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In this study, membranes from chitosan with different molecular weights (175-230 kDa) and degree of deacetylation (92%-98%) were prepared and dehydration of a ethanol-water azeotropic mixture by pervaporation on membranes in the swollen and dry initial state was investigated. The influence of chitosan characteristics and the effect of the initial membrane state on separation properties are discussed. The structure of the obtained membranes changed during the drying process and affected the membrane transport parameters and time to membrane stabilisation. The impact of chitosan characteristics on the transport parameters depended on the initial membrane state. The chitosan molecular weight influenced ethanol transport, whereas the chitosan degree of deacetylation affected water transport. In addition, chitosan with the lowest molecular weight improved the separation properties of the membranes. [ABSTRACT FROM AUTHOR]