| Patterned Porous Titania (PP-TiC^) is promising in the photocatalysis field due to its special property. However, its separation and recovery cost plenty of time and energy due to its fine size in the photodegradation of dyes. Also, in the hybrid photocatalysis-membrane system, the membrane fouling is caused by the freely suspended TiO2nanoparticles. Besides, because of its wide band gap, it can only absorb the ultraviolet light that consists4-6%of the sunlight, which limits its photocatalytic activity under the irradiation of sunlight. Therefore, the recovery and modification of patterned porous titania were studied in this paper.The pH-sensitive calcium-alginate (CA) hydrogel was chosen as a support to immobilize the patterned porous titania. PP-TiCVCA microspheres were prepared by the dropwised method. Their swelling behavior, photocatalytic activity and recovery were studied. Results indicate that PP-TiO2/CA microspheres swelled progressively at pH6.86, but they barely swelled at pH2. The microspherization of PP-TiO2is beneficial to remove Methylene Blue (MB) at pH6.86, whereas that of P25-TiO2inhibits the removal of MB. Because the swelling of PP-TiO2/CA microspheres benefits the adsorption of MB and the patterned porous structure is not blocked by the immobilization of PP-TiO2. But the swelling of P25-TiO2/CA microspheres does not offset the decrease of active sites of P25-TiO2nanoparticles due to the immobilization of P25-TiO2. The removal rate of MB is improved by the reused PP-TiO2/CA microspheres and the recovery of PP-TiO2/CA microspheres did not cost energy, but the reused PP-T1O2presents a little less efficiency in the second run and the whole process costed3.38X106J. So it is easy to recover the PP-TiO2/CA microspheres compared with the freely suspended patterned porous titania.To decrease the membrane fouling caused by the suspended TiO2in the hybrid photocatalysis-membrane process, the removal of MB was studied by the hybrid photocatalysis-dead-end microfiltration process with PP-TiO2/CA microspheres as photocatalyst. It is demonstrated that the utilizing of PP-TiO2/CA microspheres can decrease the membrane fouling and PP-TiO2/CA microspheres present better performance than the suspended PP-TiO2The removal rate of MB was as high as90%in the continuous two hours with PP-TiO2/CA microspheres as photocatalyst, and the permeate flux was the as same as that without photocatalyst, whereas the concentration of MB in the permeate side was close to the initial concentration of MB using PP-TiO2as photocatalyst. It indicates that the photodegradation of MB by the hybrid system no longer worked at that time. Because larger particles have a higher lift force compared with the drag force, so the PP-TiCVCA microspheres can be carried away by the bulk fluid. But the small PP-TiO2can easily deposit on the surface of the membrane to decline the permeate flux and MB removal rate.To enhance the photocatalytic activity of PP-TiO2under the irradiation of sunlight, PP-TiO2was modified by decorating conductive polymer. Polypyrrole/patterned porous titania was prepared by the "in-situ" polymerization method using patterned porous titania as a template, and its photocatalytic activity was investigated under the irradiation of sunlight simulated by xenon light. Results indicate that PPy was decorated in the channels of the patterned porous titania, but with the increase of PPy the channels were blocked. The absorption spectra of the composites were extended to the visible region, which enhances the photocatalytic activity of PP-TiO2under the sunlight irradiation. The photocatalytic activity of the composites reaches the maximum at the molar ratio0.1(PPy vs. PP-TiO2). |
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