Unusually Slow Extraction Rate and Mechanism of Iron(III) with Trifluoroacetylacetone in Triton X-100 Micellar System. Part II. Interfacial Transport

Abstract

In order to learn reasons of the slow formation/extraction rate of iron(III) with trifluoroacetylacetone in Triton X-100 micellar system, the rate of material transport of the extractable tris-complex from the bulk aqueous phase to the micellar pseudophase was investigated at 298 K. The rate was successfully measured using a micellar-concentration-jump stopped-flow technique; the rate was independent of the ligand, the hydrogen ion and the Triton X-100 concentrations of the starting solutions while it was first order with respect to the surfactant concentration of the resulting solutions. The rate of transport was slow enough to reduce the rates of the overall extraction reactions. The rate of formation/extraction in the micellar system was recalculated as if the extraction of the tris-complex was negligibly slow; the corrected rate constant agreed well with that obtained in the aqueous solution. The slow extraction rate observed in the trifluoroacetylacetone-Triton X-100 micellar system was concluded to be due to the slow interfacial transport of the tris-complex.