Evaluation of titanium dioxide for the adsorption and reactivity of the sulfur mustard simulant 2-chloroethyl ethyl sulfide

This thesis reports the investigation of the degradation of the sulfur mustard simulant 2-chloroethyl ethyl sulfide (CEES) over the metal oxide TiO2. The ultimate goal is the development of catalytic adsorbent materials that more effectively decontaminate surfaces at ambient conditions once they have been exposed to chemical warfare agents (CWAs) such as sulfur mustard (HD). TiO2 is an appealing candidate for this application because of its reported use in photocatalysis and pollution control under ambient conditions. For this reason, the interactions of CEES on commercially available polycrystalline Evonik-Degussa AeroxideRTM P25 and amorphous NanoActive(TM) TiO2 were investigated. Each commercial sample was analyzed under two thermal pre-activation schemes: oxidized (200 torr O2 at 400°C for 2 hrs) or reduced (200 torr H2 at 400°C for 2 hrs).;The thermal pre-activation procedure was found to induce changes in the morphological and crystalline properties of NanoActive (NA) while the P25 remained unchanged. The magnitude of these changes was similar for either oxidation or reduction. Pre-activation of the amorphous NA yielded anatase crystallites with mean diameter of 10 nm. This crystallite formation was accompanied by a decrease in surface area and pore volume by 80% and 17%, respectively. Infrared analysis revealed chemical activity at temperatures well above ambient (> 200°C) and is further confirmed by preliminary differential scanning calorimetry data. Long term (40 days) ambient reactivity investigations showed no reactivity for P25 stored at ambient temperature and light conditions. The influence of moisture conditioning was also investigated at two levels: below 10% RH and at 50% RH. Changes in this variable did not alter the reactivity of P25.;While these samples exhibit very different responses to the thermal pre-activation procedure, these resulting surfaces do not show any improvement in reactivity when compared to the original sample. Since no chemical activity is observed until temperatures exceeding 200°C, it is concluded that neither P25 nor NA are desirable as catalytic adsorbents for CWA decontamination at ambient conditions.