Hafnia ceramic nanofiltration membranes. Part I: Preparation and characterization

We have used a sol-gel process as an efficient method for the preparation of hafnia nanofiltration membranes. A stable colloidal sol was obtained after hydrolysis of an alkoxide and peptization of the hydrous oxide precipitate. After the drying of the sol, the hafnia powder was characterized using several methods, such as X-ray diffraction, dilatometry, thermal analysis, electrophoretic, and BET measurements. The hafnia membrane was obtained by coating the colloidal sol on a mesoporous ceramic support, followed by a drying and sintering of the gelled layer. The membrane was characterized by SEM and nitrogen adsorption-desorption to determine the pore size. The filtration properties of a hafnia membrane sintered at 450 degrees C were determined using water permeability and rejection of solutions containing sucrose, polyethylene glycols of different molecular weights (400, 600, 1000) and salt solutions. This membrane is characterized by a MWCO of 420 Da and pore size near 1 nm. (C) 1998 Elsevier Science B.V. All rights reserved.