Zero-Valent Iron-Supported Magnetic Hydrochar Derived from Kitchen Waste for Efficient Fenton-like Degradation of Tetracycline Hydrochloride

In this study, hydrochars loaded with iron species (Fe@HTC and Fe@HTC−T) were prepared by chemical co-precipitation and tubular furnace sintering treatment to develop efficient and sustainable catalysts for antibiotic wastewater treatment, addressing key challenges in sustainable environmental management. The characterization results indicated that iron species loaded on the hydrochars changed from Fe 3 O 4 to FeO and then to metallic Fe with the pyrolysis temperature increased from 400 °C to 800 °C. The results of the characterization revealed a phase transition of iron species, confirming the temperature-dependent evolution of catalytic activity. The catalytic performance of the hydrochar composites was evaluated for tetracycline hydrochloride (TC–HCl) degradation via a Fenton-like process. Under optimal conditions (0.2 g/L TC–HCl, 0.1 g/L catalyst, 0.1 mM H 2 O 2 , pH = 6.86), Fe@HTC−T demonstrated excellent catalytic activity with a removal efficiency of 91.2%. Moreover, Fe@HTC−T exhibited superior stability and low iron leaching rates, attributed to the protective role of the hydrochar matrix. Mechanism research suggested that hydroxyl radicals (•OH) played a dominant role in the degradation process. This study demonstrates the potential of utilizing low-cost and renewable hydrochar materials derived from biomass waste to address industrial challenges in treating high-concentration antibiotic wastewater, offering a sustainable and cost-effective solution with broad applications in environmental remediation.