Decontamination of Sulfur Mustard from Printed ... - ACS Publications

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Decontamination of Sulfur Mustard from Printed Circuit Board Using Zr-Doped Titania Suspension Václav Štengl*,† and Tomás ̌ Matys Grygar† Department of Solid State Chemisty, Institute of Inorganic Chemistry AS CR v.v.i., 250 68 Ř ež, Czech Republic

†

František Opluštil‡ and Marcela Olšanská‡ ‡

Military Technical Institute of Protection Brno, Veslařská 230, 628 00 Brno, Czech Republic ABSTRACT: We present a procedure for removal and detoxification of chemical warfare agents (CWA) from corrosionsensitive components using their reactive sorption (adsorption and bond cleavage). The procedure consists of spraying a suspended sorbent over a contaminated surface followed by mechanical removal of the spent sorbent after liquid phase evaporation. The procedure was tested using a video graphics array (VGA computer card) VGA card, sulfur mustard (yperite, HD agent, bis(2-chloroethyl)sulfide), and Zr4+-doped TiO2 sorbent obtained by homogeneous hydrolysis. After 60 min of interaction with a suspension of the reactive sorbent with the contaminated VGA card, 99.3% of the sulfur mustard was removed, while the VGA card retained its functionality. The procedure does not require specialized instrumentation. This is feasible for electronic devices, as they do not need corrosive and electrically conducting agents or nonvolatile solvents that would harm electronic circuits. The method would be applicable to decontamination of a broad range of CWAs and pesticides.

1. INTRODUCTION Reactive sorbents, materials that adsorb CWAs and cleave some of their chemical bonds, have become well-recognized decontamination agents during the past decade (see for recent reviews, refs 1,2). Metal oxide nanoparticles such as TiO2 and MgO are currently used as potential catalysts for the decontamination of chemical and biological warfare (CBW) agents.3 The main advantage of the reactive sorbents is actually their detoxification ability and not mere sorption as in the case of carbonaceous sorbents. For example, sulfur mustard is dechlorinated to divinyl sulphide and hydrolyzed to thiodiglycol.4,5 Since the end of the 1990s, numerous studies have reported on the synthesis of novel reactive sorbents, mainly metal oxides, and the degradation kinetics and reaction mechanisms have been well established1,2,4−14 Currently the used titania,8−10,12,15 and Mn oxides,11,16 have a better efficiency than the originally studied Mg,4 Ca,6 and Al oxides.7 A practical example of utilization of the reactive sorbent for organophosphates, acids, and several other toxic agents is FAST-ACT produced by NanoScale Corporation (Manhattan, KS). The reactive sorbents allow not only faster decontamination but also novel approaches to the decontamination strategy, such as self-decontaminating paints.17 To achieve further progress toward the practical use of reactive sorbents, it seems essential to find an application area not covered by other commercially present decontamination procedures. One such example could be the decontamination of corrosion-sensitive electronic circuits, such as computer components, which can be harmed by traditionally used bleaches or other currently known procedures or which would require very special technical equipment.18,19 Activated charcoal impregnated with metal ions is currently used in protective clothing applications, which has some © 2013 American Chemical Society

disadvantages. Electrospinning is emerging as one of the cheapest technologies to produce continuous nanofibers with a high surface area-to-volume ratio.20,21 MgO nanoparticles were synthesized by the Aero gel method and next mixed with various polymer solutions (poly(vinylchloride), poly(vinylidene fluoride-co-hexafluoropropylene, polysulfone)) and then subjected to electrospinning to produce nanocomposite membranes. The hydrolysis of paraoxon, a nerve agent stimulant, in the presence of these membranes was studied using UV.22 A comparative study of antimicrobial activity is done using three different electrospun nanofibers, namely, CA, PAN, and PVC, used as control and with various amounts of AgNO3 being treated with UV-irradiation leading to the enhancement of silver nanoparticles.23 This work reports on the practical use of titania suspension for decontamination of a corrosion-sensitive components of computers. One of the ways to apply reactive sorbents to contaminated surfaces or components of technology is their deposition in a form of dispersion, which has an advantage not only in that it allows a simple application of powdered reagents but also that it is easier to dissolve CWA droplets present on the surface. Preliminary experiments showed that titania suspended in appropriate solvents decontaminates sulfur mustard from a rubber plate and a paint-coated surface faster than dry titania.24 After complete evaporation of the solvent, it is possible to remove a layer of powdered reagents, such as suction with a vacuum cleaner or mechanical sweeping. Nonaggressiveness of the procedure was verified by a functional Received: Revised: Accepted: Published: 3436

