Thermodynamic Research of S-H₂O System in Sodium Aluminate Solution

Abstract:

There are many different types of valence of sufur in aluminate sodium solution during the process of the bauxite dissolution, which mainly including S^2-, S₂^2-, S, S₂O₃^2-, SO₃^2-, SO₄^2- and it may have an effect on the mineral dissolution process. Therefore, it is necessary that the thermodynamic properties of S-H₂O system were investigated in sodium aluminate solution. In this paper, the reactions between different valence states of sulfur and lye (with or without oxygen participation) were studied in sodium aluminate solution. The thermodynamic software Factsage 7.0 was carried out to calculate the standard reaction Gibbs free energy (ΔG_T^θ). The results showed that S^2- and SO₄^2- are the most stability in terms of the autoreactive reaction of different valence states at 298-573 K, and that the stability of different valence states of sufur order is “S₂^2- >(S₂O₃^2-, SO₃^2-) >S”. At 523 K, SO₃^2- is more stable than S₂O₃^2-. On the other hand, the low-valent sulfur was more likely to be oxidized into SO₄^2- under oxidizing conditions at 298-573 K. Besides, it was also found that S₂^2- is most susceptible to oxidation because of the lowest stability. Finally, the stability of the other valence states of sulfur under oxidizing conditions order is “SO₃^2- >S₂O₃^2- >S^2- >S”.

• Periodical: Key Engineering Materials (Volume 730)
• Pages: 272-281
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.730.272
• Online since: February 2017
• Authors: Li Cong Zheng, Zhan Wei Liu, Ke Qiang Xie*, Wen Hui Ma, Kui Xian Wei
• Keywords: High Sulfur Bauxite, S-H₂O System, Sodium Aluminate Solution, Thermodynamics, ΔG_T^θ

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