Effect of hydroxyl and nitrate ions on the sorption of ammonium ions by sulphonic cation exchangers

The sorption of ammonium ions and ammonia by the H+ form of sulphonic acid cation exchangers Amberlite 252, Lewatit 2629 and Relite C 360 from a solution containing NH₄NO₃ in the range of 0 to 0.214 equ/L and NH₃ in the range of 0.353 to 0 equ/L was investigated to establish the possibility of their application for the recovery of ammonium from caustic condensate generated in nitrogen fertilizer production. Breakthrough and elution curves were obtained, determining the concentration of ammonium with Nessler's reagent. The sorption of ammonium and ammonia depends on the concentration ratio of ammonia to ammonium nitrate [NH₃]/[NH₄NO₃]. On decreasing [NH₃]/[NH₄NO₃], the concentration ratio of hydroxyl to nitrate ions [OH⁻]/[NO⁻₃] and the effluent pH prior to NH⁺₄ breakthrough also decrease. This results in a decrease in the NH⁺₄ sorption because of a deficiency in the neutralization of hydrogen ions released (ordinary cation-exchange process). Thus, adverse circumstances create an unfavorable medium for NH⁺₄ removal from the caustic condensate. Maximum sorption of NH⁺₄ is attained at [NH₃]/[NH₄NO₃] ∼1.2. A further decrease in [NH₃]/[NH₄NO₃] is followed by a significant decrease in the effluent pH, which leads to an increase in the concentration of protonated sulphonic acid groups (-SO₃H), resulting in a decrease in the ion-exchange ability of the cation exchangers under investigation with respect to NH⁺₄ removal. The concentration (g/L) of NH₄NO₃ in the eluate from the cation-exchanger regeneration, carried out using 0.7 bed volumes (BV) of 20% HNO₃, amounts to 136.7 for Relite C 360, 119.5 for Lewatit K 2629 and 96.7 for Amberlite 252. The content of undamaged beads after 100 cycles (each cycle comprises saturation with caustic condensate, containing ammonia and ammonium, successive regeneration with 20% nitric acid and washing) is from 97 to 99.8%. Resistance to boiling in 20% HNO₃ solution is from 97 to 99.8%. These are applicable for the recovery of NH₄NO₃ from the caustic condensate in the nitrogen fertilizers production, preventing economic damage and environmental contamination from nitrogen compounds.     

Influences of pH on the structure,morphology and dielectric properties of bismuth titanate ceramics produced by a low-temperature self-combustion synthesis without an additional fuel agent

Bismuth titanate (BIT) ceramics were prepared by incorporating low-temperature self-combustion synthesis and pH modification. The pH value of the initial precursor was adjusted to 3, 5 and 7 by the addition of ammonium hydroxide (NH₄OH) with different amount. The reaction between ammonium ions (NH₄⁺) and nitrate ions (NO₃^?) induced the formation of ammonium nitrate (NH₄NO₃), in turn to favor the combustion by enhancing the decomposition rate. Excessive hydroxyl ions (OH^?) at higher pH value dominated the chelating of the metal carboxylate and the metal ions, resulting in a strong hybridization between bismuth (Bi) and oxygen (O), and also the suppression of the independent volatility of Bi and bismuth oxide (Bi₂O₃). Such conditions contributed to the formation of pure BIT via the low-temperature self-combustion synthesis without the use of an additional fuel agent. A BIT ceramic with high relative density (91.35%) that exhibited a high dielectric constant of ～340 and a low dissipation factor ～0.028 was obtained by the synthesis method at the neutral condition. Furthermore, it offers ability for the use in high temperature applications up to 675 °C.     

