Graphene/Fe@N-doped carbon hybrid derived from spent MOF adsorbent as efficient persulfate activator for degradation of tetracycline hydrochloride

Metal-organic frameworks (MOF) have shown significant potential as efficient adsorbing materials for treating antibiotic wastewater. However, little attention has been paid to the proper disposal of dangerous antibiotic-polluted MOF adsorbents. In this study, tetracycline hydrochloride (TCH)-saturated MIL-100(Fe) as spent MOF adsorbent was converted into graphene/[email protected] carbon hybrid (FexNC) by one-step pyrolysis to activate persulfate (PS) for TCH degradation. The existence of the TCH adsorbate on the MIL-100(Fe) precursor significantly affected the physicochemical properties of the obtained [email protected] product, which can be responsible for the higher catalytic activity of FexNC than the pristine MIL-100(Fe)-derived. FexNC was shown to have wide pH applicability (2–10) and the kinetics of TCH (96.2 mg/L) degradation was 0.042 min−1 with 0.3 g/L FexNC, 1 mM PS and pH 6. During TCH degradation, the carbon matrix and doped nitrogen in FexNC were more important than the iron species. Because of the inaccessibility of iron species encapsulated by carbon, 1O2 and O2•— were the dominant reactive oxygen species in FexNC/PS, with less contribution from SO4•— and •OH. Importantly, interfacial electron transfer was revealed to dominate the TCH oxidation process. This study provides not only a practical way for the disposal and reuse of waste MOF materials but also new ideas for the design of MOF-derived heteroatoms doping [email protected] hybrids.