From the Decomposition of Chemical Warfare ... - ACS Publications

Article Cite This: Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

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From the Decomposition of Chemical Warfare Agents to the Decontamination of Cytostatics Václav Štengl,*,†,‡ Martin Št’astný,†,§ Pavel Janoš,§ Karel Mazanec,∥ José Luis Perez-Diaz,⊥ and Irena R. Štenglová-Netíková‡ Department of Material Chemistry, Institute of Inorganic Chemistry ASCR v.v.i., 250 68 Husinec-Ř ež, Czech Republic Department of Oncology,first Faculty of Medicine, Charles University in Prague, Kateřinská 32, Praha 2 128 00, Czech Republic § Faculty of the Environment, J. E. Purkyně University in Ú stí nad Labem, Králova Výsǐ na 7, 400 96 Ú stí nad Labem, Czech Republic ∥ Military Research Institute, Veslařská 230 637 00 Brno, Czech Republic ⊥ EPS Universidad de Alcala, Alcala de Henares 28805 Madrid, Spain † ‡

S Supporting Information *

ABSTRACT: The ability of pilot samples of destructive metal oxide sorbents to decompose a sulfur mustard-type chemical warfare agent into nontoxic products in a nonaqueous solvent was compared with that of the commercial product FAST-ACT. Additionally, samples of the destructive metal oxide sorbents were used to decompose nitrogen mustards, which are used as chemotherapeutic agents, in water, and the results were compared with those of FAST-ACT. All the prepared pilot samples exhibited stoichiometric activities, i.e., the degradation rate expressed by the rate constant, k [s−1, min−1], and the decomposition efficiencies, which are expressed by the degree of conversion d [%], higher than those of the comparative commercial product FAST-ACT. Scaling up the sulfur mustard decomposition from the laboratory conditions (reaction volume, 4 L) to quarteroperating (pilot) reaction conditions (reaction volume, 100 L) had a positive effect on the reaction and final product.

1. INTRODUCTION

In the following years, we attempted to increase the stoichiometric activity of titanium dioxide by doping it with Ge4+,9 Zr4+,10 and Mn4+11 and with mixed oxides, Ti−Fe12 and Ti−Mn,13 using manganese(IV) oxide,11 Mn−Fe,14 or their graphene oxide composites.15 A sample of Ce3+/4+O2 was prepared via homogeneous hydrolysis of cerium(III) nitrate and direct precipitation of an aqueous solution of cerium(III) nitrate with an excess of ammonium bicarbonate. The excellent degradation activity with respect to soman and VX is mainly due to the defects in the crystal lattice caused by the Ce3+ atoms.16 These nanostructured materials are expected to be applicable to the decontamination of sensitive military technology components in nonaqueous environments. Nano-

Metal oxides can decompose hazardous substances on their surfaces. However, this reaction is relatively slow and not usable for practical applications. However, if the particle size is reduced to the nanoscale, then the reaction rate and ability to decompose hazardous substances increase. The first articles1,2 on the decomposition of hazardous substances were published in 1990. A supercritical drying method was used, and light metal nano-oxides, such as Ca,3 Mg,4 and Al,5 were prepared. Nanoscale MgO with a higher detoxification activity was prepared by Štengl et al.6 in toluene using a supercritical drying method. Utamapanya et al.7 first used the term “destructive sorbents” for these nanoscale metal oxides. Using the homogeneous hydrolysis of titanium(IV) oxo-sulfate and iron(III) sulfate, nanoscale anatase and ferrihydrite were synthesized in an aqueous solution and were used to decompose sulfur mustard, soman, and VX.8 © XXXX American Chemical Society

Received: October 12, 2017 Revised: January 10, 2018 Accepted: January 23, 2018

A

DOI: 10.1021/acs.iecr.7b04253 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

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Industrial & Engineering Chemistry Research

soman, and VX agent. Then, we tested a new family of decontamination agents based on hafnium-doped TiO2 in a nonaqueous solution (n-hexane) and new destructive sorbents based on titania for the degradation of cytostatic nitrogen mustards in an aqueous solution. Furthermore, this nanomaterial is already being tested in an EU project called COUNTERFOG to assess its role as a counter measurement against chemical warfare contaminants coupled with fog. The preliminary results demonstrate that the nanomaterial physicochemically catalyzes the hydrolysis of the chemical contaminant via surface interactions between the water dissolution (fog) and the chemical warfare agent.22 In this publication, we compare the stoichiometric degradation of the chemical warfare agents soman, VX, and sulfur mustard (yperite) and their derivates, e.g., nitrogen mustards, cyclophosphamide, and ifosfamide, on reactive sorbents based on TiO2 prepared under quarter-operating (pilot) conditions.

