Ultrasound-enhanced advanced oxidation processes: mechanisms and applications for treating emerging organic contaminants in water

Rapid industrialization worldwide has led to the accumulation of diverse environmental pollutants in water, air, and soil, posing significant threats to the earth's ecological balance and making environmental remediation an urgent priority. Among the various remediation techniques, ultrasound-assisted advanced oxidation processes (AOPs) have emerged as a promising approach, leveraging the unique effects of acoustic cavitation to enhance pollutant degradation in water. By generating reactive oxygen species (e.g., hydroxyl radicals) through bubble collapse and improving mass transfer, ultrasound amplifies the efficiency of AOPs using catalysts, photo-mediated processes, and chemical reagents. This review synthesizes advancements in ultrasound-assisted AOPs over the past decades, including mechanism of the reactions and novel hybrid systems, offering a global perspective on their potential for large-scale environmental remediation. We systematically explore the mechanisms of ultrasound enhancement, the types of AOPs integrated with ultrasound, and their applications in degrading persistent pollutants. Additionally, we analyze the underlying synergistic effects and discuss current challenges, and future directions for hybrid technologies based on ultrasound for efficient water treatment.