Synthesis of thin defect-free hydroxy sodalite membranes: New candidate for activated water permeation

Successful and rapid synthesis of thin defect-free hydroxy socialite (H-SOD) membranes on alpha-Al2O3 supports was carried out using direct hydrothermal synthesis. The membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-gravimetric analysis (TG/DTA), single gas permeation measurements, and water pervaporation experiments at different temperatures and pressures. The synthesis was carried out under rotation for only 3.5 h at 413 K. An inter-grown pure H-SOD membrane was made with a layer thickness of 2 mu m. Gas permeation results showed that the membrane was impermeable to N-2 and the He permeance was as low as 10(-11) mol(-1) m(-2) Pa-1, which validates absence of defects. Pervaporation experiments showed reasonable water fluxes up to 2.25 kg m(-2) h(-1) at 473 K. Water permeance was found to increase exponentially with increasing temperatures and was not affected by changing the absolute feed pressure. Permeance at temperatures above 350 K was attributed to activated transport of water through H-SOD membranes. (c) 2007 Elsevier B.V. All rights reserved.