Showing papers on "Ammonium hydroxide published in 2014"

Mechanistic analysis of ammonium cation stability for alkaline exchange membrane fuel cells

Abstract: Improving long-term cation stability is crucial for adopting anion exchange membrane fuel cells as a commercially viable technology in clean energy conversion applications. To reliably identify the most stable cation structures, we analyzed the cation stability of various synthetically prepared quaternary ammonium organic molecules via a silver oxide ion exchange reaction. This method enabled us to compare the stability of various structures of quaternary ammonium hydroxide in pure form in water without excess alkaline solution or inconsistencies faced in the presence of polymer backbones. By quantitatively comparing cation degradation via NMR, we were able to identify three cation structures with greater cation stability than the most well-known benzyltrimethylammonium. In addition, we were able to elucidate byproduct formation and degradation mechanisms as a result of hydroxide attack. From this study we concluded that alkyl-substituted cations seem to impart greater stability than benzylic-substituted cations in the presence of hydroxide anions in aqueous solution.

Graphene oxide–aluminium oxyhydroxide interaction and its application for the effective adsorption of fluoride

Abstract: A novel aluminium oxy hydroxide [Al–O(OH)] modified graphene oxide was prepared by a chemical precipitation method wherein Al3+ ions could interact effectively with the different functional groups of graphene oxide (GO). The prepared (GO–Al–O(OH) adsorbent was tested for the effective defluoridation of water. The Al3+ modified graphene oxide adsorbent was characterized using FT-IR, FT-Raman, SEM-EDS, XRD and XPS studies. The thermodynamically feasible adsorption is supported by the pseudo second order kinetics and a high Langmuir maximum adsorption capacity (51.42 mg g−1) for the GO–Al–O(OH) adsorbent. Furthermore, we could treat 2.0 L of 5.0 mg L−1 fluoride ion solution to bring the level within the permissible limits and the regeneration of the adsorbent was done using ammonium hydroxide.

Unexpected effects of the alteration of structure and stability of myoglobin and hemoglobin in ammonium-based ionic liquids

Abstract: The nature of solvent-biomolecule interactions is generally weak and non-specific. The addition of ionic liquids (ILs), which have emerged as a new class of solvents, strengthen the stability of some proteins whereas the same ILs weaken the stability of some other proteins. Although ILs are commonly used for the stabilization of biomolecules, the bimolecular interactions of their stabilization-destabilization is still an active subject of considerable interest and studies on this topic have been limited. To reveal the impact of ILs on the stability of proteins, a series of protic ILs possessing a tetra-alkyl ammonium cation [R4N](+) with a hydroxide [OH](-) anion were synthesized. In this study, we report the structural stability of heme proteins such as myoglobin (Mb) and hemoglobin (Hb) in a series of ammonium-based ILs such as tetramethyl ammonium hydroxide [(CH3)4N](+)[OH](-) (TMAH), tetraethyl ammonium hydroxide [(C2H5)4N](+)[OH](-) (TEAH), tetrapropyl ammonium hydroxide [(C3H7)4N](+)[OH](-) (TPAH) and tetrabutyl ammonium hydroxide [(C4H9)4N](+)[OH](-) (TBAH) by fluorescence and circular dichroism (CD) spectroscopic studies. Our experimental results reveal that less viscous ILs carrying smaller alkyl chain such as TMAH are strong destabilizers of the heme proteins as compared to the ILs carrying bulkier alkyl chains which are more viscous ILs, such as TBAH. Therefore, our results demonstrate that the addition of these ILs to the heme proteins decreases their thermal stability allowing the protein to be in an unfolded state at lower temperatures. Further, we describe the molecular-structural interaction of the heme proteins with the ILs (molecule like a ligand) by the PatchDocking method.

