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Copyright of Journal of Xi'an Jiaotong University is the property of Editorial Office of Journal of Xi'an Jiaotong University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The evaporation characteristics of unsymmetrical dimethylhydrazine droplets with different initial diameters in a subcritical environment were experimentally investigated with the temperature–pressure separation technique. The evaporation processes of unsymmetrical dimethylhydrazine droplets with different initial diameters in this environment have the same general pattern. All the studied droplets exhibit a short transient heating phase and a steady-state evaporation phase obeying d 2 . Notably, the expansion of the transient heating phase gradually increases with increasing ambient pressure. The change in diameter squared ∆ d 2 m a x increases from 1.03% at 1 MPa to 12.48% at 5 MPa. Under subcritical conditions, the evaporation rate decreases linearly with decreasing droplet diameter, and the droplet evaporation lifetime increases linearly. Changes in the initial droplet diameter may still have a large effect on droplets smaller than those studied here. When the ambient pressure is not greater than 3 MPa, the change in the steady-state evaporation time for both medium- and large-diameter droplets accounts for more than 70% of the variation in the droplet evaporation lifetime. As the ambient pressure increases to 4 MPa and 5 MPa, the percentage of the change in the transient heating time contributing to the variation in the droplet evaporation lifetime gradually increases to more than 45%. [ABSTRACT FROM AUTHOR]

Unsymmetrical dimethylhydrazine (UDMH) is a common liquid propellant widely used in rocket engines and other applications. The safety of UDMH in service is affected by its slow oxidation during long-term storage to form impurities such as dimethylamine (DMA) and formaldehyde dimethylhydrazone (FDH). How these impurities affect combustion performance is not known, and in order to assess these effects, the present experiments investigated the combustion characteristics of self-igniting fuels and carried out ignition delay time measurements and flame propagation velocity measurements of pure UDMH and its denatured mixtures in a nitrogen tetroxide (NTO) atmosphere. This experiment was carried out to measure the delay time of hedge ignition of pure UDMH and qualitative analysis of its flame propagation properties under vacuum conditions at room temperature (T = 293 K). Ignition delay time measurements and flame propagation characterization were performed under the same experimental conditions for UDMH mixed with 1%, 5% and 10% FDH, UDMH mixed with 1%, 5% and 10% H2O, UDMH mixed with 1%, 5% and 10% DMA, as well as for UDMH mixed with the same proportions of the three substances (1%, 5% and 10%). The flame propagation characteristics were analyzed. The results showed that the incorporation of DMA, H2O and FDH in different proportions could inhibit the combustion of UDMH to varying degrees and prolong its ignition delay time. It is worth noting that the introduction of FDH had the least effect on it, and the least effect was observed at a concentration of 1%. In contrast, the effect of DMA on UDMH is more obvious, and the addition of H2O has the largest increase in the ignition delay time of UDMH. In the flame propagation experiment, the flame of the experimental group adding H2O can no longer fill the whole experimental window, while the other experimental groups can still make the window full of flame. Combined with the measurements of the ignition delay time, it can be seen that the moisture content has the greatest effect on the combustion characteristics. [ABSTRACT FROM AUTHOR]

1,1-Dimethylhydrazine (Heptil, rocket fuel (UDMH)) is characterized by extremely high toxicity, teratogenicity and the ability to constantly absorb water from the atmosphere, losing its energy characteristics. In this regard, as well as due to the alternative fuel ("Angara") transition, there is a need for UDMH utilization in huge amounts. A more benign approach involves its immediate reaction with a formalin solution to form 1,1–dimethyl-2-methylene hydrazone (MDH), which is significantly less toxic by an order of magnitude. MDH can then be polymerized under acidic conditions, and the resulting product can be burned, yielding a substantial amount of nitrogen oxides. We propose an alternative to incineration by involving MDH in organic synthesis. We studied the reactions of MDH and its analog N,N-dimethyl-2-(methylenamino)ethane-1-amine (MDEA) with available CH-acids: tetracyanoethylated ketones (TCEKs) based on cyclohexanone, 4-propylcyclohexanone, 2-methylcyclohexanone, cyclododecanone and tetracyanoethane. The structures synthesized were confirmed by IR, 1H, 13C NMR and mass spectroscopy methods. MDH-based adducts were also identified by X-ray structural analysis. TCEKs and MDH, as well as TCEK based on cyclohexanone and MDEA, form bi- and tricyclic structures: pyrrolo [3,4c]-quinolines (using TCEKs based on cyclohexanone and 4-propylcyclohexanone), epiminomethanoquinoline-3,4-dicarbonitrile (using TCEK based on 2-methylcyclohexanone) and cyclododec[b]pyran-3,4-dicarbonitrile (using TCEK based on cyclododecanone). MDH and TCNEH2 formed a pyrrole derivative. Thus, we synthesized the structures that are of interest for molecular design and pharmaceutical chemistry. [ABSTRACT FROM AUTHOR]

