Asymmetry of diffusion permeability of bi-layer membranes

Modification of regenerated cellulose membrane based on thiol dendrimer

“…This fact is attributed to the different effect of the modifying agents on the structure of the cellulosic support: (i) a certain compaction in the structure of the RC/4-dendrimer membrane caused by a reduction of the free space among the cellulose chains as a result of the dendrimer inclusion; (ii) more open structure for the RC/4-S-DAB-CdSe membrane associated with the presence of the quantum dots, which is in agreement with the IS results. However, the three membranes exhibit the same kind of permeability-concentration dependence: a significant increase in P s values for the interval 10 −3 M-2 × 10 −2 M, but only a slight increase for NaCl concentrations higher than 2 × 10 −2 M. This kind of dependence is characteristic of charged single layer membranes (Filippov, Starov, Kononenko, & Berezina, 2008), and it is attributed to the contribution of both electrical and diffusional effects: electrical interactions are more significant at low solution concentrations, while at high C f values the electrical effect; associated to the membrane fixed charge might be neglected, since the high number of solution charges into the membrane structure is able to screen it. In this latter case, only the diffusive contribution is significant.…”

“…Analysis of the permeability-concentration results can give information on characteristic electrochemical parameters, by using the expression proposed by Filippov et al (2008) which includes both electrical and diffusive effects:…”

Surface modification of PTMSP membranes by plasma treatment: Asymmetry of transport in organic solvent nanofiltration

“…Later, the effect of asymmetry was also observed for some other systems, including the bilayered charged membranes, and the membranes modified by the hydrated zirconium oxide and polyaniline [2,15,16,[19][20][21][22][23]. Fascinating results were obtained for the transport asymmetry in the model systems based on the track-etched membranes.…”

“…Membrane modification is known to be a traditional approach that makes it possible to control the membrane characteristics and to achieve the desired performance of the heterogeneous membranes, for example, the effect of the transport asymmetry [2,15,16]. The effect of transport asymmetry was observed for the first time when studying the transport of electrolytes through the MK-40 and MK-41 ion-exchange membranes modified by tetrabutylammonium and sodium dodecylsulfate [17,18].…”

“…The effect of asymmetry was described within diverse theoretical models [2,15,16,[32][33][34]. In particular, the discrete model [32] considers the ion transport as a migration through active sites with different energies of bonds and their distribution along the pore length is non-uniform.…”