Synthesis and characterization of porous ferrimagnetic membranes

Nanoporous ferrimagnetic membranes based on maghemite (gamma-Fe2O3) and cobalt ferrite (Fe2CoO4) were prepared by the sol-gel route using colloidal ferrofluids. These membranes were used for the separation of paramagnetic and diamagnetic gaseous species at room temperature. Their magnetic properties were analyzed using a SQUID magnetometer, and their structures and porous textures were studied by X-ray diffraction, scanning electron microscopy and nitrogen adsorption-desorption analysis. O-2-N-2 adsorption and air separation experiments were carried out in order to study the magnetic interactions in static and dynamic conditions, respectively. A slight effect of the magnetic field on the selectivity of these membranes was observed. However, the measured selectivity values alpha(N2/O2) were always close to 1. Although an optimization of the membranes remains possible, it seems difficult to reach the high selectivity values required for technological applications. (C) 2003 Elsevier Inc. All rights reserved.