Flat-sheet composite membranes were developed by the traditional phase inversion technique using poly (vinyl alcohol) (PVA). PVA composite pervaporation (PV) membranes were prepared with crosslinked PVA selective layer and porous polyacrylonitrile (PAN) and polyether sulfone (PES) substrate layer material as supports for separating heat sensitivity substance epsilon-caprolactam (CPL) from CPL/water mixtures. Glutaraldehyde was used as crosslinking agent. The effect of the composition of glutaraldehyde on membrane stability and structure were investigated. The operating parameters, such as feed concentration and operating temperature, remarkably affected PV performance of the composite membranes. The composite membranes with PVA casted on PAN (PVA/PAN) showed superior PV performance than that casted on PES (PVA/PES). This study has also shown that the type of porous support plays an important role in the PV performance. As a result, this work has presented the information needed of the behavior of PV membranes for dehydration applications of industrial caprolactam. (c) 2006 Wiley Periodicals, Inc.