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The removal of unsymmetrical dimethylhydrazine (UDMH) has long been a concern because of its harmful effect on the environment and humans. This study aimed to prepare a novel graphene oxide/O-carboxymethyl chitosan (GO/CMC) composite adsorbent using the solution-blending method for the removal of UDMH from wastewater. The prepared GO/CMC was systematically characterized by Fourier-transform infrared, Raman, scanning electronic microscopy, transmission electron microscopy, thermogravimetric, and zeta potential analyses. The effects of initial pH, temperature, adsorbent dosage, initial concentration, contact time, and recyclability on the UDMH adsorption behaviour of GO/CMC were studied. The adsorption kinetics was consistent with the pseudo-second-order kinetics model, and the adsorption process was mainly controlled by chemisorption. Adsorption isotherms indicated that the adsorption of UDMH by GO/CMC followed the Langmuir adsorption isotherm. The adsorption mechanisms were mainly electrostatic attraction, hydrogen bonding, and surface complexation. Furthermore, GO/CMC composites can be used as a renewable and eco-friendly adsorbent for the removal of UDMH wastewater. The designed GO/CMC composites exhibited a relatively satisfactory recyclability and removal efficiency after five adsorption-desorption cycles.

The article presents the results of a study of synthesis and accumulation of heptyl in plants growing on soil contaminated with rocket fuel. The study was carried out under laboratory conditions of al-Farabi Kazakh National University. The results of the experiments confirmed that certain concentrations of a rocket fuel-heptyl (unsymmetrical dimethylhydrazine, UDMH) are not toxic for the crested wheatgrass, Agropyron pectiniforme Roem.et Schult., Kentucky bluegrass, Poa pratensis L., and tarragon, Artemisia terraе-albaе Krasch., although they can cause anatomical and morphological changes in the roots and leaves of plants grown on soil contaminated with UDMH. Changes in the morphological structure of plants under the influence of UDMH (in particular, in the outer tissue that protects the plant organs from drying out, temperature effects, mechanical damage and other adverse factors) can lead to an imbalance in water metabolism and gas exchange, a deterioration in the absorption and release of water, and the cessation of intake from the soil of both beneficial and harmful substances.

Introduction. Environmental safety is one of the main priorities of state policy. It ensures the legal regulation of relations in space activities to strengthen the defense and security of the Russian Federation and further extension of the international cooperation of the Russian Federation. Material and methods. In the fall areas of the stages of the booster rockets, screening studies were carried out to identify the propellant component 1.1-unsymmetrical dimethylhydrazine in atmospheric air (n=14) and drinking water (n=23), determine its metabolite N-nitrosodimethylamine quantitatively in the residents’ blood (n = 90) living in the surveyed areas before the rocket launch (n = 45) and after the launch (n = 45). Аlso quantitative determination of the N-nitrosodimethylamine metabolite in the residents’ urine in the observation group (n = 108) was performed. For comparison, there was selected a group of residents not related to rocket and space activities (n = 13). Identification and analysis of samples of atmospheric air, drinking water, and biological media (blood, urine) was performed using Agilent 7890A gas chromatograph (USA) with a 5975C quadrupole mass spectrometric detector (MCD) and a capillary column of the HP-FFAP 30m • 0.25mm • 0.25µm series. Results. The study revealed the absence of asymmetric 1.1-dimethylhydrazine in 100% of analyzed atmospheric air samples. During the observation period, the concentrations of N-nitrosodimethylamine in the range of 0.00039 to 0.001 mg/dm 3 were found in drinking water samples that did not exceed the hygienic standard (LOC NDMA 0.01 mg/dm3). N-nitrosodimethylamine in a concentration range of 0.00095-0.346 mg/dm 3 was determined in the blood samples of the population. The studies revealed that after the rocket launch, the N-NDMA concentration in the blood was 1.8 times higher than the concentration registered before the rocket launch. In the urine sample of the resident living in the surveyed area, N-nitrosodimethylamine was detected with a high degree of reliability according to the essential ion with mass 74 m/z and confirmatory ion of 42 m/z, and the concentration was quantitatively calculated at a level of C N-DMA = 0.23 μg/ml. The detection of N-nitrosodimethylamine in blood and urine, even in trace amounts, indicates the possibility of exposure. Conclusion. Performed comprehensive studies made it possible to prove the relative safety of the ecological situation in the fall areas of the booster rockets that are located close to settlements when considering the environmental pollution with unsymmetrical dimethylhydrazine and can be used for systematic monitoring.

Abstract The construction materials that contacted with unsymmetrical dimethylhydrazine and the desorption solutions obtained when treating the contaminated surface of metals and alloys with water and reagents were studied by chromatography and mass spectrometry. Neutralization of unsymmetrical dimethylhydrazine was studied using ozone and shungite. Ozonation makes it possible to destroy the toxicant molecules chemically and physically adsorbed on the surface of metal constructions, due to which they can be reused and utilized. Shungite effectively adsorbs and catalytically decomposes not only unsymmetrical dimethylhydrazine and its transformation products, but also oligomer compounds formed during the storage of hydrazine fuel. Ozonation of spent shungite can increase the efficiency of destructive processes and completeness of its regeneration.

Procedures for qualitative and quantitative analysis of microimpurities of alkylhydrazines and their transformation products in hydrocarbon rocket propellants Naftil, Syntin, and Detsilin by gas and liquid chromatography with on-line and off-line mass-spectrometric detection were developed. Reliable detection of an unsymmetrical dimethylhydrazine impurity in Naftil multicomponent propellant and in its mixtures with other hydrocarbon propellants is possible in the form of thiosemicarbazides by reversed-phase high-performance liquid chromatography and matrix-assisted laser desorption/ionization mass spectrometry.

The N-nitrosodimethylamine (NDMA) formation pathway in chloraminated drinking water remains unresolved. In pH 7-10 waters amended with 10 μM total dimethylamine and 800 μeq Cl2·L-1 dichloramine (NHCl2), NDMA, nitrous oxide (N2O), dissolved oxygen (DO), NHCl2, and monochloramine (NH2Cl) were kinetically quantified. NHCl2, N2O, and DO profiles indicated that reactive nitrogen species (RNS) formed during NHCl2 decomposition, including nitroxyl/nitroxyl anion (HNO/NO-) and peroxynitrous acid/peroxynitrite anion (ONOOH/ONOO-). Experiments with uric acid (a ONOOH/ONOO- scavenger) implicated ONOOH/ONOO- as a central node for NDMA formation, which were further supported by the concomitant N-nitrodimethylamine formation. A kinetic model accurately simulated NHCl2, NH2Cl, NDMA, and DO concentrations and included (1) the unified model of chloramine chemistry revised with HNO as a direct product of NHCl2 hydrolysis; (2) HNO/NO- then reacting with (i) HNO to form N2O, (ii) DO to form ONOOH/ONOO-, or (iii) NHCl2 or NH2Cl to form nitrogen gas; and (3) NDMA formation via ONOOH/ONOO- or their decomposition products reacting with (i) dimethylamine (DMA) and/or (ii) chlorinated unsymmetrical dimethylhydrazine (UDMH-Cl), the product of NHCl2 and DMA. Overall, updated NHCl2 decomposition pathways are proposed, yielding (1) RNS via NHCl2→HNO/NO-→O2ONOOH/ONOO- and (2) NDMA via ONOOH/ONOO-→UDMH-ClorDMANDMA.

