Molar Ratio Of Na Research Articles

A Simple Process for the Recovery of Rare Earth Elements and Iron from Sulfuric Acid Leaching Solution of NdFeB Magnets by Double Salt Precipitation

ABSTRACT Recovery of rare earth elements (REEs) from spent NdFeB magnets is important to meet the increasing demand for magnets and high-tech applications. In general, pretreatments of spent NdFeB magnets are necessary to recover REEs such as Nd, Pr, and Ce from the magnets. In this work, a simple process was proposed to recover REEs without any pretreatment of NdFeB magnets by using precipitation of REE(III) double salt. The correlations among several variables on the precipitation of REE(III) double salt were investigated by using synthetic solutions such as the molar ratio of Na(I) and sulfuric acid to Nd(III), the concentration of Nd(III) and Fe(III). The REES and iron present in NdFeB magnets were completely dissolved in 2 M H2SO4 solution at room temperature. The dissolved REE(III) ions were then directly separated by precipitation of double salt when Na2SO4 was added at 80°C. After REEs precipitation, the addition of iron powder to the filtrate at room temperature reduced Fe(III) to Fe(II) and removed a small amount of Cu(II) and Co(II) by cementation. Then Fe(II) and Na2SO4 were separated by precipitation of Fe(OH)2 when solution pH was adjusted to 8. The conditions for the precipitation of Nd(III) double salt were thermodynamically verified. Mass balance of continuous experiments indicated that it was possible to recover REEs and iron with high purity by the proposed process in this work.

Selective removal of Sr(II) from saliferous radioactive wastewater by capacitive deionization

90Sr-containing radioactive wastewater during Fukushima nuclear accident (FNA) aroused extensive consideration for its disposal. Massive coexisted Na+ ions seriously inhibited Sr2+ removal, aggravating the expenditure of radioactive wastewater treatment. Herein, a chestnut shell derived porous carbon material modified with aryl diazonium salt (ADS) of sodium 4-aminoazobenzene-4′-sulfonate (SPAC) was developed as capacitive deionization electrode for selective removal of Sr2+ from saliferous radioactive wastewater. Based on ADS modification, the Sr2+ electrosorption capacity of SPAC electrode was improved to 33.11 mg g−1 with fast ion removal rate of 2.89 mg g−1 min−1, comparing with only 16.10 mg g−1 before modification. The isothermal adsorption and kinetics by SPAC electrode fitted well with Langmuir and pseudo-second-order model, achieving a maximum Sr2+ electrosorption capacity of 58.21 mg g−1, superior cycling stability, and excellent charge efficiency (77.63%). Fascinatingly, the SPAC electrode exhibited superhigh Sr2+ selectivity of 70.65 against Na+ in Na+–Sr2+ mixed solution with molar ratio of Na+:Sr2+ as 20:1. Density functional theory (DFT) simulation, combining with electrochemical and spectral analyses, revealed that the high overlap of electron cloud between Sr2+ ion and anionic sulfonic group (–SO3-) provided SPAC with remarkable selectivity of Sr2+ ion, and illustrated the ion-swapping mechanism of Sr2+ selectivity.

Sulfur-encapsulated zeolite micromotors for the selective removal of cesium from high-salt water with accelerated cleanup times

Bubble-propelled sulfur-encapsulated NaX zeolite (S-NaX) micromotors were developed for the selective removal of cesium from high-salt conditions with accelerated cleanup times. NaX was first modified with sulfur to provide additional Lewis acid−base interactions with Cs+ for enhanced Cs+ selectivity, and then Pt was half-deposited on S-NaX for bubble propulsion via the catalytic decomposition of H2O2. The average velocity of the resulting S-NaX/Pt micromotors in 5 wt% H2O2 is 39.7 ± 17.1 μm/s, which is higher than that of a previously reported Cs adsorbent micromotor (35.4 μm/s). The Cs+ ion-exchange kinetics of the S-NaX micromotor is 1.32 times higher than that of the NaX micromotor in a 5 wt% H2O2 solution where the molar ratio of Na+ to Cs+ is 200, even though the sulfur in the S-NaX micromotor causes an adverse effect on the propulsion speed due to the sulfur poisoning effect. Moreover, the S-NaX micromotor in simulated groundwater also exhibited excellent Cs+ removal performance with distribution coefficient (Kd) values at least 3.2 times higher than those of the nonpropelled S-NaX and NaX micromotor, demonstrating the great potential for the treatment of radioactive Cs+-contaminated water.

