Defluoridation of water through the transformation of octacalcium phosphate into fluorapatite. Issue 8 (August 2019)

• Record Type: Journal Article
• Authors: Idini, Alfredo; Dore, Elisabetta; Fancello, Dario; Frau, Franco
• Is Part Of: Heliyon. Volume 5:Issue 8(2019)
• Publication Date: 2019-08
• Subjects: Materials science -- Materials synthesis -- Environmental science -- Environmental geochemistry -- Environmental pollution -- Water pollution -- Water quality -- Earth sciences -- Water defluoridation method -- OCP synthesis -- OCP-FAP transformation -- Dissolved fluoride removal; Research -- Periodicals; Medical sciences -- Periodicals; Natural history -- Periodicals; Social sciences -- Periodicals; Earth sciences -- Periodicals; Physical sciences -- Periodicals; 507.2
• DOI: 10.1016/j.heliyon.2019.e02288
• Languages: English
• ISSNs: 2405-8440

Abstract

Abstract: The consumption of water with fluoride concentration higher than 1.5 mg/L (WHO recommended limit) is recognized to cause serious diseases, and fluoride removal from natural contaminated waters is a health priority for more than 260 million people worldwide. The octacalcium phosphate (OCP), a mineralogical precursor of bio-apatite, is here tested as a fluoride remover. A new two-step method for the synthesis of OCP is proposed: 1) synthesis of brushite from calcium carbonate and phosphoric acid; 2) subsequent hydrolysis of brushite. Fluoride removal experiments are performed in batch-mode using different initial concentrations of fluoride (from 40 to 140 mg/L) and reaction times. Most of fluoride is removed within the first 2 h of all experiments, and the drinkable limit of 1.5 mg/L is reached within a minimum of 3 h for an initial fluoride concentration of 40 mg/L. The experimental fluoride removal capacity of OCP is 25.7 mg/g, and 4 g of OCP can effectively treat 1 L of water with fluoride concentration up to 50 times higher than the drinking limit of 1.5 mg/L. XRD and chemical characterization of the solid phases, before and after the removal experiments, indicate that OCP transforms into fluorapatite (FAP) uptaking fluoride from solution.