Synthesis and Evaluation of the Photocatalytic Performance of a ZnO-Graphite Composite for the Degradation of Ciprofloxacin under Sunlight

Abstract

Pharmaceutical pollutants, particularly antibiotics such as ciprofloxacin, have emerged as persistent environmental contaminants due to their widespread use and incomplete removal by conventional wastewater treatment methods. Heterogeneous photocatalysis using semiconductor-based materials has gained attention as a sustainable and efficient approach for degrading such pollutants under solar irradiation. This study aims to evaluate the photocatalytic degradation of ciprofloxacin using a ZnO–graphite nanoparticle composite to enhance degradation efficiency and reduce electron–hole recombination. Zinc oxide-graphite nanoparticles were synthesized by the hydrothermal method. Several characterization tests including XRD, IR, SEM, and UV-visible spectroscopy through absorbance were used to characterize nanoparticles. The results revealed nanoparticles exhibiting hexagonal structure of zinc oxide and mixed of zinc oxide and graphite. IR confirmed by several absorption bands characteristic of zinc oxide and graphite. The ZnO-Gr nanocomposites exhibit a mixture of rods and flat spherical particles. Also observed the band gap energy of the composites decreased, from 3.29 eV to 2.97 eV, 2.96 eV, and 2.91 eV for ZnO-Gr (1%), ZnO-Gr (3%), ZnO-Gr (5%), and ZnO-Gr (7%), respectively. The photocatalytic activities of these materials under sunlight showed degradation rates of ciprofloxacin up to 66%, 70% and 75%, and 78% and 80% for the ZnO, ZnO-Gr (1%), ZnO-Gr (5%), ZnO-Gr (7%) and ZnO-Gr (3%) catalysts, respectively. The effectiveness of ZnO-Gr (3%) catalysts increased up to 100% degradation rate of ciprofloxacin at optimal conditions such as 70 mg of catalyst, pH 7.7 with concentration of 10 mg/L. The results on the stability of photocatalyst showed good stability after four activity cycles.