As potential hypergolic fuels, hypergolic ionic liquids have attracted much attention since their development. Herein, a series of hypergolic ionic liquids based on asymmetric [bis(imidazolyl)-BH2]+ cations were synthesized. The asymmetric structure of these hypergolic ionic liquids was further confirmed by NMR, infrared (IR), and high-resolution mass spectrometry-electron spray ionization (HRMS-ESI). Moreover, these hypergolic ionic liquids possess a high density of over 1.00 g cm−3, a comprehensive liquid range from −60 °C to 20 °C, and a density-specific impulse performance ranging from 305.4 to 357.8 s g cm−3, which is superior to that of unsymmetrical dimethylhydrazine. Remarkably, (1-allyl-1H-imidazol-3-ium-1-yl)(1-methyl-1H-imidazol-3-ium-1-yl) dihydroboronium dicyandiamide had the best ignition-delay time (18 ms), a high density (1.114 g cm−3), and a high value for heat of formation (400 kJ mol−1/1.48 kJ g−1). This work provides the possibility of a promising and green hypergolic fuel as rocket propellant.

Unsymmetrical dimethylhydrazine (UDMH, heptyl) and its derivatives are used in the rocket and space industry as components of rocket fuel. UDMH is a highly toxic compound exhibiting irritant, hepatotoxic, and neurotoxic properties. In this study, the toxic effect of heptyl on isolated rat heart and lymphatic vessels was demonstrated. Acute exposure to UDMH leads to vasoconstriction of the coronary vessels of the isolated heart and pronounced stimulation of isolated lymphangions starting from the concentration of 10

Unsymmetrical dimethylhydrazine (UDMH) contaminated waste gas and related intermediates pose a great threat to human health. TiO2–reduced graphene oxide aerogel (rGA) samples with different graphene content levels were synthetized and characterized for the degradation of UDMH. The effects of GO content, humidity, and temperature were investigated under UV and VUV light, with highest UDMH conversion values of 68% and 95%, respectively. Compared with pure TiO2, the enhanced degradation activity of TiO2–rGA under UV light can be attributed to a synergetic effect between absorption and photocatalysis, while the high UDMH conversion under VUV light relies on photolysis and ozonation. The high oxygen-containing group content, rather than a high SSA, and electron trapping by graphene are key factors determining the outstanding performance of TiO2–rGA with 80 mg of GO. The prepared TiO2–graphene aerogels are promising for the degradation of gas-phase UDMH.

In this study, α-, β-, and δ-MnO2 were prepared by a uniform hydrothermal method and then coupled with vacuum ultraviolet (VUV) for the degradation of gaseous unsymmetrical dimethylhydrazine (UDMH). The performance in the removal of UDMH, by-product distribution and mechanism were systematically investigated. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption/desorption, Field Emission Scanning Electron Microscopy (FE-SEM), Raman, thermogravimetry (TG), Fourier-transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) to investigate the factors affecting the catalytic activity. The results showed that O2 and H2O were essential for the removal of UDMH. Photooxidation and ozone catalytic oxidation contribute to the removal and mineralization of UDMH. The integrated process considerably improved the removal and mineralization of UDMH by ozone catalytic oxidation. More reactive oxygen species were generated in the integrated process. The catalytic activity of the prepared catalysts follows the order: δ-MnO2 > α-MnO2 > β-MnO2. δ-MnO2 displayed the highest removal rate of 100% and a CO2 concentration of 42 ppmv. The good performance of δ-MnO2 was mainly attributed to the large number of surface oxygen vacancies.

In this work, TiO2/SBA-15 was synthesized via an in situ hydrothermal method and was used for vacuum-ultraviolet (VUV) photocatalytic degradation of unsymmetrical dimethylhydrazine (UDMH) for the first time. Compared with photocatalysis under UV irradiation, VUV photocatalysis exhibited higher photodegradation efficiency due to the synergetic effect of direct photolysis, indirect photooxidation and photocatalytic oxidation. The synthesized TiO2/SBA-15 catalysts exhibited ordered mesoporous structure and anatase phase TiO2. Titanium content, initial pH and substrate concentration impacted degradation efficiency of UDMH in the VUV photocatalysis process. Among the prepared catalysts, TiO2/SBA-15 with the molar ratio of Ti/Si = 1 : 3 (TS-2) showed the best photocatalytic activity under VUV light, with the rate constant of 0.02511 min−1, which is 1.91 times that with VUV/P25. The superior photocatalytic activity of TS-2 is mainly related to the good balance between the specific surface area and TiO2 contents. The photodegradation efficiency decreases with the increase in the initial UDMH concentration and the maximum degradation rate was obtained at pH 9.0. In the VUV/TS-2 process, ˙OH played a more important role in the degradation of UDMH than ˙O2− and the degradation pathways contained bond breaking, amidation, isomerisation and oxidation reactions. The TS-2 also showed good reusability with the rate constant maintained at above 90% after five cycles and exhibited satisfactory degradation efficiency in tap water.

A photochemical method for determination of 1,1-dimethylhydrazine H2NN(CH3)2 (unsymmetrical dimethylhydrazine (UDMH)) based on titration of the analyte with photogenerated iodine obtained by irradiation of an auxiliary solution containing potassium iodide and a mixture of sensitizers (EOSIN Y:auramine:fluorescein taken in a molar ratio 1:1:1) in an acetate medium (pH 6) has been developed. With increasing acidity, a decrease in the rate of photogeneration is observed which is most likely attributed to disproportionation of the resultant titrant. Since the titrant (iodine) content is controlled by the voltammetric method, the photochemical titration of UDMH is accompanied by a decrease in the current strength in the circuit of the amperometric setup and stabilization indicates the completeness of the reaction. Measurements of the photogeneration time necessary to compensate for the loss of titrant in the cell upon further irradiation of the solution in the presence of atmospheric oxygen provide quantitative assessing of the UDMH content in environmental objects. Since the analyte interacts with the titrant in a molar ratio 1:2, we suggest the possibility of UDMH oxidation to NDMA (N-nitrosodimethylamine). A photochemical method of UDMH determination in solution is thus developed with the detection and determination limits (0.49 and 1.62) μg/ml, respectively. Unfortunately, the sensitivity of the proposed methodology does not allow determination of a toxic chemical contaminant at the MPC level which necessitates preconcentration of the mobile forms of UDMH by steam distillation in a 40 % sodium hydroxide solution. The developed methodology matches the validation parameters by the indices of linearity, ranking, correctness and thus can be recommended for determination of the UDMH content in any analytical laboratory. The photochemical method was tested in the analysis of soil samples taken from background and contaminated territories as well as natural water. A slight excess of the UDMH content has been found in the soil taken from the former location of the military unit.

