Effect of Drop Size on the Degradation of VX in Concrete

Wagner, George W.; O’Connor, Richard J.; Edwards, Jennifer; Brevett, Carol A.

doi:10.1021/la036387b

Cited by 44 publications

(48 citation statements)

References 7 publications

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“…A detailed analysis of the degradation of specific adsorbate populations was considered impractical since, at least for slowly decomposing samples, the VX population in the macropores probably declines by migration into the micropores, as mentioned above. Previously, migration times 1 -20 d (9) t0.9/t0.5 1.8-2 (4) 12, 96 (2) 6, 96 (2) 1.1-1.5 (2) 2.5-50 (4) 3-8 (8) a Carbon granule diameters were 0.1-2.8 mm. Data are divided into subgroups for readability (see text).…”

Section: Scheme 1 Decomposition Of Vx On Activated Carbonmentioning

confidence: 98%

Decomposition of Adsorbed VX on Activated Carbons Studied by ³¹P MAS NMR

Columbus

Waysbort

Shmueli

et al. 2006

Environ. Sci. Technol.

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The fate of the persistent OP nerve agent O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX) on granular activated carbons that are used for gas filtration was studied by means of 31P magic angle spinning (MAS) NMR spectroscopy. VX as vapor or liquid was adsorbed on carbon granules, and MAS NMR spectra were recorded periodically. The results show that at least 90% of the adsorbed VX decomposes within 20 days or less to the nontoxic ethyl methylphosphonic acid (EMPA) and bis(S-2-diisopropylaminoethane) {(DES)2}. Decomposition occurred irrespective of the phase from which VX was loaded, the presence of metal impregnation on the carbon surface, and the water content of the carbon. Theoretical and practical aspects of the degradation are discussed.

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Section: Scheme 1 Decomposition Of Vx On Activated Carbonmentioning

confidence: 98%

Decomposition of Adsorbed VX on Activated Carbons Studied by ³¹P MAS NMR

Columbus

Waysbort

Shmueli

et al. 2006

Environ. Sci. Technol.

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“…The reaction was first-order with observed half-lives of over a month for pH values of 7 and below, the addition of base increased the rate of the reaction, and at a pH value of 13.5, the half-life of VX was 3 min. The phosphorus-derived products were EMPA, EA-2192, and O-ethyl methylphosphonothioic acid (CH 3 P(O)-(OC 2 H 5 )SH, EMPT); the sulfur-derived products were diisopropylaminoethanethiol (DESH, HSCH 2 CH 2 N(isoPr) 2 . Although the initial rate of VX degradation was faster with 2% added water, the reaction needed 8% water to proceed to completion.…”

Section: Introductionmentioning

confidence: 99%

Evaporation and Degradation of VX on Silica Sand

et al. 2009

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The evaporation and degradation of VX (O-ethyl S-[2-N,N-(diisopropylamino)ethyl] methylphosphonothioate) on silica sand and borosilicate glass were measured using vapor analysis and 31 P solid state magic angle spinning nuclear magnetic resonance (SSMAS NMR) spectroscopy. 31 P SSMAS NMR studies of VX degradation on crushed glass, air-dried sand, and oven-dried sand at a variety of temperatures showed that the final product was nontoxic ethyl methylphosphonic acid (EMPA), produced via the toxic diethyl dimethylpyrophosphonate intermediate. The reaction exhibited a lag time that depended upon the quantity of water and EMPA that were present in the initial sample of VX and was autocatalytic; EMPA was both the catalyst and product for the degradation of VX. 31 P SSMAS NMR studies of VX on moist sand at a variety of temperatures showed that the final product was nontoxic EMPA; observed intermediates were protonated VX, O-ethyl methylphosphonothioic acid, and toxic EA-2192 (S-[2-N,N-(diisopropylamino)ethyl methylphosphonothioic acid). The VX degradation mechanism differed on the moist and dry surfaces; the activation energies were 80 kJ/mol on moist sand and ∼46 kJ/mol on glass, air-dried, and oven-dried sand. The VX degradation rate was 5 to 9 times slower on moist sand than on air-dried sand. Analysis of the vapor emitted showed that the maximum vapor concentration coincided with the maximum surface area of the droplets, which was at ∼300 min. After four days, no further change in the concentration of vapor emitted was detected; approximately 9% of the incident VX drop on sand and ∼60% of the incident VX drop on glass had been recovered as VX vapor.

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“…Some liquids may go through a solidification process that will eventually make less liquid phase available to the pores [5][6][7]. In addition, chemical reactions in either the vapor or liquid phases may exist that can contribute to the fate of droplets [8,9]. Spread dynamics is influenced by the porous medium thickness, where two-and three-dimensional flows occur.…”

Section: Introductionmentioning

confidence: 99%