The Interaction between Otto Fuel II and Aqueous Hydroxylammonium Perchlorate (HAP), Part III: Depletion of Components within the Reacting Liquids

Gas chromatography (GC) with a Flame Ionisation Detector (FID) has been used to determine changes in the concentrations of the components of Otto Fuel II (OF) in contact with an 82% aqueous solution of hydroxylammonium perchlorate (HAP) in sealed vials at 31.7 °C during the period leading up to auto‐ignition of the two liquids. The concentration of hydroxylamine in HAP was monitored over the same period using a titration method. It was found that 2‐nitrodiphenylamine (2NDPA), the stabiliser in the OF, is completely consumed after about 65–70 h and that the concentration of hydroxylamine begins to fall at this point. 1,2‐Propanediol dinitrate (propylene glycol dinitrate, PGDN), the energetic component in the OF, is not depleted significantly until after about 90 h. The evolution of nitrous oxide (N₂O) between 65 and 90 h is attributed to the reaction of the hydroxylammonium ion with nitrous acids produced by PGDN decomposition at the liquid‐liquid interface. Carbon dioxide (CO₂) is evolved after ~ 90 h and is attributed to PGDN decomposition. HAP and PGDN are each thought to contribute to N₂O evolution after ~ 90 h.     

The Interaction between Otto Fuel II and Aqueous Hydroxylammonium Perchlorate (HAP), Part I: Initial Observations and Time‐to‐Event Measurements

Investigations have shown that a violent event (normally auto‐ignition) occurs after a relatively short period of time when the two immiscible liquids Otto Fuel II and 82% aqueous hydroxylammonium perchlorate (HAP) come into contact at temperatures between 30 °C and 50 °C. Under quiescent conditions the time from initial contact to an event (time‐to‐event) depends on the relative volumes of the liquids as well as the temperature but there is no significant difference between the time‐to‐event recorded in an open container and that recorded in a sealed container at the same temperature. It is concluded that key reactions in the build up to an event are taking place in both the Otto Fuel II and in the HAP solution.     

Absorption of NOx in packed column (II)

An absorption efficiency of packed column removing nitrogen oxides with water and NaOH solution under atmospheric pressure was studied. The efficiency and the acidity produced by absorption of NO, were measured in a packed column. The model developed that was based on the mass-transfer information for packed column and absorption mechanism accompanying the chemical reaction was compared with experimental results. Predictions using the model presented by the previous paper (part 1) was shown well to agree with from the experimental results (part II). The efficiency of NO_x, absorption is largely dependent on the height of packing material and the partial pressure of NO_x in the feed gas. The efficiency of NO_x absorption decreases with the increase of the acidity produced by recycling of water as a scrubber liquid. For the recycle mode with an aqueous NaOH solution as a scrubber liquid, NO_x absorption efficiency is shown to be constant until all of the C_OH- in the scrubber liquid are converted into C_H+.     

人工合成羟基磷灰石对水溶液中Pb~(2+)、Cd~(2+)离子的固定作用

以硝酸钙和磷酸氢二铵为反应物,采用均匀沉淀法制备羟基磷灰石粉体。羟基磷灰石能有效的固定溶液中重金属离子,并讨论了pH值、羟基磷灰石的用量、作用时间、离子的初始浓度及离子间的相互影响。试验结果表明：当羟基磷灰石的浓度为5g/L时,溶液中铅离子浓度和镉离子浓度分别为500 mg/L和30mg/L,常温搅拌30min后。在弱酸性或中性废水中,铅离子去除率可达99．6％以上,镉离子去除率可达到99．9％以上,溶液中残留镉离子浓度低于O．004．mg/L。     

Temporal and Spatial Variations in N2O Emissions from a Chinese Cabbage Field as a Function of Type of Fertilizer and Application

