Presence Of Ammonium Ions Research Articles

A New Mechanism for the Inhibition of SA106 Gr.B Carbon Steel Corrosion by Nitrite in Alkaline Water.

The purpose of this study was to investigate the composition of oxide films formed on SA106 Gr.B carbon steel in nitrite solutions at 35 °C for 1000 h. The product of the reduction of nitrite during the corrosion inhibition process was also examined. The X-ray photoelectron spectroscopy results revealed that a thin Fe3O4 film was formed and ammonium ions were adsorbed on the outermost surface of the oxide film. The presence of ammonium ions was also demonstrated by ion chromatography. These results indicate that nitrites are reduced to ammonium ions, which in turn promotes the formation of the protective Fe3O4 film.

Corrosion and Protection of Synthetic Intermetallic Compounds and Bulk Aluminum Alloy Under Simulated Atmospheric Conditions

Aluminum alloy 7075-D6 is often used for aircraft parts and is thus exposed to atmospheric conditions. AA7075-D6 is susceptible to corrosion due to high Zn, Mg and Cu contents in the form of various intermetallic particles having more or less noble electrochemical potential regarding the matrix (1,2). Usually, corrosion of aluminum alloys is simulated using solutions of various concentrations of chloride ions. However, aircraft are exposed to atmospheric conditions, where Cl- is not the only pollutant. Namely, in industrial and urban areas, major inorganic species such as ammonium (NH4 +), sulfate (SO4 2−) and nitrate (NO3 −) ions are found in the form of NH4NO3 and (NH4)2SO4 (or NH4HSO4). Therefore, these should also be considered because they represent corrosive agents for many aluminum alloys (3). Corrosive conditions may be thus better simulated by the so-called dilute Harrisonʼs solution (DHS) (0.35 wt.% (NH4)2SO4 + 0.05 wt.% NaCl), which in addition to Cl− also contains SO4 2− and nitrate NO3 − reflecting the environmental and atmospheric conditions. The first part of our study was focused on the corrosion of AA7075-T6 in DHS and comparison with NaCl solution. In addition to AA7075-T6, major intermetallic compounds (IMCs) synthesized in bulk form to represent the major intermetallic constituents (Al2Cu, Al2CuMg, Al7Cu2Fe and MgZn2) were also investigated. For IMCs, electrochemical measurements were performed using a microcell, and a standard cell was used to study the bulk alloy.Bulk AA7075-T6 was less susceptible to corrosion in DHS than in chloride solution stemming from the beneficial presence of sulfate ions and lower chloride concentration. The susceptibility of IMCs to corrosion in DHS increased as Al2Cu < Al7Cu2Fe < Al2CuMg < MgZn2 due to the increased dissolution of Mg in the presence of ammonium ions. The relative nobility of IMCs was determined based on the galvanic current density.In the second part of our study, we addressed the role of cerium salts in the corrosion protection of AA7075-T6 in DHS. Cerium salts are non-toxic compounds and demonstrate corrosion inhibition by inhibiting redox reactions by forming a protective cerium-containing precipitated conversion layer (4). Ce salts acted as inhibitors for the alloy during 14-day testing, forming a Ce hydroxide layer. The degree of protection depended on the type of anion, being the highest for Ce acetate. For the IMC, however, inhibition by Ce salts did not occur during short measurements, indicating the importance of galvanic interaction with the alloy matrix in the inhibition, which was confirmed by long-term measurements of the alloy. Micro and macro approaches give essential information on the galvanic relation between the IMPs and Al matrix under different conditions in the presence and absence of different cerium salts or other inhibitions (5). This brought about valuable information concerning corrosion inhibition and synergism with other ions in the corrosion media. Figure. Schematic presentation of (a) effect of various anions (NH4 +, SO4 2 - and Cl-) in dilute Harrison’s solution, and (b) effect of cerium(III) cations and corresponding anions (Cl-, NO3 - and CH3COO-) on the surface of AA7075-T6. Corrosion inhibition due to the deposition of the cerium layer is presented in (c). The precipitation of Ce species proceeds mainly on the cathodic sites and progressively spreads over the alloy surface; meanwhile, the Mg and Al are slowly dissolved from the anodic sites.

