Role of Visible Light-Activated Photocatalyst on the Reduction of Anthrax Spore-Induced Mortality in Mice

BACKGROUND: Photocatalysis of titanium dioxide (TiO(2)) substrates is primarily induced by ultraviolet light irradiation. Anion-doped TiO(2) substrates were shown to exhibit photocatalytic activities under visible-light illumination, relative environmentally-friendly materials. Their anti-spore activity against Bacillus anthracis, however, remains to be investigated. We evaluated these visible-light activated photocatalysts on the reduction of anthrax spore-induced pathogenesis. METHODOLOGY/PRINCIPAL FINDINGS: Standard plating method was used to determine the inactivation of anthrax spore by visible light-induced photocatalysis. Mouse models were further employed to investigate the suppressive effects of the photocatalysis on anthrax toxin- and spore-mediated mortality. We found that anti-spore activities of visible light illuminated nitrogen- or carbon-doped titania thin films significantly reduced viability of anthrax spores. Even though the spore-killing efficiency is only approximately 25%, our data indicate that spores from photocatalyzed groups but not untreated groups have a less survival rate after macrophage clearance. In addition, the photocatalysis could directly inactivate lethal toxin, the major virulence factor of B. anthracis. In agreement with these results, we found that the photocatalyzed spores have tenfold less potency to induce mortality in mice. These data suggest that the photocatalysis might injury the spores through inactivating spore components. CONCLUSION/SIGNIFICANCE: Photocatalysis induced injuries of the spores might be more important than direct killing of spores to reduce pathogenicity in the host

Photocatalytic and photoelectrocatalytic humic acid removal and selectivity of TiO(2) coated photoanode.

In this study, photocatalytic (PC) and photoelectrocatalytic (PEC) treatment methods were comparatively investigated as a possible means of removing humic acid (HA) following absorbance at 254 nm (UV(254)) and total organic carbon (TOC) analysis. The enhanced HA degradation rates were obtained in the PEC system over the conventional PC process under acidic, neutral and alkaline conditions. Preliminary and binary experiments were performed to determine the selectivity of the photoanode in terms of HA and chloride oxidation. TOC, chlorine and photocurrent parameters proved that HA was selectively removed before chlorine generation. The inhibitory effect of carbonate ions on the performance of photoanode was also studied under different pH values

selectivity of TiO2 coated photoanode

In this study, photocatalytic (PC) and photoelectrocatalytic (PEC) treatment methods were comparatively investigated as a possible means of removing humic acid (HA) following absorbance at 254 nm (UV254) and total organic carbon (TOC) analysis. The enhanced HA degradation rates were obtained in the PEC system over the conventional PC process under acidic, neutral and alkaline conditions. Preliminary and binary experiments were performed to determine the selectivity of the photoanode in terms of HA and chloride oxidation. TOC, chlorine and photocurrent parameters proved that HA was selectively removed before chlorine generation. The inhibitory effect of carbonate ions on the performance of photoanode was also studied under different pH values. (c) 2008 Elsevier B.V. All rights reserved

A comparative approach to the application of a physico-chemical and advanced oxidation combined system to natural water samples

Natural organic matter removal (NOM) efficiencies of samples from three major drinking water sources (Elmali, Omerli, and Buyukcekmece) of Istanbul were compared using different treatment systems. Enhanced coagulation as a physico-chemical method was applied using ferric chloride and aluminum sulphate as the coagulating agents. Moreover, the application of enhanced coagulation in combination with photocatalytic oxidation using TiO2 was investigated. The efficiency of NOM removal relevant to each treatment step was assessed through DOC removal, UV254 removal, and fluorescence measurements. Irrespective of the treatment applied as enhanced coagulation, photocatalytic oxidation or their combinations, the highest removal efficiency was determined for Elmali followed by Omerli and Buyukcekmece samples both in terms of DOC and UV254. Enhanced alum coagulation leads to significant variation in DOC removals as 44%, 28% and 26% for Elmali, Omerli, and Buyukcekmece water samples, respectively. Upon application of ferric chloride as the coagulant, the DOC removals achieved were found to be slightly higher as compared to alum. Moreover, the combined treatment incorporating photocatalytic oxidation subsequent to alum coagulation leads to 36%, 37%, and 50% of DOC removal for Omerli, Buyukcekmece, and Elmali respectively. The improvement of removal efficiencies in combined treatment systems were scrutinized with an emphasis on induced water properties as supported by the specific fluorescence intensities of the samples