Equilibrium and mechanism of samarium extraction from chloride medium using sodium salt of CYANEX 272

Kinetics and extraction of samarium(III) from aqueous chloride medium at constant ionic strength were studied using a sodium salt of bis(2,4,4-trimethylpentyl) phosphinic acid (CYANEX 272 (R)) in kerosene. The different parameters affecting the extraction of Sm(III) under equilibrium conditions were separately investigated to elucidate the stoichiometry of the extracted Sm(III) species. The extraction percent of the metal ion was found to increase with the increase in pH. On the basis of slope analysis method, the extracted species appears to be Sm(OH)A(2)center dot 2HA, where HA refers to CYANEX 272. The loaded organic phase was stripped with 1 M HCl in one stage at 1:1 (organic: aqueous) phase ratio. Kinetic studies on the extraction process were also carried out using a stirred Lewis cell. The results were interpreted by a reaction mechanism where the extraction process is controlled by a chemical reaction in the bulk phase rather than at the interface. (C) 2010 Elsevier B.V. All rights reserved.