Pervaporative recovery of N-methyl-2-pyrrolidone from dilute aqueous solution by using polyurethaneurea membranes

Hydroxyterminated polybutadiene (HTPB)-based polyurethaneurea membranes were synthesized and used for pervaporative recovery of N-methyl-2-pyrrolidone (NMP) from dilute aqueous solution. The sorption of NMP in cross-linked polyurethaneurea membranes was found to vary with feed NMP concentration and soft segment content of the membrane. A linear sorption isotherm was observed. The effects of membrane soft segment content, feed NMP concentration, operating temperature and membrane thickness on the pervaporation performance of the synthesized polyurethaneurea membranes were studied. With decrease in soft segment content of the membrane, the permeation flux was observed to decrease slightly but the separation factor increased to some extent. With the increase in concentration of NMP in feed solution, permeation flux was found to improve significantly. Both the permeation flux and the separation factor for NMP were found to increase with increase in operating temperature. The activation energy for pervaporation of both NMP and water calculated from Arrhenius plot indicated that an increase in hard segment content imposed a restriction to the transport of the components through the membrane.