Green synthesis of Fe-based material using tea polyphenols and its application as a heterogeneous Fenton-like catalyst for the degradation of lincomycin

Iron-based catalysts (GFe0.5) were successfully prepared from tea polyphenols (TP) and ferric trichloride and used as a heterogeneous Fenton-like catalyst for the degradation of lincomycin (LCM). The results showed that a GFe0.5 dosage of 0.01 g/L could completely degrade a 20 mg/L concentration of LCM in 90 min, and assessment of the toxicity to luminous bacteria showed that the GFe0.5/H₂O₂ system effectively reduced the toxicity risk posed by this pollutant. The results of transmission electron microscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and other characterisations showed that the synthetic material had a triangular structure similar to that of nonacarbonyldiiron, with Fe²⁺, Fe³⁺ and organic groups attached to the triangular structure's surface. That is, the present environment-friendly synthesis produces an Fe-based material resembling a mixture of nonacarbonyldiiron and ferrous chloride. Free-radical capture and electron spin resonance experiments confirmed that ·OH was the main active free radical in the degradation mechanism of the iron-based material. Cyclic experiments, inductively coupled plasma and XRD characterisation of the materials after the reaction showed that the loss of free iron was the main reason for the decrease of activity. The free iron in the Fe-based material becomes bound during the reaction, which effectively avoids the excessive consumption of Fe²⁺ in the prophase of the Fenton-like reaction, and is the key to both the efficient Fenton-like catalytic ability of GFe0.5, and to preventing the production of iron sludge.