Non-Isothermal Sublimation Kinetics of 2,4,6-Trinitrotoluene (TNT) Nanofilms.

Non-isothermal sublimation kinetics of low-volatile materials is more favorable over isothermal data when time is a crucial factor to be considered, especially in the subject of detecting explosives. In this article, we report on the in-situ measurements of the sublimation activation energy for 2,4,6-trinitrotoluene (TNT) continuous nanofilms in air using rising-temperature UV-Vis absorbance spectroscopy at different heating rates. The TNT films were prepared by the spin coating deposition technique. For the first time, the most widely used procedure to determine sublimation rates using thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) was followed in this work using UV-Vis absorbance spectroscopy. The sublimation kinetics were analyzed using three well-established calculating techniques. The non-isothermal based activation energy values using the Ozawa, Flynn⁻Wall, and Kissinger models were 105.9 ± 1.4 kJ mol-1, 102.1 ± 2.7 kJ mol-1, and 105.8 ± 1.6 kJ mol-1, respectively. The calculated activation energy agreed well with our previously reported isothermally-measured value for TNT nanofilms using UV-Vis absorbance spectroscopy. The results show that the well-established non-isothermal analytical techniques can be successfully applied at a nanoscale to determine sublimation kinetics using absorbance spectroscopy.

Trace detection of some nitro-explosives using thermal mediated immunochemical defragmented method.

A new immunoassay format using thermally induced defragmentation of some nitro-explosives with a high degree of selectivity is reported. Specific antibodies against three widely used explosives, 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), and pentaerythritol tetranitrate (PETN) were generated by designing suitable haptens using geometry optimization modules. These in-house generated antibodies were used in a newly developed thermal mediated immunochemical biosensing technique which involves the binding of specific antibodies to respective nitro-explosives on a microtiter strip, resulting in the formation of specific immunocomplex. Heating the specific immuno-complex formed on microtiter wells resulted in thermal lysis of nitro-explosives to generate nitrite ions. These ions react with Griess reagent to form a colored chromophore which correlates the concentration of individual explosive in the sample. The present work fulfills the need for an improved explosive detecting system that is highly specific and capable of quickly determining the presence of nitrate containing explosives from a mixture pool.

Graphene oxide/Fe3O4 as sorbent for magnetic solid-phase extraction coupled with liquid chromatography to determine 2,4,6-trinitrotoluene in water samples.

A fast, simple, economical, and environmentally friendly magnetic solid-phase extraction (MSPE) procedure has been developed to preconcentrate 2,4,6-trinitrotoluene (TNT) from water samples prior to determination by liquid chromatography-UV-Vis employing graphene oxide/Fe3O4 nanocomposite as sorbent. The nanocomposite synthesis was investigated, and the MSPE was optimized by a multivariate approach. The optimum MSPE conditions were 40 mg of nanocomposite, 10 min of vortex extraction, 1 mL of acetonitrile as eluent, and 6 min of desorption in an ultrasonic bath. Under the optimized experimental conditions, the method was evaluated to obtain a preconcentration factor of 153. The linearity of the method was studied from 1 to 100 µg L-1 (N = 5), obtaining a correlation coefficient of 0.994. The relative standard deviation and limit of detection were found to be 12% (n = 6, 10 µg L-1) and 0.3 µg L-1, respectively. The applicability of the method was investigated, analyzing three types of water samples (i.e., reservoir and drinking water and effluent wastewater) and recovery values ranged between 87 and 120% (50 µg L-1 spiking level), showing that the matrix had a negligible effect upon extraction. Finally, the semiquantitative Eco-Scale metrics confirmed the greenness of the developed method.

Anaerobic in situ biodegradation of TNT using whey as an electron donor: a case study.