Novel Coumarin Derivatives as Potential Urease Inhibitors for Kidney Stone Prevention and Antiulcer Therapy: From Synthesis to In Vivo Evaluation.

The presence of ammonium ions in urine, along with basic pH in the presence of urease-producing bacteria, promotes the production of struvite stones. This causes renal malfunction, which is manifested by symptoms such as fever, nausea, vomiting, and blood in the urine. The involvement of urease in stone formation makes it a good target for finding urease enzyme inhibitors, which have the potential to be developed as lead drugs against kidney stones in the future. The documented ethnopharmacology of coumarin 2-one against bacterial, fungal and viral strains encouraged us to synthesize new derivatives of coumarins by reacting aromatic aldehydes with 4-aminocoumarin. The synthesized compounds (2a to 11a) were evaluated for their antimicrobial, in vitro, and in silico properties against the urease enzyme. The study also covers in vivo determination of the synthesized compounds with respect to different types of induced ulcers. The molecular docking study along with extended MD simulations (100 ns each) and MMPBSA study confirmed the potential inhibitory candidates as evident from computed ∆Gbind (3a = -11.62 and 5a = -12.08 Kcal/mol) against the urease enzyme. The in silico analyses were augmented by an enzymatic assay, which revealed that compounds 3a and 5a had strong inhibitory action, with IC50 of 0.412 µM (64.0% inhibition) and 0.322 µM (77.7% inhibition), respectively, compared to standard (Thiourea) with 82% inhibition at 0.14 µM. Moreover, the most active compound, 5a, was further tested in vivo for antiulcer activity by different types of induced ulcers, including pyloric ligation-, ethanol-, aspirin-, and histamine-induced ulcers. Compound 5a effectively reduced gastric acidity, lipid peroxidation, and ulceration in a rat model while also inhibiting gastric ATPase activity, which makes it a promising candidate for ulcer treatment. As a result of the current research, 3a and 5a may be used as new molecules for developing potent urease inhibitors. Additionally, the compound 3a showed antibacterial activity against Staphylococcus aureus and Salmonella typhimurium, with zones of inhibition of 41 ± 0.9 mm and 35 ± 0.9 mm, respectively. Compound 7a showed antibacterial activity against Staphylococcus aureus and Salmonella typhimurium, with zones of inhibition of 30 ± 0.8 mm and 42 ± 0.8 mm, respectively. These results prove that the synthesized compounds also possess good antibacterial potential against Gram-positive and Gram-negative bacterial strains.

Evaluation of Ni–B alloy electroplated with different anionic groups

In order to study the effects of the main nickel salt on the electroplated nanocrystalline Ni–B alloy coating, the deposition rates, surface morphology, crystallinity, grain sizes, hardness, and corrosion resistance of the Ni–B films electrodeposited with plating baths containing separately nickel sulfate (NS) and nickel sulfamate (NSA) under various temperatures and current densities were compared. Under all conditions, the NSA bath system offered higher deposition rates and lower B contents than the NS counterpart because of the formation of Ni-ammonium complex, which can be adsorbed faster than nickel ions. These two groups of coatings had similar surface morphology and crystallinity under all plating conditions except for those plated with the NS bath system at 60 °C, wherein significant changes in surface texture and preferred crystal orientation as well as an abrupt increase in grain size occurred. The coating hardness was optimized by reducing the grain size and increasing the boron content because of the combined effects of grain refinement strengthening and solid solution strengthening. The differences between the two main salt systems can be explained by the presence of ammonium ions in the NSA bath, which not only increased the deposition rate but also maintained the preferred orientation in Ni (111) at high temperature. Our results indicate that, under high current density and high temperature operation conditions, the NSA main salt plating system is a more favorable option for obtaining higher quality Ni–B alloy coatings.

