Fluoride Contamination in Groundwater: Review of Advanced Remediation Techniques

Abstract

Fluorine is the most reactive halogen, occurring naturally as fluoride (F⁻) in rocks, such as cryolite and fluorapatite, with groundwater fluoride concentrations varying from 1 to 35 mg/L due to geological circumstances or effluent discharge. Fluoride minerals are typically insoluble in water and comprise 0.06%–0.09% of the Earth's crust. Excessive fluoride consumption can result in dental and skeletal fluorosis, impacting teeth and bones by creating hard fluorapatite, which causes brittleness and abnormalities. Extended exposure can advance from dental fluorosis to debilitating skeletal fluorosis. Effective water treatment encompasses centralized or decentralized methods, such as screening, flocculation, filtration, and disinfection, to enhance quality. Advanced techniques, like adsorbents, membrane filtration (membrane filtration technology [MF], ultrafiltration [UF], nanofiltration [NF], and reverse osmosis [RO]), and UV disinfection, emphasize efficiency, cost-effectiveness, and operational simplicity. Nanoparticles (NPs), esteemed for their elevated surface-to-volume ratio and reactive sites, are extensively utilized in sectors, such as cosmetics, building, and environmental cleanup. This review provides current information on significant nanocomposites for fluoride removal from water. NPs exhibiting elevated surface-to-volume ratios are advantageous materials for water purification, especially for the elimination of fluoride. Magnetic Fe₃O₄ NPs, particularly Fe₃O₄–SiO₂ nanocomposites, have significant adsorption capacity, facile magnetic separation, durability, and reusability, rendering them very efficient for water treatment. Calcite (CaCO₃) NPs exhibit significant fluoride adsorption; nevertheless, their efficacy is contingent upon pH conditions. Future research must concentrate on the development of sophisticated nanocomposites, the optimization of adsorption systems, and the evaluation of regeneration capacity, lifecycle effects, and environmental safety of nanomaterials.