Search

Electrocatalytic hydrogenation (ECH) enables the sustainable production of chemicals under ambient condition; however, suffers from serious competition with hydrogen (H2) evolution and the use of precious metals as electrocatalysts. Herein, molybdenum disulfide is for the first time developed as an efficient and noble-metal-free catalyst for ECH via in situ intercalation of ammonia or alkyl-amine cations. This interlayer engineering regulates phase transition (2H → 1 T), and effectively ameliorates electronic configurations and surface hydrophobicity to promote the ECH of biomass-derived oxygenates, while prohibiting H2 evolution. The optimal one intercalated by dimethylamine (MoS2-DMA) is capable of hydrogenating furfural (FAL) to furfuryl alcohol with high Faradaic efficiency of 86.3%–73.3% and outstanding selectivity of >95.0% at −0.25 to −0.65 V (vs. RHE), outperforming MoS2 and other conventional metals. Such prominent performance stems from the enhanced chemisorption and surface hydrophobicity. The chemisorption of H intermediate and FAL, synchronously strengthened on the edge-sites of MoS2-DMA, accelerates the surface elementary step following Langmuir-Hinshelwood mechanism. Moreover, the improved hydrophobicity benefits FAL affinity to overcome diffusion limitation. Discovering the effective modulation of MoS2 from a typical H2 evolution electrocatalyst to a promising candidate for ECH, this study broadens the scope to exploit catalysts used for electrochemical synthesis.

ZSM-22/ZSM-23 intergrowth zeolite was successfully synthesized by hydrothermal method with diethylamine and dimethylamine as co-structure directing agents at a dimethylamine/diethylamine molar ratio of 24. The physicochemical properties of ZSM-22/ZSM-23 intergrowth zeolite including the crystallinity, crystal morphology, texture and acidity were determined by XRD, FE-SEM, TEM, N2-physisorption, NH3-TPD, Py-FTIR, and so on; the performance of Pt/ZSM-22/ZSM-23 catalyst prepared by impregnation in the hydroisomerization of n-hexadecane was then investigated. The results indicate that the ZSM-22/ZSM-23 intergrowth zeolite displays the needle-like morphology with the topological structures of both ZSM-22 and ZSM-23, which is rather different from pure ZSM-22 and ZSM-23 and their mechanical mixture. After loading 0.5% Pt, the bi-functional Pt/ZSM-22/ZSM-23 catalyst exhibits excellent performance in the hydroisomerization of n-hexadecane, with a much higher yield of i-C16 products (dominated by mono-branched isomers) than those obtained over Pt supported on ZSM-22 and ZSM-22 and their mechanical mixture.

It reports the preparation and characterization of tungsten(VI) oxide supported rhodium(0) nanoparticles (Rh0/WO3 NPs) being used as catalysts in releasing H2 from dimethylamine borane (DMAB). The reducible nature of WO3 plays a significant role in the catalytic efficiency of rhodium(0) nanoparticles in the dehydrogenation of DMAB. The Rh0/WO3 NPs were in-situ generated from the reduction of Rh2+ ions on the surface of WO3 during the catalytic dehydrogenation of dimethylamine borane in toluene and isolated from the reaction solution after the dehydrogenation to be characterized by using SEM, TEM, XPS, ATR-IR and XRD. The results reveal the formation of Rh0 NPs with a mean particle size of 1.92 ± 0.34 nm dispersed on the surface of tungsten(VI) oxide. Rh0/WO3 NPs are found to be very active catalyst releasing 1.0 equiv. H2 per mole of dimethylamine borane under ambient conditions. Among the various WO3 supported Rh0 NPs with different metal loadings, the sample with 0.1% wt. Rh provide the record catalytic activity (TOF = 2816 h−1) which is one of the highest value ever reported for rhodium-based catalysts in H2 generation from DMAB at 60.0 ± 0.5 °C. Rh0/WO3 NPs were also reusable catalyst in dehydrogenation of DMAB retaining 55% of their initial catalytic activity in the 3rd run of the dehydrogenation reaction. Control experiments were performed at various catalyst concentrations and temperatures to investigate the kinetics of dehydrogenation and to calculate the activation parameters for the reaction.

Amine boranes are solid hydrogen storage materials and are difficult to transport within systems unless dissolved in solvents. The solubility and free energy of solution were experimentally determined for ammonia borane, methylamine borane, dimethylamine borane, trimethylamine borane, and tert-butylamine borane in methanol, ethanol, 1-propanol, 2-propanol, acetonitrile, dimethyl sulfoxide, and tetrahydrofuran. The solubilities of ammonia borane/methylamine borane mixtures in methanol were also measured. The enthalpy of solution was experimentally determined for ammonia borane, methylamine borane, dimethylamine borane, and 30/70 wt% ammonia borane/methylamine borane eutectic in four different solvents: methanol, ethanol, acetonitrile, and dimethyl sulfoxide. For all solutes, dimethyl sulfoxide solutions were the most exothermic or least endothermic. Increased methyl-substitution on the amine led to more endothermic processes. For methanol, ethanol, and acetonitrile, the entropy of solution increased as solubility increased. The entropy of solution for ammonia borane dissolving in dimethyl sulfoxide is negative. COSMO-RS solubility calculations using density functional theory optimized geometries agree relatively well with experimental values for amine borane materials dissolved in polar solvents.

A series of boehmite microspheres with highly effective adsorption performance for Congo red (CR) were successfully prepared via amides assisted hydrothermal method at 180 °C. Effects of dosages and hydrolysates of N,N-dimethylformamide (DMF), amides species including DMF, N-methylformamide (MF) and formamide (FA), and reaction times on their physicochemical properties were studied in detail. It was found that increase on their crystallinity and shell thickness results from the different hydrolysis rates of the amides; amorphous alumina hydrate, boehmite core-shell structure and hollow microspheres were obtained at hydrothermal times of 60, 140 and 360 min, respectively due to the Ostwald ripening. Especially, dimethylamine (DMA) as a hydrolysate of DMF, can effectively regulate the morphologies of the boehmites together with the sulfate ions, and make their pore sizes distribution (PSD) centering at 3–4 nm. Importantly, the boehmite microspheres with specific surface area of 221.3 m2/g shows the maximum adsorption capacity of 847.5 mg/g for CR calculated from Langmuir isotherm model, and its adsorption amount reached a high value of 484.1 mg/g at 60 min due to the mentioned PSD. This template-free hydrothermal method using DMF as precipitant provides an alternative approach for preparing high-performance hydrated alumina for environmental applications.