Microemulsion-Assisted Synthesis of Mesoporous Aluminum Oxyhydroxide Nanoflakes for Efficient Removal of Gaseous Formaldehyde

Abstract: Mesoporous aluminum oxyhydroxides composed of nanoflakes were prepared via a water-in-oil microemulsion-assisted hydrothermal process at 50 °C using aluminum salts as precursors and ammonium hydroxide as a precipitating agent The microstructure, morphology, and textural properties of the as-prepared materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption, and X-ray photoelectron spectroscopy (XPS) techniques It is shown that the aluminum oxyhydroxide nanostructures studied are effective adsorbents for removal of formaldehyde (HCHO) at ambient temperature, due to the abundance of surface hydroxyl groups, large specific surface area, and suitable pore size Also, the type of aluminum precursor was essential for the microstructure formation and adsorption performance of the resulting materials Namely, the sample prepared from aluminum sulfate (Al-s) exhibited a relatively high HCHO adsorption capacity in the first run, while the samples obtained from aluminum nitrate (Al-n) and chloride (Al-c) exhibited high adsorption capacity and relatively stable recyclability A combination of high surface area and strong surface affinity of the prepared aluminum oxyhydroxide make this material a promising HCHO adsorbent for indoor air purification

Ammonium Addition (and Aerosol pH) Has a Dramatic Impact on the Volatility and Yield of Glyoxal Secondary Organic Aerosol

Abstract: Glyoxal is an important precursor to secondary organic aerosol (SOA) formed through aqueous chemistry in clouds, fogs, and wet aerosols, yet the gas-particle partitioning of the resulting mixture is not well understood. This work characterizes the volatility behavior of the glyoxal precursor/product mix formed after aqueous hydroxyl radical oxidation and droplet evaporation under cloud-relevant conditions for 10 min, thus aiding the prediction of SOA via this pathway (SOACld). This work uses kinetic modeling for droplet composition, droplet evaporation experiments and temperature-programmed desorption aerosol-chemical ionization mass spectrometer analysis of gas-particle partitioning. An effective vapor pressure (p'L,eff) of ∼10(-7) atm and an enthalpy of vaporization (ΔHvap,eff) of ∼70 kJ/mol were estimated for this mixture. These estimates are similar to those of oxalic acid, which is a major product. Addition of ammonium until the pH reached 7 (with ammonium hydroxide) reduced the p'L,eff to 80 kJ/mol, at least in part via the formation of ammonium oxalate. pH 7 samples behaved like ammonium oxalate, which has a vapor pressure of ∼10(-11) atm. We conclude that ammonium addition has a large effect on the gas-particle partitioning of the mixture, substantially enhancing the yield of SOACld from glyoxal.

Effect of Caustic Type on Bitumen Extraction from Canadian Oil Sands

Abstract: The role of different types of caustics in bitumen extraction from Canadian oil sands is investigated by analyzing their effect on subprocesses involved in bitumen extraction. Both sodium hydroxide and ammonium hydroxide were shown to improve bitumen liberation, which is favorable for bitumen recovery, but increased induction time of bitumen–bubble attachment, which is harmful for bitumen recovery. Although a similar performance was observed at pH of ∼8.5, at pH 11.3, the use of ammonium hydroxide led to a shorter induction time of bitumen–bubble attachment and, hence, better bitumen recovery than the use of sodium hydroxide to achieve the same slurry pH. The better performance of ammonium hydroxide is attributed to a more hydrophobic surface and a less negative zeta potential of bitumen in the process water because of the release of less amount of natural surfactants in ammonium hydroxide solutions than in sodium hydroxide solutions of the same solution pH. Overall, ammonium hydroxide was found to be a s...

Synergistic effect of quaternary ammonium hydroxide and crown ether on the rapid and clear dissolution of cellulose at room temperature

Abstract: The simultaneous addition of 40% tetrabutylammonium hydroxide (TBAH) and crown ether (18-crown-6) promptly produced a clear aqueous solution of cellulose (10 wt%) at room temperature.

