Showing papers on "Ammonia published in 2010"
TL;DR: Maintaining appropriate levels of alkalinity, Mg, aeration along with optimal an initial NH(4)(+)/cell ratio were all necessary for long-term semi-continuous ammonium removal and cell growth.
324 citations
TL;DR: In this paper, composites of the metal-organic framework (MOF), MOF-5, and graphite oxide (GO) with different ratios of the two components are prepared and tested in ammonia removal under dry conditions.
Abstract: Composites of the metal-organic framework (MOF), MOF-5, and graphite oxide (GO) with different ratios of the two components are prepared and tested in ammonia removal under dry conditions. The parent and composite materials are characterized before and after exposure to ammonia by sorption of N2, X-ray diffraction, thermal analyses, and FT-IR spectroscopy. The results show a synergetic effect resulting in an increase in the ammonia uptake compared to the parent materials. It is linked to enhanced dispersive forces in the pore space of the composites. Additionally, ammonia interacts with zinc oxide tetrahedra via hydrogen bonding and is intercalated between the layers of GO. Retention of a large quantity of ammonia eventually leads to a collapse of the MOF-5 structure in the composites. The effect resembles that observed when MOF-5 is exposed to water. Taking into account the similarity of ammonia and water molecules, it is hypothesized that ammonia causes a destruction of the MOF-5 and composite structure as a result of its hydrogen bonding with the zinc oxide clusters.
302 citations
TL;DR: A series of W-doped CeO2/TiO2 catalysts prepared by different impregnation methods assisted with ultrasonic energy were investigated for the selective catalytic reduction (SCR) of NOx (NO and NO2) by NH3 as mentioned in this paper.
297 citations
TL;DR: Compared with the conventional pretreatment, the combined method for lignocellulosic biomass pretreatment was an economical and eco-friendly and showed over 90% of the glucose conversion even with a reduced enzyme usage and incubation time.
265 citations
TL;DR: In this article, the authors studied the hydration of sulfuric acid and dimethylamine-containing two-acid clusters using quantum chemistry, and showed that the addition of a dimethyl acid molecule to the clusters improves the hydrate distribution.
Abstract: . We have studied the hydration of sulfuric acid – ammonia and sulfuric acid – dimethylamine clusters using quantum chemistry. We calculated the formation energies and thermodynamics for clusters of one ammonia or one dimethylamine molecule together with 1–2 sulfuric acid and 0–5 water molecules. The results indicate that dimethylamine enhances the addition of sulfuric acid to the clusters much more efficiently than ammonia when the number of water molecules in the cluster is either zero, or greater than two. Further hydrate distribution calculations reveal that practically all dimethylamine-containing two-acid clusters will remain unhydrated in tropospherically relevant circumstances, thus strongly suggesting that dimethylamine assists atmospheric sulfuric acid nucleation much more effectively than ammonia.
243 citations
TL;DR: The hypothesis of nanoconfinement and metallic catalysis was tested and found to be effective for enhancing the hydrogen release kinetics and preventing the formation of ammonia.
Abstract: A system involving ammonia borane (AB) confined in a metal−organic framework (JUC-32-Y) was synthesized. The hypothesis of nanoconfinement and metallic catalysis was tested and found to be effective for enhancing the hydrogen release kinetics and preventing the formation of ammonia. The AB in JUC-32-Y started to release hydrogen at a temperature as low as 50 °C. The peak temperature of decomposition decreased 30 °C (shifted to 84 °C). AB inside JUC-32-Y can release 8.2 wt % hydrogen in 3 min at 95 °C and 8.0 and 10.2 wt % hydrogen within 10 min at 85 °C.
238 citations
TL;DR: In this paper, the rate of CO 2 absorption into a falling thin film has been measured using a wetted-wall column for aqueous ammonia between 0.6 and 6.5 times smaller than MEA at the measured temperatures, and it was shown that the difference in mass transfer rate is likely due to both the reduced temperature and differences in reactivity between ammonia and MEA with CO 2.
