Synthesis of polymer nanoparticles based highly selective membranes by mini-emulsion polymerization for dehydration of 1,4 dioxane and recovery of ethanol from water by pervaporation

Inorganic metal oxide or metal nanoparticles and organic graphene or carbon nanotube significantly improves the separation characteristics of polymer membranes. The high cost and compatibility issue of these nanoparticles may be countered by using low cost polymer nanoparticles (PNPs). Accordingly, several chitosan (CS) coated polyacrylonitrile (PAN) nanoparticles (CSPAN) were prepared by mini emulsion polymerization of acrylonitrile in the presence of chitosan as co-stabilizer. These CSPAN polymer nanoparticles were incorporated into polyvinyl alcohol (PVA). The filled PVA membrane was then crosslinked with maleic acid. The unfilled and filled PVA membranes were used for sorption and pervaporation of 1, 4-dioxane. Similarly, unfilled and CSPAN filled general purpose polystyrene (GPPS) membranes were used for recovery of ethanol from water. The structure, size, crystallinity, stability and morphologies of the PNPs and PNPs filled PVA and GPPS membranes were characterized with FTIR, NMR, SEM, TEM, EDAX and mechanical properties. The filled PVA18/GPPS3 membranes prepared with 18/3 wt% of CSPANs(of total PVA/GPPS wt.) containing 4.2/2.4 wt% of CS in CSPAN in PVA18/GPPS3 showed the best results for flux and selectivity (165.2/269.6 kg/m(2)h and 40.1/29.6 for PVA18/GPPS3) for azeotropic dioxane-water mixture (81.6 wt% dioxane) and 10 wt% ethanol in water. PVA18 and GPPS3 filled membranes were further used at varied feed concentrations of the organics in water. Both sorption and permeation were analyzed in terms of solvent-solvent and solvent-membrane interaction and solvent coupling. The hydrophilic filled PVA18 membranes showed high flux and water selectivity while the organo-philic filled GPPS3 membranes showed high flux and ethanol selectivity.

Automated summary

The addition of polymer nanoparticles significantly enhances the separation characteristics of polymer membranes for various applications, providing improved flux and selectivity. The use of low cost chitosan-coated polyacrylonitrile nanoparticles presents a promising alternative to expensive inorganic nanoparticles for membrane modification.