Unsymmetrical dimethylhydrazine (UDMH) is a widely used rocket propellant. Entering the environment or being stored in uncontrolled conditions, UDMH easily forms an enormous variety (at least many dozens) of transformation products. Environmental pollution by UDMH and its transformation products is a major problem in many countries and across the Arctic region. Unfortunately, previous works often use only electron ionization mass spectrometry with a library search, or they consider only the molecular formula to propose the structures of new products. This is quite an unreliable approach. It was demonstrated that a newly proposed artificial intelligence-based workflow allows for the proposal of structures of UDMH transformation products with a greater degree of certainty. The presented free and open-source software with a convenient graphical user interface facilitates the non-target analysis of industrial samples. It has bundled machine learning models for the prediction of retention indices and mass spectra. A critical analysis of whether a combination of several methods of chromatography and mass spectrometry allows us to elucidate the structure of an unknown UDMH transformation product was provided. It was demonstrated that the use of gas chromatographic retention indices for two stationary phases (polar and non-polar) allows for the rejection of false candidates in many cases when only one retention index is not enough. The structures of five previously unknown UDMH transformation products were proposed, and four previously proposed structures were refined.

Quantification of unsymmetrical dimethylhydrazine transformation products in ambient air is important for assessing the environmental impact of heavy rocket launches. There are very little data of such analyses, which is mainly caused by the low number of analytes covered by the available analytical methods and their complexity. A simple and cost-efficient method for accurate simultaneous determination of seven unsymmetrical dimethylhydrazine transformation products in air using solid-phase microextraction followed by gas chromatography-mass spectrometry was developed. The method was optimized for air sampling and solid-phase microextraction from 20-mL vials, which allows full automation of analysis. The extraction for 5 min by Carboxen/polydimethylsiloxane fiber from amber vials and desorption for 3 min provided the greatest analytes' responses, lowest relative standard deviations, linear calibration (R2 ≥ 0.99), and limits of detection from 0.12 to 0.5 μg/m3 . Samples with concentrations 500 μg/m3 can be stored at 21 ± 1°C without substantial losses (1-11%) for up to 24 h, while air samples with concentrations 10 and 50 μg/m3 stored for up to 24 h can be used for accurate quantification of only two and four out of seven analytes, respectively. The developed method was successfully tested for the analysis of air above real soil samples contaminated with unsymmetrical dimethylhydrazine rocket fuel.

The surface of graphene oxide (GO) with different oxidation levels is widely used in gas sensing applications. 1,1-Dimethylhydrazine (unsymmetrical dimethylhydrazine, UDMH) as a highly toxic and volatile pollution gas has long been investigated and discussed. The research reported here examined the stable structure of GO surface by first principles calculation. Furthermore, the adsorption mechanism of UDMH on the stable GO surface was explored and the optimal adsorption distance and upper limit of adsorption quantity were determined with their adsorption energy calculated. The results reveal that the hydroxyl group on GO did a great service to the UDMH adsorption and the UDMH tends to approach GO from the direction of -NH2, with distance being 2.9 A.

Unsymmetrical dimethylhydrazine (UDMH) is a liquid propellant widely used in aviation and aerospace. It produces a large amount of dimethyl hydrazine wastewater during long-term storage, testing, and reinjection. Traditional treatments produce numerous secondary contaminants such as residual high carcinogens, including N-nitrosodimethylamine (NDMA) and formaldehyde dimethylhydrazone (FDMH). In this paper, the dielectric barrier discharge (DBD) low temperature plasma technology is used to degrade the dimethyl hydrazine wastewater. Aiming at the problem of secondary pollutants in the degradation process, we used qualitative and quantitative methods to study the changes of NDMA and FDMH during the degradation of dimethyl hydrazine wastewater by DBD low temperature plasma. The kinetics of these two products showed that the degradation process of NDMA was consistent with the first-order reaction kinetics. Using density functional theory, we established molecular models of UDMH, NDMA and FDMH. According to the molecular orbital theory, the formation mechanism of NDMA and FDMH was calculated from three aspects: reaction structure, reaction path and energy change. We found that during the degradation of dimethyl hydrazine, the dimethyl hydrazine oxidation product was initiated by hydrogen abstraction on methyl (-CH3) and amine (-NH2). NDMA is produced by the oxidation of -NH2, whereas FDMH is mainly produced from dimethyl hydrazine and formaldehyde.

N,N-Dimethylhydrazine ((CH3)2–N–N–) compounds in water produce toxic N-nitrosodimethylamine (NDMA) during ozonation, thus need removing from water before ozonation. Chlorination can degrade N,N-dimethylhydrazines to give products that do not form NDMA during ozonation, but the chemistry is poorly understood. We studied the kinetics of and mechanisms involved in reactions between free available chlorine (FAC) and unsymmetrical dimethylhydrazine (UDMH) and daminozide (DMZ) (N,N-dimethylhydrazine compounds) and the efficiency with which FAC decreased the ozone–NDMA-formation potentials of UDMH and DMZ. FAC reacted quickly with UDMH (k = 4 × 105 M−1 s−1) and moderately with DMZ (k = 66 M−1 s−1) at pH 7. Formaldehyde and methanol were the main UDMH and DMZ degradation products, and succinic acid was also an important DMZ degradation product. Negligible NDMA formed (

—The behavior of unsymmetrical dimethylhydrazine (UDMH), a highly toxic rocket fuel, has been studied in a supercritical water medium within a temperature range of 400–650°C by electrospray ionization high-resolution mass spectrometry. It has been established that thermal transformation leads to the formation of a wide range of products, including at least 350–400 nitrogen-containing compounds of CHN and CHNO-classes. The main products are nitrogen-containing heterocyclic compounds containing from one to three nitrogen atoms. Based on the accurate masses, the tentative identification of the most important components is given. It has been shown that 1-methyl-1H-1,2,4-triazole predominates among the transformation products at a temperature of 650°C; in this case, the predominant fraction of UDMH is converted into gaseous nitrogen.

Current methods for measurement of unsymmetrical dimethylhydrazine (UDMH) in wastewater suffer from a small detection range and complex pretreatment. In this study, ion chromatography (IC) with conductivity detection was used to directly analyze UDMH in wastewater, without any derivatization pretreatment, and the measurement range was as wide as 0.5–1000 μg·mL−1. The effects of column temperature and sample pH on the detection were investigated. Furthermore, the chromatography conditions were optimized by combining the effects of different combinations of nitric acid, 2,6-pyridinedicarboxylic acid (PDCA), and methanesulfonic acid (MSA) on the analysis of mixed samples of UDMH and alkali metal ions. The linearity of the detected peak height (H) and peak area (A) versus UDMH concentration was studied at low, medium, and high concentrations. A good linear relationship was observed in the range of 0.5–1000 μg·mL−1, especially for A, the relative standard deviation (RSD) and correlation coefficient (R2) of which were 0.077–1.653% and 0.9998–1.0000, respectively. In addition, the method showed good sensitivity with a limit of detection (LOD) of 0.05 μg·mL−1 and a limit of quantitation (LOQ) of 0.16 μg mL−1. The precision and accuracy (expressed by recovery) were verified, where the RSD were less than 1.49% and 3.17%. Interference between hydrazines and alkali metal ions was discussed. Finally, actual UDMH samples were determined, confirming the applicability of the developed method for analyzing UDMH in wastewater during the degradation process.

