Ind. Eng. Chem. Res. 2002, 41, 1925-1928
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APPLIED CHEMISTRY Rapid Nucleophilic/Oxidative Decontamination of Chemical Warfare Agents George W. Wagner* and Yu-Chu Yang U.S. Army Edgewood Chemical Biological Center, Aberdeen Proving Ground, Maryland 21010-5424
Simple solutions of hydrogen peroxide; peroxide activators such as carbonate, bicarbonate, and molybdate; and organic cosolvents afford rapid, broad-spectrum decontamination of chemical warfare agents, even at low temperatures (-30 °C). Such solutions are nontoxic, noncorrosive, and environmentally friendly. With bicarbonate activator, the decon solution can be comprised solely using food-grade materials. In situ generation of peroxy anion OOH- effects perhydrolysis of the nerve agents O-ethyl-S-[2-(diisopropylamino)ethyl]-methylphosphonothioate (VX) and pinacolyl methylphosphonofluoridate (GD or Soman) to yield nontoxic products. For the blister agent bis(2-chloroethyl) sulfide (HD or mustard), peroxo species HCO4- and Mo(OO)42- afford oxidation, initially, to the nonvesicant sulfoxide. The U.S. Army is developing environmentally friendly decontamination systems to replace current, problematic decontaminants such as hypochlorite.1 Desirable characteristics for the replacement include maintaining a broad-spectrum reactivity toward all agents, even in cold-weather operations, while achieving a significant reduction in the corrosive and environmentally harmful nature of the decontaminant. Current decontaminants are corrosive and, furthermore, produce undesirable reaction products for bis(2-chloroethyl) sulfide (HD or mustard) that retain irritant and/or vesicant properties.1,2 In industrial applications, environmental concerns have been driving the replacement of chlorine-based bleaching processes with peroxide-based systems.3 These “green” peroxide strategies avoid the formation of toxic, carcinogenic chlorinated organic compounds such as those produced in paper production.4 In this communication, we show that peroxide-based systems can also be employed in military applications, replacing historical chlorine-based “bleach” decontaminants and others.1 Such systems afford the necessary rapid reactions and, as in the case of industrial bleaching, avoid undesirable products. We call this fledgling but promising peroxide-based decontaminant “decon green.”5 Another advantage of peroxides is evident for the development of cold-weather decontamination solutions: the freezing point of 50% H2O2 is -40 °C. Previously, Menger and Rourk6 demonstrated microemulsion formulations utilizing 30% H2O2. These microemulsions did not freeze or phase separate at -18 °C and were effective against a variety of CW simulants. Similarly, we find solutions formulated with 50% H2O2 do not freeze, phase separate, or precipitate activators down to at least -50 °C (see below). * Corresponding author. Tel.: (410) 436-8468. Fax: (410) 436-7317. E-mail:
[email protected]. Address: U.S. Army ECBC, Attn: AMSSB-RRT-CA, APG, MD 21010-5424.
Scheme 1
Basic peroxide has been known to rapidly decontaminate isopropyl methylphosphonofluoridate (GB or Sarin), 1, for decades,7,8 via generation of the powerful nucleophile peroxy anion, OOH-. This reaction is shown in Scheme 1. We have observed the long-suspected7 peroxyphosphonate intermediate, 1a, using 31P NMR analysis for both GB and pinacolyl methylphosphonofluoridate (GD or Soman), which yield peaks at 42.2 and 41.6 and 41.0 ppm (two diasteriomers), respectively. In support of the decomposition mechanism proposed for the peroxyphosphonate intermediate, Larsson8 notes that the GB reaction consumes 2 mol of H2O2 and evolves 1 mol of O2. Representative reactions for GB are shown in Table 1. GB in neutral peroxide (solution 1) exhibits an initial half-life of 67 h, apparently reacting with the background OOH-.9 Yet, the reaction gradually slows prior to completion as the pH and concentration of OOH- drop. However, with even small amounts of bicarbonate (solution 2), the reaction rates for both GB and GD become too fast to measure by NMR spectroscopy (t1/2 , 1 min) and go to completion. Although perhydrolysis is indeed fast, G agents are also easily decontaminated by dilute alkali,1 and so, peroxide offers no real advantage for these agents. Quite recently, however, it was found that O-ethylS-[2-(diisopropylamino)ethyl]-methylphosphonothioate (VX), 2, also undergoes rapid perhydrolysis to yield
10.1021/ie010732f CCC: $22.00 © 2002 American Chemical Society Published on Web 03/15/2002
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Ind. Eng. Chem. Res., Vol. 41, No. 8, 2002
Table 1. Half-Lives Observed for VX, GB, and HD t1/2a solution
activators
peroxide
1 2 3 4 5 6 7
none 0.037 M NaHCO3 0.1 M NaHCO3 0.1 M NaHCO3 0.1 M NaHCO3 0.1 M NaHCO3 0.33 M NaHCO3
8
0.75 M NaHCO3
9
0.2 M KHCO3
1.3 mL of 30% H2O2b 1.3 mL of 30% H2O2b 1.3 mL of 50% H2O2g 1.3 mL of 50% H2O2g 1.3 mL of 50% H2O2g 1.3 mL of 50% H2O2g 1.0 mL of 50% H2O2h 0.743 g of urea‚H2O2i in 1 mL of H2O 0.5 mL of 50% H2O2j
10 11
0.1 M KHCO3 + 0.1 M K2CO3 0.1 M KHCO3 + 0.1 M K2CO3 + 0.01 M K2MoO4
0.5 mL of 50% H2O2j 0.5 mL of 50% H2O2j
VX (0.01 M)
GB (0.01 M)
HD (0.1 M)
1.9 mL of t-BuOH 1.9 mL of t-BuOH 1.9 mL of t-BuOH 1.9 mL of EtOH 1.9 mL of i-PrOH 1.9 mL of PPG-425 1.0 mL of t-BuOH
.16 hc,d 120 mind 11 mind 56 sd
29 days
