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APPENDIX D Agent Neutralization by Hydrolysis Five of the seven technology packages include the destruction of chemical agents by purely chemical re- actions that reduce the agents to less toxic or nontoxic products. Four of the five propose neutralization via hydrolysis with an aqueous alkali solution. Hydrolysis is a reaction of a target compound with water, an acid, or a base in which some chemical bond is broken in the target and OH- or H+ is inserted into the bond cleavage. The destruction of chemical agent via hydrolysis is of- ten referred to as chemical neutralization. The military definition of neutralize is to render something unus- able or nonfunctional. Technically, neutralization is a chemical reaction between an acid and a base to form a salt and water. Chemical agents are neither acids nor bases, however, and the use of the term neutralization for two very different processes is somewhat confus- ing. Nevertheless, in the literature on chemical demili- tarization, the terms neutralization and hydrolysis have been used interchangeably. Therefore, unless otherwise specified, neutralization refers to the destruction of chemical agent via hydrolysis. BACKG ROU N D Agent detoxification has been an essential require- ment since the introduction of mustard in World War I. Detoxification is used for decontaminating dispersed chemical agents on the battlefield, as well as in labora- tories, production plants, and elsewhere. Many types of reactions can detoxify chemical agents, but only two are widely used: nucleophilic substitution (e.g., hydrol- ysis) and oxidation. The literature is very extensive on the neutralization of mustard but much less extensive 203 on the neutralization of nerve agents (ERDEC, 1996, 1997~. In general, work on agent decontamination has identified several problems and the need for more re- search in the following areas: Chemical agents are nonpolar compounds, but most decontaminating reagents are polar, which leads to solubility problems. HD (mustard) is very insoluble in water; VX is somewhat soluble in water at low pH but not at high pH; GB is reason- ably soluble in water. Thus, the reaction takes place only at the phase interfaces, and vigorous stirring to achieve the desired reaction rates. Thickeners have been used in some mustard for- mulations, and some agents have thickened into gels by some unknown decomposition or polymer- ization process while in storage. (Gelling occurs most often for mustard HD and, to a lesser extent, for GB.) Investigations to develop decontamination meth- ods were generally limited to room-temperature reactions because decontamination is usually per- formed at ambient temperatures. Higher tempera- tures, which are feasible for the destruction of bulk agent, were not investigated. Decontamination is generally carried out by flood- ing the surface or the liquid with a large excess of decontamination liquid (e.g., 100 to 1~; for the de- struction of bulk agent, this amount of liquid would create an unnecessarily large hazardous- waste disposal problem. Major studies on chemical-neutralization (NRC, 1993; Yang, 1995) are summarized in Table D-1. Because

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204 ALTERNATIVE TECHNOLOGIES FOR DEMILITARIZATION OF ASSEMBLED CHEMICAL WEAPONS TABLE D-1 Examples of Large-Scale Neutralizations Country AgentQuantity (tons) Reactant Temperature Disposal Period/Rate United States Sarin (GB)4,000 Aq NaOH Ambient RCRAa hazardous 1973-1976 landfill Russia Sarin, Soman,3,000 HoCH2CH2NH2 100C Incineration 1980-1990 mustard 600 Lreactorb @ 20t/a V-typeC30 H3PO4 and EGO 140C Incineration 1980-1990 600 L reactors @ 20t/a Canada Mustard700 Ca(OH)2 8t batch 95C Incineration 1974-1976 VX, Tabun,e0.3 20% KOH inMeOH Ambient Incineration 4 months Soman intermittent United Kingdom Sarin20 20% NaOH 250 kg Ambient Discharged at depth 1967-1968 per batch into coastal sea Iraq Sarin, GFe70 Aq NaOH Ambient Discharged to 1992-1993 lined pit @ 1 ton/day aResource Conservation and Recovery Act. bA mobile reactor known as the KUASI system. CA VX analog: MeP(O)(OCH2CHMe2)(S(CH2)NEt2). dEthylene glycol, (EG). eTabun is (Me2N)P(O)(OC2Hs)CN; OF is MeP(O)(OR)F where R = cyclohexyl. Source: