Photocatalytic inactivation of microorganisms using nanotubular TiO₂

Photocatalysis is a well known process for deactivation contaminations in aqueous solutions. However, enhancing the photocatalytic process efficiency remains a challenge and a subject of extensive research. In this paper, nanotubular TiO₂ oxide layer with high surface area was grown and was used as a photocatalyst, inactivating Escherichia coli bacteria and other microorganisms, as well. The photocatalytic process was studied and optimized, subsequent to filtration of the nutrient broth, using saline solution. The double layer capacitance in the interface between the oxide and the solution was measured with the use of electrochemical impedance spectroscopy method and the isoelectric point was found to be at a pH value of 6.8. This result was correlated to the photocatalytic bacteria's inactivation rate in different pH solution. One of the advantages of using immobilized TiO₂ over a powdery photocatalyst is its ability to be recycled and reused. This was well studied with photocatalytic inactivation cycles of the E. coli bacteria along with MeO degradation. It was found that while no concern of reusing the TiO₂ during MeO degradation do exist, the need for a regeneration treatment after several cycles of inactivation E. coli bacteria emerges. Finally, E. coli bacteria were deactivated under a direct sunlight irradiation. This process is proven to be an efficient method for a future commercial photocatalytic cell fabrication.