Sorption of Np(V) by synthetic hydroxyapatite

Robert C. Moore, Kathleen Holt, Hongting Zhao, Ahmed Hasan, Nasser Awwad, Mona Gasser, Charles Sanchez

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


The sorption of Np(V) to synthetic hydroxyapatite was determined in batch experiments in a 0.1 M NaClO4 solution. The hydroxyapatite used was of high purity as determined by SEM, EDS, XRD, FT-IR and ICP-MS analysis. Results from kinetic experiments with an initial Np(V) concentration of 1 × 10-7 to 1 × 10-6 indicate the sorption process is relatively fast with more than 90% of the Np(V) being sorbed in approximately 3 hours. Equilibrium experiments performed over the pH range of 6 to 11 indicated sorption is strongly pH dependent with distribution coefficients, Kd values (mL/g), increasing from 123 L/mole at pH 6 to 69 200L/mole at pH 8.5. Kd values are observed to decrease as pH further increases. Data points over a range of Np(V) concentrations were collected at pH 8 and fitted to the Langmuir isotherm model for simple adsorption. The Langmuir equation gave an excellent representation of the data. Langmuir parameters were determined to be Ca = 0.032 mole/mole and K = 1.22 × 106 L/mole, indicating the high affinity of hydroxyapatite for Np(V) adsorption.

Original languageEnglish (US)
Pages (from-to)721-727
Number of pages7
JournalRadiochimica Acta
Issue number12
StatePublished - Dec 1 2003


  • Apatite
  • Batch experiments
  • Equilibrium
  • Hydroxyapatite
  • Langmuir isotherm
  • Neptunium
  • Sorption
  • Sorption kinetics

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry


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