We conducted a field experiment in an Andosol near Tsukuba (Japan) to study the effects of the type of nitrogen fertilizer on nitrous oxide (N₂O) emissions and on nitrogen uptake by Chinese cabbage (Brassica campestris L.). We used four treatments: fertilizer containing no nitrogen (CONT), broadcast application of urea (BR-U), band application of urea (B-U), and band application of controlled-release urea (B-CU). The application rate was 250 kg N ha⁻¹, a conventional rate in the region. We measured N₂O flux two or three times a week during the 82-day growth period, then divided the cumulative emissions into three stages: early (28 days), middle (27 days), and late (27 days). The temporal variation in N₂O emissions differed among the treatments. Broadcast urea application produced 70% of N₂O emissions during the early stage. N₂O emissions increased with increasing cabbage growth in the CONT treatment, indicating that plant growth accompanied by increasing root biomass could stimulate N₂O emissions from unfertilized soil. There were no differences in the patterns of temporal variation in N₂O flux between the two band applications (B-U and B-CU); N₂O emissions in the early and middle stages were 46 and 42%, respectively, for B-U, vs. 41 and 40% for B-CU. However, the overall N₂O emission was reduced by 40.5% in the B-CU treatment compared with the B-U treatment. N₂O emissions from the soils within fertilized bands were dramatically higher than those between the fertilized bands, and this trend continued until harvesting.     

Hollow fiber membrane contactor transient experiments for the characterization of gas/liquid thermodynamics and mass transfer properties

We present results from experiments and numerical simulations of contact between a non-reactive gas (N₂O and CO₂) and a physical solvent (H₂O) occurring in a polypropylene (PP) hollow fiber membrane contactor. The closed-loop liquid flow within the experimental setup provides transient curves representing the progressive saturation of the solvent by the gas. We develop an in-house numerical model to fully characterize the gas/liquid mass transfer both in the non-wetted and in the wetted modes, i.e., when the liquid starts partially wetting the pores of the membrane. Using experiments and numerical simulations, we show that the Henry constant (H) and the molecular diffusion coefficient of a non-reactive gas absorbing into a liquid solvent can be extracted by parameter estimation. Both parameters are obtained within a single experiment at a constant temperature and the comparison with temperature-dependant correlations yields excellent agreement over the whole range of temperature studied in this work. Simulations show a partial wetting of the membrane pore by the liquid meniscus during a contact between CO₂ and H₂O, possibly due to the plasticizer effect of CO₂ inside the membrane contactor fibers.     

The Effect of H2 and the Presence of hot-O(ads) During the Decomposition of N2O on Platinum

The decomposition of N₂O was studied using a silica-supported Pt catalyst. The catalyst was found to exhibit short-lived activity at low temperatures to yield N₂ and O_(ads), the latter remained adsorbed on the surface and poisoned the active sites. Creation of hot-O_(ads) atoms during N₂O decomposition is proposed to allow O₂ desorption at intermediate temperatures. Inclusion of H₂ as a reducing agent greatly enhanced the activity and suppressed low temperature deactivation. Simultaneous and sequential pulsing of N₂O and H₂ showed that H₂ inclusion with the N₂O gas stream produced the greatest activity. A mechanism involving H_(ads) addition to “hot” oxygen atoms for H₂O formation is proposed.     

High pressure measurements and molecular modeling of the water content of acid gas containing mixtures

Water content of three carbon dioxide containing natural gas mixtures in equilibrium with an aqueous phase was measured using a dynamic saturation method. Measurements were performed up to high temperatures (477.6 K = 400°F) and pressures (103.4 MPa = 15,000 psia). The perturbed chain form of the statistical associating fluid theory was applied to predict water content of pure carbon dioxide (CO₂), hydrogen sulfide (H₂S), nitrous oxide (N₂O), nitrogen (N₂), and argon (Ar) systems. The theory application was also extended to model water content of acid gas mixtures containing methane (CH₄). To model accurately the liquid‐liquid equilibrium at subcritical conditions, cross association between CO₂, H₂S, and water was included. The agreement between the model predictions and experimental data measured in this work was found to be good up to high temperatures and pressures. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3038–3052, 2015     

