A mechanistic study of uphill transport of metal ions through countertransport supported liquid membranes

The uphill transport of vanadium(IV) through a countertransport supported liquid membrane containing di(2-ethylhexyl)phosphoric acid (D2EHPA) as a mobile carrier was examined as it relates to its transport mechanism. The experiments were carried out in a stirred permeation cell with well-defined hydrodynamics. A transport model was presented that takes into account all possible resistances. The degree of uphill transport was found to depend strongly upon the transport mechanism, especially as the concentration of vanadium(IV) in the strip phase was greater than that in the feed phase. In general, the degree of uphill transport remained comparatively larger when the role of membrane diffusion was more significant.