Controlling power loss of ozonation via ultrasonic cavitation in strongly alkaline and high-salt solutions: Mass transfer and numerical simulation.

By combining experimental analysis and numerical simulation, the enhancement of ozone mass transfer and the dynamics of cavitation bubbles via ultrasonic cavitation technology in highly alkaline and high-salinity Bayer liquor are systematically investigated. Experimental results indicate that ultrasonic irradiation significantly improves parameters such as ozone utilization efficiency and the volumetric mass transfer coefficient, while simultaneously achieving a substantial reduction in ozone consumption. Optimal ozone mass transfer performance is achieved under the conditions of an ultrasonic power of 80 W, an oxygen flow rate of 60 L/h, and a reaction temperature of 55 °C. Consequently, ultrasonic cavitation effectively reduces ozone consumption for organic degradation by 33.62%, corresponding to an operating cost reduction of 2360.48 CNY per ton of TOC degraded. Furthermore, cavitation bubble dynamics are simulated. The results show that the cavitation intensity reaches its maximum under the following conditions: a polytropic exponent of 1.57, an ultrasonic frequency of 25 kHz, an ultrasonic amplitude of 125 kPa, a reaction temperature of 55 °C, an ambient pressure of 101 kPa, and an initial bubble radius of 6 μm. Most importantly, a fundamental correlation between the calculated sound intensity per unit area and the applied ultrasonic power is established. This correlation holds significant reference value for the standardization and optimization of ultrasonic parameters in ozone‑based advanced oxidation processes using similar reactor systems.