Original scientific paper

Thermodynamic effects of temperature during roasting of chromite for sodium chromate salts formation

M. J. Mvita ; Department of Metallurgy, School of Mining, Metallurgy and Chemical Engineering, Faculty of Engineering and the Built Environment, University of Johannesburg, South Africa *
N. G. Zulu ; Department of Metallurgy, School of Mining, Metallurgy and Chemical Engineering, Faculty of Engineering and the Built Environment, University of Johannesburg, South Africa
B. Thethwayo ; Department of Metallurgy, School of Mining, Metallurgy and Chemical Engineering, Faculty of Engineering and the Built Environment, University of Johannesburg, South Africa
S. Makhamisa ; Institute for Intelligent Systems, University of Johannesburg, South Africa

* Corresponding author.

Abstract

This paper aims to assess the potential effects of roasting temperature on the formation of sodium chromate (Na₂CrO₄). To perform this task, chromite samples were complexed with NaCl at temperatures ranging from 900 °C to 1 200 °C in the presence of excess oxygen. These experimental conditions were set and assessed based on the predicted phase transformations using Facstage as a prediction tool. The scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) have revealed the roasting behaviour of chromite to be governed by a fully reacted outside layer and an unreacted core. As per the x-ray diffraction (XRD) results, at lower temperature settings, mineral phases such as hematite and chromium oxide reported as an indication of predicted oxidation of chromite. The key results indicate that the addition of NaCl reduces the equilibrium temperature, thereby fully decomposing the stable and refractory spinel structure of chromite at 1 200 °C.

Keywords

thermodynamics, Na₂CrO₄, roasting, equilibrium, x- ray research

Hrčak ID:

312316

URI

https://hrcak.srce.hr/312316

Publication date:

1.4.2024.

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