Characterization and preparation of porous membranes with a natural Mexican zeolite

The potential of a natural Mexican zeolite from the northern state of Sonora as microfiltration membranes was evaluated. The zeolite was characterized by x-ray diffraction, scanning electron microscopy (SEM), N₂ physisorption and thermal analysis. Clinoptilolite and heulandite were the main components of the zeolite. The crystallinity of this material was confirmed. Two steps made up the manufacturing process of porous membranes: pressing and sintering. It was necessary to use lubricants and agglomerants with different particle size of the zeolite. The best properties of the porous membranes were obtained using zinc stearate (4 wt%) as lubricant, boehmite (15 wt%) as agglomerant and the best particle size ranged from 63 to 300 μm. Moreover it was observed that the zeolite granule distribution improved the press of the materials by approximately 10% in the distribution proposed. The thermal treatment of the porous membranes was carried out at several temperatures (500-1000°C). The porous membranes obtained were characterized by x-ray diffraction, scanning electron microscopy and N₂ physisorption to study the global porosity, phase transformations and pore size distribution. A loss of crystallinity, decreased porosity and a lower specific surface area were found when the sintering temperature was increased. The results of pore distribution suggest that these materials are porous membranes for microfiltration.