Inactivation of Escherichia coli on anatase and rutile nanoparticles using UV and fluorescent light (original) (raw)
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Photocatalytic inactivation of microorganisms using nanotubular TiO2
Applied Catalysis B: Environmental, 2011
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 TiO 2 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 TiO 2 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 TiO 2 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.
Advances in Applied Ceramics, 2012
Water disinfection (removal of microbial agents) using sunlight is an emerging technology, which has the capacity to address the global shortage of drinking water. Therefore, intensive investigations in many laboratories aim to develop photocatalyst for water disinfection. The research is focused on titanium dioxide (TiO 2 ), which is the most promising candidate for high performance photocatalyst able to address the commercial requirements. The present work (Part 1) considers the effect of defect disorder on semiconducting and photocatalytic properties of TiO 2 (rutile) in water disinfection using solar energy. It is shown that photocatalytic properties of TiO 2 in water are closely related to the light induced reactivity of TiO 2 with water leading to the formation of active species, such as OH*, H 2 O 2 and O { 2 , which have the capacity to oxidise microorganisms. It is also shown that the ability of TiO 2 to form the active radicals is closely associated with the presence of point defects in the TiO 2 lattice and the related semiconducting properties. Therefore, photocatalytic properties of TiO 2 may be modified in a controlled manner by changes in its defect disorder. Consequently, defect chemistry may be used as the framework in the development of TiO 2 with controlled properties that are desired for solar water disinfection. The following work (Part 2) considers the structure of bacteria and their reactivity/photoreactivity with TiO 2 in aqueous environments. Both Part 1 and 2 bring together the concepts of TiO 2 photocatalysis and the concepts of microbiology in order to derive the theoretical models that are needed for the development of high performance photocatalysts for solar water disinfection.
Applied Catalysis B: Environmental, 2013
This study aimed at comparing the photocatalytic efficiencies of various TiO 2 based photocatalysts for phenol degradation and bacteria inactivation under illumination with visible light. Commercial undoped anatase and rutile (both from Aldrich), Aeroxide P25 (Evonik Industries), nitrogen-doped anatase (Sumitomo TP-S201, Sumitomo Chemical Inc.), nitrogen and sulphur co-doped anatase (Kronos VLP7000, Kronos Titan GmbH), and our custom-synthesized nitrogen-and iron-doped TiO 2 , as well as nitrogen and sulphur co-doped Aeroxide P25 and silver-and gold-deposited Aeroxide P25 were studied. The photocatalytic efficiency of different types of titanium dioxide based photocatalysts was determined by inactivation of Escherichia coli K12 bacteria and by phenol decomposition. Electron spin resonance (ESR) in combination with spin trapping was used to get insight into the reactive oxygen species (ROS)-mediated photocatalytic processes in the presence of TiO 2 -based photocatalysts. ESR results confirmed that titanias which generated OH • radicals were efficient in E. coli disinfection, whereas titanias that were unable to produce OH • radicals did not reveal significant bactericidal action. Three of our home-made titanias (iron-, nitrogen-, nitrogen/sulphur) as well as the commercial nitrogen/sulphur codoped Kronos VLP7000 TiO 2 showed higher efficiency of phenol degradation than the well-established reference photocatalyst, Aeroxide P25, but showed much lower (if any) activity for bacteria inactivation, including Kronos VLP7000, which revealed extremely high efficiency for phenol decomposition. Interestingly undoped Aldrich rutile (with large particles -100-700 nm) had the highest efficiency for inactivation of E. coli and also had fairly high activity of phenol degradation. of many model microorganisms were carried out in the presence of TiO 2 -based photocatalysts.
Materials Science in Semiconductor Processing, 2015
Research into the development of solar and visible light active photocatalysts has been significantly increased in recent years due to its wide range of applications in treating contaminants of emerging concern (CECs), endocrine disrupting compounds (EDCs), bacteria and cyanotoxins. Solar photocatalysis is found to be highly effective in treating a wide range of CECs from sources such as pharmaceuticals, steroids, antibiotics, phthalates, disinfectants, pesticides, fragrances (musk), preservatives and additives. Similarly, a number of EDCs including polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs), bisphenol A (BPA), organotins (OTs), volatile organic compounds (VOCs), natural and synthetic estrogenic and androgenic chemicals, pesticides, and heavy metals can be removed from contaminated water by using solar photocatalysis. Photocatalysis was also found effective in treating a wide range of bacteria such as Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Salmonella typhi and Micrococcus lylae. The current review also compares the effectiveness of various visible light activated TiO2 photocatalysts for treating these pollutants. Doping or co-doping of TiO2 using nitrogen, nitrogensilver, sulphur, carbon, copper and also incorporation of graphene nano-sheets are discussed. The use of immobilised TiO2 for improving the photocatalytic activity is also presented. Decorating titania photocatalyst with graphene oxide (GO) is of particular interest due to GO's ability to increase the photocatalytic activity of TiO2. The use GO to increase the photocatalytic activity of TiO2 against microcystin-LR (MC-LR) under UV-A and solar irradiation is discussed. The enhanced photocatalytic activity of GO-TiO2 compared to the control material is attributed to the effective inhibition of the electron-hole recombination by controlling the interfacial charge transfer process. It is concluded that there is a critical need for further improvement of the efficiency of these materials if they are to be considered for bulk industrial use.
