Abstract
Fluoride is widely found in soil–water systems due to anthropogenic and geogenic activities that affect millions worldwide. Fluoride ingestion results in chronic and acute toxicity, including skeletal and dental fluorosis, neurological damage, and bone softening in humans. Therefore, this review paper summarizes biological processes for fluoride remediation, i.e., bioaccumulation in plants and microbially assisted systems. Bioremediation approaches for fluoride removal have recently gained prominence in removing fluoride ions. Plants are vulnerable to fluoride accumulation in soil, and their growth and development can be negatively affected, even with low fluoride content in the soil. The microbial bioremediation processes involve bioaccumulation, biotransformation, and biosorption. Bacterial, fungal, and algal biomass are ecologically efficient bioremediators. Most bioremediation techniques are laboratory-scale based on contaminated solutions; however, treatment of fluoride-contaminated wastewater at an industrial scale is yet to be investigated. Therefore, this review recommends the practical applicability and sustainability of microbial bioremediation of fluoride in different environments.
Highlights
Fluorine is a highly electronegative halogen [1] and essential component (13th) in the Earth’s crust with 625 mg kg−1 average concentration [2,3]
This paper summarizes sources, toxicity, geochemistry, and bioaccumulation of fluoride in plants, including microbial technology available for fluoride remediation
Weathering and mineral dissolution of fluoride are assisted via cation exchange of Na+ and K+ ions in the aquifer substrate against Ca2+
Summary
Fluorine is a highly electronegative halogen [1] and essential component (13th) in the Earth’s crust with 625 mg kg−1 average concentration [2,3]. Anthropogenic sources include of fluoride ions in the soil–water systems. Adsorbents used for the fluoride removal are activated alumina [87,96], activated carbon prepared from Moringa indica bark [97], laterite [98], and waste residue [99] These methods have limitations such as high energy consumption, high cost, production of secondary contaminants, and inefficiency in removing pollutants from wastewater [100]. The primary objectives of this review are to highlight the (a) source, toxicity, and geochemistry of fluoride ions in various environments; (b) solubility and bioavailability of fluoride in subsurface systems; (c) fluoride uptake and bioaccumulation in plants; and (d) microbial approaches for fluoride remediation. Several potential future perspectives are proposed for further studies using bioaccumulation and microbial remediation methods for fluoride removal
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