Mixed matrix membranes of sodium alginate and poly(vinyl alcohol) for pervaporation dehydration of isopropanol at different temperatures

Abstract

Mixed matrix membranes of sodium alginate (NaAlg) and poly(vinyl alcohol) (PVA) containing 5 and 10wt.% silicalite-1 particles were fabricated by solution casting method and the cured membranes were crosslinked with glutaraldehyde. These membranes were used in pervaporation (PV) dehydration of isopropanol at 30, 40, 50 and 60°C. Membrane morphology was studied by scanning electron microscopy and universal testing machine to assess their mechanical strengths. Swelling results of the pristine and mixed matrix membranes were correlated with their PV performances. Selectivities of the mixed matrix membranes of NaAlg were 11,241 and 17,991 with the fluxes of 0.039 and 0.027kg/m2h, respectively, for 5 and 10wt.% silicalite-1 loadings. Corresponding values for mixed matrix membranes of PVA were 1295 and 2241, and 0.084 and 0.069kg/m2h, respectively, for 10wt.% water-containing feed at 30°C. Pristine membranes of NaAlg and PVA exhibited lower selectivities of 653 and 77 with increased fluxes of 0.067 and 0.095kg/m2h, respectively. From the temperature dependence of flux and diffusivity data with 10wt.% water-containing feed, Arrhenius plots were constructed to compute heat of sorption, ΔHs values. Mixed matrix membranes of NaAlg were better than PVA mixed matrix membranes at all compositions (10–40wt.%) of water. Molecular dynamics (MD) simulation was employed to compute the interfacial interaction energies of NaAlg and PVA polymers with silicalite-1 filler; also sorption of liquid molecules was computed. Simulated diffusivities compared well with the experimental data. Thermodynamic treatment of sorption, diffusion and permeation processes was attempted based on the Flory–Huggins theory to explain the PV performances of the membranes.