Nd‐ZnO Catalysts for Photocatalytic Degradation of Metronidazole

ABSTRACT

Conventional water treatment processes are unable to effectively degrade metronidazole (MNZ), leading to its accumulation in wastewater and posing a serious threat to aquatic environments and human health. Photocatalysis offers an environmentally friendly and stable method for removing organic pollutants. However, zinc oxide (ZnO) has a large bandgap, limiting its light absorption to the ultraviolet region. To overcome this limitation, this study synthesized a series of Nd‐ZnO catalysts with different neodymium molar ratios (0.2%, 0.5%, 0.7%, and 1.0%) via a one‐step hydrothermal method. UV–vis spectroscopy confirmed that the bandgap decreased from 3.22 to 3.18 eV after Nd doping, while the photocurrent response was enhanced and the e ⁻ –h ⁺ recombination rate was reduced. When the catalyst dosage was 10 mg and the initial MNZ concentration was 10 mg·L ⁻¹ , the degradation efficiency of 0.5 mol% Nd‐ZnO reached 94.3% after 180 min of irradiation with a 400 W metal halide lamp. First‐order reaction kinetics fitting yielded a reaction rate constant of 0.013 min ⁻¹ , which is 1.7 times that of pure ZnO; after five cycles, the degradation efficiency remained as high as 87.7%. It provides an effective photocatalyst for the treatment of antibiotic wastewater and offers important insights into the performance of rare‐earth‐modified ZnO.