To thoroughly understand low-temperature oxidation of dimethylamine (DMA), the reaction kinetics of triplet ground state O2 addition to DMA radicals ( CH 3 NH C ˙ H 2 and CH 3 N ˙ CH 3 ) are theoretically investigated. In CH 3 NH C ˙ H 2 + O2, the direct H-abstraction reaction is significant due to its extremely low energy barrier, and the dominant channels involving intermediates, CH 3 NHCH 2 O O ˙ = CH 3 NCH 2 + H O ˙ 2 , CH 3 NHCH 2 O O ˙ = C ˙ H 2 NHCH 2 OOH and C ˙ H 2 NHCH 2 OOH = CH 2 NH + CH2O + O ˙ H , also have much lower barriers than those in reaction system CH 3 CH 2 C ˙ H 2 + O2. In CH 3 N ˙ CH 3 + O2, the O2 addition to N atom has a tight transition state, hindering radical consumption at low temperatures. The second O2 addition to C ˙ H 2 NHCH 2 OOH is further investigated because of its comparable production at low temperatures and elevated pressures. The temperature- and pressure-dependent rate constants are calculated; CH3NCH2 + H O ˙ 2 and CH2NCH2OOH + H O ˙ 2 are the dominant products for the first and second O2 addition reactions, respectively, but the formation of formamides/O-heterocycles + O ˙ H is less important. Our results reveal different reaction pathways of DMA radicals from those of alkyls, and shed light on low-temperature oxidation mechanisms of N-containing fuels.

Monitoring the highly volatile dimethylamine (DMA) vapour pays an important issue for the health and safety of humans. The atomization requires an electronic nose for detecting and controlling the toxic gases in the environment. The binary metal oxides of Titanium dioxide (TiO2) and Vanadium oxide (VOx) have been used for gas/vapour sensing applications for the past few decades. However, the binary metal oxides have low selectivity and sensitivity issues in real-time applications. Therefore, mixed metal oxides are attractive alternates for gas sensing application. The mixed metal oxide TiO2-VOx thin film was deposited by reactive co-sputtering technique and investigated for their structural, morphological, and sensing properties. For the first time, we report the DMA vapour sensing properties of TiO2-VOx at room temperature. Among many vapours, such as methanol, ethanol, formaldehyde, isopropanol, acetone, and DMA, the TiO2-VOx is highly selective towards DMA than the other binary oxides VOx and TiO2. The DMA vapour sensing studies proves that the deposited mixed metal-oxide had better sensing response of ~ 3.6 to a minimum concentration of 10 ppm at room temperature than binary oxides of VOx and TiO2.

Palladium (Pd) on carbon support, electron-enriched by hydrogen incorporation (Pd-H/C), is synthesized via dimethylamine borane complex at multiple temperatures and used for the oxidation of formate (HCOO−). The electronic effect of H is confirmed by physicochemical and electrochemical analysis. Physicochemical analysis revealed no significant changes in the Pd-H/C structures, with changes only in the particle size and dispersion. Pd-H/C 0 °C showed the best catalytic activity for the oxidation of HCOO−, even though it possesses the less electrochemical surface area than commercial Pd/C. Its remarkable power density of 272 mW cm−2 at the nominal cell voltage of 0.5 V is recorded in single cell operation. The observed performance is attributed to the electronic effect brought by the incorporation of H in the Pd lattice. Still the electronic effect of H does not always compensate for the small ECSA caused by large particle size and severe agglomeration.

In this work, active and stable catalyst for the dehydrogenation reaction of dimethylamine borane (DMAB) in solvent-free medium at room temperature has been prepared. The method is based on preparing in-situ monodispersed gold nanoparticles (AuNPs) by reducing the one dimensional polymer of gold(I):6-thioguanosine hydrogel by DMAB; which acts as reducing and stabilizing agent. Monitoring time-dependent to build the surface plasmon resonance (SPR) band for the formed AuNPs was carried out by performing a kinetic study using UV–Vis spectroscopy. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) techniques were used to investigate the morphology of the AuNPs that obtained after reducing the hydrogel.

Copolymer nanoparticles with pH-responsive properties were prepared by grafting different amounts of 2-(dimethylamine) ethyl methacrylate (DMAEMA) on carboxymethyl maize starch (CMS). The formation of CMS-g-DMAEMA was verified by different techniques and was then used for stabilization of Pickering emulsion at different pH values. The CMS-g-DMAEMA nanoparticles showed pH-responsive properties in Pickering emulsion and the pH-responsivity increased as the amount of DMAEMA increased in the CMS-g-DMAEMA copolymer. The prepared Pickering emulsion underwent emulsion/demulsification transitions at different pH values. The microscopy analysis verified the attachment of CMS-g-DMAEMA on oil-water interface of Pickering emulsion. Pickering emulsion showed different droplets size, contact angle, and Zeta-potential depend on pH value and CMS/DMAEMA ratio in the CMS-g-DMAEMA copolymer. The obtained results revealed that CMS-g-DMAEMA copolymer can be successfully used for preparing and stabilizing of Pickering emulsion at pH 10.

In this work, we report the synthesis, characterization and application of graphene oxide stabilized PdCo nanoparticles (PdCo GO) for the dehydrocoupling of dimethylamine borane (DMAB) as a model reaction. Bimetallic graphene oxide stabilized PdCo nano particles were readily synthesized using an ultrasonic reduction technique, in which both metals of Pd and Co were reduced with GO. The dispersion of PdCo nanoparticles on the surface of GO was enhanced with the help of the ultrasonic reduction method which result in the enhancing of dispersion of both metals without any agglomeration problem. The characterization studies revealed that graphene oxide stabilized PdCo nanoparticles have a uniform, homogeneous distribution on graphene oxide and an average particle size of 3.48 +/- 0.22 nm. After fully characterization of graphene oxide stabilized PdCo nano particles, they have been tried in model reaction as a catalyst and exhibited a high catalytic performance compared the previous catalysts in literature with a TOF value of 226.80 h(-1). The investigation of kinetic parameters showed that graphene oxide stabilized PdCo nanoparticles have very high negative entropy (Delta S: -170.85 J mol(-1) K-1) value and a low activation energy value (Ea: 17.53 +/- 2 kJ mol(-1) for the model reaction. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Carbon supported Pt-Co alloys are among the most promising electrocatalysts towards oxygen reduction reaction (ORR) for the application in low temperature fuel cells and beyond, thus their facile and green synthesis is highly demanded. Herein we initially report an alternate aqueous phase one-pot synthesis of such catalysts (containing nominally ca. 20 wt.% Pt) based on dimethylamine borane (DMAB) reduction. The as-obtained electrocatalyst (denoted as Pt3Co/C-DMAB) is compared with the ones obtained by NaBH4 and N2H4·H2O reduction (denoted as Pt3Co/C-NaBH4 and Pt3Co/C-N2H4·H2O, respectively) as well as a commercial Pt/C, in terms of the structure and electrocatalytic property. It turns out that Pt3Co/C-DMAB exhibits the highest ORR performance among all the tested samples in an O2-saturated 0.1 mol/L HClO4, with the mass activity (specific activity) ca. 4 (6) times as large as that for Pt/C. After 10000 cycles of the accelerated degradation test, the half-wave potential for ORR on Pt3Co/C-DMAB decreases only by 4 mV, in contrast to 24 mV for that on Pt/C. Pt3Co/C-NaBH4 or Pt3Co/C-N2H4·H2O shows a specific activity comparable to that for Pt3Co/C-DMAB, but a mass activity similar to that for Pt/C. ICP-AES, TEM, XRD and XPS characterizations indicate that Pt3Co nanoparticles are well-dispersed and alloyed with a mean particle size of ca. 3.4 plusmn; 0.4 nm, contributing to the prominent electrocatalytic performance of Pt3Co/C-DMAB. This simple aqueous synthetic route may provide an alternate opportunity for developing efficient practical electrocatalysts for ORR.

