The decontamination of materials contaminated with highly toxic chemicals is a challenging problem involving transport and reaction of multiple species in multi-phase systems. Transport-reaction models were developed for liquid phase decontamination of thin film polymeric coatings containing absorbed contaminants.  The chemical warfare agent O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (known as VX) was used with several combinations of aqueous-based decontaminant solutions and polymeric substrates. Two primary mechanisms were considered: a) absorption of the decontaminant active species into the coating and reaction with the absorbed contaminant, and b) extraction of the absorbed contaminant into the adjacent decontaminant solution with subsequent reaction. Liquid phase batch reactor experiments revealed the primary reactions and corresponding kinetics for different decontaminants in the absence of an absorbing coating. Extraction dynamics from a contaminated substrate were also studied as a function of solution composition, ionic strength and pH, which change as the decontamination reaction proceeds. Additional experiments were performed in conjunction with an inverse analysis method to obtain model transport parameters for chemical species in the coatings. The experiments involved contaminating a substrate with a fixed VX exposure, applying a decontaminant, followed by a time-resolved, liquid phase extraction of the absorbing substrate via immersion in deionized water, and measuring the residual contaminant by chromatography. Model parameters were uniquely determined using the Levenberg-Marquardt nonlinear least squares fitting technique to best fit the experimental time evolution of extracted mass. The resulting decontamination model provides an accurate quantification of contaminant concentration profile within material, which is necessary to assess post-decontamination exposure hazards from vapor inhalation and direct dermal contact. The dominant decontamination mechanism for different substrate materials and decontaminant solutions was determined by comparing model predictions with experimental measurements of dermal uptake of VX from decontaminated substrates by a skin simulant material.

Decontamination of absorbing thin film coatings: Relative importance of extraction dynamics and reaction kinetics

248th National Meeting (2014)

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