Mixture Of Na2CO3 Research Articles

Structural Characterizations and Viscosity Behavior of Purified Clay Obtained by Hydrocyclone Process

Pure and low-cost bentonite was prepared by a simple procedure, different from that previously reported by sedimentation and centrifugation. In this case, the raw clay has been purified by the hydrocyclone procedure. The effect of sodium carbonate on the removal of the impurities and the proprieties of the clay phase has been investigated by XRD and FTIR analysis. The results showed a considerable reduction of quartz and calcite amounts. The best viscosity has been detected for the clay–Na2CO3 mixture 5 wt%. The use of the purified clay as an adsorbent of methylene blue showed the increases in the quantity removed from 118 mg/g for the raw clay to 184 mg/g for the purified clay with hydrocyclone.

Electronic conductivity in Gd-doped ceria with salt additions

Samples of Gd-doped ceria (GDC, Ce0.9Gd0.1O1.95) with eutectic mixtures of Na2CO3 and Li2CO3 (NLC), or K2CO3, Na2CO3 and Li2CO3 (KNLC) as sintering aids (5 mol%) were studied against pure GDC and cobalt doped GDC. The former electrolytes reached densifications in excess of 95% when sintered at 1100 °C, values comparable to pure GDC sintered at 1500 °C, and more than 20% higher than for GDC sintered at 1100 °C. X-ray diffraction powder patterns showed only typical GDC peaks without any noticeable lattice modification and microstructural analysis suggested a homogeneous distribution of residual amounts of sintering aids. The electrical properties of all materials were studied by impedance spectroscopy in air from 200 to 750 °C. Materials with NLC and KNLC showed a total ionic conductivity matching pure GDC at 600 °C. Hebb-Wagner polarization measurements, used to assess the impact of sintering aids on the n and p-type electronic conductivity of GDC (600–750 °C) showed that NLC and KNLC additions lower the p-type conductivity of GDC while Co additions have the opposite effect. The efficacy of alkali metal salts to produce ceria-based electrolytes with competitive ionic and electronic transport properties is exposed.

Preconcentration/Extraction of Phthalate Esters in Milk Samples Using MFe2O4-Based Magnetic Ionic Liquid Effervescent Tablets Consisting of Accessory Functional Fillers

Magnetic effervescent tablet-based (MEFTs) microextraction has recently gained much attention because it requires no physical energy inputs or dispersive solvent. A prominent shortcoming of MEFTs results from the short tablet storage period owing to rapid absorption of moisture, thereby making it impracticable for field use. Physico-chemical properties of MEFTs were greatly improved by the addition of water-soluble starch, such as hygroscopicity, storage/stability period, adherence, effervescent time, and intensity. MEFTs were used in a MFe2O4-based magnetic ionic liquid effervescent tablet microextraction (MMIL-ETM) for preconcentration/extraction of trace phthalate esters (PAEs) in milk matrices. This MMIL-ETM method provided three distinct advantages: (1) MEFTs integrate water-soluble starch as a functional filler, leading to longer tablet storage/stability; (2) combined effervescent dispersion and rapid retrieval of NiFe2O4 magnetic nanoparticles (MNPs) result in substantial time saving; and (3) integration of ionic liquid-based extraction with MNP adsorption produces high PAEs extraction recoveries. Optimized experimental parameters were as follows: 0.77 g mixture of Na2CO3 and water-soluble starch, 7 mg NiFe2O4 (30 nm), 50 μL [HMIM]NTf2, solution pH 2.3, and 300 μL acetonitrile as elution solvent. Under optimized conditions, extraction recoveries for four PAEs reached as high as 94.8–105.6%, LODs were as low as 0.042 μg L−1, and RSDs were < 5.4% for intra- and inter-day precisions. Due to the longer stable storage period and rapid dispersion without additional physical energy inputs, the proposed MMIL-ETM method shows great potential application for routine food monitoring under field conditions.

