The use of ozone gas started about a century ago. Ozone has been used to purify water polluted by microorganisms. The chemistry of ozone in aqueous solutions is complex and the direct reaction with molecular ozone and the indirect reaction with radicals generated when ozone is dissolved in water are considered for the process of water treatment with ozone.
The authors calculated the first principles of the reaction between molecular ozone and water vapour, but no first principles study of the decomposition of ozone in water has been carried out.
Choe Un Hwa, a researcher at the Faculty of Online Education, has conducted a study to select the size of ozone bubbles used for water treatment using ozone microbubbles, considering the ozonolysis characteristics in water.
She quantitatively calculated the decomposition of ozone in water using the density functional method (DFT/6-31G*). Among the four possible reactions between O3 and H2O in gas and water, the possibility of obtaining H2O2+O2 is relatively high.
Considering that H2O2 and O2 are products of indirect reactions by ozone with OH- as an initiator and the rate of indirect reactions is very fast, the size of ozone bubbles used for water treatment can be as large as a micron size, which can increase the solubility of ozone gas in aqueous solution and improve the ozonation efficiency.
You can find more information in her paper “Ozone Micro Bubble Treatment: What is the Size of Ozone Bubble Suitable for Water Treatment?” in “Proceedings of KUTIC-2025”.