Microwave-assisted hydrolysis of nitroglycerin (NG) under mild alkaline conditions: new insight into the degradation pathway

Nitroglycerin trapping in melamine matrices

Melamine (Mel) was used as host matrix for liquid nitroglycerin (NG), to prepare Mel/NG solid powdered compounds containing up to 45 wt% of this explosive. The two preparation processes used for this purpose consisted in evaporating a solution of both components, either in ambient conditions or under reduced pressure by the Spray Flash-Evaporation (SFE) process. In Mel/NG materials, amorphous nitroglycerin is distributed in the crystallized melamine matrix as inclusions, which were found to be smaller in size in the material prepared by the SFE process. Mel/NG materials are not stable over time: they gradually lose the nitroglycerin they contain by evaporation.

Development of microwave-assisted nitrogen-modified activated carbon for efficient biogas desulfurization: a practical approach

Removal of H₂S (hydrogen sulfide) from biogas is anticipated for higher energy conversion of methane (CH₄), while reducing the detrimental impacts of corroding the metal parts in the plant and its hazardous effect on humans and the environment. The introduction of microwave (MW) heating and nitrogen-modification could generate superior adsorbent features, contributing to high H₂S removal. Up to date, there is no work reported on the influence of physicochemical characteristics of nitrogen-modified carbon synthesized via MW and conventional heating (TH) methods and their performance in H₂S removal. Palm shell activated carbon (PSAC) was functionalized with nitrogen groups via urea impregnation, followed by the synthesis of MW and TH at 950 °C, 500 ml/min of N₂ flow rate and 30 min of heating time. MW and TH heating effects on the modified PSAC adsorbent were analysed and compared towards hydrogen sulfide (H₂S) removal. PSAC with nitrogen functionalization produced using MW heating (PSAC-MW) demonstrates superior performance, with an adsorption capacity of 356.94 mg/g. The adsorbent sample generated using MW heating exhibited notable properties, including a large surface area and a sponge-like structure, with new pores developed within the current pores. Instead of that, there was an observation of 'hot spot' appearance during the MW heating process, which is believed to be responsible for the development of physical and chemical characteristics of the adsorbent. Thus, it is believed that MW heating was assisted in the development of the adsorbent's properties and at the same time contributed to the high removal of H₂S at low adsorption temperature. The utilization of biomass-based adsorbent (PSAC) for H₂S removal can address the lignocellulosic waste disposal problem, while mitigating the H₂S release from the biogas production plants thus has several environmental merits. This indirectly contributed to zero-waste generation, while overcoming the adverse effects of H₂S.

A simple and safe approach for simultaneous spectrophotometric determination of nitroglycerin and nitrocellulose in double base solid propellants

An accurate, simple and safe method was developed for simultaneous determination of nitroglycerine (NG) and nitrocellulose (NC) in double base solid propellants (DB propellants). The proposed method is based on alkaline hydrolysis of NG and NC, and followed by colored reaction of released nitrite ion with p-nitroaniline in the presence of diphenylamine in acidic media and produce azo dye. The absorbance of the azo dye was measured at 534 nm. Two sets of reaction conditions were developed. In the first set, at room temperature, only NG was hydrolyzed and calibration curve obtained. In the second set, at 60 ℃, NG and NC were hydrolyzed simultaneously. Based on obtained amount for the NG at room temperature, and total amount of NG and NC at 60 ℃, the amount of NC was determined by using stoichiometric equations. The calibration curve was linear over the concentration ranges of 0.2-5.0, 0.5-10 μg mL^-1 for NG and NC, respectively. The proposed method was successfully applied for the determination of NG and NC in DB propellants with good recoveries ranged from 99 to 101%, and RSD less than 2.0%. The method statistically compared based on t- and F-tests with those obtained in according to military standard method (MIL-STD-286). The results showed that the proposed method offers an accuracy and reliable approach for the determination of these compounds in DB propellants, and can be suggested as a routine method in military quality control laboratories.

