Enhanced peracetic acid activation by phosphorylated zero-valent iron-copper foam for levofloxacin removal from sewage sludge: Electron transfer regulation and functional synergy

A self-supporting phosphorylated zero-valent iron–copper foam (P-ZVI@CF) was constructed for efficient and selective levofloxacin (LEV) removal from sludge, via the overcoming of electron-transfer limitations and enabling peracetic acid activation. Appearance of abundant nano-cracks and electronic modulation on ZVI, as well as the generation of built-in electric field on the Cu–Fe heterogeneous interface, synergistically accelerated the directional electron migration, Fe⁰ corrosion, and Fe(II) regeneration. Subsequently, as high as an 81.5% reduction of LEV was achieved within 60 min under the operational condition of 0.4 g/L PAA, 6.0 g/L P-ZVI@CF, and neutral pH. Moreover, the P-ZVI@CF+PAA system maintained a stable and continuous LEV removal, with a maximum removal rate of 95.3%, during a continuous 10-day operation. The distinct “division-of-labor” reactive oxidative species (ROS) mechanism played a key role in LEV degradation, in which high oxidative ·OH and Fe(IV) primarily disrupted the extracellular polymeric substance (EPS) matrix and facilitated pollutant releasing, then those released LEV could be selectively degraded by organic radicals (RO·). This functional differentiation of ROS provided a new strategy for the application of advanced oxidation for sludge treatment. Besides contaminant removal, a much higher methane productivity of 134.6 mL/g VS would be also achieved for the subsequential anaerobic digestion, as compared to control groups. The selective and efficient LEV degradation, combined with the enhancement of anaerobic methanogenesis provided a feasible strategy for green treatment of emerging pollutants in sludge.