Experimental and modeling of the electrodialytic and dialytic treatment of a fly ash containing Cd,Cu and Pb

A one-dimensional model is developed for simulating the electrodialytic and dialytic treatment of a fly ash containing cadmium, copper and lead. Two experimental systems have been used, a column of ash and a stirred ash suspension. The movement of Cd, Cu and Pb has been modeled taking into account the diffusion transport resulting from the concentration gradients of their compounds through the membranes and boundary layers and the electromigration of their ionic, simple and complex species during the operation. The model also includes the electromigration of the non-contaminant most important principal ionic species in the system, H⁺ and OH⁻, proceeding of the electrolysis at the electrodes, Ca²⁺, CO₃ ⁼, SO₄ ⁼, etc. proceeding from the ash and Na⁺ and NO₃ ⁻, or citrate and ammonium ions incorporated as electrolyte solutions and/or as agent solution during the ash treatment. The simulation also takes into account that OH⁻ generated on the cathode, during the electrodialytic remediation, is periodically neutralized by the addition of nitric acid in the cathode compartment. The anion and cation-exchange membranes are simply represented as ionic filters that preclude the transport of the cations and anions, respectively, with the exception of H⁺ which is retarded but pass through the anion-exchange membrane.     

Root GS and NADH-GDH Play Important Roles in Enhancing the Ammonium Tolerance in Three Bedding Plants

Ammonium is a paradoxical nutrient because it is more metabolically efficient than nitrate, but also causes plant stresses in excess, i.e., ammonium toxicity. Current knowledge indicates that ammonium tolerance is species-specific and related to the ammonium assimilation enzyme activities. However, the mechanisms underlying the ammonium tolerance in bedding plants remain to be elucidated. The study described herein explores the primary traits contributing to the ammonium tolerance in three bedding plants. Three NH₄⁺:NO₃⁻ ratios (0:100, 50:50, 100:0) were supplied to salvia, petunia, and ageratum. We determined that they possessed distinct ammonium tolerances: salvia and petunia were, respectively, extremely sensitive and moderately sensitive to high NH₄⁺ concentrations, whereas ageratum was tolerant to NH₄⁺, as characterized by the responses of the shoot and root growth, photosynthetic capacity, and nitrogen (amino acid and soluble protein)-carbohydrate (starch) distributions. An analysis of the major nitrogen assimilation enzymes showed that the root GS (glutamine synthetase) and NADH-GDH (glutamate dehydrogenase) activities in ageratum exhibited a dose-response relationship (reinforced by 25.24% and 6.64%, respectively) as the NH₄⁺ level was raised from 50% to 100%; but both enzyme activities were significantly diminished in salvia. Besides, negligible changes of GS activities monitored in leaves revealed that only the root GS and NADH-GDH underpin the ammonium tolerances of the three bedding plants.     

Genome-Wide Identification and Expression Analysis of AMT and NRT Gene Family in Pecan (Carya illinoinensis) Seedlings Revealed a Preference for NH4+-N

Nitrogen (N) is a major limiting factor for plant growth and crop production. The use of N fertilizer in forestry production is increasing each year, but the loss is substantial. Mastering the regulatory mechanisms of N uptake and transport is a key way to improve plant nitrogen use efficiency (NUE). However, this has rarely been studied in pecans. In this study, 10 AMT and 69 NRT gene family members were identified and systematically analyzed from the whole pecan genome using a bioinformatics approach, and the expression patterns of AMT and NRT genes and the uptake characteristics of NH₄⁺ and NO₃⁻ in pecan were analyzed by aeroponic cultivation at varying NH₄⁺/NO₃⁻ ratios (0/0, 0/100,25/75, 50/50, 75/25,100/0 as CK, T1, T2, T3, T4, and T5). The results showed that gene duplication was the main reason for the amplification of the AMT and NRT gene families in pecan, both of which experienced purifying selection. Based on qRT-PCR results, CiAMTs were primarily expressed in roots, and CiNRTs were majorly expressed in leaves, which were consistent with the distribution of pecan NH₄⁺ and NO₃⁻ concentrations in the organs. The expression levels of CiAMTs and CiNRTs were mainly significantly upregulated under N deficiency and T4 treatment. Meanwhile, T4 treatment significantly increased the NH₄⁺, NO₃⁻, and NO₂⁻ concentrations as well as the Vmax and Km values of NH₄⁺ and NO₃⁻ in pecans, and Vmax/Km indicated that pecan seedlings preferred to absorb NH₄⁺. In summary, considering the single N source of T5, we suggested that the NH₄⁺/NO₃⁻ ratio of 75:25 was more beneficial to improve the NUE of pecan, thus increasing pecan yield, which provides a theoretical basis for promoting the scale development of pecan and provides a basis for further identification of the functions of AMT and NRT genes in the N uptake and transport process of pecan.     