The evaporation characteristics of unsymmetrical dimethylhydrazine droplets with different initial diameters in a subcritical environment were experimentally investigated with the temperature–pressure separation technique. The evaporation processes of unsymmetrical dimethylhydrazine droplets with different initial diameters in this environment have the same general pattern. All the studied droplets exhibit a short transient heating phase and a steady-state evaporation phase obeying d2. Notably, the expansion of the transient heating phase gradually increases with increasing ambient pressure. The change in diameter squared ∆d2max increases from 1.03% at 1 MPa to 12.48% at 5 MPa. Under subcritical conditions, the evaporation rate decreases linearly with decreasing droplet diameter, and the droplet evaporation lifetime increases linearly. Changes in the initial droplet diameter may still have a large effect on droplets smaller than those studied here. When the ambient pressure is not greater than 3 MPa, the change in the steady-state evaporation time for both medium- and large-diameter droplets accounts for more than 70% of the variation in the droplet evaporation lifetime. As the ambient pressure increases to 4 MPa and 5 MPa, the percentage of the change in the transient heating time contributing to the variation in the droplet evaporation lifetime gradually increases to more than 45%.

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. [ABSTRACT FROM AUTHOR]

In this study, mesoporous TiO2 with various hydrolysis rates were prepared and combined with H2O2 for the photodegradation of unsymmetrical dimethylhydrazine (UDMH) under VUV irradiation. Results showed that the mesoporous TiO2 synthesized by the hydrolysis in water (MT100) exhibited a good mesoporous structure and the largest specific surface area (178.85 m2 g−1). Consequently, MT100 showed the best degradation efficiency, with the rate constant (k) for VUV/MT100 and VUV/MT100/H2O2 of 0.0185 and 0.2595 min−1, respectively, which was 1.4 and 4.0 times of that of P25. The addition of H2O2 significantly enhanced the degradation efficiency by photoactivation of H2O2 and the synergistic effect. The rate constant and the mineralization rate (after a 3-h treatment) increased by 13 and 3.8 times when 40 mM H2O2 was added into VUV/MT100. The weak alkaline condition (pH = 9) would facilitate the degradation of UDMH. The ⋅OH was the key oxidizing species in VUV/MT100/H2O2. Eight intermediates were detected during the degradation and the possible pathways of UDMH degradation in VUV/MT100/H2O2 process were proposed. VUV/MT100/H2O2 provides an efficient method to degrade UDMH.

A series of GO/g-C3N4 aerogel materials were prepared by the methods of ultrasonic peeling, solution cross-linking and freeze-drying, and the proportion of raw materials were optimized. The materials were characterized by SEM, XRD, and UV-vis absorption spectrum. The photocatalytic activity was evaluated by the degradation of unsymmetrical dimethylhydrazine (UDMH) wastewater. The pure g-C3N4 aerogel was dominated by mesoporous structure. As the graphene oxide (GO) ratio increases, the layered structure and macroporous structure of the material gradually increase, and all show strong adsorption performance. When the mass fraction of GO is 25%, the photocatalytic degradation of UDMH wastewater is the best and the performance is stable after 5 cycles, the photocatalytic activity is only reduced by 7.15%. Through the study on the energy band structure, characterization of photoelectric effect and PL spectrum, the results show that the g-C3N4 molecular orbital energy level and band gap (Eg) were impacted by the cross-linking between the π-π bond of GO layers and the aromatic ring of g-C3N4, which improve the response performance to visible light. The metallic properties of GO facilitate the rapid separation of photogenerated electron-hole pairs and improve the photocatalytic activity. According to the band gap calculation and the intrinsic molecular orbital of the material, the main active species for GOCN photocatalytic degradation of UDMH wastewater are ·O-2 and h+.

