Accelerated oxidation of mustard gas analog with PVA-based hydrogels

Sulfur mustard (HD) is a hydrophobic, volatile chemical warfare agent (CWA) that has been shown to contaminate surfaces as a solid residue. This sparks an ongoing search to rid HD residue from contaminated sensitive equipment with a simple, disposable material-based solution. Hydrogels as tunable polymeric matrices fit this niche due to their potential in formulating environment-friendly remediators for CWAs. The oxidation of sulfur in HD and its analogs affords fast methods for decontamination with minimal intermediates. Here we report our study of polyvinyl-alcohol (PVA)-based hydrogels comprising a bicarbonate-activated peroxide (BAP) system (ammonium bicarbonate and hydrogen peroxide (NH₄HCO₃-H₂O₂)) to release a strong oxidizer, peroxymonocarbonate ions (HCO₄ ^-), for long-term HD remediation at nearly neutral pH. The production of HCO₄ ^- by the PVA-based hydrogels with different concentrations of H₂O₂ was verified by NMR and Raman spectroscopy. The efficacies of these hydrogels on HD remediation were evaluated using the HD simulant, 2-chloroethyl ethyl sulfide (CEES). The amine oxide surfactant, N,N-dimethyl-1-dodecylamine N-oxide (DDAO), was incorporated into these BAP-enhanced hydrogels to facilitate the oxidation of CEES by increasing its solubility in the hydrogels. Through ¹³C-NMR analysis, a PVA-based hydrogel with BAP and DDAO was demonstrated to remediate 90% of CEES through accelerated oxidation (82%) and hydrolysis (8%) within 10 minutes. Additionally, the examination using headspace gas chromatography-mass spectrometry of the gas above a CEES-containing hydrogel showed that the relative concentration of CEES decreased by 99% within 60 to 80 minutes. Our illustrated combined use of HCO₄ ^- and amine oxide surfactants for boosting oxidative kinetics validates the versatility of this approach for applications with other gel-capture systems for advancing decontamination methods for hydrophobic substrates.