Possibilities and limitations in separating Pt(iv) from Pd(ii) combining imidazolium and phosphonium ionic liquids

• Published in: Dalton transactions : an international journal of inorganic chemistry 2015-01, Vol.44 (46), p.2131-2138
• Main Authors: Papaiconomou, Nicolas, Svecova, Lenka, Bonnaud, Céline, Cathelin, Loïc, Billard, Isabelle, Chainet, Eric
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Anions; Aqueous solutions; Bromides; Chemical Sciences; Coefficients; Extraction; Ionic liquids; Platinum; Separation
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c5dt03791c

An investigation on a process designed for separating Pt( iv ) and Pd( ii ) dissolved in acidic aqueous solution containing HCl using two ionic liquids, 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([OMIM][NTf 2 ]) and trihexyltetradecylphosphonium bromide (Cyphos 102), is presented. To this end, the single extraction of platinum in [OMIM][NTf 2 ] has been investigated as a function of the initial concentration of Pt( iv ) ions dissolved in 1 M HCl. The distribution coefficient for Pt( iv ), present in water as a PtCl 6 2− anion, decreases with the concentration of Pt( iv ). The extraction of Pd( ii ) towards [OMIM][NTf 2 ] or Cyphos 102 as a function of the concentration of HCl in the aqueous phase is also reported. Pd( ii ), present as PdCl 4 2− in water, is not extracted using [OMIM][NTf 2 ]. On the other hand, the distribution coefficients of Pd( ii ) using Cyphos 102 are above 2000. In this ionic liquid, Pd( ii ) is extracted as a PdBr 4 2− anion. Separation of Pt( iv ) from Pd( ii ) was then carried out starting from aqueous phases containing 1 M HCl and various initial concentrations of Pt( iv ). The influence of the number of extraction steps using [OMIM][NTf 2 ] on the extraction of Pt( iv ) was also studied. Unlike the results obtained from single extraction experiments of Pt( iv ), consecutive extraction of Pt( iv ) in water using [OMIM][NTf 2 ] does not improve significantly the extraction of this metal ion. The second step of the extraction process carried out using Cyphos 102 leads to the quantitative extraction of Pd( ii ) and Pt( iv ) remaining in the aqueous phase. The extraction of Pt( iv ) using [OMIM][NTf 2 ] and of Pd( ii ) using (Cyphos 102) is reported. Pd( ii ) was extracted quantitatively using Cyphos 102. Separation of Pt( iv ) from Pd( ii ) was carried out in a simple two step process.