An Ultrasound-Fenton Process for the Degradation of 2,4,6-Trinitrotoluene.

2,4,6-Trinitrotoluene (TNT), one of the main compounds in ammunition wastewater, is harmful to the environment. In this study, the treatment efficiency of 2,4,6-TNT by different treatment processes, including ferrous ion (Fe2+), hydrogen peroxide (H2O2), Fenton, ultrasound (US) irradiation, US + Fe2+, US + H2O2 and US-Fenton process, was compared. The results showed that US-Fenton was the most effective among all methods studied. The effects of initial pH, reaction time and H2O2 to Fe2+ molar ratio were investigated. The results showed that the removal of TNT, TOC and COD was maximum at an initial pH of 3.0 and H2O2 to Fe2+ molar ratio of 10:1. TNT, TOC and COD removal was fast in the first 30 min, reaching 83%, 57% and 50%, then increased gradually to 99%, 67% and 87% until 300 min, respectively. Semi-batch mode operation increased the removal of TNT and TOC by approximately 5% and 10% at 60 min, respectively. The average carbon oxidation number (ACON) was increased from -1.7 at 30 min to a steady-state value of 0.4, indicating the mineralization of TNT. Based on GC-MS analysis, 1,3,5-trinitrobenzene, 2,4,6-trinitrobenzene acid, 3,5-dinitrobenznamine and 3,5-dinitro-p-toluidine were the major byproducts from the US-Fenton process. The TNT degradation pathway was proposed, which involved methyl group oxidation, decarboxylation, aromatic ring cleavage and hydrolysis.

13C and 15N NMR identification of product compound classes from aqueous and solid phase photodegradation of 2,4,6-trinitrotoluene.

Photolysis is one of the main transformation pathways for 2,4,6-trinitrotoluene (TNT) released into the environment. Upon exposure to sunlight, TNT is known to undergo both oxidation and reduction reactions with release of nitrite, nitrate, and ammonium ions, followed by condensation reactions of the oxidation and reduction products. In this study, compound classes of transformation products from the aqueous and solid phase photodegradation of 2,4,6-trinitrotoluene (TNT) have been identified by liquid and solid state 13C and 15N NMR. Aqueous phase experiments were performed on saturated solutions of T15NT in deionized water, natural pond water (pH = 8.3, DOC = 3.0 mg/L), pH 8.0 buffer solution, and in the presence of Suwannee River Natural Organic Matter (SRNOM; pH = 3.7), using a Pyrex-filtered medium pressure mercury lamp. Natural sunlight irradiations were performed on TNT in the solid phase and dissolved in the pond water. In deionized water, carboxylic acid, aldehyde, aromatic amine, primary amide, azoxy, nitrosophenol, and azo compounds were formed. 15N NMR spectra exhibited major peaks centered at 128 to 138 ppm, which are in the range of phenylhydroxylamine and secondary amide nitrogens. The secondary amides are proposed to represent benzanilides, which would arise from photochemical rearrangement of nitrones formed from the condensation of benzaldehyde and phenylhydroxylamine derivatives of TNT. The same compound classes were formed from sunlight irradiation of TNT in the solid phase. Whereas carboxylic acids, aldehydes, aromatic amines, phenylhydroxylamines, and amides were also formed from irradiation of TNT in pond water and in pH 8 buffer solution, azoxy and azo compound formation was inhibited. Solid state 15N NMR spectra of photolysates from the lamp irradiation of unlabeled 2,6-dinitrotoluene in deionized water also demonstrated the formation of aromatic amine, phenylhydroxylamine/ 2° amide, azoxy, and azo nitrogens.

UV-FIA: UV-induced fluoro-immunochemical assay for ultra-trace detection of PETN, RDX, and TNT.

