Strategies and mechanisms for the regulation of reactive oxygen species in advanced oxidation process

<p indent="0mm">With the advancement of technology and the progress of industrialization, water pollution has become a severe global issue that humanity must confront. Organic pollution in the environment is highly complex, having evolved from single-source contamination to composite pollution, with the affected areas continuously expanding. Additionally, organic pollutants have the ability to bioaccumulate, which allows them to magnify their carcinogenic, teratogenic, and mutagenic effects through the food chain. In current research on water pollutants, emerging contaminants (ECs) have been identified as posing risks to both the ecological environment and human health due to their characteristics, such as biotoxicity, environmental persistence, and bioaccumulation. Moreover, their presence has not yet been incorporated into environmental management. Therefore, to protect human health and the public environment, it is imperative to continue researching and developing efficient methods for the removal of ECs, such as advanced oxidation processes (AOPs). Advanced oxidation processes (AOPs) have been proven to degrade various emerging pollutants by generating reactive oxygen species (ROS) with high oxidation potential. Current research mainly focuses on modifying the properties of catalysts to improve the degradation efficiency of emerging pollutants in AOPs. However, our previous works have found and proved the important role of molecular structure on affecting the degradation efficiencies and dominant ROS of contaminants in AOPs. Therefore, purposefully generating a large amount of a specific ROS based on the molecular structure characterization results of pollutants in actual wastewater is expected to significantly reduce engineering trial-and-error costs and improve the utilization efficiency of oxidants and reactive species. Based on our previous research results, this review summarizes the precise regulation methods and generating mechanisms of radicals, singlet oxygen and high-valent metals in the current advanced oxidation system. Firstly, the pivotal regulatory effects of non-metallic sulfides and natural polyphenols on the type and concentration of radicals are investigated. Furthermore, the role of single-atom catalysts in modulating the adsorption configurations of oxygen atoms within oxidants, the influence of catalysts on activation energy barriers, the synergistic interactions of dual active sites, the oxygen adsorption facilitated by oxygen vacancies, and the structural regulation of carbon materials in selectively generating singlet ¹O₂ are systematically reviewed. Finally, the regulatory effects of pH, the cooperative effects of chelating agents, anions, and catalyst structures on the selective generation of high-valent metals are comprehensively assessed. We also propose suggestions and prospects for current research on the ROS regulation, aiming to provide a reference for achieving precise oxidation of emerging pollutants. In subsequent research, the regulatory effects and mechanisms of multiple environmental factors, like pH and the co-existing anions, on radicals generation and transformation need to be comprehensively evaluated. Additionally, it is crucial to conduct an in-depth mechanisms analysis of the role of non-metal species on regulating ROS and reveal the corresponding key factors. Simultaneous degradation of multiple organic pollutants is more complex than treating a single pollutant, therefore the principle of multi free radicals combination regulation based on molecular structure characteristics to achieve efficient oxidation of various organic pollutants needs to be explored and verified in practice. For the treatment of real wastewater with complex components, deep learning can be employed to extract molecular structural features from the selective attack information of ROS toward target pollutants. Additionally, exploring the predictive performance of traditional machine learning models (ML) and ensemble models for the oxidative degradation of complex components in real wastewater, will enable the development of processes with precise oxidation functions. These efforts will lead to the formulation of technological solutions for the effective detoxification and environmental risks decrease of real wastewater with complex components.