Effect of the oxidation of activated carbon by hydrogen peroxide on its catalytic activity in the regeneration of Co(II)TETA

Cobalt(II) triethylenetetramine (Co(II)TETA) formed by soluble cobalt(II) salt combining with triethylenetetramine will be used as a wet denitration technique since it can interact with nitric oxide to accomplish quick absorption of NO from gas phase. However, the oxygen in the flue gas will oxidize Co(II)TETA to Co(III) TETA, resulting in the reduction of denitrification efficiency. Activated carbon has been used to promote the regeneration of Co(II)TETA due to its unique surface characteristics. Hydrogen peroxide solution is utilized as a modifier in the carbon modification to improve the catalytic performance of activated carbon. The experiments demonstrate that the best regeneration efficiency of Co(II)TETA is gained by the modified carbon impregnated in 0.05 mol L⁻¹ H₂O₂ solution at 70°C for 12 h with a solid/liquid ratio of 1/50 (g/mL) followed being activated at 400°C for 2 h in N₂. After being treated with hydrogen oxide solution, the surface area and acidity of the carbon is increased. Continuous experiments reveal that the NO removal efficiency gained by modified activated carbon is about 8.36% higher than that gained by the original carbon.     

Removal of Pb(II) from aqueous solutions by using clinoptilolite and bentonite as adsorbents

In the present study, the ability of natural zeolite clinoptilolite and bentonite (clay) to remove Pb(II) from aqueous solutions has been investigated in batch reactors with a maximum contact time of 120 min. Adsorption tests of Pb(II) were carried out using a solution concentration of 1,036 ppm at initial pH = 4, and solid to liquid ratio of 2 g/100 mL. The effects of agitation speed (0, 100, 200, 500 rpm), temperature (28°C, 45°C, 60°C) and particle size (2.5–5.0 mm, dust) of the minerals were examined. The effect of acidity of the aqueous solution was also examined. Bentonite was found to be more effective for the removal of Pb(II) than clinoptilolite, under the experimental conditions used. The removal of Pb(II) using bentonite reached 100% at ambient temperature and mild agitation (100 rpm), while it was approximately 90% at 60°C without agitation. On the other hand, the highest removal level reached by clinoptilolite was 55%. Clinoptilolite dust is found to be more efficient than granular clinoptilolite. Agitation and temperature affected the uptake of Pb(II), especially in the case of granular clinoptilolite (2.5–5.0 mm). Finally, it can be seen that acidity of the aqueous solution influences the removal of lead by the minerals. The adsorption of lead increases with an increase in pH of the solution from 1 to 4.     

Preparation of a PVA/HAP composite polymer membrane for a direct ethanol fuel cell (DEFC)

A novel PVA/Hydroxyapatite (HAP) composite polymer membrane was prepared by the direct blend process and solution casting method. The characteristic properties of the PVA/HAP composite polymer membranes were investigated using thermal gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), micro-Raman spectroscopy and the AC impedance method. An alkaline direct ethanol fuel cell, consisting of an air cathode with MnO₂ carbon inks based on Ni-foam, an anode with PtRu black on Ni-foam, and the PVA/HAP composite polymer membrane, was assembled and investigated. It was found that the alkaline direct ethanol fuel cell comprising of a novel cheap PVA/HAP composite polymer membrane showed an improved electrochemical performance in ambient temperature and air. As a result, the maximum power density of the alkaline DEFC, using a PtRu anode based on Ni-foam (10.74 mW cm⁻²), is higher than that of DEFC using an E-TEK PtRu anode based on carbon (7.56 mW cm⁻²) in an 8M KOH + 2M C₂H₅OH solution at ambient temperature and air. These PVA/HAP composite polymer membranes are a potential candidate for alkaline DEFC applications.     

