Sodium alginate-magnesium aluminum silicate mixed matrix membranes for pervaporation separation of water-isopropanol mixtures

摘要

Sodium alginate(NaAlg)is a well-known carbohydrate polymer occurring in natural sources.In this study,mixed matrix membranes of NaAlg filled with sub-micron size magnesium aluminum silicate(MAS)particles have been prepared by incorporating different amounts(5,10 and 15 wt.%)of MAS into NaAlg by solution casting and crosslinked with glutaraldehyde.The membranes prepared have been tested for pervaporation(PV)separation of water-isopropanol mixtures at 30°C.Membranes were characterized by Fourier transform infrared spectroscopy(FTIR)and scanning electron microscopy(SEM)to confirm the chemical interactions and homogeneity of the mixed matrix membranes.PV separation characteristics of the crosslinked NaAlg-MAS membranes have been studied by varying the feed water compositions and temperature.It was found that NaAlg membrane filled with 15 wt.% MAS gave the highest selectivity of 17,991 when tested for 10 wt.% of water containing feed mixture.Comparatively,a lower selectivity of 653 was observed for plain crosslinked NaAlg membrane for 10 wt.% water containing feed mixture;selectivity was further decreased with increasing water concentration of the feed mixture up to 50 wt.%.Water flux for the plain NaAlg membrane increased from 0.062 to 0.177 kg/m2h for the feed compositions ranging from 10 to 50 wt.% water;however at these compositions,flux values of NaAlg filled with 15 wt.% of MAS increased from 0.056 to 0.174 kg/m2 h,suggesting no significant improvement.The observed water flux is lower for the mixed matrix membranes,but higher for the plain NaAlg membrane;nevertheless,selectivity is higher for NaAlg-MAS mixed matrix membranes than observed for the plain NaAlg membrane.Similar trends have been observed at 40 and 50°C for the feed water compositions of 10-30 wt.%.The PV performance has been studied in terms of flux(J),selectivity(alpha),pervaporation separation index(PSI)and enrichment factor(beta).Permeation flux followed the Arrhenius trend over the investigated temperature range.