The lesser and excessive amounts of F− ions are both unhealthy for human health. Due to an insufficient amount of F−, the formation and decay of teeth is observed, but excessive fluoride is linked to the diagnosis of fluorosis leading to hyperactivity, Musculoskeletal abnormalities, and brain damage due to excessive fluoride exposure during the development of tooth enamel. Before opting for the method of treatment for the fluoride-contaminated water, the chemical composition of surface and subsurface water is imperative. The presence of volcanic ash and some fertilizers in the soil also leads to an increase in the concentration of F−. Sometimes a low concentration of F− also has effective health benefits, but F− at concertation > 1 ppm can lead to several health hazards. Excessive use of it over a long period of time can cause changes in DNA structure. In order to produce usable water, numerous technologies are being used for the removal of F− and its derivatives. The major technologies used for the removal of F− from waste water are green nanomaterials, capacitive deionization (CDI), membrane technology, and electrocoagulation. Apart from F− removal from waste water, techniques used for natural water are equally important, viz. adsorption technology using various adsorbents. Some effective adsorbents are namely zeolites, alumina, organic based, Shell based including carbon-based nanotubes and graphite, metallopolymers and variety of microspheres. The defluoridation of water using modified activated alumina, chitosan derivatives, clays and muds, composites, and various separation techniques having merits and demerits are in use. Mechanisms used in the fluoride removal techniques are generally Adsorption, Nano-adsorption, Reverse-osmosis, Coagulation-Precipitation, Electrodialysis, Electrocoagulation, Nanofiltration, Ion exchange, Membrane dialysis etc.