Anionic carbonate activation of layered (α+β) nickel hydroxide

Nickel hydroxide is widely used as the active material in supercapacitors. Samples of Ni(OH)2 with the (α+β) layered structure, synthesized in the slit-diaphragm electrolyzer, are the most active. The possibility of carbonate activation of layered (α+β) Ni(OH)2 was studied by the synthesis of samples in the slit-diaphragm electrolyzer using a mixture of sodium hydroxide and sodium carbonate as the electrolyte. The molar part of sodium carbonate in the NaOH+Na2CO3 mixture was controlled by acid titration in the presence of two indicators. The synthesis of nickel hydroxide samples was conducted at the molar part of carbonate from 0.16 (NaOH without the additional introduction of carbonate) to 0.83. The crystal structure of the samples was studied by means of X-ray diffraction analysis, electrochemical characteristic – by means of cyclic voltammetry and galvanostatic charge-discharge cycling in the accumulator regime. By means of XRD analysis, it was found that upon increasing the molar part of carbonate in the anolyte to 0.49, the crystallinity of the monophase layered (α+β) structure increases. It was found that a further increase of the carbonate part results in a more amorphous structure due to a partial breakdown of the hydroxide lattice with the formation of basic salts and formation of the bi-phase system. This conclusion is supported by cyclic voltammetry and discharge curves. The study of the electrochemical characteristics revealed, that for the molar part of carbonate below 0.39, carbonate activation of hydroxide occurs resulting in an improved specific capacity. Increasing the carbonate part to 0.49 results in a lower specific capacity, and even further increase results in the breakdown of hydroxide into basic salts and a significant drop in electrochemical activity. Thus, it was found, that to achieve the maximum activating effect, the optimal molar part of sodium carbonate (in a mixture with sodium hydroxide) should be about 40 %. The specific capacity of nickel hydroxide under this optimal condition is 234 mA·h/g, and this sample is found to be susceptible to activation with cobalt compounds, which further improved capacity to 254 mA·h/g.

Heating Mechanism of High Aluminum Fly Ash Activated by Na2CO3 in Microwave Field

The microwave-absorption capabilities of high-alumina fly ash (HAFA), Na2CO3 and HAFA–Na2CO2 mixtures were investigated by determining the dielectric properties [real part (e′), imaginary part (e″) and dielectric loss tangent (tan δ)] from 25°C to 800°C, using the microwave resonant cavity technique at a microwave frequency of 2450 MHz. The mass ratio of the HAFA–Na2CO3 mixtures used in all experiments was 1:1. The study found that the microwave absorption capabilities of HAFA alone do not change significantly within the range of temperatures examined. For both Na2CO3 and HAFA–Na2CO3 mixtures, however, a sharp increase in absorption capability was observed above 400°C. The microwave heating behavior of the HAFA–Na2CO3 mixtures can be divided into two stages: in the first stage (< 350°C), heating rates were found to be lower due to the weaker microwave absorption capability of the HAFA and Na2CO3; however, in the second stage (≥ 350°C), a sharp increase in heating rate was observed, linked to the strengthened absorption capability of the Na2CO3. The study found that HAFA–Na2CO3 mixtures have a good microwave-absorption ability and can be heated rapidly by microwaves; therefore, it is feasible to use microwave heating for the activation of high-alumina fly ash with Na2CO3.