Morphological control of CaCO3 superstructures in seawater: Insights into Ca-source anion influence and formation mechanism

This work provides crucial insights into the crystallization and morphogenesis of CaCO3 polymorphs in seawater at elevated temperatures. Using Ca source anions as a controlling factor, we modify the crystallization of CaCO3 and demonstrate that stable and intricate particle morphologies of CaCO3, such as hexagonal bipyramidal, disks, and twin structures, can be generated in seawater without surfactants. The synthesis of CaCO3 was accomplished through a direct hydrothermal method utilizing water-soluble Ca salts (calcium chloride, calcium nitrate, and calcium acetate) as Ca source and urea as a carbonate source. Depending on the specific source anions used, various morphological changes were observed. The CaCO3 prepared with the nitrate source yields vaterite as the major polymorph with hexagonal bipyramidal morphology. Pseudohexagonal prisms of aragonite were the primary product obtained with calcium acetate as the source. In contrast, chloride ions yielded vaterite and aragonite depending on the reaction temperature and time. The purity of CaCO3 prepared with seawater was > 94 % regardless of the Ca source. We observe that the phase formation follows the order of gypsum-vaterite-aragonite with an increase in hydrothermal reaction time. Further, we propose the formation mechanism of vaterite hexagonal bipyramidal and aragonite pseudohexagonal prism superstructures where directional aggregation of particles occurs in the presence of ammonium ions and seawater solvent. These findings, obtained through the exploration of seawater and different Ca sources, offer a comprehensive understanding of how source anions influence the selective formation of CaCO3 polymorph and its morphological tuning. This information can be applied to tailor the synthesis of CaCO3 for specific applications.

Corrosion of Synthetic Intermetallic Compounds and AA7075-T6 in Dilute Harrison’s Solution and Inhibition by Cerium(III) Salts

This study addresses the behavior of an aluminum alloy and its components in conditions simulating the presence of atmospheric salts. The corrosion of synthetic intermetallic compounds (IMCs) Al2Cu, Al2CuMg, Al7Cu2Fe, MgZn2, and bulk aluminum alloy 7075-T6 was studied in dilute Harrison’s solution (DHS, 0.35 wt% (NH4)2SO4 + 0.05 wt% NaCl). For IMCs, electrochemical measurements were performed using a microcell, and a standard electrochemical cell was used to study the bulk alloy. Separately measured cathodic and anodic potentiodynamic polarization curves were recorded, and prolonged immersion was characterized using electrochemical impedance spectroscopy. Samples were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Bulk AA7075-T6 was less susceptible to corrosion in DHS than in chloride solution stemming from the beneficial presence of sulfate ions and lower chloride concentration. The susceptibility of IMCs to corrosion in DHS increased in the order Al2Cu < Al7Cu2Fe < Al2CuMg < MgZn2 due to the increased dissolution of Mg in the presence of ammonium ions. The relative nobility of IMCs was determined based on the galvanic current density. Further, the possibility of using cerium chloride, nitrate and acetate salts as corrosion inhibitors in DHS was evaluated. Ce salts acted as inhibitors for the alloy during 14 d testing, forming a Ce hydroxide layer. The degree of protection depended on the type of anion, with acetate Ce salt giving the most efficient protection. For the IMC, however, inhibition by Ce salts did not occur during short measurements in the microcell, indicating the importance of galvanic interaction with the alloy matrix in the inhibition mechanism, which was confirmed by long-term measurements of the alloy.

