Using photoactivated periodate to decompose TOC from hydrolysates of chemical warfare agents

Photoactivated periodate was investigated for the disposal of hydrolysates of chemical warfare agents (HCWAs) when hydrolysis is used as the first step in disposal of chemical warfare agents (CWAs). The kinetics and mechanisms of total organic carbon (TOC) loss by photoactivated periodate oxidation of the HCWAs, thiodiglycol (TDG), 3,3-dithiopropanol (TDP), and 1,4-thioxane (TX), were investigated at pH 3, 7, and 10. At pH 3, TDG had the fastest rate of TOC loss followed by TDP and TX. Less TOC loss at pH 7 compared to pH 3 was attributed to ozone decomposition reactions and OH quenching by mineralization products (e.g., bicarbonate) at pH 7. At pH 10, compared to pH 7, TX had more TOC loss, but TDG and TDP exhibited similar TOC loss as pH 7 conditions. In all experiments, TOC loss ceased when periodate was depleted. Solution conditions such as pH, initial ratio of periodate to HCWA, nitrogen purging, and consecutive additions of periodate were investigated to explore the role of reactive species in TOC loss and to determine optimal periodate mineralization conditions for HCWAs. In all cases consecutive additions of periodate provided the most TOC loss but the conditions for the most efficient use of periodate was different for each HCWA.