Contamination by 2,4,6-trinitrotoluene (TNT), an explosive extensively used by the military, represents a serious environmental problem. In this study, whey has been selected as the most technologically and economically suitable primary substrate for anaerobic in situ biodegradation of TNT. Under laboratory conditions, various additions of whey, molasses, acetate and activated sludge as an inoculant were tested and the process was monitored using numerous chemical analyses including phospholipid fatty acid analysis. The addition of whey resulted in the removal of more than 90% of the TNT in real contaminated soil (7 mg kg(-1) and 12 mg kg(-1) of TNT). The final bioremediation strategy was suggested on the basis of the laboratory results and tested under real conditions at a TNT contaminated site in the Czech Republic. During the pilot test, three repeated injections of whey suspension into the sandy aquifer were performed over a 10-month period. In total, approximately 5m(3) of whey were used. A substantial decrease in the TNT groundwater concentration from the original levels (equalling 1.49 mg l(-1) to 8.58 mg l(-1)) was observed in most of the injection wells, while the concentrations of the TNT biotransformation products were found to be elevated. Pilot-scale application results showed that the anoxic and/or anaerobic conditions in the aquifer were sufficient for TNT bio-reduction by autochthonous microorganisms. Whey application was not accompanied by undesirable effects such as a substantial decrease in the pH or clogging of the wells. The results of the study document the suitability of application of whey to bioremediate TNT contaminated sites in situ.

Graphene oxide-based optical biosensor functionalized with peptides for explosive detection.

A label-free optical biosensor was constructed with biofunctionalized graphene oxide (GO) for specific detection of 2,4,6-trinitrotoluene (TNT). By chemically binding TNT-specific peptides with GO, the biosensor gained unique optoelectronic properties and high biological sensitivity, with transducing bimolecular bonding into optical signals. Through UV absorption detection, increasing absorbance responses could be observed in presence of TNT at different concentrations, as low as 4.40×10(-9) mM, and showed dose-dependence and stable behavior. Specific responses of the biosensor were verified with the corporation of 2,6-dinitrotoluene (DNT), which had similar molecular structure to TNT. Thus, with high sensitivity and selectivity, the biosensor provided a convenient approach for detection of explosives as miniaturizing and integrating devices.

TNT and RDX degradation and extraction from contaminated soil using subcritical water.

The use of explosives either for industrial or military operations have resulted in the environmental pollution, poses ecological and health hazard. In this work, a subcritical water extraction (SCWE) process at laboratory scale was used at varying water temperature (100-175 °C) and flow rate (0.5-1.5 mL min(-1)), to treat 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) contaminated soil, to reveal information with respect to the explosives removal (based on the analyses of soil residue after extraction), and degradation performance (based on the analyses of water extracts) of this process. Continuous flow subcritical water has been considered on removal of explosives to avoid the repartitioning of non-degraded compounds to the soil upon cooling which usually occurs in the batch system. In the SCWE experiments, near complete degradation of both TNT and RDX was observed at 175 °C based on analysis of water extracts and soil. Test results also indicated that TNT removal of >99% and a complete RDX removal were achieved by this process, when the operating conditions were 1 mL min(-1), and treatment time of 20 min, after the temperature reached 175 °C. HPLC-UV and ion chromatography analysis confirmed that the explosives underwent for degradation. The low concentration of explosives found in the process wastewater indicates that water recycling may be viable, to treat additional soil. Our results have shown in the remediation of explosives contaminated soil, the effectiveness of the continuous flow SCWE process.

Preparation of magnetic TNT-imprinted polymer nanoparticles and their accumulation onto magnetic carbon paste electrode for TNT determination.