Adapted from NRC, 1993; Yang, 1995. the hydrolysis technologies proposed for the As- sembled Chemical Weapons Assessment (ACWA) all start with either NaOH-solution (three proposals) or KOH-solution (one proposal) for nerve agents and wa- ter for mustard (four proposals), the discussion below is limited to agent detoxification with these materials. Aqueous systems have some obvious advantages: reduced fire and other chemical hazards; a more sub- stantial research basis than for other reagents; and a smaller volume of organic material to dispose of. HYDROLYSIS OF GB Basic aqueous solutions react readily with GB by the following reaction: o 11 (CH3)2CHO P F + 2NaOH 1 CH3 sarin (GB) o 11 (CH3)2CHO P O~ + 2 Na + H2O + F (1) 1 CH3 isopropyl-methylphosphonic acid Yang (1995) states that, "The reaction is a bimo- lecular displacement (SN 2 (P)) of F- by OH- to produce the phosphonate anion." The rate can be high; the sec- ond-order rate constant at 25C (77F) is 25 (molarity- sec)~1 (Gustafson and Martell, 1962~: d [GB] = -25~0H] [GB] dt where the brackets represent concentration. Assuming caustic is maintained at 0.1 molar, the concentration of GB should be reduced one million-fold in 5.5 seconds. Sarin is soluble in water, although the exact solubil- ity limit does not appear to have been reported. It has been reported, however, that a 1: 1 volume mix of sarin and water was immediately miscible (Reeves and Macy, 1947~. Alcohol (methanol or ethanol) is some- times added to keep the GB in solution. Excess NaOH or KOH is required to maintain the high pH. A typical impurity in GB is a diester: o 1l/O (isopropyl) H3C P.\ O (isopropyl) If the pH of the final solution falls below 7, this diester can react with fluoride ion to reform GB (Beaudry et al., 1993~. The reaction is very slow, however.

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APPENDIX D TABLE D-2 Effect of pH on Equilibrium of Remaining GB GB pH Moles/L ng/L 3 0 9 8 lo-l 10-4 10-5 lo-6 10-~9 10-13 10-11 10-9 1.4 x 10-8 0.014 .4 40 Excess NaOH is also required to ensure the "com- plete" conversion of GB. The estimated equilibrium constant, Ke, for the hydrolysis reaction is (Harris et al., 1982~: K = [IMP][F ~ = 1Oi9 [GB] [OH ~ where tIMP] is the concentration of the isopropyl methylphosphonate (IMP) ion; EF-] is the concentra- tion of fluoride ion; [OH-] is the concentration of hy- droxyl ion; and KGB] is the concentration of GB re- maining. All concentrations are in gram-moles per liter. This equilibrium constant was calculated from elemen- tal reaction rates (see Harris et al., 1982~. The effect of pH on the amount of GB remaining in solution has been calculated based on this equilibrium constant (see Table D-2. For this calculation it was assumed that the IMP and F- concentrations were 0.1 molar each. The calculation suggests that the pH must be maintained at 9 or more for the GB to be re- duced to below the detection level. (Note: The equilib- rium quoted above has been questioned [Ward, 1998a], but it is certain that GB can reform at low pH at about the levels suggested in Table D-2. An alternative ex- planation for the reformation of GB at low pH is the reaction of the diester impurity.) Isopropyl methyl- phosphonic acid, the major product of the hydrolysis of GB, is a Schedule 2 compounds and must be irre- versibly destroyed to meet the requirements of the Chemical Weapons Convention (CWC). Military grade GB is not very pure. Early lots (1 to 241) were manufactured to a specification of 92 per- cent and were distilled. Later lots (242 to 431) were manufactured to a specification of 88 percent and were iSchedule 2 compounds are defined as those that can be readily con- verted to chemical agent. Any high valence phosphorus compound with alkyl side chain in the range Cat to C4, iS considered a Schedule 2 compound. 