Hydrogeochemical Processes Regulating the Groundwater Quality and its Suitability for Drinking and Irrigation Purpose in Parts of Coastal Sindhudurg District, Maharashtra

Abstract The hydrochemistry of groundwater samples from the northern part of coastal Sindhudurg district, Maharashtra, India, was studied with an aim to comprehend its suitability for domestic and irrigation use. Groundwater samples were collected from 66 dug wells distributed over the study area, during the month of November 2017. The results of the chemical analysis indicate that the groundwater is alkaline in nature and are mainly characterized by Ca+-Mg+2-HCO3–, Ca+-Mg+2-Cl– and Na+-Cl– facies. The molar ratios of Na+/Cl–>1, both Mg2+/Na+ and Ca2+/Na+ ratios <1, (Ca2+ + Mg2+)/ (SO42– + HCO3–) = 1 suggest that the rock-water interaction of silicates / schistose rocks (quartz, chlorite, amphibolites, schist etc.) and ion exchange reaction are the major controlling factors of groundwater chemistry. Lower molar ratios of Cl–/ HCO3–< 0.5, NO3-/Cl-<0.3 observed reflect freshwater regime. Three samples which are in proximity to the Arabian Sea, deduce the effect of secondary contributions (saline water and anthropogenic sources). In order to determine the probable sources of groundwater contamination, principal component analysis was also carried out. The first three principal components with eigen value 1 or more are responsible for 71.31 %, 12.38% and 8.32% of the total variance in the data set, indicating major role of groundwater-rock interaction and marginal saltwater intrusion effect in the study area. Groundwater quality index computed for drinking purpose indicate that about 96% of the water samples lie within the permissible limits stipulated by the World Health Organization and Bureau of Indian Standards, and fall under the good to excellent category, suggesting its suitability for drinking purpose in the area. Water quality index indicates that most of the water is of excellent to good quality for irrigation, except for a few coastal samples.

One-step synthesis of highly dispersed nanosheets of magadiite

By using the combination of PEG 300 (polyethylene glycol with average molecular weight of 300) and sodium salts, highly dispersed nanosheets of magadiite were directly obtained from hydrothermal synthesis. The total concentration of sodium ions(Na+/PEG 300), the crystallization time and the stirring speed are three key parameters that determine the dispersion of magadiite. As the molar ratio of Na+/PEG 300 was increased to 0.96 or above, highly dispersed nanosheets of magadiite were synthesized. By increasing the stirring speed, magadiite becomes more stable and its dispersity is greatly enhanced. Based on these results, a mechanism for the formation of dispersed magadiite has been proposed, in which “in situ delamination” was assumed.

Mineral transition of desilication products precipitated in synthetic sodium aluminate solution under atmospheric pressure

Abstract The liquor concentration, mineral proportion, crystal parameters and micro morphology of various desilication products (DSPs) precipitated in silica-supersaturated sodium aluminate solution at 95 °C under different reaction conditions were systematically researched. The DSPs formed under atmospheric pressure comprise amorphous phase, zeolite A, zeolite and sodalite, and the DSPs concentration and crystallinity increase with the increase of initial silica concentration, initial molar ratio of caustic Na 2 O to Al 2 O 3 ( α K ) and desilication duration. Decreasing the initial silica concentration, initial α K and increasing the desilication duration can reduce the proportion of zeolite A. The zeolite and sodalite are the stable DSPs, while the precipitation of zeolite A occurs at a high silica-supersaturated state in sodium aluminate solution. The DSPs are precipitated in the form of agglomerates, but the morphologies of various DSPs are quite different. Both the molar ratios of Na 2 O to Al 2 O 3 and SiO 2 to Al 2 O 3 in DSPs increase with the increasing desilication duration, resulting in the increase of the cell volumes of various DSPs. The precipitation sequence of DSPs under atmospheric pressure is: amorphous phase→zeolite A→zeolite→sodalite.

Na-Ga-Si type-I clathrate single crystals grown via Na evaporation using Na-Ga and Na-Ga-Sn fluxes.

