Permeability properties of gels and membranes derived from chitosan

A series of membranes was prepared by air-drying the thin layers of N-acyl- and N-arylidene-chitosan gels. Their flow rates of water and permeabilities of various compounds were examined. N-Acylchitosan membranes were stable in both dilute acid and alkali, but N-arylidene-chitosan membranes were unstable in dilute acid. N-Acetylchitosan membranes were stable in formic acid at room temperature for up to 7 hr. The flow rates of water through N-acetylchitosan membranes were 10.0--23.6 X 10(-3) ml/cm2min under a pressure of 3 kg/cm2, and were unchanged by the membrane thickness (12--60 micrometers). The increase of carbon numbers for N-acyl groups caused a slight decrease in the flow rates, and the flow rates were decreased by partial O-acetylation of N-acetylchitosan membranes. The flow rate of water through chitosan membranes (thickness 30--35 micrometers) was 7.1 X 10(-4) ml/cm2min, which was decreased by an increase in the membranes thickness. Low-molecular-weight compounds (MW less than 2900) passed through these membranes, but high molecular-weight compounds (MW greater than 13,000) did not pass through.