215 citations
TL;DR: In this article, single molecule reactions have been studied between nickel oxyhydroxide, urea, and the hydroxide ion to understand the process of urea dissociation into ammonia, isocyanic acid, cyanate ion, carbon dioxide, and nitrogen.
Abstract: Single molecule reactions have been studied between nickel oxyhydroxide, urea, and the hydroxide ion to understand the process of urea dissociation into ammonia, isocyanic acid, cyanate ion, carbon dioxide, and nitrogen. In the absence of hydroxide ions, nickel oxyhydroxide will catalyze urea to form ammonia and isocyanic acid with the rate-limiting step being the formation of ammonia with a rate constant of 1.5 × 10⁻⁶ s⁻¹. In the presence of hydroxide, the evolution of ammonia was also the rate-limiting step with a rate constant of 1.4 × 10⁻²⁶ s⁻¹. In addition, desorption of the cyanate ion presented an energy barrier of 6190 kJ mol⁻¹ suggesting that the cyanate ion cannot be separated from NiOOH unless further reactions occurred. Finally, elementary dissociation reactions with hydroxide ions deprotonating urea to produce nitrogen and carbon dioxide were analyzed. These elementary reactions were investigated along three paths differing in the order that protons were removed and the nitrogen atoms were rotated. The rate-limiting step was found to be the removal of carbon dioxide with a rate constant of 4.3 × 10⁻⁶⁵ s⁻¹. Therefore, the catalyst could be deactivated by the surface blockage caused by carbon dioxide adsorption.
203 citations
TL;DR: Thaumarchaeal appeared to dominate ammonia oxidation in this soil and oxidized ammonia arising from mineralization of organic matter rather than added inorganic nitrogen.
Abstract: Both bacteria and thaumarchaea contribute to ammonia oxidation, the first step in nitrification. The abundance of putative ammonia oxidizers is estimated by quantification of the functional gene amoA, which encodes ammonia monooxygenase subunit A. In soil, thaumarchaeal amoA genes often outnumber the equivalent bacterial genes. Ecophysiological studies indicate that thaumarchaeal ammonia oxidizers may have a selective advantage at low ammonia concentrations, with potential adaptation to soils in which mineralization is the major source of ammonia. To test this hypothesis, thaumarchaeal and bacterial ammonia oxidizers were investigated during nitrification in microcosms containing an organic, acidic forest peat soil (pH 4.1) with a low ammonium concentration but high potential for ammonia release during mineralization. Net nitrification rates were high but were not influenced by addition of ammonium. Bacterial amoA genes could not be detected, presumably because of low abundance of bacterial ammonia oxidizers. Phylogenetic analysis of thaumarchaeal 16S rRNA gene sequences indicated that dominant populations belonged to group 1.1c, 1.3, and "deep peat" lineages, while known amo-containing lineages (groups 1.1a and 1.1b) comprised only a small proportion of the total community. Growth of thaumarchaeal ammonia oxidizers was indicated by increased abundance of amoA genes during nitrification but was unaffected by addition of ammonium. Similarly, denaturing gradient gel electrophoresis analysis of amoA gene transcripts demonstrated small temporal changes in thaumarchaeal ammonia oxidizer communities but no effect of ammonium amendment. Thaumarchaea therefore appeared to dominate ammonia oxidation in this soil and oxidized ammonia arising from mineralization of organic matter rather than added inorganic nitrogen.
195 citations
TL;DR: Methane fermentation that was carried out along with ammonia striping to avoid ammonia accumulation that significantly inhibited methane production was demonstrated and methane production from chicken manure was successfully produced.
193 citations
TL;DR: It can be inferred from the adsorption results that physical adsor adaptation of ammonia on both MOFs dominated at ammonia pressures below 150 torr after which chemical reactions between ammonia and MOF frameworks take place.
TL;DR: In this paper, the authors proposed to use active free chlorine to remove ammonia from an acidic solution, while the formation of by-products such as chlorate and possibly perchlorate is minimized.