Changes in the N2O concentration in the gas tract of a UKL-7 unit in the production of nonconcentrated nitric acid

The N₂O concentration in the nitrous and tail gas along the tract of nine UKL-7 devices at OAO Novomoskovsk Azot facilities employing high-temperature catalytic cleansing (HTCC, seven devices) and low-temperature selective catalytic cleansing (SCC, two devices) is monitored to cleanse the emitted gases formed during the manufacture of nonconcentrated nitric acid from nitrogen oxides. N₂O formation in the layer of platinoid catalyst takes place in the gauze located at the beginning of the gas tract due to relatively low temperatures. Sampling is performed at 6 analysis points. Due to the lack of an analysis point at the outlet from the catalytic layer, the missing values of the N₂O concentration are determined from calculations based on the data obtained in a test reactor with a working diameter of 0.15 m functioning in the mode of the industrial reactor of the UKL-7 unit. The results from monitoring demonstrate that the values of N2O differ substantially between individual UKL-7 units (the values for the N₂O concentration in the nitrous gas downstream of the boiler lie in the range 1320–1810 ppm), which can be explained by differences in the flow of hydrodynamic gas through the catalyst layer. Since in the devices with HTCC the N₂O concentration in the cleansed tail gas is lower than the acceptable concentrations, additional cleansing from N₂O is not required. Elevated N₂O concentrations (680–1130 ppm) are found in the tail gases of devices with SCC, which necessitates additional cleansing. It would be logical to place the unit for cleansing the tail gases from N₂O downstream of the gas turbine.     

Microwave sintering of fine grained HAP and HAP/TCP bioceramics

The effect of microwave sintering conditions on the microstructure, phase composition and mechanical properties of materials based on hydroxyapatite (HAP) and tricalcium phosphate (TCP) was investigated. Fine grained monophase HAP and biphasic HAP/TCP biomaterials were processed starting from stoichiometric and calcium deficient nanosized HAP powders. The HAP samples microwave (MW) sintered for 15 min at 900 °C, with average grain size of 130 nm, showed better densification, higher density and certainly higher hardness and fracture toughness than samples conventionally sintered for 2 h at the same temperature. By comparing MW sintered HAP and HAP/TCP samples, it was concluded that pure HAP ceramics have superior mechanical properties. For monophase MW sintered HAP samples, the decrease in the grain size from 1.59 μm to 130 nm led to an increase in the fracture toughness from 0.85 MPa m^1/2 to 1.3 MPa m^1/2.     

Effects of soil solution on the dynamics of N2O emissions: a review

In this review, which consists of two parts, major interactions between nitrous oxide (N₂>O) and soil solution are described. In the first part, as an introduction, concentrations of dissolved N₂>O in different aqueous systems are summarized. An inventory of data on maximal N₂>O concentrations in soil solution (up to 9984 g N₂>O-N l^–1>) and in soil air (up to 8300 ppm) from literature is presented. The peak N₂>O concentrations represent a N₂>O supersaturation in the soil solution up to 30000 times with respect to ambient air and a soil air N₂>O concentration about 25000 times higher than in the atmosphere. The main physico–chemical parameters (solubility, diffusion) controlling N₂>O distribution between soil solution and soil air are outlined. The influences of cultivation practice, nitrogen turnover, water content and temperature on N₂>O a ccumulation in soil solution and soil air are reviewed. In the second part some models of N₂>O dynamics in soils are discussed with emphasis on N₂>O transport processes. A simple qualitative scheme is developed to categorize the effects of the soil solution on N₂>O dynamics in soils. In this scheme the temporary, intensive N₂>O oversaturation of the soil solution is interpreted as a result of gas diffusion inhibition by water (barrier function of soil solution) resulting in an accumulation of N₂>O. In addition, N₂>O supersaturation is an indication that transitory much N₂>O can be stored in the soil solution (storage function of soil solution). Where the soil solution flows up-, down- or sidewards it can act as a relevant transport medium for dissolved N₂>O (transport function of soil solution). This scheme is applied to examples from the literature.     

