Natural polyphenol-mediated oxidative polymerization and degradation of emerging contaminants

Tremendous advances have been made in enhancing the abatement of emerging contaminants (ECs), especially with the assistance of ubiquitous and eco-friendly natural polyphenols (NPs). Current research shows that NPs allow the efficient elimination of ECs through oxidative polymerization and degradation pathways in advanced oxidation processes (AOPs). Therefore, an in-depth understanding of these processes is essential for further advanced environmental applications. This work provides a comprehensive overview on the latest advancements in polymerization and degradation of ECs in various NP-mediated AOPs, including Fenton, persulfate, peracetic acid, and other oxidation processes. The review outlines the occurrence of fundamental properties of commonly used NPs, and then comprehensively elaborates the associated mechanisms of NP-mediated enhancement on AOPs. NPs can prevent metal ions from precipitating, enhance the reactivity of NP − M (M represents metals) complex, and accelerate both homogeneous and surface Mn+1/Mn+ redox cycling, thereby promoting reactive species generation and contaminant degradation. Direct interactions between NPs and oxidants produce phenoxyl radicals and quinones, driving ECs transformation through radical polymerization or nucleophilic addition. Moreover, this work discusses the advantages and application potential of NP-mediated AOPs in real environmental scenarios. The merits of NP-mediated oxidation technology include wide pH suitability, robust anti-interference capacity, minimal harmful residues, and diversified application scenarios. Last but not least, the key knowledge gaps and future research needs of NP-mediated AOPs are highlighted. This review provides guidance on the application of NP-mediated AOPs to address real-world environmental issues.