In this paper, the catalytic wet peroxide oxidation (CWPO) combined with vacuum ultraviolet (VUV) irradiation was developed to mineralize the wastewater with high concentration of unsymmetrical dimethylhydrazine (UDMH), especially to decompose the main byproduct of UDMH decomposition, N-nitrosodimethylamine (NDMA). CuO-NiO-MgO/γ-Al2O3 was used as the catalyst and H2O2 as the resources of ⋅ O H . Fourier Transform Infrared spectroscopy (FT-IR), X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray spectroscopy (EDX) were employed to evaluate the structure of the catalyst. The treatment performances such as the UDMH degradation efficiency, chemical oxygen demand (COD) removal efficiency, and the concentration of N-nitrosodimethylamine (NDMA) were investigated in the treating process. The optimal conditions were obtained based on the results of single-factor experiments including parameters such as the initial UDMH concentration, catalyst dosage, initial pH, H2O2 dosage and temperature. The comprehensive results indicated that CWPO/H2O2/VUV process presented remarkable treatment performance to the reaction conditions with about 100% UDMH conversion efficiency, 95.02% COD removal efficiency and approximately 100% UDMH removal within 30 min.

Unsymmetrical dimethylhydrazine (UDMH) is a rocket propellant for carrier rockets and missiles. UDMH is environmentally hostile compound, which easily forms a variety of toxic products of oxidative transformation. The liquidation of unused UDMH from retired launch sites is performed by the complete burning of UDMH-containing wastes. Due cyclicity of the burning equipment the UDMH-containing wastes are subject of prolonged storage in contact with atmospheric oxygen and thus contains a complicated mixture of UDMH degradation products. High performance liquid chromatography (HPLC), high resolution mass spectrometry (HRMS) and NMR were used for the isolation on characterization of new highly polar and potentially toxic UDMH transformation products in the mixture. Two series of unreported isomers with high ionization cross section in electrospray ionization were isolated by repeated preparative HPLC. The structures of the isomers were established by tandem HRMS and NMR. The cytotoxicity of the isolated compounds has been preliminarily studied and found to be similar to UDMH or higher.

Quantification of unsymmetrical dimethylhydrazine (UDMH) transformation products (TPs) in solid samples is an important stage in monitoring of environmental pollution caused by heavy rockets launches. The new method for simultaneous quantification of UDMH TPs in sand samples using vacuum-assisted headspace solid-phase microextraction (Vac-HSSPME) followed by gas chromatography-mass spectrometry (GC-MS) is proposed. Compared to regular HSSPME, Vac-HSSPME yielded 1.3–4.8 times higher responses for NDMA, MTA and PAl. Increasing air-evacuation time from 20 to 120 s at 23 ºC resulted in decreased responses of analytes by 25–46%. Freezing of samples (-30 ºC) had negligible effect on responses of analytes at air-evacuation time 20 s. The best combination of responses of analytes and their RSDs was achieved after air-evacuation of a sample (m = 1.00 g) for 20 s at 23 ºC, incubation for 30 min and 30-min extraction at 40°C by Car/PDMS fiber. Vac-HSSPME provided linear calibration plots in studied ranges of concentrations with coefficients of determination ranging from 0.9912 to 0.9938. The limits of detection for spiked sand samples varied from 0.035 to 3.6 ng g− 1. Spike recoveries of target analytes from sand samples were 84–97% with RSDs 1–11%. The developed method was successfully tested in the experiment on studying losses of analytes from open vials with model sand spiked with UDMH TPs. The developed method can be recommended for analysis of trace concentrations of UDMH TPs when studying their transformation, migration and distribution in contaminated sand.

N-nitrosodimethylamine (NDMA), a nitrosamine, is a typical nitrogenous disinfection byproduct. In this study, NDMA formation potential and mechanism, from tetracycline and oxytetracycline (as model precursors) in an ammonium-contaminating water, were investigated. The results indicated that both monochloramine and dichloramine played a vital role in NDMA formation. Additionally, the determination of NDMA formation potential (NDMA FP) at a wide range of pH showed that the unprotonated tetracycline tended to have a higher NDMA conversion ratio. We also found that the dissociation of hydroxyl on the meta-position of dimethylamine group promoted on NDMA formation. The detection of significant intermediate products showed that N-chloro unsymmetrical dimethylhydrazine (UDMH-Cl) and sequences of chlorine substitution products were key intermediates, indicating that NDMA formation occurred via the UDMH mechanism pathway. These results improve the knowledge on NDMA formation mechanism and the control strategies during the disinfection of ammonium-containing water.

The gas-phase structures of protonated unsymmetrical 1,1-dimethylhydrazine (UDMH) and the proton-bound dimers of UDMH and hydrazine are examined by infrared multiple photon dissociation (IRMPD) action spectroscopy utilizing light generated by a free electron laser and an optical parametric oscillator laser system. To identify the structures present in the experimental studies, the measured IRMPD spectra are compared to spectra calculated at the B3LYP-GD3BJ/6-311+G(d,p) level of theory. These comparisons show that protonated UDMH binds the proton at the methylated nitrogen atom (α) with two low-lying α conformers probably being populated. For (UDMH)2H+, the proton is shared between the methylated nitrogen atoms with several low-lying α conformers likely to be populated. Higher-lying conformers of (UDMH)2H+ in which the proton is shared between α and β (unmethylated) nitrogen atoms cannot be ruled out on the basis of the IRPMD spectrum. For (N2H4)2H+, there are four low-lying conformers that all reproduce the IRMPD spectrum reasonably well. As hydrazine and UDMH see usage as fuels for rocket engines, such spectra are potentially useful as a means of remotely monitoring rocket launches, especially in cases of unsuccessful launches where environmental hazards need to be assessed.