In this study, the TNT-imprinted polymer shell was created on nano-sized Fe3O4 cores in order to construct the nano-sized magnetic molecularly imprinted polymer (nano-MMIP). For this purpose, the surface of the synthesized magnetic nanoparticles was modified with methacrylic acid. The modified particles were then utilized as the core on which the TNT-imprinted polymeric shell was synthesized. The synthesized materials were then characterized by scanning electron microscopy, FT-IR and thermal gravimetric analysis (TGA). The resulting nano-MMIP particles were suspended in TNT solution and then collected on the surface of a carbon paste electrode via a permanent magnet, situated within the CP electrode. The extracted TNT was analyzed on the CP electrode by applying square wave voltammetry (SWV). It was found that the oxidative signal of TNT is much favorable for TNT detection on the resulting magnetic carbon paste electrode. The electrode with nano-MMIP showed distinctly higher signal to TNT, compared to that containing magnetic non-imprinted polymer (MNIP) nanoparticles. All parameters influencing the method performance including extraction pH, extraction time and sorbent amount were evaluated and optimized. The developed method showed a dynamic linear concentration range of 1.0-130.0 nM for TNT measurement. The detection limit of the method was calculated to be 0.5 nM. The method showed appropriate capability for TNT analysis in real water samples.

Screen-printed electrode-based electrochemical detector coupled with in-situ ionic-liquid-assisted dispersive liquid-liquid microextraction for determination of 2,4,6-trinitrotoluene.

A novel method is reported, whereby screen-printed electrodes (SPELs) are combined with dispersive liquid-liquid microextraction. In-situ ionic liquid (IL) formation was used as an extractant phase in the microextraction technique and proved to be a simple, fast and inexpensive analytical method. This approach uses miniaturized systems both in sample preparation and in the detection stage, helping to develop environmentally friendly analytical methods and portable devices to enable rapid and onsite measurement. The microextraction method is based on a simple metathesis reaction, in which a water-immiscible IL (1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, [Hmim][NTf2]) is formed from a water-miscible IL (1-hexyl-3-methylimidazolium chloride, [Hmim][Cl]) and an ion-exchange reagent (lithium bis[(trifluoromethyl)sulfonyl]imide, LiNTf2) in sample solutions. The explosive 2,4,6-trinitrotoluene (TNT) was used as a model analyte to develop the method. The electrochemical behavior of TNT in [Hmim][NTf2] has been studied in SPELs. The extraction method was first optimized by use of a two-step multivariate optimization strategy, using Plackett-Burman and central composite designs. The method was then evaluated under optimum conditions and a good level of linearity was obtained, with a correlation coefficient of 0.9990. Limits of detection and quantification were 7 µg L(-1) and 9 µg L(-1), respectively. The repeatability of the proposed method was evaluated at two different spiking levels (20 and 50 µg L(-1)), and coefficients of variation of 7 % and 5 % (n = 5) were obtained. Tap water and industrial wastewater were selected as real-world water samples to assess the applicability of the method.

Pathways for degrading TNT by Thu-Z: a Pantoea sp. strain.

2,4,6-Trinitrotoluene (TNT), an extensively used and versatile explosive, is harmful in soil and water. In the present study, four bacterial strains capable of degrading TNT have been isolated from contaminated sites and named as Thu-A, Thu-B, Thu-C, and Thu-Z. Thu-Z, which gave the highest degradation efficiency compared to the others, was assigned to the genus Pantoea according to its 16S rRNA gene. Similarities in both biochemical properties and morphology suggested that Thu-Z was a Pantoea sp. strain. Thu-Z was proved to be capable of using TNT as a sole nitrogen source by cleaving NO(2) from the nitroaromatic ring by direct aromatic ring reduction. Under nitrogen-limited conditions, 96.6 % N of TNT was consumed by Thu-Z for growth, which was determined in terms of NaNO(2). Trace nitro reduction metabolites such as 2,4-diamino-6-nitrotoluene (24Dam) and 2,6-diamino-4-nitrotoluene (26Dam) were identified in the presence of (NH(4))(2)SO(4). On the other hand, 4,4',6,6'-tetranitro-2,2'-azoxytoluene (22Azo) and 2,2',6,6'-tetranitro-4,4'-azoxytoluene (44Azo) were detected in the absence of (NH(4))(2)SO(4). These indicated the existence of a dual pathway for Thu-Z, while the direct aromatic ring reduction was predominant. Addition of a nitrogen source ((NH(4))(2)SO(4)) after inoculation stimulated the growth of Thu-Z and accelerated TNT degradation.

