Sulfonated polysulfone supported high performance thin film composite membranes for forward osmosis

Abstract

Abstract Sulfonated polymers have shown great promise as a material for membranes in water purification. Their hydrophilic nature combined with impressive chemical stability has yielded unique membranes with desalination capacity combined with chlorine tolerance. In this work, we explore the use of these polymers in support materials for thin film composite (TFC) membranes for forward osmosis (FO). Our reasoning behind their use lies in their intrinsic hydrophilicity, which promotes wetting and mass transfer in this support layer. We combine the use of this supporting material with different polyester (PET) nonwoven backings in order to better understand how backing choice and membrane midlayer material choice interrelate. By varying the degree of sulfonation in the support midlayer, along with selecting backing nonwovens with appropriate characteristics, our best membranes exhibited water flux of about 70 L m−2 h−1 using 1 M sodium chloride draw solution against deionized water in PRO mode. The use of the PET in these membrane imparted impressive mechanical properties while still keeping the structural parameter low (as low as 277 μm). This is the lowest structural parameter of the fabric backed TFC membranes reported in the open literature. These results suggest that the combination of sulfonated polymer midlayers with appropriate PET nonwovens could serve to inform next generation membrane designs for forward and pressure retarded osmosis.