Permeation Of NH3 Research Articles

Fabrication of 3-(trihydroxysilyl)-1-propanesulfonic acid membranes with superior affinity and selectivity for NH3 permeation over H2 and N2 at 50–300 °C

Ammonia (NH3) produced by Haber-Bosch process is separated through the condensation process, which needs a large amount of energy consumption. Membrane separation technology is compelling for achieving energy-saving and efficient NH3 separation. Therefore, 3-(trihydroxysilyl)-1-propanesulfonic acid (TPS) was applied, for the first time, to fabricate sulfonic silica-based membranes and evaluated for NH3 selective permeation. The amorphous siloxane network can be formed by simple condensation of silanol (Si–OH) under sulfonic acid (-SO3H) self-catalysis, as confirmed by the results of Fourier transform infrared spectroscopy and X-Ray diffractometry. Moreover, TPS xerogel powders dried from TPS sols showed excellent thermal stability and dense structure via thermogravimetric and N2 adsorption analyses. Importantly, an intensive NH3 adsorption amount of ∼3.0 mmol g−1 for TPS xerogels from NH3 adsorption and temperature-programmed desorption was twice higher than the reported oxidized (3-mercaptopropyl)trimethoxysilane xerogels (∼1.41 mmol g−1), which was ascribed to the inherently stronger proton-acidic -SO3H groups in TPS. Finally, TPS membranes prepared using TPS solutions diluted with ethanol expressed superior NH3-selective permeation based on favorable molecular sieving and NH3 adsorption-diffusion via single and binary gas permeation, especially remarkable NH3 permeance of ∼2.6 × 10−7 mol m−2 s−1 Pa−1 and excellent NH3/N2 selectivity of 266 at 300 °C.

Optimization of Ni-amine coordination for improving NH3 permeation through nickel-doped bis[3-(trimethoxysilyl)propyl] amine membranes

Nickel-coordinated bis[3-(trimethoxysilyl)propyl] amine (BTPA) xerogels and membranes reportedly showed excellent NH3 adsorption, permeance, and permselectivity. To study the H2, N2, and NH3 permeation properties of Ni-BTPA membranes in detail, the nickel doping amount in BTPA should be optimized. In this work, Ni-BTPA sols/gels with nickel/propylamine (Ni/N–H) mole ratios of 0, 0.125, 0.25, 0.50, and 1.00 were prepared and characterized via DLS, FT-IR, UV–vis, TG-MS, and XRD, indicating that the sol size and the interactions between nickel and N–H/N=O were increased with an increase in the Ni/N–H mole ratio. The large NH3 adsorption and desorption amounts were obtained with 0.50 and 1.00 Ni-BTPA xerogels via NH3-TPD measurement, additionally, the competitive interactions between nickel and NH3/other functional groups, such as N–H and N=O, were found in 1.00 Ni-BTPA, which could negatively affect the NH3 affinity. The pore sizes of membranes were gradually enlarged in Ni-BTPA with increases in the nickel content, which improved gas permeation. Due to the enlargement of the pore size and the sufficient NH3 affinity, the 0.50 Ni-BTPA membrane recorded the optimal performance with a NH3 permeance of ∼ 2.8 × 10-6 mol m−2 s−1 Pa−1, an ideal NH3/H2 selectivity of 11, and NH3/N2 selectivity of 102 at 200 °C.

Super selective ammonia separation through multiple-site interaction with ionic liquid-based hybrid membranes

Efficient separation and recovery of ammonia (NH3) is essential for environmental protection and resource utilization. In this work, hybrid membranes for NH3 separation through multiple-site interaction were developed by combining the unique features of ionic liquids (ILs) and a midblock-sulfonated block copolymer. The functionalized ILs ([2-Mim][NTf2] and [Im][NTf2]) with ammonia interaction sites were incorporated into the Nexar™ matrix, which greatly improves the affinity for NH3 over nitrogen (N2) and hydrogen (H2). Benefited from the self-assembly of the block copolymer, the hybrid membranes primarily exhibit lamellar morphology. More continuous ionic domains with well-distributed ILs were formed in the hybrid membranes, contributing to forming interconnected channels for enhanced gas transport. In this case, addition of the ILs into the Nexar matrix significantly enhances NH3 separation performance. Nexar/[Im][NTf2]-25 membrane achieves the highest NH3 permeability of 3565 Barrer and a maximum NH3/N2 and NH3/H2 ideal selectivity of 1865 and 364, respectively. The significantly enhanced NH3 permeation compared with the neat Nexar membrane indicates the positive role of ILs in the hybrid membranes.

