Pervaporation separation using sodium alginate and its modified membranes - A review

Sodium alginate (NaAlg) and its modified forms have been widely used as membranes in pervaporation (PV) separation of aqueous-organic solutions because of the hydrophilic nature and versatility to modify/tune their structures to achieve the desired separation. A survey of the literature indicates that in recent years, NaAlg-based membranes have been reported to perform outstanding separation characteristics in dehydrating the aqueous-organic mixtures. In view of the availability of extensive data on the PV performance of NaAlg and its modified membranes, particularly in separating water-organic mixtures, we thought of compiling the available literature PV data on NaAlg membranes with an aim to assess their performances over other membranes. The present review addresses the application of PV technique using NaAlg membranes for dehydration of organic liquids of different kinds. Literature data on NaAlg-based membranes such as grafted NaAlg, blends of NaAlg, hybrid composites of NaAlg and mixed matrix membranes of NaAlg are widely scattered. Hence, this review compiles and critically evaluates such data. Literature data on modified NaAlg including blends, grafts, filled matrices, composites, etc., are discussed with respect to a variety of aqueous-organic mixtures. Factors such as effect of feed composition, membrane swelling, flux and selectivity are assessed with reference to solvents like ethanol, isopropanol, tetra-hydrofuran, 1,4-dioxane, acetic acid, and acetonitrile.