Radical assisted iron impregnation on preparing sewage sludge derived Fe/carbon as highly stable catalyst for heterogeneous Fenton reaction

Radical induced sewage sludge pretreatment has been developed to enhance sludge stabilization and dewater-ability. Except for anaerobic digestion, the reutilization of the oxidized sludge residuals is still a challenging issue for wastewater treatment plant. In the view of favorable role in sludge disintegration, the pretreated sludge precursors, which was obtained by sequential radical oxidation and iron impregnation, was carbonized to prepare the carbon encapsulated Fe nanoparticles (Fe NPs), which could then behave as highly stable and active heterogeneous Fenton-like catalyst to degrade Black-T. By contrast, the carbonized products derived from direct iron impregnation were also prepared as a control method. The effect of H2O2/Fe2+ on zeta potential, particle size, morphology and texture structure of the pretreated sludge precursors and their corresponding influence on the carbonized materials were systematically evaluated. Results showed that radicals' activation could facilitate the iron impregnation on sewage sludge by rupturing the microbial aggregate and making them more accessible to subsequent microbial fragments. Compared to direct iron impregnation, the carbonized products featured much higher iron insertion rate and the uniformly dispersed Fe NPs encapsulated into porous carbons, which in turn enables catalysts exhibiting more efficient catalytic activity in continuous heterogeneous Fenton-like degradation and resistance to metal leaching.