Cathode Properties of Na3FePO4CO3 Prepared By Mechanical Milling Method for Na-Ion Battery

Introduction In rechargeable batteries for grid storage, the cost performance is more important than the energy density. For large-scale batteries, the minor metal-free cathode active materials are attractive for Na-ion batteries because of their natural abundance and low cost. In addition, polyanionic cathodes are also attractive for the high thermal and chemical stability. Among the iron-based phosphate family, the theoretical capacity of Olivine-type LiFePO4 is restricted to 170 mAh/g and the Na counterpart, Maricite-type NaFePO4 is electrochemically inactive. On the other hand, a new polyanionic intercalation cathode Na3FePO4CO3 has high theoretical capacity of 190 mAh/g based on Fe2+/Fe4+ redox 1). Nevertheless, Na2.24FePO4CO3 synthesized by hydrothermal method can just deliver discharge capacity of 112 mAh/g at 10 mA/g, corresponding to 1.18 e- reaction, because of the oxidation of Fe2+ during hydrothermal process and intrinsic property of a poor ionic conductivity2). In order to improve electrochemical performance of Na3FePO4CO3, mechanochemical synthesis method by ball milling was tried in a manner similar to NaMF3 3). In addition, we investigated the cathode properties of Na3FePO4CO3 against Na metal anode and confirmed the reversible multi electron reaction in it. Experimental NaFePO4 + Na2CO3 /C composite was prepared by three-step mechanical ball milling. First, the mixture of Na2CO3 and maricite-NaFePO4 obtained by solid state method 4) with the molar ratio of Na2CO3 : NaFePO4 = 1 : 1 was put in the Ar-filled container with 3f-ZrO2 balls. This mixture was ball-milled using a planetary mill (Pulverisette7, Fritsch Japan Co., Ltd.) with a rotation speed of 600 rpm for 12 h. Second, the obtained mixture was ball-milled with 15 wt% acetylene black (AB, Denka Co., Ltd.) at a rotation speed of 500 rpm in Ar. And then, the above mixture was ball-milled again with 15 wt% AB with a rotation speed of 400 rpm in Ar. The cathode pellets were fabricated by mixing of the NaFePO4 + Na2CO3 /C composite powder with a 10 wt% polytetrafluoroethylene (PTFE) Teflon binder (Polyflon PTFE F-104, Daikin Industries, Ltd.) and punched into disks (ca. 30 mg weight and 10 mm diameter). The electrochemical performance of the NaFePO4 + Na2CO3 /C composite was evaluated by a 2032 coin-type cell with a nonaqueous electrolyte (1 M NaPF6/EC:DMC(1:1 in vol.) Tomiyama Pure Chemical Industries, Ltd.) and a glass filter separator (GA-55, ADVANTEC) against Na metal (Sigma-Aldrich). All cells were assembled in an Ar-filled glove box. The charge-discharge measurements were performed in galvanostatic mode at 25°C. Results and discussion The initial and second charge-discharge profiles of the mechanical milling-synthesized NaFePO4 + Na2CO3 /C composite cathode was obtained between 1.5 and 4.5 V at a rate of 0.4 mA/cm2 at room temperature (Fig. 1). During the first cycle, the obtained sample deliver a discharge capacity of 125 mAh/g, and even after 30 cycles, a reversible discharge capacity of 113 mAh/g, corresponding to 1.19 e- reaction per mole. In order to investigate the valence state of Fe in initial sample, Mössbauer spectroscopy experiment performed on initial sample. The result suggests that the 34% Fe in the sample is oxidized from 2+ to 3+. In Fig. 1, two plateaus of 2.6 and 4.2 V in the 2nd charged profile were observed, which correspond to the redox voltage of Fe2+/Fe3+ and Fe3+/Fe4+ in the reported value3). We will report about the electrochemical performance of NaFePO4 + Na2CO3 /C composite at RT and elevated temperature. The charge-discharge mechanism of NaFePO4 + Na2CO3 /C composite cathode will be also discussed at the presentation. References 1) H. Chen, et al., J. Am. Chem. Soc., 134, 19619 (2012). 2) A. Kitajou, et al., Electrochim. Acta., 245, 424 (2017). 3) W. F. Huang, et al., Sci. Rep., 4, 4188 (2014). 4) M. Avdeev, et al., Inorg.Chem., 52, 8685 (2013) Figure 1

Corrosion Experiments on Ceramic Samples Within Molten Salts

The molten salts can provide many possibilities for their use, e.g., an electrolyte in fuel cells or as a heat transfer medium and an oxygen transporter for flameless oxidation in molten salt oxidation (MSO) technology. The environment of molten salts is very corrosive; therefore, it is crucial to find such ceramic materials, which could be used as reactor filling for MSO technology. The aim of this work was to research physical properties of ceramic samples after the exposure within the eutectic mixture of Na2CO3, K2CO3, Li2CO3 and temperature of 700 °C.