Thirty two commercially available standards were used to determine chromatographic retention indices for three different stationary phases (non-polar, polar and mid-polar) commonly used in gas chromatography. The selected compounds were nitrogen-containing heterocycles and amides, which are referred to in the literature as unsymmetrical dimethylhydrazine (UDMH) transformation products or its assumed transformation products. UDMH is a highly toxic compound widely used in the space industry. It is a reactive substance that forms a large number of different compounds in the environment. Well-known transformation products may exceed UDMH itself in their toxicity, but most of the products are poorly investigated, while posing a huge environmental threat. Experimental retention indices for the three stationary phases, retention indices from the NIST database, and predicted retention indices are presented in this paper. It is shown that there are virtually no retention indices for UDMH transformation products in the NIST database. In addition, even among those compounds for which retention indices were known, inconsistencies were identified. Adding retention indices to the database and eliminating erroneous data would allow for more reliable identification when standards are not available. The discrepancies identified between experimental retention index values and predicted values will allow for adjustments to the machine learning models that are used for prediction. Previously proposed compounds as possible transformation products without the use of standards and NMR method were confirmed. [Display omitted] • GC-MS RIs were obtained for 32 substances, which are UDMH transformation products. • Very little RI data for UDMH transformation products is present in the NIST database. • Inconsistencies were found among those compounds for which the indices are known. • The data obtained will allow to adjust ML methods for predicting indices. [ABSTRACT FROM AUTHOR]

The GO/CMC composite absorbent was prepared by the solution・blen(ling method using graphene oxide (GO) and carboxymethyl chitosan (CMC) as raw materials and characterized by FTIR, Raman, SEM, TEM, and TG・DTG・ The results show that a large number of carboxyl and epoxy groups are present in GO/CMC and that GO and CMC are well compounded・ The performance of the absorption treatment of unsymmetrical dimethylhydrazine (UDMH) wastewater is influenced by the composition of the absorbent, the addition of oxidizing agents, and inorganic phase change materials. Absorbent absorption treatment is most effective when GO is added at 10% ・ The oxidizing agent Ca(C1O)2 can undergo a more violent redox reaction with UDMH. The reaction intensity is effectively mitigated by the doping of absorbents ・ When 0. 5 g of 10% GO/CMC and 2. 5 g of Ca(C1O)2 were added, the maximum concentration of volatilized UDMH gas was only 58. 69 mg/m3 ・ Furthermore, the addition of inorganic phase change materials further reduces the system temperature and the maximum concentration of volatile UDMH gas. The GO/CMC composite absorbent can provide a useful exploration for the emergency absorption treatment of high concentration UDMH wastewater. [ABSTRACT FROM AUTHOR]

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 10-4 M. The changes are dose-dependent. After exposure to UDMH in high concentrations (10-2 M), the changes in the functional parameters became irreversible. The obtained results provide evidence for the organ-specific effect of UDMH on visceral muscle organs. [ABSTRACT FROM AUTHOR]

The article presents the results of a study of synthesis and accumulation of heptyl in the plants growing on the 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 terrae-albae Krasch., although they can cause anatomical and morphological changes in the roots and leaves of the plants grown on the soil contaminated with UDMH. The 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. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The TiO2/g-C3N4 composites were prepared by the hydrothermal method with cetyltrimethyl ammonium bromide (CTAB). The influence of CTAB on the structural properties and spectral properties of the composites was studied. The samples were characterized by XRD, TEM, N2 adsorption-desorption, FT-IR, UV-Vis DRS and PL, meanwhile, the samples were used to degrade unsymmetrical dimethyl hydrazine (UDMH) wastewater under visible light. The results show that the crystal structure of TiO2/g-C3N4 composites assisted by CTAB is intact,with smaller particle size of nanoparticles and uniformly distributed on g-C3N4 sheets. The specific surface area of the composites increases and the mesoporous is more abundant, the adsorption ledge of the composites is expanded to 450nm, the recombination rate of hole-electron reduces obviously. Photocatalytic results show that the UDMH degradation efficiency of TiO2/g-C3N4 (CTAB) reaches 83.2% in 120min, which is improved by 13.7% than that of the no CTAB-assisted composites.