Developments in photocatalytic antibacterial activity of nano TiO2: A review
Korean Journal of Chemical Engineering, 2016
TiO 2 , which is one of the most explored materials, has emerged as an excellent photocatalyst material for environmental and energy fields, including air and water purification, self-cleaning surfaces, antibacterial and water splitting. This review summarizes recent research developments of TiO 2-based photocatalyst used for photocatalytic antibacterial applications. Several strategies to enhance the efficiency of TiO 2 photocatalyst are discussed, including doping with metal ions, noble metals, non-metals, and coupling with other materials. The mechanism of photocatalytic antibacterial activity in the presence of nano-sized TiO 2 is also discussed. The modified TiO 2 photocatalyst significantly inhibits the growth of bacterial cells in response to visible light illumination. TiO 2 photocatalysis appears to be promising as a route of advanced oxidation process for environmental remediation.
Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology, 2016
The inactivation of Escherichia coli and Qβ phage was examined following their photocatalytic treatment with TiO2 hollows and spheres that had been prepared by electrospray, hydrothermal treatment, and calcination. The crystal structures of the hollows and spheres were assigned to TiO2 anatase, and the surface areas of the hollows and spheres were determined to be 91 and 79 m(2) g(-1), respectively. Interestingly, TiO2 spheres exhibited higher anti-pathogen performance than TiO2 hollows, a difference we ascribe to the prevention of light multi-scattering by microorganisms covering the surfaces of the TiO2 particles. The photocatalytic decomposition of dimethyl sulfoxide (DMSO) in the presence of TiO2 hollows and spheres was examined in order to study the dependence of photocatalytic activity on TiO2 morphology for the size scale of the reactants. TiO2 hollows provided greater photocatalytic decomposition of DMSO than did TiO2 spheres, in contrast to the pattern seen for pathogen ina...
Inactivation of pathogenic microorganisms in the photocatalytic process on nanosized TiO2 crystals
2008
The kinetics of the photocatalytic oxidation of E. coli gram-negative bacteria and the basic components of the cell wall membrane (LPS, PE, and PGN) on a porous film composed of TiO 2 nanoparticles was studied using frustrated total internal reflection FTIR spectroscopy. Structural changes in the cell wall membrane at the initial stage of cell oxidation were revealed. It was demonstrated that the cell's organic material is photocatalytically oxidized in such a manner that the TiO 2 surface is cleaned. Laser photolysis experiments demonstrated that the organic material of the cell wall membrane reduces holes in the valence band of TiO 2 .
Semiconductor Photocatalysis - Materials, Mechanisms and Applications, 2016
This chapter presents the use of a commercial micro-sized TiO 2 powder as an alternative to the traditional nano-powders as semiconductors in photocatalytic processes. Results of the photocatalytic efficiency towards the photodegradation of the traditional pollutant molecules both in gas phase (nitrogen oxides (NO x) and volatile organic compounds (VOCs)) and in water phase (phenol) are presented and compared to the results obtained with two nano-sized reference powders. Micro-sized TiO 2 is also industrially coated at the surfaces of porcelain grés tiles (Active Clean Air and Antibacterial Ceramic™). The possibility to have a photocatalytic material, strongly stuck at the surface of a vitrified tile, increases the use of photocatalysis in real conditions: no problem of filtration of the semiconductor from the liquid medium after use and no risks of leakage of nanoparticles in the atmosphere. Tests were performed using reactors equipped with UV-A lamps and with suitable analytical systems, depending on the final purpose. Characterization data from both powders and coated tiles are put in correlation with the photocatalytic results to understand the semiconductor action during the photocatalytic process. Polluting molecules were chosen in order to cover all the common aspects of environmental pollution: NO x and some VOCs represent the model molecules to test the efficiency of the micro-sized TiO 2 (degradation from the pristine molecule to CO 2 or inorganic salts) in gas phase. As for the water pollution, phenol was chosen as common pollutant in worldwide rivers. Moreover, tests on self-cleaning and antibacterial properties are also reported. The positive results of micro-sized TiO 2 both in powder and coated onto the surface of porcelain grés tiles open the way to new photocatalytic products that do
Chemical engineering transactions, 2020
In this study, the TiO2 nanoparticles were coated on the monolithic surface by a dip-coating technique. Characterization of synthesized samples was determined by X-ray diffraction. Antibacterial application of the samples was investigated under simulated solar irradiation on Escherichia coli (E. coli) bacteria. A 5.7 log CFU mL-1 decrease of E. coli was observed with TiO2 nanoparticles after 3 h irradiation, whereas the number of surviving E. coli cells decreased by 2.7 log CFU mL-1 with monolithic TiO2 at the same irradiating condition. Despite the reduction of photocatalytic antibacterial effect, the results confirmed the photocatalytic antibacterial activity of monolithic TiO2 under simulated sunlight irradiation as well as revealed its potential in practical water treatment applications.
Photocatalytic inactivation of E. coli in surface water using immobilised nanoparticle TiO 2 films
Water Research, 2009
Photocatalysis is a promising method for the disinfection of potable water in developing countries where solar irradiation can be employed, thus reducing the cost of treatment. In addition to microbial contamination, water normally contains suspended solids, dissolved inorganic ions and organic compounds (mainly humic substances) which may affect the efficacy of solar photocatalysis. In this work the photocatalytic and photolytic