Fabrication of mesoporous TiO₂ membranes by a nanoparticle-modified polymeric sol process

A straightforward synthesis of crack-free mesoporous titania membrane on a macroporous support without intermediate layers by a nanoparticle-modified polymeric sol-gel process is reported. TiO₂ nanoparticle (Degussa P25) was dispersed into the prepared sol to toughen the formed gel. This helped to avoid the cracking of membrane during the drying and early stage of sintering, particularly when the sol-gel transformation occurred on a substrate with an uneven surface. The results of X-ray diffraction and Brunauer-Emmett-Teller analyses show that the nanoparticle doping did not significantly affect the particle size of TiO₂ nanocrystals; however, it slightly broadened the pore size distribution because it has a larger particle size compared to the prepared materials. The sols with and without P25 nanoparticle were subsequently dip-coated on a support with average pore size of 150nm, thus formed a mesoporous membrane layer after drying and sintering processes. An integrated, crack-free mesoporous TiO₂ membrane layer was obtained by this method, while the membrane prepared with the original sol developed a few cracks. Further, the filtration experiment showed that the prepared membrane had a high flux, and the membrane with nanoparticle modification delivered better separation performance by rejection of dextran.