Characterization of thermal desorption instrumentation with a direct liquid deposition calibration method for trace 2,4,6-trinitrotoluene quantitation.

The use of thermal desorption systems for the analysis of trace vapors typically requires establishing a calibration curve from vapors generated with a permeation tube. The slow equilibration time of permeation tubes causes such an approach to become laborious when covering a wide dynamic range. Furthermore, many analytes of interest, such as explosives, are not available as permeation tubes. A method for easily and effectively establishing calibration curves for explosive vapor samples via direct deposition of standard solutions on thermal desorption tubes was investigated. The various components of the thermal desorption system were compared to a standard split/splitless inlet. Calibration curves using the direct liquid deposition method with a thermal desorption unit coupled to a cryo-focusing inlet were compared to a standard split/splitless inlet, and a statistical difference was observed but does not eliminate or deter the use of the direct liquid deposition method for obtaining quantitative results for explosive vapors.

Retention of 2,4,6-trinitrotoluene and heavy metals from industrial waste water by using the low cost adsorbent pine bark in a batch experiment.

Pine bark is a low cost sorbent originating from the forest industry. In recent years, it has been found to show promise as an adsorbent for metals and organic substances in contaminated water, especially landfill leachates and storm water. This study aims to investigate if pine bark can replace commercial adsorbents such as active carbon. An industrial effluent, collected from a treatment plant of a demilitarization factory, was diluted to form concentration ranges of contaminants and shaken with pine bark for 24 hours. Metals (e.g. Pb, Zn, Cd, As and Ni) and explosives, e.g., 2,4,6-trinitrotoluene (TNT), were analysed before and after treatment. The aim of the experiment was twofold; firstly, it was to investigate whether metals are efficiently removed in the presence of explosives and secondly, if adsorption of explosive substances to pine bark was possible. Langmuir and Freundlich isotherms were used to describe the adsorption process where this was possible. It was found that metal uptake was possible in the presence of TNT and other explosive contaminants. The uptake of TNT was satisfactory with up to 80% of the TNT adsorbed by pine bark.

2,4,6-Trinitrophenol degradation by Bacillus cereus isolated from a firing range.

Bacillus cereus strain PU, isolated from soil contaminated with explosive waste, tolerated up to 1.3 mM 2,4,6 trinitrophenol (TNP) and utilize it aerobically as sole nitrogen and carbon source. Degradation of TNP was accompanied by stoichiometric release of 2.1 ± 0.15 mol nitrite/mol TNP at 539 µmol/h g dry cell wt. Metabolism of TNP was accompanied by transient accumulation of an orange-red metabolite, hydride meisenheimer complex (H-TNP), indicating a metabolic pathway involving complete reductive removal of the nitro group as nitrite.

Organic pollutants removal from 2,4,6-trinitrotoluene (TNT) red water using low cost activated coke.

We treated 2,4,6-trinitrotoluene (TNT) red water from the Chinese explosive industry with activated coke (AC) from lignite. Since the composition of TNT red water was very complicated, chemical oxygen demand (COD) was used as the index for evaluating treatment efficiency. This study focused on sorption kinetics and equilibrium sorption isotherms of AC for the removal of COD from TNT red water, and the changes of water quality before and after adsorption were evaluated using high performance liquid chromatography, UV-Vis spectra and gas chromatography/mass spectroscopy. The results showed that the sorption kinetics of COD removal from TNT red water onto AC fitted well with the pseudo second-order model. The adsorption process was an exothermic and physical process. The sorption isotherm was in good agreement with Redlich-Peterson isotherm. At the conditions of initial pH = 6.28, 20 degrees C and 3 hr of agitation, under 160 g/L AC, 64.8% of COD was removed. The removal efficiencies of 2,4-dinitrotoluene-3-sulfonate (2,4-DNT-3-SO3-) and 2,4-dinitrotoluene-5-sulfonate (2,4-DNT-5-SO3-) were 80.5% and 84.3%, respectively. After adsorption, the acute toxicity of TNT red water reduced greatly, compared with that of unprocessed TNT red water.

