Transport mechanism of chromium(III) through the unmixed bulk liquid membrane containing dinonylnaphthalenesulfonic acid as a carrier

Cr(III) transport through the unmixed bulk liquid membrane containing di-nonylnaphthalenesulfonic acid (DNNSA) as a carrier has been investigated. The concentration of chromium in the strip solution and the viscosity of the membrane versus DNNSA concentration in it was measured. The results indicated that in the present of threshold carrier content in the membrane (near 0.32 mol dm−3) the common facilitated transport is changing to the another kind of transport which is more effective than a facilitated diffusion mechanism. The maximum in the curve of Cr(III) flux versus DNNSA concentration was found and increase of membrane viscosity versus carrier concentration was observed. It seems that in the threshold carrier concentration in the membrane the distance between neighboring molecules decreases and there is a possibility to a chromium ions jump from one complexing center to another. We suppose that might be a “jumping” transport theoretically predicted by Cussler et al. [27]. It was shown that to obtain “jumping” effect a system needs a certain time-lag (about 0.5 h). During this time the new transport structure is self-organized inside the membrane.