structured oxides have also been tested for the degradation of organophosphorus pesticides, such as parathion-methyl17,18 and trimethyl phosphate.19 Štengl et al.20 presented a possible method for decontaminating a VGA circuit board from sulfur mustard using n-hexane as a reaction medium. The degradation reactions of all these destructive sorbents occur in nonaqueous environments.11 Sulfur mustard, commonly known as yperite, is a prototypical substance from the sulfur-based family of cytotoxic and vesicant chemical warfare agents. By replacing the S atom with an N atom, a family of nitrogen mustards can be derived; see Figure 1. HN2, mustine, and bis(2-chloroethyl) methylamine were the

2. EXPERIMENTAL SECTION All of the used chemicals, titanium oxo-sulfate (TiOSO4), zirconium(IV) chloride (ZrCl4), hafnium(IV) chloride (HfCl4), aluminum(III) sulfate (Al2(SO4)3.16H2O), urea (CO(NH2)2), and sulfuric acid (H2SO4), were purchased from Sigma-Aldrich, and the drugs cyclophosphamide and ifosfamide were obtained from EBEWE Pharma. The homogeneous hydrolysis of titanium oxo-sulfate with urea was used for the titanium(IV) dioxide synthesis. The chemical warfare agents used for tests were prepared at the Military Research Institute (Brno, Czech Republic) with the following purities: (i) VX, O-ethyl S-[2(diisopropylamino)ethyl] methylphosphonothioate, 91.6%; (ii) soman, O-pinacolyl methylphosphonofluoridate, or GD, 94.0% and (iii) sulfur mustard, bis(2-chloroethyl) sulfide, or HD, 96.5%. 2.1. Synthesis of Titania. 2.1.1. Pilot Sample G253. In a typical synthesis, 4 kg of TiOSO4 was dissolved in 30 L of warm distilled water acidified with 0.160 L of 98% H2SO4 in a 150 L double-walled glass boiler for indirect heating (duplicator, see Figure 2). Once the titanium oxo-sulfate was dissolved in the pellucid solution, 16 kg of urea was added. Next, distilled water was added to reach a total reaction volume of 100 L. The mixture was heated at 100 °C with stirring for 6 h until the pH reached 7.2. The gained precipitate was washed via decantation in two 50 L barrels until a conductivity of 10 μS was reached, filtered, and dried at 105 °C. 2.1.2. Pilot Sample G065. In this synthesis, 50 L of 53.1 g of Ti/L titanium oxo-sulfate and 38.8 kg of urea was added into a 150 L duplicator. Next, distilled water was added to reach a total reaction volume of 100 L. The mixture was heated at 100 °C with stirring for 6 h until the pH reached 7.2. The obtained precipitate was washed via decantation in two 50 L barrels until the conductivity reached 10 μS, filtered, and dried at 105 °C. 2.1.3. Pilot Sample G284. To synthesis this sample, 4 kg of TiOSO4 was dissolved in 30 L of warm distilled water that was acidified with 0.160 L of 98% H2SO4 in a 150 L duplicator. Once the titanyl oxo-sulfate was dissolved in the pellucid solution, 400 g of aluminum(III) sulfate and 16 kg of urea were added. Next, distilled water was added to reach a total reaction volume of 100 L. The mixture was heated at 100 °C with stirring for 6 h until the pH reached 7.2. The resulted precipitate was washed via decantation in two 50 L barrels until the conductivity reached 10 μS, filtered, and dried at 105 °C. 2.1.4. Pilot Sample G015. In this synthesis, 300 g of TiOSO4 was dissolved in 10 L of warm distilled water acidified with

Figure 1. Overview of nitrogen mustards.

first anticancer chemotherapeutics. Mustine was developed after a war accident in 1943 in Bari, Italy, where civilians and soldiers were exposed to sulfur mustard. The survivors had a reduced number of lymphocytes, which is useful for the possible treatment of lymphomas. The nitrogen mustards that can be used as warfare agents include HN1, bis(2-chloroethyl)ethylamine, and HN3, tris(2-chloroethyl)amine. Other nitrogen mustards, e.g., cyclophosphamide, ifosfamide, uramustine, melphalan, bendamustine, and chlorambucil, are used as chemotherapeutic agents for the treatment of different kind of cancers. Cytostatics are chemotherapeutic agents used for the treatment of cancer. Cytostatics from the group of nitrogen mustards are alkylating agents. Their active metabolites bind to nucleophile sites of DNA and cause its breaks. This lead to the cell death via apoptosis. Cytostatics generally have mutagenic, cancerogenic, and reproduction affecting effects, which are caused by their changes in DNA. This so-called MCR effect is potentially dangerous for healthcare staff in oncological departments. Precise decontamination of the working environment is essential for staff and patients safety.The potential for using titanium(IV) dioxide as a new, efficient, and cheap material for the complete decontamination of anthracycline antibiotics in water. This pioneering study introduced titanium(IV) dioxide as a promising alternative method for cytostatics decomposition. In this paper, we compare the degradation activity of pilot samples based on titanium(IV) oxide with that of the only commercial product, FAST-ACT (http://fast-act.com), for the decomposition of warfare agents, such as sulfur mustard, B