Liquid Chromatographic Method Development for Quantification of Inorganic Nitrite and Nitrate Impurities from Nitroglycerin Drug Substance by Using Ion-Pair Reagents with Liquid-Liquid Extraction Technique

A large number of laboratory studies have reported Nitrite (NO2-) and Nitrate (NO3-) to be among the most common degradation products of the high-explosive Nitroglycerin drug substance. A novel, simple, robust and rapid reversed-phase high-performance liquid chromatography method has been developed for quantification of inorganic Nitrite and Nitrate impurities from Nitroglycerin drug substance. Successful separation was achieved in isocratic elution, using Inertsil C8-3, (250 × 4.6 mm, 5.0 μm) column, with mobile phase consisting of pH 7.0 tetrabutyl ammonium hydrogen sulfate buffer, methanol and acetonitrile (96:02:02, v/v/v). Flow rate was monitored at 2.0 mL min-1 and ultraviolet detection at 220 nm. The present work describes the role of an ion-pair reagent in the separation of polar compounds and liquid-liquid extraction technique for separation of polar and non-polar compounds. Nitroglycerin was subjected to various stress conditions to demonstrate the stability-indicating power of the method. The performance of the method was validated as per present International Council for Harmonisation (ICH) guidelines for specificity, linearity, accuracy, precision, ruggedness and robustness. The developed method can be a valuable alternative to the current ion-exchange chromatographic method mentioned in the literature. To the best of our knowledge, a rapid Liquid Chromatography (LC) method, which separates inorganic Nitrite and Nitrate impurities of Nitroglycerin, disclosed in this investigation was not published elsewhere.

Mechanisms for Abiotic Dechlorination of Trichloroethene by Ferrous Minerals under Oxic and Anoxic Conditions in Natural Sediments

Bench-scale experiments were performed on natural sediments to assess abiotic dechlorination of trichloroethene (TCE) under both aerobic and anaerobic conditions. In the absence of oxygen (<26 μM), TCE dechlorination proceeded via a reductive pathway generating acetylene and/or ethene. Reductive dechlorination rate constants up to 3.1 × 10^-5 d^-1 were measured, after scaling to in situ solid:water ratios. In the presence of oxygen greater than 120 μM, TCE dechlorination proceeded via an oxidative pathway generating formic/glyoxylic and glycolic/acetic acids, and oxidative dechlorination rate constants (again scaled to in situ conditions) up to 7.4 × 10^-3 d^-1 were measured. These rates correspond to half-lives of 60 and 0.25 years for abiotic TCE dechlorination under anaerobic and aerobic conditions, respectively, indicating the potentially large impact of aerobic TCE oxidation in the field. For both reductive and oxidative TCE dechlorination pathways, measured first-order rate constants increased with increasing ferrous iron content, suggesting the role of iron oxidation. Hydroxyl radical formation was measured and increased with increasing oxygen and ferrous iron content. Rate constants associated with TCE oxidation products increased with increasing hydroxyl radical generation rates, and were zero in the presence of a hydroxyl radical scavenger, suggesting that oxidative TCE dechlorination is a hydroxyl radical driven process.

Low hazard small-scale synthesis and chemical analysis of high purity nitroglycerine (NG)

A two-phase batch method to prepare high purity 1,2,3-propanetriyl trinitrate (nitroglycerine, NG) was evaluated, simplified and adapted specifically for low hazard small-scale synthesis.

Nitroglycerin degradation mediated by soil organic carbon under aerobic conditions

The presence of nitroglycerin (NG) has been reported in shallow soils and pore water of several military training ranges. In this context, NG concentrations can be reduced through various natural attenuation processes, but these have not been thoroughly documented. This study aimed at investigating the role of soil organic matter (SOM) in the natural attenuation of NG, under aerobic conditions typical of shallow soils. The role of SOM in NG degradation has already been documented under anoxic conditions, and was attributed to SOM-mediated electron transfer involving different reducing agents. However, unsaturated soils are usually well-oxygenated, and it was not clear whether SOM could participate in NG degradation under these conditions. Our results from batch- and column-type experiments clearly demonstrate that in presence of dissolved organic matter (DOM) leached from a natural soil, partial NG degradation can be achieved. In presence of particulate organic matter (POM) from the same soil, complete NG degradation was achieved. Furthermore, POM caused rapid sorption of NG, which should result in NG retention in the organic matter-rich shallow horizons of the soil profile, thus promoting degradation. Based on degradation products, the reaction pathway appears to be reductive, in spite of the aerobic conditions. The relatively rapid reaction rates suggest that this process could significantly participate in the natural attenuation of NG, both on military training ranges and in contaminated soil at production facilities.

