Photo-degradation of yperite over V, Fe and Mn-doped titania–silica photocatalysts

Abstract

The photocatalytic decomposition of yperite (bis(2-chloroethyl)sulfide), a chemical warfare agent, was achieved by using titania-silica catalysts doped with several transition metal ions. The preparation of these catalysts was achieved by impregnation of a titania-silica mixed oxide previously synthesized using a sol-gel route with salts of the doping elements (vanadium, iron, manganese). The above catalysts were characterized using several spectroscopic techniques: FTIR, Raman, DR-UV-Vis, and XPS. The band gap energy was measured for each photocatalytic system. The reaction was carried out in two different types of reactors, i.e. naturally aerated and a closed quartz tube aerated under a constant flow, and using two types of irradiation, UV-Vis and Vis. The investigated systems proved to be extremely active, leading to an almost complete degradation of yperite in 2 h of irradiation. An excellent correlation between the photocatalytic performances and the band gap has been found. Based on the characterization data and on the temporal evolution of the reaction products, a reaction mechanism has been suggested. This mechanism considers two distinct pathways for the decomposition of yperite, namely the C-S bond cleavage and the S oxidation.

Catalytic Processes for the Neutralization of Sulfur Mustard

“…The resulting radical cation intermediates can eliminate chloroethylene (or its hydration product) to form surface-bound thiyl radicals, which recombine to disulfides (Figure 11). [137] Subsequently,t he photocatalytic decomposition of mustard analogs was tested in the presence of doped TiO 2 (V,F e, Mn, W), [137,138] Au-supported TiO 2 , [139,140] ZnO, [141,142] and MnO 2 nanomaterials, [143] all suitable for visible light harvesting. Doped TiO 2 (V,F e, Mn, W) and Au-supported TiO 2 displayed improved sulfur mustard degradationc ompared with TiO 2 ,e specially under visible irradiation.…”

“…The resulting radical cation intermediates can eliminate chloroethylene (or its hydration product) to form surface‐bound thiyl radicals, which recombine to disulfides (Figure 11). [137] …”

“…Subsequently, the photocatalytic decomposition of mustard analogs was tested in the presence of doped TiO 2 (V, Fe, Mn, W), [137, 138] Au‐supported TiO 2 , [139, 140] ZnO, [141, 142] and MnO 2 nanomaterials, [143] all suitable for visible light harvesting. Doped TiO 2 (V, Fe, Mn, W) and Au‐supported TiO 2 displayed improved sulfur mustard degradation compared with TiO 2 , especially under visible irradiation.…”

Synergism of Activated Carbon and Undoped and Nitrogen‐doped TiO2 in the Photocatalytic Degradation of the Chemical Warfare Agents Soman, VX, and Yperite

“…oxidation, dehydrohalogenation, enzymatic hydrolysis, methanolysis). [37][38][39][40] Photocatalytic oxidation appears to be a viable alternative for chemical warfare agents decomposition because it generates less waste and can be performed without energy consumption or addition of any corrosive chemical. However, reported data using real warfare compounds is very scarce and there is an interest in establishing suitable photocatalysts for the complete detoxification of chemical warfare agents.…”

“…As can be seen, after 2 h HD was completely decomposed on both materials. It has been proposed that the decomposition of HD over titania-silica systems [40] follows two main reaction pathways (Scheme 3), both having in common the initial attack of oxygen on this chemical and differing in the occurrence of a subsequent CÀS bond splitting (pathway A in Scheme 3) or S atom oxidation (pathway B in Scheme 3).…”