October 5, 2012 January 25, 2013 February 12, 2013 February 12, 2013 dx.doi.org/10.1021/ie302711u | Ind. Eng. Chem. Res. 2013, 52, 3436−3440

Industrial & Engineering Chemistry Research

Article

surface is sufficient with respect to the intensity of the spraying. Areal density of the coating dispersion mixture was 600−700 mL/m2 (Figure 2). Homogeneous coverage of the decontami-

test of the decontaminated component. The decontamination efficiency was evaluated using the methodology specified in the document of NATO.25

2. EXPERIMENTAL SECTION 2.1. Used Decontamination Reagent. Dispersion of powdered reagents was prepared from the sample specimen of nanostructured of Zr4+-doped TiO2 marked as TiZr_412 (pilot plant production in the Institute of Inorganic Chemistry ASCR v.v.i.). The synthesis procedure is based on the environmentally benign hydrolysis of metal salts from aqueous solution by urea.26 Powder reagent was dispersed in n-nonane in the ratio of 100 parts by weight of powder and 600 parts by volume of solvent. The powder was gradually added into the solvent at the same time as intensive stirring of the resulting mixture. 2.2. Test Specimen Corrosion-Sensitive Materials. The test used a VGA graphics card WD90C30-LR (Western Digital Ltd.) 2.3. Application of Powder Reagent Dispersion and Decontamination Process. Sulfur mustard (other names yperite, HD agent, bis (2-chloroethyl) sulfide), purity 92.3%, was used. A total of 55 droplets of sulfur mustard were deposited over a VGA card using a digital micropipet; total initial amount of sulfur mustard was 71 mg (Figure 1). The

Figure 2. Layer of dispersed titania immediately after deposition on the surface of the VGA card.

nated surface was ensured by visual examination; a large excess of the reactive sorbent was intentionally used (Figure 2). The applied layer was left on the card surface at room temperature (21 ± 1) °C for 60 min. During this interval, nonane spontaneously evaporated. The layer of the remaining dry sorbent was removed using a flat brush harder (Figure 3); a

Figure 1. VGA cards contaminated by droplets of sulfur mustard.

volume of an individual droplet was 0.8 μL. Then the VGA card was mounted in a horizontal position in a closed stainless steel dish (25 cm × 25 cm × 3 cm) and left at room temperature (21 ± 1) ° C for 60 min. Possible evaporation of sulfur mustard in that stage was not assumed. The VGA card was fixed at an angle of 45°, and then it was sprayed by powder reagent dispersed in nonane using an electrical spray gun (Wagner, Type 400 SE), with a circular nozzle 0.8 mm. The distance of the nozzle from the VGA card surface was 30 cm. The adhesion of sulfur mustard to the card

Figure 3. Mechanical removal of titania from the card surface. 3437

dx.doi.org/10.1021/ie302711u | Ind. Eng. Chem. Res. 2013, 52, 3436−3440


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vacuum cleaner with a sufficient filter can also be used. The sorbent, which penetrated small slits between the board and the electronic components, was not completely removed by that technique. The appearance of the VGA card after decontamination and draining layer of powdered reagents is shown in Figure 4.

