Direct sunlight-driven degradation of 2-chlorophenol catalyzed by kaolinite-supported ZnO

Abstract

Commercial and laboratory-prepared ZnO nanoparticles are assessed here as a photocatalyst in photodegradation of aqueous 2-chlorophenol under direct sunlight. Kaolinite is used as a support for ZnO to enable its recovery after reuse. The composite ZnO/kaolinite is prepared by growing ZnO nanoparticles directly on kaolinite surface and is characterized by a number of methods such as electronic absorption spectra, photoluminescence spectra, X-ray diffraction and scanning electron microscopy. All ZnO systems (commercial, synthetic and supported) exhibit the wurtzite phase. The composite ZnO/kaolinite shows higher photocatalysis efficiency in 2-chlorophenol degradation over both commercial and synthetic ZnO powders. The composite ZnO/kaolinite is also easier to recover and reuse, showing no observable loss in its catalyst efficiency even after five cycles. These features highlight the merit of using composite ZnO/kaolinite as photocatalyst in water purification with direct sunlight for the first time. All catalyst systems are more efficient in basic media (pH ~ 8.5) than in neutral and acidic media, as rationalized by the point of zero charge concepts here. Moreover, the composite ZnO/kaolinite shows enhanced catalytic efficiency in 2-chlorophenol photodegradation in a wider pH range, compared to other counterparts, which shows another added value.