Hyunsook Jung

Zirconium Hydroxide‐coated Nanofiber Mats for Nerve Agent Decontamination

Diverse innovative fabrics with specific functionalities have been developed for requirements such as self-decontamination of chemical/biological pollutants and toxic nerve agents. In this work, Zr(OH)4 -coated nylon-6,6 nanofiber mats were fabricated for the decontamination of nerve agents. Nylon-6,6 fabric was prepared via the electrospinning process, followed by coating with Zr(OH)4 , which was obtained by the hydrolysis of Zr(OBu)4 by a sol-gel reaction on nanofiber surfaces. The reaction conditions were optimized by varying the amounts of Zr(OBu)4 ,the reaction time, and the temperature of the sol-gel reaction. The composite nanofibers show high decontamination efficiency against diisopropylfluorophosphate, which is a nerve agent analogue, due to its high nucleophilicity that aids in the catalysis of the hydrolysis of the phosphonate ester bonds. Composite nanofiber mats have a large potential and can be applied in specific fields such as military and medical markets.

Toward a detoxification fabric against nerve gas agents: guanidine-functionalized poly[2-(3-butenyl)-2-oxazoline]/Nylon-6,6 nanofibers

A novel guanidine-functionalized polymer, poly[2-(3-butenyl)-2-oxazoline] (PBuOxz), has been co-electrospun with Nylon-6,6 to form fibers that could be used for the decontamination of chemical warfare agents (CWAs). PBuOxz was obtained from the living cationic polymerization of 2-(3-butenyl)-2-oxazoline, which was synthesized starting from 4-pentenoic acid. This clickable PBuOxz polymer could be easily functionalized through the introduction of amine groups via thiol–ene click chemistry, followed by guanidinylation to form guanidine-functionalized PBuOxz (G-PBuOxz). The synthesized G-PBuOxz/Nylon-6,6 fibers are an active hydrolysis species for diisopropyl fluorophosphate (DFP), an organophosphate mimic of nerve agents. The decontamination efficiency for DFP could be as high as 100% under trace aqueous solution conditions using this G-PBuOxz/Nylon-6,6 fiber as the decontamination agent at the ratio of [guanidine]/[DFP] = 100/1 in 2 hours. The hydrolysis occurs via a general SN2 mechanism for this G-PBuOxz-based catalysis. Furthermore, the kinetics of decontamination were also investigated based on time and guanidine concentration. Hence, this G-PBuOxz/Nylon-6,6 fiber is effective as a hydrolyzing agent against toxic organophosphates, and thus exhibits potential as a material for protecting against chemical warfare agents.

Study on the initial evaporation rates of distilled sulphur mustard (HD) in concrete using wind tunnel and TD-GC/MSD: effect of drop size and temperature

In this paper, we demonstrate a robust, analytical method for the study of the initial evaporation rates of distilled sulphur mustard (HD) in concrete at various drop sizes and temperatures. We used a 5-cm wind tunnel and thermal desorption (TD) in connection with gas chromatograph and mass spectrometry detection (GC/MSD). Drops of neat HD, ranging in sizes of 1, 3, 6 and 9 µL, were applied to small concrete coupons. The temperatures were either 18°C, 25°C, 35°C or 50°C. The drop of HD rapidly spread in concrete upon its release. The initial evaporation rates of the drop of HD were analysed by TD in conjunction with GC/MSD. The results showed that the initial evaporation rates increased while HD spread over the surface of concrete, then decreased as the contamination was over. We also found that the initial evaporation rates of the drop of HD in concrete are linearly proportional to drop size and temperature. In particular, drop size or spreading factor has a more pronounced effect on the initial evaporation rates of the drop of HD in concrete than temperature.

Enhanced thermal degradation of 2,2′-dichlorodiethyl sulfide (sulfur mustard, HD) with the presence of metal oxides

GRAPHICAL ABSTRACT ABSTRACT Thermal degradation of sulfur mustard (2,2′-dichlorodiethyl sulfide, HD) in the presence of metal oxide adsorbents was investigated by thermal desorption in conjunction with gas chromatography–mass spectrometry (GC-MS). Zr(OH)4, Al2O3, Al2CoO4, MgO, CeO2, and V2O5 were used as metal oxide adsorbents. Neat HD was spiked onto the metal oxides packed in glass tubes, which were kept at room temperature and then heated at moderately elevated temperatures of 100°C by a thermal desorption system. The products of thermal degradation were directly transferred and analyzed by GC-MS. 1,4-Dithiane and 1,4-oxathiane were characterized as the major products of the thermal degradation of HD in the presence of Zr(OH)4, Al2O3, Al2CoO4, and CeO2 adsorbents. No effective degradation was observed with MgO and V2O5. Of particular note is Zr(OH)4, which extremely enhanced the thermal degradation of HD.

Fate and degradation of the chemical warfare agent soman on sands

Soman is one of the most toxic nerve agents of the known chemical warfare agents. There is actually few knowledge on the behavior of soman in the event of an environmental contamination. It is in particular unknown whether soman remains on a given surface, evaporates into air, or degrades. Here, we studied the evaporation of soman deposited on silica sand using a laboratory-sized wind tunnel, thermal desorption, and gas chromatography. We also investigated the degradation of soman on silica sand by 31phosphorus solid state magic angle spinning nuclear magnetic resonance and gas chromatography–mass spectrometry. Results show that a drop of soman on silica sand spreads laterally while evaporating. The maximum vapor concentration was found when the spreading of the soman drop was maximum on the surface. Simultaneously, soman was absorbed gradually into the pore of sand and degraded to O-pinacolyl-methylphosphonic acid following a pseudo-first-order rate reaction over weeks. To our best knowledge, this is the first report on the fate of soman in a sandy environment.

Development of Chemical Vapor Sampler for Man-in-Simulant Test(MIST)

We have recently developed a cost-effective and pouch-type chemical vapor sampler which consists of a selectively permeable high density polyethylene(HDPE) membrane, aluminum/nylon barrier film, and adsorbents. Since the sampler mimics the actual adsorption process that occurs when the skin is exposed to chemical vapors, it can be applied to man-in-simulant test(MIST) to determine the protective capability of individual protective ensembles for chemical warfare agents. In this study, we describe the manufacturing process of samplers and results for performance testing on MIST. Methyl salicylate(MeS) is used to simulate chemical agent vapor and the vapor sampler was used to monitor chemical concentration of MeS inside the protective suit system while worn. Values of protection factors(PF) were also analyzed to provide an indication of the protection level of the suit system evaluate by MIST. The results obtained by home-made samplers(ADD samplers) and commercially avaliable ones(Natick samplers) showed no significant differences.