Nanocomposite membranes based on sodium alginate/poly(ε-caprolactone)/graphene oxide for methanol, ethanol and isopropanol dehydration via pervaporation

Abstract

Novel biodegradable nanocomposite membranes were prepared by incorporating different concentrations (2, 4 and 6 wt%) of graphene oxide (GO) as a nanoadditive into a blend of sodium alginate/poly(e-caprolactone) at ratio of 3:1 (SA:PCL) on the basis of solution-casting method and were then used for dehydration of a series of alcohols (methanol, ethanol and isopropanol) through pervaporation. The effects of feed composition, GO content and various alcohols on pervaporation performance were investigated. In addition, the swelling behaviors of SA/PCL/GO nanocomposite membranes were measured. All membranes were water selective, and the permeation rate increased with raising the GO content. The presence of GO having the functional groups increased the hydrophilicity of the SA/PCL blend polymer matrix, which resulted in the formation of a higher flux to water molecules. The best separation performance was achieved for the SA/PCL/GO-6 nanocomposite membrane containing 6 wt% GO with isopropanol–water feed at 30 °C. An enhancement in water concentration from 20 to 80 wt% increased the flux values from 506 to 779 g/m2 h. Likewise, an increase in feed water composition in the case of ethanol–water and methanol–water mixtures increased the flux values from 461 to 757 g/m2 h and from 298 to 569 g/m2 h, respectively. However, the separation factor of water for all membranes decreased with the increase in feed concentration. Pervaporation dehydration of aqueous isopropanol mixtures also proceeded easier than that of aqueous ethanol and methanol mixtures due to the larger molecular size of isopropanol. High dehydration performance of alcohol–water mixtures demonstrated the utility of these membranes for use in solvent dehydration application with higher efficiency.