Titania-zeolite composite for tetracycline photocatalytic degradation under visible light: A comparison between...

In this study, TiO₂ supported over embryonic Beta zeolite (BEA) was prepared for the photocatalytic degradation of Tetracycline (TC) antibiotic under visible light. The immobilization of sol-gel TiO₂ over the zeolite increased its surface area from 33 (m²/g) to 226 (m²/g) and enhanced its adsorption efficiency from 8 % to 18 %. In order to expand the photocatalytic activity of TiO₂ towards the visible light region (i.e. λ > 380 nm), two different metal sensitization techniques with Iron ions from aqueous solution of FeCl₃ were explored. In the ion-exchange method, the substitutional cations within the TiO₂/BEA structure were exchanged with Fe³⁺. Whereas, in the doping technique, solgel TiO₂ was doped with Fe³⁺ during its synthesis and before its immobilization over Zeolite. Four different samples with 20, 40, 60, and 100 % w/w of TiO₂/BEA ratio were prepared. After testing the various ion-exchanged photocatalysts under blue and white lights, only Fe-60%TiO₂/BEA showed better activity compared to pure TiO₂ under white light at TC initial concentration, C _o = 20 ppm. For the doped immobilized Titania with 60 wt% TiO₂/BEA, three different doped photocatalysts were prepared with 3 %, 7 %, and 10 % per mole Fe/TiO₂. All the Fe-doped TiO₂/BEA photocatalysts showed better activity compared to pure TiO₂ under white light. Under solar irradiations, the 3 % Fe-doped TiO₂/BEA was able to degrade all TC within 120 min, while Fe-60%TiO₂/BEA needed 200 min, and TiO₂ needed more than 300 min. This enhanced performance was a result of both increased surface area due to immobilization over BEA as well as iron doping by Fe³⁺ that simultaneously increased the visible light absorption of TiO₂ and minimized the charge carrier recombination effect.