Effects of Ca2+ bridge cross-linking on structure and pervaporation of cellulose/alginate blend membranes

Blend membranes prepared by coagulating the mixture of 8 wt.% cellulose cuoxam and 8 wt.% aqueous sodium alginate solution were cross-linked by using Ca2+ bridge in 5 wt.% CaCl2 aqueous solution. Pervaporation separation parameter of ethanol–water mixtures through the blend membranes was measured by a pervaporation apparatus. The effects of Ca2+ cross-linking and operating temperature on the permeation flux and separation factor were investigated and discussed. The results from IR, DMA and X-ray diffraction indicated that the strong interaction between cellulose and alginate exists in the blend membranes. For the Ca2+ cross-linked blend membranes, which have relatively higher density and crystallinity, the permeation flux hardly changed, while the pore size measured from the flow rate method decreased. Moreover, the cellulose/alginate (8:2, by weight) blend membrane cross-linked with Ca2+, showed the higher pervaporation separation factor for 90% alcohol feed mixture at 60°C and the higher the permeation flux at lower temperature than that of uncross-linked membrane, owing to Ca2+ bridge. The mechanical properties of alginate membranes were significantly improved by introducing cellulose and Ca2+ bridge. Its tensile strength was 12 times higher than that of alginate membrane.