Role of CuxO-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 H 2 O 2 -catalyzed tetracycline (TC) degradation in a combined treatment with PHC and Cu x O@PHCs. The effects of pH on TC degradation by Cu x O@PHCs were also evaluated in the presence of H 2 O 2 and compared with that by Cu x O@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 x O@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 Cu 2 O/CuO. The H 2 O 2 -catalyzed degradation by Cu x O@PHC700 (0.231 min –1 ) was faster than that by Cu x O@PHC500 (0.107 min –1 ), Cu x O@PHC300 (0.013 min –1 ), and Cu x O@GAC (0.041 min –1 ) ( p ≤ 0.05; analysis of variance (ANOVA)). The maximum TC removal was achieved by Cu x O@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 x O@PHC700 could attain about 96% of TC degradation. This implies that the saturated carbocatalyst still had promising catalytic activity for reuse. Overall, Cu x O@PHC is a cost-effective option for TC removal from contaminated water.