Elimination of orthophosphate from synthetic leachate using adsorption on bentonite clay

The composition of leachates is very variable and rich in toxic compounds, which requires treatment before discharge into the natural environment in order to avoid their impact on the environment and/or human health and to comply with the requirements of regulatory discharge standards in the natural environment. Among the parameters indicating pollution by leachates, we have COD, BOD5, conductivity, pH, the presence of ammonium ions, nitrite, nitrate, chloride, orthophosphate, etc. This study presents the results of synthetic leachate orthophosphate adsorption tests on bentonite clays. For the determination of the orthophosphate concentration in the synthetic leachate, before and after adsorption, we applied the method of Ultra-Violet adsorption spectroscopy. The adsorption capacity of bentonite, the amount needed and the removal efficiency were determined. The orthophosphate adsorption yield on bentonite reaches up to 32.6 % for 5 g/L of bentonite stirred for 4 hours and exceeds 39,19 % after 24 hours of stirring.

Quantifying Sphingomyelin in Dairy through Infusion-Based Shotgun Mass Spectrometry with Lithium-Ion-Induced Fragmentation.

Quantifying sphingomyelin (SM) species by infusion-based mass spectrometry (MS) is complicated by the presence of isobaric phosphatidylcholine (PC) species, which generate a common m/z 184 product ion in the presence of ammonium ions as a result of the phosphocholine headgroup. Lithium ion adducts of SM undergo a selective dehydration [Li + H2O + (CH3)3NC2H4PO4] with a corresponding neutral loss of -207 Da. This neutral loss was employed to create a SM-selective method for identifying target species, which were quantitated using multiple reaction monitoring (MRM). SM-selective fragments in MS3 were used to characterize the sphingosine base and acyl chain. These methods were used to identify 50 individual SM species in bovine milk ranging from SM 28:1 to SM 44:2, with d16:1, d17:1, d18:1, d19:1, and d20:1 bases, and acyl fatty acids ranging from 10 to 25 carbons and 0-1 desaturations. Spiked SM standards into milk had a recovery of 99.7%, and endogenous milk SM had <10% coefficient of variation for both intra- and interday variability, with limits of detection of 1.4-5.55 nM and limits of quantitation of 11.8-178.1 nM. This MS-MRM method was employed to accurately and precisely quantify SM species in dairy products, including bovine-derived whole milk, half and half, whipping cream, and goat milk.

Biocatalytic 3D Actuation in Liquid Crystal Elastomers via Enzyme Patterning.

Liquid crystal elastomers (LCEs) are stimuli-responsive materials that undergo large shape transformations after undergoing an order-disorder transition. While shape reconfigurations in LCEs are predominantly triggered by heat, there is a considerable interest in developing highly specific triggers that work at room temperature. Herein, we report the fabrication of biocatalytic LCEs that respond to the presence of urea by covalently immobilizing urease within chemically responsive LCE networks. The hydrogen-bonded LCEs developed in this work exhibited contractile strains of up to 36% upon exposure to a base. Notably, the generation of ammonia by immobilized urease triggered a disruption in the supramolecular network and a large reduction of liquid crystalline order in the films when the LCEs were exposed to urea. This reduction in order was macroscopically translated into a strain response that could be modulated by changing the concentration of urea or exposure time to the substrate. Local control of the mechanical response of the LCE was realized by spatially patterning the enzyme on the surface of the films. Subsequent exposure of enzymatically patterned LCE to urea-triggered 3D shape transformations into a curl, arch, or accordion-like structure, depending on the motif patterned on the film surface. Furthermore, we showed that the presence of salt was critical to prevent bridging of the network by the presence of ammonium ions, thereby enabling such macroscopic 3D shape changes. The large actuation potential of LCEs and the ability to translate the biocatalytic activity of enzymes to macroscopic 3D shape transformations could enable use in applications ranging from cell culture, medicine, or antifouling.