Influence of nitrogen nutrition and metabolism on ammonia volatilization in plants

Barley (Hordeum vulgare L. cv. Golf) was grown in solution culture with controlled nitrogen availability in order to study the influence of nitrogen nutrition on ammonia emission from the leaves. Ammonia emission measured in cuvettes connected to an automatic NH₃ monitor was close to zero for nitrate grown plants but increased to 0.9–1.3 nmol NH₃ m^-2 leaf area s^-1 after 3–5 days of ammonium nutrition. Increasing concentrations from 0.5 to 10 mM NH₄ ⁺ in the root medium increased NH₃ emission from the shoots, root glutamine synthetase activity and NH₄ ⁺ concentrations in apoplast, xylem sap and bulk tissue, while apoplastic pH values decreased.Inhibition of glutamine synthetase in nitrate grown barley plants by addition of 1 mM methionine sulfoximine (MSO) to the root medium caused ammonia emission to increase 5 to 10-fold after 2–3 hours. At the same time shoot tissue ammonium concentrations started to increase. Addition of an inhibitor of photorespiration, 1 mM pyrid-2-yl hydroxymethane sulfonate (HPMS) reduced this increase in ammonia emission showing a relation between NH₃ emission and photorespiration.Oil seed rape (Brassica napus L. cv. Global) plants grown at 3 different nitogen levels (2N, 4N and 7N) in a sand/soil mixture showed increasing NH₃ compensation points with increasing N level. This increase was highly correlated with increasing NH₄ ⁺ concentrations in the leaf apoplast and total leaf tissue. The NH₃ compensation points could be succesfully predicted on basis of the pH and NH₄ ⁺ concentration in the leaf apoplast.     

Hydrazine Radiolysis by Gamma-Ray in the N2H4–Cu+–HNO3 System

Radiolysis of chemical agents occurs during the decontamination of nuclear power plants. The γ-ray irradiation tests of the N₂H₄–Cu⁺–HNO₃ solution, a decontamination agent, were performed to investigate the effect of Cu⁺ ion and HNO₃ on N₂H₄ decomposition using a Co-60 high-dose irradiator. After the irradiation, the residues of N₂H₄ decomposition were analyzed by Ultraviolet-visible (UV) spectroscopy. NH₄⁺ ions generated from N₂H₄ radiolysis were analyzed by ion chromatography. Based on the results, the decomposition mechanism of N₂H₄ in the N₂H₄–Cu⁺–HNO₃ solution under γ-ray irradiation condition was derived. Cu⁺ ions form Cu⁺N₂H₄ complexes with N₂H₄, and then N₂H₄ is decomposed into intermediates. H⁺ ions and H^● radicals generated from the reaction between H⁺ ion and e_aq⁻ increased the N₂H₄ decomposition reaction. NO₃⁻ ions promoted the N₂H₄ decomposition by providing additional reaction paths: (1) the reaction between NO₃⁻ ions and N₂H₄^●+, and (2) the reaction between NO^● radical, which is the radiolysis product of NO₃⁻ ion, and N₂H₅⁺. Finally, the radiolytic decomposition mechanism of N₂H₄ obtained in the N₂H₄–Cu⁺–HNO₃ was schematically suggested.     

Behavior of Microporous Nitroprussides in Presence of Ammonia

The behavior of microporous nitroprussides in the presence of ammonia, both in anhydrous and hydrated states, was studied using ammonia adsorption isotherms and IR, Mössbauer and XRD techniques. In their anhydrous state these materials behave as a zeolite for ammonia adsorption, however when structural water is present a decomposition process was observed. The crystallization or adsorbed water is used by ammonia to form NH⁺ ₄ and OH^–, creating basic conditions where the structural building unit [Fe(CN)₅NO] loses the NO group to form a pentacyano complex. This leads to the formation of mixed salts, M(NH₄)[Fe(CN)₅]·xH₂O. For ferrous nitroprusside the formed OH^– ion competes with the complex anion for the iron(2+) cation which is removed, then oxidized and finally observed as a ferric oxyhydroxide, FeOOH.     

