Study of pervaporation for dehydration of caprolactam through blend NaAlg–poly(vinyl pyrrolidone) membranes on PAN supports

Abstract

To improve or develop a new caprolactam dehydration process, pervaporation (PV) separation of caprolactam–water solutions was investigated using a composite membrane consisting of a selective sodium alginate (NaAlg)–poly(vinyl pyrrolidone) (PVP) blend membrane as top layer and a polyacrylonitrile (PAN) ultrafiltration (UF) membrane as substrate. The selective layer was physically blended and crosslinked with glutaraldehyde. The membranes were characterized by SEM, FTIR, XRD, and contact angle measurements. The effect of PVP content in the blend membranes on the pervaporation performance was investigated. The flux was increased by the addition of PVP and the separation factor was also increased when the PVP content was in the range of 0–20 wt.%. The blend membrane containing 20 wt.% PVP exhibited excellent PV properties with a flux of 1634.4 g/(m 2 h) and separation factor of 1610.6 at 323 K, for 50 wt.% caprolactam. Besides, operating temperature and feed composition on pervaporation performances were investigated. The results showed that the membranes permeation flux increased with increasing feed temperature and the water concentration, while separation factor decreased. The normalized permeation fluxes in terms of water permeance, caprolactam permeance and selectivity were also introduced to evaluate the membranes performance. The evaluated results revealed that the separation performances of NaAlg–PVP composite membranes were strongly related to their intrinsic hydrophilic/hydrophobic nature as well as the operating parameters.