Hydrazine hydrate is now produced worldwide by an ecofriendly process using ammonia and hydrogen peroxide as reactants, with methylethylketone (MEK) and acetamide being other active ingredients. Ketazine is an intermediate product during the formation of which, phase separation occurs between an upper organic layer enriched in ketazine and lower aqueous phase containing substantial amounts of acetamide (30 wt.%) and methylethylketone (5%) which have to be recycled in the form of a concentrated solution after partial removal of water (60%). The membrane based pervaporation (PV) technique has been successfully applied using the chemically compatible and highly hydrophilic chitosan membrane to dehydrate the highly alkaline aqueous layer. The effect of operating parameters such as feed composition and barrier thickness on membrane performance with respect to acetamide separation and water flux has been evaluated. High degree of acetamide separation was achieved along with reasonably good water flux and MEK separation. (C) 2003 Elsevier Science B.V. All rights reserved.