Ceria supported ruthenium nanoparticles (Ru0/CeO2) are synthesized by impregnation of Ru3+ ions on CeO2 powders followed by sodium borohydride reduction of Ru3+/CeO2. Their characterization was achieved using analytical methods including TEM, XRD, BET, SEM, and XPS. All the results reveal the formation of ruthenium(0) nanoparticles in 1.8 ± 0.3 nm size on CeO2 support. Ru0/CeO2 nanoparticles show high activity in catalyzing the H2 evolution from dimethylamine borane (DMAB). Ru0/CeO2 nanoparticles with 0.55% wt Ru provide the highest turnover frequency (812 h−1) for releasing H2 from DMAB at 60 °C and a total of 2500 turnovers before deactivation. High activity of Ru0/CeO2 nanoparticles for catalytic dehydrogenation of DMAB is attributable to the reducible nature of CeO2 support. Ce3+ defects formation in ceria under reducing conditions of dehydrogenation causes accumulation of negative charge on the oxide support, which makes oxide surface attractive for the ruthenium(0) nanoparticles. This, in turn, causes an enhancement in the metal-support interaction and thus in catalytic activity. The XPS analysis of bare ceria and Ru0/CeO2 demonstrates the increase in the concentration of Ce3+ defects after catalysis. Ru0/CeO2 nanoparticles are also reusable catalyst for H2 evolution from DMAB retaining 40% of initial activity after 4th run of reaction. The catalytic activity of Ru0/CeO2 nanoparticles and activation energy of catalytic dehydrogenation are compared with those of the other ruthenium based catalysts known in literature.

The effective coagulation aid epichlorohydrin-dimethylamine was synthesized, its co-effect with three ferric iron species in polyferric chloride on humic acid elimination and membrane pollution in coagulation-ultrafiltration hybrid technique were appraised to improve the hybrid water treatment technology and generate cleaner water production by this research. To be specific, dosages of polyferric chlorides 2 and polyferric chlorides&epichlorohydrin-dimethylamine were adjusted according to their coagulation performance in jar tests. Furthermore, properties of generated flocs such as floc size (median particle diameter), strength/recovery factor and fractal dimension feature were monitored and combined with results of membrane fouling resistance under various shear forces to understand the mechanism of membrane fouling. Results indicated that epichlorohydrin-dimethylamine can observably enhance the coagulation performance of all polyferric chlorides, especially at low dosage of 4 mg/L. The higher the epichlorohydrin-dimethylamine dosage, the higher removal efficiencies achieved. In particular, for polyferric chloride with basicity of 1.5, the removal efficiency for dissolved organic carbon raised approximately from 15% to 32% as epichlorohydrin-dimethylamine dosage increased from zero to 1.5 mg/L. Meanwhile, for ultra-membrane 3 applied in this study, addition of the epichlorohydrin-dimethylamine also significantly reduced the total membrane fouling resistance of all coagulated water samples by forming cake layer of low compactness and reducing residual micro-particles, 4 even when shearing forces was introduced. Thereinto, the total membrane fouling resistance reduction of polyferric chloride with basicity of 1.5 was the most obvious, which dropped from 2.8 × 108 m−1 to 2.3 × 108 m−1, approximately.

Palladium(II) 2,4-pentanedionate, impregnated on alumina nanopowder, was reduced by dimethylamine borane (DMAB) forming Pd(0) nanoparticles (NPs) at room temperature. Pd(0) NPs could be isolated from solution and characterized by ATR-IR, UV–vis, XRD, SEM, TEM, XPS and BET. The results obtained from TEM images reveal the formation of palladium(0) nanoparticles on gamma-alumina, having a mean particle size of 7.1 ± 2.6 nm. Alumina supported Pd(0) NPs with various metal loadings were employed as catalyst in dehydrogenation of DMAB at room temperature and the sample with 5.0% wt. Pd provides the highest turnover frequency (TOF = 73 h−1) at 25.0 ± 0.5 °C. Kinetics of the catalytic dehydrogenation was also investigated depending on Pd concentration and temperature to determine the kinetic parameters of the H2 release reaction.

Organic amines, including amine groups and carbon groups, are highly toxic chemicals with regard to both human health and ecosystems. However, the treatment of organic amines in wastewater remains a challenge using existing methods because of poisonousness of amines to microorganisms and simultaneous poor denitrification. In this work, we used a photoelectrochemical-chlorine radicals process to selectively and efficiently degrade organic amines into N2 and CO2. The proposed process was based on the reaction of organic amines with chlorine radicals (Cl ) and hydroxyl radicals (HO ) and a fast reduction reaction of nitrate-N on a porous Pd-Cu/porous nickel cathode (Pd-Cu/PN). For dimethylamine (DMA), this system achieved removal rates of 99.20% and 51.34% for total nitrogen (TN) and total organic carbon (TOC) within 2.5 h, respectively. Four main intermediate products, including methylamine (MA), ammonia (NH4+), nitrate (NO3−) and nitrite (NO2−), were observed, and no chlorohydrocarbon was detected. The analysis of electron-spin resonance (ESR) and a free-radical capture experiment confirmed that free radicals, especially Cl , played an important role in the denitrification of DMA. Trimethylamine (TMA), ethylamine (EA) and diethylamine (DEA) were also degraded to demonstrate the general applicability of this system, and the corresponding TN removal rates were 96.23%, 93.85% and 92.37%, respectively. This work provides a new, efficient, highly selective and environmentally friendly treatment method for removing organic amines from wastewater.

CO2 foam can be used for mobility control and blocking gas breakthrough channels during CO2 injection for enhanced oil recovery, and specially designed and formulated foam agents are needed to enhance the stability of the foams especially under reservoir conditions. In this study, the performance of CO2 foams with various surfactants has been investigated, including amide based surfactants (e.g. coconut monoethanol amide (CMEA), lauryl diethanol amide (LDEA)), amine based surfactants (cocoacyl propyl dimethylamine (UC11AMPM)), sodium dodecyl sulfate (SDS) and its mixtures with the amides and amines. A visualized high pressure and high temperature foam meter and a sand-pack flooding setup were used to assess the foam's performance, along with the surface tension measurement of the surfactant solutions in the presence of CO2. The influence of temperature, the surface tension of the aqueous solution, and SDS on CO2 foam performance of amide and amine based surfactant were investigated. The experimental results indicate that the amide or amine based surfactant alone all show poor foam performance, while their CO2 foam stability and their mobility control capability can be greatly enhanced at high temperature up to 100 °C with the salinity of 50000 mg/L. After adding SDS to CMEA, LDEA, or UC11AMPM, an excellent synergistic effect can be formed among the molecules, which can reduce the surface tensions of individual surfactant solution and enhance the stability of CO2 foams.