TL;DR: In this paper, the oxygen isotopic systematics for ammonia oxidation, the first step in the regeneration of nitrate from ammonium, were evaluated for their roles in determining the d18O of nitrite produced by four species of ammonia-oxidizing bacteria (AOB).
Abstract: We examined the oxygen isotopic systematics for ammonia oxidation, the first step in the regeneration of nitrate from ammonium. In particular, oxygen isotopic fractionation and exchange with water were evaluated for their roles in determining the d18O of nitrite produced by four species of ammonia-oxidizing bacteria (AOB). Microbially catalyzed oxygen isotopic exchange between nitrite and water was less than 25% at low cell densities (106 cells mL21) and ammonium concentrations (less than 50 mmol L21). The amount of exchange was relatively constant for a given species of ammonia oxidizer but varied between 1% and 25% among the four species tested. The d18O value of nitrite produced at a given water d18O value also varied by nearly 10% among the different species. Isotopic fractionation, either during oxygen (O2) incorporation by ammonia monooxygenase and/or water incorporation by hydroxylamine oxidoreductase plays an important role in setting the d18O of nitrite produced by AOB. This work provides a detailed characterization of the oxygen isotopic systematics of ammonia oxidation by AOB, which will help us better interpret the oxygen isotopic distributions of nitrite, nitrate, and nitrous oxide in terrestrial and aquatic environments. Nitrogen is an essential macronutrient whose supply can limit primary production and carbon export from the surface ocean on seasonal, annual, decadal, and millennial time scales. Nitrate (NO { ) is the primary form of fixed nitrogen in the sea, and much research has focused on
TL;DR: Controlling the cathode/anode surface area ratio appeared to be a very efficient way of shifting electrode potentials to optimal values, consequently favoring the conversion of nitrate to nitrogen during a paired galvanostatic electrolysis.
TL;DR: In this paper, the influence of phosphorus, alkaline and alkaline earth metals, chromium and copper on the catalytic activity and selectivity of a V2O5-WO3/TiO2 catalyst for the selective catalytic reduction (SCR) of nitrogen oxides with ammonia has been studied.
Abstract: The influence of phosphorus, alkaline and alkaline earth metals, chromium and copper on the catalytic activity and selectivity of a V2O5–WO3/TiO2 catalyst for the selective catalytic reduction (SCR) of nitrogen oxides with ammonia has been studied. These components are put through a catalytic aftertreatment system of a diesel engine as impurities of biodiesel (K, Na, P), urea solution (K, Na, Ca, Mg) and abrasion of the engine (Cr, Cu). The catalysts were exposed to corresponding nitrates or ammonium compounds in diluted solution by wet impregnation or deposition of inorganic aerosol particles. The second approach allows a more realistic investigation using catalysts and reaction conditions close to mobile application. Hereby, the effects of single catalyst poisons have been investigated. Furthermore, the influence of combinations of poisons using Design of Experiments (DOE) has been determined in case of impregnated catalysts. Physical and chemical characterization methods focusing on NH3-TPD, penetration profiles and chemical analysis have been carried out to gain insight into the extent and the mechanism of deactivation. Both impregnated and aerosol deactivated catalysts show a strong poisoning effect of alkaline metals due to a reduced ammonia adsorption capacity. This effect could be weakened by a simultaneous doping of phosphates or sulphates. Chromium and copper are moderate catalyst poisons but have the ability to increase the N2O production.
TL;DR: The economic analysis of the process showed that ammonia can be removed at a cost of 9.6 euro/kg NH(4)-N(removed), however, this value can be greatly reduced, however, if the value of the struvite produced is considered.
TL;DR: In this article, the exchange kinetics and thermodynamics of amines for ammonium in small (1-2 nm diameter) ammonium bisulfate and ammonium nitrate clusters were investigated using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS).
