Pervaporation separation of ethanol–water mixtures through sodium alginate membranes

A sodium alginate (SA) dense membrane was prepared by the casting and drying of sodium alginate solutions on an acrylic plate, followed by crosslinked with phosphoric acid for the separation of ethanol–water mixtures at 30°C by the pervaporation method. The membrane containing 3 wt.% of sodium alginate shows the highest separation selectivity of 2182 with a substantial flux of 0.035 kg m–2 h–1. Permeation flux increased with an increase in weight percentage of water in the feed mixture, but separation selectivity decreased. The effect of experimental factors, such as the concentration of the feed solutions, membrane thickness and the operating permeate pressure on SA membrane performance were evaluated. The membranes were also subjected to sorption studies to evaluate the extent of interaction and degree of swelling in pure as well as binary feed mixtures. Further, ion exchange capacity (IEC) studies were carried out for all the crosslinked and uncrosslinked membranes to determine the total number of interacting groups present in the membranes.