Internalization of fluoride in hydroxyapatite nanoparticles

Daniel S. Mosiman, Andre Sutrisno, Riqiang Fu, Benito J. Marin~as

Research output: Contribution to journalArticlepeer-review

Abstract

Hydroxyapatite (HAP) is a cost-effective material to remove excess levels of fluoride from water. Historically, HAP has been considered a fluoride adsorbent in the environmental engineering community. This paper substantiates an uptake paradigm that has recently gained disparate support: assimilation of fluoride to bulk apatite lattice sites in addition to surface lattice sites. Pellets of HAP nanoparticles (NPs) were packed into a fixed-bed media filter to treat solutions containing 30 mg-F/L (1.58 mM) at pH 8, yielding an uptake of 15.97 ± 0.03 mg-F/g-HAP after 864 h. Solid-state 19F and 13C magicangle spinning nuclear magnetic resonance spectroscopy demonstrated that all removed fluoride is apatitic. A transmission electron microscopy analysis of particle size distribution, morphology, and crystal habit resulted in the development of a model to quantify adsorption and total fluoride capacity. Low- and high-estimate median adsorption capacities were 2.40 and 6.90 mg-F/g-HAP, respectively. Discrepancies between experimental uptake and adsorption capacity indicate the range of F- that internalizes to satisfy conservation of mass. The model was developed to demonstrate that F- internalization in HAP NPs occurs under environmentally relevant conditions and as a tool to understand the extent of F- internalization in HAP NPs of any kind.

Original languageEnglish (US)
Pages (from-to)2639-2651
Number of pages13
JournalEnvironmental Science and Technology
Volume55
Issue number4
DOIs
StatePublished - Feb 16 2021

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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