Four phenylurea herbicides (PUHs) were assessed for degradation and transformation into N-nitrosodimethylamine (NDMA) under three oxidation conditions (chlorine (Cl2), chlorine dioxide (ClO2), and ozone (O3)) from an aqueous solution. Removal ratios correlated with the numbers of halogen elements contained in PUHs (isoproturon (0) > chlorotoluron (1 Cl) > diuron (2 Cl) > fluometuron (3 F)), and the degradation efficiencies of oxidants from fastest to slowest were: O3, ClO2, and Cl2. NDMA can be generated directly from the ozonation of PUHs. Further, compared with chloramination alone, ozonation prominently promoted NDMA formation potential (NDMA-FP) during post-chloramination, and NDMA-FPs increased approximately 23–68 times than those during ozonation only at 2.5 mg/L O3 over 10 min; molar yields of NDMA from highest to lowest were 11.1% (isoproturon), 1.17% (chlorotoluron), 1.0% (diuron), and 0.73% (fluometuron). The PUH degradation kinetics data during ozonation agreed with the pseudo-first-order model. The rate constant kobs were 0.31 × 10−3–19.8 × 10−3 s−1. The kobs and removal ratios of PUHs during ozonation partially scaled with the mass, LogKow, and Henry’s constants of PUHs. Comparisons of measured NDMA-FPs with calculated NDMA-FPs from residual PUH after oxidation showed that the intermediates produced during ozonation facilitated NDMA-FPs; this contribution was also observed for chlorotoluron and isoproturon during ClO2 oxidation. Examination of reaction mechanisms revealed that tertiary amine ozonation, N-dealkylation, hydroxylation, the cleavage of N–C bonds, ammonification, and nitrification occurred during the ozonation of PUHs, and the dimethylamine (DMA) functional groups could be decomposed directly and transformed into NDMA via the formation of the intermediate unsymmetrical dimethylhydrazine. NDMA is also formed from the reaction between DMA and phenylamino-compounds. Clarifying primary degradation products of PUHs and transformation pathways of NDMA during oxidation processes is useful to optimize treatment processes for water supplies.

In this paper, we briefly described the ecological consequences of six space rocket accidents launched from the Baikonur Cosmodrome between 1999 and 2018 and focused on an assessment of efficiency of soil remediation following the accidental crash of launch vehicle Proton-M on July 2, 2013, which resulted in the severest environmental impact in the modern Russian space industry. On the day after the accident, the content of carcinogenic unsymmetrical dimethylhydrazine and nitrosodimethylamine, as well as nitrate in soils of the crash site exceeded their maximal permissible concentrations by 8900, 6100 and 85 times, respectively. Mitigation measures included soil detoxication by a solution of 10% H2O2 and 1% iron complexonate, soil excavation and ploughing. Two years later (in April 2015), both unsymmetrical dimethylhydrazine and nitrosodimethylamine concentrations were below 0.05 mg/kg and nitrate concentration did not exceed 3.9 g/kg. As compared to background sites, soils of the crash site had significantly (P-value

The article presents the results of ecological modeling of soil and plant pollution processes by toxic heptyl rocket fuel (unsymmetrical dimethylhydrazine, UDMH) and the product of its transformation by N-nitrosodymethylamine (NDMA). Experiments delivered in laboratory conditions show that in sabulous gray-brown soil (uncontaminated soil samples were taken from the Baikonur Cosmodrome zone), the reaction of transformation of UDMH in NDMA is reversible and depends on the concentrations of reacting compounds. NDMA is transferred from the soil to the stems and leaves of plants of wild-growing species by the aerogenous route. The ability to accumulate NDMA by leaves and stems of plants is more or less dependent on the plant species. Objective - research on the transformation of unsymmetrical dimethylhydrazine (UDMH) and N - nitrozodymethylamine (NDMA) in a closed reservoir - an ecological model of rocket fuel pollution. Research methods. The method of ecological modeling studies of UDMH and NDMA contamination in soil and plants has been developed and tested. Boxes with samples of sabulous gray-brown soil and seeds of wild plants brought from the drop zones of detachable parts of launch vehicles have been placed in hermetically sealed and transparent containers. NDMG or NDMA are introduced into the soil. To measure the content of UDMH and NDMA in soil samples, in condensate on container walls, in the above-ground part and roots of plants, as well as in water washes from leaves, the method of quantitative chemical analysis high performance liquid chromatography has been used.

N-nitrosodimethylamine (NDMA), a toxic disinfection byproduct commonly associated with chloramination, has recently been found to form from an anti-yellowing agent (4,4'-hexamethylenebis (1,1-dimethylsemicarbazide) (HDMS)) during ozonation but the mechanisms are unclear. In this paper, the potential roles of molecular ozone (O3) and hydroxyl radical (∙OH) on NDMA formation from HDMS were investigated under various oxidation conditions (ozone dosages, pH) and different components in water (bromide ion (Br-), bicarbonate ion (HCO3-), sulfate ion (SO42-), and humic acid (HA), as well as natural organic matter (NOM) from a lake). Moreover, HDMS transformation pathways by ozonation were determined. The results indicated that the formation of NDMA was enhanced through the combined effect of O3 and ∙OH compared to that by O3 alone (addition of tert-butyl alcohol (tBA) as ∙OH scavenger). ∙OH itself cannot generate NDMA directly; however, it can transform HDMS to intermediates with higher NDMA yield than parent compound. The NDMA generation was affected (small dosages promoted but high dosages inhibited) by HA or Br- no matter with or without tBA. The presence of SO42- and HCO3- ions lowered NDMA formation through ∙OH scavenging effect. Increasing pH not only increased degradation rate constant by enhancing ∙OH generation but also affected HDMS dissociation ratio, reaching the maximum NDMA formation at pH 7-8. Natural constituents in selected water matrix inhibited NDMA formation. Impacts of these influencing factors on NDMA formation by only O3 however were significantly less pronounced over that by the joint roles of O3 and ∙OH. Based on the result of Q-TOF, LC/MS/MS, and GC/MS, the possible transformation pathways of HDMS by ozonation were proposed. The NDMA enhancement mechanism by the combined effect of O3 and ∙OH can be attributed to greater amounts of intermediates with higher NDMA yield (such as unsymmetrical dimethylhydrazine (UDMH)) produced. These findings provide new understanding of NDMA formation upon ozonation of typical amine-based compounds.

Quantification of transformation products of unsymmetrical dimethylhydrazine (UDMH) in soil requires tedious, time- and labor-consuming sample preparation. The simple and fast method for quantification of transformation products of UDMH in aqueous extracts from soil using vacuum-assisted headspace solid-phase microextraction (Vac-HSSPME) was optimized in this work. The method is based on extraction of analytes from soil with water followed by Vac-HSSPME of the obtained aqueous extracts, and gas chromatography-mass spectrometry analysis. The target transformation products were: pyrazine, 1-methyl-1H-pyrazole, N-nitrosodimethylamine, N,N-dimethylformamide, 1-methyl-1Н-1,2,4-triazole, 1-methyl-imidazole and 1H-pyrazole. The effect of a sample pH on responses of target analytes was studied. It was negligible, and no pH adjustment was recommended before a subsequent extraction. The water amount was optimized to provide the best combination of analytes responses and their precision. Extraction by adding 7.00 mL of water to 2.0 g of soil ensured linear dependence of responses of the analytes on their concentrations in soil. The optimized method provided detection limits of target analytes in soil in the range from 0.2 to 9 ng/g. The spike recoveries obtained for model samples were in the range 90-103%. The developed method can be recommended for application in laboratories conducting routine analyses of soil samples potentially contaminated by rocket fuel residuals.