Stable isotopes of nitrate reflect natural attenuation of propellant residues on military training ranges

Nitroglycerin (NG) and nitrocellulose (NC) are constituents of double-base propellants used notably for firing antitank ammunitions. Nitroglycerin was detected in soil and water samples from the unsaturated zone (pore water) at an active antitank firing position, where the presence of high nitrate (NO3(-)) concentrations suggests that natural attenuation of NG is occurring. However, concentrations alone cannot assess if NG is the source of NO3(-), nor can they determine which degradation processes are involved. To address this issue, isotopic ratios (δ(15)N, δ(18)O) were measured for NO3(-) produced from NG and NC through various controlled degradation processes and compared with ratios measured in field pore water samples. Results indicate that propellant combustion and degradation mediated by soil organic carbon produced the observed NO3(-) in pore water at this site. Moreover, isotopic results are presented for NO3(-) produced through photolysis of propellant constituents, which could be a dominant process at other sites. The isotopic data presented here constitute novel information regarding a source of NO3(-) that was practically not documented before and a basis to study the contamination by energetic materials in different contexts.

Biological Denitrification of High Nitrate Processing Wastewaters from Explosives Production Plant

Wastewater samples originating from an explosives production plant (3,000 mg N l(-1) nitrate, 4.8 mg l(-1) nitroglycerin, 1.9 mg l(-1) nitroglycol and 1,200 mg l(-1) chemical oxygen demand) were subjected to biological purification. An attempt to completely remove nitrate and to decrease the chemical oxygen demand was carried out under anaerobic conditions. A soil isolated microbial consortium capable of biodegrading various organic compounds and reduce nitrate to atmospheric nitrogen under anaerobic conditions was used. Complete removal of nitrates with simultaneous elimination of nitroglycerin and ethylene glycol dinitrate (nitroglycol) was achieved as a result of the conducted research. Specific nitrate reduction rate was estimated at 12.3 mg N g(-1) VSS h(-1). Toxicity of wastewater samples during the denitrification process was studied by measuring the activity of dehydrogenases in the activated sludge. Mutagenicity was determined by employing the Ames test. The maximum mutagenic activity did not exceed 0.5. The obtained results suggest that the studied wastewater samples did not exhibit mutagenic properties.

Degradation of trinitroglycerin (TNG) using zero-valent iron nanoparticles/nanosilica SBA-15 composite (ZVINs/SBA-15)

Trinitroglycerin (TNG) is an industrial chemical mostly known for its clinical use in treating angina and manufacturing dynamite. The wide manufacture and application of TNG has led to contamination of vast areas of soil and water. The present study describes degradation of TNG with zero-valent iron nanoparticles (ZVINs) in water either present alone or stabilized on nanostructured silica SBA-15 (Santa Barbara Amorphous No. 15). The BET surface areas of ZVINs/SBA-15 (275.1 m2 g(-1)), as determined by nitrogen adsorption-desorption isotherms, was much larger than the non-stabilized ZVINs (82.0 m2 g(-1)). X-ray diffraction (XRD) showed that iron in both ZVINs and ZVINs/SBA-15 was present mostly in the α-Fe0 crystalline form considered responsible for TNG degradation. Transmission Electron Microscopy (TEM) showed that iron nanoparticles were well dispersed on the surface of the nanosilica support. Both ZVINs and ZVINs/SBA-15 degraded TNG (100%) in water to eventually produce glycerol and ammonium. The reaction followed pseudo-first-order kinetics and was faster with ZVINs/SBA-15 (k1 0.83 min(-1)) than with ZVINs (k1 0.228 min(-1)). The corresponding surface-area normalized rate constants, knorm, were 0.36 and 0.33 L h(-1) m(-2) for ZVINs/SBA-15 and ZVINs, respectively. The ZVINs/SBA-15 retained its original degradation efficiency of TNG after repeatedly reacting with fresh nitrate ester for five successive cycles. The rapid and efficient transformation of TNG with ZVINs/SBA-15, combined with excellent sustained reactivity, makes the nanometal an ideal choice for the clean up of water contaminated with TNG.