Kinetics of Ion Formation in the Volumetric Reaction of Methane with Air

The formation of ions in the volumetric reaction of methane and hydrogen with air is analyzed. In methane–air mixtures, the highest concentrations are observed for NO⁺, NO₃ ^–, CO₃ ^–, CO₄ ^–, OH^–, and NO₂ ^– ions. In hydrogen–air mixtures, maximum concentrations are characteristic for NO⁺, OH^–, H₃O⁺, O^–, and O₂ ^– ions. In both rich and lean mixtures after ignition there is a long time interval during which the ion concentrations are far from equilibrium. The duration of this interval and the ion concentrations in it depend on the initial parameters of the mixture and the air–fuel ratio. Key words: volumetric reaction of methane with air, ion-molecular reactions, kinetics, ions.     

Glass electrode response to lithium ion activity. Effects of sodium,potassium, ammonium,tetramethyl-, tetraethyl-, and tetra-n-butyl ammonium ions in water and 50% water-ethanol mixture

Competing effects of Na⁺, K⁺, NH⁺₄ and three quaternary ammonium ions, Me₄N⁺, Et₄N⁺, and n-Bu₄N⁺, on the response of a lithium ion-selective glass electrode have been investigated in water and 50% water-ethanol mixture. The results have been analysed according to an ion-exchange model developed earlier for solutions in propylene carbonate. It appears that the effects of the two groups of cations can be rationalized in terms of the relative ease (or difficulty) or desolvation experienced by a lithium ion, in their presence, prior to its incorporation into the glass phase.     

Aerated membrane‐attached biofilm reactor as an effective tool for partial nitrification in pretreatment of anaerobic ammonium oxidation (ANAMMOX) process

BACKGROUND: A laboratory‐scale membrane aeration bioreactor was employed to treat synthetic ammonium‐rich wastewater to yield an appropriate NH₄⁺/NO₂^? ratio for anaerobic ammonium oxidation (ANAMMOX). The main objectives of this study were to steadily obtain 50% partial nitrification in batch experiments, to evaluate the effects of aeration and to identify the dominant bacterial community of the biofilm for partial nitrification. RESULTS: Some of the ammonium in the synthetic wastewater was partially nitrified. A suitable NH₄⁺/NO₂^? ratio (1:1 to 1:1.3) for the ANAMMOX process was obtained after 24 h. The dissolved oxygen (DO) level in the treated water was very low (below 0.6 mg L^?1). Both the appropriate NH₄⁺/NO₂^? ratio and the low DO level make this bioreactor an ideal pretreatment system for ANAMMOX. In addition, a molecular biotechnology method was applied to prove that the ammonia‐oxidizing bacteria dominated the biofilm. CONCLUSION: This system achieved surprising cost savings in the aeration process compared with traditional aeration systems. The combination of this system with the subsequent ANAMMOX process has great potential as a favorable short‐cut in the treatment of ammonium‐rich wastewater. Copyright © 2007 Society of Chemical Industry     

Nutrient Leaching in Undisturbed Cores of an Acidic Sandy Podosol Following Simultaneous Potassium Chloride and Di-Ammonium Phosphate Application