Solvent‐Templated Block Ionomers for Base‐ and Acid‐Gas Separations: Effect of Humidity on Ammonia and Carbon Dioxide Permeation

AbstractAs energy needs continue to drive the development of biogas and fossil‐fuel technologies, methods by which to selectively remove basic (NH3) and acidic (CO2) gases are becoming increasingly important, especially in light of global climate change. Block copolymers are considered as suitable membrane candidates in gas separations due to the ability of such copolymers to microphase‐separate and spontaneously form nanoscale morphologies that exhibit spatially modulated chemical specificity. Incorporation of charged moieties along the midblock of a thermoplastic elastomeric multiblock copolymer yields an amphiphilic block ionomer possessing a flexible molecular network stabilized by rigid endblocks. The presence of hydrophilic microdomains introduces an important consideration regulating molecular transport: humidity. In this study, solvent‐templating paradigms are employed to control the morphologies of midblock‐sulfonated pentablock ionomers, as discerned by electron microscopy and X‐ray scattering. The effect of humidity on the permeation of NH3, CO2, and N2is then investigated through the resulting membranes. As expected, NH3permeates significantly faster than N2, especially under humid conditions. Although not as pronounced, similar behavior is observed for CO2, thereby establishing that this block ionomer is generally selective to humidified polar gases.

Proton-sensing transistor systems for detecting ion leakage from plasma membranes under chemical stimuli.

The plasma membrane toxicity and hemolysis are widely and routinely evaluated in biomaterials science and biomedical engineering. Despite the recent development of a variety of methods/materials for efficient gene/drug delivery systems to the cytosol, the methodologies for safety validation remain unchanged in many years while leaving some major issues such as sensitivity, accuracy, and fast response. The paper describes a new way of measuring the plasma membrane leakage in real time upon challenge by toxic reagents using a solid-state transistor that is sensitive to proton as the smallest indicator. Our system was reliable and was correlated to the results from hemolysis assay with advanced features in sensitivity, fast response, and wide applicability to chemical species. The downsizing and integration features of semiconductor fabrication technologies may realize cytotoxicity assays at the single-cell level in multi-parallel.

Aquaporin 4 as a NH3 Channel

Ammonia is a biologically potent molecule, and the regulation of ammonia levels in the mammalian body is, therefore, strictly controlled. The molecular paths of ammonia permeation across plasma membranes remain ill-defined, but the structural similarity of water and NH3 has pointed to the aquaporins as putative NH3-permeable pores. Accordingly, a range of aquaporins from mammals, plants, fungi, and protozoans demonstrates ammonia permeability. Aquaporin 4 (AQP4) is highly expressed at perivascular glia end-feet in the mammalian brain and may, with this prominent localization at the blood-brain-interface, participate in the exchange of ammonia, which is required to sustain the glutamate-glutamine cycle. Here we observe that AQP4-expressing Xenopus oocytes display a reflection coefficient <1 for NH4Cl at pH 8.0, at which pH an increased amount of the ammonia occurs in the form of NH3 Taken together with an NH4Cl-mediated intracellular alkalization (or lesser acidification) of AQP4-expressing oocytes, these data suggest that NH3 is able to permeate the pore of AQP4. Exposure to NH4Cl increased the membrane currents to a similar extent in uninjected oocytes and in oocytes expressing AQP4, indicating that the ionic NH4 (+) did not permeate AQP4. Molecular dynamics simulations revealed partial pore permeation events of NH3 but not of NH4 (+) and a reduced energy barrier for NH3 permeation through AQP4 compared with that of a cholesterol-containing lipid bilayer, suggesting AQP4 as a favored transmembrane route for NH3 Our data propose that AQP4 belongs to the growing list of NH3-permeable water channels.

In situ precipitation: a novel approach for preparation of iron-oxide magnetoliposomes.

BackgroundConventional methods of preparing magnetoliposomes are complicated and inefficient. A novel approach for magnetoliposomes preparation was investigated in the study reported here.MethodsFeCl3/FeCl2 solutions were hydrated with lipid films to obtain liposome-encapsulated iron ions by ultrasonic dispersion. Non-encapsulated iron ions were removed by dialysis. NH3 · H2O was added to the system to adjust the pH to a critical value. Four different systems were prepared. Each was incubated at a different temperature for a different length of time to facilitate the permeation of NH3 · H2O into the inner phase of the liposomes and the in situ formation of magnetic iron-oxide cores in the liposomes. Single-factor analysis and orthogonal-design experiments were applied to determinate the effects of alkalization pH, temperature, duration, and initial Fe concentration on encapsulation efficiency and drug loading.ResultsThe magnetoliposomes prepared by in situ precipitation had an average particle size of 168±14 nm, zeta potential of −26.2±1.9 mV and polydispersity index of 0.23±0.06. The iron-oxide cores were confirmed as Fe3O4 by X-ray diffraction and demonstrated a superparamagnetic response. Encapsulation efficiency ranged from 3% to 22%, while drug loading ranged from 0.2 to 1.58 mol Fe/mol lipid. The optimal conditions for in situ precipitation were found to be an alkalization pH of 12, temperature of 60°C, time of 60 minutes, and initial Fe concentration of 100 mM Fe3+ + 50 mM Fe2+.ConclusionIn situ precipitation could be a simple and efficient approach for the preparation of iron-oxide magnetoliposomes.