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a conventional X-ray tube (Cu Kα radiation, 30 kV, 10 mA) and the LYNXEYE 1-dimensional detector was used for determination of the crystal phases using DiffracPlus Topas and Eva software (Bruker AXS).The morphology of powder samples, dispersed in ethanol and air-dried on silicon wafer chips, was investigated with FEI Nova NanoSEM 450 scanning electron microscope (SEM) in a high-vacuum mode at 5 kV acceleration voltage. Low-temperature nitrogen physisorption was employed for the surface area (BET method) and porosity (BJH method) measurements, using the Coulter SA3100 (Beckman) instrument. The samples were outgassed at 150 °C for 1 h prior measurements. 2.2.1. GC Method for the Decomposition of Chemical Warfare Agents (CWAs) in n-Hexane. The decompositions of sulfur mustard, soman, and VX on the reactive sorbents in nhexane was measured using the methodology11 developed by the Military Institute Brno. The amount of CW agent residuals was determined by GC/FID. An Agilent 6890 GC was equipped with a 30 m × 0.32 mm ID (0.25 μm film thickness) HP-5 capillary column (Agilent Technologies, USA). A sample volume of 1 μL was injected using Agilent 7673 autosampler without split. Helium was the carrier gas with a constant flow rate of 4.3 mL/min. The gas flow rates for flame preparation were: H2 30 mL/min, air 400 mL/min, and makeup gas N2 + carrier gas at 25 mL/min. GC oven temperature program was optimized in order to achieve reliable separation of the monitored substance in the short analysis time. The time ramps vary between substances according their properties and are as follows: GD, initial temperature 60 °C after 1 min hold time increase to 100 °C with rate of 10 °C/min followed by increase to the final temperature 250 °C at a rate of 30 °C. VX, initial temperature 90 °C, after 1 min hold time increase to 210 °C with rate of 22 °C/min followed by increase to the final temperature 280 °C at a rate of 50 °C. HD, initial temperature 90 °C, after 1 min hold time increase to 135 °C at a rate of 15 °C/min followed by increase to the final temperature 260 °C at a rate of 25 °C. Data were acquired and processed using the Agilent GC ChemStation Rev A.09.01 software running on an IBM compatible PC. The characteristic GC chromatograms for sulfur mustard, soman, and VX agent are presented in Figure S1. 2.2.2. Decomposition of CWAs in Water. To evaluate the effect of water additions on the detoxification activities, six types of samples were tested: pure nanopowder, pure water, and mixtures with 1, 10, 20, and 50% nanopowder, respectively. The tested material/solution (200 mg) was mixed with 1 mg of the CWA in a 4 mL vial (Supelco). The vial was sealed with a cap and placed in a thermostated shaker. All the experiments were performed at 25 °C. After the designated reaction time, the CWA residuals were extracted with 1.8 mL of n-hexane. The suspension was vigorously agitated, and the organic fraction was separated using a centrifuge (5000 rpm for 3 min) and analyzed for the CWA residual content. The detoxification capabilities of the evaluated samples are expressed as the elimination percentage of the CWA from the reaction mixture under the given conditions. The concentrations of the agents were also quantified using a GC-FID method. 2.2.3. HPLC (DAD; MS) Method for the Decomposition of Cytostatics. The decomposition of cyclophosphamide and ifosfamide on the reactive sorbents in water was measured at University J.E. Purkyně in Ú sti ́ nad Labem using the methodology developed at the Institute of Inorganic Chemistry AVCR.21 The concentration of cytostatic drugs was determined

Figure 2. Double-walled glass boiler (150 L) for indirect heating (duplicator).

