Preparation of PFSA/PSf hollow fiber composite membranes with recovered PFSA for the pervaporation separation of EtOH/H2O

Abstract

Perfluorosulfonic acid/Polysulfone(PFSA/PSf) hollow fiber composite membranes have been prepared by dip-coating method using PSf ultrafiltration (UF) membrane as substrate with recovered PFSA. The composite membranes were applied to the pervaporation separation of 95% ethanol (EtOH)/H 2 O mixture. SEM images show that the thickness of the PFSA skin layer of the composite membranes is about 2 μm, much thinner than those of other PFSA composite membranes revealed in the literatures. Effects of annealing temperature, coating solution concentration and counter-ions of PFSA on the pervaporation performances of the composite membranes were investigated. The total flux decreases and separation factor increases with the increase of annealing temperature. The highest permeation flux of 3230 g m −2 h −1 and a separation factor of 5.4 is obtained for the composite membrane annealed at 80°C. The lowest permeation flux of 396 g m −2 h −1 and a separation factor of 27.7 is obtained for the composite membrane annealed at 160°C. The permeation performances of the PFSA/PSf composite membrane are evidently influenced by the counter-ions of PFSA. The flux sequence of the PFSA/PSf composite membranes with different counter-ions is H + >Li + >Ca 2+ >Mg 2+ >Na + >K + >Ba 2+ >Fe 3+ >Al 3+ , and the separation factor sequence is H + <Li + <Al 3+ <Na + <Mg 2+ <Ca 2+ <K + <Ba 2+ <Fe 3+ . The apparent activation energy ΔE app values of the composite membranes with different counter-ions were calculated by Arrhenius law. The sequence of ΔE app values for the membranes with monovalent counter-ions is Li + >Na + >K + . There are very little variations of ΔE app values between the composite membranes with three divalent counter-ions (Mg 2+ , Ca 2+ and Ba 2+ ), and the ΔE app values of the composite membranes with two trivalent counter-ions (Fe 3+ and Al 3+ ) are relatively high. pervaporation, hollow fiber composite membrane, perfluorslulfonic acid (PFSA), ethanol (EtOH)/H 2 O mixture

Pervaporation separation of dimethyl carbonate/methanol mixtures with regenerated perfluoro‐ion‐exchange membranes in chlor‐alkali industry

“…With the increase in size of the counter ion, the free volume of ion cluster decreases and causes the decrease of the permeation flux. The similar tendencies of the separation selectivity and permeation flux with counter ions were also found in the pervaporation separation of alcohol/H 2 O mixtures 10–12…”

“…PFSA is the main ingredient of PFIEM. Besides its applications in chlor‐alkali cell, pervaporation process is another important application field for PFSA membrane 6–16. Several reports revealed the dehydration of inorganic and organic acid6–9 by pervaporation process using PFSA (nafion) membrane because it has high chemical stability and preferential permeation for water.…”

“…Several reports revealed the dehydration of inorganic and organic acid6–9 by pervaporation process using PFSA (nafion) membrane because it has high chemical stability and preferential permeation for water. Furthermore, PFSA was also employed to the dehydration of small molecular alcohol by pervaporation process or blended with other materials 10–13. PFSA has also been found to be highly selective for separating methanol (MeOH) from organic solutions in some separation process 14–16.…”