Enhanced microwave-assisted Fenton-like reactions for water treatment via conduction loss modulation of CuOx/MSN catalysts.

Abstract

Integrating microwave (MW) irradiation into advanced oxidation processes (AOPs) has emerged as a promising strategy for enhancing catalytic reactivity. MW can selectively deliver energy to catalysts, generating localized hot spots and promoting interfacial electron transfer that enhance radical generation and oxidation kinetics. This work demonstrates an energy-dissipation-guided catalyst design for MW-assisted Fenton-like water treatment at a commercially relevant frequency of 2.45 GHz. Catalyst electronic energy dissipation, with conduction loss as a key component, was suggested to be a governing factor in reaction performance. CuO_x (CuO/Cu₂O) nanoparticles were immobilized on porous silica to promote conduction-loss-dominated MW energy dissipation. Structural stability was improved by suppressing aggregation and strengthening copper-silica interactions. Pore-size tuning showed that smaller pores further reduced Cu leaching. This trend is consistent with stronger anchoring of CuO_x via surface -OH and -NH₂ interactions near pore walls. The optimized catalyst (MSN-N1-Cu2%) achieved high degradation performance at neutral pH with only 2 wt% Cu and exhibited ultra-low Cu leaching in each cycle (≤0.028 mg/L) with stable operation over repeated cycles. It further showed broad applicability, completely removing eight representative organic pollutants (aromatic compounds, synthetic dyes, and an organophosphorus compound) within 4 min. In addition, the recalcitrant contaminants PFOA and PFOS exhibited removal efficiencies of 30% and 62%, respectively, within 10 min. These results provide practical guidance for energy-efficient MW-based water treatment and motivate frequency-catalyst matching to direct MW energy toward catalytic activation rather than bulk solution heating.