0.060 L of 98% H2SO4 in 150 L duplicator. Once the titanyl oxo-sulfate was dissolved in the pellucid solution, 2 kg of urea was added. Next, distilled water was added to reach a total reaction volume of 100 L. The mixture was heated to 100 °C with stirring for 6 h until the pH reached 7.2. The formed precipitate was washed via decantation in two 50 L barrels until the conductivity reached 10 μS, filtered, and dried at 105 °C. 2.1.5. Zr4+- and Hf4+-Doped Titania Laboratory Samples. Zirconium oxo-sulfate (ZrOSO4) was prepared via the reaction of a stoichiometric amount of ZrCl4 and sulfuric acid.23 HfOSO4 was synthesized from HfCl4 using the same procedure. The Zr4+- and Hf4+-doped nanocrystalline titania samples were prepared via homogeneous hydrolysis of TiOSO4 and ZrOSO4 (HfOSO4) aqueous solutions using urea as the precipitation agent. Using this method, we prepared six samples: TiZr_1.0 g, TiHf_0.5 g, TiHf_1.0 g, TiHf_5.0 g, TiHf_8.0 g, and TiHf_15.0 g.23,24 2.2. Characterization Methods. All the prepared samples and their essential characteristics, e.g., X-ray powder diffraction patterns, morphologies, BET surface areas, and porosities, agreed with those of the samples prepared under the laboratory conditions (volume 4 L), which were already published.8,21,25,23,24 The diffractometer Bruker D2 equipped with C


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Table 1. Rate Constant k [s−1] for Soman and VX and k [min−1] for Sulfur Mustard (Yperite) and Degree of Conversion, d [%], at Time t = 60 sa soman

a

−1

VX −1

sulfur mustard −1

sample

k [s ]

d [%]

k [s ]

d [%]

k [min ]

d [%]

FAST-ACT G253 G284 G065

0.1112 0.6897 0.5682 0.5555

100.0 100.0a 100.0a 100.0b

0.0517 0.5988 0.4762 0.5917

92.3 100.0b 100.0b 100.0b

0.0189 0.0543 0.0655 0.0908

52.9d 58.3d 66.9d 74.9d

Time t = 10 s. bTime t = 20 s. cTime t = 40 s. dTime t = 60 min.

3. RESULTS AND DISCUSSION 3.1. Characterization of Prepared Titania-Based Materials. All used samples were prepared by hydrothermal hydrolysis of titanium oxo-sulfate TiOSO4 with urea Co(NH2)2 at temperature 100 °C. According to XRD patterns, diffraction lines of all prepared samples are characteristic for TiO2 anatase modification; see Figurea S2 and S3. From SEM micrographs shown in Figurea S4 and S5, it is evident that the synthesized powders Zr4+−TiO2 and Hf4+−TiO2 form spherically shaped aggregates of a rather narrow size distribution of 1−2 mm in diameter. The measured BET surface area of the all sample powders was determined to be between 259 and 362 m2 g−1 with the sample TiHf_15 exhibiting the largest area 488.1 m2 g−1 (see Figures S6 and S7). Textural characterization of the materials was carried out by low-temperature nitrogen physisorption. All prepared samples had typical type IV isotherm with H1 hysteresis loop found in materials with a relatively narrow range of uniform mesopores according to IUPAC classification. Pore size is at the border between microporous and mesoporous substances with a pore size of 3− 5 nm. Figure S8 presents SEM images, BET (273.1 m2 g−1), adsorption/desorption hysteresis loop, and pore size area distribution of FAST-ACT. 3.2. CWA Stoichiometric Degradation in n-Hexane. The synthesis of the titanium(IV) oxide samples has been published several times, which included anatase modification under laboratory conditions with a 4 L volume and homogeneous hydrolysis of titanium(IV) oxo-sulfate with urea.8,25 This reaction results in spherical 1−2 μm TiO2 particles with anatase modifications, which consist of 5−8 nm nanoparticles. The reaction conditions in a 150 L duplicator, such as the high heat capacity or high ion concentration in the solution, correspond to previous empirically obtained knowledge on the higher stoichiometric efficiency, specific surface area or yield of the reaction. Table 1 presents the rate constant, k [s−1], and degree of conversion, d [%], for the nerve agents, soman, and VX, and k [min−1] for the blister agent, sulfur mustard, using our pilot samples of TiO2 and mixed oxide TiO2−Al2O3 with a mixture of titania and magnesia, which is produced under the commercial label FAST-ACT. FAST-ACT is high-performance specialty material that is effective for neutralizing a wide range of toxic chemicals and can also degrade CWAs. The degradation kinetics of soman, VX and sulfur mustard are shown in Figures 3, 4, and 5, respectively. The figures show that all the pilot samples have higher degradation rates and degrees of conversion than those of the comparative commercial sample, FAST-ACT. The resulting stoichiometric activity is probably the largest influence from doping tetravalent metals, Me4+. Doping the anatase in comparison with the nondoped anatase phase with