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. [ABSTRACT FROM AUTHOR]

The main challenge facing the anodic electro-Fenton through the 2e– water oxidation reaction (WOR) for toxics degradation lies in the electrode's stability, because the anodic oxygen evolution (OER) generated O 2 will inevitably exfoliate the electro-active components loaded on the electrode substrate. To address this point, two aspects need attention: 1) Identifying a catalyst that exhibits both excellent electrocatalytic activity and selectivity can improve the faradaic efficiency of hydrogen peroxide (H 2 O 2); 2) Employing novel methods for fabricating highly stable electrodes, where active sites can be firmly coated. Consequently, this study utilized microarc oxidation (MAO) to prepare a ceramic film electrode Zn 2 SnO 4 @Ti at 300 V. Zn 2 SnO 4 acts as an WOR electrocatalyst and further improved the generation of H 2 O 2 for treating real wastewater containing Unsymmetrical Dimethylhydrazine (UDMH). From the perspective of characterization of electrode structure, Zn 2 SnO 4 @Ti forms a stable active coating, the electrochemical yield of H 2 O 2 is high up to 78.4 μmol h−1 cm−2, and the selectivity of H 2 O 2 is over 80% at 3.3 V vs. RHE, which can be fully applied to scenarios where it is inconvenient to transport H 2 O 2 and need in-situ safe production. Additionally, the prepared electrodes exhibit significant stability, suitable for various applications, providing insightful preparation strategies and experiences for constructing highly stable anodes. • Highly active and selective 2e– WOR electrodes were prepared using Zn 2 SnO 4 with TC4. • Zn 2 SnO 4 @Ti–300V achieved a high H 2 O 2 yield of 78.4 μmol h−1 cm−2 at 3.3 V vs. RHE voltage. • Zn 2 SnO 4 improved its 2e– WOR stability by MAO device. • Zn 2 SnO 4 @Ti can effectively degrade UDMH wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel ZIF-8-derived magnetic composites were synthesized with chitosan as an external carbon source. • FCZ@C-600 exhibited an extremely high adsorption capacity (185.70 mg/g) for UDMH. • The successful attachment of CS/ZIF-8 increased the effective adsorption sites on the adsorbents. • Potential adsorption mechanisms can be defined (mainly electrostatic interactions, diffusion, and hydrogen/coordination bonds). • The new adsorbents showed excellent recyclability, stability, and biosafety for successive UDMH adsorptions. Efficient and convenient removal of hazardous unsymmetrical dimethylhydrazine (UDMH) remains challenging for ecological security and human health. In this work, ZIF-8-derived magnetic porous carbons (FCZ@Cs) were synthesized via layer-by-layer self-assembly and pyrolysis using chitosan as an external carbon source. The optimal pyrolysis temperature of FCZ@Cs is 600 °C and the maximum adsorption capacity of FCZ@C-600 for UDMH is 185.70 mg/g at 298 K. Moreover, FCZ@C-600 has wide pH adaptability and good resistance to acid, natural organic matter, and interfering ions. UDMH adsorption onto FCZ@C-600 and ZIF-8-600 conforms to pseudo-second-order and Langmuir models. Thermodynamic studies demonstrate that the adsorption performance is endothermic and favorable. Mechanisms investigations further identify electrostatic interactions, diffusion, and hydrogen/coordination bonds as the greatest contributors to UDMH adsorption. Notably, magnetic FCZ@C-600 can be readily separated by a magnet and exhibits high stability with an adsorption capacity of 42.05 mg/g after six cycles. Furthermore, the leaching concentration of Fe and Zn can be as low as 0.3 mg/L and 1.0 mg/L (pH ≥ 4), respectively. UDMH wastewater after adsorption also shows good biosafety. This work provides insights into the development of emerging metal-organic framework-derived adsorbents with multifunctionality and good sustainability for efficient wastewater treatment. [ABSTRACT FROM AUTHOR]

Lignin, a large scale by-product of papermaking and bioethanol production, is applied now in various fields. One of the main areas of use is in the development of different adsorbents, including those intended for detoxification of the spills of 1,1-dimethylhydrazine-based rocket fuel. The present work has shown the possibility of oxidative modification of hydrolytic lignin by hydrogen peroxide to improve the efficiency of the adsorbent. The change in functional composition of the modified adsorbent was studied by IR and NMR spectroscopy. It was shown that the oxidative treatment led to an increase in the content of carbonyl and carboxyl groups, which act as the active adsorption centres for hydrazine molecules. The optimum oxidation conditions were found. An increase in treatment duration from 15 to 120 min and in concentration of hydrogen peroxide from 6 to 30% did not have a significant effect on the functional composition and adsorption properties of lignin.

