Photocatalytic decomposition of DMMP on titania

The photocatalytic decomposition of gas-phase dimethyl methylphosphonate (DMMP) on TiO2-coated glass substrate was studied using a single-pass reactor. The disappearance of DMMP and the appearance of products were monitored for several DMMP concentrations between 1 and 90 ppmv in air. Intrinsic reaction rates were determined, products were identified and reaction chemistry has been postulated. The main reaction products identified were carbon dioxide and carbon monoxide in the gas-phase, and methylphosphonic acid and phosphate on the catalyst. It was found that due to build-up of surface phosphorus-containing species, the catalyst de activated relatively rapidly. One of the interesting results of this study is that the catalyst activity was completely recovered by washing with water and partially recovered by exposure to UV (UVA; similar to 352 nm) Light. (C) 1998 Elsevier Science S.A. All rights reserved.