Unsymmetrical dimethylhydrazine (UDMH) is a high N-containing (as much as nearly 50%) substance. Traditional treatment methods such as incineration will inevitably cause the formation of nitric oxide and secondary pollution. Supercritical water is a preferred transformation medium due to its unique physicochemical properties. However, at present most of studies are limited to supercritical water oxidation (SCWO) which tends to produce hydrogen nitrate resulting in corrosion to the reactor. To conquer this problem, we propose supercritical water gasification (SCWG) technology which is in a reducing environment, realizing both harmless treatment and resource utilization. In order to promote its industrialization process, the reaction pathways and kinetic parameters should be studied. In this paper, the reaction pathways and kinetics of UDMH in supercritical water were conducted under the conditions of 400 °C–550 °C in quartz reactor, which avoids the catalytic effect on the reaction kinetics. From the resource utilization perspective, the most abundant quantitatively detectable gaseous product is methane, together with less hydrogen, carbon monoxide and ethane orderly. All these gaseous products are combustible. The maximum of carbon efficiency is 90.25% at 550 °C, 10 min. In the point of view of harmless treatment, the organic compounds contained in the residual liquid are detected with 1H NMR, FTIR and GC/MS. Results show that UDMH could be fully degraded within 3 min and the ultimate organic compounds in the residual liquid are mainly dimethylamino acetonitrile and trimethylamine. In addition, a reaction pathway for UDMH disposed in supercritical water is developed. Finally, the quantitative kinetic model for describing the gaseous products and ammonia-nitrogen in the residual liquid is brought forward. The pyrolysis activation energy for UDMH in supercritical water is 49.98 ± 7.38 kJ/mol.

1,1-Dimethylhydrazine is widely used as a fuel by some classes of carrier rockets. Being an extremely toxic and reactive substance, it gives a number of hazardous transformation products and poses a serious threat to the ecological state of the launch sites and territories used for landing of spent rocket parts. On the basis of studies of the retention of analytes on the sulfobetaine zwitterionic stationary phase, the HILIC–ESI-MS/MS method for simultaneous and rapid determination of unsymmetrical dimethylhydrazine and six major products of its transformation (methylhydrazine, N-nitrosodimethylamine, N,N-dimethylformamide, 1-methyl-1,2,4-1H-triazole, 1,1,4,4-tetramethyl-2-tetrazene, 1,1-dimethylguanidine) was developed. The achieved detection limits for the analytes were 0.02–7 μg L−1 and, for most compounds, they are significantly lower compared to the existing IC–MS/MS method. Direct combination of HILIC–MS/MS with preliminary pressurized extraction with acetonitrile allowed analysis of peat bog soils contaminated with rocket fuel within 40 min, including all sample preparation steps. The developed method was successfully tested on a sample of real soil from the falling place of the spent carrier rocket stage.

Effectiveness of pyridoxine hydrochloride and inosine glycyl-cysteinyl-glutamate dinatrium (molixan) in monotherapy and in combination in acute poisoning by unsymmetrical dimethylhydrazine on survival, blood biochemical indicators and the state of plasma coagulation hemostasis was assessed. Unsymmetrical dimethylhydrazine was administered intraperitoneally at a dose of 115 mg/kg (LD50) once. Drugs under examination were also admistered intraperitoneally: pyridoxine hydrochloride in a dose of 50 mg/kg once, 30 minutes after the administration of unsymmetrical dimethylhydrazine, the inosine glycyl-cysteinyl-glutamatedinatrium (molixan) in a dose of 60 mg/kg seven times: 30 minutes after the administration of unsymmetrical dimethylhydrazine, and then daily for 6 days. Biochemical parameters of blood, plasma coagulation hemostasis, were evaluated 7 days after the administration of unsymmetrical dimethylhydrazine. The use of pyridoxine as a monotherapy and in combination with molixan prevents death of experimental animals and the development of convulsive syndrome. In addition, the combination of molixan with pyridoxine eliminates the development of toxic lesions of liver that is having hepatoprotective effect. The efficiency of molixan as hepatoprotector, apparently, related to the fact that in its structure it is a combined preparation containing the peptide and purine components. The peptide component (glycyl-cysteinyl-glutamate dinatrium) is a pharmacological analogue of oxidized glutathione, purine is represented by inosine. Oxidized glutathione has cytoprotective activity, inhibits the cytolysis of hepatocytes, and reduces the severity of inflammatory process during toxic damage of liver cells by the products of metabolism of xenobiotics. Inosine also has hepatoprotective properties. As a precursor to the synthesis of adenosine triphosphoric acid and nucleotides, it stimulates a number of metabolic processes in body, supports energy balance in various tissues, particularly in liver and myocardium.

Carcinogenic N, N-Dimethylnitrosamine (NDMA) has been reported to generate significantly during ozonation of fuel additive unsymmetrical dimethylhydrazine (UDMH), the combined ozone/Peroxy-Monosulfate (O3/PMS) technology was tried for reducing its formation in this study. The influence of PMS dosages, ozone concentrations, pH, Br- and humic acid (HA) on NDMA formation from UDMH were investigated. In addition, the reduction mechanisms were explored by intermediates identification and Gaussian calculation. The results demonstrated that O3/PMS technology was effective on NDMA reduction, reaching an efficiency of 81% with 80 μM PMS. Higher NDMA reduction rates were achieved by O3/PMS with increasing pH within the scope of research (from 5 to 9), achieving a maximum of 69.9% at pH 9. The presence of bromide ion facilitated NDMA generation during ozonation, but the reduction efficiency by O3/PMS slightly improved from 66.3% to 70.6%. The presence of HA reduced NDMA formation in O3/PMS system. The contribution of SO4•− on NDMA reduction accounted for ~64%, which was higher than that of •OH (41.4%); however, its promotion role on conversing UDMH to NDMA was lower than O3. Therefore, the technology could reduce NDMA formation effectively. In addition, the results of Gaussian calculation manifested that the N atom in -NH2 group of UDMH was easily attacked not only by •OH but also by O3, so it is the key path that determines final NDMA formation. This study would provide reference for reducing NDMA formation during ozonation of UDMH-containing water matrixes.

Existing and newly developed technologies for clean-up of wastewaters and soils contaminated with rocket fuel unsymmetrical dimethylhydrazine (UDMH) are based on the oxidative treatment, as well as gasification in supercritical water. Being easily transformed by a radical mechanism, UDMH is capable of producing an extremely wide range of potentially hazardous nitrogen-containing products. Their identification and simultaneous quantification at low concentrations in water samples by gas chromatography is a challenging task requiring a matrix change. We proposed a combination of dispersive vortex-assisted liquid-liquid microextraction (VALLME) of analytes followed by gas chromatography – Orbitrap mass spectrometry allowing simultaneous target analysis and non-targeted screening. Dichloromethane and chloroform provided rapid (10 min) and effective extraction of most of UDMH transformation products. The maximum recoveries were achieved by alkalizing and saturating the aqueous samples with ammonium sulfate. The use of pyridine‑d5 as an internal standard allowed developing an approach to the simultaneous determination of 24 compounds of various classes with detection limits for the most analytes in the range 0.02–1.1 μg L−1 and accuracy of 81–117% with low-cost, simple, and rapid sample preparation procedure. Extraction with a 100 µL of chloroform allowed further increasing sensitivity up to one order of magnitude and attaining LOD values for 20 compounds in the range of 0.002–0.1 μg L−1 comparable with that obtained by vacuum-assisted headspace solid-phase microextraction. The developed method was validated and tested for the analyses of real samples – degraded aqueous solution of rocket fuel, products of UDMH treatment in supercritical water and aqueous extract of soil from the place of carrier rocket accidental crash. Twenty-nine compounds that were not previously described as UDMH transformation products were tentatively identified.

