Dissolved concentration and lifetime of ozone ultrafine bubbles

Abstract Ozone has a broad potential application scope, including sterilization, water purification, and wastewater treatment. However, these applications are limited by its instability and short lifetime. Ozone ultrafine bubbles (UFBs) were observed to increase the dissolved concentration and lifetime of ozone; however, the mechanism involved has not yet been comprehensively analyzed. This study aims to experimentally elucidate the effect of ozone conversion to UFBs on ozone concentration and lifetime. We analyzed the two methods primarily used for ozone UFB generators: ozone direct dissolution and ozone pressure mixing and dissolution. We measured the dissolved ozone concentration and lifetime of the ozone UFBs. Furthermore, we measured the particle size distribution, from which we calculated the specific surface area per unit volume. We experimentally demonstrated that the ozone direct dissolution method achieved an increase in the concentration of dissolved ozone due to the increase in the ozone transfer as the specific surface area increased. However, the lifetime achieved was considered to be insufficient for use as a disinfectant solution. We used the ozone pressure mixing and dissolution method to achieve the concentration lifetime required for use as a disinfectant, with a flow rate of 40 l min −1 when the number of bubbles was proportional to the flow rate. This represents a considerable advancement in the use of ozone UFB water as a portable disinfectant.