Titania immobilized over Fe-functionalized beta and silicalite zeolites for tetracycline photocatalytic degradation under visible light

Abstract

Titania photocatalyst is widely employed in the removal of organic pollutants from water streams. However, TiO₂ suffers from agglomeration and is mostly active under UV light resulting in low system efficiency. In this study, we prepared sol–gel TiO₂ immobilized on beta (BEA) and silicalite zeolites for the photocatalytic degradation of tetracycline antibiotics under visible light. Ferric ions were incorporated into the supported Titania photocatalyst via ion exchange method to enhance its visible light absorption. The deposition of the Titania over BEA zeolite greatly enhanced its adsorption efficiency (from 5.6% to 24%) and surface area (from 90 to 305.9 m²/g) while silicalite support only slightly affected the adsorption of Titania. The scanning electron microscope (SEM) characterization of the photocatalysts indicated that the zeolite structure was conserved after modification and the UV–VIS DRS characterization confirmed the enhancement of visible light absorption. The TiO₂/Fe-Beta was able to degrade 100% of tetracycline (TC) in solution under blue light after 90 min compared to only 30% by TiO₂/Fe-silicalite and 28% by TiO₂. When the weight percentage of TiO₂ in the TiO₂/Fe-silicalite photocatalyst increased from 20% to 60%, its efficiency increased from 87% to 99% after 300 min. Similar results were also obtained under white light, where the TiO₂/Fe-Beta achieved the highest efficiency (81.5%) as compared to TiO₂/Fe-silicalite (66.6%) and TiO₂ (44.7%). We attribute this enhanced performance of TiO₂/Fe-Beta to enhanced adsorption capacity due to BEA immobilization and improved visible light absorption.