Combustion synthesis of α-Si3N4 assisted by molten salt additives

Combustion synthesis (CS) of silicon nitride (Si₃N₄), assisted by molten salt additives under high N₂ pressure, is reported. The effect of salt additives (NaCl, MgCl₂, and MgCl₂?6H₂O) on the reaction temperature and the final α-Si₃N₄ content is studied. The maximum reaction temperature (T_max) decreased with an increase in the amount of the salt additives. NaCl is found to be the most suitable as it results in 57.8% α-Si₃N₄ at 30 mass% concentration. MgCl₂ is strongly hygroscopic, and MgCl₂?6H₂O decomposes at very low temperature. Therefore, they absorb heat at low temperatures, which makes it difficult to reach the ignition temperature, thereby hindering the reaction propagation. Si₃N₄ is necessary as a diluent for creating pores in the raw materials to allow effective penetration and contact of N₂ gas with the Si particles.     

Kinetics of the exchange between battery-active manganese dioxides and manganese(II) ions in aqueous solution

The initial rate and the extent of exchange between ⁵⁶Mn-labelled dioxides and 0.1M MnSO₄ solution at 25°C and pH 5.4 were found to increase in the series: β-MoO₂ (R4), <γ-MnO₂ (R2), < ?-MnO₂. The rate of exchange between R2 and 0.1M MnSO₄ solution at pH 2.0 was higher than the corresponding results at pH 5.4 but the results were similar at the two pH values when R2 was washed with dilute acid (pH 2.0) prior to the exchange at pH 2.0. The results of the exchange for the size fraction ?120 to + 300 mesh of R2 were similar to those for the unsieved R2 under the same conditions. When either R2 or R4 were partially reduced with N₂H₄·H₂O solution prior to the exchange, the results were appreciably higher than those obtained for the unreduced solids—especially in the case of R2. When different concentrations of Mn(NO₃)₂ solution were used with R2, the percentage exchange increased to a small extent as the concentration increased ten-fold. The variation of the solid: solution ratio had a minor effect on the extent of exchange between R2 and 0.1M MnSO₄ solution.     

Real time intracellular pH dynamics in Listeria innocua under CO2 and N2O pressure

This article investigates the inactivation mechanism of high-pressure food treatment, considered as alternative to conventional biocidal processes. We aimed to determine intracellular pH decrease under CO₂ and N₂O pressure, so far postulated as one of the main causes of inactivation. Working with a lab-scale bioreactor in mild conditions – 25 °C and pressures up to 8 MPa – we monitored – for the first time during pressurization – cytoplasmic pH variations of Listeria innocua labeled with pH-sensitive fluorophores based on fluorescein.We show that carbonic acid, due to solubilization of CO₂ into the aqueous phase, causes a rapid pH drop in the cytosol, reaching pH 4.8 at 1 MPa and falls below the detection limit of the indicator fluorophore of pH 4.0. This correlates with a reduced viability (below 90%) in all the pressure ranges investigated. Contrarily, treatment under N₂O pressure reduces cell viability without significant pH-drop neither of intra- nor extra-cellular liquid at any pressure investigated. The pH value remains between 7 and 6 while an inactivation of more than 80% is achieved at 8 MPa.Our data clearly demonstrate that, as a critical pressure is achieved, microbial inactivation is mainly due to pressure-induced membrane permeation – stimulated by non-acidifying fluids as well, rather then cytoplasmic acidification, as widely argued so far. A definitive understanding of the microbial inactivation mechanism due to CO₂/N₂O under pressure has been advanced significantly.     

