Synergistic adsorption and photocatalytic performance of CuO–CdS composites for the removal of doxycycline

The presence of antibiotic residues in water causes severe environmental pollution and health risks for the population. This study reports the synthesis, characterization, and application of CuO, CdS, and CuO/CdS composites with different molar ratios (2:1, 1:1, and 1:2) for the removal of doxycycline (DOX) from aqueous media. The composites were prepared via a co-precipitation method, and the prepared nanocomposite was characterized using several techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), UV–Vis diffuse reflectance spectra (DRS), BET (Brunauer–Emmett–Teller) surface area analysis, and zeta potential measurements. Both adsorption and photocatalysis are used for the removal of doxycycline. Among the prepared materials, the CuO: CdS (1:1) composite exhibited the highest adsorption efficiency and the highest photocatalysis efficiency in sunlight irradiation. Adsorption kinetics followed the pseudo-second-order model, and thermodynamic analysis indicated a spontaneous and endothermic process. The enhanced efficiency is attributed to the formation of an S-scheme heterojunction which promotes efficient charge separation and suppresses electron–hole recombination.