The majority of unsymmetrical dimethylhydrazine (UDMH) treatments produce lots of toxic by-products, among which N-Nitrosodimethylamine (NDMA) is a strong carcinogen. The compositions of the by-products are important for evaluating the treatment efficiency and understanding the UDMH degradation mechanism to achieve UDMH mineralization. The intermediate and end products of UDMH treatment with different oxidants were investigated by using a simple and fast method, solid-phase micro-extraction (SPME) in combination with gas chromatography–mass spectrometry (GC-MS). The effects of several parameters (coating fibre, salt addition, pH, sampling time and desorption time) were studied to optimize analyte recovery. The best response can be attained by the 65 µm PDMS/DVB fibre at pH 7 during 10 min after desorption of 1 min in the GC inlet. The intermediate and final oxidative products of UDMH wastewater treatment with different oxidants (O3, Mn2+/O3, Fe2+/H2O2) were investigated. The results showed that the UDMH treatment with O3 could lead to high yields of NDMA. Metal catalytic ozonation could largely minimize the formation of NDMA. No NDMA was observed in the final decontaminated samples after treatment with Fe2+/H2O2. The NDMA formation and degradation mechanism were discussed based on the intermediates. This study is expected to provide useful information for controlling NDMA formation during UDMH wastewater treatment.

Abstract—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. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We describe the syntheses and crystal structures of two molecular salts containing the 1,1-dimethylhydrazinium cation, namely 1,1-dimethylhydrazin-1-ium bromide, C2H9N2+·Br−, (I), and 2,2-dimethylhydrazin-1-ium dihydrogen phosphite, C2H9N2+·H2PO3−, (II). In (I), the cation is protonated at the methylated N atom and N—H...Br hydrogen bonds generate [010] chains in the crystal. In (II), the cation is protonated at the terminal N atom and cation-to-anion N—H...O and anion-to-anion O—H...O hydrogen bonds generate (001) sheets.

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 Nnitrosodymethylamine (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 wildgrowing 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. [ABSTRACT FROM AUTHOR]

Abstract: Products of the interaction of 1,1-dimethylhydrazine with nitrogen dioxide in an aqueous solution are characterized by high-resolution mass spectrometry with electrospray ionization. It was found that more than 200 compounds of CHO, CHN, and CHNO classes formed in the reaction; the main component is extremely dangerous N-nitrosodimethylamine. Among the products of the transformation of 1,1-dimethylhydrazine, N-nitrosodibutylamine is identified for the first time. The results obtained are of importance for understanding processes of the transformation of rocket fuel in surface and ground waters at the places of impact of spent rocket stages containing both the propellant and the oxidant. [ABSTRACT FROM AUTHOR]

Determination of transformation products (TPs) of rocket fuel unsymmetrical dimethylhydrazine (UDMH) in soil is highly important for environmental impact assessment of the launches of heavy space rockets from Kazakhstan, Russia, China and India. The method based on headspace solid-phase microextraction (HS SPME) and gas chromatography-mass spectrometry is advantageous over other known methods due to greater simplicity and cost efficiency. However, accurate quantification of these analytes using HS SPME is limited by the matrix effect. In this research, we proposed using internal standard and standard addition calibrations to achieve proper combination of accuracies of the quantification of key TPs of UDMH and cost efficiency. 1-Trideuteromethyl -1H- 1,2,4-triazole (MTA-d3) was used as the internal standard. Internal standard calibration allowed controlling matrix effects during quantification of 1-methyl- 1H- 1,2,4-triazole (MTA), N,N -dimethylformamide (DMF), and N- nitrosodimethylamine (NDMA) in soils with humus content < 1%. Using SPME at 60 °C for 15 min by 65 µm Carboxen/polydimethylsiloxane fiber, recoveries of MTA, DMF and NDMA for sandy and loamy soil samples were 91–117, 85–123 and 64–132%, respectively. For improving the method accuracy and widening the range of analytes, standard addition and its combination with internal standard calibration were tested and compared on real soil samples. The combined calibration approach provided greatest accuracies for NDMA, DMF, N -methylformamide, formamide, 1H -pyrazole, 3-methyl- 1H -pyrazole and 1H -pyrazole. For determination of 1-formyl-2,2-dimethylhydrazine, 3,5-dimethylpyrazole, 2-ethyl -1H -imidazole, 1H- imidazole, 1H -1,2,4-triazole, pyrazines and pyridines, standard addition calibration is more suitable. However, the proposed approach and collected data allow using both approaches simultaneously. [ABSTRACT FROM AUTHOR]