Preparation method of super-hydrophobic cellulose material with micro-nano structure

Abstract: The invention relates to a preparation method of a super-hydrophobic cellulose material with a micro-nano structure. The method comprises the following steps: (1) adding ethyl orthosilicate and functionalized siloxane into an ethanol system containing deionized water to obtain a dispersion liquid of functionalized silica particles A in the presence of ammonium hydroxide serving as a catalyst; with the dispersion liquid of functionalized silica particles A as seeds, sequentially adding the ethyl orthosilicate, the functionalized siloxane, the deionized water, the ammonium hydroxide and the ethanol so as to obtain a dispersion liquid of functionalized silica particles B; (2) performing ultrasonic dispersion on the two types of functionalized silica particles in dimethylformamide, then adding a hydrophobic polymer and a low surface energy additive into the system and evenly stirring so as to form white dispersion liquid; and (3) coating the white dispersion liquid obtained in the step (2) on a natural cellulose material in a direct spraying manner or a spin coating manner so as to obtain the super-hydrophobic cellulose material with the micro-nano structure. The coating material has strong scouring resistance and acid-alkali resistance besides the excellent hydrophobic property.

Insights into the Transport of Aqueous Quaternary Ammonium Cations: A Combined Experimental and Computational Study

Abstract: This study focuses on understanding the relative effects of ammonium substituent groups (we primarily consider tetramethylammonium, benzyltrimethylammonium, and tetraethylammonium cations) and anion species (OH(-), HCO3(-), CO3(2-), Cl(-), and F(-)) on ion transport by combining experimental and computational approaches. We characterize transport experimentally using ionic conductivity and self-diffusion coefficients measured from NMR. These experimental results are interpreted using simulation methods to describe the transport of these cations and anions considering the effects of the counterion. It is particularly noteworthy that we directly probe cation and anion diffusion with pulsed gradient stimulated echo NMR and molecular dynamics simulations, corroborating these methods and providing a direct link between atomic-resolution simulations and macroscale experiments. By pairing diffusion measurements and simulations with residence times, we were able to understand the interplay between short-time and long-time dynamics with ionic conductivity. With experiment, we determined that solutions of benzyltrimethylammonium hydroxide have the highest ionic conductivity (0.26 S/cm at 65 °C), which appears to be due to differences for the ions in long-time diffusion and short-time water caging. We also examined the effect of CO2 on ionic conductivity in ammonium hydroxide solutions. CO2 readily reacts with OH(-) to form HCO(-)3 and is found to lower the solution ionic conductivity by almost 50%.

Highly Active and Stable Ni−SiO2 Prepared by a Complex- Decomposition Method for Pressurized Carbon Dioxide Reforming of Methane

Abstract: A series of Ni–SiO2 catalysts was synthesized by the complex-decomposition method using different amino acids as complexing agents and fuels and nickel nitrate and tetraethoxysilane as precursors of Ni and SiO2, respectively. For comparison, ammonium hydroxide and acetic acid were also used as complexing agents and fuels. Characterization by XRD, TEM, and N2 adsorption–desorption at low temperature indicated that the structural and textural properties of the Ni–SiO2 catalysts were strongly dependent on the complexing agent used. The dispersion of metallic Ni was increased by optimizing the complexing agent used. As revealed from H2-TPR patterns, Ni–SiO2 exhibited significantly different interactions between Ni and SiO2, the extent of which was influenced by the complexing agent used. The Ni–SiO2 catalysts were comparatively evaluated for carbon dioxide reforming of methane (CDR) under the following conditions: CH4/CO2 = 1.0, T = 750 °C, GHSV = 53200 mL·g–1·h–1, and P = 1.0 atm. The results indicate that t...

Properties of magnetic nanoparticles prepared by co-precipitation.

Abstract: Magnetic nanoparticles were synthesized by the addition of ammonium hydroxide to an iron chloride solution by chemical co-precipitation. In order to examine systematically the crystal phase, average size, and magnetic properties of the magnetic nanoparticles, the following were used as experimental parameters: molar ratio of Fe2+/Fe3+, composition of the iron chloride solution, amount of ammonium hydroxide, reaction temperature, and oxidation time of reaction precipitate. In the processing conditions of Fe2+/Fe3+ ratios of 0.5 and 1.0, iron chloride solutions of 0.1-0.8 m, NH4OH molar ratios of 6-14R, reaction temperatures of 25-80 degrees C, and oxidation times of 5-90 min, the co-precipitated nanoparticles were observed to exist as a single phase of Fe3O4. The average size of the particles was approximately 20 nm, and their magnetization was saturated at about 60 emu/g with superparamagnetism. When the iron chloride solution comprised only Fe2+ ions, the oxidation of the reaction precipitates also developed a Fe3O4 phase. However, the particle size reached 78 nm with increasing oxidation times, and the saturation magnetization increased significantly to 82 emu/g while its coercive force was 150 Oe, which indicated that the nanoparticles were paramagnetic.

