Physical Properties of Ozone

Performance and Regeneration Issues of Resin in Ion Exchange Reactions

Ozone is an unstable gas with a pungent, characteristic odor, and its molecular structure is shown in the figure. It can be photochemically synthesized within the Earth's stratosphere, but exists at only extremely low concentrations at Earth's surface.

1.1 General Physical Properties

At room temperature, ozone is a blue gas; however, the blue color is not very pronounced at room temperature unless it is a relatively thick gas layer.

1.2 Solubility of Ozone

Ozone is slightly soluble in water. At standard pressure and temperature (STP), its solubility is 13 times greater than that of oxygen and 25 times greater than that of air. By passing ozone into distilled water, the solubility of ozone in water at different temperatures and pressures can be measured. Figure 2-2 shows the relationship between the solubility of pure ozone in water and temperature at a pressure of 1 atm. As shown in Figure 2-2, at 0℃, the solubility of pure ozone in water reaches 2.858 × 10⁻² mol/L (1372 mg/L). Like other gases, the solubility of ozone in water conforms to Henry's Law, which states that at a given temperature, the mass of any gas dissolved in a known liquid is directly proportional to the partial pressure of that gas acting on the liquid. The Henry's constant is only a function of temperature and is independent of concentration.

C = KH P (1-1)

Where C – solubility of ozone in water, mg/L;

P – partial pressure of ozone in ozonated air, kPa;

KH – Henry's constant, mg/(L·kPa).

From equation (1-1), it is known that since ozonated air is mostly used in actual production, its ozone partial pressure is very small, therefore the solubility of ozone is much lower than the data in Table 1-3. For example, in ozone generators using air as raw material, ozonated air contains only 0.6% to 1.2% ozone (by volume). According to the gas equation and Dalton's law of partial pressures, the partial pressure of ozone is only 0.6% to 1.2% of the pressure of ozonated air. Therefore, when the water temperature is 25°C, adding this ozonated air to water results in an ozone solubility of only (0.625 to 1.458) × 10⁻⁴ mol/L (3 to 7 mg/L). In general water treatment, ozone concentrations are low, so its solubility in water is not significant. At low concentrations, the solubility of ozone in water basically satisfies Henry's Law.