From Fundamentals to Mechanisms: Peroxyacetic acid catalysts in emerging pollutant degradation

Abstract

In the peroxyacetic acid advanced oxidation process (PAA/AOPs), organic pollutants are decomposed by radical and non-radical pathways via metal, non-metal, and metal-non-metal composite catalysts activated by PAA; the pollutant degradation efficiencies are affected by pH, H 2 O 2 concentration, catalyst and PAA dosage, and the water matrix. Density functional theory (DFT) revealed the influence of electronic structure (e.g., bond lengths, highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) energy levels, and electrostatic potentials) on reaction pathways and efficiencies. This review aims to present researchers with a comprehensive and concise overview of the potential application of PAA/AOPs technology in addressing emerging environmental pollutants, with the ultimate goal of expediting its practical implementation. The growing research interest in advanced oxidation technologies has led to a focus on using reactive peroxyacetic acid (PAA), a strong oxidising agent capable of degrading emerging contaminants through both radical (e.g., hydroxyl, organic radicals) and non-radical (e.g., singlet oxygen, high-valent metal oxides) pathways, offering high resistance to environmental disturbances. Current PAA research faces significant challenges, particularly in unravelling complex degradation mechanisms to optimise catalytic efficiency and minimise environmental impacts. Previous reviews lack a focused exploration of specific oxidisers like PAA and provide less detailed mechanistic insights, practical application strategies, and environmental considerations compared to a more targeted, in-depth analysis. This study systematically investigates the role of catalyst-assisted activation of PAA in the degradation of emerging pollutants within advanced oxidation processes (AOPs). We focus on analysing the physicochemical properties of PAA and its activation mechanisms, with particular emphasis on the effects of different catalysts on the reactivity of PAA and the degradation mechanisms. Furthermore, we summarise the key factors influencing the degradation efficiency of pollutants, assess the applicability of the PAA system in environmental remediation, and explore the application of density functional theory (DFT) calculations in revealing interactions between catalysts and PAA, as well as in elucidating catalytic mechanisms. Finally, we discuss challenges and future directions for PAA in pollutant management, aiming to establish a theoretical foundation and support the development of environmentally friendly materials for pollution remediation.

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