Standardized Figures of Merit for Proper Benchmarking of Photocatalytic Inactivation of Bacteria Using Thin Films Based on TiO2 Nanostructures
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Abstract The study of photocatalysts fixed to surfaces for the inactivation of bacteria in wastewater has increased in recent years. However, there are no standardized methods to analyze the photocatalytic antibacterial activity of these materials, and no systematic studies have attempted to relate this activity to the number of reactive oxygen species generated during UV‐light irradiation. Additionally, studies regarding photocatalytic antibacterial activity are usually carried out with varying pathogen concentrations, UV light doses, and catalyst amounts, making it difficult to compare results across different materials. The work introduces the photocatalytic bacteria inactivation efficiency (PBIE) and bacteria inactivation potential of hydroxyl radicals (BIPHR) figures of merit for evaluating the photocatalytic activity of catalysts fixed onto surfaces for bacteria inactivation. To demonstrate their applicability, these parameters are calculated for various photocatalytic TiO 2 ‐based coatings, accounting for the catalyst area, the kinetic reaction rate constant associated with bacteria inactivation and hydroxyl radical formation, reactor volume, and UV light dose. This approach enables a comprehensive comparison of photocatalytic films prepared by different fabrication techniques and evaluated under diverse experimental conditions, with potential applications in the design of fixed‐bed reactors.Keywords:
Hydroxyl radical
OBJECTIVE To establish a HPLC method for the determination of elimination ratio of hydroxyl radicals by Traditional Chinese Medicine.METHODS Benizoic acid reacted with hydroxyl radicals produced by Co2+ and H2O2,and main hydroxylated products were made.Extractives of Traditional Chinese Medicine eliminated hydroxyl radicals in solution and reduced the amounts of the products.Then the elimination ratio of hydroxyl radicals by Traditional Chinese Medicine was determined indirectly.RESULTS The optimal determination condition was found out and the reaction system of benizoic acid and hydroxyl radicals was analyzed.CONCLUSION The method can be applied to screen the hydroxyl radical scavenger and study the hydroxyl radical.
Hydroxyl radical
Scavenger
Hydroxyl value
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In terms of the UV irradiating directions, photocatalysis with TiO2 thin films can be divided into two types, the background irradiated photocatalysis and the foreground irradiated one. Comparatively, background irradiated photocatalysis has an advantage of avoiding the UV light attenuation which foreground irradiated one suffers when the light is going through the solution. In this article, the influence of the thickness of the films, the wavelength of light source and non-uninformly doping with V on the photocatalytic efficiency of the catalyst in case of background irradiated photocatalysis is investigated, and simultaneously it is compared with foreground irradiated one. The results show that in case of background irradiated photocatalysis there is an optimal thickness of the film according to the wavelength of the light source that is limited in the range of 300 nm to 388 nm, which is quite different from foreground irradiated one. But in both cases, the catalyst's photocatalytic activities are improved by non-uniformly doped with V.
Visible spectrum
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Hydroxyl radical
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Redistribution
Settling
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In this paper,salicylic acid was used as a molecular probe to determine hydroxyl radicals in aquatic system.The steady state concentrations and quantum yields of hydroxyl radicals formed by ultraviolet irradiation of nitrate and nitrite solutions were explored.Formation rate of hydroxyl radicals and removal rate of organic pollutants through oxidation with hydroxyl radical in natural water were estimated on the basis of above results.
Hydroxyl radical
Ultraviolet
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Isoprene
Hydroxyl radical
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Of the active forms of oxygen hydroxyl radicals are the most reactive. The use of hydroxyl radicals is based on advanced oxidation technologies for water purification. However, OH* radicals quickly terminate in interactions with each other or they are consumed in reactions with water impurities at the place of radical creation. The possibility of transporting hydroxyl radicals without a significant decrease in their concentration was investigated. It was shown that under conditions for forming ozone-hydroxyl mixture, hydroxyl radicals could be transported 40 cm in up to 0.12 s. The main condition needed for transportation is the accumulation of hydrogen peroxide. Hydrogen peroxide interacts with ozone, maintaining the concentration of hydroxyl radicals. As an example of a device that can create an ozone-hydroxyl mixture, a corona discharge, was considered. The results can be useful in the development of water purification devices.
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Peroxide
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Underlayer exposed ZnO:Al-TiO2 coupled films are prepared by different means.Surface morphology by SEM,microstructure by XRD,film thickness by surface profiler and photocatalysis are investigated.In order to explain the enhanced photocatalysis,reaction Ag++→Ag↓ is adopted to clarify the mechanism.It turns out that during the process of photocatalysis the exposed part of the underlayer releases e-and this suppresses recombination of light-induced charges,thus enhanced photocatalysis.
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The ability to generate hydroxyl radicals of the different electrolyzed water and the sodium hypochlorite solution in the process of storage was investigated.The results showed that the changes of p H did not affect the ability of electrolyzed water to generate hydroxyl radicals when the available chlorine concentration was 17 mg / L.When the available chlorine concentration was 60 mg / L,the ability to generate hydroxyl radicals increased with the p H increasing,the hydroxyl radicals in slightly acidic electrolyzed water did not change significantly within 0~24h,the concentration of hydroxyl radicals reached the maximum when the storage time of 5h both at 17℃ and 4℃.At the different p H and the available chlorine concentration,and the capacity of electrolyzed water to produce hydroxyl radicals was stronger than that of sodium hypochlorite solution.
Sodium hypochlorite
Hydroxyl radical
Hydroxyl value
Hypochlorite
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