The reduction of fluoride concentrations in water is one of many concerns. Adsorption is the most widely used technology for fluoride removal and the center to development of adsorption technology is the improvement of adsorbents. This review classifies the typical fluoride removal adsorbents into four types: metal oxides/hydroxides, biopolymers, carbon-based, and other adsorbents. The exploitation of new materials and the synthesis of composite materials are two ways of developing new adsorbents. In comparison to the discovery of novel adsorbents for fluoride adsorption, research into the composite synthesis of different types of conventional adsorbents has proliferated in recent years. The traditional adsorbents used the earliest, metal oxides, can act as active centers in a wide range of applications for modifying and compounding with other types of adsorbents. This study emphasizes reviewing the research on fluoride removal by composite adsorbents synthesized from different types of metal-modified materials. Seven factors were compared in terms of material characterization, initial fluoride concentration, adsorbent dose, pH, temperature, reaction time, and maximum adsorption capacity. The modification of composite adsorbents is facile and the synergistic effect of the different types of adsorbents significantly improves fluoride adsorption capacity. Metal composite adsorbents are synthesized by facile coprecipitation, hydrothermal, or impregnation modification methods. The adsorption mechanisms involve electrostatic attraction, ion exchange, complexation, and hydrogen bonding. The fluoride adsorption capacity of composite adsorbents has generally improved, indicating that most modifications are successful and have application prospects. However, to achieve significant breakthroughs in practical applications, numerous issues such as cost, separation/regeneration performance, and safety still need to be considered.

As the pollution and destruction of global water resources become more and more severe, the treatment of wastewater has attracted significant attention. The template method is a synthetic method in which the template is the main configuration to control, influence, and modify the morphology as well as control the dimensions of the material, thus achieving the properties that determine the material. It is simple, highly reproducible, and predictable, and more importantly, it can effectively control the pore structure, size, and morphology of the material, providing a novel platform for the preparation of adsorbent materials with excellent adsorption properties. This review focuses on the classification of the templates according to their properties and spatial domain-limiting capabilities, reviews the types of hard and soft template materials and their synthetic routes, and further discusses the modulation of the morphological structure of the materials by the introduction of templates. In addition, the application and adsorption mechanisms of heavy metal ions and dyes are reviewed based on the regulatory behavior of the template method.