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Mera N.,Japan National Institute of Advanced Industrial Science and Technology | Hirakawa T.,Japan National Institute of Advanced Industrial Science and Technology | Sano T.,Japan National Institute of Advanced Industrial Science and Technology | Takeuchi K.,Japan National Institute of Advanced Industrial Science and Technology | And 3 more authors.
Applied Catalysis B: Environmental | Year: 2014

Dimethyl methylphosphonate (DMMP) removal by a continuous photocatalytic reaction system at different levels of humidity (RH) was investigated for the purpose of allowing rescue operations at disaster sites over an extended period of time when applied to gas masks or other protective gear. With a high flow rate of air (10L/min), around 85% of the 0.17μmol/L DMMP was successfully eliminated by this photocatalytic reaction system regardless of relative humidity. On the other hand, the formation of intermediates on the TiO2 surface indicated that photocatalytic activity was dependent on relative humidity, and during a 5-h test period, the ratio of photocatalytic DMMP conversion reached 74.5% at 100% RH. DMMP adsorption onto the TiO2 surface was found to be quite strong; DMMP removal was observed despite low humidity and dark conditions. © 2013 Elsevier B.V. Source


Sato K.,Chiba Institute of Science | Hirakawa T.,Japan National Institute of Advanced Industrial Science and Technology | Komano A.,Chiba Institute of Science | Kishi S.,Chiba Institute of Science | And 8 more authors.
Applied Catalysis B: Environmental | Year: 2011

The adsorption and photocatalytic degradation of nerve agent, isopropyl methylphosphonofluoridate, Sarin (GB) as a real Chemical Warfare Agent (CWA) on powdery Titanium dioxide (TiO2) film have been investigated using Gas chromatography/mass spectrometry (GC/MS) analysis in ambient atmosphere. We found that the ability to decontaminate GB molecules on TiO2 photocatalyst can be estimated to be 42 molecules/nm2, indicating that 1g of TiO2 photocatalyst can decontaminate 3.4mmol of GB molecules as the limitation value to maintain the photocatalytic activity. We also elucidated a plausible photocatalytic decontamination mechanism of GB at the surface of TiO2 photocatalyst on the basis of the results obtained in this study. © 2011 Elsevier B.V. Source


Hirakawa T.,Japan National Institute of Advanced Industrial Science and Technology | Sato K.,Chiba Institute of Science | Komano A.,Chiba Institute of Science | Kishi S.,Chiba Institute of Science | And 8 more authors.
Journal of Physical Chemistry C | Year: 2010

The adsorption and photocatalytic degradation of nerve agent, isopropyl methylphosphonofluoridate, Sarin (GB) on powdery TiO2 film has been investigated using attenuated total reflection infrared Fourier transform spectroscopy (ATR-FTIR) in ambient atmosphere. Producing innocuous isopropyl methylphosphonic acid as a consequence of GB adsorption at the surface of TiO2 indicates that powdery TiO2 film is effective to hydrolyze GB. The adsorbed GB and IMPA were quickly decomposed by TiO 2 photocatalysis to give isopropanol, acetone, formate, and methylphosphonic acid, and finally completely mineralized to phosphoric acid, water, and carbon dioxide. We also elucidated a plausible adsorption structure and photocatalytic decomposition mechanism of GB at the surface of TiO 2 photocatalyst. Copyright © 2010 American Chemical Society. Source


Komano A.,Chiba Institute of Science | Hirakawa T.,Japan National Institute of Advanced Industrial Science and Technology | Sato K.,Chiba Institute of Science | Kishi S.,Chiba Institute of Science | And 8 more authors.
Applied Catalysis B: Environmental | Year: 2013

The TiO2 photocatalytic decomposition of ethyl-S-dimethylaminoethyl methylphosphonothiolate (VX) as a real chemical warfare agent (CWA) in liquid phase has been investigated by gas chromatography/mass spectrometry (GC/MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The TiO2 photocatalytic decomposition rate, rVX, was accelerated with increase in alkalinity. The several kinds of by-products such as diisopropylamine, ethyl methylphosphonic acid, oxygenated VX and partially oxidized VX were observed. On the basis of the by-products, the TiO2 photocatalysis were proposed as the P-S, C-N cleavage and oxygenation of VX molecule carried out mainly. The difference between rVX and vaporized dimethyl methylphosphonate (DMMP), rDMMP as CWA simulant was also investigated and the rVX was 30 times faster than the rDMMP. On the basis of the decomposition mechanism of VX and DMMP molecules, the results of the acceleration of rVX in alkaline condition and of the comparison of rVX and rDMMP were also discussed. © 2013 Elsevier B.V. Source


Hirakawa T.,Japan National Institute of Advanced Industrial Science and Technology | Sato K.,Chiba Institute of Science | Komano A.,Chiba Institute of Science | Kishi S.,Chiba Institute of Science | And 8 more authors.
Journal of Photochemistry and Photobiology A: Chemistry | Year: 2013

The specific differences on TiO2 photocatalytic decomposition rates of vaporized isopropyl methylphosphonofluoridate, sarin (GB), r GB as a real Chemical Warfare Agent (CWA) and vaporized dimethyl methylphosphonate (DMMP), rDMMP as CWA simulant in gas phase have been investigated by Gas chromatography/mass spectrometry (GC/MS) analysis in ambient. The concentration of GB molecules adsorbed at the surface of TiO 2 in the dark, CGB, was 28 times larger than CDMMP in the dark. The rGB was then 3.3 times faster than the rDMMP. The results were explained by taking into account faster hydrolysis of GB molecules at the surface of TiO2 and the larger diffusion constant of GB in the gas phase than DMMP molecules. The effect of F- adsorption at the surface of TiO2 as fluoridated surface on the TiO2 photocatalysis was also studied. © 2013 Elsevier B.V. Source

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