Catalyst-Assisted H2O2 Systems for Bacterial Disinfection of Wastewater: From UV/Visible Synergy to Electro-/Photo-Fenton Pathways

Hydrogen peroxide assisted advanced oxidation processes are pivotal for next-generation water treatment, yet progress is slowed by fragmented evidence, non-uniform metrics, and scale-up blind spots. This review consolidates mechanisms and performance across homogeneous and heterogeneous Fenton and photo-Fenton catalysts, including Prussian blue analogues, MOF-derived oxides and carbons, and spinels, as well as peroxidase-like nanozymes, carbon co-catalysts, and photolytic UV/H₂O₂ and visible or solar routes. We harmonize conditions through a benchmarking scheme that combines energy per order, oxidant utilization efficiency, photon-normalized kinetics, mineralization selectivity, and durability with leaching tests. Kinetic mapping pinpoints limitations involving H₂O₂ activation versus self-scavenging, metal redox cycling, mass transfer, and pH or matrix effects from bicarbonate, halides, and natural organic matter. We address by-product control and safety through staged oxidant delivery, matrix-aware pretreatment, and in situ H₂O₂ generation in electro-Fenton systems. Screening techno-economic and life-cycle indicators delineates regimes where UV/H₂O₂ is favored, where solar photo-Fenton narrows the energy gap, and where photoelectrochemical architectures extend durability. From these insights we propose design rules for materials, reactors, and operation, and we outline reporting standards that couple photon accounting, stability protocols, and transparent cost and impact metrics to enable fair comparisons and faster translation.