Preparation Of Silicalite-1and Magadiite Supported Membranes And Evaluation Of Their Separation Performance Of Ethanol-water Mixtures

Based on the application of hydrophobic and hydrophilic membranes duringpervaporation membrane separation for bio-ethanol concentration process, thehydrophobic silicalite-1membrane and hydrophilic magadiite membrane weredesigned and prepared on porous alumina substrate. By spin-coating macromoleculemembrane (chitosan and zein) as the structure-directing agent, the orientated growthof silicalite-1was achieved. The plate-like magadiite powder and magadite membranewere prepared through interface–controlled heterogeneous nucleation. The magadiitemembrane exhibited great performance of hydrophilicity and dehydration due to itslamellar structure and abundant hydroxyl.Silicalite-1membrane supported on porous alumina substrate was prepared byin-suit hydrothermal synthetic process. The experimental results showed that themembrane was a,b-orientated with average thickness of~10μm. The silicalite-1membrane showed4.02×10-8mol s-1m-2Pa-1nitrogen permeate at293K. Thepervaporation for3wt%ethanol concentration in feed showed the separation factor (α)of ethanol and the total permeate fluxe (J) were1.67and4.79kg·m-2·h-1at293K.In order to prepare the oriented membranes, chitosan and zein were spin-coatedon the porous alumina substrate as the structure-directing agents, and the a-orientatedsilicalite-1membranes were synthesized. The silicalite-1membrane modified bychitosan and zein had an average thickness of23μm and31μm with2.69×10-8,2.52×10-8mol·s-1·m-2·Pa-1nitrogen permeate at293K, and the membranes got thickeras more times the modifiers coated. The experimental results indicated that thea-orientated membranes were more compact and flat and showed higher separationfactor and lower total permeate flux (α=2.64and2.27for chitosan and zeinrespectively，J=2.36and2.87kg·m-2·h-1for chitosan and zein respectively). At thesame time, the separation factor of ethanol decreased as the temperature and theethanol concentration increased, the permeation flux increased as the temperature andthe ethanol concentration increased.By adding heterogeneous interface in hydrothermal process, the fabricatedmagadiite was plate-like with the size of3~5μm (P-magadiite), specific surface areaof66m2.g-1and pore size distribution between4and5nm. It was the mesoporous material with high specific surface area. The magadiite synthesized through traditionalone-pot hydrothermal process was cauliflower-like (C-magadiite) with specificsurface area of28m2.g-1. P-magadiite showed faster sorption rate and higheradsorption capacity of calcium ions compared with C-magadiite in the absorption anddesorption of calcium ions. The pervaporation process was applied for evaluating theseparation performance of the magadiite supported membrane. Water separationfactor (α) of3.4with total permeation flux (J) of2.66kg·m-2·h-1were obtained at293K for ethanol feed composition of80wt.%. The separation factor of water decreasedas the temperature and the ethanol concentration increased; the total permeation fluxincreased as the temperature increased, the permeation flux decreased as the ethanolconcentration increased.