Photocatalytic degradation of an antibiotic in aqueous solution using ZnO

This study investigates the photocatalytic degradation of the antibiotic flumequine in aqueous solution using ZnO synthesized via a simple and environmentally friendly route. The synthesized photocatalyst exhibited a hexagonal wurtzite crystal structure with an average crystallite size of 34.4 nm, a specific surface area of 6 m² g^-1, and an optical band gap of 3.19 eV. Batch photocatalytic experiments were carried out to evaluate the effects of catalyst dosage (0.5-2.0 g L^-1), initial flumequine concentration (5-25 mg L^-1), and solution pH (3-10). The highest degradation efficiency (99%) was achieved at pH ≈ 6.2 using an initial flumequine concentration of 10 mg L^-1 and a ZnO dosage of 1.5 g L^-1. The degradation kinetics followed an apparent pseudo-first-order model, with the rate constant decreasing from 0.013 to 0.0013 min^-1 as the initial flumequine concentration increased from 5 to 25 mg L^-1. The concentration-dependent kinetic behavior was further described using the Langmuir-Hinshelwood model, yielding an intrinsic surface reaction rate constant of 0.1005 mg L^-1 min^-1 and a Langmuir adsorption constant of 0.5814 L mg^-1. Total organic carbon analysis revealed a maximum mineralization efficiency of 39.4%, indicating the formation of intermediate products during photocatalytic degradation. Reusability experiments demonstrated that ZnO retained satisfactory photocatalytic activity after five successive cycles. These findings demonstrate that pristine ZnO is an efficient and stable photocatalyst for the removal of flumequine from aqueous media and highlight its potential for wastewater treatment applications.