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

Abstract

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 CuxO@PHCs. The effects of pH on TC degradation by CuxO@PHCs were also evaluated in the presence of H2O2 and compared with that by CuxO@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 CuxO@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 CuxO@PHC700 (0.231 min–1) was faster than that by CuxO@PHC500 (0.107 min–1), CuxO@PHC300 (0.013 min–1), and CuxO@GAC (0.041 min–1) (p ≤ 0.05; analysis of variance (ANOVA)). The maximum TC removal was achieved by CuxO@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 CuxO@PHC700 could attain about 96% of TC degradation. This implies that the saturated carbocatalyst still had promising catalytic activity for reuse. Overall, CuxO@PHC is a cost-effective option for TC removal from contaminated water.