Synthesis, application and catalytic performance of layered double hydroxide based catalysts in advanced oxidation processes for wastewater decontamination: A review

Layered double hydroxides (LDHs) are a class of anionic clays with flexible tunability, facile exchangeability of intercalated anions, good thermal stability, and plentiful active sites. By virtue of their advantages, LDHs, as catalysts, catalyst precursors or catalyst supports, have been widely used in advanced oxidation processes (AOPs) to degrade organic pollutants in water and showed prominent catalytic performance as concluded from nearly 100% removal of contaminants in a relatively short time. To shed light on the synthesis, application and catalytic performance of LDH-based catalysts, this review summarized the properties, categories, synthesis and characterization methods of LDH-based catalysts, and their applications, reaction mechanisms and the corresponding influencing factors in heterogeneous Fenton-like processes, sulfate radical based AOPs and photocatalysis. Compared with LDHs, LDOs and nanocomposites possess other performances that are beneficial for AOPs catalytic processes, such as good dispersity, easy separability and synergistic effect. Moreover, the optimum material design and corresponding reaction mechanisms would be varied with the types of AOPs. In the end, based on the current challenges in LDH-based catalysts, future researches are suggested to focus on developing green and efficient synthetic method, optimizing material design, and promoting their practical application.