Reverse selective NH3/CO2 permeation in fluorinated polymers using membrane gas separation

The analysis of the process of gas and vapour permeation through dense polymers is of primary importance for packaging, controlled release and membrane separation processes. A significant amount of polymer permeability data has already been reported, especially for permanent gases, such as N2, O2, H2, CH4 and CO2, although a very small amount of data is available for ammonia (NH3). In this case, the experimental results show the faster permeation of NH3 in comparison to CO2, which is in agreement with the solution diffusion model predictions. NH3 is smaller and more condensable than CO2. In this study, the solubility, diffusion coefficient and permeability of NH3, CO2 and N2 in ten different polymers were investigated between 5 and 50°C. A reverse NH3/CO2 permeation selectivity is occasionally observed for dense fluorinated polymers (PTFE, FEP, Hyflon AD and Teflon AF). This unusual behaviour is interpreted in the light of the diffusion and sorption coefficients obtained from time lag experiments which tend surprisingly to show in fluorinated polymers: a NH3/CO2 solubility selectivity systematically lower than expected by the usual correlations and, in some cases, lower diffusion coefficients for NH3 than for CO2. This peculiar result is interpreted from the differences between NH3 and CO2 interactions with fluorine atoms, similarly to the differential solubility phenomena of these two species which have previously been clearly established in fluorinated liquids.

AmtB-mediated NH3 transport in prokaryotes must be active and as a consequence regulation of transport by GlnK is mandatory to limit futile cycling of [formula omitted

The nature of the ammonium import into prokaryotes has been controversial. A systems biological approach makes us hypothesize that AmtB-mediated import must be active for intracellular NH4+ concentrations to sustain growth. Revisiting experimental evidence, we find the permeability assays reporting passive NH3 import inconclusive. As an inevitable consequence of the proposed NH4+ transport, outward permeation of NH3 constitutes a futile cycle. We hypothesize that the regulatory protein GlnK is required to fine-tune the active transport of ammonium in order to limit futile cycling whilst enabling an intracellular ammonium level sufficient for the cell’s nitrogen requirements.

Calibration and evaluation of nitric acid and ammonia permeation tubes by UV optical absorption.

An ultraviolet (UV) optical absorption system has been developed for absolute calibrations of nitric acid (HNO3) and ammonia (NH3) permeation tube emission rates. Using this technique, dilute mixtures containing NH3 or HNO3, both of which interact strongly with many surfaces, are accurately measured at levels below a part per million by volume. This compact and portable instrument operates continuously and autonomously to rapidly (<1 h) quantify the emission of trace gases from permeation devices that are commonly used to calibrate air-monitoring instruments. The output from several HNO3 and NH3 permeation tubes, with emission rates that ranged between 13 and 150 ng/min, was examined as a function of temperature, pressure, and carrier gas flow. Absorptions of 0.015% can be detected which allows a precision (3sigma) of +/-1 ng/min for the HNO3 and NH3 permeation tubes studied here. The accuracy of the measurements, which relies on published UV absorption cross sections, is estimated to be +/-10%. Measurements of permeation tube emission rates using ion chromatography analysis are made to further assess measurement accuracy. The output from the HNO3 and NH3 permeation tubes examined here was stable over the study period, which ranged between 3 months and 1 year for each permeation tube.