Abstract: . The exchange kinetics and thermodynamics of amines for ammonia in small (1–2 nm diameter) ammonium bisulfate and ammonium nitrate clusters were investigated using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Ammonium salt clusters were reacted with amine gas at constant pressure to determine the kinetics of exchange. The reverse reactions, where aminium salt clusters reacted with ammonia gas, were also studied, and no substitution of ammonia for amine was observed. Gibbs free energy changes for these substitutions were determined to be highly exothermic, −7 kJ/mol or more negative in all cases. Uptake coefficients (reaction probabilities) were found to be near unity, implying that complete exchange of ammonia in small clusters by amine would be expected to occur within several seconds to minutes in the ambient atmosphere. These results suggest that if salt clusters are a component of the sub-3 nm cluster pool, they are likely to be aminium salts rather than ammonium salts, even if they were initially formed as ammonium salts.
TL;DR: A biogas production first-order kinetic model accurately predicted the behaviour of the microorganisms affecting the thermophilic anaerobic digestion, allowing its evolution to be predicted.
TL;DR: In this article, polypropylene hollow-fiber membranes were used to achieve the removal of ammonia from aqueous solutions, in which the effects of several factors such as the initial concentrations of the ammonia and sulfuric acid solutions, the pH of the ammonium feed, the velocity of the feed streams and the presence of excess ions in the ammonia feed solution were investigated.
TL;DR: The experimental results showed that the decomposition of PNP conformed to the pseudo-first-order reaction kinetics under the applied conditions, and the removal of total organic carbon and total nitrogen was not as effective as that of P NP.
TL;DR: A generalized conclusion is that having pH approximately 8 is favorable in many situations, in which the effluent concentrations of total nitrite and total ammonium should be approximately equal.
Abstract: Recent studies on shortcut biological nitrogen removal (SBNR), which use the concept of denitrification from nitrite, have reported the key factors affecting nitrite build-up, such as dissolved oxygen (DO) limitation, pH, and free ammonia (FA) and free nitrous acid (FNA) inhibition. This study extends the concept of the traditional minimum substrate concentration (S(min)) to explain the simultaneous effect of those factors. Thus, we introduce the minimum DO concentration (DO(min)) and the maximum substrate concentration (S(max)) that are needed to support a steady-state biological system. We define all three values as the MSC values. The model provides a method to identify good combinations of pH, DO, and total ammonium nitrogen (TAN) to support shortcut nitritation. We use MSC curves to show that the effect of DO-alone and the effect of DO plus direct pH inhibition cannot give strong enough selection against nitrite oxidizing bacteria to work in a practical setting. However, adding the FA and FNA effects gives a strong selection effect that is accentuated near pH 8. Thus, a generalized conclusion is that having pH approximately 8 is favorable in many situations. We defined a specific operational boundary to achieve shortcut nitritation coupled to anaerobic ammonium oxidation (ANAMMOX), in which the effluent concentrations of total nitrite and total ammonium should be approximately equal. Experimental results for alkaline and acidic nitrite-accumulating systems match the trends from the MSC approach. In particular, acidic systems had to maintain higher total ammonium, total nitrite, and DO concentrations. The MSC values are a practical tool to define the operational boundaries for selecting ammonium-oxidizing bacteria while suppressing nitrite-oxidizing bacteria.
TL;DR: It was concluded that ammonia stripping at alkaline pH is important for anaerobic digestion of piggery wastewater and the alkali types should be chosen cautiously to avoid cation toxicity.
TL;DR: In this paper, the electrochemical oxidation of ammonia was investigated on a Ni/Ni(OH)(2) electrode prepared by potential cycling of a Ni electrode in 1 M NaClO4.
TL;DR: In this paper, the potential of partial ammonia substitution to improve the safety of hydrogen use and the effects on the performance of internal combustion engines, the propagation, development of surface cellular instability and nitrogen oxide (NOx) and nitrous oxide (N2O) emissions of spark-ignited spherical laminar premixed ammonia/hydrogen/air flames were studied experimentally and computationally.
TL;DR: In this paper, the capability of Chlorella vulgaris to remove nitrogen in the form of ammonia and/or ammonium ions from wastewater effluent in a local wastewater treatment plant (i.e., the Mill Creek Plant in Cincinnati, Ohio, U.S.A.) was studied.