by liquid chromatography using the Dionex UltiMate 3000 UHPLC system. The system consisted of an UltiMate 3000 Pump, UltiMate 3000 Diode Array Detector (DAD) operating at 230 nm, Rheodyne 7725i injection valve with 20 μL sampling loop, and the Kinetex column 3 mm × 100 mm packed with octadecyl-bonded stationary phase Gemini, C-18, 5 μm (Phenomenex, Torrance, CA). The composition of mobile phase was acetonitrile (HPLC-gradient-grade, Thermo Fischer Scientific) with the addition of formic acid (0.1%)/water acidified with formic acid (0.1%) with a set gradient from 1.5 min up to 0 min for the column equilibration and from 0 min (30% acetonitrile) up to 10 min (95% acetonitrile), at a rate of 0.80 mL min−1 and column temperature of 30 °C. All samples were analyzed by HPLC/MS. The analysis of cyclophosphamide was performed using LTQ Orbitrap mass spectrometer following chromatographic separation using liquid chromatography (HPLC) system consisting of an autosampler and dual pumps. HPLC system with a model Thermo Finnigan (Palo Alto, CA) was used. The chromatographic separations were carried out by automated injection of 10 μL samples onto the Kinetex column 3 mm × 100 mm packed with octadecyl-bonded stationary phase Gemini, C-18, 5 μm (Phenomenex, Torrance, CA), adopting a gradient mobile phase of acetonitrile (HPLC-gradient grade, Thermo Fischer Scientific) with the addition of formic acid (0.1%)/water acidified with formic acid (0.1%) with a set from 1.5 min up to 0 min for the column equilibration and from 0 min (30% acetonitrile) up to 10 min (95% acetonitrile) in the ESI positive mode, at a rate of 0.80 mL/min. An LTQ Orbitrap mass spectrometer (Thermo Scientific, Bremen, Germany) equipped with an atmospheric pressure interface and an ESI ion source was used. The tuning parameters adopted for the ESI source were as follows: capillary voltage 37.00 V, tube lens 65 V. The source voltage was set to 3.5 kV. The heated capillary temperature was maintained at 275 °C. Analyses were run using full MS (50−1000 m/z range) in the positive ion mode, with a resolution of 30.000 in ITMS mode. 2.2.4. FTIR Analysis of Cytostatics Degradation. The cyclophosphamide degradation process was studied on a Nicolet Impact 400D FTIR spectrometer equipped with the Praying Mantis (Harrick) cuvette for diffuse reflection measurements (DRIFTS). The heating of the cell was controlled using ATC-024−3 equipment (Harrick).19 In a typical experiment, the sorbent sample (∼50 mg) was placed in a DR cuvette, and a droplet (10 μL) of a cyclophosphamide solution (2 mg mL−1) was dosed by an automatic micropipette. The acquisition of spectra was started immediately and repeated in selected time intervals (0, 15, 30, 50, 90, and 120 min. The one spectrum consists of 128 scans with a resolution of 4 cm−1. All the presented spectra (see Figure 12) were processed using OMNIC Spectra (version 8.3) software. D


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Ge4+ influences the content of the amorphous phase and enhances the degradation of soman and VX with the nondoped anatase phase. The highest degrees of conversion, 100% for soman, 99% for VX, and 95% for sulfur mustard, were achieved using the sample containing 2.0 wt % of Ge.9 Similar results were also obtained by doping Zr4+. The undoped titania degraded 87.7% of sulfur mustard, 97.1% of soman and 98.9% of VX in 32 min. In contrast, excellent results were observed for the stoichiometric degradation of soman and VX when the reaction occurred within 1 min.23 These results were refined using a new sample denoted TiZr_1.0 g (see Table 2), and the calculated rate constants for soman and VX are k = 0.2770 and 0.2283 s−1, respectively. The formation of an anion complex, [Zr(OH)n]4−n, in the reaction mixture during the homogeneous hydrolysis increases the proportion of the amorphous phase. The amorphous phase has a positive influence on the stoichiometric degradation activity in nonaqueous and nonpolar environments, e.g., in n-hexane. The excellent soman and VX degradation results upon doping TiO2 samples with Zr and Hf can be attributed to the formation of [Zr(OH)n]4−n and [Hf(OH)n]4−n during the homogeneous hydrolysis.26 If the Zr or Hf content is higher than ∼0.08 M, then degradation of the CWAs decreases due to the reduced crystallinity and porosity, and the entire sample becomes an amorphous phase. The calculated rate constants, k [s−1] for soman and VX and k [min−1] for sulfur mustard, and the degrees of conversion d [% ] for the Zr- and Hf-doped titania samples are presented in Table 2. The corresponding kinetics curves for soman, VX, and sulfur mustard in n-hexane are shown in Figures 6, 7, and 8. 3.3. Derivatives from Sulfur Mustard Stoichiometric Degradation in Water. As previously mentioned, cyclophosphamide and ifosfamide are nitrogen mustards, which are derivatives of sulfur mustard. The mechanism for the destructive adsorption of cyclophosphamide on titanium oxide was monitored using instrumental methods that have been validated for this purpose: LC-MS and in situ sensing DRIFT spectra. Because cytostatic agents are mostly used in aqueous solutions, the decomposition reactions will also be performed in water. Figure 9 is a schematic diagram of the reaction of cyclophosphamide with FAST-ACT to produce 3((amino(bis (2-chloroethyl)amino)phosphoryl)oxy) propanoic acid, which remains in the reaction mixture. The calculated rate constant, k = 0.0842 min−1, corresponds to a 32% degree of conversion per 120 min. However, the decomposition of cyclophosphamide using the pilot TiO2 sample G015 occurs without an intermediate and with k = 0.0602 min−1 and a degree of conversion of 89.7%/120 min. Figure 10 shows the kinetic degradation of cyclophosphamide on G015 and FASTACT. Ifosfamide is degraded to 4-hydroxy-ifosfamide on the surface of FAST-ACT and G015. In the case of FAST-ACT, 4 hydroxy-ifosfamide remains in the reaction mixture. The sample G015 mineralizes the 4-hydroxy-ifosfamide into phosphoric acid, carbon dioxide, and water. The rate constant, k [min−1], and degree of conversion are presented in Table 3. Figure 11 shows the degradation kinetics for ifosfamide on the FASTACT and G015. The decomposition of ifosfamide is slower on the FAST-ACT commercial sample than that on the titania TiO2 sample. An example of the fingerprint DRIFT spectra (700−3000 cm−1) obtained at preselected time intervals (0, 15, 30, 50, 90, and 120 min) after the destructive adsorption on the titanium oxide G015 is presented in Figure 12. The important bands are recognizable as the titania surface-adsorbed cyclophosphamide,

