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Dehydration behaviour of the Ca(SO4,HPO4).2H2O solid solution

Published online by Cambridge University Press:  05 July 2018

A. J. Pinto ,
A. Jimenez  and
M. Prieto
A. J. Pinto*
Affiliation:
Departamento de Geología, Universidad de Oviedo, C/ Jesús Arias de Velasco s/n, 33005 Oviedo, Spain
A. Jimenez
Affiliation:
Departamento de Geología, Universidad de Oviedo, C/ Jesús Arias de Velasco s/n, 33005 Oviedo, Spain
M. Prieto
Affiliation:
Departamento de Geología, Universidad de Oviedo, C/ Jesús Arias de Velasco s/n, 33005 Oviedo, Spain
*
*E-mail: [email protected]
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Abstract

Gypsum (CaSO4·2H2O) and brushite (CaHPO4·2H2O) are minerals with similar structures, despite not being isostructural. They both belong to the monoclinic system, but crystallize in different space groups. It is known that, to some extent, phosphate and sulphate groups can substitute for each other within the structure of these minerals. In the present work, the dehydration behaviour of experimentally produced Ca(SO4,HPO4)·2H2O solid solutions is assessed from thermogravimetrical (TG and DTG) and differential scanning calorimetry (DSC) analyses. For the applied experimental conditions it was not possible to obtain homogenous precipitates with compositions within 0.27 < XBr < 0.53, where XBr is the brushite mole fraction. The results reveal that the dehydration behaviour of solid solutions with compositions within the 0 < XBr < 0.27 interval tend to approach the dehydration process of pure gypsum. On the other hand, solid solutions with compositions within 0.53 < XBr < 1 involve higher dehydration temperatures than the brushite end-member, in a two-step process.

Keywords

gypsumbrushitesolid solutionsdehydrationTGDTG
Type
Research Article
Information
Mineralogical Magazine , Volume 72 , Issue 1 , February 2008 , pp. 277 - 281
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2008

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References

Andara, A., Heasman, D., Fernandez-Gonzalez, A. and Prieto, M. (2005) Characterization and crystallization of Ba(SO4, SeO4) solid solution. Crystal Growth and Design, 5, 1371–1378.CrossRefGoogle Scholar
Aslanian, S., Stoilova, D. and Petrova, R. (1980) Isodimorphous substitution in the calcium sulphate —calcium hydrogen phosphate — water system. Zeitschrift für anorganische und allgemeine Chemie, 465, 209–220.Google Scholar
Fatu, D. (2001) Kinetics of gypsum dehydration. Journal of Thermal Analysis and Calorimetry, 65, 213.CrossRefGoogle Scholar
Fernández-Gonzalez, A., Andara, A., Alia, J.M. and Prieto, M. (2006) Miscibility in the CaSO4-2H2O-CaSeO4-2H2O system: Implications for the crystallisation and dehydration behaviour. Chemical Geology, 225, 256–265.CrossRefGoogle Scholar
Heijnen, W.M.M. and Hartman, P. (1991) Structural morphology of gypsum (CaSO4.2H2O), brushite (CaHPO4.2H2O) and pharmacolite (CaHAsO4.2H2O). Journal of Crystal Growth, 108, 290–300.CrossRefGoogle Scholar
Jordan, G. and Astilleros, J.M. (2006) In situ HAFM study of the thermal dehydration on gypsum (010) surfaces. American Mineralogist, 91, 619–627.CrossRefGoogle Scholar
Mclntosh, A.O. and Jablonski, W.L. (1956) X-ray powder patterns of the calcium phosphates. Analytical Chemistry, 28, 1424–1427.Google Scholar
Pinto, A., Jimenez, A. and Prieto, M. (2008) Mixing properties and crystallization behaviour of the Ca(SO4,HPO4)-2H2O solid solution from aqueous solutions, (in prep.).CrossRefGoogle Scholar
Putnis, A., Winkler, B. and Fernandez-Diaz, L. (1990) In situ IR spectroscopic and thermogravimetric study of the mechanism of dehydration of gypsum. Mineralogical Magazine, 54, 123–128.CrossRefGoogle Scholar
Rinaudo, C, Lanfranco, A.M. and Franchini-Angela, M. (1994) The system CaHPO4-2H2O-CaSO4-2H2O: crystallization from calcium phosphate solutions in the presence of SO4∼. Journal of Crystal Growth, 142, 184–192.CrossRefGoogle Scholar
Rinaudo, C, Lanfranco, A.M. and Boistelle, R. (1996) The gypsum-brushite system: crystallization from solutions poisoned by phosphate ions. Journal of Crystal Growth, 158, 316–321.CrossRefGoogle Scholar
Sakae, T., Nagata, H. and Sudo, T. (1978) The crystal structure of synthetic calcium phosphate-sulphate hydrate, Ca2HPO4SO4-4H2O and its relation to brushite and gypsum. American Mineralogist, 63, 520–527.Google Scholar
Schofield, P.F., Knight, K.S., van der Houwen, J.A.M. and Valsami-Jones, E. (2004) The role of hydrogen bonding in the thermal expansion and dehydration of brushite. Physics and Chemistry of Minerals, 31, 606–624.CrossRefGoogle Scholar
Tortet, L., Gavarri, J.R., Nihoul G., Fulconis, J.M. and Rouquerol, F. (1996) Dehydration and electrochemical activity of calcium hydrogenophosphate dihydrate. European Journal of Solid State and Inorganic Chemistry, 33, 1199–1210.Google Scholar