Bekaert Group, Belgium

The analysis of the process of gas and vapour permeation through dense polymers is of primary importance for packaging, controlled release and membrane separation processes. A significant amount of polymer permeability data has already been reported, especially for permanent gases, such as N2, O2, H2, CH4 and CO2, although a very small amount of data is available for ammonia (NH3). In this case, the experimental results show the faster permeation of NH3 in comparison to CO2, which is in agreement with the solution diffusion model predictions. NH3 is smaller and more condensable than CO2. In this study, the solubility, diffusion coefficient and permeability of NH3, CO2 and N2 in ten different polymers were investigated between 5 and 50 °C. A reverse NH3/CO2 permeation selectivity is occasionally observed for dense fluorinated polymers (PTFE, FEP, Hyflon AD and Teflon AF). This unusual behaviour is interpreted in the light of the diffusion and sorption coefficients obtained from time lag experiments which tend surprisingly to show in fluorinated polymers: a NH3/CO2 solubility selectivity systematically lower than expected by the usual correlations and, in some cases, lower diffusion coefficients for NH3 than for CO2. This peculiar result is interpreted from the differences between NH3 and CO2 interactions with fluorine atoms, similarly to the differential solubility phenomena of these two species which have previously been clearly established in fluorinated liquids.

Differential pH restoration after ammonia-elicited vacuolar alkalisation in rice and maize root hairs as measured by fluorescence ratio

Changes of vacuolar pH in hair cells of young rice (Oryza sativa L.) and maize (Zea mays L.) roots were measured after ammonia application at various levels of external pH. After loading the pH-sensitive, fluorescent dye Oregon green 488 carboxylic acid 6-isomer into the vacuoles of root hairs, ratiometric pH data of high statistical significance were obtained from root hair populations comprising hundreds of cells. The pH of the vacuole at external pH 5.0 was 5.32 ± 0.08 (±SD, n= 15) and 5.41 ± 0.13 (±SD, n= 15) in rice and maize, respectively. A moderate external ammonia concentration of 2 mM led to vacuolar alkalisation at both, low (pH 5.0) and high (pH 7.0–9.0) external pH, presumably due to NH3 permeation into the vacuole. With increasing external pH, ammonia application did not cumulatively increase vacuolar pH. In rice, the increase in vacuolar pH ranged from 0.1–0.8 pH units; in maize a more constant increase of 0.5 pH units was observed. The vacuolar pH increase was efficiently depressed in rice (especially at high external pH), but not in maize. Inhibition of the tonoplast H+-ATPase by concanamycin A raised vacuolar pH and increased the ammonia-elicited vacuolar alkalisation in both species, proving that vacuolar H+-ATPase activity counters the ammonia-elicited alkalisation effect. However, even under conditions of vacuolar H+-ATPase inhibition, rice was still able to restore an ammonia-elicited pH increase. High vacuolar pH levels as found in maize under conditions of high NH3 influx may derive from inefficient cytosolic ammonia assimilation and tonoplast proton pumping. Thus, in maize, prolonged reduction of the proton gradient between the cytosol and the vacuole may play an important role in NH3 toxicity.

Ammonium fluxes into plant roots: Energetics, kinetics and regulation

AbstractAmmonium uptake across the plasma membranes of seedling roots of intact rice plants is thermodynamically active at low external concentrations, and consequently, electrogenic uniport is an unlikely mechanism for influx. At higher NH4+ concentrations uptake is passive and electrogenic uniport is a possibility. While passive permeation of NH3 is also possible at high external [NH4+], influx measurements at 10 mM NH4+ demonstrated a pH dependence which was inconsistent with significant NH3 permeation. Kinetic studies using 13NH4+ established that influx at low external [H4+] occurred via high affinity transport systems (HATS) in rice and spruce, while at higher [NH4+], influx was mediated by low affinity transport systems (LATS), that showed linear concentration dependence. Ammonium influx via the HATS was shown to be up‐regulated or down‐regulated in response to changes of N status, whereas influx in the LATS was insensitive to N status. The identity or identities of the regulatory signals responsible for controlling influx are discussed.

Ammonia transport in a mathematical model of rat proximal tubule

Pathways for ammonia transport have been incorporated within a model of rat proximal tubule [A. M. Weinstein. Am. J. Physiol. 263 (Renal Fluid Electrolyte Physiol. 32): F784-F798, 1992]. The luminal membrane includes a Na+/NH4+ exchanger, while at the peritubular membrane there is uptake of NH4+ on the Na(+)-K(+)-adenosinetriphosphatase (Na(+)-K(+)-ATPase); both luminal and peritubular cell membranes contain conductive pathways for NH4+. The model equations have been expanded to include cellular ammoniagenesis. The principal focus of this study is the interplay of forces that can raise proximal tubule fluid total ammonia concentration 10-fold higher than in arterial plasma. Analysis of a cellular model reveals that luminal membrane Na+/NH4+ exchange, cellular production of ammonia, and peritubular membrane NH4+ uptake (via Na(+)-K(+)-ATPase or via K+ channel) all act in parallel to drive ammonia secretion. This derives from the cellular interconversion of NH4+ and NH3 and the free permeation of NH3 across cell membranes. It implies that inhibition of the luminal membrane transporter does not block the contribution of peritubular uptake to the overall active transport of ammonia. Conversely, when inhibition of the luminal membrane Na+/NH4+ entry (i.e., Na+/H+ inhibition) depresses transcellular Na+ flux, then the decrease of NH4+ flux through the peritubular Na+ pump enhances the apparent importance of the luminal membrane pathway. This analysis is confirmed in the numerical calculations and is a departure from the Ussing paradigm of series membrane Na+ transport. Although active secretion of ammonia by this tubule is substantial, the relative contribution of luminal Na+/NH4+ exchange and of peritubular uptake via the Na+ pump remains uncertain. The determination of peritubular capillary NH4+ concentration will be crucial to resolving this uncertainty, with lower concentration (i.e., closer to systemic arterial ammonia) obligating greater luminal membrane Na+/NH4+ exchange.