Removal of dinitrotoluenes and trinitrotoluene from industrial wastewater by ultrasound enhanced with titanium dioxide.

Oxidative degradation of dinitrotoluenes (DNTs) and 2,4,6-trinitrotoluene (TNT) in wastewater was conducted using ultrasonic irradiation combined with titanium dioxide (TiO(2)). The batch-wise experiments were carried out to elucidate the influence of various operating parameters on the sonolytic behavior, including power intensity, TiO(2) dosage, acidity of wastewater, reaction temperature and oxygen dosage. It is worthy to note that the nitrotoluene contaminants could be almost completely eliminated by sonochemical oxidation enhanced significantly with the addition of TiO(2) due to the supply of adsorbent and/or excess nuclei. High destruction rate of nitrotoluenes could be achieved by increasing the acidity of wastewater and decreasing the reaction temperature. According to the result given by pyrolysis/gas chromatograph-mass spectrometer (Pyrolysis/GC-MS), it is postulated that DNTs adsorbed on TiO(2) preliminarily undergo denitration pathway to o-mononitrotoluene (MNT) or oxidation pathway to 1,3-dinitrobenzene (DNB), respectively. Further, based on the spectra obtained from GC-MS, it is proposed that DNTs dissolved in wastewater proceed with similar reaction pathways as those adsorbed on TiO(2). Besides, oxidative degradation of 2,4,6-TNT results in the formation of 1,3,5-trinitrobenzene (TNB). Apparently, the sonolytic technique established is promising for direct treatment of wastewater from TNT manufacturing process.

Desorption of nitramine and nitroaromatic explosive residues from soils detonated under controlled conditions.

Potentially toxic nitroaromatic and nitramine compounds are introduced onto soils during detonation of explosives. The present study was conducted to investigate the desorption and transformation of explosive compounds loaded onto three soils through controlled detonation. The soils were proximally detonated with Composition B, a commonly used military explosive containing 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). Gas-exchangeable surface areas were measured from pristine and detonated soils. Aqueous batches of detonated soils were prepared by mixing each soil with ultrapure water. Samples were collected for 141 d and concentrations of Composition B compounds and TNT transformation products 2-amino-4,6-dinitrotoluene (2ADNT), 4-amino-2,6-dinitrotoluene (4ADNT), and 1,3,5-trinitrobenzene (1,3,5-TNB) were measured. The RDX, HMX, and TNT concentrations in detonated soil batches exhibited first-order physical desorption for the first, roughly, 10 d and then reached steady state apparent equilibrium within 40 d. An aqueous batch containing powdered Composition B in water was sampled over time to quantify TNT, RDX, and HMX dissolution from undetonated Composition B particles. The TNT, RDX, and HMX concentrations in aqueous batches of pure Composition B reached equilibrium within 6, 11, and 20 d, respectively. Detonated soils exhibited lower gas-exchangeable surface areas than their pristine counterparts. This is likely due to an explosive residue coating on detonated soil surfaces, shock-induced compaction, sintering, and/or partial fusion of soil particles under the intense heat associated with detonation. Our results suggest that explosive compounds loaded to soils through detonation take longer to reach equilibrium concentrations in aqueous batches than soils loaded with explosive residues through aqueous addition. This is likely due to the heterogeneous interactions between explosive residues and soil particle surfaces.

Attenuation of TNT in seawater microcosms.

