Removal of fluoride from aquatic environment

High fluoride concentrations in aquatic environment, even above 30 mg/L, are often detected in many parts of the world. Due to fluoride effects on health, World Health Organization (WHO) as well as national health authorities have established its maximum permissible concentration in drinking water at the level of 1.5 mg/L. This review article aims to provide detail information on researchers' efforts in the field of fluorides removal during potable water production. The contaminant elimination methods have been broadly divided into three sections, that is, coagulation/precipitation, adsorption and membrane techniques. Both, precipitation with the use of calcium salts or coagulation with aluminum sulfate and ferric salts followed by sedimentation are used for fluoride removal. In electrocoagulation, a coagulant is generated in situ by means of oxidation of anode usually made of aluminum or iron. Adsorption is broadly utilized as it offers acceptable results and it is most appealing technique for the removal of fluorides regarding costs, simplicity of outline and operation. Alumina/aluminum-based materials, clays and soils, some minerals and carbon-based materials as well as layered double oxides, nanosorbents and biosorbents, they all have been tested as adsorbents for fluorides removal. Among membrane techniques reverse osmosis, nanofiltration, ultrafiltration in integrated systems, electrodialysis and Donnan dialysis have been discussed.