Single crystals of a Na–Ga–Si clathrate, Na8Ga5.70Si40.30, of size 2.9 mm were grown via the evaporation of Na from a Na–Ga–Si melt with the molar ratio of Na : Ga : Si = 4 : 1 : 2 at 773 K for 21 h under an Ar atmosphere. The crystal structure was analyzed using X-ray diffraction with the model of the type-I clathrate (cubic, a = 10.3266(2) Å, space group Pm3̄n, no. 223). By adding Sn to a Na–Ga–Si melt (Na : Ga : Si : Sn = 6 : 1 : 2 : 1), single crystals of Na8GaxSi46−x (x = 4.94–5.52, a = 10.3020(2)–10.3210(3) Å), with the maximum size of 3.7 mm, were obtained via Na evaporation at 723–873 K. The electrical resistivities of Na8Ga5.70Si40.30 and Na8Ga4.94Si41.06 were 1.40 and 0.72 mΩ cm, respectively, at 300 K, and metallic temperature dependences of the resistivities were observed. In the Si L2,3 soft X-ray emission spectrum of Na8Ga5.70Si40.30, a weak peak originating from the lowest conduction band in the undoped Si46 was observed at an emission energy of 98 eV.

Synthesis and Characterization of Distorted Orthorhombic Type Na0.7MnO2 Cathode Material By Spray Pyrolysis

Because the lithium-ion batteries have characteristics of high capacity, high energy density, long cycle life and safety, lithium-ion batteries have been widely used as power sources for electric vehicles, portable electric device, and hybrid electric vehicles in the battery market. However, lithium resource is not abundant element and unevenly distributed in earth. Indeed, the price of lithium has dramatically surged due to commercialization of lithium batteries for power sources of vehicles and energy storage systems. In order to resolve the above problem, sodium-ion batteries using 3d - transition metals have been studied in earnest from 1980s. Sodium resource is possible to be compared with lithium resources as counterpart because sodium is one of the most opulent elements on the Earth. In addition, sodium is the second lightest and smallest alkali metal. Above all, intercalation chemistry of sodium is similar to lithium. For this reason, we decided to attempt to prepare distorted orthorhombic - Na0.7MnO2 based on Mn3+/4+ redox reaction synthesized by spray pyrolysis. Na0.7MnO2 powders were prepared by an ultrasonic spray pyrolysis method. Stoichiometric amounts of manganese nitrate tetra-hydrate and sodium nitrate as the starting materials were dissolved in distilled water at a molar ratio of Na:Mn of 0.7:1 at room temperature. The dissolved solution was added to a mixture solution of citric acid and sucrose. The resulting aerosol stream was introduced into a vertical quartz reactor heated to 400oC. The precursor powders were calcined from 1000 to 1300oC for 10h in a furnace under an air atmosphere at a heating rate of 5oC/min and then followed by slowly cooling to room temperature. The synthesized Na0.7MnO2 powders were identified by X-ray diffraction (XRD) with Cu kα radiation and analyzed by Rietveld refinement. The particle morphologies and size of the obtained precursors and powders were observed using scanning electron microscopy (SEM). Galvanostatic charge/discharge test was performed using a R2032-type coin cell. The electrochemical performances of Na0.7MnO2 were measured by using a constant charge-discharge rate of 9mAg-1 at voltages between 1.5 and 4.3V. Sodium layered oxide, Na0.7MnO2, with the distorted orthorhombic (space group:Cmcm) type structure was synthesized by an ultrasonic spray pyrolysis method and characterized as positive electrode for sodium batteries. The Na0.7MnO2 electrode delivered a high specific capacity of 228 mAhg-1 at 0.05C rate in the 1.5–4.3 V range. The capacity retention after 25 cycles is about 90% in the 1.5–4.3 V range. This reason of high capacity retention would be structural stability of the distorted orthorhombic Na0.7MnO2 electrodes during cycling. In order to confirm this reason, we conducted the in situ X-ray diffraction at first charge/discharge process. Furthermore, to understand the relationships between electrochemical properties and structural changes, cycled electrode were subjected to ex situ X-ray diffraction. Figure 1

Synthesis of ZSM-5 aggregates by a seed-induced method and catalytic performance in methanol-to-gasoline conversion

A seed-induced method was applied to synthesize a series of ZSM-5 aggregates using silicalite-1 (S-1) as seeds. The samples were characterized by several techniques and studied in the methanol-to-gasoline (MTG) conversion reaction in a continuous fixed-bed reactor. The results showed that the molar ratios of Na 2 O/SiO 2 and H 2 O/SiO 2 in the precursors had great effects on the physicochemical and catalytic properties. The ZSM-5 aggregates with the highest crystallinity, external surface areas, micropore volumes, mesopore volumes and small primary crystal and aggregate sizes, obtained with the molar composition of 0.12Na 2 O–1SiO 2 –0.02Al 2 O 3 –25H 2 O-0.01Seed in the precursor, exhibited the highest stability.

