A Review on the Application of LDH Based Catalysts in Advanced Oxidation Processes for Degradation of Emerging Contaminants

Layered double hydroxide (LDH) is a class of anionic clays with flexible tunability, facile exchangeability of intercalated anions, good thermal stability, and plentiful active sites. Due to the numerous advantages, LDH have been widely used as catalysts, catalyst or catalyst carriers in advanced oxidation processes (AOPs) to degrade organic pollutants (especially recalcitrant emerging contaminants such as antibiotics) in water, and exhibit excellent catalytic performance. To promote the application of LDH based catalysts (LDH) in wastewater treatment, this article reviews the properties, types, synthesis methods of LDH catalysts, and the performance and mechanism of LDH in the degradation of emerging contaminants in common AOPs such as heterogeneous Fenton process, persulfate activation, and photocatalysis. LDH catalysts have various types such as LDH, the oxides of LDH (LDO) and nanocomposites. Especially, LDO and nanocomposites have good dispersibility, easy separation, and synergistic effects, which are conducive to improving catalytic performance. Furthermore, LDH catalysts can be synthesized using simple preparation methods such as hydrothermal and co precipitation methods. By selectively adjusting the composition and structure of LDH, excellent pollutant removal efficiency can be achieved in different types of AOPs by various degradation mechanisms. Finally, based on the current challenges faced by LDH catalysts, suggestions and future research priorities were proposed, such as developing green and efficient synthesis methods and optimizing material design.