Lignin, a large scale by-product of papermaking and bioethanol production, is applied now in various fields. One of the main areas of use is in the development of different adsorbents, including those intended for detoxification of the spills of 1,1-dimethylhydrazine-based rocket fuel. The present work has shown the possibility of oxidative modification of hydrolytic lignin by hydrogen peroxide to improve the efficiency of the adsorbent. The change in functional composition of the modified adsorbent was studied by IR and NMR spectroscopy. It was shown that the oxidative treatment led to an increase in the content of carbonyl and carboxyl groups, which act as the active adsorption centres for hydrazine molecules. The optimum oxidation conditions were found. An increase in treatment duration from 15 to 120 min and in concentration of hydrogen peroxide from 6 to 30% did not have a significant effect on the functional composition and adsorption properties of lignin. [ABSTRACT FROM AUTHOR]

Photocatalysis technology could utilize solar energy to degrade many toxic pollutants and provides possibility to deal with unsymmetrical dimethylhydrazine (UDMH) wastewater with less energy consumption. In this study, well-aligned TiO nanorod arrays (TiO NRAs) were grown directly on transparent conductive glass (FTO) via a hydrothermal method, and TiO NRAs/CdS heterostructure films were prepared by decorating TiO NRAs with CdS nanoparticles through successive ion layer adsorption and reaction (SILAR). Under visible light, the TiO NRAs/CdS heterostructure displays enhanced photodegrading capacity compared with the bare TiO NRAs, and the highest photodegradation rate, 27.5% higher than that of the bare TiO NRAs, was achieved by the sample with 15 SILAR cycles. Additionally, the solution pH had some influence on the degradation process, which shows that the best degradation rate can be achieved in the neutral solution (pH is ca. 7.2), and the photodegradation process can be better in alkaline solution than in the acid solution. Moreover, the visible photocatalytic stability of the TiO NRAs/CdS sample was investigated. Finally, the underlying photocatalytic mechanism was discussed according to the photoelectrochemical and photoluminescence results. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We describe the syntheses and crystal structures of two molecular salts containing the 1,1-dimethylhydrazinium cation, namely 1,1-dimethylhydrazin-1-ium bromide, C2H9N2+Br-, (I), and 2,2-dimethylhydrazin-1-ium dihydrogen phosphite, C2H9N2+-H2PO3-, (II). In (I), the cation is protonated at the methylated N atom and N-H⋯Br hydrogen bonds generate [010] chains in the crystal. In (II), the cation is protonated at the terminal N atom and cation-to-anion N-H⋯O and anion-to-anion O-H⋯O hydrogen bonds generate (001) sheets. [ABSTRACT FROM AUTHOR]

[Display omitted] • AgCo/SBA-15 exhibited the highest activity in PMS activation to eliminate UDMH. • The synergy between Ag and Co account for the superior catalytic activity. • 1O 2 was the dominant reactive oxygen species in AgCo/SBA-15/PMS. • PMS activation mechanism and UDMH degradation pathways were proposed. A set of SBA-15 supported Co-based bimetallic catalysts was prepared by the incipient wetness impregnation method and then used to activate peroxymonosulfate (PMS) to eliminate unsymmetrical dimethylhydrazine (UDMH). The physicochemical properties of catalysts were studied by serious of techniques. The reusability of the catalyst and the influence of reaction parameters were investigated. The results showed that AgCo/SBA-15 exhibited the best degradation efficiency. The good conductivity of Ag nanoparticles, strong UDMH adsorption ability, moderate Co ions leaching concentration, and the synergistic effect between Co and Ag were responsible for the excellent catalytic activity. Complete UDMH (100 mg/L) degradation and 75.2 % mineralization could be achieved at the reaction times of 15 and 180 min, respectively. The quenching experiments and EPR analysis indicated 1O 2 played a dominant role in UDMH degradation. Furthermore, the possible degradation pathways were proposed according to the GC–MS intermediates and DFT calculation. This study provides new insights into heterogeneous activation of PMS and offers an efficient method for wastewater treatment. [ABSTRACT FROM AUTHOR]