Enhanced Pyrophyllite Flotation Performance Using Sodium Oleate as an Anionic Collector in the Presence of Ammonium Ion

Enhanced Pyrophyllite Flotation Performance Using Sodium Oleate as an Anionic Collector in the Presence of Ammonium Ion

Rapid evaluation of ammonium in different rain events minimizing needed volume by a cost-effective and sustainable PDMS supported solid sensor

The presence of ammonium ion in rainwater is due to atmospheric processes which involve its scavenging from gas phase and particulate matter. The fractionated samplings of rainwater can provide information about these processes and their potential sources. However, only a low sample volume may be available, which constrained the analysis in general and more particularly in situ mode. For minimizing this limitation, this work proposes a polydimethylsiloxane (PDMS)-salicylate sensor that produces a color change. The embedding of solid reagents into PDMS was optimized. Good analytical characteristics (analysis time of 10 min, sample volume of 500 μL, limit of detection 0.03 μgmL−1) were obtained. Furthermore, other features of the method such as carbon footprint, equipment cost, residues, toxicity and safety have to be taken into account to be assessed according to the Green Analytical Chemistry approach. In this sense, the hexagon tool was employed for comparing the proposed sensor with methods based on the same reaction as well as with general methods for the ammonium analysis in water (using luminol, ion selective electrode, Nessler and modified Roth method). The proposed method based on PDMS-salicylate sensor stands out from all the others by its sustainability, particularly, in terms of low carbon footprint, residues and cost. The method was applied to fractionated samplings in a suburban site (Galicia, Northwestern Spain) and a higher contribution of the rainout process was observed. When long-duration rain events were analyzed, a relationship between the sampling time and ammonium concentration could indicate a loss of ammonium ion over time.The research focuses on developing an innovative PDMS-sensor, for monitoring ammonium determination in rainwater under wide conditions (scavenging process).

Optimum Operating Conditions for the Removal of Phosphate from Water Using of Wood-Branch Nanoparticles from Eucalyptus camaldulensis.

A batch bio-sorption experiment was conducted on Eucalyptus camaldulensis Dehnh. wood-branch in the form of woody sawdust nanoparticles (nSD-KF) to evaluate their potential efficiency as phosphate bio-sorption capacity. The operating parameters of phosphate bio-sorption including contact time, initial concentration, pH, temperature, dosage, size, competing ion, and the possible mechanisms responsible for phosphate removal from water were investigated. The nSD-KF were green-synthesized by ball mill grinder and phosphate solutions with various concentrations were performed. The results revealed that the maximum adsorption capacity (qmax) value of nSD-KF was 50,000 µg/g. In addition, the removal efficiency of nSD-KF significantly increased with the increase of initial phosphate concentration, contact time, temperature, and dosage. However, it decreased with the increase of pH and in double-system solution with the presence of ammonium ions. At the application study, the nSD-KF successfully removed 87.82% and 92.09% of phosphate from real agricultural wastewater in a batch experiment and in a column experiment, respectively. Adsorption efficiency of nSD-KF for phosphate increased after the first and second regeneration cycles, but it decreased after the third and fourth cycles. The poor to moderate phosphate desorption from nSD-KF sorbent indicates the stability of phosphate bound to nSD-KF materials. Regardless, biodegradability of nSD-KF-loaded phosphate is possible, and it will be a good source of phosphate to a plant when added to the agricultural soil as a supplemental application of fertilizer. In conclusion, nSD-KF could be considered as a promising lignocellulosic biomaterial used for the removal of phosphate from waters as bio-sorption process.

Biological nutrient recovery from human urine by enriching mixed microalgal consortium for biodiesel production

Utilization of waste resources is necessary to harness the long-term sustainability of algal technology. The study focused on the use of human urine as the basic nutrient source for culturing native microalgal consortium and further optimized the process parameters using response surface methodology. A full factorial, central composite rotatable design (CCRD) with three variables: urine concentration (1–10% vol of urine/vol of distil water [%v/v]), pH (6.5–9) and light intensity (50–350 μmolphotonsm−2sec−1) was used to evaluate the microalgal biomass and lipid content. Results indicated that at 95% confidence limits, the selected factors influence the biomass and lipid productivity. The maximum biomass productivity of 211.63 ± 1.40 mg l−1 d−1 was obtained under optimized conditions with 6.50% v/v of urine, pH of 7.69 and at light intensity of 205.40 μmolphotonsm−2sec−1. The lipid content was found to increase from 18.96 ± 1.30% in control media to 26.27 ± 1.94% under optimal conditions. The interactive effect of variables over the microalgal biomass and lipid content has also been elucidated. The data obtained were comparable to the BG11 media (control). Optimized diluted urine media in the presence of ammonium ions and under limited nitrate showed better lipid yields. Significant lipid biomolecules were detected in the algal oil extracts obtained from the diluted urine media characterized by Fourier transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance (NMR). Gas chromatography-mass spectrometry (GCMS) revealed the presence of several monounsaturated and polyunsaturated fatty acids in the transesterified algal oil. Such studies would aid in technically realizing the field scale cultivation of microalgae for biofuels.