the residual contamination of the circuit, it would be necessary to repeat the steps of spraying the sorbent suspension, solvent evaporation, and spent sorbent removal. There were no visible changes in the appearance of the VGA card after the treatment (compare Figures 1 and 4), and it retained its functionality after the test. 3.2. Comparison with Other Procedures. Enormous attention has recently been paid to synthesize novel reactive sorbents and describe the mechanism of their action in degradation CWAs; however, it has not been accompanied by an adequate effort to optimize their practical implementation. The recent reviews on CWAs and their destruction do not mention practical ways of how to apply nanocrystalline reactive sorbents,1,2,28 although their suitability for this purpose seems indisputable. Selection of well-targeted types of objects to be decontaminated is vital for optimization of a novel procedure. Actually, the decontamination of electronic devices is still a challenge. Hermann19 published a report on a vacuum plasma decontamination of sensitive electronic components, which included work in special chamber attached to plasma generator all operating at 30 Torr, which is technically demanding. Kaiser and Haraldsen18 proposed a flow through line in which the electronic equipment was immersed in an appropriate solvent, which does not harm the equipment but does dissolve CWA; the solution circulated through carbon filters. Although this setup was very efficient in terms of decontamination degree, CWAs were transferred to filters but not detoxified. Also, this approach is obviously more technically demanding than spraying and mechanical removal of reactive sorbents. Application of a suspended solid on a contaminated surface is also used in commercially available kit Sx 34 (Cristanini S.p.A, Rivoli Veronese, Italy); however, that solid does not detoxify CWAs but just allows their collection from contaminated printed circuits by a vacuum cleaner. Mere removal of contaminants would be achieved after surface cleaning by pressurized or solid CO2. An additional advantage of the proposed procedure is that it does not expose the objects to be decontaminated to soluble salts, alkalies, and nonvolatile solvents, which could be retained on finely structured surfaces and later cause electric short circuits or corrosion. The residues of titania could hardly cause such post-treatment damages, but they could endanger fine mechanic (movable) components. The sorbent application in a form of suspension facilitates the detoxification kinetics9,13 and simplifies treatment of a finely structured surface of printed circuits. The solvent volatility is advantageous for subsequent mechanical removal of the spent sorbent; however, the flammability of nonane could perhaps present a practical problem. For the dispersion of nanostructured metal oxides, nonpolar aprotic solvents are most suitable, but nonflammable hydrogen fluorinated ethers could be an alternative to hydrocarbons. The novelty of our work is an optimal choice of both the reactive sorbent and solvent. Aprotic nonpolar solvents allow the chemical reaction of CWA with the sorbent; this does not proceed in protic solvents. The role of solvent is not fully understood. In batch experiments, the rate of sulfur mustard degradation by titania depends on a solvent: it decreased in the following order: nonane > xylene > butyl acetate > DMSO > ethanol > dioxin.24 The chosen solvent (nonane) has optimal reaction properties and volatility: the suspension should dry out within 30−60 min to allow diffusion and decontamination. The concentration of a solid is chosen to achieve a suspension

Figure 4. VGA card after decontamination.

2.4. Determination of Sulfur Mustard after Decontamination. The final contamination of the VGA card was determined after three times extracting the VGA card with a prescribed mixture of solvents (heptane mixed with acetone in the ratio of 9:1 parts by volume) as required by Decontamination Triptych.25 The VGA card was always inserted into a polypropylene dish with a cover filled with 50 mL of extraction mixture. The dish was then placed and mounted on the digital shaker (IKA, model KS 130) and controlled at a speed of 130 vibrations per minute for 120 min. The use of excess liquid and long extraction time should guarantee CWA removal from orifices in the VGA card. Extracts were analyzed by a GC technique using a gas chromatograph 6890 Agilent Technologies with a silica capillary column DB FFAP and FPD-S detector.8−10,12 The concentration of sulfur mustard in this extract was determined and recalculated to the total nonreacted amount and corresponding decontamination efficiency. The final removal of the residual powder reagents was performed with ethanol in an ultrasonic bath.

3. RESULTS AND DISCUSSION 3.1. Decontamination of VGA Card. The residual amount of sulfur mustard after 1 h decontamination of the VGA card was 492 μg, i.e., 0.69% of the original value. Although that residual contamination somewhat exceeds the prescribed value for the maximum allowable contamination for long-term contact with unprotected skin (more than 6 h contact), it meets the safety requirements for short-term contact (less than 15 min). Love et al.27 found comparable efficiency with sulfur mustard decontamination from flat steel surfaces using the modern decontamination procedures. This is quite satisfactory achievement because the efficiency of the VGA card decontamination could have been hindered by segmentation (fine structuring); the droplets of CWA can easily penetrate into the slits and holes in the printed circuits. To further reduce 3438



