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Comment on “The experimental determination of hydromagnesite precipitation rates at 22.5– 75°C” by Berninger, U.-N., Jordan, G., Schott, J. and Oelkers, E.H.

Published online by Cambridge University Press:  02 January 2018

Yongliang Xiong*
Affiliation:
Sandia National Laboratories (SNL), Carlsbad Programs Group, 4100 National Parks Highway, Carlsbad, NM 88220, USA
Ziya Cetiner
Affiliation:
Department of Geological Engineering, Canakkale Onsekiz Mart University, Canakkale 17020, Turkey
*

Abstract

In this work, we tested the equilibrium constant of hydromagnesite [Mg5(CO3)4(OH)2·4H2O] at 22.5°C proposed by Berninger et al. (2014) against field observations. By field observations we mean that analytical resultsoriginate from samples in the natural environment. In our test, we calculated saturation states of hydromagnesite, using the equilibrium constant of hydromagnesite at 22.5°C from Berninger et al., for the carbonate lakes in Qinghai-Xizang Plateau in China and for Salda Lake in Turkey,based on the hydrochemical data from literature. The predictions based on this equilibrium constant indicate that all of these lakes are strongly under-saturated with respect to hydromagnesite. However, hydromagnesite has been shown to form in all of these lakes. Therefore, this equilibrium constant is clearly in direct contradiction with field observations, leading to the conclusion that the equilibrium constant of hydromagnesite of Berninger et al. (2014) is not suitable for geochemical modelling.

Type
Article Commentary
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2017

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