Tubular composite PVA ceramic supported membrane for bio-ethanol production

Abstract

Thin polyvinyl alcohol (PVA) layers loaded with fumed silica were coated on porous ceramic supports. Scanning electron microscope (SEM) was used to characterize the ceramic-supported thin PVA active layers and the effects of coating gel PVA concentration on thickness and density of the active layers were investigated. Pervaporation (PV) dehydration of 90wt.% ethanol was performed at temperatures of 30, 45 and 60°C. The values of water flux (0.05–2.92kg/m2h) and selectivity (3–180) exceed typical values obtained for pure PVA membranes. Besides the pervaporation separation index (PSI) varies from 5.84 to 82.81. Compared to pure PVA membrane with maximum PSI of 47.2, the pervaporation performance was significantly improved. The best separation performance was obtained using the membrane prepared from 5wt.% PVA solution containing 6wt.% fumed silica and at pervaporation temperature of 45°C with permeation flux of 1.69kg/m2h, and selectivity of 50. The highest permeation flux, selectivity and PSI was 2.92kg/m2h, 180 and 82.81, obtained at 60, 30 and 45°C, respectively, while using membranes loaded with 8, zero and 6wt.% of fumed silica in PVA membrane prepared from 5, 10 and 5wt.% PVA solutions, respectively. The novel ceramic support increased mechanical strength of the membrane and protected the ultrathin polymeric top active layer under aggressive operating conditions, especially high pressure gradient across the membrane. Incorporation of fumed silica also resulted in higher water permeation flux. Due to these results, the synthesized membranes are suitable for ethanol purification in industrial scales.