Selective and Efficient Ligandless Water-in-Oil Emulsion Liquid Membrane Transport of Thorium(IV) Ions

Abstract

<em>The present paper concerns on the selective and very efficient transport of thorium(IV)</em><em> ions from aqueous solutions through an emulsion liquid membranes composed </em><em>by paraffin and a surfactant</em><em>, without carrier requirement. The influence of pH of the external aqueous</em><em> phase, the surfactant concentration in the membrane phase, the type, and concentration of the acid used in the receiving phase, the emulsification and mixing speed on the process efficiency </em><em>were examined and discussed. </em><em>The optimized conditions were: liquid paraffin as diluent, 5% surfactant </em><em>(nonionic polyamine surfactant</em><em> span-80), emulsification rate 5250 rpm, 15 min of stirring at 750 rpm in the extraction step, pH 5, oil/aqueous ratio of 3 in emulsions and using 0.3 M solution of sulfuric acid as stripping phase. Under optimized experimental conditions, thorium ions </em><em>were selectively and quantitatively transported from its mixture solution with lanthanides La(III), Sm(III),</em><em> Eu(III) and Er(III). The concentration of thorium ions, in single component transport experiment, was measured spectrophotometrically using </em><em>ArsenazoIII as the indicator at 655 nm, and the analysis of metal ions in competitive experiments was performed</em><em> by an ICP-OES instrument under recommended conditions provided by the instrument's manufacturer.</em>