Surface modification of nanocomposite ceramic membranes by PDMS for condensable hydrocarbons separation

PDMS/ceramic nanocomposite membranes were fabricated via dip-coating method. Tubular porous nanocomposite ceramic supports were used as membrane substrates and polydimethylsiloxane was applied as a top active layer. The hybrid membranes were characterized morphologically by scanning electron microscopy (SEM) and their gas transport properties were measured using single gas permeation (butane and hydrogen) at ambient temperature and different pressures. SEM micrographs confirmed the penetration of polymeric layer into ceramic support pores at low concentrations of PDMS solution. Experimental results clearly indicated that the undesirable penetration during the dip-coating stage could be avoided by increasing the concentration of PDMS coating solution. This led to the formation of a uniform and dense coating layer without penetration into pores of the support. These hybrid membranes showed higher permeability combined to a suitable selectivity in comparison with dense homogeneous PDMS membrane. In addition, at low pressures, the high selectivity of PDMS/ceramic nanocomposite membranes for condensable hydrocarbons separation revealed that the dominant mechanism is solution-diffusion. (C) 2009 Elsevier B.V. All rights reserved.