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viscosity sufficient to prevent flowing off during the decontamination. 3.3. Possible Problems and Future Prospects. Penetration of CWA to some plastics and rubber, causing their softening, has been reported.29 In the VGA card, there are neither rubber nor thermoplastic parts but rather hard plastics. The CWA removal from orifices and porous surfaces should be guaranteed by diffusion in liquid medium of the suspension. The decontamination was checked by repetitive VGA card extraction by solvent, and hence, the calculated efficiency also includes the consequences of places possibly less accessible for suspended reactive sorbent. Possible evaporation of sulfur mustard during decontamination was not analyzed, but it should theoretically be taken into account if confined places were decontaminated. The duration of the extraction was taken from NATO Decon Triptych [24]; no experiments with shorter times were performed. Another concern could arise from possible toxicity of the products. In the heptane−acetone extract after the experiment, no expected (and unwanted) toxic reaction products (sulfur mustard monoxide and dioxide) were identified. If these products had been formed, they remained covalently bonded to the oxide surface. We expect that the procedure described in this paper would also be successful with other common CWAs, as it is known that HD is generally reacting slower with chemical decontaminants than agents like VX and GD.8−10,12,17,27 Efficiency of Zr4+-doped TiO2 under the conditions reported in this paper has already been proven.12 Chemical similarity of organophosphate CWAs and pesticides and corresponding efficiency of reactive sorbents to their adsorption and chemical cleavage1 is promising also for a broader future practical use of the proposed procedure.

(3) Sundarrajan, S.; Chandrasekaran, A. R.; Ramakrishna, S. An update on nanomaterials-based textiles for protection and decontamination. J. Am. Ceram. Soc. 2010, 93 (12), 3955−3975. (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), 3225−3228. (5) Stengl, V.; Kralova, D.; Oplustil, F.; Nemec, T. Mesoporous manganese oxide for warfare agents degradation. Microporous Mesoporous Mater. 2012, 156 (0), 224−232. (6) 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− 5123. (7) 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), 1636−1644. (8) Wagner, G. W.; Procell, L. R.; Koper, O. B.; Klabunde, K. J. Decontamination of chemical warfare agents with nanosize metal oxides. Abstr. Pap. Am. Chem. Soc. 2001, 221, U571−U571. (9) Klabunde, K. J.; Erickson, L.; Koper, O.; Richards, R. Review of Nanoscale Materials in Chemistry: Environmental Applications. In Nanoscale Materials in Chemistry: Environmental Applications; Erickson, L. E.; Koodali, R. T.; Richards, R. M., Eds.; 2010; Vol. 1045, pp 1−13. (10) 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), 754−758. (11) Stengl, V.; Matys Grygar, T.; Oplustil, F.; Nemec, T. Sulphur mustard degradation on zirconium doped Ti−Fe oxides. J. Hazard. Mater. 2011, 192 (3), 1491−1504. (12) Stengl, V.; Bakardjieva, S.; Murafa, N.; Oplustil, F. Zirconium doped titania: Destruction of warfare agents and photocatalytic degradation of orange 2 dye. Open Process Chem. J. 2008, 1, 1−7. (13) Stengl, V.; Bludska, J.; Oplustil, F.; Nemec, T. Mesoporous titanium−manganese dioxide for sulphur mustard and soman decontamination. Mater. Res. Bull. 2011, 46 (11), 2050−2056. (14) Stengl, V.; Matys Grygar, T.; Oplustil, F.; Nemec, T. Ge4+ doped TiO2 for stoichiometric degradation of warfare agents. J. Hazard. Mater. 2012, 227−228 (0), 62−67. (15) Kleinhammes, A.; Wagner, G. W.; Kulkarni, H.; Jia, Y. Y.; Zhang, Q.; Qin, L. C.; Wu, Y. Decontamination of 2-chloroethyl ethylsulfide using titanate nanoscrolls. Chem. Phys. Lett. 2005, 411 (1− 3), 81−85. (16) Prasad, G. K.; Mahato, T. H.; Pandey, P.; Singh, B.; Suryanarayana, M. V. S.; Saxena, A.; Shekhar, K. Reactive sorbent based on manganese oxide nanotubes and nanosheets for the decontamination of 2-chloro-ethyl ethyl sulphide. Microporous Mesoporous Mater. 2007, 106 (1−3), 256−261. (17) Wagner, G. W.; Peterson, G. W.; Mahle, J. J. Effect of adsorbed water and surface hydroxyls on the hydrolysis of VX, GD, and HD on titania materials: The development of self-decontaminating paints. Ind. Eng. Chem. Res. 2012, 51 (9), 3598−3603. (18) Kaiser, R.; Haraldsen, K. Decontamination of Sensitive Equipment, VSP BV imprint of Brill, Utrecht, 2003; pp 109−127. (19) Herrmann, H. W.; Selwyn, G. S.; Henins, I.; Park, J.; Jeffery, M.; Williams, J. M. Chemical warfare agent decontamination studies in the plasma decon chamber. IEEE Trans. Plasma Sci. 2002, 30 (4), 1460− 1470. (20) Sundarrajan, S.; Venkatesan, A.; Ramakrishna, S. Fabrication of nanostructured self-detoxifying nanofiber membranes that contain active polymeric functional groups. Macromol. Rapid Commun. 2009, 30 (20), 1769−1774. (21) Sundarrajan, S.; Ramakrishna, S. Fabrication of functionalized nanofiber membranes containing nanoparticles. J. Nanosci. Nanotechnol. 2010, 10 (2), 1139−1147. (22) Sundarrajan, S.; Ramakrishna, S. Fabrication of nanocomposite membranes from nanofibers and nanoparticles for protection against chemical warfare stimulants. J. Mater. Sci. 2007, 42 (20), 8400−8407.

