Removal of high concentration dimethyl methylphosphonate in the gas phase by repeated-batch reactions using TiO2

The aim of our study is to develop apparatuses that use TiO2 for effective decontamination of air contaminated by Sarin gas. We performed photocatalytic decomposition of gaseous dimethyl methylphosphonate (DMMP) by TiO2 and identified the oxidization products. The high activity of TiO2 (0.01 g) was observed under UV-light irradiation and high concentration DMMP (33.5 μM) was removed rapidly. On the other hand, DMMP was not decreased under UV-light irradiation without TiO2. This indicates that photocatalytic treatment is very effective for the removal of DMMP. Methanol, formaldehyde, formic acid, methyl formate, CO, CO2 and H2O were detected as the primary products. In the gas phase, no highly poisonous substances were detected. In order to examine the performance of photocatalytic activity during long-term reactions, we performed photocatalytic decomposition by repeated-batch reactions using TiO2. High photocatalytic activities decreased gradually. Meanwhile, the strong adsorption of TiO2 against DMMP was observed as photocatalytic activities decreased. During the repeated-batch reactions with the sample scaled up (TiO2: 0.1 g), the total amount of removed DMMP reached 968.5 μM by both photocatalytic decomposition and the strong adsorption of TiO2. These results suggest the possibility of removing large amounts of DMMP.