Photocatalytic Inactivation of Salmonella typhimurium by Floating Carbon-Doped TiO2 Photocatalyst

Abstract

Photocatalysis application is considered as one of the most highly promising techniques for the reduction in wastewater pollution. However, the majority of highly efficient photocatalyst materials are obtained as fine powders, and this causes a lot of photocatalyst handling and reusability issues. The concept of the floating catalyst proposes the immobilization of a photocatalytic (nano)material on relatively large floating substrates and is considered as an encouraging way to overcome some of the most challenging photocatalysis issues. The purpose of this study is to examine floating photocatalyst application for Salmonella typhimurium bacteria inactivation in polluted water. More specifically, high-density polyethylene (HDPE) beads were used as a photocatalyst support for the immobilization of carbon-doped TiO2 films forming floating photocatalyst structures. Carbon-doped TiO2 films in both amorphous and anatase forms were deposited on HDPE beads using the low-temperature magnetron sputtering technique. Bacteria inactivation, together with cycling experiments, revealed promising results by decomposing more than 95% of Salmonella typhimurium bacteria in five consecutive treatment cycles. Additionally, a thorough analysis of the deposited carbon-doped TiO2 film was performed including morphology, elemental composition and mapping, structure, and depth profiling. The results demonstrate that the proposed method is a suitable technique for the formation of high-quality photocatalytic active films on thermal-sensitive substrates.

Floating Carbon-Doped TiO2 Photocatalyst with Metallic Underlayers Investigation for Polluted Water Treatment under Visible-Light Irradiation

“…In the current study, the metal underlayer effect upon the photocatalytic activity and bactericidal effect of carbon-doped TiO 2 was analysed. Our previous studies disclosed that C-doped TiO 2 as well as HDPE beads is a suitable combination for S. Typhimurium inactivation under UV-B light irradiation [64,65]. Here, we step further by improving our previous approach by adopting metallic underlayers for better dye decomposition as well as bacteria inactivation under visible-light irradiation.…”

“…A similar C-doped TiO 2 film technique was applied in our previous study, where 5-7 at. % of carbon was incorporated [65]. We presume that due to native HDPE beads surface morphology, deposited Ni might be penetrated or mixed with beads surface layers (i.e., polyethylene).…”

“…But these changes invoked the formation of amorphous TiO 2 which is known for the lower photocatalytic activity than anatase phase. While looking for the solution, it was decided to apply slightly different experimental set-up, which was successfully used in our previous work [65] of anatase phase C-doped TiO 2 film deposition on uncovered HDPE beads. The alternative set-up used slightly larger magnetron (95 mm diameter, 300 W pulsed DC power) that was placed at 10 cm distance from the HDPE beads.…”

“…The alternative set-up used slightly larger magnetron (95 mm diameter, 300 W pulsed DC power) that was placed at 10 cm distance from the HDPE beads. The more detailed description of this set-up is provided at [65].…”

“…Here, the magnetron sputtering technique was used for the deposition of both the metal underlayer and carbon-doped TiO 2 . Doping with carbon is straightforward to synthesise a photocatalyst with improved visible light photocatalytic activity [65]. Magnetron sputtering was chosen as a technique suitable for temperature-sensitive materials.…”