Highlights Ultrasonic cavitation is recorded by high-speed camera and hydrophone in a gas-expanded liquid system. Content of CO 2 has an important influence on evolution of bubble cloud. Cavitation intensity depends on ultrasonic power and gas content. The combination of ultrasound and gas-expanded liquid system greatly promotes mass transfer.

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Highlights High excess enthalpy is crucial for cavitation bubbles in high x-CO 2 mixtures. Surface tension is the key factor in low x-CO 2 mixtures. Greater critical ultrasonic power is needed for higher pressure of mixtures. Maximum value of transient cavitation intensity is greater in higher x-CO 2 mixtures. Combination of compression and substitution effects cavitation in CO 2 -expanded DMF.