205 not distilled (U.S. Army, 1996~. Stabilizers were added to all lots to retard degradation. The first stabilizer used was tributylamine (TBA); later, diisopropyl- carbodiimide (DICDI) was used. Some of the older GB has been found to contain crystalline material, believed to result from the TEA inhibitor. Some GB has been recovered, redistilled, and restabilized with DICDI. Thus, considerable variation in GB composition should be expected during the stockpile disposal program. The purity of GB at loading of weapons is reported to be between 73 percent and 93 percent. Hydrolysis of VX (described in the next section) produces a two-phase product: a small organic layer, which is reported to result primarily from the DICDI inhibitor, remains separate from the main aqueous phase. This same behavior has recently been reported from the hydrolysis of GB (Ward, 1998b). The organic layer amounts to approximately 2 to 5 percent of the original agent volume. The flash point of this organic layer has not been reported. During the large-scale disposal of satin at the Rocky Mountain Arsenal in 1973-1976 (Item 1 in Table D-1), GB apparently persisted in the brine at a very low level. The brine had to be certified to have less than 2 ng/ml (2 ppb w/v) of GB before going to a dryer, where the liquid was evaporated and the solid residue was pack- aged to be buried. Several explanations for the persis- tence of GB were offered (Harris et al 1982~. The one most generally accepted at present is a problem in the analytical procedure, with GB reforming during analy- sis. The analytical method now proposed by ERDEC is: extraction in chloroform at high pH (e.g., pH of 11), followed by gas chromatography (GC) and mass spec- trometry (MS). The extraction at high pH eliminates the problem of GB reforming. The problem was serious at the Rocky Mountain Arsenal because hydrolysis was the only process being used. A follow-up process is now required to eliminate the major Schedule 2 product (isopropl-methyl- phosphonic acid; see Eqn. 1~. This process could be used to ensure the complete destruction of low-level residual GB. Hydrolysis of GB has also led to a problem with formation of a solid precipitate believed to be sodium fluoride (Ward, 1998c), which has only limited solu- bility in water (i.e., about 4 percent). A ferrous oxide or hydroxide has also been suggested. GB hydrolysate,

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206 ALTERNATIVE TECHNOLOGIES FOR DEMILITARIZATION OF ASSEMBLED CHEMICAL WEAPONS provided by the Chemical Agent and Munitions Dis- posal Systems (CAMDS) for use by the ACWA tech- nology providers in their process demonstrations, was prepared in fairly dilute solution to avoid formation of the precipitates. The formulation used was 7 gallons of GB with 93 gallons of 5 percent NaOH solution in water. (This represents roughly 10 percent excess of NaOH solution in water and resulted in a pH between l l and 12.) The hydrolysate will probably be determined to be toxic when animal toxicity studies are completed (by analogy with VX-hydrolysate, below). Thus, it should be handled with care as a toxic material. HYDROLYSIS OF VX The hydrolysis of VX proceeds much more slowly than that of GB. In dilute solution, at 22C (72F): d[~X] = -5.2 x 10-3 [OH] [VX] dt The rate constant shown is 4,800 times smaller than that of GB. A reduction in concentration by a factor of one million would require more than 7 hours. The acti- vation energy for the reaction is given as 15.0 kcal/mol (at pH = 12~. Thus, increasing reaction temperature from 22C to 90C, for example, would increase the reaction rate by a factor of 117; the reaction time would be correspondingly reduced. The temperature chosen for hydrolysis of VX at Newport is 90C (194F). The rates quoted above are for VX in solution. How- ever, VX has very limited solubility at high pH. There- fore, the reaction rate will be limited by the mass-trans- fer rate between the two phases. As reaction proceeds, CH-P S CH-CH-N NaOH OCH2 CH3 VX the products (see Figure D-1), which are soluble in water, increase the solubility of the remaining VX. In development work performed for Newport, vigorous stirring was used to disperse the two phases. The major reactions in the neutralization process are shown in Figure D-1. The overall reaction requires more than 2 moles of NaOH per mole of VX to neutral- ize the ethyl methylphosphonic acid (EMPA) and me- thyl phosphoric acid (MPA), as well as the thiolamine, and to maintain a high pH. VX exhibits behavior simi- lar to GB: if the pH of the product solution is allowed to drop, VX will reform. Approximately 90 percent of the VX reacts directly (by the top reaction), breaking the P-S bond to form