Emulsion liquid membrane in the selective extraction of Dy

Abstract

Due to comparable ionic radii, lanthanoids are known to have similar physical and chemical properties. Separation of lanthanoids from one another is therefore a challenging task. Such crucial separation chemistry could be performed with the help of solvent extraction technique. In order to overcome the associated problems based on solvent extractions, the emulsion liquid membrane based method has been applied to do the selective and efficient extraction of the lanthanoid Dy. This work describes the role of emulsion liquid membranes for the selective extraction of Dy(III) ion with the help of aniline yellow dye at pH 3 medium. The emulsion was prepared using different oils viz, mustard oil, coconut oil and palm oil as the organic phase. The complexation of the lanthanoids (La(III), Ce(III), Ce(IV), Pr(III), Gd(III), Sm(III) and Dy(III)) with aniline yellow (AY) and benzene azo naphthylamine (BAN) dye was studied using UV-Vis spectrophotometer at three different pH (pH 1, pH 3 and pH 5) conditions. The complexation was observed at pH 3 and 5 for only Pr(III) and Dy(III) with both the dyes having high association constant values (∼106 M-1). The emulsion liquid membrane (ELM) prepared with mustard oil, coconut oil and palm oil at pH 3 showed zeta potential value − 30.60 mV, − 27.00 mV and − 35.90 mV respectively. Selective extraction of the Dy-AY complex was obtained for the ELM prepared with mustard oil at pH 3 medium (90%). After extraction of the Dy-AY complex, the zeta potential decreased to − 41.80 mV for the ELM. The effect of stirring time, pH of the medium and the concentrations of the feed solutions have positive correlations towards the extraction process. After the extraction process, the oil reach phase was demulsified using a mixture of organic solvents and the extracted metal ion was back-extracted with the help of cation exchange resin. 88% of the extracted Dy could be back extracted upon demulsification.