We report results of the studies relating to the fabrication of a surface plasmon resonance (SPR) based label-free immunosensor for real-time monitoring of endothelin-1 (ET-1), a colon cancer biomarker. A gold disk modified with a self-assembled monolayer (SAM) of 11-mercaptoundecanoic acid (11-MUA) was functionalised via covalent immobilization of monoclonal anti-ET-1 antibodies using EDC-NHS (1-(3-(dimethylamine)-propyl)-3-ethylcarbodiimide hydrochloride, N-hydroxy succinimide) chemistry. This immunosensing platform (ethanolamine/anti-ET-1/11-MUA/Au) was characterized via atomic force microscopy (AFM), contact angle (CA) and Fourier transform infrared (FT-IR) spectroscopic techniques. The fabricated SPR electrode was further used to detect ET-1 in the broad concentration range 2–100 pg mL−1, with a detection limit of 0.30 pg mL−1 and remarkable sensitivity of 2.18 mo pg−1mL. The adsorption mechanism was studied using monophasic model and the values of association (ka) and dissociation (kd) constants for anti-ET-1 and ET-1 binding were calculated to be 4.4 ± 0.4 × 105 M−1 s−1 and 2.04 ± 0.0003 × 10−3 s−1, respectively. The results obtained via analysis of serum samples of colorectal cancer patients were found to be in good agreement with those obtained from enzyme-linked immunosorbent assay (ELISA) technique. Further, electrochemical studies were performed to prove the efficacy of the fabricated platform as a point of care device for the detection of ET-1.

Herein, Palladium-Nickel alloy nanoparticles assembled on Vulcan carbon composites (PdNi@VC) have been reported as highly efficient, stable and durable catalyst for the hydrogen evolution from dimethylamine borane. Palladium-Nickel alloy nanoparticles assembled on Vulcan carbon composites were prepared using ultrasonic reduction technique and characterized using some analytical methods. The characterization analyses revealed that Palladium-Nickel alloy nanoparticles assembled on Vulcan carbon composites have a monodisperse metal distribution and crystalline structure. Some catalytic experiments were performed, and some activation parameters such as activation energy (Ea=40.05 +/- 2 kJ/mol), activation entropy (Delta S =-132.11 +/- 1 J mol(-1) K-1) and activation enthalpy (Delta H =37.55 +/- 1 kJ mol(-1)) were calculated for catalytic reaction of dimethylamine borane. The turnover frequency (TOF) value of Palladium-Nickel alloy nanoparticles assembled on Vulcan carbon composites was found to be 283.48 h(-1), having one of the best catalytic activities among the previous heterogenous catalysts tested for dimethylamine borane (DMAB) catalytic reaction. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Triphenylamine (TPA) compounds are versatile charge transport materials, demonstrating high emission efficiency and interesting interactions in solid state. Their spectroscopic emission parameters highly depend on surrounding medium owning to strong CT character in solution. Although TPA compounds demonstrate good charge transport capabilities, further optimization via molecular design is required. In this work, various TPA molecular systems with varying number of additional dimethylamine (dMA) and phenylethenyl (PE) substituents were thoroughly investigated. Additionally, influence of quaternarization of tertiary amine groups in the triphenylamine backbone on emission and electronic properties was analyzed. TPA-dMA compounds demonstrated aggregation induced emission enhancement with high emission efficiency and excellent (μh = 4.7·10−3 cm2V−1s−1) charge transport in the solid state. Quaternarization of tertiary amine groups in the triphenylamine backbone has led to emission and electronic properties in the wide 400–700 nm spectral region.

The structures, energetics, and infrared spectra of the cationic monomethylamine clusters (MMA)n+ were studied using quantum chemical calculations. The results reveal the preference of the formation of proton-transferred CH3NH3+-NH2CH2 ion-radical contact pair structure via the intermolecular proton transfer from the CH3 group to the nitrogen atom, which feature is different from the cationic dimethylamine and trimethylamine clusters reported recently. The CH3NH3+-CH2NH2 and CH3NH3+-NHCH3 ion-radical structures and the charge-shared (hemibonded) N N type (MMA)2+ ion core structure are predicted to be less energetically favorable. Simulated infrared spectra suggest that vibrational frequencies of the NH2 antisymmetric stretch of CH2NH2 radical would afford a sensitive probe for fundamental understanding of ion-radical networks generated from the radiation-induced chemical processes in the (MMA)n+ complexes.

Dimethylamine (DMA), which is mostly generated in fine chemical industry, has enormously threatened the public health, therefore should be eliminated from water efficiently. Superior to any other methods to remove DMA, adsorbing it by sorbent could avoid the generation of secondary pollution. Among all the sorbents employed in this study, low Si/Al ratio Beta zeolite synthesized without organic template exhibits the highest performance of adsorbing DMA from water. When the transition-metal cations were introduced by ion-exchange, the adsorption of DMA was enhanced. Subsequently, the saturated adsorbent was heated in air condition, detection results of the off-gas indicated that nearly all of the DMA adsorbed was oxidized and negligible harmful by-product was produced. Beta zeolite adsorption coupled with catalytic oxidation could eliminate DMA efficiently and environmental friendly which has wide application prospects in waterworks.

A series of 2,2′:6′,2″-terpyridine (terpy), 2,6-di(thiazol-2-yl)pyridine (dtpy), and 2,6-di(pyrazin-2-yl)pyridine (dppy) derivatives with electron donating amino groups (dimethylamine, piperidine, morpholine and diphenylamine) connected to the terpy/dtpy/dppy skeleton via phenylene linkage have been thoroughly investigated in order to get an insight into the impact of amine donors and nitrogen-based π-deficient heterocycles on the thermal, redox, UV–Vis absorption and emission properties. All the compounds melted without thermal decomposition and the presence of di(pyrazin-2-yl)pyridine skeleton increased the melting temperature and prevented formation of amorphous material. The obtained compounds undergo electrochemical reduction and oxidation processes and show electrochemically estimated Eg in the range of 2.30–2.83 eV. The lowest values of Eg were confirmed for the compounds bearing 2,6-di(pyrazin-2-yl)pyridine core and dimethylamine or piperidine substituents. Structure-dependent fluorescence properties of the synthesized compounds were evidenced in both solution and solid state. The use of 2,2′:6′,2″-terpyridine as acceptor unit gives opportunity to obtain more efficient emitters, while 2,6-di(pyrazin-2-yl)pyridine derivatives display the largest Stokes shifts. The dramatic decrease in the fluorescence quantum yield with the increasing polarity was attributed to ICT→TICT, while dual emission behavior was assigned to LE to ICT emissions. The effect of protonation and viscosity on the emission properties was also examined and it was found to be dependent on the nature of the acceptor moiety. Under external voltage the 2,6-di(pyrazin-2-yl)pyridine derivatives, except for dtpy with diphenylamine, did not exhibit light emission, contrary to the functionalized terpy and dppy.