Characterization, dielectric and electrical behaviour of BaTiO3 nanoparticles prepared via titanium(IV) triethanolaminato isopropoxide and hydrated barium hydroxide

Abstract: A new sol-precipitation technique for the preparation of nano BaTiO3 crystallite has been developed by reacting 0·2 M each of Ti(IV) triethanolaminato isopropoxide and hydrated barium hydroxide in methanol such that the molar ratio of Ba : Ti is 1·02 at 80 °C under stirring (1200 rpm) for one hour in alkaline media using tetra methyl ammonium hydroxide (TMAH). It was calcined at 100 °C for 12 h. Structural and compositional properties were investigated by XRD, SEM, EDX, TEM, SAED and DLS techniques. FT–IR and TG–DTA were used to characterize its purity and the thermal stability. The BaTiO3 particles prepared were found to be spherical, homogeneous and cubic in structure. The particle size was found to be 23–31 nm. The dielectric constant and dissipation factor after sintering at 400 °C were 5379 and 0·63, respectively at 100 Hz frequency. The a.c. conductivity (σ a.c.) was found to be 2 × 10–5 S-cm–1 at room temperature (30 °C). It increased with increasing temperature up to 50 °C and decreased with further increase in temperature. The impedance was 3·37 × 105 ohms at room temperature. It decreased with increasing frequency.

Field Dissipation and Storage Stability of Glufosinate Ammonium and Its Metabolites in Soil

Abstract: A simple analytical method was developed to measure concentrations of glufosinate ammonium and its metabolites, 3-methylphosphinico-propionic acid (MPP) and 2-methylphosphinico-acetic acid (MPA), in field soil samples. To determine the minimum quantification limit, samples were spiked at different levels (0.1, 0.5, and 1.0 mg/kg). Soil samples were extracted with ammonium hydroxide solution 5% (v/v), concentrated, and reacted with trimethyl orthoacetate (TMOA) in the presence of acetic acid for derivatization. The derivatives were quantified by gas chromatography (GC) using a flame photometric detector (FPD). The linear correlation coefficients of glufosinate ammonium, MPP, and MPA in soil were 0.991, 0.999, and 0.999, respectively. The recoveries of this method for glufosinate ammonium, MPP, and MPA in soil were 77.2–95.5%, 98.3–100.3%, and 99.3–99.6% with relative standard deviations (RSD) of 1.8–4.1%, 0.4–1.4%, and 1.3–2.0%, respectively. Glufosinate ammonium dissipated rapidly in soil to MPA in hours and gradually degraded to MPP. The half-life of glufosinate ammonium degradation in soil was 2.30–2.93 days in an open field. In soil samples stored at −20°C glufosinate ammonium was stable for two months. The results of this study should provide guidance for the safe application of the herbicide glufosinate ammonium to agricultural products and the environment.

Zinc oxide porous nano-cages fabricated by laser ablation of Zn in ammonium hydroxide.

Abstract: We report the successful synthesis of ZnO porous nano-cages with controllable hollow spaces by simply using laser ablation of Zn target in liquid medium containing deionized water and ammonia (Vwater:Vammonia = 7:1~5:1). In addition to the porous surface, the created interior space of the ZnO nano-cage substantially increases with the ammonia concentration. The related growth mechanism has been illustrated based on the ultra-rapid alkaline etching process. Moreover, numerous Zn(NH3)42+ clusters generated by the selective etching route readily penetrate into the ZnO porous structures and can be embedded in these unique nano-cages. It is envisaged that these composite ions/ ZnO porous nano-cages have significant implications for gas sensing and catalytic applications. The synthetic scheme used here should also be applicable to other semiconductors.