Fluorescence quenching based immunoassay format for the detection of a trace amount of some nitro-explosives with a high degree of selectivity is reported in this study. The immunoassay comprises anti-explosive antibodies functionalized microtitre strips specific to the targeted explosives, pentaerythritol tetranitrate (PETN), 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), and 2,4,6-trinitrotoluene (TNT). UV induced photolysis of nitro-explosive bound to targeted antibodies generates primarily nitrite ions which after the quick reaction with the detector molecule, 2,3-diaminonaphthalene (DAN), a fluorophore, quenches its fluorescence intensity, however, proportionately undergo cyclization to produce a highly fluorescent product, 2,3-naphthotriazole (NAT). The synthesized product, NAT, was verified using various chromatographic and spectrophotometric techniques. This newly developed antibody-based detection method, utilizing DAN dye, demonstrated a high selectivity towards PETN, RDX, and TNT. This method can be used as an economical testing kit for direct quantification of explosives, implying the great potential for quick, low-cost trace detection of explosives.

Factorial design application in photocatalytic wastewater degradation from TNT industry-red water.

In trinitrotoluene (TNT) purification process, realized in industries, there are two washes carried out at the end of the procedure. The first is performed with vaporized water, from which the first effluent, called yellow water, is originated. Then, a second wash is performed using sodium sulfite, generating the red water effluent. The objective of this work was to get the best conditions for photocatalytic degradation of the second effluent, red water, in order to reduce toxicity and adjust legal parameters according to regulatory agencies for dumping these effluents into waterways. It has used a statistical evaluation for factor interaction (pH, concentration) that affects heterogeneous photocatalysis with titanium dioxide (TiO2). Thus, the treatment applied in the factorial experimental design consisted of using a volume equal to 500 mL of the effluent to 0.1 % by batch treatment, which has changed TiO2 pH and concentration, according to the design, with 20 min time for evaluation, where it was used as response to the reduction of UV-Vis absorption. According to the design responses, it has obtained optimum values for the parameters evaluated: pH = 6.5 and concentration of 100 mg/L of TiO2 were shown to be efficient when applied to red water effluent, obtaining approximately 91 % of discoloration.

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.

Effects of additives on 2,4,6-trinitrotoluene (TNT) removal and its mineralization in aqueous solution by gamma irradiation.

The effects of additives (i.e., methanol, EDTA, mannitol, thiourea, nitrous oxide, oxygen and ozone) on gamma irradiation of 2,4,6-trinitrotoluene (TNT) were investigated to elucidate the initial reaction mechanism of TNT degradation and suggest an practical method for complete by-product removal. All additives, except thiourea, significantly increased the TNT removal efficiency by gamma irradiation. The overall results of the additive experiments implied that the TNT decomposition would be initiated by *OH, e(aq)(-), and HO(2*)/O(2*)(-), and also implied that *H did not have any direct effect on the TNT decomposition. Additions of methanol and nitrous oxide were more effective in TNT removal than the other additives, achieving complete removal of TNT at doses below 20 kGy. Total organic carbon (TOC) of the irradiated solution was analyzed to evaluate the degree of TNT mineralization under the additive conditions. TOC under the nitrous oxide addition was removed rapidly, and complete TNT mineralization was thus achieved at 50 kGy. Methanol addition was very effective in the TNT removal, but it was not effective in reduction in TOC. Trinitrobenzene (TNB), oxalic acid and glyoxalic acid were detected as radiolytic organic by-products, while ammonia and nitrate were detected as radiolytic inorganic by-products. The most efficient TNT removal and its mineralization by gamma irradiation would be achieved by supersaturating the solution with nitrous oxide before irradiation.

Femtosecond and nanosecond laser-induced breakdown spectroscopy of trinitrotoluene.

Femtosecond and nanosecond laser-induced breakdown spectroscopy (LIBS) were used to study trinitrotoluene (TNT) deposited on aluminum substrates. Over the detection wavelength range of 200-785 nm, we have observed emission from CN and C(2) molecules as the marker for the explosive with femtosecond LIBS. In contrast, the signal for nanosecond LIBS of TNT is dominated by emission from the elemental constituents of the explosive. Aluminum emission lines from the substrate are also observed with both femtosecond and nanosecond excitation and indicate the role played by the substrate in the interaction.

