Separation or organic/organic mixtures using pervaporation process has become a prime alternative and is extensively studied particularly in the chemical and petrochemical industries due to the process versatility. One of the classic example of its application is the separation of methanol (MeOH) from methyl tert-butyl ether (MTBE) in the production of octane enhancers for fuel blend, which has already been commercialized using cellulose acetate by Air Products [1, 2]. Since then, efforts have been devoted to producing the optimal membrane material for pervaporation separation of alcohol/ether mixtures [1, 2, 3]. In the similar attempt conducted by Kim et al., , pervaporative separation of this azeotropic mixtures showed an excellent selectivity and enhanced permeability with the incorporation of sodium alginate (SA) and chitosan (CS) to form polyion complex (PIC) membranes.
SA is an anion electrolyte polysaccharide extracted from seaweeds . SA is one of the commonly used green polymers as membrane materials. It is commonly used as a thickener, immobilization agent, gelling agent and films and coatings production . It is reported that the alginates contribute approximately 4.4 billion dollar in the global market of hydrocolloids and polysaccharides . On the other hand, CS is a typical polar material with unique properties such as biocompatible, biodegradable and non-toxic, and has successfully been used as membrane material .
This studies aimed at investigating factors affecting the pervaporation performance of prepared PIC membranes at different SA loading, MTBE concentration in feed and feed temperature. SA and CS were blended at different SA concentrations and PIC composite membranes were prepared through solution casting method. Both of the polymers were chosen in this studies due to their abundant availability, biodegradable, hydrophilicity and good membrane forming properties.
2.1 Membrane preparation.
Porous support for composite membranes was prepared from polysulfone by phase inversion method. 0.5-2.0 wt% of SA solutions was prepared by dissolving SA in 10 wt% aqueous acetic acid. CS concentration was fixed at 2.0 wt% and dissolved in 1 wt% acetic acid. Blends of CS and SA were casted onto the porous support to form composite membranes and air dried.
2.2 Membrane characterization
2.2.1 SEM analysis.
The morphology of the composite membranes were determined by using Phillips XL -40 Scanning Electron Microscope (SEM) at 10 kV accelerating voltage. The membranes were sputter-coated with gold before analysis.
2.2.2 Swelling Experiments.
The pre-weighed composite membranes were immersed in a liquid sorbate of known composition of MTBE/MeOH in a closed bottle at room temperature for 24 hours for an equilibrium swelling. The swollen composite membranes were weighed after excess liquid was blotted with filter paper. The amount of sorbed liquid in the composite membranes was expressed...