4. CONCLUSIONS We experimentally verified effective decontamination of sulfur mustard (yperite) from a PC video card by nanostructured Zr4+-doped TiO2 dispersed in nonane. The proposed technique does not produce toxic waste and is technically feasible with simple equipment. The proposed technique is not limited to sulfur mustard as the ability of nanostructured titania to detoxify also other known CWAs and organophosphate pesticides is well known.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel.: 420 2 6617 3534. Fax.: 420 2 2094 0157. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by RVO 61388980 and Project FP7SEC-2012 No. 312 804 Counterfog (Device for Large Scale Fog Decontamination).

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REFERENCES

(1) Kim, K.; Tsay, O. G.; Atwood, D. A.; Churchill, D. G. Destruction and detection of chemical warfare agents. Chem. Rev. 2011, 111 (9), 5345−5403. (2) Prasad, G. K.; Ramacharyulu, P.; Singh, B. Nanomaterials based decontaminants against chemical warfare agents. J. Sci. Ind. Res. 2011, 70 (2), 91−104. 3439



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(23) Lala, N. L.; Ramaseshan, R.; Bojun, L.; Sundarrajan, S.; Barhate, R. S.; Ying-jun, L.; Ramakrishna, S. Fabrication of nanofibers with antimicrobial functionality used as filters: protection against bacterial contaminants. Biotechnol. Bioeng. 2007, 97 (6), 1357−1365. (24) Opluštil,F.; Olšanská, M. Preparation Nanodispersive Oxides and Hydroxides of Light Metals (Mg, Al and Ti) and Their Reactivity against Poisonous Substances; Military Technical Institute of Protection Brno Research Report; 2001; unpublished. (25) Combined Operation Characteristics, Technical Specification and Test Procedures and Evaluation Criteria for NBC Decontamination Equipment (Decontamination Triptych); AEP-58; U.S. Department of Defense, 2005. (26) Stengl, V.; Subrt, J.; Bezdicka, P.; Marikova, M.; Bakardjieva, S. Homogeneous Precipitation with Urea: An Easy Process for Making Spherical Hydrous Metal Oxides. In Solid State Chemistry V; Sajgalik, P., Drabik, M., Varga, S., Eds.; Trans Tech Publications, Ltd: Zurich, Switzerland, 2003; Vol. 90−91, pp 121−126. (27) Love, A. H.; Bailey, C. G.; Hanna, M. L.; Hok, S.; Vu, A. K.; Reutter, D. J.; Raber, E. Efficacy of liquid and foam decontamination technologies for chemical warfare agents on indoor surfaces. J. Hazard. Mater. 2011, 196, 115−122. (28) Seto, Y. Research and development of on-site decontamination system for biological and chemical warfare agents. J. Health Sci. 2011, 57 (4), 311−333. (29) Wagner, G. W.; Procell, L. R.; Sorrick, D. C.; Lawson, G. E.; Wells, C. M.; Reynolds, C. M.; Ringelberg, D. B.; Foley, K. L.; Lumetta, G. J.; Blanchard, D. L. All-weather hydrogen peroxide-based decontamination of CBRN contaminants. Ind. Eng. Chem. Res. 2010, 49 (7), 3099−3105.

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Decontamination of Sulfur Mustard from Printed ... - ACS Publications

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