Eur. Phys. J. Special Topics 226, 943-955 (2017)
https://doi.org/10.1140/epjst/e2016-60230-8

Regular Article

Evaluation of the solubility constants of the hydrated solid phases in the H₂O-Al₂O₃-SO₃ ternary system

¹ Université de Lyon, Université Claude Bernard Lyon 1, Laboratoire des Multimatériaux et Interfaces, UMR CNRS 5615, 69622 Villeurbanne, France
² Mines ParisTech, 35 Rue Saint Honoré, 77305 Fontainebleau cedex, France
³ AREVA, BU Mines, 1 Place Jean Millier, 92084 Paris la Défense cedex, France

^a e-mail: angelique.teyssier@outlook.com

Received: 18 July 2016
Revised: 7 August 2016
Published online: 18 April 2017

Abstract

During the acid processing of aluminosilicate ores, the precipitation of a solid phase principally consisting of hydrated aluminium hydroxysulfates may be observed. The experimental study of the H₂O-Al₂O₃-SO₃ ternary system at 25 ^∘C and 101 kPa enabled to describe the solid-liquid equilibra and to identify the nature, the composition and the solubility of the solid phases which may form during the acid leaching. To predict the appearance of these aluminium hydroxysulfates in more complex systems, their solubility constants were calculated by modelling the experimental solubility results, using a geochemical reaction modelling software, CHESS. A model for non-ideality correction, based on the B-dot equation, was used as it was suitable for the considered ion concentration range. The solubility constants of three out of four solid phases were calculated: 10^4.08 for jurbanite (Al(SO₄)(OH).5H₂O), 10^28.09 for the solid T (Al₈(SO₄)₅(OH)₁₄.34H₂O) and 10^27.28 for the solid V (Al₁₀(SO₄)₃(OH)₂₄.20H₂O). However the activity correction model was not suitable to determine the solubility constant of alunogen (Al₂(SO₄)₃.15.8H₂O), as the ion concentrations of the mixtures were too high and beyond the allowable limits of the model. Another ionic activity correction model, based on the Pitzer equation for example, must be applied to calculate the solubility constant of alunogen.