Preparation of sludge-based biochar loaded with ferromanganese and its removal mechanism of tetracycline hydrochloride

To remove the serious contamination caused by tetracycline hydrochloride, this paper uses the method of impregnation followed by pyrolysis to prepare ferromanganese-loaded sludge-based biochar and investigate its effectiveness in removing tetracycline hydrochloride. The material was characterized by field emission SEM, FTIR, and X-ray diffraction analysis. The possible reaction mechanisms involved in the removal of tetracycline were deduced based on the determination of Mn 2+ during the reaction process and XPS characterization of materials before and after the reaction, and analysis of degradation intermediates and reaction pathways during tetracycline hydrochloride degradation was discussed. The results showed that the highest removal rate of 90.71% was achieved at a Fe-to-Mn ratio of 2:1 for the Fe-to-Mn-loaded sludge-based biochar. XPS characterization before and after the reaction showed that the valence state of Fe did not change significantly and was stable, while Mn 4+ partially changed to Mn 2+ and a redox reaction occurred. The changes in Mn 2+ concentration during the reaction showed that the degradation of tetracycline hydrochloride was mainly dominated by MnO 2 . The LC–MS analysis revealed eight intermediates in the degradation of tetracycline, and two possible reaction pathways existed.