Cu2O/Waste Tire-Derived Activated Carbon Catalysts Applied in Persulfate Oxidation Processes for Antibiotic Remediation in Aqueous Matrices

Conventional wastewater treatment processes are not specifically designed to efficiently eliminate pharmaceutical contaminants such as metronidazole (MTZ), highlighting the need for effective advanced oxidation processes (AOPs). Heterogeneous persulfate activation represents a promising approach for degrading recalcitrant organic pollutants. In this study, Cu-loaded activated tire char (ATC-Cu) catalysts were synthesized for the first time using different ATC/Cu weight percentages (2.5, 5, and 10% w/w) and evaluated for MTZ degradation through peroxymonosulfate (PMS) and peroxydisulfate (PDS) activation. XRD analysis confirmed the formation of the Cu2O crystal phase, while textural characterization revealed a meso–macroporous structure. Among the investigated systems, ATC-10 w/w Cu/PMS exhibited the highest catalytic performance, achieving complete MTZ degradation within 10 min, with an apparent kinetic rate constant of k = 0.357 min−1. The optimum PMS and catalyst dosages were 250 and 400 mg/L, respectively. Mechanistic investigations identified SO4•− as the dominant reactive species, indicating a predominantly radical oxidation pathway, whereas •OH played a secondary role. The influence of inorganic ions and natural organic matter was also evaluated, revealing limited inhibition of MTZ degradation. Overall, ATC-Cu catalysts combine efficient persulfate activation with waste-tire valorization, demonstrating their potential as sustainable catalysts for pharmaceutical-contaminated wastewater treatment.