the sodium salt of EMPA and the his (isopropyl) amino ethyl thiol ("thiolamine"~. How- ever, about 10 percent of the VX reacts by a second channel in which the P-O bond is cleaved to form the intermediate compound shown as EA2192, which is itself highly toxic but will react slowly to form MPA and more thiolamine. EA2192 is hydrolyzed at least ten times more slowly than VX. About six hours at 90C (194F) are required for adequate destruction. Most of the products are soluble in aqueous NaOH, but a small residue, arising mainly from a stabilizer added to the original VX, remains as an insoluble or- ganic layer less dense than water. The organic layer is flammable with a flash point of 53C (127F) (ERDEC, 1998~. This should be recognized as a hazard in carry- ing out the reaction at 90C (194F). Military grade VX is 90 to 95 percent pure; a typical analysis is shown in Tables D-3 and D-4. The agent analysis was obtained by GC with a thermal conduc- tivity detector. The other organic components were 'CH(CH3~2 ~13% ~ ~NaOH ~ -CH3CH2 OH ~/ CH(CH312 CH3 P O~Na++ Na+ ~S CH2-CH2-N O CH2CH3 EMPA slow'| -CH3CH2OH Thiol CH(CH3~2 /CH(cH312 0 ,CH(CH3~2 CH3 P-S-CH2 CH2 N ~ CH3 P-ONa++Na+~S-CH2-CH2-N O~Na+ \CH(CH3~2 O~ Na+ CH(CH3~2 EA 2192 MPA Thiol FIGURE D- 1 Primary reactions involved in VX hydrolysis. Source: Yang et al., 1992; NRC, 1996.

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APPENDIX D TABLE D-3 Results of the VX Ton Container Survey Program (Organics~a Organic Compounds Mole % VX S. S' bis(2-diisopropylaminoethyl) methylphosphonodithiolate Dimethyl ketone (acetone) Diisopropylamine N. N-diisopropylmethylamine Diisopropylcarbodiimide (stabilizer) N. N-diisopropylethylamine O-ethyl methylethylphosphinate 1, 3-diisopropylurea Diethyl methylphosphonate 2-(diisopropylamino)ethane thiol O. O-diethyl methylphosphonothiolate O. S-diethyl methylphosphonothiolate 2-(Diisopropylamino)ethyl ethyl sulfide Diethyl dimethylpyrophosphonate (pyro) O. O-diethyl dimethylpyrophosphonothioate 0-(2-diisopropylaminoethyl) O-ethylmethylphosphonate (QB) 1, 2-bis (ethyl methylphosphonothiolo)ethane Unknowns Total 95.700 0.135 0.004 0.103 0.003 1.190 0.004 0.021 0.004 0.041 0.065 0.098 0.046 0.081 0.072 0.124 0.170 0.450 0.500 00.000 aAnalyzed by gas chromatography/mass spectroscopy (GC/MS). Source: U.S. Army, 1997a. analyzed by GC with an electron-impact mass selec- tive detector. Metal analysis was performed with in- ductively-coupled plasma/atomic emission spectros- copy (ICP/AES ). Mercury was analyzed by cold-vapor atomic absorption. The largest "impurity" listed is DICDI, which was added to the VX as a stabilizer (antioxidant). Its con- centration can be as high as 5 percent. The other TABLE D-4 Results of the VX Ton Container Survey Program (Metals~a Metal Analytical Result (ppm) Arsenic Chromium Lead Selenium Zinc Mercury Copper Iron Magnesium Calcium Barium 6.700 1.200 0.370 3.600 4.400 0.130 0.500 17.000 4.200 28.000 0.031 aAnalyzed by inductively coupled plasma (ICP) spectrometry. Source: U.S. Army, 1997a. 207 impurities shown are present at large parts-per-million (ppm) concentrations; many impurities in the parts-per- billion (ppb) range would probably be found with more sensitive analytic techniques. The aqueous phase contains most of the product, about 95 percent; the organic layer has approximately 5 percent of the total. The compositions of the two product phases will, of course, be quite different. A typical composition for the total mixture (obtained by "homogenizing" the two phases) is shown in Table D-5. The analysis was based on 13C and 3lP nuclear mag- netic resonance spectrometry (NMR). The major products are those expected from the re- action sequence given in Figure D-1, together with nonreacted impurities expected from the initial compo- sition. Materials present at very low concentrations (e.g., ppm range or less) are not, in general, differenti- ated in the analysis. The exceptions are VX, shown in Table D-6 to be remaining to the ppb range, and EA 2192, in the ppm range. The hydrolysis product has an unpleasant odor, which can be mitigated by the addition of bleach after the hydrolysis reaction is complete. This may or may not be desirable, depending on the subsequent treat- ment planned for the material.

