Ozone and flow technology for the destruction of chemical warfare agents
A study from the Center for Integrated Technology and Organic Synthesis (CiTOS) of the University of Liège demonstrates the power of ozone and computational tools for the neutralization of mustard gas simulants. Researchers at CiTOS propose a faster, safer, and more economical process for neutralizing the chemical threat. The uniqueness of the method lies in a methodology where a computer generates optimal destruction conditions before being implemented in the laboratory, with a significant impact on waste reduction. The results of this study are now published as a communication in Green Chemistry.
"Our work at the Center for Integrated Technology and Organic Synthesis relies on the synergy between computational chemistry, organic chemistry, and micro/mesofluidic technologies. We are developing new synthesis protocols with a minimal number of experiments, and the preliminary investigation of operational conditions is carried out in silico through quantum chemistry," explains Jean-Christophe Monbaliu, head of the CiTOS Lab (Faculty of Science/MolSys Research Unit) at the University of Liège. This methodology significantly reduces waste generation during optimization phases and also limits the handling of toxic compounds, thereby enhancing operator safety, which is critical in research concerning the destruction of chemical weapons.
In a series of previous articles, researchers at CiTOS, in collaboration with a team from the University of Rouen (Dr. Julien Legros, Prof. Pierre-Yves Renard), relied on micro and mesofluidic reactors to design safe and efficient neutralization processes. Despite significant advancements in the destruction of military stockpiles, there are still numerous mustard gas maritime dump sites dating back to World Wars I-II. These represent a silent threat with unpredictable ecological and societal impacts. "This context justifies the development of new, more effective, straightforward, and widely accessible neutralization methods," explains Jean-Christophe Monbaliu. An effective neutralization method must be as straightforward as possible to ensure direct applicability during emergency situations. It is inconceivable to develop complex, costly, and time-consuming methods that would only delay an emergency response. "In our two previous articles, we presented a method combining air and light and a method based on the generation of an organic version of bleach. Despite their effectiveness for neutralization and their widespread applicability, these processes co-generated wastes in addition to the neutralized compounds," continues Jean-Christophe Monbaliu.
In addition to the environmental aspect of neutralization processes, this research theme is even more complex because the targeted compounds cannot be prepared or purchased since they have been banned by the Chemical Weapons Convention (also for obvious reasons of toxicity). This presents a significant challenge, as it deprives the chemist of the object of their study. To overcome these difficulties, researchers at CiTOS have developed an innovative approach that leverages the advantages of computational chemistry. This approach allows for the safe and legal study of mustard gas and its reactivity in silico (i.e., via computer simulation). "These computational tools enable us to rationally select mustard gas simulants, which are molecules similar to mustard gas in terms of chemical properties but without its toxicity. These simulants are then used in the laboratory to develop safe neutralization conditions," says the Director of CiTOS. "Even better, these in silico tools also allow us to predict the optimal neutralization conditions, thereby speeding up their development without generating waste."
The team focused on ozone as a neutralization reagent. Ozone is generated directly from air and manipulated in a hermetic mesofluidic system where it destroys mustard gas simulants. The method requires no additives, no catalyst, and produces only oxygen as an additional byproduct. The optimal conditions were then tested in collaboration with Flow Technology Manufacturer Corning, leading to the design of a safe, mobile, and highly efficient neutralization system. Mustard gas simulants are rendered harmless in a mere second using ozone, with minimal waste generation. Once the neutralization conditions are validated in the laboratory using simulants, the same computational tools confirm in silico the experimental results on actual mustard gas, with the assistance of a kinetic model.
Boddaert, P. Bianchi, D. V. Silva-Brenes, A. Musina, M. Winter, P. M. C. Roth, P.-Y. Renard, J. Legros and J.-C. M. Monbaliu, A miniaturized ozonolysis flow platform for expeditious sulfur mustard warfare simulant neutralization, Green Chem. 2023, Advance Article (DOI: 10.1039/D3GC03470D).
F.R.S.-FNRS (Incentive grant for scientific research MIS F453020F, Jean-Christophe Monbaliu; PhD Fellowship ASP 1.A.054.21F, Pauline Bianchi). Computational resources were provided by the “Consortium des Équipements de Calcul Intensif” (CÉCI), funded by the “Fonds de la Recherche Scientifique de Belgique” (F.R.S.-FNRS) under Grant No. 2.5020.11a and by the Walloon Region.