Poly(ether-block-amide) membrane for pervaporative separation of pyridine present in low concentration in aqueous solution

Abstract

The present work attempts to recover pyridine from its dilute concentration of aqueous solution, a concern for industries, through pervaporation. Poly(ether-block-amide) (PEBA) thermoplastic elastomers (based on nylon-12 and poly tetra-methylene oxide homogeneous polymer) were utilized for making membrane. PEBA polymer is typically hydrophobic and it was observed that the membrane was preferentially permeable to pyridine. The membranes that were cast with PEBA were also characterized through SEM and XRD. To observe quantitative indication of the PEBA membrane affinity for pyridine–water mixture, the sorption experiments were performed over wide ranges of feed composition (from almost 0–40 wt% of pyridine in an aqueous solution) at 60 °C. Further, in order to compare sorption results, polysulfone (PSf) membrane was also utilized. Negligible sorption of water was observed with PEBA membrane, reflecting greater affinity for pyridine. Experimentations were performed to study influences of pyridine feed concentration (up to 8 wt%), feed temperature (40–80 °C) and downstream pressure (0.8–15 mbar) on flux and selectivity. It was observed that total as well as partial (pyridine) flux increased with increase in feed (pyridine) concentration. Further, water flux marginally increased (relatively constant) with increase in feed (pyridine) concentration, which may be considered due to coupling effects. Experiments were also conducted using PEBA membrane to study the effect of feed concentration on activation energy. Interestingly, it was observed that it is possible to carry out the operation at an elevated temperature in order to achieve high productivity. Using PEBA membrane, estimated value of permeability coefficient for pyridine was found to be greater than that for water. Results were further analyzed through permeation ratio θ in order to explain interactions between the polymer and the permeants.