Magnetic hydrochar from the extract and residue of herbal medicines for adsorption and Fenton reaction

Abstract

Residues of herbs medicines are potential resources to prepare hydrochar. However, problems such as limited adsorption capacity and difficulty in recovery restrict the application of residues. Here, Ferrous sulfate heptahydrate (FeSO4·H2O) was used to load Fe3O4 to prepare Fe3O4-modified hydrochar (Fe-CBC). Herbal extract (silymarin) was used to prepare functionalized hydrochar (Sil-Fe-CBC) for the first time by using the residue of clematis. Sil-Fe-CBC was used to remove methylene blue (MB) and tetracycline (TC) from water. The MB adsorption quantity was increased to 124.7 mg/g within 30 min, and the removal was increased to 84.26%. The TC removal was achieved approximately 91% in 120 min at an optimum pH of 3, an H2O2 dosage of 0.4 mL, a Sil-Fe-CBC dosage of 0.6 g/L, and a temperature of 30 °C. The FTIR spectra and XRD spectrum studies confirm that the form of ·OH is linked to Fe2+ in the catalysis process via the reduction of silymarin. Silymarin functionalization is a new approach to promote the efficiency of Fenton. Herbal medicine residues are potential raw materials in hydrochar preparation, and the extracts can improve hydrochars' performance.