Analytical and experimental studies of facilitated transport

Abstract

Facilitated transport is a process in which permeation through a liquid film is chemicall) augmented. Becauw of the scientific and engineering interest in this phenomenon, the purpose of this work was to carry out a detailed mothematical and experimental investigation of facilitated transport. The diffwential equations describing facilitated transport are presented, and a generally applieabk numerical solution recently developed by G. M. Roe for this type of boundary value problem is summarized. The experimental investigation consisted of measuring tho steady stote rate of transport of nitric oxide through thin films of ferrous chloride solution and of determiniag independently the values of the system parameters of which the nitric oxide flux was a function. The experimental results were accurately predicted by using the model developed by Roe. This is the first demonstration of a general quantitative understanding of facilitotod transport.Over the years there have been many attempts to develop semipermeable membranes for separation processes, and patents on potential processes date back more than a century. However, it is only in the past 10 yr. that membranes have been developed which make certain membrane separation processes within range of being economically and technically feasible. Although several polymers such as silicone rubber and cellulose acetate are useful membrane materials, in general polymeric materials are not desirable as semipermeable membranes, since most are relatively impermeable to all gases and liquids. Several years ago W. L. Robb (1) considered liquids as potential membrane materials, and based on this concept a highly effective immobilized liquid membrane for carbon dioxide removal from a life supporting environment was developed by Ward and Robb ( 2 ) . During this work it was found that it was possible to augment chemically the transport of carbon dioxide across the liquid film. This phenomenon, known as facilitated tramport, was first observed in 1959 by Scholander (3) and Wittenberg ( 4 ) in the steady state diffusion of oxygen across thin films of aqueous hemoglobin solutions.There is a continuing interest in facilitated transport in the life sciences, and, as already demonstrated, facilitated transport can have important practical application in improving the performance of liquid membranes for separation processes. There are a number of experimental and analytical studies of facilitated transport in the literature (2, 5 ) . However, these studies represent special cases in which simplifying assumptions could be made, making it popsible to describe the performance of these systems analytically. Because it was not previously available, the present investigation was undertaken to develop a general quantitative understanding of facilitated transport.Facilitated transport is a process whereby the permeation of a solute across a membrane is chemically augmented. The simplest type of facilitated transport system consists of a gas A and nonvolatile molecular or ionic species B and AB p...

Reactive barrier films

“…10, the case without reaction. This prediction of unaltered lag time is not always supported experimentally, perhaps because of unequal diffusion coefficients (Ward, 1970). Nonetheless, the reaction causes the barrier to be breached more quickly, which is the antithesis of what we want.…”

Coupled diffusion of butanol solubilized in aqueous sodium dodecylsulfate micelles

“…However, the diffusion cjf associating solutes is more frequently described by using pseudobinary transport equations (8,(21)(22)(23)(24)(25)(26)(27)(28)(29) Can. J. Chem.…”

Transport of copper(II) through supported liquid membrane containing LIX65N.

“…The diffusivity in a membrane with micro-pores is related to that in the bulk organic solvent by the following equation7} : Dm=sDb/t> (18) where r is the tortuosity of the membrane. Mackie and Meares15) have expressed the tortuosity as a function of the volume fraction of the polymer framework.…”