A safe and compact flow platform for the neutralization of a mustard gas simulant with air and light

A low footprint, mobile, robust and frugal chemical neutralization technology is reported for the oxidative neutralization of a mustard gas simulant. It relies on the inherent properties of a highly engineered continuous flow setup and carefully optimized and simple, yet robust, experimental conditions. The neutralization protocol uses only non-toxic, widely available and cheap chemicals. The continuous flow setup integrates a singlet oxygen generator and exploits its oxidative power to neutralize 2-chloroethyl ethyl sulfide (CEES), the most common thioether mustard gas simulant. The flow reactor can be connected to either pressurized oxygen or air and handles CEES as a 1 M solution in EtOH containing a trace amount (0.06 mol%) of a non-toxic and widely available photosensitizer (Methylene Blue). Upon irradiation with visible light (orange or white light), total and highly selective neutralization towards the corresponding non-toxic sulfoxide (1-chloro-2-(ethylsulfinyl)ethane, CEESO) is obtained with reactor effluents containing less than 1% of the corresponding potentially toxic sulfone (1-chloro-2-(ethylsulfonyl)ethane, CEESO2). With a low footprint (L x W x H 94 x 42 x 40 cm), this neutralization technology can be embarked on a vehicle for on-site interventions, localized at a neutralization facility or both. The experimental work is also supported with a computational rationalization of the reactivity of CEES towards singlet oxygen.