Novel sodium alginate composite membranes prepared by incorporating cobalt(III) complex particles used in pervaporation separation of water–acetic acid mixtures at different temperatures

The present paper is our continuing effort to develop a new type of sodium alginate (NaAlg) composite membrane by incorporating cobalt(III)(3-acetylpyridine-o-aminobenzoylhydrazone) (Co-APABZ) complex as filler particles in different ratios. Membranes were prepared by solution casting followed by solvent evaporation and crosslinked with glutaraldehyde. Pervaporation (PV) performance of the prepared composite membranes was assessed in terms of flux and selectivity and these data were compared with the pristine NaAlg membrane in PV dehydration of water–acetic acid mixtures. Pristine Co-APABZ particles in crystalline form were prepared and characterized by the solid state X-ray diffraction (XRD) technique, while the NaAlg/Co(III)composite membranes were characterized by thermogravimetry (TGA) and dynamic mechanical thermal analyzer (DMTA). X-ray crystal structure of Co-APABZ has shown that the complex formed was crystalline in nature with six lattice water molecules, which are interconnected by hydrogen bonds linking together to form cyclic hexamers that are analogous to cyclohexane, creating water channels for an easy transport of water molecules. TGA indicated no changes in thermal stability of the membranes due to the presence of Co-APABZ in the NaAlg matrix. DMTA confirmed NaAlg crosslinking with glutaraldehyde. Effects of Co-APABZ content, membrane thickness, temperature and feed water compositions on membrane performance were investigated to find an optimum PV performance of the membranes developed. NaAlg composite membranes in the presence of Co-APABZ particles preferentially absorbed water molecules to facilitate diffusion of water through the membranes and thus enhance the selectivity to water. However, the amount of Co-APABZ present in the NaAlg matrix and the degree of membrane swelling has an effect on membrane performance. Selectivity of 174 for water with a flux of 0.123 kg/m2 h was obtained for 5 wt.% Co-APABZ containing NaAlg matrix, when tested for the feed mixture containing 10 wt % water. The present results are superior to the previously published data based on NaAlg membranes.