Nanoconfined Catalysts Enable Tunable Radical and Nonradical Ozonation for Selective Treatment of Saline Industrial Wastewaters

Abstract

Selective control of ozone activation pathways remains challenging, particularly in saline industrial wastewaters, where chloride-rich matrices suppress radical oxidation and reduce mineralization efficiency. Here, we show that carbon-shell nanoconfinement of FeCo alloy nanoparticles enables material-defined tuning between radical and nonradical catalytic ozonation pathways. By controlling carbon-shell thickness and nitrogen speciation, we modulate interfacial electron transfer, ozone activation, and oxidation selectivity. Thin carbon shells create electron-rich metal–carbon interfaces that promote radical-driven ozonation and enhance TOC mineralization. In contrast, thicker shells enriched in pyridinic N favor the formation of surface oxygenated intermediates and promote a surface-mediated nonradical oxidation pathway that resists chloride quenching, delivering more than 3-fold higher COD removal in high-salinity real wastewater than the radical-dominant catalyst. Scavenger experiments, electron paramagnetic resonance spectroscopy, electrochemical measurements, in situ FTIR and Raman spectroscopy, and density functional theory calculations collectively show how metal–carbon interactions and N speciation govern ozone adsorption, electron-transfer kinetics, and pathway selection. These results establish carbon-shell nanoconfinement as a general material strategy for tuning catalytic ozonation selectivity in complex industrial wastewaters.