Amounts Of Alkali Metal Ions Research Articles

Highly dispersed Pt clusters within ZSM-5 stabilized by alkali metal ions and Al sites for partial methane oxidation

Zeolite is an ideal material to encapsulate nanoparticles and avoid metal aggregation, but it is challenging to achieve a high degree of metal dispersion inside zeolite. In this work, the Na+ reagent was introduced to synthesize Pt@S-1 and Pt@ZSM-5 to explore the effect of Al sites and alkali metal ions on dispersion of Pt nanoparticles. The properties of four catalysts were characterized by XRD, TEM, CO-TPR, TG and FT-IR, and the effects of alkali metal ions were analyzed combined with POM test results. The introduction of a certain amount of alkali metal ions in Pt@ZSM-5 catalyst consumed part of the hydroxyl group to form stable Pt-Ox(OH)yNa active species, which further improves the stability and dispersity of platinum nanoparticles and promotes the activity of partial oxidation of methane. This stabilization strategy can be extended to other porous materials encapsulating metal nanoparticles.

Dielectric property and polarization mechanism of sodium silicate glass in GHz–THz range

Glass is a candidate of dielectric materials for high-frequency communication technologies, and it is important to clarify the dielectric function of glass in GHz–THz range. In this study, the complex permittivities of silica glass and sodium silicate glasses were measured at 0.5–15 THz using terahertz time-domain spectroscopy and terahertz spectroscopic ellipsometer systems. The dielectric permittivity and loss of silica glass were extremely low in the GHz band, whereas those of sodium silicate glasses were relatively high in the GHz band. The dielectric dispersion at frequencies lower than 9 THz became larger with increasing Na content, and the dispersion greatly affected the dielectric permittivity and loss in the GHz band. Molecular dynamics simulations indicated that vibrations and migrations of Na ions occur in the frequency range of GHz to THz, and the dielectric dispersion at frequencies below 9 THz is due to the vibrations and migrations of Na ions, which are easily moved by an electric field. These results suggested that glass materials with a low amount of alkali metal ions are required when glass materials are applied as a high-frequency dielectric material.

Mechanism studies for adsorption and extraction of soluble sodium from bauxite residue: Characterization, kinetics, and thermodynamics

Bauxite residue contains a certain amount of alkali metal ions, among which sodium ions are predominant and have a great impact on its application performance. In this paper, a series of sodium ion adsorbents with different Al contents were prepared based on the structural characteristics of NASICON-type materials to study the effect on sodium ion adsorption and regeneration adsorption performance. The results showed that the adsorbent with 40% Al had the best adsorption rate (95.6%). The adsorbents were characterized by SEM, XRD, Raman spectroscopy, TG-DSC, XPS and N2 adsorption-desorption, and the results showed that the adsorbents had a stable three-dimensional network structure. The adsorption isotherm models, adsorption kinetics and adsorption thermodynamics were discussed. The adsorption process followed the Langmuir isotherm model and pseudo-second-order kinetic model and was a spontaneous exothermic reaction. In addition, the adsorption mechanism was also discussed; this mechanism involved the participation of carbon-oxygen bonds and electrostatic interactions during adsorption. Desorption and regeneration experiments demonstrated that the adsorbent had excellent reusability, with an adsorption rate of 88.82% after three cycles. This study effectively solves the problem of sodium ion disposal in waste liquid after bauxite residue dealkalization to a certain extent, alleviating the environmental pollution caused by subsequent waste liquid discharge. Additionally, the later application of sodium ions can "turn trash into treasure". This study not only provides a new route for the separation of sodium ions in bauxite residue but also has great significance both from an environmental perspective and from a resource recovery perspective.

Enhancing the photovoltaic performance of planar heterojunction perovskite solar cells by doping the perovskite layer with alkali metal ions

Doping the perovskite layer with a small amount of alkali metal ions can enhance the photovoltaic efficiency of perovskite solar cells.