Improving the electrochemical performance of layered cathode oxide for sodium-ion batteries by optimizing the titanium content

P2-type transition metal oxides are promising cathode materials for sodium-ion batteries. However, due to irreversible phase transition, these batteries exhibit low capacity and poor cycling stability. In this study, highly dense, spherical P2-type oxides Na0.67[Ni0.167Co0.167Mn0.67]1-xTixO2 (0 ≤ x ≤ 0.4) are synthesized by calcining a mixture of Na2CO3, spherical ternary precursor powder Ni0.167Co0.167Mn0.67O2, and different amounts of nanoscale TiO2. High-temperature X-ray diffraction results obtained during calcination reveal 850 °C as the optimum calcination temperature. All materials exhibit high crystallinity without any impurity phases. The initial reversible capacities of the as-prepared samples decrease with increasing Ti substitution; however, these samples attain better cycling stability. When x = 0.2, the sample delivers an initial discharge capacity of 138 mAh g−1 at 20 mA g−1 between 2 and 4.5 V. Even at 100 mA g−1, the sample delivers 101 mAh g−1 reversible capacity in the first cycle with capacity retention of 89.4% after 300 cycles. Moreover, the material shows sloping potential profiles, with the average voltages reaching up to ∼3.8 V. The ex-situ X-ray diffraction (XRD) results of the samples after cycling demonstrate that Ti substitution improves the structural stability. In general, Ti substitution is an effective approach for improving the electrochemical performance of ternary P2-type oxide Na0.67Ni0.167Co0.167Mn0.67O2.

Recovery of uranium and copper from mineralized dolostone, Gabal Allouga, Southwestern Sinai, Egypt

To avert excessive sulfuric acid exhaustion in the classical leaching procedure and to avoid leaching of other undesirable impurities, proper alkaline leaching has been achieved for dolostone of Gabal Allouga, Southwestern Sinai, Egypt. The relevant factors for alkaline leaching of a technological sample assaying 1.2% Cu and 0.15% U were examined using a mixture of Na2CO3/ (NH4) HCO3 solution upon two samples namely; roasted sample at 540°C and raw materials un-roasted. The leaching kinetic results showed that the leaching procedure of uranium and copper from dolostone is controlled by shrinking core kinetic model 1–2/3(X)−(1−X)2/3 = kdt.

Phase transformation mechanism in activation of high-alumina fly ash with Na2CO3

In this study, the phase transformation mechanism of a high-alumina fly ash (HAFA)–Na2CO3 mixture was investigated by temperature- and time-programmed heating in a muffle furnace. The temperature range was 600 °C–1000 °C, and the time interval was 20–120 min. The mass loss behaviour of the HAFA–Na2CO3 mixture was investigated by a thermogravimetric analysis method using argon at a heating rate of 10 °C min−1. It was found that HAFA without any added flux showed no loss or gain of any element or material under the experimental conditions. The results also showed that HAFA hardly contained any volatile water, carbon, sulphur, or other components. The decomposition of Na2CO3 occurred at 844 °C, and the HAFA–Na2CO3 mixture began to react at 600 °C, indicating that the reaction of HAFA with Na2CO3 started before the decomposition of Na2CO3. The phase transformation of the HAFA–Na2CO3 mixture at different temperatures for 60 min or at 900 °C for different times was investigated by x-ray diffraction. Each reaction required different temperature conditions, and at a specific temperature, the length of the heating time affected the progress of the reaction.