Figure 3. Soman decomposition kinetics on the pilot and FAST-ACT samples.

Figure 4. VX decomposition kinetics on the pilot and FAST-ACT samples.

Figure 5. Sulfur mustard decomposition kinetics on the pilot and FAST-ACT samples.

E


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Table 2. Rate Constant, k [s−1], for Soman and VX and k [min−1] for Sulfur Mustard (Yperite) Degradation and Degree of Conversion, d [%], at Time t = 60 s soman

a

−1

VX −1

sulfur mustard −1

sample

k [s ]

d [%]

k [s ]

d [%]

k [min ]

d [%]

TiZr_1.0 g TiHf_0.5 g TiHf_1.0 g TiHf_5.0 g TiHf_8.0 g TiHf_15.0 g

0.2770 0.3717 0.3134 0.5128 0.3597 0.5025

100.0 100.0 99.5 99.4 100.0 100.0a

0.2283 0.3861 0.1067 0.6578 0.6097 0.7518

100.0a 100.0a 95.8 100.0 100.0 100.0

0.0133 0.1271 0.4347 0.0595 0.0606 0.0724

40.7b 85.9b 90.9b 72.4b 78.4b 89.8b

Time t = 30 s. bTime t = 60 min.

Figure 6. Soman decomposition kinetics on Hf4+-doped titania samples.

Figure 8. Sulfur mustard decomposition kinetics on the Hf4+-doped titania samples.

Figure 9. Scheme of the cyclophosphamide degradation after a surface reaction with FAST-ACT in water. TP1-FA = 3-((amino (bis (2chloroethyl)amino)phosphoryl)oxy) propanoic acid.

wavenumber (approximately 1215 cm−1), which may indicate the group decays during the stable surface complex formation with the surface hydroxyls.28,19 Additionally, the vibrational band at a wavenumber of ∼1170 cm−1, corresponding to the ν(P−O) vibration absorption, disappears over time. This demonstrated that the ring in the cyclophosphamide molecule was completely opened via cleavage of the P−O−aryl bond. In contrast, the vibration bands at 1058 cm−1, which can be assigned to a specific vibration ν(P−O−C), remain unchanged because only a slight deformation occurred due to the separation of the electronegative oxygen from the phosphorus in the ring.29 Therefore, clearly, other vibrational bands will be influenced. The peaks at 884 and 1460 cm−1 represent the absorption of ν(P−N), and the peaks at 2850 and 2960 cm−1

Figure 7. VX decomposition kinetics on the Hf4+-doped titania samples.

which decomposed through a process similar to that of organophosphates on reactive sorbents as previously reported.27,17,18,18 The destructive adsorption of cyclophosphamide occurs via binding of the electrophilic phosphoryl oxygen ν(PO) to the surface hydroxyl groups by hydrogen-bond formation. As seen in Figure 12, the PO bond (∼1280 cm−1) shifts to a lower F


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Figure 10. Cyclophosphamide degradation kinetics on the surfaces of FAST-ACT and the titania sample G015. TP1-FA forms 3-((amino(bis (2-chloroethyl)amino)phosphoryl)oxy) propanoic acid from the degradation of cyclophosphamide on the titania surface.

