Facilitated transport via carrier‐mediated diffusion in membranes: Part I. Mechanistic aspects, experimental systems and characteristic regimes

Abstract

Experimental Systems and CharacteristicCarrier-mediated transport in membranes as a globally nonreactive process is distinguished from film theory with chemical reaction and other facilitated diffusion phenomena. With the concept of stoichiometric and system invariants, an approach is developed for the analysis of carriermediated transport with multiple permeants involving multiple reactions in the membrane. Approximate solutions of the requisite differential equations according to the relative importance of diffusion and reaction rates are reviewed, as well as typical experimental studies. Criteria for evaluating whether a membrane is in the diffusion or equilibrium regime are given, and, in the latter case, the effects of some system parameters are given, for example, binding constants, competitive permeants. Advances in membrane technology have made it possible in recent years to manufacture membranes in diverse forms such as sheets, tubes, and hollow fibers. In most current applications to separations processes, the membrane functions as a physical diffusion barrier or simple (micro-) sieve. However, &rough recent studies on models of biological membranes, it has become evident that artificial membranes, often in the form of liquid films, can be made functionally very specific in their properties by incorporating mobile or partially mobile compounds within the membrane structure which selectively react with a restricted class of permeants, for example, in ionspecific electrodes. These compounds serve effectively as carriers which not only can render the membrane very specific in its transport properties but also can enhance the relative rate at which the preferred permeants diffuse across the barrier.While various mechanistic models have been proposed to describe carrier-mediated transport in membranes, those models based on diffusion accompanied by chemical reaction have received the most theoretical and experimental study and are the main subject of this review. Recent studies of carriepmediated membrane transport of this type has led to a basic and more precise understanding of the effect of the major parameters involved, including the reaction kinetics, equilibrium (binding) constant, membrane diffusivities, concentration gradients, membrane thickness, and solubilities of the permeants in the membrane phase.Currently available numerical methods, together with various asymptotic and approximate analytic methods, based on the respective concepts of weak gradients or fast and slow reactions, allow one to estimate with a good deal of confidence the response of a particular carriermediated membrane to a variety of operational conditions. Apart from their potential for direct applications to processes such as drug transport into cells, the concepts and methods developed in these studies, relating to reaction boundary-layer analysis, global nonreactivity, and competitive interactions with carriers, suggest similar theoretical treatments in a diversity of related phenomena, such as facilitated heat transfer, ion-...

Facilitated transport of CO2 in novel PVAm/PVA blend membrane

“…Besides, the diffusion of N 2 is more comparable with that of CO 2 when at high pressure and without facilitated effect, which can also account for the loss of selectivity. Schultz [45] related the thickness of carrier-mediated transport membranes with the ratio between the carrier-mediated rate and the Fickian diffusion rate with the second Damköhler number, l 2 /(Dt 0.5 ), in which l is membrane thickness, D is the diffusion coefficient of the free component and t 0.5 , half time of the complexation reaction. An optimal thickness for different operating pressures is thus possible to predict according to the Damköhler number.…”

A compatible crosslinker for enhancement of CO2 capture of poly(amidoamine) dendrimer-containing polymeric membranes

“…50, and then decreases with increase in p(CO 2 ), which is most likely due to decrease in Q(CO 2 ) while Q(H 2 ) stays constant. The CO 2 permeation undergoes on a facilitated transportation via carrier-mediated diffusion mechanism [22]. Without 4GMAP, the polymeric membranes cannot tolerate under pressure above 0.23 MPa of p(CO 2 ) and 0.29 MPa of total pressure.…”

Mathematical modelling of CO2 facilitated transport through liquid membranes containing amines as carrier

“…Due to mass transfer accompanied by chemical reaction, the permeability and selectivity of liquid membranes are enhanced as compared to just physical transport. Because of very high permselectivity of facilitated transport membrane in comparison to conventional polymeric membranes on one hand and relatively very low energy consumption with respect to other conventional processes on the other hand, facilitated transport membranes have attracted the attention of many industries and researchers (Schultz et al, 1974;Saha et al, 1977;Niiya and Noble, 1985;Sengupta and Sirkar, 1986;Way et al, 1987;Way and Noble, 1989;Kreulen et al, 1993;flux without carrier or purely molecular diffusive. Many numerical and approximate solutions have been carried out in order to predict the facilitation factor for the transport of a single component facilitated transport in liquid membranes (Ward, 1970;Smith and Quinn, 1979;Kemena et al, 1983;Noble et al, 1986;Basaran et al, 1989;Guha et al, 1990;Dindi et al, 1992;Jemaa and Noble, 1992;Davis and Sandall, 1993;Teramoto, 1994Teramoto, , 1995Teramoto et al, 1996Teramoto et al, , 1997Al-Marzoughi et al, 2002;Morales-Cabrera et al, 2005).…”