Concentration of aqueous dimethyl sulfoxide solutions through a chitosan membrane by permeation with a temperature difference

Abstract

Permeation and separation characteristics of aqueous dimethyl sulfoxide solutions through a chitosan membrane were studied by pervaporation and evapomeation. The chitosan membrane predominantly permeated water from aqueous dimethyl sulfoxide solutions in both methods. Permeation rates in evapomeation were smaller than those in pervaporation but separation factors in the former were greater than those in the latter. In temperature-difference controlled evapomeation, when the feed temperature of an aqueous dimethyl sulfoxide solution was kept constant and the temperature of the chitosan membrane surroundings was changed, both permeation rate and permselectivity for water increased with decreasing temperature of the membrane surroundings. The results are discussed from a viewpoint of the physicochemical properties of the membrane and permeant; mechanisms for permeation and separation of aqueous dimethyl sulfoxide solutions through a chitosan membrane by a few permeation methods are discussed.