Ion induced promotion of activity enhancement of mesoporous manganese oxides for aerobic oxidation reactions

Inverse micelle templated mesoporous manganese oxide (University of Connecticut mesoporous material, UCT-1) and ion promoted mesoporous manganese oxides (UCT-18-X, X=Mg2+, Ca2+, K+, Na+ and Cs+) having trace amount of alkali metal ions as promoters with tunable porosity and crystallinity were synthesized. The synthesis was based on the use of inverse micelles as soft templates and unique NOx chemistry as established for recently discovered UCT materials. The materials were tested for selective aerobic alcohol oxidation and the catalytic activity followed the order of UCT-1<UCT-18-Mg<UCT-18-Ca<UCT-18-K<UCT-18-Na<UCT-18-Cs. The catalytic activity was correlated to the promoter ion induced increase in basicity of the materials. The retention of an amorphous structure, low reducibility, and the effects of lattice oxygen are other key factors responsible for the enhanced catalytic activity. The UCT-18-Cs catalyst was found to oxidize various alcohols to corresponding aldehydes and ketones selectively (100% selectivity) with very high conversion (as high as 100%). The UCT-18-Cs also exhibited solvent free green oxidation of 1.3.5-trimethylbenzene to yield 3,5-dimethylbenzoic acid and (3,5-dimethylphenyl)methyl ester with >90% conversion and 90% selectivity for the acid and 9% selectivity for the ester.

Determination of Au and Pt in titanate nanotube catalysts by photon activation analysis

This study demonstrated the determination of Au and Pt concentrations in titanate nanotube-supported (abbreviated as TNT-supported) metal catalysts by photon activation and their catalytic activity with respect to metal concentration. An 18MV medical accelerator was used as photon source to activate the metals and generate radionuclides for gamma-ray spectroscopic analysis. Two TNT-supported metal catalysts, namely Au/NaTNT and Pt/MTNT (M=Na+ and Cs+), were prepared and the Au and Pt concentrations and the respective loading efficiencies were determined. The detection sensitivities with respect to the photon activated radionuclides were estimated to select the most sensitive gamma rays for the determination of Au and Pt concentrations. The loading efficiency for Au/NaTNT decreased with increasing Au concentration prepared, while it was almost 100% for Pt loading in Pt/MTNT of various prepared Pt concentrations. The Au/NaTNT containing 2.53wt% of Au effectively oxidized CO at a much lower reaction temperature than the lower concentration ones. For cinnamaldehyde hydrogenation reaction, the catalytic activity of Pt/TNT with different Pt loadings followed the order of 2.9>2.3>0.9>0.5wt%. This photon activation technique, with minus interfering radionuclides in the gamma-ray spectra and induced radioactivities in the samples, is perfectly suited to the determination of metal concentrations in TNT-supported catalysts, that might contain considerable amounts of alkali metal ions.

Reactions of Metal Salts and Alkali Metal Nitrates. Role of the Metal Precursors and Alkali Metal Ions in the Resulting Phase of Zirconia

Zirconia powders are prepared by reaction of a zirconium precursor with an alkali metal nitrate. The major part of the reactions takes place before the melting points and then the reactions go slowly to completion at 450°C in the molten salts. The roles of the precursor and the alkali metal ion are discussed considering the reaction between two precursors, octahydrated zirconium oxychloride and zirconium tetrachloride, and two nitrates, LiNO3 and NaNO3, and some resulting physico-chemical differences. The obtained zirconia powders contain very small amounts of alkali metal ions which act as stabilizing agent. Their effect on the balance tetragonal–monoclinic ZrO2 depends upon the homogeneity of their distribution which is related to their ability to diffuse inside the bulk of particles and their polarizing power when located mainly on the surface.

Polynuclear nickel hexacyanoferrates: monitoring of film growth and hydrated counter-cation flux/storage during redox reactions

Abstract An electrochemical quartz crystal microbalance (EQCM) was employed to monitor directly the growth of nickel(II) hexacyanoferrate(III) (NiHCNFe) films on gold substrates during electrodeposition as well as a result of sol-gel aggregation in colloidal nickel ferricyanide solutions used for modification. Frequency changes due to mass changes of the gold/crystal working electrode were correlated with cyclic voltammetric (CV) data. Evidence is also provided for the sorption of counter-cations (Li+, Na+ and K+), and associated water molecules, during redox reactions of the film. There is a strict relationship between the amount of alkali metal ions incorporated into the film during reduction, or excluded from the film during oxidation, and the frequency changes during EQCM measurements. The amount of solvent (H2O) transferred and sorbed in the NiHCNFe film reflects the degree of hydration of the investigated counter-ions. Anions also seem to participate in NiHCNFe electrochemistry, but their role is much less pronounced.

