Unraveling the critical role of iron-enriched sludge hydrochar in mediating the Fenton-like oxidation of triclosan

The traditional Fenton system is subject to the low efficiency of the Fe(III)/Fe(II) conversion cycle, with sig-nificant attempts made to improve the oxidation efficiency by overcoming this hurdle. In support of this goal, iron-enriched sludge-derived hydrochar was prepared as a high-efficiency catalyst by one-step hydrothermal carbonization and its performance and mechanisms in mediating the oxidation of triclosan were explored in the present study. The hydrochar prepared at 240 degrees C for 4 h (HC240-4) had the highest removal of triclosan (97.0%). The removal of triclosan in the HC240-4/H2O2 system was greater than 90% in both acidic and near-neutral environments and remained as high as 83.5% after three cycles, indicating the broad pH applicability and great recycling stability of sludge-derived hydrochar in Fenton-like systems. H2O2 was activated by both persistent free radicals (PFRs; 19.7%) and iron (80.3%). The binding of Fe(III) to carboxyl decreased the electron transfer energy from H2O2 to Fe(III), making its degradation efficiency 2.6 times greater than that of the con-ventional Fenton reaction. The study provides a way for iron-enriched sludge utilization and reveals a role for hydrochar in promoting iron cycling and electron transfer in the Fenton reaction.

Automated summary

In this study, iron-enriched sludge-derived hydrochar was prepared as a high-efficiency catalyst for the oxidation of triclosan. The hydrochar exhibited excellent removal efficiency of triclosan, with a broad pH applicability and great recycling stability. The activation of H2O2 was achieved by both persistent free radicals and iron, making the degradation efficiency significantly higher than that of the conventional Fenton reaction. These findings provide insights into the utilization of iron-enriched sludge and the role of hydrochar in promoting iron cycling and electron transfer in the Fenton reaction.