Hydrophilically surface-modified and crosslinked polybenzimidazole membranes for pervaporation dehydration on tetrahydrofuran aqueous solutions

Abstract

Chemical modification has been carried out on polybenzimidazole (PBI) membranes for pervaporation dehydration on tetrahydrofuran (THF)/water mixtures. The PBI membrane crosslinked with 30wt% of a polybenzoxazine (CR-PBI-30) shows good stability and high separation performance for pervaporation dehydration on the THF aqueous solutions in a wide range of concentrations above 50wt%. Incorporation of poly(styrene sulfonic acid) (PSSA) chains to CR-PBI-30 membrane surface increases the surface hydrophilicity and water dissolution/absorption of the resulting membrane (CR-PBI-30-PSSA), so as to increase its water permeability without sacrificing membrane selectivity. The CR-PBI-30-PSSA membrane shows extremely high separation factors (the water concentrations at the permeate side (Cw)>99.99wt%) and moderate permeation fluxes (about 180gh−1m−2) for pervaporation dehydration on the THF aqueous solutions in concentrations above 80wt%. The membrane also shows a Cw>97.5wt% and a water flux of 220gh−1m−2 for a 70wt% THF aqueous solution. This work demonstrates an effective approach to prepare membranes for pervaporation dehydration on aqueous solutions of high polar solvents, especially for the feed solutions possessing high water contents.