Solubility of sulphur dioxide in aqueous electrolyte solutions at higher ionic strengths—Chloride and bromide containing systems

The absorption of sulphur dioxide in chloride and bromide containing electrolyte solutions was measured up to ionic strengths of 5 mol/dm3. The thermodynamic equilibrium of the gas phase and the liquid phase was characterized by UV spectroscopy. UV spectra analysis gave strong evidence for SO2X− complexes existing in the solutions. Consequently, these compounds were implemented in the reaction scheme for absorption.For thermodynamic modelling the activity coefficient model of Pitzer was used. The Pitzer parameters of some important ion pairs and, as a very effective extension, the Sechenov's constant for dissolved molecular sulphur dioxide were fitted to laboratory data. This work demonstrates that fitting Sechenov's constant improves the model performance very much. With the extended model we find a good agreement between model prediction and experimental data over the entire range of concentrations.