Recent developments and challenges in zeolite-based composite photocatalysts for environmental applications

Aluminosilicate zeolites have been found to be effective supports of semiconductor photocatalysts for the removal of organic compounds in wastewater and air. In this review, we summarize the progress in the application of zeolite materials such as Y, ZSM-5, mordenite, beta and clinoptilolite for improving the performance of semiconductor photocatalysts in degradation of environmental pollutants. The main synthesis strategies and the mechanisms of organic compounds adsorption and photocatalysis by zeolite-based photocatalysts are explicated in detail. Meanwhile, various types of zeolite-based photocatalytic composites are also thoroughly summarized. The more reliable zeolite-based photocatalysts with high photocatalytic activity under visible or sunlight irradiation should be extensively investigated. Additionally, we highlight the advancements for improving performance of different zeolite-based composites in photocatalytic degradation organic contaminants in wastewater and air. The achieved progress demonstrates that the photocatalytic enhancement of zeolite-based composites is predominantly dependent on the enhanced adsorption performance, as well as the high separation and transfer efficiency of photogenerated charge carriers. Hence, the characteristics of the zeolite-based composites (surface area, pHpzc value, hydrophobic, band gap and band edge), the nature of organic contaminants and other experiment factors need to be taken into account in applying to photodegradation process involving this catalyst. Finally, the current challenges and perspectives for the future research of these photocatalysts are presented.