Exploration of nanocomposite membranes composed of phosphotungstic acid in sodium alginate for separation of aqueous–organic mixtures by pervaporation

• Phosphotungstic acid used in sodium alginate to develop nanocomposite membranes.
• Membrane characterization was done by UTM, DSC, UTM, AFM and XRD.
• PV separation of water–isopropanol and water–ethanol mixtures was performed.
• Improvement in separation performance observed for nanocomposite membranes.

Phosphotungstic acid (PTA) in unmodified and modified form (by ammonium carbonate) was incorporated as filler nanoparticles in different compositions (3%, 5%, 7% and 10%) in sodium alginate (NaAlg) to develop nanocomposite membranes (NCMs) by solution casting method and cross-linked with glutaraldehyde. The performance of these NCMs has been tested over that of pristine NaAlg membrane for dehydration of isopropanol and ethanol via the pervaporation (PV) technique. Membranes were characterized by a variety of techniques. The PV performance was investigated over the feed water composition of 10–30 wt.% and temperature interval of 30–60 °C. Improvement in separation performance was observed for the modified membranes than the unmodified membranes, suggesting the importance of chemical modification of PTA nanoparticles to avoid the leaching problem. The NaAlg membrane containing 10 wt.% modified PTA showed the highest PV performance, clearly indicating the effect of adding modified PTA.