TL;DR: In this article, the characteristics of the reaction between ammonium sulfite, the main desulfurizing solution, and the flue-gas-contained sulfur dioxide during the process of ammonia-based WFGD in a power plant were investigated.
TL;DR: In this paper, two carbons with different contents of sulfur were prepared and oxidized either by heating in air or by chemical treatment, and the materials were then tested as adsorbents of ammonia in dynamic conditions, at room temperature.
TL;DR: In this paper, ammonium nitrate formation was observed from the NOAA WP-3D aircraft over Houston during the 2006 Texas Air Quality Study with fast-response measurements of NH3, HNO3, particle composition, and particle size distribution.
Abstract: [1] Anthropogenic emissions of NOx (nitric oxide (NO) + nitrogen dioxide (NO2)), which in sunlight can be oxidized to form nitric acid (HNO3), can react with ammonia (NH3) to form ammonium nitrate particles. Ammonium nitrate formation was observed from the NOAA WP-3D aircraft over Houston during the 2006 Texas Air Quality Study with fast-response measurements of NH3, HNO3, particle composition, and particle size distribution. Typically, NH3 mixing ratios over the urban area ranged from 0.2 to 3 ppbv and were predominantly from area sources. No NH3 enhancements were observed in emission plumes from power plants. The few plumes with high NH3 levels from point source emissions that were sampled are analyzed in detail. While the paucity of NH3 data in emission inventories made point source identification difficult, one plume was traced to NH3 release from an industrial accident. NH3 mixing ratios in these plumes ranged from 5 to 80 ppbv. In these plumes, the NH3 enhancement correlated with a decrease in HNO3 mixing ratio and an increase in particulate NO3− concentration indicating ammonium nitrate formation. The ammonium nitrate aerosol mass budget in the plumes was analyzed to assess the quantitative agreement between the gas and aerosol phase measurements. The thermodynamic equilibrium between the gas and aerosol phase was examined for one flight by comparing the modeled dissociation constant for ammonium nitrate with NH3 and HNO3 measurements. The high levels of NH3 in these plumes shifted the equilibrium toward favorable thermodynamic conditions for the condensation of ammonium nitrate onto particles.
TL;DR: Anode-supported proton-conducting fuel cell with BaZr 0.1 Ce 0.7 Y 0.5 Sr 0.8 Fe 0.2 O 3−δ (BSCF) cathode was fabricated in this article.
TL;DR: In this paper, the selective catalytic reduction of NOx with ammonia over all Fe-zeolite catalyst was investigated experimentally and a transient kinetic model was developed, which includes reactions that describe ammonia storage and oxidation, NO oxidation, selective catalyst reduction (SCR) of NO and NO2, formation of N2O, ammonia inhibition and ammonium nitrate formation.
Abstract: The selective catalytic reduction of NOx with ammonia over all Fe-zeolite catalyst was investigated experimentally and a transient kinetic model was developed. The model includes reactions that describe ammonia storage and oxidation, NO oxidation, selective catalytic reduction (SCR) of NO and NO2, formation of N2O, ammonia inhibition and ammonium nitrate formation. The model call account for a broad range of experimental conditions in the presence of H2O, CO2 and O-2 at temperatures from 150 to 650 degrees C. The catalyst stores ammonia at temperatures up to 400 degrees C and shows ammonia oxidation activity from 350 degrees C. The catalyst is also active for the oxidation of NO to NO2 and the oxidation reaches equilibrium at 500 degrees C. The SCR of NO is already active at 150 degrees C and the introduction of equal amounts of NO and NO2 greatly enhances the conversion of NOx at temperatures up to 300 degrees C. The formation of N2O is negligible if small fractions of NO2 are fed to the reactor, but a significant amount of N2O is formed at high NO2 to NO ratios. An ammonia inhibition oil the SCR of NO is observed at 200 degrees C. This kinetic model contains 12 reactions and is able to describe the experimental results Well. The model was validated using short transient experiments and experimental conditions not used in the parameter estimation and predicted these new conditions adequately.