Preparation method of carbon-coated doping-modification ternary composite cathode material for lithium ion battery

Abstract: The invention discloses a preparation method of a carbon-coated doping-modification ternary composite cathode material for a lithium ion battery. According to the method, a compound containing Li, Ni, Co and Mn and a metal doped compound are dissolved in water respectively in a stoichiometric ratio; an organic acid is added, pH of the solution is regulated by ammonium hydroxide, and the solution is stirred continuously to obtain a homogeneous and transparent solution; then the solution is placed on an electric furnace, heated with the furnace until the solution evaporates and boils to a critical point, and spontaneously combusts quickly; and powder obtained after the combustion is subjected to heat treatment for 6-14 hours at the temperature of 600-950 DEG C, and the carbon-coated doping-modification ternary LiNixCo(y-a)Mn(1-x-y)MaO2 composite cathode material is obtained. Two methods are adopted for carbon coating, a carbon source is introduced during a sample synthesizing process or the heat treatment process, the surface of the ternary material can be uniformly coated with the carbon layer, synthesis of the ternary material and carbon coating are finished by one step quickly and simply with a self-propagating combustion method, an obtained product is low in cost, uniform in particle and stable in electrochemical performance, and industrial production is facilitated.

Synthesis of quaternary ammonium hydroxide from its halide salt by bipolar membrane electrodialysis (BMED): effect of molecular structure of ammonium compounds on the process performance

Abstract: BACKGROUND Conventional methods for synthesis of quaternary ammonium hydroxides, such as the reaction of quaternary ammonium chloride, ion-exchange and electro-electrodialysis cannot achieve benign production of QAOH without secondary pollution. The objective of the present study was to develop bipolar membrane electrodialysis with a novel stack configuration as an improved method to prepare high purity quaternary ammonium hydroxide from its halide salt. RESULTS To investigate the synthesis of quaternary ammonium hydroxide (QAOH) with high purity by using electrodialysis with bipolar membranes (BMED), four different types of quaternary ammonium hydroxides (tetramethylammonium hydroxide, TMAOH; tetrapropylammonium hydroxide, TPAOH; methyltriethylammonium hydroxide, MTAOH; and benzyltrimethylammonium hydroxide, BTAOH) were chosen as the target products. The effect of the molecular structure of four different types of halide salts (NR4X) on the BMED performance was studied by investigating operating parameters such as current density, feed concentration and feed flow velocity and energy consumption on the basis of ion dimensions and molecular weight, ion electrophoretic mobility and the interaction between ammoniums and membranes. The results indicate that it is feasible to obtain quaternary ammonium hydroxides with high purity (Cl−/Br− content < 500 ppm) by BMED with a novel four-compartment configuration in view of environmental aspects. CONCLUSION For converting higher molecule size halide salts, the process performance was lower, while the energy consumption increased, at similar experimental conditions, which is in line with the theory. © 2014 Society of Chemical Industry.

Niobium Peroxide‐Catalyzed Selective Epoxidation of Allylic Alcohols

Abstract: Modified niobium peroxides were prepared and used for catalyzing the epoxidation of allylic alcohols with hydrogen peroxide in the absence of any other solvent under ice bath conditions. Niobium peroxides modified with ionic liquid-type 1-dodecyl-3-methylimidazolium hydroxide or conventional tetradecyl trimethyl ammonium hydroxide surfactants demonstrated excellent yields (80–99 %) for the epoxidation of allylic alcohols to their epoxides even if the reaction was performed without any other solvent at 0 °C for 0.5 h. The catalyst characterization demonstrated that the surfactant molecules were anchored on the surface of the niobium catalyst by weak noncovalent interactions. Compared with niobium peroxides, the modified amphiphilic catalysts allowed easier accessibility to hydrophobic substrates and thus demonstrated high reaction rate and excellent recyclability for the epoxidation under mild conditions.