Herein, we report a highly active Ru@PVP nanocatalyst for the hydrolytic dehydrogenation of dimethylamine-borane under room conditions. The Ru@PVP nanocatalyst was readily prepared, stabilized and used effectively in the catalytic dehydrogenation reaction of dimethylamine-borane in water at room conditions. The prepared Ru@PVP nanocatalyst was characterized using advanced analytical methods such as XPS, XRD, HR-TEM, etc. The characterization analyzes shown that Ru metals are uniformly distributed on the PVP support surface; the mean particle of catalyst size was found to be 2.78 +/- 0.16 nm. The catalytic test showed that DMAB had a high catalytic activity with Ru@PVP in aqueous solutions, and TOF value was found to be 2500.52 h(-1) for hydrolytic dehydrogenation of DMAB at room conditions. The study also included kinetic data such as activation parameters for different temperatures, catalyst concentration, and substrate concentration experiments. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Cationic polymers, which are commonly used as flocculants and coagulant aids in water and wastewater treatment, have been recently reported to promote the formation of nitrosamines. Most of the findings to date are based on poly (epichlorohydrin dimethylamine) and poly (diallyldimethylammonium chloride), while few studies have considered nitrosamines formation of polyacrylamides. In this work, the nitrosamines formation from non-ionic, anionic and cationic polyacrylamides was evaluated. Moreover, the effects of chemical structures of cationic polyacrylamides (including molecular weight, charge density, and monomers) on nitrosamines formation were investigated. The results revealed that the highest amount of nitrosamines formation was formed from cationic polyacrylamide, followed by non-ionic polyacrylamide and anionic polyacrylamide. Molecular weight and various cationic monomers showed no significant effects on nitrosamines formation, but monomers generated significantly higher amount of nitrosamines formation than cationic polyacrylamides. Nitrosamines formation increased with the increasing charge density of cationic polyacrylamides, and FTIR analysis results showed that the quaternary amine groups preferentially reacted with chloramines than with amide groups. This work shed new light on the nitrosamines formation from water and wastewater treatment polymers.

In order to controlling the yields of N-nitrosodimethylamine (NDMA), a highly human carcinogen, the competitive formation mechanism of NDMA and formaldehyde dimethylhydrazone (FDMH) from 1,1-dimethylhydrazine (UDMH) ozonation have been explored experimentally using gas chromatography-mass spectroscopy (GC–MS). Further, the results have been explained computationally using density functional theory (DFT) methods, as well as coupled cluster single-double (CCSD) methods, FDMH is not only an intermediate, but also a competitor for NDMA formation from UDMH. NDMA formation proceeds via H-abstraction from –NH2 moiety, while FDMH formation proceeds via H-abstraction from –CH3 moiety. The newly discovered NDMA formation mechanisms are: H-abstraction, diazene formation, O-addition. As ozone concentrations increases, the yields of NDMA rise accordingly. In addition, the theory results show that it is easier for NDMA to form from FDMH than that from UDMH. This study aims in providing a more detailed NDMA formation mechanism from UDMH than previous studies.

Stimuli responsive luminescent materials have attracted increasing attention for their potential application in many fields. In this work, dimethylamine substituted bisbenzocoumarins amides (DBCE and DBCP) are synthesized and their optical properties are investigated. These molecules show solvatochromic properties. The orange fluorescence emission of DBCE in crystalline state is blue-shifted to yellow emission upon grinding. The orange color could be recovered by recrystallization process. Powder wide-angle X-ray diffraction and DSC experiments reveal that the transformation from crystalline states to amorphous states under external stimuli is responsible for the mechanochromic properties. This work developed a new kind of binaphthane-type luminescent materials with blue-shifted mechanochromic properties.

Bacteremia is a serious problem of public health that is caused by bacteria in the blood and their components, in this way, total asepsis is a critic aspect in the different stages of transfusion medicine and in the use of biomedical devices in contact with tissues and blood. The aim of this study is to advance in the development of a new pathogen-inactivation technique by surface-contact based on the making of plasticized PVC bags with antibacterial properties. For that, films of PVC were chemically modified by nucleophilic substitution and quaternization of amino groups using dimethylamine and 1-bromoethane, respectively. Films were characterized by infrared spectroscopy, nuclear magnetic resonance, thermogravimetric analysis and elemental analysis; in addition, antibacterial properties against Gram-positive and Gram-negative bacteria (S. aureus and E. coli, respectively), hemolytic activity and surface adsorption of blood-components were evaluated. Results shown that cationic PVC, with ∼15% of quaternary ammonium groups, has antibacterial activity and hemolytic properties (hemolysis ∼7%), but also, affinity of blood-components with the surface was increased in comparison with PVC. Our results evidenced that cationic PVC can be obtained by the procedure performed, being a promissory alternative for the making of biomedical surface with capacity of pathogen-inactivation by in situ surface-contact.

Biofiltration has been shown to be effective for disinfection by-product (DBP) precursor control, however few studies have considered its role in the potential formation of DBPs. Biofilm is composed of heterogeneous bacteria as well as extracellular polymeric substances (EPS). The objective of this study was to determine the contribution of biofilm-related materials such as EPS to form nitrogen-containing DBPs upon chloramination, and to determine the influence of cyclical (scheduled on-off) biofilter operation on DBP precursor removal. Biologically active media was sampled from a full-scale biofilter operating under cold-water conditions (3.6 ± 0.5 °C) and extracted using a cation exchange resin into a phosphate buffer solution. Biomass concentrations, as determined using adenosine triphosphate (ATP) measurements, remained stable at 298 ± 55 ng ATP/g media over the trial period. N-nitrosodimethylamine (NDMA) and haloacetonitrile (HAN4) formation potential (FP) tests conducted under uniform formation conditions (UFC) using extracted biofilm yielded 0.80 ± 0.27 ng NDMA/g media and 18.7 ± 3.3 ng dichloroacetonitrile (DCAN)/g media. Further analyses of extracted biofilm using fluorescence spectroscopy and liquid chromatography-organic carbon detection indicated the presence of proteins above 20 kDa and humic-like substances. Extracted proteins (93.5 ± 8.1 μg/g media) correlated well (R = 0.90) with UV 280 measurements, indicating that spectrophotometry may serve as a valuable tool to quantify proteins in extracted biofilms. While substances in biofilms can serve as NDMA and DCAN precursors, the full-scale cyclically-operated biofilter that was examined did not show release of NDMA precursors during start-up following stagnation periods of 6 h or more. These biofilters consistently removed 6.9 ± 4.3 ng/L of NDMA precursors; typical NDMA UFC-FP of biofilter effluent was 8.5 ± 2.6 ng/L.

US EPA Method 521 employs activated carbon-based solid phase extraction (SPE) cartridges for analyzing N-nitrosamines. The analysis of N-nitrosamines and their chloramine-reactive and ozone-reactive precursors in nitrified municipal secondary effluent revealed the potential for NDMA to form as an artefact during the analysis. As samples passed through the SPE cartridge, the activated carbon mediated the reaction of nitrite with dimethylamine to form NDMA. The reaction was not significant with tertiary amines. Artefactual NDMA formation was important for nitrite concentrations >0.2 mg/L as N in the Biological Nitrogen Removal (BNR) process effluent. However, it is difficult to define a general threshold for nitrite concentrations, because the importance of the reaction also depends on secondary amine concentrations, which are usually poorly characterized. Pre-treatment of samples with sulfamic acid to destroy nitrite mitigated the artefact. This artefact did not affect NDMA analysis in a nitrified effluent from another facility, likely due to low dimethylamine concentrations. This artefact also did not affect the analysis of primary effluent, due to the lack of nitrite, or the analysis of other N-nitrosamines, likely due to the lack of their secondary amine precursors. Because chloramination does not significantly degrade nitrite, this artefact could affect the analysis of chloramine-reactive N-nitrosamine precursors. Because ozonation rapidly degrades nitrite, it should not affect the analysis of ozone-reactive precursors. However, ozonation at 0.8 mg ozone/mg dissolved organic carbon resulted in significant degradation of all N-nitrosamines, even though simultaneous NDMA formation from ozone-reactive precursors resulted in a net increase in NDMA concentration.

