Upcycling Textile White Mud to Fabricate MIL-125-Derived Amorphous TiO2@C: Effective Electrocatalyst for Cathodic Reduction of Antibiotics

Abstract

Cathodic reduction is a green and promising remediation strategy for reducing the antibacterial activity of antibiotic contaminants and increasing their biodegradability. However, the lack of cost-effective electrocatalysts has restricted its application. In this study, we upcycled textile white mud by separating 1,4-dicarboxybenzene (BDC) and fabricating MIL-125(Ti)-derived amorphous TiO2@C (TiO2@C-W) as a functional electrocatalyst. The separated BDC from white mud shows lower crystallinity than BDC chemicals, but the resulting TiO2@C-W features a much higher degree of oxygen vacancies and a 25-fold higher specific surface area than that of TiO2@C derived from BDC chemicals. With florfenicol (FLO) as a probe, TiO2@C-W exhibits similar cathodic reductive activity (0.017 min−1) as commercial Pd(3 wt.%)/C (0.018 min−1) does, which was 1.4 and 3.7 times higher than that of oxygen vacancy-engineered TiO2 and TiO2@C, respectively. The as-fabricated TiO2@C-W could not easily remove FLO via the oxygen reduction reaction-based pathway with the applied bias for cathodic reduction. Though the activity of TiO2@C-W undergoes a slight decline with continuous running, more than 80% of 20 mg L−1 FLO can still be reduced in the eighth run. Water chemistry studies suggest that a lower initial solution pH boosts the cathodic reduction process, while common co-existing anions such as Cl−, NO3−, HCO3−, and SO32− show a limited negative impact. Finally, TiO2@C-W shows reductive activity against several representative antibiotics, including nitrofurazone, metronidazole, and levofloxacin, clarifying its potential scope of application for antibiotics (e.g., molecules with structures like furan rings, nitro groups, and halogens). This study couples the upcycling of textile white mud with the remediation of antibiotics by developing functional electrocatalysts, and offers new insights for converting wastes from the printing and dyeing industry into value-added products.