In south-east Queensland, Australia, extensive areas of sandy soils (Podosols) with shallow (<1 m) watertables are used for exotic pine tree production. Despite concerns that surface-applied fertilisers (di-ammonium phosphate (DAP) and potassium chloride (KCl)) may be contributing to a decline in local groundwater quality, published information on nutrient leaching in these Podosols is scarce. Large (0.3 m i.d. ×0.85 m long) undisturbed soil cores were intermittently leached with deionised water following a single surface application of KCl in combination with DAP. Potassium was applied at rates (equivalent on a surface area basis) of 0 (K0), 50 (K50), 100 (K100) and 300 (K300) kg K⁺/ha, and DAP was applied at a rate equivalent to 50 kg P ha⁻¹. Applied ions appeared in the leachate very quickly after surface application, and reactive ions leached at the same rate as non-reactive ions. This behaviour was attributed to preferential soil–water flow, and limited ion sorption. About 30, 35, 100 and 25 percent of the applied K⁺, phosphorus (P), chloride (Cl⁻) and ammonium (NH₄⁺) was leached from the soil cores. Cation exchange was the major mechanism responsible for K⁺ and NH₄⁺ retention, although nitrification may have also contributed to NH₄⁺ losses. Findings indicate that significant amounts of surface-applied fertiliser ions can potentially be rapidly leached below the tree root-zone, and into the underlying groundwater. Immobile water regions were estimated to comprise nearly 50% of the soil–water. Intermittent leaching resulted in secondary concentration peaks along the trailing edge of the ion breakthrough curves (BTCs). This was attributed to diffusion of solute from immobile water regions into mobile water regions during periods of no-flow.     

Development and application of a simultaneous measurement method for gaseous ammonia and particulate ammonium in ambient air

Ammonia gas is one of the precursors contributing to the formation of secondary particulate ammonium via reactions with atmospheric acids, such as sulfuric and/or nitric acids, which are present in ambient air. In this study, a new instrument that is suitable for measuring ammonia gas and fine particulate ammonium (PM_2.5 NH₄⁺) concentrations simultaneously under ambient conditions was developed. A wetted frit sampler was connected in the back of a counter-current flow tube (CCFT) sampler, and the NH₃ gas and PM_2.5 NH₄⁺ samples were collected by CCFT and wetted frit samplers, respectively. An air sample was drawn through the samplers at a flow rate of 1.0 dm³ min^?1 and an absorption water flow rate of 120 mm³ min^?1. Then, the ammonium that formed in the absorption solution was detected by the indophenol method using a continuous flow analysis system. The estimated detection limits were 43 and 49 ng m^?3 for ammonia gas and PM_2.5 NH₄⁺, respectively. Notably, the ammonia gas was collected on the CCFT sampler with a collection efficiency of 98.5%, but most of the PM_2.5 NH₄⁺ passed through it and was captured on the wetted frit sampler with a collection efficiency of approximately 100%. The present method was applied to measure NH₃ gas and PM_2.5 NH₄⁺ at two urban sites: Osaka, Japan and Ho Chi Minh City, Vietnam. It was found that the simultaneous measurement method performed very well and that the measured concentrations were comparable with those obtained with the annular denuder method.

Copyright © 2016 American Association for Aerosol Research     

Amperometric determination of ammonium ions with a microbial sensor

A sensor for NH⁺₄ ions has been developed, which consists of immobilized micro-organisms (Bacillus subtilis, Pseudomonas aeruginosa, Trichosporon cutaneum) in combination with an electrochemical transducer. This sensor is based on the measurement of acceleration of respiration after addition of NH⁺₄ in the presence of glucose. The physiological background of this signal and its connection with NH⁺₄ ion uptake and/or metabolism is discussed. The response time of the sensor is about 5.10 s for NH⁺₄ ions. A linearity was observed between 0.005 and 0.15 mmol dm^?3 NH⁺₄ ions. The sensitivity of the sensor remained almost constant for 12 days. The sensor was used to determine NH⁺₄ ions in a microbial fermentation broth.     

