Phase Transformations, Ion-Exchange, Adsorption, and Dissolution Processes in Aquatic Fluorapatite Systems
(2009) In Langmuir 25. p.2355-2362- Abstract
- A synthetic fluorapatite was prepared that undergoes a phase transformation generated during a dialysis step. A surface layer with the composition Ca(9)(HPO(4))(2)(PO(4))(4)F(2) is formed, which is suggested to form as one calcium atom is replaced by two protons. A surface complexation model, based upon XPS measurements, potentiometric titration data, batch experiments, and zeta-potential measurements was presented, The CaOH and OPO(3)H(2) Sites were assumed to have similar protolytic properties as in a corresponding nonstoichiometric HAP (Ca(8.4)(HPO(4))(1.6)(PO(4))(4.4)(OH)(0.4)) system. Besides a determination of the solubility product of Ca(9)(HPO(4))(2)(PO(4))(4)F(2), two additional surface complexation reactions were introduced; one... (More)
- A synthetic fluorapatite was prepared that undergoes a phase transformation generated during a dialysis step. A surface layer with the composition Ca(9)(HPO(4))(2)(PO(4))(4)F(2) is formed, which is suggested to form as one calcium atom is replaced by two protons. A surface complexation model, based upon XPS measurements, potentiometric titration data, batch experiments, and zeta-potential measurements was presented, The CaOH and OPO(3)H(2) Sites were assumed to have similar protolytic properties as in a corresponding nonstoichiometric HAP (Ca(8.4)(HPO(4))(1.6)(PO(4))(4.4)(OH)(0.4)) system. Besides a determination of the solubility product of Ca(9)(HPO(4))(2)(PO(4))(4)F(2), two additional surface complexation reactions were introduced; one that accounts for a F/OH ion exchange reaction, resulting in the release of quite high fluoride concentrations (similar to 1 mM) that turned out to be dependent on the surface area of the particles. Furthermore, to explain the lowering of pH(iep) from around 8 in nonstoichiometric HAP suspensions to about 5.7 in FAP suspensions, a reaction that lowers The surface charge due to the readsorption of fluoride ions to the positively charged Ca sites was introduced: CaOH(2)(+) + F(-) -> CaF + H(2)O. The resulting model also agrees with predictions based upon XPS and ATR-FTIR observations claiming the formation of CaF(2)(S) in the most acidic pH range. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/4332381
- author
- Bengtsson, Asa ; Shchukarev, Andrei ; Persson, Per LU and Sjoberg, Staffan
- publishing date
- 2009
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Langmuir
- volume
- 25
- pages
- 2355 - 2362
- publisher
- The American Chemical Society (ACS)
- external identifiers
-
- scopus:63249100904
- pmid:19140703
- ISSN
- 0743-7463
- DOI
- 10.1021/la803137u
- language
- English
- LU publication?
- no
- additional info
- 4
- id
- afd08dc7-7a3c-4cf2-86e4-f01d703900fe (old id 4332381)
- date added to LUP
- 2016-04-01 12:08:20
- date last changed
- 2022-01-26 23:19:42
@article{afd08dc7-7a3c-4cf2-86e4-f01d703900fe,
abstract = {{A synthetic fluorapatite was prepared that undergoes a phase transformation generated during a dialysis step. A surface layer with the composition Ca(9)(HPO(4))(2)(PO(4))(4)F(2) is formed, which is suggested to form as one calcium atom is replaced by two protons. A surface complexation model, based upon XPS measurements, potentiometric titration data, batch experiments, and zeta-potential measurements was presented, The CaOH and OPO(3)H(2) Sites were assumed to have similar protolytic properties as in a corresponding nonstoichiometric HAP (Ca(8.4)(HPO(4))(1.6)(PO(4))(4.4)(OH)(0.4)) system. Besides a determination of the solubility product of Ca(9)(HPO(4))(2)(PO(4))(4)F(2), two additional surface complexation reactions were introduced; one that accounts for a F/OH ion exchange reaction, resulting in the release of quite high fluoride concentrations (similar to 1 mM) that turned out to be dependent on the surface area of the particles. Furthermore, to explain the lowering of pH(iep) from around 8 in nonstoichiometric HAP suspensions to about 5.7 in FAP suspensions, a reaction that lowers The surface charge due to the readsorption of fluoride ions to the positively charged Ca sites was introduced: CaOH(2)(+) + F(-) -> CaF + H(2)O. The resulting model also agrees with predictions based upon XPS and ATR-FTIR observations claiming the formation of CaF(2)(S) in the most acidic pH range.}},
author = {{Bengtsson, Asa and Shchukarev, Andrei and Persson, Per and Sjoberg, Staffan}},
issn = {{0743-7463}},
language = {{eng}},
pages = {{2355--2362}},
publisher = {{The American Chemical Society (ACS)}},
series = {{Langmuir}},
title = {{Phase Transformations, Ion-Exchange, Adsorption, and Dissolution Processes in Aquatic Fluorapatite Systems}},
url = {{http://dx.doi.org/10.1021/la803137u}},
doi = {{10.1021/la803137u}},
volume = {{25}},
year = {{2009}},
}