Synergistic mechanism of ultrasonic cavitation and advanced oxidation: Free radical path optimization and advanced treatment of industrial wastewater

In industrial wastewater, emerging pollutants with environmental persistence, bioaccumulation and ecological toxicity (polycyclic aromatic hydrocarbons (PAHs), perfluorinated compounds (PFAC) and drug residues) pose a serious threat to ecological security and human health. Advanced oxidation technologies (AOPs) have become the core means of wastewater treatment by achieving deep mineralization of organic matter through free radical-mediated oxidation reactions. However, the application of single AOPs is limited by bottlenecks such as low mass transfer efficiency, catalyst deactivation, by-product generation and high energy consumption. Ultrasound technology significantly improves the efficiency of AOPs by enhancing mass transfer, activating oxidants and catalyst regeneration through a synergistic physicochemical mechanism that breaks through the limitations of conventional technologies. This review firstly summarizes the current research status and limitations of single AOPs. Then, ultrasonic oxidation technology seen as an entry point, it systematically explores the cross-scale synergistic mechanism and industrial application potential of ultrasonic synergistic advanced oxidation technologies (US-AOPs). This reveals the coupled synergistic pathways of ultrasonic cavitation effect with Fenton, ozone, electrochemical and photocatalytic technologies and the mechanism of regulating the generation of by-products. Secondly, the economics and stability of US-AOPs in industrialization are demonstrated through industrial cases. The challenges faced by US-APOs are analysed in terms of cost, scalability, and operational robustness. It is found that the integration of interdisciplinary emerging technologies is expected to promote the transformation of wastewater treatment in US-AOPs towards a high efficiency, low carbon and intelligent, which provides innovative solutions for near-zero discharge and resource utilisation of industrial wastewater.