Non-Dispersive Extraction of Chromium(VI) by Cyphos IL102/Solvesso 100 Using the Pseudo-Emulsion-Based Strip Dispersion Membrane Operation.

Abstract

The removal of chromium(VI) from an acidic (HCl) medium through non-dispersive extraction with strip dispersion (NDXSD) was investigated using a microporous PVDF membrane support in a permeation cell. The ionic liquid Cyphos IL102 (phosphonium salt) in Solvesso 100 was used as an organic phase. In NDXSD, the stripping phase (NaOH) is dispersed in the organic phase on the cell side with an impeller stirrer adequate to form a strip dispersion. This pseudo-emulsion phase (organic + strip solutions) provides a constant supply of the Cyphos IL102/Solvesso 100 to the membrane phase. Various hydrodynamic and chemical parameters, such as variation in the feed and pseudo-emulsion stirring speeds, HCl and Cr(VI) concentrations in the feed phase, and carrier concentration, were investigated. Results indicated that the best chromium(VI) transport was obtained under the following conditions: feed and pseudo-emulsion stirring speeds of 1000 min-1 and 600 min-1, respectively; an HCl concentration in the feed phase of 0.1 M; a chromium concentration of 0.01 g/L in the same phase; and carrier concentration in the organic phase in the 2-5-10% v/v range. From the experimental data, several mass transfer coefficients were estimated: a bulk diffusion coefficient of 3.1·10-7 cm2/s and a diffusion coefficient of 6.1·10-8 cm2/s in the membrane phase and mass transfer coefficients in the feed (5.7·10-3 cm/s) and membrane phases (2.9·10-6 cm/s). The performance of the present system against other ionic liquids and the presence of base metals in the feed phase were investigated.