Enhanced photocatalytic degradation of caffeine using Co-Zn/Al₂O₃ nanocomposite

This work focuses on the synthesis and characterization of photocatalytic activity of Co-Zn/Al₂O₃ nanocomposite obtained by calcination of Co-loaded Zn/aluminum layered double hydroxide by wet impregnation method. The catalyst was characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), BET and UV-DRS. The evaluation of catalytic activity was investigated for the degradation of emerging pharmaceutical pollutant caffeine in aqueous solutions under UV irradiation. The process parameters were optimized for the maximum removal of caffeine. A maximum caffeine removal of 92% was obtained with the optimal conditions at the catalytic dosage of 0.5 g/L, contact time of 50 min, initial concentration of 50 mg/L, and pH of 9.5. The batch experimental data coincide well with the pseudo first order kinetic model, the rate constant of 0.012 min^-1, with the R² value of 0.875-0.938. The regeneration study reveals that the catalyst has high stability and maximum removal efficiency. Hence, the synthesized nanocatalyst is considered a potential photo catalyst for removing the pharmaceutical pollutant caffeine from aqueous solutions.