Pervaporation separation of methyl tert-butyl ether /methanol mixtures using polyion complex chitosan membranes

Abstract

The main objective of this research was to develop polyion complex composite (PIC) membranes consisting of chitosan/sodium alginate (SA) for the pervaporation separation of methyl tert-butyl ether (MTBE)/methanol mixtures. The PIC membranes were fabricated by casting homogeneous chitosan/SA solution onto polysulfone (PS) which was used as a porous support. The chitosan and sodium alginate solutions were prepared separately by using dilute acetic acid as the common solvent. The homogeneous chitosan/SA solution was prepared by mixing both the chitosan and SA solutions for 24 hours. The morphological structure of the membranes was studied using Scanning Electron Microscopy (SEM). The morphology study showed that the PIC membranes consisted of two layers. The top layer was dense which indicated that the two polymers were very homogenously intermixed and in the state of the polyion complex. The membranes were used for the separation of MTBE/methanol mixture via pervaporation. The separation performance of the chitosan/SA membrane was compared with that of composite chitosan membrane. The sodium alginate content incorporated in the PIC membrane enhanced the membrane performance in the pervaporation separation of MTBE/methanol mixtures. The overall pervaporation performances for the membranes were determined in term of pervaporation separation index (PSI). The PIC membranes showed higher PSI than that of the composite membrane especially at high feed MTBE concentrations. The optimum concentration of SA in membranes was found to be 1.5 wt. %. At this concentration of SA, the degree of swelling was 1.02 % with 42.5 wt. % MTBE sorbed in membrane while PSI increased from 946.9 g/m2.h (composite chitosan membrane) to 3211.8 g/m2.h. It was also found that a rise in operating temperature increased the permeation flux and separation factor.