The influence of a lithium chloride (LiCl) additive on poly(ether sulfone) (PES) membranes was investigated. A microwave technique was used to prepare membrane dope solutions, and two different types of solvent systems were used: single-solvent (SS) and double-solvent (DS) systems. In the SS system, PES was dissolved in N,N-dimethylformamide (DMF), and In the DS system, PES was dissolved in DMF and acetone. In the DS system, the control ratio of DMF to acetone was kept at 3.47, and the concentration of LiCl in both solvent systems was varied from 1 to 4 wt %. We observed that the microwave technique was able to dissolve the polymer rapidly, in less than 1 h. The performance of the PES membrane was evaluated in terms of poly(ethylene glycol) separation and molecular weight cutoff (MWCO). The results reveal that the presence of LiCl improved both the flux and rejection rates, and its concentration was best kept at 3 wt % for the tested conditions. In addition, we found that the mean pore size of the membranes produced from the DS system was smaller and the MWCO was lower as compared to the SS system.

In this article a modified polydimethylsiloxane (PDMS) blended polystyrene (PS) interpenetrating polymer network (IPN) membranes supported by Teflon (polytetrafluoroethylene) ultrafiltration membrane were prepared for the separation of ethanol in water by pervaporation application. The relationship between the surface characteristics of the surface-modified PDMS membranes and their permselectivity for aqueous ethanol solutions by pervaporation are discussed. The IPN supported membranes were prepared by sequential IPN technique. The IPN supported membrane were tested for the separation performance on 10 wt % ethanol in water and were characterized by evaluating their mechanical properties, swelling behavior, density, and degree of crosslinking. The results indicated that separation performance, mechanical properties, density, and the percentage of swelling of IPN membranes were influenced by degree of crosslink density. Depending on the feed temperature, the supported membranes had separation factors between 2.03 and 6.00 and permeation rates between 81.66 and 144.03 g m À2 h À1 . For the azeotropic water-ethanol mixture (10 wt % ethanol), the supported membrane had at 30 C a separation factor of 6.00 and a permeation rate of 85 g m À2 h À1 . Compared to the PDMS supported membranes, the PDMS/PS IPN supported blend membrane ones had a higher selectivity but a somewhat lower permeability.

No abstract

In this work, a series of pervaporation blend membranes with polydimethylsiloxane (PDMS)/polystyrene (PS) were prepared by using the sequential interpenetrating polymer network (IPNs) technique with various amount of PS (10-70 wt.%). The blend IPN membranes were supported by Teflon (polytetrafluoroethylene) ultrafiltration membrane. Effect of PS contents in PDMS IPNs on crosslinked density, molecular weight, network-chain segment concentration, water swelling properties, and tensile properties were investigated. Results revealed that the degree of crosslink density and tensile strength of the PDMS IPNs blend membrane depending on wt.% of PS added and scan electron microscope image confirmed that the PDMS/PSt IPN membranes have continuous microphase structures. The synthesized IPNs blend membrane was used for ethanol recovery from aqueous solution by pervaporation, and exhibited enhanced separation performance compared with PDMS membranes. The maximum separation factor of IPNs blend membrane were obtained at 50 C, and the total flux increased exponentially along with the increase of temperature. The PDMS/PS membrane synthesized by 50 wt.% PS gave the best pervaporation performance with a selectivity (a) of 7.6, permeation rate of 214 g/m 2 h with a 10 wt.% ethanol (EtOH) concentration at 60 C.