A Review on the Role of Bicarbonate and Proton Transporters during Sperm Capacitation in Mammals

Alkalinization of sperm cytosol is essential for plasma membrane hyperpolarization, hyperactivation of motility, and acrosomal exocytosis during sperm capacitation in mammals. The plasma membrane of sperm cells contains different ion channels implicated in the increase of internal pH (pH_i) by favoring either bicarbonate entrance or proton efflux. Bicarbonate transporters belong to the solute carrier families 4 (SLC4) and 26 (SLC26) and are currently grouped into Na⁺/HCO₃⁻ transporters and Cl⁻/HCO₃⁻ exchangers. Na⁺/HCO₃⁻ transporters are reported to be essential for the initial and fast entrance of HCO₃⁻ that triggers sperm capacitation, whereas Cl⁻/HCO₃⁻ exchangers are responsible for the sustained HCO₃⁻ entrance which orchestrates the sequence of changes associated with sperm capacitation. Proton efflux is required for the fast alkalinization of capacitated sperm cells and the activation of pH-dependent proteins; according to the species, this transport can be mediated by Na⁺/H⁺ exchangers (NHE) belonging to the SLC9 family and/or voltage-gated proton channels (HVCN1). Herein, we discuss the involvement of each of these channels in sperm capacitation and the acrosome reaction.     

Mechanistic aspects of the K+ ion selective electrode based on valinomycin-PVC

The mechanism of ion selective electrode membranes based on valinomycin + KBPh₄ in plasticized PVC is discussed in the light of recent impedance studies. In a typical membrane the K⁺ is largely present as K⁺ val − BPh⁻₄ ion pairs. The transport number for K⁺ val is ∼ 0.87 whilst that for BPh₄ is ∼ 0.13. At the aqueous KCl membrane interface the exchange current for K⁺ typically exceeds 30 μA cm⁻². There is no evidence for any significant take up of water by these membranes, either as water molecules or as water globules containing OH⁻.     

Formation of no and NH4 + ions in the low-temperature peripheral zone of a flame

It is found that charged nitrogen oxides are formed not only in the front and the high-temperature combustion-product zone of a Bunsen-type flame but also in the relatively cold external region of the flame close to the burner nozzle. The peripheral NO⁺ is formed from atmospheric oxygen drawn in from outside the flame. The concentration of NO⁺ ions increases as the mixture is enriched with fuel. Possible pathways by which the peripheral NO⁺ ions may appear are considered. It is suggested that their precursor is the NH₄ ⁺ ion formed from ammonia.Karaganda. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 3, pp. 111–115, May–June, 1993.     

Sorption of Aniline by Montmorillonite

Sorption of aniline by montmorillonite was studied by infra-red, X-ray diffraction and differential thermal analysis methods. The amount of aniline sorbed and the type of bonding depend upon the interlayer cations: anilinium, H⁺- and Al³⁺- give anilinium aniline ions, NH₄⁴-ammonium aniline ions, alkalis and alkaline earths except Cs are bonded to aniline through water bridges and transition metal cations are coordinated to aniline partly directly and partly through water bridges. Sorption does not occur in the complete absence of water.     

Effects of Z-value on physicochemical and biological properties of β-SiAlONs ceramics

This study evaluated the effects of different Z-values on the physical, chemical, and biological properties of β-SiAlON ceramics. Increasing the Z-value of the β-Si₃N₄ solid solution's main phase resulted in the replacement of Si–N bonds with Al–O bonds. The number of columnar crystals decreased, bulk density increased, and porosity decreased, thus transforming the fine-particle microstructure of β-Si₃N₄ into the columnar structure of β-SiAlON. The compressive strength increased, which facilitated sintering at 1500 °C without sintering auxiliaries. H⁺ and OH⁻ ions in deionized water broke the covalent bonds on the β-SiAlON surface, thereby forming new Si–OH, Al–OH, and N–H bonds on the β-SiAlON surface and producing SiO₄⁴⁻, AlO₂⁻, and NH₄⁺ groups in the solution. Increasing the soaking time changed the compositions of ionized H⁺ and OH⁻ ions, thus increasing the pH. MC3T3-E1 cells were cultured on the β-SiAlON surface, and it was observed that the increase in the Z-value of β-SiAlON had no influence on cell adhesion and spreading, but it may slightly suppress cell proliferation at high Z-values. At low Z-values, the low AlO₂⁻ concentration helps promote osteogenic differentiation and mineralized nodule formation. Thus, β-SiAlON ceramics possess excellent physical, chemical, and biological properties and are considered excellent bone-repairing materials.