Removal of Fluoride by Modified Adsorbents: A Review of Modification Methods and Adsorption Mechanisms

Fluoride is ubiquitously present in the natural environment, and its excessive levels can pose serious threats to human health and industrial production. Among various fluoride pollution control methods, adsorption is recognized for its optimal cost-effectiveness and adaptability. The mechanism of fluoride adsorption and the adsorption capacities of various modified adsorbents have been comparatively analyzed :natural minerals, biomass materials, metal oxides, and several emerging types of adsorbents, among which metal-based adsorbents show the best performance. Four modification methods to enhance the performance of adsorbents have been summarized: acid activation, thermal activation, surface functional group modification, and composite materials. Ultimately, this paper identifies the current limitations of adsorption methods for fluoride removal, including insufficient adsorption capacity and a narrow pH range of applicability. These findings are expected to offer valuable insights for the advancement of adsorbent materials research.