Electrochemical Enhancement of Photocatalytic Disinfection on Aligned TiO₂ and Nitrogen Doped TiO₂ Nanotubes.

Cristina Pablos,Dionysios Dionysiou,Javier Marugán,Patrick Dunlop,Rafael Van Grieken,Jeremy Hamilton,John Byrne

doi:10.3390/molecules22050704

Abstract

TiO2 photocatalysis is considered as an alternative to conventional disinfection processes for the inactivation of waterborne microorganisms. The efficiency of photocatalysis is limited by charge carrier recombination rates. When the photocatalyst is immobilized on an electrically conducting support, one may assist charge separation by the application of an external electrical bias. The aim of this work was to study electrochemically assisted photocatalysis with nitrogen doped titania photoanodes under visible and UV-visible irradiation for the inactivation of Escherichia coli. Aligned TiO2 nanotubes were synthesized (TiO2-NT) by anodizing Ti foil. Nanoparticulate titania films were made on Ti foil by electrophoretic coating (P25 TiO2). N-doped titania nanotubes and N,F co-doped titania films were also prepared with the aim of extending the active spectrum into the visible. Electrochemically assisted photocatalysis gave higher disinfection efficiency in comparison to photocatalysis (electrode at open circuit) for all materials tested. It is proposed that electrostatic attraction of negatively charged bacteria to the positively biased photoanodes leads to the enhancement observed. The N-doped TiO2 nanotube electrode gave the most efficient electrochemically assisted photocatalytic inactivation of bacteria under UV-Vis irradiation but no inactivation of bacteria was observed under visible only irradiation. The visible light photocurrent was only a fraction (2%) of the UV response.

Highlights

Chlorination is an effective approach for the disinfection of water; it can lead to the formation of disinfection by-products e.g., trihalomethane, which can be mutagenic and carcinogenic.some species of pathogenic microorganisms are resistant to chlorination and ozonation [1].As a consequence, new technologies have been developed to overcome the drawbacks of current disinfection processes
SEM analysis of TiO2 nanostructures obtained by anodization of Ti foil were carried out for both, SEM analysis of TiO2 nanostructures obtained by anodization of Ti foil were carried out for undoped and doped titania nanotube samples
Nanoparticulate films of N,F-TiO2 and P25 were prepared for comparison purposes

Summary

Introduction

Chlorination is an effective approach for the disinfection of water; it can lead to the formation of disinfection by-products e.g., trihalomethane, which can be mutagenic and carcinogenic.some species of pathogenic microorganisms are resistant to chlorination and ozonation [1].As a consequence, new technologies have been developed to overcome the drawbacks of current disinfection processes. Chlorination is an effective approach for the disinfection of water; it can lead to the formation of disinfection by-products e.g., trihalomethane, which can be mutagenic and carcinogenic. Some species of pathogenic microorganisms are resistant to chlorination and ozonation [1]. New technologies have been developed to overcome the drawbacks of current disinfection processes. Heterogeneous photocatalysis is an advanced oxidation process (AOP) which can operate under ambient temperature and pressure, and oxygen from the air can be utilized as the oxidant without the addition of consumable chemicals. If one can use solar energy to drive the photocatalytic process it becomes a truly clean technology. Since the early work of Molecules 2017, 22, 704; doi:10.3390/molecules22050704 www.mdpi.com/journal/molecules

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