Permeation of solutes in water‐swollen poly(vinyl alcohol‐co‐itaconic acid) membranes

Partition and permeability coefficients of urea, NaCl, and saccharose in water‐swollen poly(vinyl alcohol‐co‐itaconic acid) membranes with various water contents (0.25 ⩽ H ⩽ 0.86) were measured. Partition coefficients and permeability ratios in freezing and nonfreezing water were estimated based on a parallel permeation model. It was suggested that at 25°C the permeation of saccharose in the nonfreezing water was nearly zero due to its negligible partition coefficient, while NaCl and urea were found to be able to permeate even the nonfreezing water. The activation energies of diffusion for three solutes were found to increase with the decrease of water content of the membranes. Since the fraction of nonfreezing water increased with the decrease of water content of the membranes, it is assumed that the increased activation energy of diffusion is due to the fact that the diffusion in nonfreezing water needs higher activation energy than in the pure bulk water.