Pervaporation study of ceramic-supported thin PVA membranes in dehydration of ethanol: Effect of PVA coating gel concentration

Thin polyvinyl alcohol (PVA) layers were prepared on top of porous molite ceramic supports. Mercury porosimetry analysis was carried out confirming a porosity of 22%-34% for the supports respect to the sintering condition. Ceramic-supported thin PVA membranes were characterized via SEM and dehydration of aqueous ethanol. Thickness of the PVA layer formed on top of the support was in the range of 2–10 μm. Effects of PVA concentration in the coating gel on thickness and density of the active layers were investigated using SEM micrographs. PVA concentration of the coating gel is the most effective parameter on active layers thickness and density, after repetition of the coating process. Dehydration of ethanol was performed at 30–60 °C with feed water concentration of 10 wt.%. These membranes exhibited adequate water fluxes (14–81 g/m2h) and high separation factors (44–119). The flux and separation factor values exceeded typical values obtained for PVA membranes. The novel ceramic support increases mechanical strength of the membrane and protects the ultrathin polymer top layer under aggressive operating conditions, specially the pressure gradient across the membrane, resulting in high flux. Besides decreasing swelling of the PVA top layer, results in high separation factor. These two are both favorable for an effective separation but in common polymeric membranes increasing one of them diminishes the other one. However this novel ultrathin PVA membrane has the advantages of high selectivity beside high permeation flux.