Diffusive permeability of ionic solutes in charged chitosan membrane

Abstract

ABSTRACT:The permeabilities of three kinds of solutes with similar sizes such as anionic benzenesulfonic acid, neutral styrene glycol, and cationic theophylline in the chitosan membrane were investigated. The chitosan membrane becomes cationic below its pKa value. Benzenesulfonic acid showed the highest permeability, whereas theophylline showed the lowest, although these solutes have almost the same size. This can be explained by the electrostatic attraction or repulsion between the solute and the membrane instead of the size exclusion effect. The permeabilities of benzenesulfonic acid and theophylline increased and decreased, respectively, with the decrease of pH from 7.4 to 4.0 because of the increase of the charge density of the membrane. Thus, the selectivity of benzenesulfonic acid to theophylline increased and reached about 30 at pH 4.0, in contrast to the selectivity of nearly unity in poly(vinyl alcohol) (PVA) membrane. The partition coefficients for three solutes showed the similar tendencies to those in the permeabilities. Contrary to the results of the permeabilities, the partition coefficients increased with the increase of the degree of the crosslinking in the membrane. This is probably due to the increase of the electrostatic interaction between the solute and the membrane brought about by the smaller mesh size and also due to the increase of the bound water fraction in the membrane.

Studies on nanofiltration membrane formed by diisocyanate cross-linking of quaternized chitosan on poly(acrylonitrile) (PAN) support

“…[7,8]. At present, commercially available NF membranes are mainly neutral or negatively charged composite membranes [9,10].…”

Electrolyte diffusion in a chitosan membrane

“…At the beginning of the diffusion process the amount of salt retained in the membrane is zero, which is consistent with a stationary regime; for longer times, however, Fig 5 suggests that the membrane is continuously liberating electrolyte, without gaining any material. This could be related to the formation of a thin barrier of salt‐saturated membrane at the very surface of the film, which blocked the entrance of KCl in the membrane (decrease in permeability, due to saturation of chitosan membranes by electrolytes has already been reported in the literature19, 20). Another reason could be that, in this work, osmosis was not taken into account.…”

Preparation of thermoresponsive core–shell copolymer latex with potential use in drug targeting

“…Therefore, particles had more negative zeta potential when the weight ratio of MAA/MMA or the concentration of MAA and MMA increased. When the solution was changed to pH 4, the COOH group of MAA in the shell was very stable in the COOH form, the NH + 3 derived from NH 2 of chitosan (the pK a value of chitosan was reported to be 6.3 [31,32]) and the SO − 4 derived from the initiator (ammonium persulfate) combined to determine the zeta potential of the particles. Consequently, the zeta potential of particles was very small in the pH 4 buffer solution.…”