Degradation of tetracycline in synthesized wastewater using immobilized TiO2 on rotating corrugated aluminum drum

The failure to remove tetracycline (TC) in most conventional wastewater treatment systems results in the discharge and accumulation of TC in the environment, which in turn, increases the potential for developing TC-resistance in naturally occurring microorganisms. Thus, there is a need to explore other processes that can enhance TC degradation during wastewater treatment. In this study, we investigated the adsorption and photocatalytic degradation of TC using titanium dioxide (TiO₂) immobilized onto an aluminum (Al) drum reactor. The TC concentrations were measured using UV-Vis spectrophotometry and liquid chromatography with mass spectrometry. TC removal was achieved by partially immersing the drum reactor in synthetic wastewater, and then rotating the drum to expose the adhered aqueous film to overhead UV lamps. Two-level full factorial design was used to investigate the effects of TiO₂ immobilization on Al drum, UV photon absorption and drum corrugation on TC removal efficiency. Results show that the adsorption of TC to Al³⁺ sites enhances the mass transfer of TC from the bulk aqueous solution to the reactor drum. The adsorption rate of TC is higher in Al-TiO₂ than in the Al alone likely due to the increased number of adsorption sites in Al-TiO₂. The continuous photon absorption by the Al decreases the TC removal rate, which might be due to the excitation of Al site-TC bonds leading to TC desorption. On the other hand, photon absorption by TiO₂ promotes photocatalytic activities that increase TC removal. A statistical analysis of time-series data shows that the photocatalytic degradation of TC follows first order kinetics. Overall, the findings from this study demonstrate the potential application of catalyst immobilization in the photocatalytic removal of tetracycline in sewage.