Molecular oxygen activation by atomic Fe-moieties on MnO₂ for enhanced remediation of parachlormetaxylenol wastewater

Abstract

The spin-forbidden effect and high bond energy of molecular oxygen (O₂) pose a fundamental challenge for its activation in wastewater treatment. We address this by constructing an atomically dispersed Fe-Mn dual-site catalyst (Fe_0.1-Mn-350), which overcomes the sluggish O₂ kinetics of monometallic oxides and the aqueous instability of conventional single-atom catalysts. This catalyst enables complete degradation of 20 mg/L parachlormetaxylenol (PCMX) within 15 minutes, with a reaction rate (0.2205 min⁻¹) 25 times greater than MnO₂ and surpassing benchmark catalysts. Experimental and theoretical analyses reveal that the preferential side-on O₂ adsorption at Fe sites of Fe_0.1-Mn-350 significantly reduces activation barriers by 38% (versus Fe-CNTs by 15%, Co-MnO₂ by 25%), and triggers a dual-pathway mechanism involving both radical (^•OH, O₂^•−) and non-radical (¹O₂, Fe(IV)) species. Crucially, the Fe_0.1-Mn-350/O₂ system demonstrates robust practicality, maintaining 98% efficiency in real hospital wastewater, stable operation in a 12-h continuous-flow reactor, and a low operational cost of 0.28 USD/m³. The technology’s environmental sustainability is further validated by a remarkable 80% recovery of zebrafish embryo hatchability and a 93% reduction in developmental toxicity. This work provides a green and economically viable strategy for the destructive treatment of persistent halogenated contaminants in water.

Graphical abstract

Keywords

Atomic Fe-Mn catalyst / O₂ adsorption and activation / Advanced oxidation processes / Toxicity assessment / Wastewater remediation

Highlight

	● An atomically dispersed Fe-Mn dual-active-site catalyst was synthesized.
	● It achieved 25-fold higher O2 activation rate than MnO2 for PCMX degradation.
	● Preferential side-on O2 adsorption reduces activation barrier by 38%.
	● The system operated stably for 12 h in a continuous-flow reactor.
	● It reduced treatment cost to 0.28 USD/m3 and detoxified wastewater effectively.

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