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Issue 25, 2018
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A thermodynamic description for water, hydrogen fluoride and hydrogen dissolutions in cryolite-base molten salts

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Abstract

This paper presents a quantitative thermodynamic description for water, hydrogen fluoride and hydrogen dissolutions in cryolite-base molten salts, which is of technological importance to the Hall–Héroult electrolytic aluminum extraction cell. The Modified Quasichemical Model in the Quadruplet Approximation (MQMQA), as used to treat a large variety of molten salt systems, was adopted to thermodynamically describe the present liquid phase; all solid solutions were modeled using the Compound Energy Formalism (CEF); the gas phase was thermodynamically treated as an ideal mixture of all possible species. The model parameters were mainly obtained by critical evaluations and optimizations of thermodynamic and phase equilibrium data available from relative experimental measurements and theoretical predictions (first-principles calculations and empirical estimations) for the lower-order subsystems. These optimized model parameters were thereafter merged within the Kohler/Toop interpolation scheme, facilitating the prediction of gas solubility (H2O, HF and H2) in multicomponent cryolite-base molten salts using the FactSage thermochemical software. Several interesting diagrams were finally obtained in order to provide useful information for the industrial partners dedicated to the Hall–Héroult electrolytic aluminum production or other molten-salt technologies (the purification process and electroslag refining).

Graphical abstract: A thermodynamic description for water, hydrogen fluoride and hydrogen dissolutions in cryolite-base molten salts

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Publication details

The article was received on 27 Apr 2018, accepted on 29 May 2018 and first published on 01 Jun 2018


Article type: Paper
DOI: 10.1039/C8CP02678E
Citation: Phys. Chem. Chem. Phys., 2018,20, 17324-17341
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    A thermodynamic description for water, hydrogen fluoride and hydrogen dissolutions in cryolite-base molten salts

    K. Wang and P. Chartrand, Phys. Chem. Chem. Phys., 2018, 20, 17324
    DOI: 10.1039/C8CP02678E

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