Synthesis, characterization and application of disodium tetraborate cross-linked polyvinyl alcohol membranes for pervaporation dehydration of ethylene glycol

Abstract

Dehydration of ethylene glycol-water mixture was carried out in a laboratory pervaporation unit using a flat sheet membrane test cell. Polyvinyl alcohol-polyether sulfone (PVA-PES) composite membranes were synthesized and cross linked with two different concentrations, viz 0.2 and 0.5% of disodium tetraborate (borax). The derived membranes were extensively characterized for their morphology, intermolecular interactions, thermo-mechanical stability, and physicochemical properties using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and water uptake studies. The membrane performance was evaluated in terms of pervaporation flux, separation factor, selectivity, permeability and solute diffusion coefficients of EG-water mixture at varying feed flow rate. Both in terms of flux and separation factor PVA-PES-0.2% borax composite membrane was found superior to PVA-PES-0.5% borax crosslinked and its uncrosslinked counterpart. Cross-linking the composite with borax produced a membrane with lower crystallinity and a smaller swelling degree, but having improved thermostability and mechanical properties.