Water/nonionic sugar surfactant/oil microemulsion: efficient extraction of transition metal ions

Abstract

A ternary microemulsion system composed of sugar-based non-ionic surfactant, water as the polar phase, and ethyl acetate as the organic phase is used to extract transition metal ions (viz. copper, chromium, iron, cadmium, cerium, zirconium and molybdenum). We have constructed fish-shaped phase diagrams for formulating microemulsions. Once the metal ions were recovered from complexes, the absorbance values of the metal ions were determined spectrophotometrically. We have used an industrial-grade sugar-based non-ionic surfactant, which is a greener alternative for the formulation of a microemulsion system due to its superior physicochemical property and non-toxicity as compared to that of the conventional non-ionic surfactants. The UV–Vis. spectrophotometric investigations revealed that the absorbance increases with an increase in metal ion concentration in the aqueous phase and drops with an increase in potassium thiocyanate concentration. It has been inferred that a concentration of 0.05 mol/L potassium thiocyanate is the optimum concentration for recovering 0.05 mol L ^–1 molybdenum, cerium, and zirconium salts efficiently. The recovery efficiency was determined for all the metal ions, and it was found to be 88 % of the chromium (III) ions, 89 % of the molybdenum (VI) ions, 85 % of the cerium (IV) ions, and 91 % of the zirconium (IV) ions respectively.