NH3 permeation through the apical membrane of MDCK cells is via a lipid pathway

The pathway for NH3 permeation across the apical membrane of MDCK cells was determined by measuring the effect of membrane fluidizing agents, protein reactive agents, and temperature on cellular NH3 influx. The rate of NH3 influx was calculated from the time course of increase in intracellular pH (pHi), measured with 2,7-biscarboxyethyl-5(6)-carboxyfluorescein, when MDCK cell monolayers were exposed to NH4Cl. The apical membrane NH3 permeability was 7.13 +/- 0.37 x 10(-3) cm/s (n = 12) at 37 degrees C and 1.23 +/- 0.07 x 10(-3) cm/s (n = 7) at 18 degrees C. In comparison, apical membrane permeability at 37 degrees C to the weak acids, valeric acid and acetic acid, were 1.39 +/- 0.11 x 10(-2) cm/s (n = 4) and 6.93 +/- 0.11 x 10(-3) cm/s (n = 4), respectively. The activation energy for NH3 permeation was 15.0 +/- 1.0 kcal/mol (17.5 degrees C-37.5 degrees C). In the presence of the membrane fluidizing agents, heptanol or chloroform, NH3 permeability increased in a dose-dependent manner. Heptanol (15 mM) significantly decreased the activation energy for NH3 permeation to 4.4 +/- 0.6 kcal/mol, P less than 0.001. The carboxyl reactive agent (1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide metho-p-toluensulfonic acid 1 mM), aminoreactive agents (4,4'-diisothiocyanostilbene-2,2'-disulfonic acid 50 microM; picrylsulphonic acid 1 mM), the sulphydryl reactive agent (p-chloromercuriphenylsulfonic acid 1 mM), and the nonspecific membrane protein cleaving agent pronase (1 mg/ml) had no effect on the NH3 influx. The results suggest that NH3 permeates the plasma membrane of MDCK cells via a lipid pathway.

PH of cerebrospinal fluid in the cisterna Magna and on the surface of the choroid plexus of the 4th ventricle and its effect on ventilation in experimental disturbances of acid base balance. Transients and steady states.

In cats anesthetized with chloralose urethane, the arterial pH and the pH either in the cisterna magna or on the surface of the choroid plexus of the 4th ventricle as well as the tidal volume, expiratory CO2 partial pressure and arterial pressure were continuously recorded. Transients and steady states were observed after the inhalation of CO2, and the i.v. injection of HCl, NaHCO3, NH4Cl, and (NH4)2CO3. 1. pH on the surface of the choroid plexus follows changes in arterialpco2 almost instantaneously. 2. Injection of HCl into the blood is followed by a transient increase in endtidalpco2 and at the same time by a transient decrease of pH on the surface of the plexus. 3. After i.v. injection of NH4Cl and (NH4)2CO3 an abrupt increase of pH on the surface of the choroid plexus is observed indicating instantaneous permeation of NH3 from the blood into the CSF. This is in agreement with the distribution theory of the early phase of NH4Cl acidosis proposed by the authors in an earlier paper. 4. If the pH is measured in the cisterna magna all reactions are much slower but are in the same direction. 5. In the steady state of respiratory acidosis, the change of pH on the surface of the choroid plexus is less than that of the blood. 6. In metabolic acidosis and alkalosis only minimal—if any—changes of pH on the surface of the choroid plexus can be demonstrated, indicating that the regulation of plexus pH in these instances is very accurate. 7. In respiratory as well as in metabolic disturbances it would seem from the observed data that even in the first few minutes some bicarbonate exchange between the blood and the CSF occurs. 8. The increase of bicarbonate concentration in the CSF after i.v. injection of ammonium salts is mainly the result of the NH3 entering the CSF and reacting with H2CO3.