A comparison of methanol permeability in Chitosan and Nafion 117 membranes at high to medium methanol concentrations

Chitosan membranes, cross-linked in sulphuric acid, were evaluated for methanol permeability at high to medium methanol concentrations and compared to the methanol permeability in Nafion 117 membranes. As a natural polymer, Chitosan is considered to be a cheap source of membrane material compared to Nafion. Methanol permeability through Chitosan membranes of medium molecular weight for methanol concentration of 12 mol/L at 20 °C was found to be (8.0 ± 0.5) × 10−7 cm2/s. This is almost three times lower than the permeability found for Nafion 117 of (2.3 ± 0.2) × 10−6 cm2/s at the same methanol concentration and temperature. An increased methanol concentration of 18.5 mol/L resulted in a decreased methanol permeability of (5.2 ± 0.6) × 10−7 cm2/s at 20 °C for Chitosan compared to increased methanol permeability of (2.7 ± 0.5) × 10−6 cm2/s at the same temperature for Nafion 117. An increased temperature of 50 °C at methanol concentration of 12 mol/L however resulted in an order of magnitude increase in methanol permeability ((4.1 ± 0.3) × 10−6 cm2/s) for Chitosan membrane, which is comparable to the increase in methanol permeability of (3.8 ± 0.8) × 10−6 cm2/s for Nafion 117 membrane.