Figure 12. DRIFT fingerprint spectra of cyclophosphamide destructive adsorption on the titanium oxide sample G015.

destructive nanosorbent and water. As previously mentioned, nano-oxide destructive sorbents have very high degradation activities for real CWAs. Tests were conducted using the described method in a strictly nonaqueous environment.11 The rate constants, k [min−1], and degree of conversion, d [% ], for pure water and 1, 10, 20, and 50% suspensions of the titania destructive sorbents are presented in Tables 4−6. Figures S9− S17 show the degradation kinetics for individual CWAs on the destructive sorbents. The degradation capabilities of all three tested samples of the active, dispersible, destructive nanosorbents, G065, G253, and G284, are very similar. Also, the impact of adding water to the reaction mixture is almost identical for all three samples. The pure materials in a nonaqueous environment have very good detoxification activities for soman and VX, and the CWAs are destroyed within 30 s. Water also shows a detoxification activity of 56% per hour for sulfur mustard and VX and 10% per hour for soman. Increasing the amount of active, dispersed nanooxides in water increases the detoxification activity of the decontamination mixture. The activity of a 1% solution reaches 91% for VX and 25% for soman. The activity of a 10% solution is over 90% per hour for both agents. The detoxification activities of all three tested destructive sorbents are higher than the activity of water. The tests show the specific behavior of the mixtures in the case of sulfur mustard, and the detoxification activities of the mixtures are less than the activity of pure water, as shown in Table 6. The test showed that increasing the amount of water in the mixture of the active, dispersible, destructive nanosorbents negatively affects the theoretical detoxification capability of the decontamination solution in the case of VX and soman. In the case of sulfur mustard, the negative effect of water is lessened due to the similar detoxification efficiency of the nano-oxides and water. However, the intended dispersible, destructive nanosorbents can also be used in a mixture with water despite the negative effect, but the concentration of the prepared mixture should be less than 20%.

Table 3. Rate Constant, k [min−1], and Degree of Conversion, d [%], for Cyclophosphamide and Ifosfamide Degradation cyclophosphamide

ifosfamide

sample

k [min−1]

d [%]

k [min−1]

d [%]

FAST-ACT G015

0.0842 0.0602

32.0 89.7

0.0304 0.0746

40.9 96.5

Figure 11. Ifosfamide degradation kinetics on the surfaces of FASTACT and the titania sample G015.

represent the absorption of the ν(C−H) stretching vibrations.30 In all cases, the belt vibration intensities of the bands decrease due to further cleavage of the cyclophosphamide molecule into smaller fragments. In the presence of gaseous CO2(g), absorption bands appear at 1775 and 1900 cm−1, corresponding to the carbonyl group, ν(CO). The 2361 cm−1 band is assigned to adsorbed CO2 with the Ti−O−C-O adsorption configuration.31 3.4. Stoichiometric Degradation of CWAs in Water. The COUNTERFOG project involves the use of destructive nanosorbents in a fog environment or “smog” that contains a

4. CONCLUSIONS The prepared samples of the destructive sorbents TiO2, and TiO2−Al2O3 and Zr4+- and Hf4+-doped TiO2 laboratory samples were used for the stoichiometric decomposition of G


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Table 4. Rate Constant, k [min−1], for Soman Degradation in 1, 10, 20, and 50% Suspensions of TiO2 in Water and Degree of Conversion, d [%], at Time t = 60 min H2O sample G065 G253 G284 a

−1

k [min ]

1% TiO2

10% TiO2

20% TiO2

−1

−1

−1

50% TiO2

d [%]

k [min ]

d [%]

k [min ]

d [%]

k [min ]

d [%]

k [min−1]

d [%]

10.7

0.0212 0.0202 0.0220

26.7 30.9 25.4

0.0558 0.0578 0.0463

92.2 93.9 73.04

0.1095 0.1144 0.0812

99.0 95.5 93.4

1.3889 1.4705 0.9523

100a 100a 100b

0.0363

Time t = 10 min. bTime t = 20 min.

Table 5. Rate Constant, k [min−1], for VX Degradation in 1, 10, 20, and 50% Suspensions of TiO2 in Water and Degree of Conversion, d [%], at Time t = 60 min H2O sample G065 G253 G284 a

−1

k [min ]

1% TiO2

10% TiO2

20% TiO2

−1

−1

−1

50% TiO2

d [%]

k [min ]

d [%]

k [min ]

d [%]

k [min ]

d [%]

k [min−1]

d [%]

56.2

0.0408 0.0497 0.0469

89.1 91.4 91.1

0.0615 0.0638 0.0741

96.7 97.6 99.3

0.0836 0.0925 0.1133

99.7 99.3 99.9

0.8474 0.9803 1.0869

100a 100b 100b

0.0465

Time t = 20 min. bTime t = 10 min.