Pollutant release and transfer registers (PRTRs) compounds accidentally released to source waters can be important precursors of the carcinogenic N-nitrosodimethylamine (NDMA) during drinking water treatment. The NDMA formation potentials (NDMAFPs) of 31 anthropogenic nitrogenous compounds with dimethylamine (DMA) moiety on the Japanese PRTR and the registered precursors listed by the Ministry of Health, Labour and Welfare of Japan are investigated as well as influencing factors (i.e., NH2Cl dose and water matrices) on the NDMAFPs of precursors. Tertiary amines with aryl groups β-positioned to the nitrogen atom of the DMA moiety formed high concentrations of NDMA (35–51%) during chloramination. Moreover, dimethylcarbamoyl chloride (DMCCl) was considered a new NDMA precursor with NDMAFP of 1.1%, higher than DMA, a traditional NDMA precursor. Excessive NH2Cl dose enhanced the NDMA formation, and the NDMAFP of DMCCl significantly decreased in river water; the effect of the matrix in river water varied and was compound-specific. Among the selected nitrogenous compounds, NDMAFPs of 15 excessed the current guideline concentration for NDMA in Japan (100 ng/L) assuming an accidental release of 0.144 mg C/L (the concentration in previous Japanese water quality accident in May 2012), and 2-(dimethylaminomethyl) thiophene (DMAMT) showed the highest NDMAFP at 58 μg/L.

Summary 90Sr2+ remediation from acidic nuclear waste solution and contaminated seawater attracts great public attention but is very challenging because the removal performance toward soft Sr2+ by traditional oxidic ion-exchange materials are greatly affected by hard cations including H+, Na+, and Ca2+. We report a layered oxidic coordination polymer [(CH3)2NH2][ZrCH2(PO3)2F] (SZ-4) showing a notable advance over existing ion-exchange materials in 90Sr removal efficiencies with elevated distribution coefficients and record-high uptake capacities under acidic conditions. Moreover, the removal of Sr2+ is not significantly affected by the presence of a large excess of hard cations, leading to the successful cleanup of 90Sr-contaminated seawater samples. Such superior capabilities are directly visualized by well-refined single-crystal structures during in situ Sr2+ sorption process, revealing a distinctive two-step intercalation mechanism and a unique soft cation uptake selectivity achieved through collaborative coordination by the host layer and the interlayer dimethylamine (DMA) as a soft N-donor ligand.

In this study, we report a superior dehydrogenation catalyst for dimethylamine borane, which exhibited one of the best catalytic activities. The newly formed catalyst system contains well dispersed ruthenium-copper nanomaterials on reduced graphene oxide (3.86 ± 0.47 nm), which was prepared by using the ultrasonic double reduction technique. The characterization of monodisperse ruthenium-copper alloy nanoparticles was performed using some advanced analytical methods such as TEM, HRTEM, XPS, Raman spectroscopic analysis. The experiments results revealed that the monodisperse ruthenium-copper alloy catalyst (RuCu@rGO) has one of the highest catalytic activity compared to previous studies, having a high turnover frequency value (256.70 h−1). The detailed kinetic parameters such as activation energy, enthalpy, and entropy values were also calculated for the dehydrogenation of dimethylamine borane at room temperature. Also, the results showed that the monodisperse RuCu@rGO catalyst has high durability and reusability as retained its 81% initial catalytic activity even after 4th runs for the dehydrogenation of dimethylamine borane.

Microporous and hydrophobic polymers were synthesized and tested as NO oxidation catalysts to overcome water co-adsorption in combustion flue gas streams. The self-cross-linked 4,4′-bis(chloromethyl)-1,1′-biphenyl polymer (PBCMBP), with micropore volume of 0.38 cm3/g and surface area of 1430 m2/g, provided 62% NO oxidation efficiency at 25 °C in dry conditions but its performance dropped to 50% in the presence of 1.6 vol% moisture (wet conditions). To decrease performance loss, PBCMBP was modified with benzene (PBCMBP-BZ) to remove pendant chloromethyl groups, improving resistance to surface reactions with NO2 that add hydrophilicity. In wet conditions, PBCMBP-BZ has 59% NO oxidation efficiency, an 18% increase compared to PBCMBP at 25 °C. PBCMBP was also functionalized with dimethylamine (PBCMBP-DMA) to increase surface basicity, increasing NO oxidation by 11% in dry conditions, but decreasing NO oxidation in wet conditions by 30% due to increased proclivity to react with NO2. The combined impact of temperature and humidity was measured up to 100 °C, showing that moisture’s impact decreases with increasing temperature and that PBCMBP-DMA outperforms other catalysts at higher temperatures. Findings suggest that catalyst surface chemistry can be manipulated to further improve NO oxidation performance, especially in the presence of moisture.

Detection of ammonia and simple amine species such as methylamine (CH3NH2), dimethylamine ((CH3)2NH) and trimethylamine ((CH3)3N) is very important due to their industrial origin. This work details an evaluation on whether the fluorographene is a good candidate to sense the existence ammonia and simple amines for detection of fish spoilage? In order to achieve accurate data, the various interaction positions between the gaseous molecules, graphene and fluorographene sheets were studied. Furthermore, the electronic density of states (DOS plots) demonstrated that fluorographene sheet realizes the existence of NH3, CH3NH2, (CH3)2NH and (CH3)3N species with a more obvious signal (ΔEg = 0.036, 0.0308, 0.0499 and 0.0191 eV) compared to the graphene sheet (ΔEg = 0.0015, 0.0006, 0.0041 and 0.0022 eV). So, gained results demonstrates that the fluorographene can be applied as a bioelectronics nose in the various food spoilage sensors especially in detectors of the fish spoilage.

Three amine-modified Merrifield resins (AMMRs) were synthesized with ethane diamine, methylamine and dimethylamine to assess the impact of amine group on SO2 adsorption under low SO2 concentration. The dimethylamine-modified Merrifield resin (DMAMR) grafting with tertiary amine groups showed the greatest SO2 adsorption compared with ethane diamine-modified Merrifield resin (EDAMR) and methylamine-modified Merrifield resin (MAMR). Different amine groups had different reaction mechanisms with SO2. It was much easier for SO2 to form noncovalent charge transfer complex with tertiary amine group than the zwitterion and ion/counterion products with primary and secondary amine groups under dry condition. The noncovalent charge transfer complex had a relatively weaker thermostability than the zwitterion and ion/counterion products. As the temperature increased from 25 °C to 75 °C, the SO2 adsorption capacity on DMAMR decreased by 78.92%, which was much higher than that of EDAMR and MAMR (63.77% and 63.41% respectively). As SO2 concentration increased from 40 ppm to 100 ppm, significant increase (∼100%) in SO2 adsorption capacity was observed. Lower SO2 flow rate led to a more sufficient reaction between SO2 and amine groups, resulting the increase in SO2 adsorption capacities. Water vapor enhanced the SO2 adsorption performance of AMMRs significantly due to the formation of salt. However, it was more difficult for tertiary amine group to react with SO2 in the presence of water due to its relatively weaker basicity. DMAMR showed a greater regeneration performance than EDAMR and MAMR under dry and humid condition.

