Proceedings of the Public Security S&T Summer Symposium 2009

CRTI 06-0170RD

Organophosphorus Agent Decontamination

Project Lead: Environment Canada

Federal Partner: Royal Military College of Canada

Industry Partner: SAIC Canada

Other Partners: Queen’s University; Research Institute of Hygiene, Occupational Pathology, and Human Ecology; State Research Institute of Organic Chemistry and Technology

Objectives

The primary objective of this study is to develop and evaluate a safe and rapid catalytic decontamination method designed to remove and destroy organophosphorus (OP) agents and pesticides from building materials, sensitive equipment, and soils. This project will build on novel solution chemistry developed by Queen’s University wherein metal ions catalyze the decomposition of OP agents through their reaction with light alcohols. In some applications (e.g., sensitive equipment or soils), the catalysts will be immobilized on polymers and silica-solid supports in order to be packaged in columns and used repeatedly.

Relevance

OP chemical warfare agents and toxic industrial chemicals form one of the largest groups of chemical terrorism agents. They also represent major threats in view of their extreme toxicity and availability as industrial chemicals. Existing decontamination technologies for these agents use corrosive ingredients, cannot be applied to sensitive equipment, and may be harmful to the environment. The proposed process will address these problems by developing an efficient, universal, and environmentally safe technology. It will be applicable to the chemical restoration of buildings and structures, as well as to the decontamination of sensitive equipment and soil. The resulting waste streams will be environmentally benign and will not require further waste containment or treatment operations.

The solid-supported catalytic methodology uses columns through which recovered solutions of OP contaminant are quickly neutralized. It provides an effluent that is pH neutral, is at ambient temperature, and contains no metal ions so that decontamination of sensitive equipment can be realistically accomplished. Moreover, recycling recovered neutralized solutions reduces the environmental footprint and the quantities of solvents that are needed.

Recent Progress and Results

The methanol-based catalytic system was used in preliminary experiments. These experiments were aimed at developing experimental and analytical procedures and determining key factors affecting decontamination of paraoxon in liquid phase. The decontamination efficiency was determined at various concentrations of catalyst and paraoxon and for different reaction times. This was done by quantification of residual paraoxon in the post-reaction mixture using gas chromatography/mass spectrometry (GC/MS) and ultraviolet-visible spectrometry techniques. Breakdown products were identified by GC/MS.

The researchers found that paraoxon (1 g/L) completely decomposed in 15 minutes even when the catalytic system was diluted up to 20 times of its original concentration. Diluted catalytic systems (up to 10 times) provided complete destruction of paraoxon in less than 5 minutes. Diethyl methyl phosphate and 4-nitrophenol have been identified as the main breakdown products.

The methanol-based catalytic system was effective at destroying Russian VX in liquid phase. Analytical procedures were developed and evaluated for GC/MS analysis of Russian VX and breakdown products.

The development of a solid-supported catalyst continued in two directions. The first solid matrix evaluated was lanthanides attached to terpyridine ligands, themselves attached to silica gel by amine links. The matrix was tested for the catalyzed methanolysis of paraoxon and ethyl ρ-nitrophenyl methylphosphonate. The complex showed a high to moderate reactivity. A drop in the rate constant was observed after each use of the matrix due to the leaching of metals. The value of the decrease in the rate constant depended on the metal (Sm³⁺~Eu³⁺>Yb³⁺). In addition to the conventional fixation of metals to solid supports via chelating ligands, a new method based on a microencapsulation technique was employed for fixing La³⁺ and Yb³⁺ to polystyrene. In the case of Yb³⁺, the leaching of the metal was prevented by varying the composition of the solution, which preserved the reactivity of the matrix. The rate constants were similar to the supported-terpyridine-Ln systems at around 7 × 10^-4 s^-1.

The high fluorophilicity of lanthanides causes them to bind very strongly to the fluoride anions released from phosphonofluoridates (e.g., sarin and soman) during methanolysis, which kills the metals’ reactivity. Metal additives were used to scavenge fluoride ions released into the solution. The efficiency of different metal additives, such as Sm(OTf)₃, Eu(OTf)₃, Yb(OTf)₃, EtSi(OMe)₃, Al(OiPr)₃, B(OPh)₃, B(OBu)₃, MeB(OH)₂, and p-Tol-B(OH)₂, was studied. Sm(OTf)₃ was found to be the most efficient additive and preserved 40 percent of the total activity in the presence of 4 eq. fluoride anions.

Impact

The newly developed methods for decontamination of sensitive equipment, building materials, and soils will have a significant impact on Canada’s ability to prepare for and recover from a chemical terrorism event. By allowing reuse of the solvents and catalysts, the decontamination methods present an enhanced environmentally and economically friendly solution for the destruction of OP compounds. The use of low-flammable, low-toxic perfluorocarbons as solvents will reduce harmful effects on the environment and responders. The possibility to reuse the reaction media will also highly reduce the amount of runoff. The rapid and complete destruction of OP agents will prevent the risk of contamination of the environment by the breakdown products.

Authors:

Vladimir Blinov, Emergencies Operational Analytical Laboratories and Research Support Division, Environment Canada, vladimir.blinov@ec.gc.ca

Konstantin Volchek, Environment Canada, konstantin.volchek@ec.gc.ca

R. Stanley Brown, Queen’s University, rsbrown@chem.queensu.ca

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