Synthesis of hydroxyapatite-iron oxides nanocomposite for fluoride adsorption in groundwater samples

SCHEVERIN, V. N.; SCHMIDT, L. N.; DIAZ, E. M.; HORST, M. F.; LASSALLE, V. L.

ENVIRONMENTAL GEOCHEMISTRY AND HEALTH

SPRINGER

Año: 2025 vol. 47

0269-4042

Fluoride contamination in groundwateris a major environmental concern due to its serioushealth implications. Among various remediation strategies, hydroxyapatite-based adsorbents are promisingdue to their high affinity for fluoride ions. This studyevaluates the performance of two hydroxyapatite–iron oxide nanocomposites, Hap–IONp–1 and Hap–IONp–2, synthesized via a hydrothermal methodwith varying iron oxide content. The materials werecharacterized by X-ray diffraction, scanning electronmicroscopy, and Fourier-transform infrared spectroscopy. Kinetic and equilibrium adsorption experimentswere conducted in model solutions, with the pseudosecond-order and Freundlich models providing thebest fit. The influence of pH on fluoride removalwas also assessed. Further evaluation was performedusing three groundwater samples from differentregions of Argentina, all exceeding the World HealthOrganization limits for fluoride and arsenic. Thesamples differed in fluoride concentration, hardness, alkalinity, and other dissolved species. Adsorption experiments over six reuse cycles revealed thatHap–IONp–1, with a lower iron oxide content, consistently achieved higher fluoride removal, particularly in waters with moderate fluoride levels and highhardness. However, the efficiency of both materialsdecreased in samples with high alkalinity and fluorideconcentrations, likely due to ion competition. Thesefindings highlight the importance of water chemistryin adsorbent selection and support the development oftailored materials for effective fluoride remediation innatural waters.