Exploring layered double hydroxide efficiency in removal of fluoride ions from water: material insights, synthesis and modification strategies and adsorption mechanisms

Abstract

Fluoride ion pollution is currently one of the important factors causing chemical risks in drinking water. The adsorption method is an important way to solve this problem due to its simple operation and low cost. The key to the adsorption method is to develop efficient fluoride ion adsorption materials. Among many adsorbents, layered double hydroxide (LDH) materials have the characteristics of simple preparation, adjustable layer composition, adjustable interlayer anion type, and high adsorption capacity. Thus, they are considered to be highly promising fluoride ion adsorbents. This work provides a comprehensive summary of LDHs used for fluoride ion adsorption, from the perspectives of composition, synthesis, modification, environmental factors affecting adsorption performance, and adsorption mechanisms. Notably, this work distinguishes between LDH and its derivatives such as mixed metal oxides because they have different fluoride adsorption mechanisms. Specifically, the general discussion is focused on the LDH phase, while MMO and complexes are discussed in the modification section. Additionally, problems and future directions in the development of LDH-based fluoride ion adsorbents are explored.