State-of-the-art recent applications of layered double hydroxides (LDHs) material in Fenton-based oxidation processes for water and wastewater treatment

Wastewater treatment has become a great concern of this century owing to the advent of different types of refractory pollutants, which needs to be effectively treated with state-of-the-art catalysts and techniques. Layered double hydroxides (LDHs), as two-dimensional (2D) layered materials, are deemed to be promising candidates for environmental remediation due to outstanding advantages, such as high surface area, unique exchangeability of intercalated anions, porous, and stable layered structure. Fenton-based processes have been demonstrated their ability in removal of recalcitrant contaminants even in low quantities. Recently, LDHs and their derivatives have emerged as an important class of Fenton-based catalysts to overcome conventional Fenton process drawbacks, including narrow working pH, potential for secondary contamination, and sludge production. This review aims to summarize the current knowledge about LDHs, different synthesis procedure, and properties of LDHs materials. A systematical investigation on the recent progress in application of multi-metals LDH-based catalysts in Fenton, Fenton-like, photo-Fenton (PF), and electro-Fenton (EF) processes and the corresponding reaction mechanisms were provided. Furthermore, key strategies (oxygen vacancies, carbon materials, incorporation of different metals, magnetic materials) to increase active sites, electron transfer rates, and hydroxyl radicals (•OH) generation, were also described, which thereby lead to improvement in the LDHs performance. The role of LDHs in the design of electrodes and EF membranes were discussed in detail. This study also summarized the applications of LDHs materials as catalysts in Fenton-based processes for elimination of different organic pollutants. Finally, this review focuses on challenges, some crucial issues of current research, and future prospects of LDH-based Fenton catalysts in environmental remediation to achieve excellent catalytic performance. It is believed that this work provides valuable insights into the efficacious applications of LDH materials in the field of Fenton-based processes.