Effect of alkali metal ions on gel formation in the 12‐hydroxystearic acid/soybean oil system

AbstractIt has been known that 12‐hydroxystearic acid (12HSA) forms a thermoreversible gel with a fibrous associated network in organic solvents. Mechanically durable gels were induced by the addition of small amounts of alkali metal ions, which can be supplied in the form of alkali metal salts of 12HSA (abbreviated as 12HS‐M), even at a lower concentration range of gelling agent than with 12HSA alone. The structure of the networks was investigated by infrared spectrometry (IR), circular dichroism (CD) and scanning electron microscopy (SEM). The experiments were carried out over a total concentration range of 0.1≈4.0 wt/vol% of 12HSA and 12HS‐M in soybean oil. 12HS‐Na showed more effective gel forming power than any other alkali metal ions. The molar ratio of 12HSA/12HS‐Na for obtaining optimal gel forming effect was 100:1. The intensity of the absorption bands of the IR spectra, due to the hydrogen‐bonded hydroxyl groups, remained constant regardless of the amount of added 12HS‐Na. A remarkable molar ellipticity decrease was observed with an increase in the concentration of 12HS‐Na, although the maximum wavelength of the CD spectrum, originating from the chirality of 12HSA, remained constant. By SEM observation, linearly extended fibrils were observed with the addition of 12HS‐Na. These results suggest that the mechanical trengthening of the gel by alkali metal ions is due to alteration of the dispersed state of the helically grown fibrous crystals of 12HSA.

Synsedimentary volcanic-ash-derived illite tonsteins in Late Permian coal-bearing formations of southwestern China

Illite claystones (tonsteins) of Late permian coal-bearing formations are well developed and extensively distributed in southwestern China. Over the past decades it has been recognized that they are synsedimentary volcanic ash-falls in origin (altered tuff beds), based on the data derived from the comprehensive investigations on their stratigraphic and geographic distribution, petrographic types, chemical composition, accessory-mineral assemblage, as well as on their morphological characteristics. Recently, mineralogical and petrological identifications and X-ray diffraction analyses on these peculiar tonsteins further suggest that they can be classified mainly into three categories based on their clay-mineral constitution: kaolinitic, kaolinitic-illitic (transitional type), and illitic. As coal partings in most cases, these different types of tonsteins show a distinct zonal distribution on a regional scale. Their mineral constitution is profoundly modified by the combined effects of many factors during deuterogenic diagenesis, as indicated by the variation in volatile-component percentage (VM) of the adjacent coal seams (VM is calculated on a combustible-component basis). Those tonsteins intercalated in coal with a VM > 10% are dominated by kaolinite. But they contain increasing amount of illite at the expense of kaolinite when VM of coal decreases from 10% to 8%. When VM declines to less than 8% the clay minerals in these tonsteins are almost entirely illite with some sort of accompanying chloritization. It is clear that, from a regional point of view, the variation in clay-mineral constitution of these tonsteins is in response to the continual and progressive change in geological processes. In addition to the temperature and pressure conditions, the existence of a certain amount of alkali-metal ions and ferrous ions in solution is one of the controlling factors.

Ion-exchange on synthetic zeolites in non-aqueous ammonia solutions of alkali metal nitrates

The ion-exchange on synthetic Na zeolites, 4A and 13X, in non-aqueous ammonia solutions of alkali metal nitrates have been investigated. When the ion-exchange was carried out in non-aqueous ammonia solutions of alkali metal nitrates, it was found that ammonia was adsorbed into zeolites as the ion-exchange reaction occurred and a greater amount of alkali metal ions were introduced in zeolites compared with to those exchanged in aqueous solutions. The results showed the formation of a new type of inclusion complex, in which ammoniated alkali metal ions are introduced and nitrate ions are co-included.