Table 6. Rate Constant, k [min−1], for Sulfur Mustard Degradation in 1, 10, 20, 50, and 100% Suspensions of TiO2 in Water and Degree of Conversion, d [%], at Time t = 60 min H2O sample G065 G253 G284

−1

k [min ] 0.0186

1% TiO2 −1

10% TiO2 −1

20% TiO2

d [%]

k [min ]

d [%]

k [min ]

d [%]

k [min ]

d [%]

k [min−1]

d [%]

56.7

0.0183 178 0.0089

55.7 41.5 52.8

0.0072 0.0152 0.0081

50.7 36.7 37.2

0.0062 0.0131 0.0071

35.8 32.7 29.5

0.0228 0.0272 0.0210

69.7 59.3 62.3

0.0242 0.0321 0.0246

78.0 63.4 63.4

ACKNOWLEDGMENTS This work was supported by project NATO SPS 984599 and partially funded by the Seventh Framework Programme of the European Commission under grant 312804 - COUNTERFOG.

■

REFERENCES

(1) Wagner, G. W. Decontamination of chemical warfare agents with nanosize metal oxides. Abs. Pap. Am. Chem. Soc. 2009, 237, 125. (2) Wagner, G. W.; Procell, L. R.; Koper, O. B.; Klabunde, K. J. Decontamination of chemical warfare agents with nanosize metal oxides. ACS Symp. Ser. 2001, 891, 139. (3) Wagner, G. W.; Koper, O. B.; Lucas, E.; Decker, S.; Klabunde, K. J. Reactions of VX, GD, and HD with nanosize CaO: Autocatalytic dehydrohalogenation of HD. J. Phys. Chem. B 2000, 104 (21), 5118− 23. (4) Wagner, G. W.; Bartram, P. W.; Koper, O.; Klabunde, K. J. Reactions of VX, GD, and HD with nanosize MgO. J. Phys. Chem. B 1999, 103 (16), 3225−8. (5) Wagner, G. W.; Procell, L. R.; O’Connor, R. J.; Munavalli, S.; Carnes, C. L.; Kapoor, P. N.; Klabunde, K. J. Reactions of VX, GB, GD, and HD with nanosize Al2O3. Formation of aluminophosphonates. J. Am. Chem. Soc. 2001, 123 (8), 1636−44. (6) Stengl, V.; Bakardjieva, S.; Marikova, M.; Subrt, J.; Oplustil, F.; Olsanska, M. Aerogel nanoscale magnesium oxides as a destructive sorbent for toxic chemical agents. Cent. Eur. J. Chem. 2004, 2 (1), 16− 33. (7) Utamapanya, S.; Klabunde, K. J.; Schlup, J. R. NANOSCALE METAL-OXIDE PARTICLES CLUSTERS AS CHEMICAL REAGENTS - SYNTHESIS AND PROPERTIES OF ULTRAHIGH SURFACE-AREA MAGNESIUM-HYDROXIDE AND MAGNESIUM-OXIDE. Chem. Mater. 1991, 3 (1), 175−81. (8) Stengl, V.; Marikova, M.; Bakardjieva, S.; Subrt, J.; Oplustil, F.; Olsanska, M. Reaction of sulfur mustard gas, soman and agent VX with nanosized anatase TiO2 and ferrihydrite. J. Chem. Technol. Biotechnol. 2005, 80 (7), 754−8.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.iecr.7b04253. GC chromatograph figures of sulfur mustard, agent VX, and soman; XRD, SEM, BET, and porosity of pilot samples G253, G065, G284, G065, commercial sample FAST-ACT, and Zr4+- and Hf4+-doped titania samples; pictures of the decomposition kinetics off all samples on soman, agent VX, and sulfur mustard (PDF)

■

−1

100% TiO2

k [min ]

the CWAs, soman, VX, sulfur mustard, and sulfur mustard derivatives, nitrogen mustards, which are used as cytostatics. The results were compared with the degradation activity of the commercial product FAST-ACT. All the prepared samples had faster kinetics and were more effective for the stoichiometric decomposition of CWAs and also nitrogen mustards used as cytostatics, than FAST-ACT. The tests also show that the detoxification activity is reduced by the addition of water to the reaction mixture except for sulfur mustard derivatives.

■

50% TiO2

d [%]

■

−1

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

̌ Václav Stengl: 0000-0002-2262-5533 Pavel Janoš: 0000-0002-3098-4333 Notes

The authors declare no competing financial interest. H


Article


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