Interfacial State Change of Cellulose Triacetate Membrane by Adsorption of Polyelectrolyte

Study of the surface character as responsible for controlling interfacial forces at membrane–feed interface

The role of the interfacial forces was emphasized in interactive processes, involving membrane surface and penetrating molecules. The surface character controlling the dissolution process of some species (CO2, H2O, C3H6O2, C4H8O2, C5H10O2) was evaluated in relation to the supra-molecular chemistry of membranes based on 80PTMO/PA12. Infrared analyses combined with the estimation of the hydrophilic and hydrophobic domains of the membrane surface yielded useful information about the distribution, availability and accessibility of the polar moieties responsible for the penetrant sorption. At the interface, attractive Lewis acid/base interactions such as H-bonding directed the sorption of vapor species into the membranes, whereas quadrupolar CO2 participated in specific Lifshitz-van der Waals interactions with the modified polymers. In both the cases, the presence of additional polar moieties such as carbonyl, sulfonamide, and hydroxyl groups enhanced the affinity of the Pebax-based membranes for the penetrating species considered in this work. As a result, the quantification of the reactivity of a membrane surface for specific molecules may allow predictive models to be constructed and selective membranes to be designed.

An Application of Percolation Theory to the Electrolyte Penetration through Porous Water-Swollen Cellulose Triacetate Membrane

Permeability coefficients P of KCl through porous cellulose triacetate (CTA) membranes were measured as a function of the water volume fraction V(W) and diffusion coefficients D were determined using solubility parameters K and a membrane thickness d from the relationship of P = KD/d. D increased with an increase in V(W). D especially increases abruptly around V(W) = 0.5, which corresponds to 2% triethylene glycol (TEG) content. The percolation theory was applied to the experimental results under the conditions D(A) = D (V(W) = 1) = 1.8 x 10(-5) cm(2) s(-1), D(B) = D(V(W) = 0) = 1.8 x 10(-8) cm(2) s(-1), coordination number (Z) = 2.5, 3, 3.5, and 4, and packing fraction f = 1.0. A good fit was obtained at Z = 3.5 because the experimental and calculated results also shifted at the same V(W) below V(W) = 0.5. It is suggested that a phase inversion, that is, change of a discontinuous water phase to a continuous water phase, occurs around V(W) = 0.5. Above V(W) = 0.5, the experimental results agree well with the calculated line for Z = 3 or Z = 2.5 which means that the coordination numbers decrease with an increase in water content. It is thought that V(W) is overestimated because it is hard to completely wipe off the excess water quickly from the membrane surface. Z = 3.5 means that a pore can connect in 3.5 directions. Copyright 1999 Academic Press.

Preconcentration of quinolones by dialysis on-line coupled to high-performance liquid chromatography

The parameters influencing dialytic separation of ciprofloxacin (CF) fluoroquinolone were investigated. Dialysis with a porous cellulose acetate membrane was on-line coupled with HPLC and the analysis of dialysate was made by isocratic ion-pairing liquid chromatography using a reversed-phase analytical column and fluorescence detection. Optimisation of the experimental conditions for selective dialytic enrichment are described and explanations of some phenomena affecting dialysis efficiency discussed. By the use of a neutral donor (pH approximately 7) and acidic acceptor solution (pH < 4) a substantial enrichment of quinolones was achieved. Accumulation of CF in the acidic acceptor phase is based on the protonation of the analyte in the acceptor compartment. Continuous-flow of donor solution and a stagnant acceptor solution gave high dialysis efficiency in 5-15 min. Effects of interfering substances present in real samples on the variation of dialysis efficiency can be minimised by successive dialysis runs of the original and spiked samples.

Ion Transport across a Polyelectrolyte-Adsorbed Cellulose Triacetate Membrane in the Multicomponent Ionic Systems

The effects of polyelectrolyte adsorption by cellulose triacetate (CTA) membrane on ionic transport are investigated in two systems: the three-ionic-component system and the multicomponent-ionic system. In the three-ionic-component system, the permeabilities of two anions are affected by the competitive ion. Especially in the case of the albumin-adsorbed CTA membrane, there exists much greater specificity for the permeability of SO2-4 than in the case of the lysozyme-adsorbed membrane. On the other hand, in the case of the PAS-H(10L)(polydiallyldimethylammonium chloride)-adsorbed membrane, the permeability coefficient of HPO2-4 increases, though there exists the effect of a competitive ion. In a multicomponent-ionic system, the logarithmic permeability coefficient ratios (rP) of each ion in an adsorbed membrane to that in a nonadsorbed membrane decreased by PAS-H(10L) adsorption for all cations. The rP of bivalent cations decreased more than those of univalent cations because of the rejection from the positively charged adsorbed layer. On the other hand, the permeabilities slightly increase because of the attraction from the PAS-H(10L)-adsorbed layer when competitive anions exist among them. Furthermore, the increase in the HPO2-4 permeability is confirmed by PAS-H(10L)-adsorption on a CTA membrane for a case very similar to the actual anion multicomponent system. These are the most important results in the application for an approach to phosphate extraction from blood across an artificial kidney membrane. Copyright 1999 Academic Press.