Thermodynamic modeling of oxygen dissolvation in water

Abstract

Traditional methods for determining the solubility of oxygen in water are considered. Their advantages and disadvantages are shown. It is noted that especially great difficulties arise when measuring SO in a real chemical process, where the temperature and components of the system, as well as their ratios change over time. The new method for determining the solubility of oxygen based on thermodynamic calculation of the equilibrium phase and component composition of the oxygen-water system by minimizing the isobaric-isothermal potential of Gibbs using the software package "Selector" is proposed. The model is based on the exact equation of state for calculating the chemical potential of the vapor phase and the chemical potential of the liquid phase. The result is mathematical laws of dissolution of oxygen in water depending on a wide range of temperatures and pressures, which allows significantly facilitating and expanding the range of reliable control of the parameters of chemical-technological processes. The thermodynamic model allows calculations to be performed both in pure water and in acid and salt solutions, as well as taking into account the vapor phase and without it. The equation of Henry’s constant is given for oxygen and air from temperatures in the range of 273...373 K and pressures up to 10 atm., which allows determining any intermediate values. To do this, it is necessary to substitute in the equation the current data of temperature and pressure, which are easily measurable. It is shown that within these ranges the deviation from the experimental values is minimal 1%, which allows using of the presented equations in technological calculations. The value of the temperature, at which the minimum solubility of oxygen is being observed, for pure oxygen is determined Tmin = 370.5K, for air Tmin = 370.3 K., the value of enthalpy changes sign.