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208 ALTERNATIVE TECHNOLOGIES FOR DEMILITARIZATION OF ASSEMBLED CHEMICAL WEAPONS TABLE D-5 Analysis of Homogenized VX Hydrolysate after 240-Minute Reaction Timea Compound Formula Mole % EMPA (Ethyl methlyphosphonic acid) MPA (Methylphosphonic acid) EMPSH (O-Ethyl methylphosphonothioic acid) Other UP RSH (Diisopropylaminoethanethiol) RSSR (Bis [diisopropylaminoethyl] disulfide) RS R (B is [diisopropylaminoethyl] sulfide) RSCCSH (2- [diisopropylaminoethylthio] ethanethiol DIPA (Diisopropylamine) CDI (Dicyclohexylcarbodiimide) Other RS-compounds OP(CH3)(0 CH2 CH3) (OH) OF (CH3)(0H)2 SP(CH3)(0 CH2 CH3)(0H) Not applicable R'- SH R'- SS'R' R'- S - R' R1 - S1 - CH2 CH2SH HN[CH(CH3)2]2 C6Hll - N = C = N - C6H Not applicable 41.5 4.6 0.3 0.2 43.4 0.4 0.7 1.3 0.6 2.7 1.9 aAnalyzed by 13C and 31p nuclear magnetic resonance (NMR) spectroscopy. Source: U.S. Army, 1997b. VX was hydrolyzed at CAMDS to supply hydroly- sate for the ACWA technology provider demonstra- tions. This hydrolysate had a higher concentration than the GB hydrolysate. Thirty-three gallons of VX were mixed with 67 gallons of 20 percent NaOH solution in water to produce the hydrolysate. The primary purpose of the VX hydrolysis is to re- duce the material toxicity. Animal tests have been car- ried out to confirm the reduced toxicity. The intrave- nous LD50 value of VX for mice was reported to be 0.0141 mglkg. The hydrolysis product was 4 to 6 or- ders of magnitude less toxic. The characteristic signs of nerve agent attack were not observed with the hy- drolyzed material. The remaining toxicity is due to the salt and organic content of the samples. The major phosphorus products in the hydrolysate are considered to be Schedule 2 compounds; they must be irreversibly destroyed to meet the requirement of the CWC. In summary, the hydrolysis reaction can reduce the toxicity of the original VX by a large factor, 5,000-fold TABLE D-6 Residual VX and EA 2192 Concentrations from 12-Liter Reactor Tests Reaction Time (minutes) Homogenized Samples vxa EA 2192b 30 120 < 20 ppb < 20 ppb 65 ppm < 24 ppm aAnalyzed by GC/ion trap mass spectrometry (ITMS). bAnalyzed by 3~P NMR spec~oscopy. Source: U.S. Army, 1997b. to 25,000-fold. The product retains a low level of toxic- ity and will require further treatment before being re- leased to the environment. HYDROLYSIS OF HD The mustard stored at Aberdeen, Maryland, will be detoxified by hydrolysis with hot water (90C; 194F) followed by the addition of caustic. The overall desired reaction is: S\ ,CH, CH, C1 CH2 CH2 C1 + 20H- ~ S\ ,CH3 CH2 CH 'CH3 CH2 CH + 2C1 This overall reaction follows a complex series of steps, however, leading to several products. In addition, mili- tary grade mustard is usually impure (as low as 80 per- cent purity), and the impurities contribute to the com- plexity of the neutralized mix. There are several reasons for the two-step reaction sequence (hot water hydrolysis followed by addition of caustic). Hydrolysis with water is preferred because caustic produces vinyl compounds, which are consid- ered toxic and resist further treatment. The products of the aqueous hydrolysis are strongly acidic, and the pH must be adjusted for the subsequent treatment proposed for Aberdeen (biodegradation). Finally, the added caus- tic will react with a small amount of sulfonium salts, which are themselves toxic. A typical analysis of liquid mustard is shown in Table D-7 (based on GC/MS analysis). There are probably many more components present at lower

