TEMPERATURE-INDUCED PHASE-SEPARATION OF NONIONIC POLYOXYETHYLATED SURFACTANT AND APPLICATION TO EXTRACTION OF METAL THIOCYANATES

Poly(oxyethylene) (7.5) nonylphenyl ether is utilized for the cloud point ion-pair extraction of thiocyanato complexes of transition-metal ions. The cloud point of this surfactant is sensitive to the concentration of SCN-. This phenomenon can be explained by the repulsive interaction between the surfactant chains due to the partition of SCN- into the micelle, which is experimentally verified by ion-chromatographic determination of SCN- in the surfactant-rich phase. Results obtained in the extraction study are identical with those in the usual solvent extration, suggesting that the extraction occurs along a similar mechanism. However, plots based on an equation derived, from an extraction model indicate that a neutral 1:2 complex is also extracted into the surfactant-rich phase to a significant extent.