Preparation and performance of H-SOD membranes: a new synthesis procedure and absolute water separation

Abstract

Successful and rapid synthesis of thin defect free hydroxy sodalite (H-SOD) membranes with a thickness of 2 μm on α-Al2O3 supports was achieved using direct hydrothermal synthesis. The membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and single gas permeation measurements. Single component pervaporation experiments were carried out to investigate water flux through H-SOD membranes at different temperatures and pressures. The membranes were used for pervaporative separation of water from water-isopropanol (IPA) mixtures. The effects of IPA feed concentration and temperature were studied on the permeation flux and the separation factor of water with respect to IPA. The membrane was impermeable to N2 and He permeance was as low as 10–11 mols–1m–2Pa–1, which validates absence of defects. Pervaporation fluxes of water up to 2.25 kgm–2h–1 at 423 K were obtained. In pervaporation of water from water/IPA mixtures, the membranes showed absolute selectivity towards water regardless of temperature or feed concentration. Increasing temperature seemed to have little effect on flux values; but increasing the water content in feed led to a dramatic increase in flux through the membrane.