Solvent extraction and separation of Bi(III) and Sb(III) from HCl and HBr media using tri-<i>n</i>-octyl phosphine oxide (TOPO)

Abstract

The solvent extraction and separation of Bi(III) and Sb(III) from aqueous acidic media was investigated using Tri-<i>n</i>-octyl phosphine oxide (TOPO) in toluene. Quantitative extraction of Bi(III) was observed in acid range of 0.001-0.01M of HCl and 0.01-0.1M of HBr and that for Sb(III) extraction was incomplete in HCl media over the entire concentration range studied. The extraction of Sb(III) was quantitative in range 0.01-0.1M of HBr media. Effect of various other parameters such as reagent concentration, type of diluents, stripping agents, effect of diverse ions were studied to ascertain optimum conditions for the quantitative extraction and separation of Bi(III) and Sb(III). After equilibration Bi(III) from organic phase was stripped with 3M HNO₃ and determined spectrophotometrically by thiourea method at 470 nm, while Sb(III) was stripped with 9M H₂SO₄ and determined spectrophotometrically by iodide method at 425 nm. The effect of temperature on the extraction of Bi(III) and Sb(III) from HCl and HBr media has also been studied. The method is applicable to the analysis of pharmaceutical samples and alloys.