The hypergolic ignition behaviors of four newly synthesized ionic liquids with dicyanamide anion (ionic liquids 1 and 3) and cyanoborohydride anion (ionic liquids 2 and 4) were experimentally inves...

In this work, simple, rapid and highly sensitive method of hazardous chemical 1,1-dimethylhydrazine (unsymmetrical dimethylhydrazine, UDMH) determination based on pre-column derivatization with unsubstituted aromatic aldehydes and reversed-phase high performance liquid chromatography-ultraviolet-tandem mass spectrometry (RP HPLC-UV-MS/MS) has been developed. Along with benzaldehyde, commercially available aromatic aldehydes, namely: 2-naphthaldehyde, 2-pyridinecarboxaldehyde, and 2-quinolinecarboxaldehyde, were used as derivatizing reagents in the analysis of hydrazines for the first time. The reactions were studied in a wide pH range by varying reaction time and other conditions. A slightly alkaline pH 9 was shown to be optimal for the derivatization of UDMH by aromatic aldehydes. The quantitative yield of derivatization products under the established conditions was confirmed by HPLC analysis with amperometric detection. For all studied reagents, wide linear ranges of concentrations (0.01–1000 μg/L) in natural water samples were observed. The limits of detection for UDMH in natural water were in the 3.7–130 ng/L range. 2-Quinolinecarboxaldehyde was selected as the most appropriate reagent for HPLC-UV-MS/MS determination of UDMH. In case of using this reagent, the accuracy was in the range of 97–102%, and precision, expressed as RSD was less than 8%. The developed approach does not require laborious stages of pre-concentration and isolation of UDMH from natural water components.

Supercritical water gasification technology has been proved to be an alternative to realize both resource utilization and harmless treatment. However, atomistic simulation should be investigated as a supplement to our previous experiment to fully understand the gasification mechanism process of unsymmetrical dimethylhydrazine (UDMH) in supercritical water. The degradation mechanism was studied with molecular dynamic using the DFT and ReaxFF combination method. Simulation under different temperatures was systematically discussed to investigate the product distribution. It was found that hydrogen yield dominates and the amount of methane and ammonia tend to decrease at high temperature. The degradation mechanism was also developed. There are two ways of UDMH’s degradation: the bond breaking of carbon–nitrogen or nitrogen-nitrogen bond. High temperature favors the former while low temperature favors the latter. We also analyzed the source of product species and found that abundant free radicals resulted from high temperature is the main reason for the dominant hydrogen yield. The yield of methane is resulted from two competing mechanisms, whereas element nitrogen in unsymmetrical dimethylhydrazine is transformed to nitrogen and ammonia.

Graphene and its derivatives are widely used in the adsorption of various pollutants. The present study investigated the absorption of UDMH (Unsymmetrical Dimethylhydrazine) on intrinsic graphene or graphene oxides (GO) based on the first-principles calculations. The optimal molecular orientation of UDMH, when absorbed by GO, was determined, and the adsorption energies (Ea) and charge transfer of UDMH were revealed as well. The calculation results indicate that the UDMH adsorption effect seems to be independent of the adsorption site of graphene. Moreover, the enhancement of hydroxyl groups on graphene is greater than that of the epoxy groups. And if hydroxyl and epoxy groups are both on the graphene surface, the adsorption of UDMH is more favorable when they are located on the same side.

Supercritical water gasification technology has ability to process unsymmetrical dimethylhydrazine (UDMH) wastewater derived from launching spacecraft, missile or satellite realizing both harmless treatment and resource utilization due to its unique property. Owning advantages such as compact structure, highly reduced reactor volume, improved heat transfer efficiency and fully mixed reactants, a spiral continuous reactor was proposed based on the characteristics of UDMH wastewater. Methylhydrazine (MMH) was used as model compound on account of UDMH’s commercial unavailability. The degradation of MMH in supercritical water is determined as an apparent first-order reaction using initial rate method. The effect of different parameters including temperature (450–550 °C), feeding flow rate (10–75 g/min), feeding concentration (5–30 %), and catalyst type on gasification were systematically investigated and subsequently the migration of carbon and nitrogen was also concerned. Results showed that addition of KOH could make the carbon gasification efficiency approach 100 % with the maximum hydrogen yield up to 21.6 mol/kg under the condition of 500 °C, 23 MPa, feeding flow rate of 30 g/min, feedstock concentration of 10 %. The proportion of organic carbon in total carbon tended to decrease with the increase of temperature. Most of nitrogen (up to 99.7 % at most) was gasified within our experimental range.

Titanium dioxide (TiO 2 ) has been widely investigated as a photocatalytic material. However, the photocatalytic activity of TiO 2 is suppressed by the large band gap and the recombination rate of the electron-hole pairs. Here, we propose an in situ synthetic strategy for the construct of carbon doped TiO 2 (carbon-TiO 2 ) nanotubes using surface-sulfonated layer of polystyrene fibers/titania composites as the precursors of TiO 2 and carbon source via a facile route of calcination. This technique involves the preparation of morphology well controlled polystyrene fibers, sulfonation of PS fibers, sol-gel synthetic process of TiO 2 and the pyrolysis of SSPS fibers in a N 2 atmosphere at 450 °C. The morphology and structure of as-prepared carbon-TiO 2 nanotubes are mainly characterized by SEM, TEM, XRD, Raman spectroscopy, XPS and UV–vis spectroscopy. All results confirm the carbon doping in the as-prepared carbon-TiO 2 nanotubes. As a result of the unique microstructure, this composite exhibits remarkable photocatalytic efficiency for the degradation of unsymmetrical dimethylhydrazine under visible light irradiation, indicating great potential for dealing with waste water containing organic pollutant.

The present paper describes the phenomenon of hard start observed from a demonstrator of 500 N scale nontoxic hypergolic thruster using high-test peroxide as an oxidizer. When 90% concentration of hydrogen peroxide was used, the hard start was observed even under the fuel lead operation. To effectively suppress the occurrence of hard start phenomena in the startup phase of the thruster, oxidizer-to-fuel mass ratio and concentration of hydrogen peroxide have been individually considered. In drop tests, the ignition delays of hypergolic reactions became longer in the oxidizer-rich condition than those measured in the fuel-rich condition. By regulating oxidizer-to-fuel mass ratio with deliberate control of the oxidizer mass flow rate, the thruster operated smoothly even using 90% high-test peroxide in the fuel-rich environment. Furthermore, without the utilization of the flow control device, the thruster successfully operated when higher concentrations of high-test peroxide (95 and 98%) were used under the f...

