Preparation of 13X from waste quartz and photocatalytic reaction of methyl orange on TiO₂/ZSM-5, 13X and Y-zeolite

TiO₂ photocatalytic reactions not only remove a variety of organic pollutants via complete mineralization, but also destroy the bacterial cell wall and cell membrane, thus playing an important bactericidal role. However, the post-filtration procedures to separate nanometer-levels of TiO₂ and the gradual inactivity of photocatalyst during continuous use are defects that limit its application. In this case, we propose loading TiO₂ on zeolite for easy separation and 13X is considered as a promising one. In our study, 13X-zeolite was prepared by a hydrothermal method and the source of Si was extracted from waste quartz sand. For comparison, commercial zeolite with different microporous and mesoporous diameters (ZSM-5 and Y-zeolites) were also used as TiO₂ supports. The pore size of the three kinds of zeolites are as follows: Y-zeolite > 13X > ZSM-5. Different TiO₂ loading content over ZSM-5, 13X and Y-zeolite were prepared by the sol-gel method. XRD, FTIR, BET, UV-vis, TGA and SEM were used for investigation of material characteristics. In addition, the efficiencies of mineralization and photodegradation were studied in this paper. The effects of the loading ratio of TiO₂ over zeolites, initial pH, and concentration on photocatalytic performance are investigated. The relationship between best loading content of TiO₂ and pore size of the zeolite was studied. The possible roles of the ZSM-5, 13X-zeolites and Y-zeolites support on the reactions and the possible mechanisms of effects were also explored. The best loading content of TiO₂ over ZSM-5, 13X and Y-zeolite was found to be 50 wt%, 12.5 wt% and 7 wt%, respectively. The optimum pH condition is 3 with TiO₂ over ZSM-5, 13X-zeolites and Y-zeolites. The results showed that the degradation and mineralization efficiency of 12.5 wt%GT13X (TiO₂ over 13X) after 90 min irradiation reached 57.9% and 22.0%, which was better than that of 7 wt%GTYZ (TiO₂ over Y-zeolites) while much lower than that of 50 wt%GTZ (TiO₂ over ZSM-5). The materials were recycled four times while the degradation was remained at a higher level.