Role of Cu_xO‑Anchored Pyrolyzed Hydrochars on H₂O₂‑Activated Degradation of Tetracycline: Effects of Pyrolysis Temperature and pH

This study investigated the effects of pyrolysis temperature on the physicochemical properties of pyrolyzed hydrochars (PHCs) and H₂O₂-catalyzed tetracycline (TC) degradation in a combined treatment with PHC and Cu_xO@PHCs. The effects of pH on TC degradation by Cu_xO@PHCs were also evaluated in the presence of H₂O₂ and compared with that by Cu_xO@GAC. To analyze their physicochemical changes due to the oxidant, the carbocatalysts were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) analysis, and Fourier transform infrared (FTIR) spectroscopy. To sustain its cost-effectiveness, spent Cu_xO@PHC700 was regenerated using NaOH. Based on the characterization results, increasing the pyrolysis temperature from 300 to 700 °C enlarged their specific surface area and pore volume. The X-ray diffraction (XRD) analysis revealed that the Cu anchored in the carbocatalyst existed as Cu₂O/CuO. The H₂O₂-catalyzed degradation by Cu_xO@PHC700 (0.231 min^–1) was faster than that by Cu_xO@PHC500 (0.107 min^–1), Cu_xO@PHC300 (0.013 min^–1), and Cu_xO@GAC (0.041 min^–1) (p ≤ 0.05; analysis of variance (ANOVA)). The maximum TC removal was achieved by Cu_xO@PHC700 at pH 6 due to the H-bonding and Cu-bridging effects between the Cu-loaded carbocatalyst and TC molecules in solutions. Treated effluents could meet the maximum discharge limit standard of 1 mg/L set by the local legislation. After the first regeneration, the spent Cu_xO@PHC700 could attain about 96% of TC degradation. This implies that the saturated carbocatalyst still had promising catalytic activity for reuse. Overall, Cu_xO@PHC is a cost-effective option for TC removal from contaminated water.