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APPENDIX D TABLE D-7 Typical Composition of HD Agenta 209 TABLE D-8 Concentration of Metals in HD Agenta Compound Mole %c Metal Content (ppm) HD Qb 2-chloroethyl 4-chlorobutyl sulfide 1, 4-dithiane 1, 2-dichloroethane Bis 3-chloropropyl sulfide 2-chloropropyl 3'-chloropropyl sulfide 2-chloroethyl 3-chloropropyl sulfide 1-chloropropyl 2-chloroethyl sulfide 1, 4-thioxane 91.38 6.08 0.86 0.81 0.35 0.18 0.18 0.14 0.02 <0.01 aAnalyzed by GC/MS. bQ is the following cyclic sulfonium compound: / CH2 CH2 \ CH2 CH2/ CImpurities may vary widely among ton containers containing HD. For example, in a survey of ton containers at Aberdeen (U.S. Army, 1996), the mole percent of 2-chloroethyl 4-chlorobutyl sulfide ranged from 0 to 2.32, for trichlorethylene it varied between 0 and 0.02. , S+ CH2 CH2 C1 Source: U.S. Army, 1996. concentrations (e.g., at the ppm level). The mustard also conta~ns small concentrations of metals (see Table D-8) the exact forms of which are not known. There is generally a residual "heel" in mustard con- tainers a gel that will not flow but that can be washed out. The heel can amount to more than 10 percent of the stored agent. Analyses of three heel samples are given in Table D-9. The heel also contains metals, in- cluding a large amount of iron (e.g., > 10,000 ppm as iron sulfide). Clean out of the ton containers containing HD leads to a small vapor stream that requires treatment prior to release. An analysis of a vapor sample is shown in Table D-10. Sim~lar vapors should be expected when cleaning out mustard-filled weapons. Aluminum Antimony Arsenic Barium Beryllium Bismuth Cadmium Calcium Chromium Cobalt Copper Iron Lead Magnesium Manganese Nickel Phosphorus Selenium Silicon Silver Sodium Sulfur Thallium Thorium Tin Vanadium Zinc < 13.0 <9.0 18.9 <0.3 <0.2 < 12.0 <3.0 9.6 <2.0 <2.0 91.8 5,035.0 <7.0 <0.4 0.6 <4.0 32.6 < 14.0 110.9 <4.0 < 16.0 264,420.0 < 13.0 < 11.0 <6.0 <3.0 <0.7 aAnalyzed by ICP spectrometry. Source: U.S. Army, 1996. Mustard is relatively insoluble in water, so the hy- drolysis reaction must occur at the interface. High- shear mixing has been used to speed up the reaction. The rate-determining step of the reaction with water was found to be the formation of an intermediate cyclic ethylene sulfonium ion: S\ CH2 CH2 C1 /CH2 + H+ + C1- ~ C1~H2~H2 S\ | + C1 CH2 CH2 CH2 C1 TABLE D-9 Complex Organic Compounds in HD Heel by NMR (mole percent~a Sample # Location HD Cyclic Sulfonium Ionb 1, 4-Dithiane Other C-03-04-HH-1936 Top of heel 53 42 C-03-05-HH-1936 Bottom of heel 33 60 C-03-06-HH-1936 Middle portion 14 86 aAnalyzed by ~H and ~3C NMR. bThe cyclic sulfonium ion is CH2 CH2\ \ CH2 CH2/ Source: U.S. Army, 1996. / S+ CH2 CH2 C1

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210 TABLE D-10 Content of HD Agent and Volatile Organic Compounds in Initial Ton Container Vapora Compound 1, 2-dichloroethane Bis-(2-chloroethyl) sulfide (HD) 1, 4-dithiane 2-Chlorobutane Tetrachloroethene aAnalyzed by GC/MS. Source: U.S. Army, 1996. ALTERNATIVE TECHNOLOGIES FOR DEMILITARIZATION OF ASSEMBLED CHEMICAL WEAPONS Concentration (mg/L) 6.000 0.830 0.600 0.210 0.083 This intermediate then reacts further, and a series of materials other than the expected thiodiglycol are formed. A suggested reaction pathway is shown in Figure D-2. In early work on mustard hydrolysis, HD could not be detoxified by hydrolysis. The rate of reaction was slow and was controlled by the rate of mass