Application of Floating TiO2 Photocatalyst for Methylene Blue Decomposition and Salmonella typhimurium Inactivation

Abstract

The growing level of wastewater as well as pollution of freshwater by various bacteria are essential worldwide issues which have to be solved. In this contribution, nanocrystalline anatase TiO2 films deposited by magnetron sputtering on high-density polystyrene (HDPE) beads were applied as floating photocatalysts for Salmonella Typhimurium bacterial inactivation in water for the first time. Additionally, the photocatalytic degradation of methylene blue dye in the presence of HDPE beads with TiO2 film under UV-B irradiation was investigated. The suitability to adopt such floating photocatalyst structures for practical applications was tested in cycling experiments. The detailed surface morphology, crystal structure, elemental mapping, surface chemical composition and bond analysis of deposited TiO2 films were investigated by scanning electron microscope, X-ray diffractometer and X-ray photoelectron spectroscope techniques. The bacterial viability as well as MB decomposition experiments showed promising results by demonstrating that 6% of bacterial colonies were formed after the first run and only about 1% after the next four runs, which is an appropriate outcome for practical applications. NPN uptake results showed that the permeability of the outer membrane was significantly increased as well.

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

“…This means that the reduction in the pathogen was approximately 90% and 99% for the amorphous and anatase carbon-doped TiO 2 photocatalysts, respectively. The bactericidal effect induced by UV light-irradiated undoped anatase TiO 2 deposited on the HDPE beads was investigated in our previous paper [35]. In the case of undoped TiO 2 , the inactivation efficiency of bacteria averaged 97%, which is higher than the amorphous but lower than the anatase carbon-doped TiO 2 photocatalyst.…”

“…After treatment, the viability of the bacteria was evaluated by the spread plate method. The main parameters of the procedure were as follows: used sample volume-50 µL; sample dilution-1:2500; incubation medium-LB Agar; incubation time-20-22 h, with an incubation temperature of 37 • C. The remaining part of the treated bacteria suspensions was used for the measurement of membrane permeability by the N-phenyl-1-naphthylamine (NPN) uptake factor assay (more details on the used procedure are provided in [35]).…”

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.…”

“…The remainder parts of suspensions from the vessels were centrifuged at 3000× g for 5 min at 4 • C (Heraeus™ Megafuge™ 16R, Thermo Scientific, Bremen, Germany). The pellet was collected with NaPi buffer (100 mM, pH 8) to obtain 3.6 × 10 9 cfu/mL (OD 600 of 12), divided in two parts and further used for NPN uptake factor assay for membrane permeability determination (as described in [64] and for ethidium accumulation assay. 1.2 µM of EtBr was added into cell suspension then mixed and poured into wells to obtain a concentration 0.6 OD 600 in an each well.…”

Influence of the Metabolic Activity of Microorganisms on Disinfection Efficiency of the Visible Light and P25 TiO2 Photocatalyst

“…In general, it is considered, that the main factor of any photocatalytic water treatment process is the formation of ROS, namely, hydrogen peroxide (H 2 O 2 ), superoxide (O2•−), and hydroxide (OH•) radicals. In solution ROS are expected to act as strong oxidizing agents and fully oxidize harmful inorganic compounds, mineralize organic molecules, or cause fatal damage to the microbial membranes, proteins, and nucleic acids [12]. However, there is a fundamental difference in how strong oxidants react with various inorganic compounds and how they affect live microorganisms which can actively respond to the external oxidation.…”