Pervaporation Separation of Tetrahydrofuran/Water Azeotropic Mixtures using Phosphorylated Blend Membranes

Abstract

In this study, we developed novel phosphoric acid crosslinked blend membranes for the pervaporation separation of tetrahydrofu-
ran/water mixtures. Sodium alginate and chitosan blend membranes were prepared by solution casting and solvent evaporation technique. These blend membranes were crosslinked with phosphoric acid in isopropanol/water baths and used for pervaporation separation of feed mixtures ranging from 6 to 43 wt.% water in tetrahydrofuran (THF)/water mixtures at 30 °C. Crosslinking was confirmed by Fourier transform infrared (FTIR) and Ion Exchange Capacity (IEC) study. Thermal stability and crystallinity of the membranes were determined from thermogravimetric analysis (TGA) and X-ray diffraction (XRD) studies respectively. The surface morphology of the membranes was observed using Scanning electron microscopy (SEM). Sorption studies were carried out to evaluate the extent of interaction and degree of swelling of the membranes in THF, water and binary mixtures. The effect of experimental parameters such as feed composition, membrane thickness, and permeate pressure on separation performance of the phosphorylated membranes were determined. These membranes were found to have good potential for breaking the azeotrope of 94 wt.% THF with a selectivity of 459 and normalized flux of 0.25 kg m⁻² h⁻¹ 10 µm. The membrane performance exhibited a reduction in selectivity and an improvement in flux with increasing feed water compositions. Selectivity improved and flux decreased with increasing membrane thickness. Both flux and selectivity decreased with increasing permeate pressure.