Explosives: fate, dynamics, and ecological impact in terrestrial and marine environments.

An explosive or energetic compound is a chemical material that, under the influence of thermal or chemical shock, decomposes rapidly with the evolution of large amounts of heat and gas. Numerous compounds and compositions may be classified as energetic compounds; however, secondary explosives, such as TNT, RDX, and HMX pose the largest potential concern to the environment because they are produced and used in defense in the greatest quantities. The environmental fate and potential hazard of energetic compounds in the environment is affected by a number of physical, chemical, and biological processes. Energetic compounds may undergo transformation through biotic or abiotic degradation. Numerous organisms have been isolated with the ability to degrade/transform energetic compounds as a sole carbon source, sole nitrogen source, or through cometabolic processes under aerobic or anaerobic conditions. Abiotic processes that lead to the transformation of energetic compounds include photolysis, hydrolysis, and reduction. The products of these reactions may be further transformed by microorganisms or may bind to soil/sediment surfaces through covalent binding or polymerization and oligomerization reactions. Although considerable research has been performed on the fate and dynamics of energetic compounds in the environment, data are still gathering on the impact of TNT, RDX, and HMX on ecological receptors. There is an urgent need to address this issue and to direct future research on expanding our knowledge on the ecological impact of energetic transformation products. In addition, it is important that energetic research considers the concept of bioavailability, including factors influencing soil/sediment aging, desorption of energetic compounds from varying soil and sediment types, methods for modeling/predicting energetic bioavailability, development of biomarkers of energetic exposure or effect, and the impact of bioavailability on ecological risk assessment.

Decomposition of dinitrotoluene isomers and 2,4,6-trinitrotoluene in spent acid from toluene nitration process by ozonation and photo-ozonation.

Ozone and UV/O3 were employed to mineralize dinitrotoluene (DNT) isomers and 2,4,6-trinitrotoluene (TNT) in spent acid from toluene nitration process. The oxidative degradation tests were carried out to elucidate the influence of various operating variables on the performance of mineralization of total organic compounds (TOC) in spent acid, including reaction temperature, intensity of UV (254 nm) irradiation, dosage of ozone and concentration of sulfuric acid. It is remarkable that the nearly complete mineralization of organic compounds can be achieved by ozonation combined with UV irradiation. Nevertheless, the hydroxyl radicals (*OH) would not be generated by either ozone decomposition or photolysis of ozone under the experimental condition of this study. According to the spectra identified by gas chromatograph/mass spectrometer (GC/MS) and further confirmed by gas chromatograph/flame ionization detector (GC/FID), the multiple oxidation pathways of DNT isomers are given, which include o-, m-, p-mononitrotoluene (MNT) and 1,3-dinitrobenzene, respectively. In addition, oxidative degradation of 2,4,6-TNT leads to a 1,3,5-trinitrobenzene intermediate.

Phototransformation of 2,4,6-trinitrotoluene: sensitized by riboflavin under different irradiation spectral range.

Riboflavin-sensitized phototransformation of 2,4,6-trinitrotoluene (TNT) under natural sunlight was investigated with reverse-phase high performance liquid chromatography/mass spectrometry (HPLC/MS) and gas chromatography/mass spectrometry (GC/MS). The effect of different spectral region of sunlight on TNT phototransformation in the absence or presence of riboflavin was also investigated by using optical filters with cut-off at 400 or 455 nm. The concentration of riboflavin in the phototransformation of TNT was optimized. Concentration of riboflavin and TNT was 1.0 and 50 microM, respectively. The rates of phototransformation of TNT under natural sunlight in the presence or absence of riboflavin were conformed to initial pseudo-first-order rate equation. The photolysis half life of TNT in the presence of riboflavin was 21.87 min, compared to 39 min in the absence of riboflavin under natural sunlight. Two major phototransformation products of TNT, 3,5-dinitroaniline (3,5-DNA) and 1,3,5-trinitrobenzene (1,3,5-TNB), were detected in the samples in the presence of riboflavin receiving irradiation at full wavelength or wavelength >400 nm. The results indicate that riboflavin mediates TNT sensitized-phototransfomation under natural sunlight or near-UV-vis light.