transfer. As shown in the reaction scheme of Figure D-2, sulfo- nium ion aggregates H-TG, CH-TG, and H-2TG were formed and could be stable; also, H-2TG was believed Main reaction CH2 CH2CI CH2 CH2 S/ - S+ CH2 CH2CI CH2CH2CI HD CH (Sulfur mustard) I (Chlorohydrin) Side reaction ~ +Thiodiglycol ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ /CH2 CH2CS+ S\ \ CH2CH2OH CH2 CH2CI H-TDG HOCH2CHp HOCH2 CH2 , CH2CH2OH / CH2 CH2OH ~H2O / CH2 CH2 C S\ S CH2 CH2OH CH2 CH2 OH \ ~Thiodiglycol / / \ / S+CH2 CH2 CH2 CH2S+ / \ / \ CH-TDG ,CH2 CH2OH \ / S CH2CH2OH H-2TDG *Brackets indicate transition states that are not directly observable. to be quite toxic. All of these observations were based on low-temperature hydrolysis with moderate stirring. With very vigorous high-shear m~xing and high tem- perature (90C; 194F), very complete hydrolysis, pri- marily to the desired thiodiglycol, has been achieved. Work at ERDEC using hot water for hydrolysis with NaOH solution added at the end of the reaction has reduced mustard to less than 20 ppb (the detection level); 99 percent of the mustard was converted to the thiodiglycol. The organic compounds in the hydrolysate at differ- ent times during the reaction after agent addition to the hot water, and after subsequent addition of NaOH- are shown in Table D- 1 1. (Only the major components were analyzed; there are undoubtedly many others at ppm-levels). The analysis of Table D- 1 1 does not show the chlorinated hydrocarbons present in the original mustard, which go through the hydrolysis reaction es- sentially unchanged. The hydrolyzed product remains toxic to some ani- mal species. For example, fathead minnows (a fresh- water species) showed an EC50 of 12 percent vol./volt ~H2OCH2CH2OH CH2-CH2 ~H2O CH2CH2OH S. ~S+ ~ S CH2CH2 Cl CH2CH2 OH CH2 CH2 OH TDG (Thiodiglycol) FIGURE D-2 Reversible formations of the sulfonium ion aggregates in the hydrolysis of mustard. Source: Yang et al., 1992; NRC, 1996.

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APPENDIX D TABLE Dell Organic Compounds in HD Hydrolysate (Mole Percent) Analysis of Residuals Compound 79 Minutes after End of HD Feed 63 Minutes after End of NaOH Addition TDG 90.70 91.20 CHTGb 1.70 0.05 Q OHC 2.50 3.40 1, 4-dithiane 0.50 0.80 Glycol o.so o.5o C6H~2SO2 compounds 2.10 2.20 Acetone 0.02 Not detected Other 2.00 1.80 aAnalyzed by OH NMR. bCHTG=HOCH2CH2-S-CH2CH2-S+-(CH2CH2OH)2 CQ-OH = HO CH2 CH2-S- CH2 CH2-S- CH2 CH2OH Source: U.S. Army, 1996. (i.e., a concentration of 12 vol. percent hydrolysate in water led to the death of half the test population.) Sheepshead minnows, a saltwater species, had a higher tolerance: EC50 of 80 percent vol./volt The difference in the tolerance level of the two species is probably due to the high salt content of the hydrolysate. The hydrolysis product is not acceptable for direct discharge and must be further treated. The major prod- uct (the thiodiglycol) is considered a Schedule 2 com- pound and must be irreversibly reacted to meet the re- quirements of the CWC. Recent work on HD has shown that hydrolysis at high temperature (90C; 194F) with vigorous mixing can successfully destroy the mustard. The product is not acceptable for discharge, however, without further treatment. REFERENCES Beaudry, W.T., J.H. Buchanan, D.K. Rohrbaugh, J.B. Samuel, L.L. Szafraniec, and J.R. Ward. 1993. Analysis of Decontamination Solution of G-agents to Detect Reformation of Agents. ERDEC- TR-005. January 1993. Aberdeen Proving Ground, Md.: Edgewood Research, Development and Engineering Center. ERDEC (Edgewood Research, Development and Engineering Cen- ter). 