Isotopic transient studies of sodium promotion of Pt/Al2O3 for the water–gas shift reaction

The promotional effect of sodium on Pt/Al2O3 catalysts for the water–gas shift (WGS) reaction was investigated with operando FTIR during steady-state and isotopic transient experiments. The highest turnover frequency (TOF) promotion per surface Pt occurred on a 0.82wt.% Pt/Al2O3 catalyst with a 30:1molar ratio of Na:Pt. This catalyst exhibited a TOF of 0.35s−1 at 250°C and 7% CO, 11% H2O, 9% CO2, and 37% H2 compared to 0.43×10−2s−1 on Pt/Al2O3. Operando IR revealed that Na addition modifies CO adsorption on Pt to create more strongly bound, multiply-bonded CO species at 1768cm−1 and 1697cm−1 compared to predominantly linear CO on Na-free Pt/Al2O3 at 2060cm−1. Transient experiments with 12CO/13CO isotope switches showed that the number of carbon-containing active intermediates increased from less than 1% of the surface Pt for Na-free Pt/Al2O3 to nearly 100% of the surface Pt for 20Na:Pt/Al2O3, which indicates that only a small fraction of the Pt surface on the Na-free samples participates in the WGS reaction. From time-resolved IR spectra during transient WGS with 12CO/13CO and 12CO2/13CO2 isotope switches, we propose that surface formate species are spectators for all Na-promoted Pt/Al2O3 catalysts under these WGS conditions. The results suggest that Na promotes Pt/Al2O3 for WGS by modifying the local electronic properties of Pt and creating new H2O activation sites, which provide greater availability of surface OH/H species to react with nearly all CO on the metallic Pt surface through a non-formate pathway.

Flux growth of magnetoplumbite-type strontium ferrite single crystals with La–Co co-substitution

The Na2O flux method was successfully applied in the single crystal synthesis of the magnetoplumbite-type strontium ferrite with La–Co co-substitution (Sr1−xLaxFe12−yCoyO19), which is a familiar base material for commercial permanent magnets. The initial amount of Na2O flux was fixed in the molar ratio of Na/(Sr+La)=5.17. Composition analysis revealed discordance between La and Co concentrations (x>y) in the obtained crystals, indicating that the extra charge introduced by the Co2+ substitution for Fe3+ is not compensated by La3+ for Sr2+. In the present growth condition, the necessary amount of La is nearly twice that of Co (y/x≃0.55), suggesting valence instability of an appreciable amount of Fe3+ to Fe2+. Single crystalline magnetization measurements showed that the substitution markedly enhances the magnetic anisotropy and slightly raises the saturation magnetization. Remaining problems, which should be resolved before the experimental determination of the Co site occupation, are also discussed.

ChemInform Abstract: Crystal Structure of (Na0.70)(Na0.70,Mn0.30) (Fe3+,Fe2+)2Fe2+ (VO4)3, a Sodium‐, Iron‐ and Manganese‐Based Vanadate with the Alluaudite‐Type Structure.

AbstractThe title compound is prepared by several calcination steps of NaNO3, Mn, Fe, V2O5 in the molar ratio of Na:Mn:Fe:V = 2:2:1:3 (Pt crucible, 1030 K).

ChemInform Abstract: Crystal Structure of Type Alluaudite KNa5Mn3(MoO4)6.

AbstractKNa5Mn3Mo6O24 is prepared by solid state reaction of a mixture of Na2CO3, K2CO3, Mn(OAc)3, and (NH4)2Mo4O13 in the molar ratio of Na:K:Mn:Mo = 1:1:2:3 (porcelain crucible, 950 K, 3 weeks; cooling to 900 K at a rate of 5 K/d).

ChemInform Abstract: Crystal Structure of Type Alluaudite K0.4Na3.6Co(MoO4)3.

AbstractK0.4Na3.6Co(MoO4)3 is prepared by solid‐state reaction of Na2CO3, Co(NO3)2, K2CO3, and (NH4)2Mo4O13 in the molar ratio of Na:K:Co:Mo = 2:1:3:3 (porcelain crucible, 963 K, 2 weeks; cooling to 910 K at a rate of 5 °C/d).

