Degradation of rhodamine B using a heterogeneous Fenton-like reaction driven by nano-zero-valent iron loaded on biochar prepared in the presence of ultrasonic irradiation

The biochar-supported nanoscale zero-valent iron (nZVI@BC) was synthesized in the presence of ultrasonic irradiation and applied in the heterogeneous Fenton-like degradation of rhodamine B (RhB). The property changes in the nZVI@BC synthesized in the presence and absence of ultrasonic irradiation were characterized, which confirmed that the ultrasonically irradiated catalyst had a better dispersion and higher electron transfer rate, showing better catalytic performance for RhB degradation. The effects of the catalyst dosage, pH value and H₂O₂ concentration were investigated, and it was found that under the conditions of initial pH = 3, H₂O₂ concentration = 15 mmol L^-1, catalyst dosage = 1.5 g L^-1 and 298 K, the RhB removal efficiency of nZVI@BC(ultrasonic irradiation) was 97.7%. Furthermore, the classical second-order kinetic model showed better fitting results, suggesting that the RhB degradation was primarily controlled by a chemical reaction, and the activation energy was calculated to be 77.8 kJ mol^-1. Based on quenching experiments and electron paramagnetic resonance spectra, free radicals ˙OH and ˙O₂ ^- were detected, and ˙OH was found to be the main free radical in RhB degradation. After three cycles of catalyst reuse, its removal efficiency was still more than 70%. This work provides a new route for using ultrasonic irradiation to improve the catalyst performance in Fenton-like systems.