EFFECT OF ORGANIC-SOLVENTS AS GELATING AGENTS ON PERFORMANCE OF CHITOSAN MEMBRANES FOR ULTRAFILTRATION

Chitosan membranes for ultrafiltration were prepared by the phase inversion method with an aqueous solution of acetic acid as the solvent. In order to improve the membrane performance, various organic solvents were employed as the gelating agents. Their effects on the membrane formability and performance were investigated from the viewpoint of their behaviors in gelating processes. The gelating agents showing good membrane formability could be grouped into two groups depending on the heat change obtained by mixing chitosan solution and gelating agent. The agents showing endothermic change in the case of mixing formed tight membranes and the agents showing exothermic change formed loose membranes. Further, the agents having the higher fluidity formed the looser membranes among the exothermic gelating agents. These results suggest that the affinity for water of the gelating agent as well as the relative exchange rates between water in chitosan-rich phase and the gelating agent play important roles as determinants for the membrane performance.