Laser Fluorimetric determination of the extracted uranium from industrial grade phosphoric acid and phosphate rocks using natural adsorbent, EWS

ABSTRACTLaser fluorimetric determination of the complete reduced U(IV) using Zn metal was applied on industrial grade phosphoric acid and phosphate rocks after separation using a low cost natural cationic adsorbent of Egyptian white silica sand (EWS). The determination process was performed after prior separation of cationic uranyl complex. This method was applied to overcome the interfering problems of P(V), Fe(III) and Ca(II). For maximum loading efficiency, the adsorption parameters such as pH, amount of adsorbent, contact time, temperature and initial U(IV) concentrations were investigated via a batch process. On the other hand the effective elution factors such as eluting agents, ratio of Na2CO3 with NaHCO3, volume of 30% H2O2, contact time and temperature were also investigated. A selective elution of oxidized U(VI) was carried out by using a 1 mol L−1 mixture of Na2CO3 and NaHCO3 solution in the presence of (0.8 mL/10 mL) of 30% H2O2 as an oxidizing agent. The maximum U loading capacity (75 mg g−1) was attained at the resulted optimum loading and elution conditions.

Role of temperature in de-mixing absorbance spectra composed of compound electrolyte solutions.

This work is focused on the role of temperature in the de-mixing of absorbance spectra measured in mixed aqueous Na2SO4 and NaNO3 solutions. First, the influence of temperature on the absorbance spectrum of demineralized water was determined. Second, the absorbance spectra of five separate electrolytes (NaNO2, NaNO3, CaCl2, K2CO3, and NaOH) at three temperatures (4°C, 25°C, and 50°C) for concentrations ranging from 0.0625M to 0.5M were examined. These five electrolytes show similar temperature dependencies. Finally, absorbance spectra of mixed solutions were investigated at temperatures of 5°C, 15°C, 25°C, 35°C, and 45°C for concentrations ranging from 0.0625M to 0.5M per electrolyte in the mixture. The spectral window from 650 to 1100nm was utilized to observe the ionic and temperature influences on the vibrational modes of the OH bond in the solvent molecules. The effects of dissolving Na2SO4 and NaNO3 are nonlinearly cumulative at lower temperatures indicating extended alteration of the water structure beyond the first hydration shell. A similar trend was observed for a mixture of Na2CO3 and NaCl. Furthermore, it was found that higher temperatures are better for recovering the separate component absorption signatures of an electrolyte mixture. The near-infrared spectral regime is well suited for integrated sensing, and therefore these results can help in designing an integrated sensor to identify inorganic species in water.

Utilization of coal fly ash from a Chinese power plant for manufacturing highly insulating foam glass: Implications of physical, mechanical properties and environmental features

This research focuses on the potential use of fly ash (WAf) from a Chinese pulverized-coal combustion (PCC) power plant for manufacturing foam glass. The influences of fly ash properties, fly ash/recycled glass proportion in the raw materials, addition of fluxing and foaming agent, firing temperature, and residence time at the peak temperature on the final properties (apparent density, compressing strength and leachable potential of major and trace elements) of the foam specimens are investigated. The optimal foaming products were obtained consuming up to 33.3–43.3% fly ash, adding 9–11% Na2CO3 fluxing agent and 0.5% SiC foaming agent, firing at 865–915 °C during 15 min residence time at the peak temperature. The obtained fly ash-based product revealed comparable compressive strength but slightly higher densities than commercial foam glass, with low CO2 emissions and low leachable potential for environmentally relevant trace elements within the limits for inert/no-hazardous material established by the European Council Decision 2003/33/EC for land waste disposal. The large porosity of the foam glass indicates a high potential of thermal and acoustic insulation. The foaming behavior and the final properties the foam glass are strongly influenced by properties of fly ash (mainly fluxing temperature and organic C content), fly ash/recycled glass proportion in the raw materials, addition of Na2CO3 fluxing agent and SiC foaming agent, firing temperature, and residence time at the peak temperature. The low C content and high refractory character of WAf give rise to poor foaming of the specimens when only fly ash and Na2CO3 mixtures are used. The consumption of relatively high proportions of recycled glass and SiC is essential to produce foaming.