1996. HD Hydrolysis/Biodegradation Toxicology and Ki- netics. ERDEC-TR-382. December 1996. Aberdeen Proving Ground, Md.: Edgewood Research, Development and Engineer- ing Center. ERDEC. 1997. Neutralization and Biodegradation of Sulfur Mus- tard. ERDEC-TR-388. February 1997. Aberdeen Proving Ground, Md.: Edgewood Research, Development and Engineer- ing Center. 211 ERDEC. 1998. Material Safety Data Sheet, Revised August 1998. Aberdeen Proving Ground, Md.: Edgewood Research, Devel- opment and Engineering Center. Gustafson R.L., and A.E. Martell. 1962. Reaction of Sarin with NaOH. Journal of the American Chemical Society 84: 2309- 2316. Harris, J.M., K. DeBruin, J.E. Gebhart, B.C. Garrett, and T.M. Prociv. 1982. GB-NaOH Neutralization Mechanism and Ana- lytical Procedures Evaluation. DRXTH-SE-CR-82161. May 1982. Arberdeen Proving Ground, Md.: U.S. Army Toxic and Hazardous Material Agency. NRC (National Research Council). 1993. Alternative Technologies for the Destruction of Chemical Agents and Munitions. Board on Army Science and Technology. Washington, D.C.: National Academy Press. NRC. 1996. Review and Evaluation of Alternative Chemical Dis- posal Technologies. Board on Army Science and Technology. Washington, D.C.: National Academy Press. U.S. Army. 1996. Chemical Reaction Analysis Report: Literature Search and Analysis of M28 Propellant Decomposition and Potential Reactions of GB and VX Nerve Agents with Propel- lant. Aberdeen Proving Ground, Md.: Program Manager for Chemical Demilitarization. Reeves, A.M., and R. Macy. 1947. Hydrolysis of Agents GB and GE. TGIR No. 369. Project A1.13. Washington, D.C.: U.S. Army. Ward, R. 1998a. Personal communication from R. Ward, Edgewood Research, Development, and Engineering Center, to Walter May, National Research Council Committee on Review and Evaluation of Alternative Technologies for Demilitariza- tion of Assembled Chemical Weapons, July 15, 1998. Ward, R. 1998b. Personal communication from R. Ward, Edgewood Research, Development, and Engineering Center, to Walter May, National Research Council Committee on Review and Evaluation of Alternative Technologies for Demilitariza- tion of Assembled Chemical Weapons, July 20, 1998. Ward, R. 1998c. Personal communication from R. Ward, Edgewood Research, Development, and Engineering Center, to Walter May, National Research Council Committee on Review

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212 ALTERNATIVE TECHNOLOGIES FOR DEMILITARIZATION OF ASSEMBLED CHEMICAL WEAPONS and Evaluation of Alternative Technologies for Demilitariza- tion of Assembled Chemical Weapons, November 16, 1998. U.S. Army. 1996. Ton Container Decontamination and Disposal Program Demonstration Report: A Second Mustard Ton Con- tainer (TC Serial #D94102~. Aberdeen Proving Ground, Md.: Program Manager for Chemical Demilitarization. U.S. Army. 1997a. Project Information Package for the Newport VX Chemical Agent Disposal Facility. Aberdeen Proving Ground, Md.: Program Manager for Chemical Demilitarization. U.S. Army. 1997b. Neutralization of VX Nerve Agent with So- dium Hydroxide: 12-liter Mettler Test Report. Aberdeen Prov- ing Ground, Md.: Program Manager for Chemical Demilitariza- tion. Yang Y.-C. 1995. Chemical Reactions for Neutralizing Chemical Warfare Agents. Chemistry and Industry 9: 334-337. Yang Y.-C., J.A. Baker, and J.R. Ward. 1992. Decontamination of chemical warfare agents. Chemistry Review 92: 1729-1743.