Constructing nanoconfined spaces in persulfate oxidation processes for efficient degradation of emerging contaminants: Structures, mechanisms, and challenges

Persulfate-based advanced oxidation processes (PS-AOPs) are widely recognized for their potential in treating emerging contaminants (ECs) in aquatic environments. However, the complex composition of water matrices often triggers side reactions that hinder effective ECs removal, complicating the practical application of AOPs. Recently, nanoconfined space-driven AOPs have emerged as a focal point in addressing these challenges. Nevertheless, the rational design of nanoconfined microreactors and the primary mechanisms governing PSAOPs remain topics of debate. Therefore, this review critically examines recent advancements in nanoconfinement within PS-AOPs, aiming to provide insights for future research endeavors. Specifically, the review introduces a classification methodology based on the dimensions of nanoconfined spaces and the synthesis techniques of microreactors. Subsequently, it focuses on the comprehensive analysis and elucidation of nanoconfinement-mediated catalytic mechanisms, including the identification of active sites, evaluation of hollow space contributions, and exploration of reactive species generation. Through constructing nanoconfined spaces in PS-AOPs, the removal of ECs can effectively mitigate metal ion leaching while minimizing the influence of the water matrix, thereby enhancing catalyst recovery efficiency. Nonetheless, challenges persist in realizing cost-effective, efficient, robust, and sustainable nanoconfinement-driven PS-AOPs.