Photocatalytic demethylation of 2,4,6-trinitrotoluene (TNT) by porphyrins.

Illumination of tetraphenyl porphyrin sulfonate (TPPS), CuTPPs and FeTTPPS in solution with trinitrotoluene (TNT) at pH7 at room temperature using tungsten lamp illumination results in the degradation of TNT to yield trinitrobenzoic acid and trinitrobenzene. No other degradation products are observed. The rate of TNT degradation follows the series TPPS > FeTPPS > CuTPPS.

Decomposition of 2,4,6-trinitrotoluene (TNT) by gamma irradiation.

The purpose of this study was to evaluate the potential of gamma irradiation to decompose 2,4,6-trinitrotoluene (TNT) in an aqueous solution; the concentration range of the TNT solution was 0.11-0.44 mmol/L. The decomposition rate of TNT by gamma irradiation was pseudo-first-order kinetic over the applied initial concentrations. The dose constant was strongly dependent on the initial concentration of TNT. Increasing the concentration of dissolved oxygen in the solution was more effective on the decomposition of TNT as well as its mineralization. The required irradiation dose to remove 90% of initial TNT (0.44 mmol/L) was 58, 41, 32, 28, and 25 kGy at the dissolved oxygen concentration of 0.025, 0.149, 0.3, 0.538, and 0.822 mmol/L, respectively. However, TOC still remained as 30% of the initial TOC (3.19 mmol/L) when 200 kGy irradiation dose was applied to the TNT solution (0.44 mmol/L) containing dissolved oxygen of 0.822 mmol/L. The removal of the TNT was more efficient at a pH below 3 and at a pH above 11 than at neutral pH (pH 5-9). The required irradiation dose to remove over 99% of the initial TNT (0.44 mmol/L) was 39, 76, and 10 kGy at pH 2, 7, and 13, respectively. The dose constant was increased 1.6-fold and over 15.6-fold at pH 2 and 13, respectively, compared to that at pH 7. When an irradiation dose of 200 kGy was applied, the removal efficiencies of the TOC (initial concentration 3.19 mmol/L) were 91, 46, and 53% at pH 2, 7, and 13, respectively. Ammonia and nitrate were detected as the main nitrogen byproducts of TNT, and glyoxalic acid and oxalic acid were detected as organic byproducts.

Mineralization of dinitrotoluenes and trinitrotoluene of spent acid in toluene nitration process by Fenton oxidation.

Fenton's reagent, UV/H2O2 and UV/Fenton's reagent were employed to mineralize dinitrotoluene (DNT) isomers and 2,4,6-trinitrotoluene (TNT) of spent acid in toluene nitration process. The bench-scale experiments were conducted to elucidate the influence of various operating variables on the performance of removal of total organic compounds (TOC) from spent acid, including reaction temperature, concentration of ferrous ion and H2O2 dosage. It is remarkable that organic compounds were completely mineralized by Fenton oxidation, of which removal efficiency is superior to that of UV/H2O2. Nevertheless, it makes slight difference between Fenton oxidation and UV/Fenton oxidation. According to the spectra identified by gas chromatograph/mass spectrometer (GC/MS), it is proposed that oxidative degradation of DNT isomers leads to o-, m-, p-mononitrotoluene (MNT) and 1,3-dinitrobenzene respectively. Besides, the oxidation of 2,4,6-TNT gives the 1,3,5-trinitrobenzene intermediate. Apparently, Fenton oxidation is promising for purification of spent acid industrially.