Analysis of Niobium–Rare-Earth Ores by Inductively Coupled Plasma Mass Spectrometry

To determine the composition of niobium–rare-earth ores by atomic emission spectrometry and inductively coupled plasma mass spectrometry, two procedures are developed for sample preparation based on autoclave decomposition and flux fusion. Autoclave decomposition is carried out in a mixture of HF and HNO3 at a temperature of up to 220°C and a pressure of up to 160 atm using a developed system with resistive heating. Subsequent evaporation to dry salts ensures the removal of F– ions and silicon as SiF4. The residue is dissolved in a mixture of HCl and H2O2 at 160°C under elevated pressure. The resulting solutions (10% with respect to HCl with the addition of H2O2) are diluted before measurements. The dissolution process is monitored for each sample using stable highly enriched isotopes of 91Zr, 100Mo, 149Sm, and 178Hf. The second procedure is based on fusing samples with a mixture of Na2CO3 and Na2B4O7 at 1050°C in a muffle furnace and dissolving the resulting melt in a mixture of HCl and H2O2. The procedures were tested using the national (NFS-23) and foreign standard samples of composition (OREAS-462, 463, 464, 465, Australia) and real samples of niobium–rare-earth ores.

Advanced low-temperature ceramic nanocomposite fuel cells using ultra high ionic conductivity electrolytes synthesized through freeze-dried method and solid-route

Low ionic conductivity and slow reaction kinetics often limit the performance of a ceramic nanocomposite fuel cell (CNFC). Here, we report a novel synthesis method, freeze-dried method, to achieve a record high ionic conductivity for nanocomposite electrolytes (>0.5 S/cm) based on Ce0.85Sm0.15O2 (SDC) and a eutectic mixture of Na2CO3, Li2CO3, K2CO3 (NLK). The highest ionic conductivity (0.55 S/cm) was reached by increasing the carbonate content of the electrolyte to 35 wt%. For the sake of comparison, the nanocomposite electrolytes were also prepared through solid-route. Composite anodes and cathodes for complete fuels were prepared from NiO and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), respectively using both solid-route and freeze-dried nanocomposite electrolytes. Complete fuel cells manufactured from these nanocomposite materials produced ∼1.1 W/cm2 at 550 °C. The EIS measurements revealed low ohmic losses (0.18 Ω cm2) and even lower charge transfer resistance (0.05 Ω cm2). In addition, it was found that the open-circuit-voltage (OCV) of the CNFCs improved from 1.1 V to 1.2 V when a mixture of air and CO2 was supplied as compared to the case when only air was supplied at the cathode. Finally, high temperature X-ray diffraction (HT-XRD) revealed stable structures of SDC, NiO and LSCF up to 600 °C, which shows the thermal stability of these fuel cell materials.

Comparative analysis of ceramic-carbonate nanocomposite fuel cells using composite GDC/NLC electrolyte with different perovskite structured cathode materials