Elemental and stable isotopic study of sweeteners and edible oils: Constraints on food authentication

Elemental concentrations and stable isotopic compositions of 41 sweeteners (syrups, honeys, and sugars) and 43 edible oils were determined to evaluate their potential as parameters for food authentication. The addition of as little as 10% of corn syrup to pure maple syrup can be detected using molar ratios of Na/(Na+K) and Na/(Na+Ca) for maple syrups. The detection of more than 15% adulterant in maple syrup and honey is also possible due to the 13‰ difference in carbon isotopic composition of C3 plants for authentic honeys and maple syrups (25.1±1.1‰) relative to the carbon isotopic composition of C4 plants for corn syrups and cane sugars (−11.4±0.8‰) as major adulterant agents. Nearly constant net oxygen (1.028±0.002) as well as hydrogen (0.974±0.005) isotope fractionation factors between honeys and average local meteoric waters from two areas, Kingston and Costa Rica, suggests that these isotope ratios of honeys are good candidates to authenticate their geographic locations. The net oxygen (1.03±0.001) as well as hydrogen (0.894±0.003) isotope fractionation factors between olive oils and local meteoric waters from different parts of Italy suggests that these isotope ratios are independent of the oil processing method and therefore can be used to trace geographic locations.

ChemInform Abstract: Quaternary Pnictides with Complex, Noncentrosymmetric Structures. Synthesis and Structural Characterization of the New Zintl Phases Na11Ca2Al3Sb8, Na4CaGaSb3, and Na15Ca3In5Sb12.

AbstractSingle crystals of the new title Zintl phases are prepared by solid state reactions from mixtures of the elements in the molar ratio of Na:Ca:M:Sb = 3:3:1:4 (M: Al, Ga, In) in sealed Nb containers (1173 K, 24 h).

ChemInform Abstract: Synthesis and Characterization of a New Quaternary Borate Na2Cs2Sr(B9O15)2 with the Unprecedented [B9O19]11‐ Group, Notation of 3 x (3:2Δ + T).

AbstractSingle crystals of the new title compound are prepared from a powder mixture of Na2CO3, Cs2CO3, SrCO3, and H3BO3 in the molar ratio of Na:Cs:Sr:B = 2:3:2:17 (Pt crucible, 750 °C, 7 d).

ChemInform Abstract: Thermoelectric Properties of p‐Type Semiconducting NaB5C with Hexaboride‐Type Structure, Compared to Layered MB2C2 (M: La, Ce).

AbstractNaB5C is prepared by solid state reaction of the elements in the molar ratio of Na:B:C = 6:5:1 (sealed boronated Ta tubes in evacuated quartz ampoule, 1000 °C, 6‐8 h) and densified by high‐pressure spark plasma sintering (923 K, 100 MPa, 90 min).

ChemInform Abstract: β‐Nb9VO25.

Abstractβ‐Nb9VO25 is prepared by a solid‐state reaction of Nb2O5, V2O5, and Na2CO3 in the molar ratio of Na:Nb:V = 3:6:1 (porcelain crucible, 1198 K, 1 week, slow cooling).

Morphological tuning and enhanced luminescence of NaEuF4 nano-/submicro-crystals

• NaEuF 4 nano-/submicro-crystals were prepared via hydrothermal process. • The pH and Cit 3− /Eu 3+ ratio have an important role in the growth of NaEuF 4 . • Enhanced luminescence was observed in NaEuF 4 spheres with smaller size. • J–O theory was used for analysis of luminescent properties of NaEuF 4 phosphor. NaEuF 4 nano-/submicro-crystals with various morphologies including regular nano-spheres, submicro-spheres, submicro-spindles and hexagonal submicro-rods were prepared through a facile hydrothermal process by adjusting the pH value and the molar ratio of Na 3 Cit/Eu 3+ in the precursor solution. The resultants were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and photoluminescence spectroscopy (PL). The possible formation mechanisms for the morphology-varied NaEuF 4 crystals were proposed based on the FE-SEM observation. The luminescent properties of NaEuF 4 spheres with different particle size were studied. It was found that the luminescent intensities of NaEuF 4 spheres increase with the decrease of particle size. Finally, the mechanism of luminescent enhancement was discussed.