Sialylation is one of important glycosylation in human beings and plays an important role in cancer development. α2,3-Linked and α2,6-linked sialic acids are normally observed on the end of N-glycans and have different functions. Derivatization on sialic acid was designed to detect the different linkages by MALDI-TOF MS. In this study, a two-step derivatization by dimethylamine and ammonium hydroxide was improved to modify the sialic acid and made it easier to detect the different linkages of sialic acids on MALDI-TOF MS. Using this derivatization method, specific sialic acids linkages on N-glycans of protein samples such as fetuin and lactoferrin were detected. For complex cell samples, increased α2,3-linked and α2,6-linked sialic acids on bi-antennary and tri-antennary N-glycans were observed in A549 cells induced by hypoxia environment. Taken together, our two-step derivatization of sialic acids offers a simple and accurate way to detect specific linkages on N-glycans with MALDI-TOF mass spectrometer.

In this study, the effects of five different pre-oxidation scenarios (i.e., individual, simultaneous, and sequential applications of chlorine dioxide [ClO2] and chlorine [Cl2]) on the removal of N-nitrosodimethylamine (NDMA) formation potential (FP) from different water matrices (i.e., non-impacted natural waters, wastewater [WW]-impacted, and polymer-impacted waters) with subsequent chloramination were investigated. Practically relevant doses of ClO2 and Cl2 were applied for all scenarios to avoid the formation of disinfection by-products (DBPs) at regulatory levels. The removal efficiency of NDMA FP for all the oxidation scenarios (individual or simultaneous) was

Electroless deposition (also called chemical deposition) is a commonly used chemical approach to prepare metallic layers on various substrates. Cobalt films were deposited on the copper electrode using dimethylamine borane (DMAB) as a reducing agent and different amines: diethylenetriamine (dien), triethylenetetraamine (trien), propylenediamine (prop), tetraethylenepentaamine (ttren), pentaethylenehexaamine (pnten). The deposition conditions of electroless deposition of cobalt films were investigated in more detail by means of electrochemical quartz crystal microgravimetry (EQCM). The effects of pH, temperature and concentration of the reactants on the deposition rate of cobalt films have been determined. It was found that the induction period of the deposition of cobalt films depends on solution composition, temperature, and the presence of different amines.

In the growing area of wastewater reuse, the performance of reverse osmosis (RO) is limited by poor membrane selectivity towards nitrosamines and other low-molecular weight, neutral contaminants. This study aimed to increase RO membrane rejection of N-nitrosodimethylamine (NDMA), a carcinogenic nitrosamine that is produced during chlorination and chloramination of secondary wastewater effluent. Toward this goal, we modified commercial polyamide RO membranes with graphene oxide (GO) nanosheets, and demonstrated that GO functionalization can decrease the NDMA permeability coefficient by 31%, while only decreasing water permeability by 13%. The improved selectivity is likely due to additional steric exclusion derived from the GO nanosheet coating. Moreover, membrane characterization indicated that the GO modification does not change the hydrophilicity or roughness of the interface. The latter interfacial characteristics, combined with the well-established biocidal properties of graphenic nanomaterials, render GO functionalization a promising strategy for the development of highly selective membranes for wastewater reclamation.

Amides, a class of nitrogen-containing organic pollutants in the atmosphere, may affect the formation of atmospheric aerosols by the interactions with sulfuric acid. Here, the molecular interactions of sulfuric acid with formamide, methylformamide, dimethylformamide, acetamide, methylacetamide and dimethylacetamide was investigated by density functional theory. Geometry optimization and Gibbs free energy calculation were carried out at M06-2X/6-311++G(3df,3pd) level. The results indicate that the addition of amides to H2SO4 might have a promoting effect on atmospheric new particle formation at 298.15 K and 1 atm. In the initial stage of new particle formation, the binding capacity of amides and sulfuric acid is stronger than ammonia, but weaker than methylamine. It is worth noting that the trans-methylacetamide could have similar capabilities of stabilizing sulfuric acid as dimethylamine. In the presence of water, amides are found to only have a weak enhancement capability on new particle formation. In addition, we can infer from evaporation rate that the small molecule clusters of formamide and sulfuric acid may be more energetically favorable than macromolecule clusters.

This research article describes the solvents composition and structure effects on the depolymerization/extraction yield of a bituminous coal from the Naricual coalfield, located in Eastern Venezuela. Benzene, chloroform, N,N-dimethylformamide (DMF), 3-methylphenol (m-cresol), hexahydropyridine (piperidine) and toluene have been used as solvents; dimethylamine and p-phenylenediamine were used as additives (coal: amine 10:1 ratio), testing possible changes in yield in a Soxhlet extraction system in a 12 h lapse. The extraction/depolymerization capabilities were increased as follow: benzene

Amines play an important role in the formation and transformation of atmospheric aerosols. Gaseous phase and PM2.5 samples were collected simultaneously at Nanling Mountains, southern China during autumn 2016 and summer 2017. The site is strongly affected by long distance transport from marine and continental air masses. Five amines, methylamine (MA), dimethylamine (DMA), diethylamine (DEA), dibutylamine (DBA) and morpholine (MOR), were detected by gas chromatography-mass spectrometry (GC-MS) after derivatization. The backward trajectory analyses suggested that different origins of air masses led to seasonal variation of amines. In gaseous phase samples, the average concentrations of total measured amines (Ʃamines) were 193.4 ± 111.7 ng m−3 in autumn 2016 and 307.5 ± 196.7 ng m−3 in summer 2017. In PM2.5 samples, the average concentrations of Ʃamines were 12.4 ± 10.8 ng m−3 in autumn 2016 and 20.7 ± 11.0 ng m−3 in summer 2017. MA and DMA were the dominant amines, together contributing approximately 70% to gaseous amines and 80% to particulate amines. A strong linear relationship was found between Ʃamines and NO3− in PM2.5, implying that amines might mainly exist in the form of aminium nitrate. Ammonium (NH4+) was found mostly likely in the form of ammonia sulfate. Approximately 7.4% of the gaseous total amines partitioned to PM2.5. A good linear relationship between the fraction of total atmospheric concentration sorbed by PM2.5 (Φ) and the concentrations of O3 was found, suggesting that O3 likely played an important factor in the gas-to-particle partitioning of amines. Additionally, under high relative humidity circumstances (92% ± 7.0%), direct dissolution was a crucial step for gaseous amines partitioning into particles. The ratios of amines-C to water-soluble organic carbon (WSOC) and amines-N to water-soluble organic nitrogen (WSON) were 0.21% and 1.57% in autumn 2016 and 0.54% and 2.08% in summer 2017, respectively. The results of this study provide essential information on the formation mechanism of particulate amines.

