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.
Highlights
Pervaporation is much touted as an efficient and environmentally benign separation process both as a standalone unit and a supplementary to the distillation
Formation of Polyvinyl alcohol-polyether sulfone (PVA-Poly ether sulfone (PES)) composite membranes is modulated by the addition of a cross-linking agent, borax in the present study, which leads to the formation of esters with hydroxyl groups on the polymer network.[18]
The polyvinyl alcohol (PVA) layers were successfully cross linked with two different concentrations e.g. 0.2% and 0.5% borax as cross linking agents 0.2% borax crosslinked PVA-PES composite was found better in terms of flux, permeability and separation factor
Summary
Pervaporation is much touted as an efficient and environmentally benign separation process both as a standalone unit and a supplementary to the distillation. For polyvinyl alcohol (PVA) based pervaporation membranes incorporation of an interfacial cross linking agent can counter the inherent swelling susceptibility of PVA to ensure that the contaminants in water can be retained, and minimize compaction under pressure while used in other pressure driven processes.[15] There is a challenge for any membrane to achieve high permeate flux but not at expense of its stability and mechanical properties. A growing body of literature in recent years has investigated the structural, mechanical, and thermal properties of different polymeric hydrogels, disodium tetraborate (borax) cross-linked polyvinyl alcohol composite membrane for pervaporative separation of EG-water solution has not been extensively focused so far to the best of our knowledge. Put to the fundamental aspects of PVA-PES composites doped with borax for dehydration of EG on a commercial scale
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