Transport phenomena of chitosan membrane in pervaporation of water-ethanol mixture

The pervaporation transport process of H2O-EtOH solution was studied on a chitosan membrane and on a H2SO4 crosslinked chitosan membrane. The influence of concentration, temperature, and crosslinking was also studied. The dependence of permeation fluxes on feed concentration showed strong coupling effects existed in the permeation process. That the thermodynamic swelling-distribution relationship changed with the feed concentration also showed that a strong coupling effect existed in the thermodynamic swelling process. The permeation fluxes and thermodynamic swelling processes showed analogous relationships versus the concentration in the feed. The high swelling ratio and the high selectivity of the membrane in the thermodynamic swelling distribution process was the basis of high flux and high permselectivity of pervaporation. With an increase of temperature, the permeation fluxes increased quickly, but the swelling ratio of water and EtOH in the membrane scarcely changed. This showed that an increase of temperature promoted the diffusion process but had little influence on permselectivity. The permselectivity of pervaporation depended strongly on the thermodynamic swelling process.