Single-stranded DNA structural diversity: TAGGGT from monomers to dimers to tetramer formation.

DNA quadruplex structures have emerged as novel drug targets due to their role in preventing abnormal gene transcription and maintaining telomere stability. Trapped Ion Mobility Spectrometry-Mass Spectrometry (TIMS-MS), combined with theoretical modeling, is a powerful tool for studying the kinetic intermediates of DNA complexes formed in solution and interrogated in the gas phase after desolvation. A TAGGGT ssDNA sequence was purchased and studied in 10 mM ammonium acetate using nanospray electrospray ionization (nESI)-TIMS-MS in positive and negative ion mode. Collisional cross section (CCS) profiles were measured using internal calibration (Tune Mix). Theoretical structures were proposed based on molecular dynamics, charge location and geometry optimization for the most intense IMS bands based on the number of TAGGGT units, adduct form and charge states. A distribution of monomeric, dimeric and tetrameric TAGGGT structures were formed in solution and separated in the gas phase based on their mobility and m/z value (e.g., [M + 2H]+2 , [2M + 3H]+3 , [M - 2H]-2 , [2M - 3H]-3 , [4M + 4H]+4 , [4M + 3H + NH4 ]+4 , [4M + 2H + 2NH4 ]+4 and [4M + H + 3NH4 ]+4 ). The high mobility resolution of the TIMS-MS analyzer permitted the observation of multiple CCS bands per molecular ion form. Comparison with theoretical candidate structures suggests that monomeric TAGGGT species are stabilized by A-T and G+ -G interactions, with the size of the conformer influenced by the proton location. In the case of the TAGGGT quadruplex, the protonated species displayed a broad CCS distribution, while six discrete conformers were stabilized by the presence of ammonium ions (n = 1-3). This is the first observation of multiple conformations of TAGGGT complexes (n = 1, 2 and 4) in 10 mM ammonium acetate. Candidate structures with intramolecular interactions of the form of G+ -G and traditional A-T base pairing agreed with the experimental trends. Our results demonstrate the structural diversity of TAGGGT monomers, dimers and tetramers in the gas phase beyond the previously reported solution structure, using 10 mM ammonium acetate to replicate biological conditions.

Fabrication of high thermal conductive shape-stabilized polyethylene glycol/silica phase change composite by two-step sol gel method

Tetraethyl silicate (TEOS) and polyethylene glycol (PEG) were used to prepare inorganic–organic polyethylene glycol (PEG)/silica (SiO2) nanocomposites by a controllable sol–gel method. Two kinds of counter ions were used to help gelatinize step by step. The presence of metal ions accelerates hydrolysis of SiO2 sol and the presence of ammonium ions allows the system to gel rapidly. PEG forms a shell-and-core structure with SiO2 and this composite shows excellent thermal stability. Moreover, system contains respectively Calcium ions (Ca2+), magnesium ions (Mg2+), aluminum ions (Al3+) were studied. It is very interesting that PEG with different metal ions formed different strength of the chemical force between PEG and metal ions change due to presence of different metal ions. As the force increased, the thermal conductivity increased from 0.25 W m−1 k−1 to 0.41 W m−1 k−1 and the phase change latent heat of the composites increased from 46.99 to 91.05 J/g, without affecting the phase transition temperature.