A comparative analysis of perovskite structured cathode materials, La0.65Sr0.35MnO3 (LSM), La0.8Sr0.2CoO3 (LSC), La0.6Sr0.4FeO3 (LSF) and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), was performed for a ceramic-carbonate nanocomposite fuel cell using composite electrolyte consisting of Gd0.1Ce0.9O1.95 (GDC) and a eutectic mixture of Na2CO3 and Li2CO3. The compatibility of these nanocomposite electrode powder materials was investigated under air, CO2 and air/CO2 atmospheres at 550 °C. Microscopy measurements together with energy dispersive X-ray spectroscopy (EDS) elementary analysis revealed few spots with higher counts of manganese relative to lanthanum and strontium under pure CO2 atmosphere. Furthermore, electrochemical impedance (EIS) analysis showed that LSC had the lowest resistance to oxygen reduction reaction (ORR) (14.12 Ω∙cm2) followed by LSF (15.23 Ω∙cm2), LSCF (19.38 Ω∙cm2) and LSM (>300 Ω∙cm2). In addition, low frequency EIS measurements (down to 50 μHz) revealed two additional semi-circles at frequencies around 1 Hz. These semicircles can yield additional information about electrochemical reactions in the device. Finally, a fuel cell was fabricated using GDC/NLC nanocomposite electrolyte and its composite with NiO and LSCF as anode and cathode, respectively. The cell produced an excellent power density of 1.06 W/cm2 at 550 °C under fuel cell conditions.

A hydrometallurgical process for the recovery of metal values from spent Cu–Cr catalyst

ABSTRACTThe Cu–Cr catalyst has been used in many chemical processes and dumped in the landfill after losing the catalytic property. Owing to the toxicity of chromium, the dumping of catalyst is not environmentally acceptable. So metal values should be removed before disposal. One typical Cu–Cr catalyst was leached with H2SO4 and from the leach liquor Cu and Cr were extracted using LIX 860N and NaD2EHPA, respectively. The McCabe–Thiele diagram at pH 3.5 with 20% LIX 860N indicated two stages at A:O = 1:1 for quantitative extraction of copper. The stripping of Cu was achieved by 10% H2SO4. After the extraction of Cu, the extraction of Cr was carried out with NaD2EHPA. The McCabe–Thiele diagram for Cr extraction with 0.5 M NaD2EHPA at pH 3.0 showed two stages at A:O ratio of 1:1. The loaded organic of chromium was stripped with the mixture of Na2CO3, NaOH and H2O2.

The impact of seawater with calcium and magnesium removal for the flotation of copper-molybdenum sulphide ores

The use of seawater in the flotation of copper-molybdenum sulphide ores is becoming increasingly important. However, the complex chemistry by the presence of calcium and magnesium hydroxyl-complexes interferes with the recovery of molybdenite. This study analyzes the impact of pre-treated seawater with calcium and magnesium removal on the floatability of copper-molybdenum sulphide ores. The pretreatment was carried out by a mixture of Na2CO3 and CaO, which promotes the precipitation of calcium and magnesium ions. Three different conditions were compared, (i) flotation in seawater at pH 11.5; (ii) flotation in pretreated seawater with calcium and magnesium removal at pH 11.5; and (iii) flotation in seawater at natural pH, i.e. pH≈7.6. While the copper recovery was similar in all cases, the recovery of molybdenum at high alkaline condition was notably increased when seawater harness was reduced. On the other hand, a high pyrite depression was reached because the oxidizing atmosphere at pH 11.5 allows Fe(OH)3 formation.

ChemInform Abstract: Synthesis, Crystal Structure and Charge‐Distribution Validation of β‐Na4Cu(MoO4)3 Adopting the Alluadite Structure‐Type.

AbstractSingle crystals of the new β‐variety of Na4Cu(MoO4)3 are prepared by firing a 4:1:3 molar mixture of Na2CO3, Cu(OAc), and (NH4)6Mo7O24 in air (porcelain crucible, 873 K, 20 d; cooling to 823 K at a rate of 10 K/d).