Catalytic liquid-phase hydrogenation of N-nitrosodimethylamine (NDMA) over CeO2, TiO2 and CeO2-TiO2 (CexTi, x referred to the molar ratio of Ce to Ti) supported Pd-Ni bimetallic catalysts (Pd-Ni/CexTi) was investigated. Characterization results indicated that Ce-O-Ti solid solutions formed through the incorporation of Ti4+ into the CeO2 lattice, resulting in increased specific surface areas and reduced average crystal sizes of CexTi. Ti doping also promoted the generation of oxygen vacancies (Ov) on the surface of CexTi. For Pd-Ni/CexTi, the amount of oxygen vacancies first increased and then decreased with the increasing of Ti content, and the maximum content of Ov was observed on Pd-Ni/Ce4Ti. Consequently, Pd-Ni/Ce4Ti had the smallest metal particle sizes, due to the strong metal-support interaction formed between Pd-Ni and Ov. Pd-Ni/CexTi exhibited much higher catalytic activities than that of Pd/CeO2 and Pd/TiO2 for NDMA reduction, and the Pd-Ni/Ce4Ti had the highest activity. The catalytic activity of Pd-Ni/CexTi was relevant to the oxygen vacancies on the support, which influenced the metal dispersion and the adsorption of intermediate product of NDMA reduction.

N -nitrosodimethylamine (NDMA) contamination in several drugs has been reported since 2018, and there is also a potential risk of the NDMA contamination in various other drug substances and their pharmaceutical products. To quantitate NDMA in various drugs having diverse physicochemical properties, a specific, sensitive and durable analytical method is required, in addition to methods that can be applied to a class of nitrosamines. We aimed to develop an off-line isolation method for NDMA in drug substances using solid-phase extraction (SPE) for quantification using high-performance liquid chromatography (HPLC)–atmospheric pressure chemical ionization (APCI)–tandem mass spectrometry (MS/MS).Impediments to accurate quantitation of NDMA in drug substances using LC–MS/MS and insufficient durability of the system is due to the extremely large amounts (≈ 10 8 times) of active pharmaceutical ingredients (APIs) in sample solutions in comparison to the trace amount of NDMA. It is occasionally possible to encounter a reduced retention of NDMA and/or decreased separation from other substances in LC, matrix effect in MS detection, and undesirable contamination of instruments with API and other substances, which consequently results in deterioration of system performance and generation of unreliable data even in the cases where divert valve is configured between the column and ion source of the MS instrument.To address the problems, an off-line isolation methodology for NDMA from APIs having diverse physicochemical properties, namely ranitidine hydrochloride (ranitidine), metformin hydrochloride (metformin), nizatidine, valsartan, and telmisartan , was developed. The applicability of the method was confirmed by batch analysis of metformin and ranitidine. Furthermore, contrary to previous reports, NDMA was found to be stable over a wide pH range. The methodology and information would contribute the control of NDMA concentration in various drugs to realize the safe delivery of pharmaceuticals to patients.

Water reclamation using reverse osmosis (RO) has become an indispensable component of the urban water supply system. However, the removal of low molecular weight contaminants of emerging concerns such as N-Nitrosodimethylamine (NDMA) from RO is challenging, thereby raising serious safety concerns about reclaimed water. Herein we modify RO membrane with graphene oxide (GO) using polydopamine (PDA) as crosslinking agent. The modification of commercial RO membrane via co-deposition of PDA-GO subsequently resulted in superior NDMA rejection (83 ± 3.57%) when compared with the membranes modified via GO, PDA, GO on PDA impregnated surface, and pristine RO. The narrow interlayer spacing of the GO (0.36 nm), attributed to its partial reduction occurred due to thin PDA layer formation on its both sides, exhibited enhanced sieving effect in addition to the coverage of free–volume hole-size of the polyamide layers which offered hindrance to NDMA permeation. In addition, CFU-enumeration and confocal laser scanning microscopy revealed that the partial reduction of GO did not significantly affect its associated antibacterial property when compared with the membrane modified via GO after PDA impregnation. However, enhanced antibiofouling performance was observed using optical coherence tomography (OCT) employed in this study for in-situ, real-time, and non-destructive fouling monitoring with better flux performance.

Halonitromethanes (HNMs) is a typical class of nitrogenous disinfection byproducts with high toxicity. The effect of Br− on the formation and transformation of HNMs from dimethylamine (DMA) during the ultraviolet (UV)/chlorine disinfection has been investigated in current study. Results reveal that only chloronitromethane, dichloronitromethane and trichloronitromethane (TCNM) could be found during the UV/chlorine disinfection. Whereas in the presence of Br−, nine species of HNMs could be observed simultaneously. When Br− concentration increased from 0 to 15.0 mg L−1, the predominant species of HNMs were gradually changed from TCNM to dibromonitromethane and tribromonitromethane, which contributed to 23.37% and 31.07% of total HNMs concentration at 15 mg L−1 Br−, respectively. The presence of Br− not only shifted the chlorinated-HNMs (Cl-HNMs) towards brominated-HNMs (Br-HNMs) but also affected the dominant species and total concentration of HNMs. When Br− concentration was 4.0 mg L−1, the formation of HNMs decreased with the increase of pH from 6.0 to 8.0 and increased with the increase of free chlorine and DMA. When free chlorine concentration rose from 0.25 to 1.1 mmol L−1, Br-HNMs were shifted to Br(Cl)-HNMs and then to Cl-HNMs. According to the findings, possible formation and transformation pathways of HNMs from DMA were proposed in the presence of Br− during the UV/chlorine disinfection. Finally, it was proved that the effect of Br− on the trend of HNMs in real water was similar to that in deionized water, but higher HNMs concentrations and delayed peak time were observed in real water. This study can provide the scientific evidence and fundamental data for the applications of UV/chlorine disinfection in the treatment of water containing Br−.

N-nitrosamines (NAs), a class of emerging nitrogenous disinfection byproducts, have been detected remarkably in drinking/reclaimed water. There is a significant risk of excessive levels of NAs in the chlorination of the polluted source water, especially in the direct chlorination of nitrite-enriched groundwater. Considering the co-pollution of nitrite and micro-organic pollutants on groundwater, experiments were conducted on chlorination of nitrite-enriched water with precursor of antibiotics, and it was confirmed that the Cl 2 : N (molar ratio of chlorine to nitrite), contacting time, pH, and DO appreciably influenced the NAs formation potential. The molecular electric potential revealed that different dissociation status of precursors has a specific correlation with NAs formation potential (FP). The nitrite significantly increased the NAs FP because the reactive nitrogen species (RNS) formed in the oxidation process from nitrite to nitrate. Sequences of transformation products are determined to support the RNS promoted hypothesis of N-nitrosodimethylamine (NDMA) formation mechanism; furthermore, theoretical investigation in the reaction of dimethylamine (DMA) with different RNS verified the above hypothesis.