Novel apatite-based sorbent for defluoridation: Synthesis and sorption characteristics of nano-micro-crystalline hydroxyapatite-coated-limestone

Cynthia M. Kanno, Rebecca L. Sanders, Steven M. Flynn, Genevieve Lessard, Satish Chandra Babu Myneni

Research output: Contribution to journalArticlepeer-review

58 Scopus citations

Abstract

Elevated levels of fluoride (F-) in groundwaters of granitic and basaltic terrains pose a major environmental problem and are affecting millions of people all over the world. Hydroxyapatite (HA) has been shown to be a strong sorbent for F-; however, low permeability of synthetic HA results in poor sorption efficiency. Here we provide a novel method of synthesizing nano- to micrometer sized HA on the surfaces of granular limestone to improve the sorption efficiency of the HA-based filter. Our experiments with granular limestone (38-63, 125-500 μm) and dissolved PO43- (0.5-5.3 mM) as a function of pH (6-8) and temperature (25-80 °C) indicated rapid formation of nano- to micrometer sized HA crystals on granular limestone with the maximum surface coverage at lower pH and in the presence of multiple additions of aqueous PO43-. The HA crystal morphology varied with the above variables. The sorption kinetics and magnitude of F - sorption by HA-coated-fine limestone are comparable to those of pure HA, and the F- levels dropped to below the World Health Organizations drinking water limit of 79 μM for F- concentrations commonly encountered in contaminated potable waters, suggesting that these materials could be used as effective filters. Fluorine XANES spectra of synthetic HA reacted with F- suggest that the mode of sorption is through the formation of fluoridated-HA or fluorapatite at low F- levels and fluorite at high F- loadings.

Original languageEnglish (US)
Pages (from-to)5798-5807
Number of pages10
JournalEnvironmental Science and Technology
Volume48
Issue number10
DOIs
StatePublished - May 20 2014

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry

Fingerprint Dive into the research topics of 'Novel apatite-based sorbent for defluoridation: Synthesis and sorption characteristics of nano-micro-crystalline hydroxyapatite-coated-limestone'. Together they form a unique fingerprint.

Cite this