Quantification of trace concentrations of transformation products of rocket fuel unsymmetrical dimethylhydrazine (UDMH) in water requires complex analytical instrumentation and tedious sample preparation. The goal of this research was to develop a simple and automated method for sensitive quantification of UDMH transformation products in water using headspace (HS) solid-phase microextraction (SPME) in combination with GC-MS and GC-MS/MS. HS SPME is based on extraction of analytes from a gas phase above samples by a micro polymer coating followed by a thermal desorption of analytes in a GC inlet. Extraction by 85 µm Carboxen/polydimethylsiloxane fiber at 50 °C during 60 min provides the best combination of sensitivity and precision. Tandem mass spectrometric detection with positive chemical ionization improves method accuracy and selectivity. Detection limits of twelve analytes by GC-MS/MS with chemical ionization are about 10 ng L−1. GC-MS provides similar detection limits for five studied analytes; however, the list of analytes detected by this method can be further expanded. Accuracies determined by GC-MS were in the range of 75–125% for six analytes. Compared to other available methods based on non-SPME sample preparation approaches (e.g., liquid–liquid and solid-phase extraction), the developed method is simpler, automated and provides lower detection limits. It covers more UDMH transformation products than available SPME-based methods. The list of analytes could be further expanded if new standards become available. The developed method is recommended for assessing water quality in the territories affected by space activities and other related studies.

SO42-/TiO2, SO42-/Fe2O3 nanoparticles were prepared by the impregnation precipitation method. The X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy disperse spectroscopy (EDS) results showed that the uniform size of SO42-/TiO2, SO42-/Fe2O3 nanoparticles with high purity, good dispersivity and particle size range from 50nm to 200nm. A comparative study between SO42-/TiO2 and SO42-/Fe2O3 nanoparticles applied in the photocatalytic experiment on unsymmetrical dimethylhydrazine (UDMH) wastewater was carried out.

In this paper, we assessed snow pollution by nitrogen-containing substances including rocket propellants – UDMH (unsymmetrical dimethylhydrazine, (СН3)2NNH2) and NT (nitrogen tetroxide, N2O4) – and their transformation products (NDMA (nitrosodimethylamine, (CH3)2NNO), NO3−, NO2− and NH4+) within the falling regions (FRs) of the first and second stages of Proton-M rockets launched from the Baikonur Cosmodrome. At the first stage FR in Central Kazakhstan, snow with a pH range from 1.7 to 9.0 was contaminated by N-containing substances (maximal value in g/L): UDMH – 0.27, NDMA – 0.04, NO3− – 19, NH4+ – 0.04 and NO2− – 0.13. The first stage landing resulted in snow contamination by soil dust particles and N-containing substances at a rate of 13 g/m2 and 82 mg/m2/day, respectively. The maximal permissible addition (MPA) for UDMH, NDMA and NO3− to the 0–5 cm layer of soil was estimated at 0.06, 0.006 and 70.2 mg/m2, respectively. At the second stage FR in the NE Altai, substances released by space transportation were absent and the concentration of NO3− and NH4+ corresponded to the natural background level. The index of contamination (IC) was used for characterizing the degree of snow contamination by N-containing substances. A simulation model was developed for analysing the dependence of snow contamination by rocket propellant components on the weather parameters.

Daminozide (Alar) was found to produce N-nitrosodimethylamine (NDMA) and N-nitrodimethylamine (NITDMA) when treated with nitrite in acidic solution. Unsymmetrical dimethylhydrazine (UDMH), the hydrolysis product of Daminozide, gave the same products. Use of 15N-nitrite and 15N-Daminozide showed that both the nitroso group of NDMA and the nitro group of NITDMA arise from the nitrite.

N-Dimethylnitrosamine (NDMA) has aroused increasing concern among public health agencies. It is necessary to develop some effective methods to remove NDMA from drinking water. A reductive process has been investigated as an alternative treatment method for NDMA removal from water. In this manuscript, zero-valent iron nanoparticles (ZVINPs) were synthesized, and then supported on mesoporous silica materials with high surface area (MCM-41) to prepare a stable ZVINP/MCM-41 nanocomposite. X-ray diffraction measurements showed the stabilization of the ZVINPs upon their support on MCM-41, which enhanced their activity. The ZVINP/MCM-41 nanocomposite was used for the catalytic reduction of NDMA in the model solution, and the results showed the dependency of the removal process on the ZVINP/MCM-41 mass, time of removal, and solution pH. The mechanism of NDMA reduction by ZVINP/MCM-41 was studied, and the results showed the conversion of NDMA to unsymmetrical dimethylhydrazine, dimethylamine (DMA) and NH4+. The product analysis found that in the process of removal, adsorption and reduction existed at the same time.

Compounds with N,N-dimethylhydrazine moieties ((CH3)2N-N-) form N-nitrosodimethylamine (NDMA) during ozonation, but the relevant reaction chemistry is hitherto poorly understood. This study investigated the reaction kinetics and mechanisms of NDMA formation during ozonation of unsymmetrical dimethylhydrazine (UDMH) and daminozide (DMZ) as structural model N,N-dimethylhydrazine compounds. The reaction of ozone with these NDMA precursor compounds was fast, and kO3 at pH 7 was 2 × 106 M−1 s−1 for UDMH and 5 × 105 M−1 s−1 for DMZ. Molar NDMA yields (i.e., Δ[NDMA]/Δ[precursor] × 100) were 84% and 100% for UDMH and DMZ, respectively, determined at molar ozone dose ratio ([O3]0/[precursor]0) of ≥4 in the presence of tert-butanol as hydroxyl radical ( OH) scavenger. The molar NDMA yields decreased significantly in the absence of tert-butanol, indicating OH formation and its subsequent reaction with the parent precursors forming negligible NDMA. The k OH at pH 7 was 4.9 × 109 M−1 s−1 and 3.4 × 109 M−1 s−1 for UDMH and DMZ, respectively. Reaction mechanisms are proposed in which an ozone adduct is formed at the nitrogen next to N,N-dimethylamine which decomposes via homolytic and heterolytic cleavages of the –N+-O-O-O− bond, forming NDMA as a final product. The heterolytic cleavage pathway explains the significant OH formation via radical intermediates. Overall, significant NDMA formation was found to be unavoidable during ozonation or even O3/H2O2 treatment of waters containing N,N-dimethylhydrazine compounds due to their rapid reaction with ozone forming NDMA with high yield. Thus, source control or pre-treatment of N,N-dimethylhydrazine precursors and post-treatment of NDMA are proposed as the mitigation options.

Snow cover contamination is assessed in the impact areas of the first stage of the expandable launch system Proton in Central Kazakhstan. It was revealed that the chemical effect ofpropellants on the snow cover is local. The increase in the content of the following high-toxic substances in the snow was registered: unsymmetrical dimethylhydrazine, nitrosodimethylamine, and nitrate and nitrite ions. The most part of the pollutants is localized in the upper 5-cm snow layer. Nitrogen tetroxide decreases the value of pH, and unsymmetrical dimethylhydrazine increases it. The inflow of calcareous soil particles to the atmosphere and their subsequent fallout result in the alkalization of snow and in the neutralization of acidification by nitrogen tetroxide accompanied by the formation ofthe salts of nitric acid and nitrous acid.