An advanced oxidation process based on using a combination of hydrodynamic cavitation, and acoustic cavitation has been investigated for decontamination of unsymmetrical dimethylhydrazine (UDMH) waste water. The effect of various operating parameters such as velocity, inlet pressure, temperature, and pH on the extent of UDMH conversion has been studied with the aim of maximizing the extent of decontamination. It has been observed that an optimum pressure and operating temperature in a moderately acidic medium are more favorable for a rapid removal of UDMH. No toxic byproduct was observed in the decontaminated samples, although the oxidation process eliminated up to 97% of UDMH. A synergistic effect has been obtained by a hybrid method of acoustic and hydrodynamic cavitation. The total and per pass, synergistic effect achieves 16% and 68%, respectively. Due to a high optimization potential, this hybrid method can be visualized as a new step in wastewater treatment facilities involving UDMH or other refractory toxic materials. [ABSTRACT FROM AUTHOR]

A pilot scale hydrodynamic cavitation (HC) reactor, using iron metal blades, as the heterogeneous catalyst, with no external source of H 2 O 2 was developed for catalytic decontamination of unsymmetrical dimethylhydrazine (UDMH) waste water. In situ generation of Fenton reagents suggested an induced advanced Fenton process (IAFP) to explain the enhancing effect of the used catalyst in the HC process. The effects of the applied catalyst, pH of the initial solution (1.0–9.7), initial UDMH concentration (2–15 mg/l), inlet pressure (5.5–7.8 bar), and downstream pressure (2–6 bar), have been investigated. The results showed that the highest cavitation yield can be obtained at pH 3 and initial UDMH concentration of 10 mg/l. Also, an increase in the inlet pressure would lead to an increase in the extent of UDMH degradation. In addition, the optimum value of 3 bar was determined for the downstream pressure that resulted to 98.6% degradation of UDMH after 120 min of processing time. Neither n-nitrosodimethylamine (NDMA) nor any other toxic byproduct (/end-product) was observed in the investigated samples. Formic acid and acetic acid, as well as nitromethane, were identified as oxidation by-products. The present work has conclusively established that hydrodynamic cavitation in combination with Fenton’s chemistry can be effectively used for the degradation of UDMH. [ABSTRACT FROM AUTHOR]

• The effect of different oxygen-functional groups of GO on the adsorption of UDMH was investigated. • A green preparation method of carboxy-rich GO was explored. • The inhibition effect of carboxy-rich GO on UDMH escape was verified. Unsymmetrical dimethylhydrazine (UDMH) is a widely used liquid propellant in the aerospace field but possesses a high leakage risk. Therefore, water spray device has been extensively used in all limited spaces of UDMH storage. However, once it is triggered, it will in turn create a large pool of liquid UDMH inside the storage facility and continue to produce toxic UDMH gas, hindering leak remediation and rescue activities. To address this practical problem, the present study first explores the graphene oxide structure based on the first principles study and then designs the most promising exogenous additive structure. Subsequently, carboxyl-rich graphene oxide materials are synthesized employing a modified Hummers method, which meets the requirement of the exogenous additive structure and environmental friendliness. Finally, the experimental results show that the use of graphene oxide with carboxyl-rich structure for UDMH leakage decreases the maximum UDMH escape amount and procure valuable time for subsequent emergency operations. [ABSTRACT FROM AUTHOR]

The treatment of wastewater containing UDMH was investigated using electrolyzed oxidizing water (EOW) integrated with a membrane bioreactor (MBR). The MBR was also operated alone as a reference. The effect of combining MBR with EOW was discussed in terms of the resulting concentrations of UDMH, COD, and the main byproducts. The results showed that EOW-MBR process removed 99.9% of UDMH from water containing 500 mg/L UDMH. Combining EOW and MBR did not have any significant drawbacks with respect to biological or filtration processes with COD removal rates in the range 93-95%. The concentrations of the main by-products (dimethylamine, formaldehyde dimethylhydrazone, and N-nitrosodimethylamine) were greatly reduced. Compared with MBR, the benefits of using the EOW-MBR process are evident for the removal of UDMH and its by-products. [ABSTRACT FROM AUTHOR]

