Sonochemistry in environmental remediation. 2. Heterogeneous sonophotocatalytic oxidation processes for the treatment of pollutants in water.

Recent advances in advanced oxidation technologies for applications in environmental remediation involve the use of acoustic cavitation. Cavitation is the formation, growth, and implosive collapse of gas- or vapor-filled microbubbles formed from acoustical wave-induced compression/ rarefaction in a body of liquid. Cavitation is effective in treating most liquid-phase pollutants but it is highly energy intensive and not economical or practically feasible when used alone. One of the most interesting topics in the recent advances in environmental sonochemistry is the intensification of the ultrasonic degradation process by coupling ultrasound with other types of energy, chemical oxidants, or photocataysts. In Part II of this series, a critical review of the applications of ultrasound in environmental remediation focusing on the simultaneous or hybrid use of ultrasonic irradiation and photocatalysis in aqueous solutions, namely, sonophotocatalytic oxidation processes, is presented.