Local Structure Analysis of Na0.5Bi0.5TiO3 based Oxide Ion Conductor By DFT Calculations and RMC Method

INTRODUCTION In recent decades, oxide-ion conducting ceramics are expected to be applied for various electrochemical devices, such as the solid oxide fuel cells (SOFC), and play an important role in the field of the solid-state electrochemistry. Among the devices, SOFC has attracted much attention because it realizes high power generation efficiency and low environmental load. The operating temperature of commercially available SOFC is too high, i.e. 1000 ˚C, at present and thus lowering the operating temperature to around 500 ˚C (intermediate temperature) is highly desired to put them into practical use. Recently, it has been found that Na0.5Bi0.5TiO3 based materials exhibit high oxide-ion conductivity and low activation energy, and the materials become potential candidates for electrolytes of SOFC at the intermediate temperature. In this work, in order to investigate effects of Bi and O deficits on atomic configurations of Na0.5Bi0.5TiO3-based materials and local environment of these deficits, we prepared Na0.5Bi0.5-xTiO3-δ and Na0.5+yBi0.5-yTiO3-δ. The atomic configurations of the samples were investigated by analyzing neutron and synchrotron X-ray total scatterings with the density functional theory (DFT) and the reverse Monte Carlo (RMC) simulation. EXPERIMENTAL Na0.5Bi0.5-xTiO3-δ and Na0.5+yBi0.5-yTiO3-δ were synthesized by solid-state method. In the solid–state method, mixture of Na2CO3, TiO2 and Bi2O3 was calcined at 850 oC for 3 h in air, and then sintered at 1100 oC for 2 h in air. The samples were identified by X-ray diffraction. The metal compositions were evaluated by inductively coupled plasma spectroscopy (ICP) and atomic absorption spectrometry(AA). Cross-section morphologies of the bulk samples were observed by scanning electron microscopy (SEM). The densities of the sintered pellets were evaluated by the Archimedes method. The conductivity measurements were carried out between 300-900 oC by the AC impedance method. Neutron powder diffraction experiments were performed at BL20B2 (J-PARC, Japan). The data were refined using Rietveld technique (Z-code). In order to discuss the effect of Bi and O deficits on the atomic configurations, Na0.5Bi0.5-xTiO3-δ and Na0.5+yBi0.5-yTiO3-δ were also investigated by the RMC simulation (RMCProfile) using total scattering data measured by synchrotron X-ray (BL04B2, SPring-8) and neutron (BL21, J-PARC) sources in addition to the Bragg profile. RESULTS AND DISCUSSION It was found from XRD measurements that Na0.5Bi0.5-xTiO3-δ and Na0.5+yBi0.5-yTiO3-δ could be attributed to the perovskite-type structure with a space grope of Cc. The analytical compositions of Na0.5Bi0.5-xTiO3-δ and Na0.5+yBi0.5-yTiO3-δ evaluated by ICP and AA analysis were able to be controlled, and thus essentially equal to the nominal values. From the results of the Archimedes method, relative densities of the samples were more than 94 %. Figure 1 shows conductivities of the samples as a function of temperature. As seen in this figure, the conductivities of Na0.5Bi0.5-xTiO3-δ were increased with decreasing the Bi amount. In addition, by comparing the conductivity of Na0.5Bi0.5-xTiO3-δ and Na0.5+yBi0.5-yTiO3-δ, it was demonstrated that better electrochemical property could be achieved in the case of Na0.5+yBi0.5-yTiO3-δ. Conductivities measured under conditions of oxygen and argon showed similar behavior against temperature, indicating dominant oxygen-ion conduction. In the Rietveld analysis, we assumed the space group as Cc, and then could refine the average structure successfully. In addition, in order to examine local structures and cation arrangements around the Bi vacancies around and O vacancies in detail, the synchrotron radiation X-ray and neutron total scatterings were measured for Na0.5Bi0.5-xTiO3-δ and Na0.5+yBi0.5-yTiO3-δ. By using the data, the local structure analysis by the RMC method and the DFT was carried out. As a result, considerable differences in the bond distance between the each oxygen and bismuth was observed, and the effect on the conductive properties were suggested. REFERENCES 1)M.Li, M.J.Pietrowski et al., Nature Materials, 13, 31 (2014). Figure 1