Effects of liquid post-column addition in electrospray ionization performance in supercritical fluid chromatography–mass spectrometry

In supercritical fluid chromatography coupled to atmospheric pressure ionization mass spectrometry (SFC-MS), the use of a make-up post-column is almost mandatory to avoid analyte precipitation, especially when using low percentage of modifier (<5%) in the mobile phase. Due to the specific nature of gaseous CO2, the tuning of the make-up conditions in electrospray becomes an important factor and can be used to tune analyte sensitivity. Neither a dilution effect (loss of signal) nor a relevant degradation of chromatographic performances is observed with the addition of a make-up at various flow-rates, up to 0.7mL/min. From supercritical conditions (1mL/min 40°C, 150bar) to gaseous state (room temperature, atmospheric pressure), the CO2 expands around 430 times, contributing to almost 5% of the nebulizing process. In positive mode, the presence of ammonium ions either in the mobile phase or in the make-up did significantly increase the MS signal, even at basic apparent pH. The ionization performance of electrospray is influenced by the acidic buffer power of the carbon dioxide, and was found to be restricted in the apparent pH range of 3.8–7.2 in the various conditions investigated. This may challenge sensitive detection in negative mode, as illustrated for bosentan. The use of DMSO as make-up additive (up to 30%) showed a simplification of the full scan spectrum regarding the adducts. Finally, the optimization of make-up composition leads to an enhancement up to a factor of 69 on the electrospray MS response signal, for the SFC-SRM/MS analysis of HIV protease inhibitors in plasma extracted from Dried Plasma Spots.

Photoluminescence from amino functionalized graphene quantum dots prepared by electrochemical exfoliation method in the presence of ammonium ions

This study elucidates how the nitrogen functionalities affect the UV-visible absorption and photoluminescence (PL) emission of N-modified graphene quantum dots (NGQDs).

Sorption of Heavy Metals by Bed Silts in the Presence of Ammonium Ions

Sorption of Heavy Metals by Bed Silts in the Presence of Ammonium Ions

Corrosion of Mg alloy in the presence of ammonium ion. Evidence of hydride sub-products

Corrosion of AZ31 Mg alloy was systematically investigated by different experimental approaches in the presence and in the absence of NH4+. Remarkable reactivity of Mg/NH4+ system was manifested by copious evolution of hydrogen over a dark corrosion film, associated to active deprotonation of complex Mg hydrides, more likely bridged {Mg2+(AlH4−)2Mg2+(H−)2} complexes covered by a skin of MgO. Metastability of hydride phases is favored in the presence of species that alter the equilibrium dissociation of water, such as NH4+ and SO42−. Chemical recombination of hydrogen atoms of oxidic Mg hydrides is proposed as the kinetically determinant process.

Effects of ammonium ions from the anolyte within bio-cathode microbial fuel cells on nitrate reduction and current density

This study was to determine the effects of the ammonium ion in the anolyte of the two-chamber bio-cathode MFC, which uses nitrate ions as the final electron acceptor, on the nitrate reduction and the current density. The ammonium nitrogen mass transfer coefficient was 3 × 10−6 cm/s and the diffusivity was 6 × 10−8 cm2/s through Nafion 117 under abiotic conditions, with the circuit disconnected. When the TCBC-MFC was operated at 96.6 ± 11.2 mg/L of SCODcr in the anode chamber and 37.9 ± 2.8 mg/L of nitrate nitrogen in the cathode chamber at an external resistance 100 Ω, the analytical denitrification rate was being 7.89 ± 0.78 g/m3d in the presence of ammonium ions and 3.07 ± 0.26 g/m3d in the absence of ammonium ions. The current density was 176.1 ± 31.7 mA/m2 when NH4+-N was present in the anolyte and 28.2 ± 19.4 mA/m2 without NH4+-N. Thus, it was determined that the ammonium ions in the anolyte were promoted electron movement, which increased the denitrification rate to twice that in the ammonium-free system.