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Publication Detail
The dissolution kinetics and apparent solubility of natural apatite in closed reactors at temperatures from 5 to 50 °C and pH from 1 to 6
  • Publication Type:
    Journal article
  • Publication Sub Type:
    Journal Article
  • Authors:
    Harouiya N, Chaïrat C, Köhler SJ, Gout R, Oelkers EH
  • Publication date:
    15/10/2007
  • Pagination:
    554, 568
  • Journal:
    Chemical Geology
  • Volume:
    244
  • Issue:
    3-4
  • Status:
    Published
  • Print ISSN:
    0009-2541
Abstract
The apparent solubility and dissolution rates of natural apatite were measured in closed-system reactors as a function of temperature from 5 to 50 °C and pH from 1 to 6. The temporal release rates of Ca, P, and F during the experiments are approximately consistent with stoichiometric dissolution in all experiments. One advantage of closed-system experiments is that they allow determination of reactive fluid evolution and dissolution rates at far-from to near-to equilibrium conditions. Surface area normalized apatite dissolution rates, r, obtained in all experiments are consistent withr = AA aH+n exp (EA / RT) (1 - exp (- A / σ RT))where AA stands for a rate constant equal to 4 × 10- 3 mol/cm2/s, aH+ denotes the activity of the aqueous H+, n designates a reaction order equal to 0.6, EA symbolizes an activation energy equal to 11.0 kcal/mol, A refers to the chemical affinity of the dissolving apatite, σ stands for Temkin's average stoichiometric number equal to 5; R designates the gas constant, and T represents absolute temperature. Logarithms of apparent equilibrium constants obtained from experiments performed at 3 ≤ pH ≤ 5.6 for the apatite dissolution reactionCa5(PO4)3F + 3H+ = 5Ca2+ + 3HPO42- + F-are found to be - 29.5 ± 0.6, - 29.4 ± 0.9 and - 29.9 ± 1.3 at 5, 25, and 50 °C, respectively. © 2007 Elsevier B.V. All rights reserved.
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