Buoyant titanium dioxide (TiO2) as high performance photocatalyst and peroxide activator: A critical review on fabrication, mechanism and application

Abstract

Titanium dioxide (TiO2) photocatalyst is widely used in wastewater treatment. The favourable attributes of TiO2 such as chemically stability, cost-effectiveness, low toxicity to humans and high catalytic activity have received extensive attention from researchers seeking to design better materials. Nevertheless, one of the drawbacks of TiO2 photocatalyst is the powder form which is capable of reducing its performance. This phenomenon is attributed to the low active surface area, decreased light absorption and limited contact area with the pollutants in an aqueous system. Therefore, researchers have developed new ideas by immobilising potential catalysts onto a buoyant substrate to design an effective buoyant photocatalyst. This review aims to discuss the crucial properties of the buoyant substrates and promote the benefits of designing the ideal TiO2-based buoyant photocatalysts. Moreover, several vital parameters have been underlined in the fabrication methods to ensure high stability and durability of the buoyant photocatalysts during the photocatalysis process. Additionally, the activation methods of hydrogen peroxide (H2O2), persulfate (PS) and peroxymonosulfate (PMS) for the photodegradation of pollutants are also highlighted in this review paper. The good reusability of the synthesised buoyant photocatalysts is proven as a good indicator of their stability. Furthermore, this review article suggests potential guidelines for the researchers in the fabrication of the TiO2-based buoyant photocatalysts for wastewater treatment applications in the future.