In the realm of environmental protection, the urgency to address emerging contaminants (ECs) has intensified. A beacon of promise in this endeavor is the biochar-based catalysts (BCs)-activated persulfate (PS) process, specifically utilizing singlet oxygen (1O2). This process not only navigates the challenges posed by complex environmental backgrounds but also amplifies mass transfer for efficient ECs removal.

This comprehensive review dissects the intricate mechanisms behind BCs, focusing on their oxygen functional group (OFG), defect structure, and persistent free radicals (PFRs). These elements activate PS, propelling the generation of 1O2. Heteroatom doping emerges as a critical factor, enhancing electronic conductivity and creating additional reactive sites for bolstering 1O2 production.

The generation of 1O2 in BCs/PS processes hinges on SO5•- and O2•, as revealed through meticulous electron structure examinations. To accurately gauge the contribution of 1O2, the review scrutinizes current detection methods, highlighting the efficacy of quenching experiments, electron paramagnetic resonance (EPR) spectra, solvent exchange, and probe methods. Utilizing multiple detection approaches mitigates the risk of false positives inherent in relying on a single method.

Notably, Density Functional Theory (DFT) calculations predict the reactivity of 1O2 with per- and polyfluoroalkyl substances (PFAS), hinting at potential inefficiency in degrading PFAS based on the predictive model.

As we journey forward, this review underscores the need for continued research to enhance the development of 1O2-activated advanced oxidation processes (AOPs) for robust ECs removal, marking a significant stride toward a cleaner and healthier environment.