## 1 Introduction
[14] proposed a PC-SAFT model to predict the SO\({}_{2}\) solubility in water, covering a valid _T-P_ range of 263.15-393.15 K and 10-300 bar, which can accurately predict the SO\({}_{2}\) solubility in water above 10 bar and 273.15 K, but at lower temperatures and pressures, it cannot accurately calculate the SO\({}_{2}\) solubility. [PERSON] et al. [15] used the Monte Carlo (MC) molecular simulation technique to predict the vapor-liquid and liquid-liquid equilibria including the solubility data of SO\({}_{2}\)-H\({}_{2}\)O mixture in the temperature range of 293-393 K and pressures up to 25 bar, and the results from the MC simulation are in agreement with experimental data at liquid-vapor and liquid-liquid equilibria. As mentioned above, the models of SO\({}_{2}\) solubility in multi-ion electrolyte solutions are still lacking, and most of them either have lower accuracy or have a limited temperature-pressure-salinity range. Therefore, it is necessary to develop an accurate model for the \begin{table}
\begin{tabular}{l l l l l} \hline
**References** & **Salt** & **_T (K)_ & **_P (bar)_** & **_m\({}_{\text{salt}}\) (mol/kg)_** \\ \hline [PERSON] et al. [6] & H\({}_{2}\)SO\({}_{4}\), Na\({}_{2}\)SO\({}_{4}\) & 298–323 & 10\({}^{-4}\)–0.1 & 0-saturation \\ [PERSON] et al. [7] & NaCl, NH\({}_{4}\)Cl & 313–393 & 0–37 & 0–6 \\ [PERSON] et al. [8] & seawater & 278.15–318.15 & 0.976 & unstated \\ [PERSON] [9] & water & 293–333 & 0–0.01 * & 0 \\ [PERSON] et al. [10] & HCl, NaCl, HBr, NaBr & 298 & 1.015 & 0–4.613 \\ [PERSON] et al. [11] & water & 298–313 & 0.2–3.6 & 0 \\ [PERSON] et al. [12] & water, NaCl & 313–393 & 0–40 & 0–6 \\ [PERSON] et al. [13] & seawater, brine & 298.15–323.15 & unstated & 0–1 \\ [PERSON] et al. [14] & water & 263.15–393.15 & 10–300 & 0 \\ [PERSON] et al. [15] & water & 293–393 & 0–25 & 0 \\ \hline \end{tabular}  
* Notes: _T, P and m\({}_{\text{salt}}\) denote the temperature, pressure and molality of salt, respectively.* is the partial pressure of SO\({}_{2}\).  
\end{table} 
Table 1: Thermodynamic models for calculating SO\({}_{2}\) solubilities in pure water, aqueous salt solutions or seawater. solubility of SO\({}_{2}\) in multi-ion electrolyte solutions. In this work, we first review experimental data of SO\({}_{2}\) solubility in pure water and multi-ion electrolyte solutions. Then an accurate thermodynamic model is developed to predict the SO\({}_{2}\) solubility in water and multi-ion electrolyte solutions by the activity-fugacity relationship at vapor-liquid equilibria. Finally, the applications of the model are briefly discussed. Review of Experimental Data for SO\({}_{2}\) Solubility in Pure Water and Aqueous Electrolyte Solutions  
In this article, the solubility data of four different systems (SO\({}_{2}\)-H\({}_{2}\)O, SO\({}_{2}\)-NaCl-H\({}_{2}\)O, SO\({}_{2}\)-KCl-H\({}_{2}\)O and SO\({}_{2}\)-Na\({}_{2}\)SO\({}_{4}\)-H\({}_{2}\)O) have been found and compiled as shown in Table 2, where the information of each data set is provided, including the temperature, pressure, salinity and total number of data points. SO\({}_{2}\) solubility in water represents the total amount of SO\({}_{2}\) species dissolved in water, including SO\({}_{2}\)(aq), HSO\({}_{3}^{-}\) and SO\({}_{3}^{2-}\).