Uncovering nano-bonechar for attenuating fluoride in naturally contaminated soil.

Fluoride ion (F−) is one of the major geogenic contaminants in water and soil. Excessive consumption of these geogenic contaminants poses serious health impacts on humans and plants. In this study, a novel carbonaceous material, nano-bonechar, was synthesized from cow bones and applied as a soil amendment at rates of 0, 0.5, 1, and 2% to remediate and revitalize naturally F−-contaminated soil. The results revealed that the nano-bonechar significantly reduced the mobility and bioavailability of F− by 90% in the contaminated soil, and improved the soil quality by increasing the soil water holding capacity, soil organic matter, and the bioavailable contents of PO 4 3−, Ca2+, and Na+. Subsequently, the pot experiment results showed a significant reduction in the uptake of F- by 93% in Zea mays plants. Moreover, the nano-bonechar application improved the plant's growth, as indicated by the higher fresh and dry weights, root and shoot lengths, and total content of PO 4 3−, Ca2+, and K+ than those of un-amended soil. The F-immobilization in soil was mainly due to the presence of the hydroxyapatite [Ca 10 (PO 4) 6 (OH) 2 ] mineral in the nano-bonechar. Ion exchange between OH− (of nano-bonechar) and F− (of soil), and the formation of insoluble fluorite (CaF 2) contributed to the attenuation of F− mobility in the soil. It is concluded that nano-bonechar, due to its size and enrichment in hydroxyapatite, could successfully be utilized for the rapid remediation and revitalization of F−-contaminated agricultural soil. [Display omitted] • A novel material, nano-bonechar, was produced from cow bones via pyrolysis and milling. • Nano-bonechar immobilized 90% F− in naturally contaminated agricultural soil. • Nano-bonechar tended to bind F− as fluorite (CaF 2) and fluorapatite [Ca 10 (PO 4) 6 F 2 ]. • F− uptake by Zea mays was significantly reduced by 93% in the amended soil. • PO 4 3−, Ca2+, and K+ uptake by Zea mays significantly enhanced in the amended soil. [ABSTRACT FROM AUTHOR]