Solubility of I2 in a HI–H2O system: Measurement and modelling.

The sulfur–iodine (S–I) thermochemical cycle for hydrogen production can be widely applied. The solubility of I 2 in complex and non-ideal HI–H 2 O–I 2 (HI x) ternary systems is critical for the phase separation behaviour and Bunsen reactor design. A new apparatus was established to measure the I 2 solubility using potentiometric titration. Fifty-two experimental data points of the I 2 solubility in the HI–H 2 O system were obtained at temperatures ranging from 293 K to 353 K, and the molar fraction of HI ranged from 7.69% to 15.74%. A new solubility model of I 2 in the HI–H 2 O system was developed using the solid-liquid phase equilibrium theory and a local composition model suitable for electrolyte systems (ELECNRTL). The complex effect of I 2 and I− promoting the dissolution of I 2 in the HI x system was also verified, in which the short-range interaction was dominant over the long-range interaction. The parameters of the model were determined by using the experimental data obtained in this work, where the average relative deviation (ARD) of the model was 2.73%. The model was also simultaneously validated using available experimental data, with which the calculated results were in agreement. This model satisfies the application requirements of the engineering design. • A high precision I 2 solubility measurement system for HI x solution system is established. • The I 2 solubility in HI x system is measured in the range of T = 293–353 K and x HI = 7.69–15.74%. • A high accuracy solubility model is established. • The change of internal forces in the HI x system is analysed. [ABSTRACT FROM AUTHOR]