The ability of two differing marine sediments (one clayey, the other sandy) to attenuate the explosive 2,4,6-trinitrotoluene (TNT), dissolved in intertidal seawater from the eastern English coast of the North Sea, was examined using aerobic microcosms. Analysis of the seawater from the microcosms revealed an initial sharp decline in TNT concentration with clayey sediment in both sterilized (to prevent microbial activity) and unsterilized microcosms. This effect did not occur to such a marked extent in similar sterile and non-sterile sandy sediment microcosms and was attributed mainly to sorption of TNT to the fine clay particles of the clayey sediment. As time progressed, the attenuation of TNT in microcosms containing either type of sediment was found to be less in those that had been sterilized compared with those where microbial action proceeded unhindered. Feeding the microcosms, (i.e. supplying extra carbon sources for the microbial communities), appeared to have a small, but perceptible, enhancing effect upon TNT dissipation. The attenuation of TNT was also measured in large microcosms containing 2.5 L of seawater and no sediment. Analysis of the seawater revealed a gradual decline in TNT concentration in non-sterile and fed microcosms compared to their sterile counterpart. Overall, this laboratory study showed that the attenuation of TNT is slow (half-life in seawater ca.1900 days; half-life sand sediment <700 days; half life in clay sediment 130 days) under conditions commonly encountered in coastal waters of the North Sea.

Macroporous silica for concentration of nitroenergetic targets.

Hierarchical organosilicate sorbents were synthesized which possess structure on two length scales: macropores of approximately 1microm lined by mesopores (35-45A). The incorporation of macropores provides enhanced flow-through characteristics over purely mesoporous materials, thereby reducing back pressure when used in column formats. Materials of this type with varied surface groups were applied to the adsorption of 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) in both batch and column formats. The results presented here demonstrate the potential of these materials for application as solid phase extraction materials for the pre-concentration of nitroenergetic targets from aqueous solutions. The structural and binding characteristics of the materials have been evaluated and preliminary data on the impact of complex matrices is provided.

Dynamic planar solid phase microextraction-ion mobility spectrometry for rapid field air sampling and analysis of illicit drugs and explosives.

A preconcentration device that targets the volatile chemical signatures associated with illicit drugs and explosives (high and low) has been designed to fit in the inlet of an ion mobility spectrometer (IMS). This is the first reporting of a fast and sensitive method for dynamic sampling of large volumes of air using planar solid phase microextraction (PSPME) incorporating a high surface area for absorption of analytes onto a sol-gel polydimethylsiloxane (PDMS) coating for direct thermal desorption into an IMS. This device affords high extraction efficiencies due to strong retention properties at ambient temperature, resulting in the detection of analyte concentrations in the parts per trillion range when as low as 3.5 L of air are sampled over the course of 10 s (absolute mass detection of less than a nanogram). Dynamic PSPME was used to sample the headspace over the following: 3,4-methylenedioxymethamphetamine (MDMA) tablets resulting in the detection of 12-40 ng of piperonal, high explosives (Pentolite) resulting in the detection of 0.6 ng of 2,4,6-trinitrotoluene (TNT), and low explosives (several smokeless powders) resulting in the detection of 26-35 ng of 2,4-dinitrotoluene (2,4-DNT) and 11-74 ng of diphenylamine (DPA).

[Determination of 2,4,6-trinitromethylbenzene in biological material].

The objective of this study was to search for the optimal conditions necessary to extract 2,4,6-trinitromethylbenzene (2,4,6-TNMB) from biological material with acetonitrile. It is shown that 2,4,6-TNMB can be purified from the coextracted components of the biological material on a silica gel column, L 40/100 mcm. Methods are described for the identification and quantitative measurement of 2,4,6-trinitromethylbenzene in the cadaveric liver tissue by thin layer paper chromatography, IR spectrophotometry, and reverse phase high-performance liquid chromatography (rp-HPLC) with the use of a diode-matrix detector.