Mineralization of hydroxyapatite on a polymer substrate in a solution supersaturated by polyelectrolyte

In this article, a new method to construct composites of hydroxyapatite (HAP) and polymer material is introduced. A previously developed method for mineralization of CaCO₃ on a polymer substrate was applied to HAP. A solution that contained Ca²⁺, PO₄^3–, and OH‐ ions was supersaturated with polyacrylic acid (PAA) that, at the same time, formed a polymer complex with the substrate, a polyvinyl alcohol (PVA) film, at the substrate surface. In this thin surface layer, nucleation of HAP took place. Subsequently, the disklike domains of HAP that were generated spread until they covered the PVA film surface. By regulating the pH of the supersaturated solution at around 7.4, the domain size decreased and the quantity of deposited material increased. Approximately 20 mg of HAP coating was obtained on a PVA film of 1 cm radius when the film was soaked in single 200 mL batch of the supersaturated solution for 21 days. The junction between HAP layer and PVA substrate film was found to be very firm. When a crosslinked PVA/PAA was used as the substrate, the film swelled in the supersaturated solution to form a hydrogel. Then mineralization took place within the gel, and a transparent monolithic composite of HAP and the polymer network was obtained. In 13 days, the weight increase was 29 mg, which corresponded to a 71 wt % HAP mineralization ratio of the composite. By changing crosslinking degree and HAP mineralization ratio, the flexibility of composite will be controlled in a wide range. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1465–1470, 2006     

Effects of the depth of NO and N2O productions in soil on their emission rates to the atmosphere: analysis by a simulation model

Many factors are concerned in the changing forms of nitrogen compounds in soil, so it is not easy to make precise models to simulate the concentration profiles of soil nitric oxide (NO) and nitrous oxide (N₂O) and their emission rates under various soil conditions. We prepared a simple mathematical simulation model based on soil concentration profiles of NO and N₂O. The profiles were measured at lysimeters filled with Andosol soil and fertilized with ammonium sulfate at rate of 200 kgNha^-1, incorporating to plow layer (Hirose & Tsuruta, 1996). In this model, diffusion of gases in soil followed Fick's law and the diffusion coefficient was adopted from Sallam et al. (1984). The gas production rate was set up at constant value in the site of gas production, and the gaseous consumption followed Michaelis-Menten kinetics. By changing only the depth of NO and N₂O production in soil in this model, we obtained the following results.(1) When the depth of gas production was set at near the soil surface (NO: 0–10 cm, N₂O: 0-8 cm), the emission rates of both gases corresponded with the results of the lysimeter-measurement.(2) When the depth of gas production was shifted down 10 cm deeper (NO: 10–20 cm, N₂O: 10-18 cm), the gas emission rate of NO decreased to 1.3% of (1), while that of N₂O was almost the same as (1).(3) In the case that the total intensity of produced gases was not changed from (1) or (2), but that the extent of gas productions expanded 3 times wider (NO: 0–30 cm, N₂O: 0–24 cm) than (1) or (2), the emission rates of NO and N₂O became 26% and 95% of (1), respectively.The above results suggest the possibility of mitigating NO emission by setting the site of gaseous production in deeper soil, e.g. by means of deep application of fertilizer.     

Rapid measurement of gas diffusivity in liquids using a tube-in-tube reactor with an unsteady-state strategy

In this work, an unsteady-state strategy for rapid measurement of gas diffusivity in liquid is proposed, which has a quick perturbation of the liquid flow rate in inner tube for obtaining the change of gas flow rate across the membrane with time. The strategy has taken full advantages of the tube-in-tube reactor that possesses a high permeability Teflon AF-2400 membrane to accelerate the diffusion rate of gas to liquid without direct contact between the two phases. With a developed mathematical model fitting the recorded variation of gas flow rate with time, the gas diffusivity in liquid can be determined within 0.5–3 min compared with the conventional methods of 4–14 hr. In addition, the strategy is demonstrated with several gas–liquid systems (O₂-DMSO, CO₂-[Emim] [NTf₂] and CO₂-[Bmim] [BF₄]) with varied viscosities and temperatures, showing a good agreement with literature values with less than 10% deviation.