Organic gel propellants are promising candidates for a variety of rocket motor and scramjet applications, since they are intrinsically safe and provide high performance. It is well known that organic gel fuel droplets exhibit distinct combustion characteristics compared with conventional liquid fuel droplets, and furthermore an understanding of the ignition delay and lifetime of these droplets is critical to the improvement of combustor design. In this work, investigations of the combustion of unsymmetrical dimethylhydrazine (UDMH) organic gel droplets in different nitrogen tetroxide (NTO) oxidizing atmospheres were conducted using two sets of experimental apparatus. The combustion characteristics under different conditions of temperature and pressure were compared and analyzed based on the flame shapes observed during experimentation. From these trials, an unsteady combustion model was developed and used for the numerical simulation of spray-sized UDMH organic gel droplet combustion in an NTO atmosphere. The hypergolic ignition and burning characteristics of the organic gel droplets under conditions simulating either engine startup or steady state combustion were compared, and changes in ignition delay and droplet lifetime with ambient temperature and pressure were analyzed. The experimental and numerical results show that the UDMH organic gel droplets exhibit periodic swell-burst behavior following the formation of an elastic film at the droplet surface. Each droplet burst results in fuel vapor ejection and flame distortion, the intensity of which declines with increasing ambient pressure. However, the swell-burst period is extended with increasing ambient pressure, which results in potential flameout. Under conditions of low temperature and pressure similar to those at engine startup, the ignition delay and lifetime of spray-sized gel droplets decrease with increasing temperature or pressure, although there is a sharp increase in droplet lifetime when the ambient pressure reaches a critical value associated with flameout. The ignition delay was found to be a rate-limited phenomenon linked to the droplet heating rate. The proportion of ignition delay and droplet lifetime due to droplet heating-up decreased with increasing temperature or decreasing pressure. Conversely, at high temperatures and pressures simulating the engine's steady state operating conditions, the droplets were observed to flameout after several swell-burst periods and both ignition delay and lifetime decreased monotonically with increasing temperature or pressure. The ignition delay time was determined to be rate-limited by gas phase chemical reactions and contributed very little to the overall droplet lifetime compared with the engine startup condition. [ABSTRACT FROM AUTHOR]

A procedure has been developed for the determination of unsymmetrical dimethylhydrazine (UDMH) based on precolumn derivatization with glyoxal and determination of the produced derivative, mono-1,1-dimethylhydrazone of glyoxal, by reversed-phase HPLC ( RP-HPLC) with UV detection at 305 nm. It has been demonstrated that the reaction of UDMH with an excess of glyoxal in solution quantitatively yields one stable product within 20 min at 25°C at pH 3.5. To increase the sensitivity of UDMH determination it has been proposed to perform solid-phase extraction preconcentration of the derivative from a 25-mL sample portion on cartridges containing Strata SDB-L polymer adsorbent. The analytical range of UDMH determination in water is 0.5-10000 μg/L or 0.01-20 μg/L using preconcentration. The relative standard deviations of UDMH determination ( n = 3) do not exceed 0.12 and 0.25 without and with preconcentration, respectively. The accuracy of UDMH determination is confirmed by the analysis of spiked samples and by RP-HPLC determination with preliminary derivatization with 4-nitrobenzaldehyde as independent method. [ABSTRACT FROM AUTHOR]

For the fast and accurate determination of trace unsymmetrical dimethylhydrazine (UDMH), a high performance liquid chromatography method was developed after the optimization of the chromatographic conditions by comparing the detection results under the different detection wavelengths, types and proportions of the mobile phase and the optimization of the derivative conditions by comparing the detection results under the different derivative time, the solution pH values and the dosages of derivatizing regents. The optimized conditions are as following, for the chromatography: separation by the C18 column and detection by the ultraviolet detector, 390 nm as the wavelength, the acetonitrile and water with a volume ratio of 4:1 were taken as the mobile phases; for the derivatization: derivatization with 4-nitrobenzaldehyde (the molar concentration is 3 mmol/L in the total volume), the solution pH 5. 5, heating in a water bath at 75 °C for 15 min. The results showed that under the optimized conditions, the retention time of the derivative product was 2. 64 rain, the correlation coefficients of peak area (peak height) to mass concentration was equal to or more than 0. 999 4, the detection limit was 0. 5 µg/L. For the simulated water sample, the relative standard deviation was equal to or less than 1.69%, and the recovery of standard addition was 95.7% - 102. 7%. The method is rapid in determination, and has good linear relationship, a low detection limit, the precision and accuracy for determining trace UDMH in water. [ABSTRACT FROM AUTHOR]