An imperative approach for fluorosis mitigation: Amending aqueous calcium to suppress hydroxyapatite dissolution in defluoridation

Publication Type  Journal Article
Year of Publication  2019
Authors  Sankannavar, R.; Chaudhari, S.
Journal Title  Journal of Environmental Management
Volume  245
Pages  230-237
Start Page  230
Journal Date  05/2019
Publisher  Elsevier Ltd.
Key Words  Drinking water; Fluoride contamination; Fluorosis; Fluoride toxicity; Fluoride removal; Defluoridation; Hydroxyapatite; Phosphate levels; Calcium amendment; Alkaline water; Fluorosis reversal
Abstract  

Drinking of fluoride (F−) contaminated water causes fluorosis and thus providing safe drinking water to the affected community remains a major challenge. Therefore, defluoridation without disturbing water quality is imperative. Hydroxyapatite (HAP) is proved to have a potential application for defluoridation; however, its dissolution during defluoridation is a concern for its implementation. Experiments conducted by suspending HAP in F− solution and deionized water without F− show that former had high residual pH and PO43- than the latter with Ca2+ being absent in the former. This indicates that Ca2+ had participated in defluoridation and promoted HAP dissolution when Ca2+ was unavailable. Hence, HAP dissolution seems to be a governing step for defluoridation. However, higher residual PO43- and pH affect drinking water quality, and its usage may pose additional health problems. Thus, Ca2+ deficient defluoridated water is unfit for drinking unless it is treated further. Hence, the present work proposes a novel method to overcome HAP dissolution by amending aqueous Ca2+ to F− water. The results show that amending Ca 2+ efficiently prevents HAP dissolution and enhances defluoridation capacity as an added feature. Furthermore, speciation using MINEQL+ and FTIR of fluoride-calcium treated HAPs suggest the possibility of defluoridation by aqueous CaF+ adsorption onto HAP besides F− ion exchange with OH−.

URL  https://authors.elsevier.com/a/1Z8em_6sjVA5fK
DOI  10.1016/j.jenvman.2019.05.088
Citation Key  6264
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