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 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 degrees 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.

Automated summary

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. Results showed that increasing the pyrolysis temperature enlarged the specific surface area and pore volume of the carbocatalysts, and CuxO@PHC700 exhibited a faster degradation rate for TC compared to other carbocatalysts. After regeneration, the spent CuxO@PHC700 still had promising catalytic activity for TC degradation.