphos IL 167) as an ion carrier was reported. The results show that Zn(II) and Fe(III) are effectively transported through PIMs and SLMs, while Fe(II) transport is not effective. The highest values of initial flux and permeability coefficient of Zn(II) were noticed for SLM containing Cyphos IL 167. Cyphos IL 101-containing SLM is more stable than PIM.

Mathematical modeling of cadmium(II) solvent extraction from neutral and acidic chloride media using Cyanex 923 extractant as a metal carrier

This paper describes experimental work and the mathematical modeling of solvent extraction of cadmium(II) from neutral and acidic aqueous chloride media with a Cyanex 923 extractant in Exxol D-100. Solvent extraction experiments were carried out to analyze the influence of variations in the composition of the aqueous and organic phases on the efficiency of cadmium(II) extraction. In neutral and acidic chloride conditions, the extraction of cadmium(II) by the organophosphorous extractant Cyanex 923 (L) is based on the solvation mechanism of neutral H(n)CdCl((2+n)) species and the formation of H(n)CdCl((2+n))L(q) complexes in the organic phase, where n=0, 1, 2 and q=1, 2. The mathematical model of cadmium(II) extraction was derived from the mass balances and chemical equilibria involved in the separation system. The model was computed with the Matlab software. The equilibrium parameters for metal extraction, i.e. the stability constants of the aqueous Cd-Cl complexes, the formation constants of the acidic Cd-Cl species and the metal equilibrium extraction constants, were proposed. The optimized constants were appropriate, as there was good agreement when the model was fitted to the experimental data for each of the experiments.

Neodymium recovery from NdFeB magnet wastes using Primene 81R·Cyanex 572 IL by solvent extraction

The necessity of Rare Earth Elements (REEs) recycling is crucial to minimizing their supply risk and provide an alternative to greener technologies. Hence, the REEs recovery from NdFeB magnet wastes using cationic extractants by solvent extraction technique has been investigated in this research. Due to the difficulty in maintaining the aqueous pH in the industrial counter-current devices when extractants like Cyanex 272 or Cyanex 572 are used, the Primene 81R·Cyanex 572 ionic liquid has been synthesised to overcome this. 99.99% Nd(III) recovery with a purity of 99.7% from an aqueous mixture of Nd/Tb/Dy in chloride medium, the three representative REEs present in the NdFeB magnets wastes, has been achieved after two stages counter-current extraction process using 0.30 M of Primene 81R·Cyanex 572 ionic liquid (1:4 A:O ratio) diluted in Solvesso 100, without any aqueous pH conditioning.