Coprecipitation of alkali metal ions with calcium carbonate

The coprecipitation of alkali metal ions (Li +, Na +, K + and Rb +) with calcium carbonate has been studied experimentally and the following results have been obtained: 1. (1) Alkali metal ions are more easily coprecipitated with aragonite than with calcite. 2. (2) The relationship between the amounts of alkali metal ions coprecipitated with aragonite and their ionic radii shows a parabolic curve with a peak located at Na + which has approximately the same ionic radius as Ca 2+. 3. (3) However, the amounts of alkali metal ions coprecipitated with calcite decrease with increasing ionic radius of alkali metals. 4. (4) Our results support the hypothesis that 4.1. (a) alkali metals are in interstitial positions in the crystal structure of calcite and do not substitute for Ca 2+ in the lattice, but 4.2. (b) in aragonite, alkali metals substitute for Ca 2+ in the crystal structure. 5. (5) Magnesium ions in the parent solution increase the amounts of alkali metal ions (Li +, Na +, K + and Rb +) coprecipitated with calcite but decrease those with aragonite. 6. (6) Sodium-bearing aragonite decreases the incorporation of other alkali metal ions (Li +, K + and Rb +) into the aragonite.

Polarographic study of xylenol orange

In neutral medium the ring carbonyl group of xylenol orange is reduced in two one-electronsteps at a dropping mercury electrode. Step I is nearly reversible, but step II strongly irreversible. The half-wave potentials of both steps depend on pH, for the products of reduction, the dye radical formed in step I and the OH group produced in step II, behave as acids. From the E 1/2 vs. pH dependence, the p K of the dye radical is found to be 9.5, that of the hydroxy compound 5.6. On progressive acidification the height of step II continuously decreases, while that of step I increases. In solutions with pH<2, only a single (according to logarithmic analysis) one-electron, but overall (according to coulometry) two-electron step results. The ratio i I/ i II for the two steps increases when larger amounts of alkali metal ions are added. The exaltation of the first wave at the expense of wave II is explained by an acid-dependent dismutation of the dye radical formed during the first one-electron step.

Polarographic study of xylenol orange

In neutral medium the ring carbonyl group of xylenol orange is reduced in two one-electronsteps at a dropping mercury electrode. Step I is nearly reversible, but step II strongly irreversible. The half-wave potentials of both steps depend on pH, for the products of reduction, the dye radical formed in step I and the OH group produced in step II, behave as acids. From the E 1/2 vs. pH dependence, the p K of the dye radical is found to be 9.5, that of the hydroxy compound 5.6. On progressive acidification the height of step II continuously decreases, while that of step I increases. In solutions with pH<2, only a single (according to logarithmic analysis) one-electron, but overall (according to coulometry) two-electron step results. The ratio i I / i II for the two steps increases when larger amounts of alkali metal ions are added. The exaltation of the first wave at the expense of wave II is explained by an acid-dependent dismutation of the dye radical formed during the first one-electron step.

Dielectric and Anelastic Effects in Inorganic Glasses

THE dielectric properties of inorganic glasses in alternating fields are usually described in terms of the complex dielectric constant where e′ is the real part and e″ is the imaginary part or dielectric loss. The values of e′ and e″ are usually obtained from measurements of the capacitance and resistance of a disk shaped specimen fitted with metal electrodes. If the value of Cp/Co (where Cp is the equivalent parallel capacitance and Co is the capacitance with a vacuum between the electrodes) is plotted against log ω (where ω is the angular frequency), then, in the audiofrequency range and with blocking electrodes (for example, gold or platinum), a curve of the form shown in Fig. 1 is usually obtained with glasses containing appreciable amounts of alkali-metal ions.

Positive Ion Contamination on Metal Surfaces

Alkali metal, positive ion, contamination on metal surfaces contained in borosilicate glass envelopes has been studied for various gas atmospheres up to 100 torr. Positive ion desorption phenomena have been observed in ambient gases which are essentially similar to those obtained in the in-vacuo and sputtering experiments of Bills and Evett. Mass spectrometer examination confirmed the results of Bills and Evett, Riddock and Leck and of Bradley that the dominant ion was K+ with lesser amounts of Na+. Particularly heavy contamination by K+ was observed in the presence of O2. In the extreme case, direct vapor phase condensation of alkali metal contamination may be observed. The results differ from those of Riddock and Leck in that the amount of alkali metal ions desorbed from a W surface after extended gas discharge saturated at 0.03 monolayer coverage.