Palladium(II) complexes adsorption from the chloride solutions with macrocomponent addition using strongly basic anion exchange resins, type 1

The use of the strongly basic anion exchange resins, type 1 such as Lewatit MP-500 and Lewatit MP-500A for palladium(II) complexes adsorption has been investigated. The adsorption process was carried out from the chloride solutions with macrocomponent (sodium chloride) addition (x M HCl–1.0 M NaCl; x M HCl–2.0 M NaCl) where the concentration of hydrochloric acid was constant and equal to x = 0; 0.1; 0.5; 1.0; and 2.0 M, respectively. The breakthrough curves of Pd(II) were determined and the sorption parameters (weight and bed distribution coefficients, working anion exchange capacity) were calculated. The pseudo-second kinetic order was applied in kinetic studies as well as to calculate the kinetic parameters. The values of the working anion exchange capacities (0.029 g/cm³; 0.028 g/cm³) for Lewatit MP-500 and Lewatit MP-500A (0.028 g/cm³; 0.027 g/cm³) in the 1.0 M NaCl and 0.1 M HCl–1.0 M NaCl solutions, respectively are really close and in other solutions under discussion Lewatit MP-500 possess slightly higher values of capacities, and therefore is insignificantly more efficient in the adsorption process of palladium(II) ions than Lewatit MP-500A. The equilibrium adsorption capacities changed in the range 8.84–9.99 and 8.40–9.38 mg/g for Lewatit MP-500 as well as 8.12–9.57 and 7.26–8.85 mg/g for Lewatit MP-500A in the chloride x M HCl-1.0 M NaCl and x M HCl-2.0 M NaCl solutions, respectively. The adsorption process proceeds according to the pseudo-second kinetic order.     

Charge transfer at Fe/FeO(CaF2) electrodes at 1450 ‡C: Exchange current density,electrode capacitance,diffusivity

The kinetics of the electrode reaction Fe = Fe _slag ²⁺ + 2e ^- has been investigated using the single and double pulse techniques. It was found that the exchange current densities are very large increasing from 2 to 10 A cm^-2 in the range of Fe²⁺-concentration from 2 · 10^-6 to 30 · 10^-6 mole cm⁻³. The electrode capacitance increases from 50 ΜF cm^-2 approximately linearly with the square root of Fe²⁺-concentration. An attempt was made to explain the concentration dependent part of the capacitance in terms of a model involving electrosorption of the speciesFe _ad ⁿ⁺ at the slag/iron interface. If the adsorbed iron ions are the intermediates in a consecutive charge transfer mechanism, the rate determining step is the transfer of iron between the adsorbed layer and the slag. On the other hand, it may be possible that the transfer is in one step with adsorption occurring in parallel. Formerly with Max-Planck Institut für Eisenforschung, D-4000 Düsseldorf, Germany     

The kinetics of the exchange of cobalt(II) ions between NaCl and Na2O-SiO2-Fe2O3 melts in the temperature range 1200 to 1400 K

Studies of the equilibria and kinetics of the Co²⁺ ion exchange in the Na₂O-SiO₂-Fe₂O₃/NaCl system were performed over the 1200 to 1400 K temperature range by measuring the emf of galvanic cells of the following composition: $$( - )Co\left| {\frac{{NaCl - CoCl_2 }}{{Na_2 O - SiO_2 - Fe_2 O3}}} \right.\left| {NaCl - CoCl_2 } \right.\left| {Co( + )} \right.$$ Distribution coefficients α of the Co²⁺ ions between the salt phase and silicate melt are of the l0^?2 order. Differential equations describing the transfer process of the Co²⁺ ions from the salt phase to the silicate phase were solved. The diffusion coefficients D_Co ²⁺ in the Na₂O-SiO₂-Fe₂O₃ melt were determined by substituting the Co²⁺ ion concentration change in fused NaCI into the differential equations. The values of D_Co ²⁺ are about 10^?5 cm²S^?1 and they decrease with decreasing temperature and increasing Fe_?2O_?3 content in slags. The diffusion coefficient of the cobalt (II) ions in slags determined in this way is consistent with that determined by the otating disk method.     

Solvent extraction of base metals by mixtures of organophosphoric acids and non-chelating oximes

The effect of non-chelating oximes on the extraction of several transition and nontransition metals by solutions of organophosphoric acids (H₂A₂) in xylene has been investigated. Synergistic enhancements of extraction of divalent transition metal ions were found with the oximes of aliphatic aldehydes, the enhancements of extraction increasing in the order VO²⁺ < Mn²⁺ < Mn²⁺ < Co²⁺ < Cu²⁺ < V²⁺ < Ni²⁺. Large synergistic effects were also found for copper(I) and silver(I). Among the divalent non-transition metals studied (Mg, Ca, Zn, Cd, Sn, and Pb), only cadmium showed a synergistic effect. No significant synergism was found for any of the trivalent metal ions studied (Fe, Cr, V, Al, Bi, La, Ce, and Nd). The extracted complexes of copper, cobalt, and nickel were shown to be octahedral in structure, with the compositions Cu(HA₂)₂(oxime)₂, Co(HA₂)₂(oxime)₂, and NiA(HA₂)(oxime)₃, respectively, in which HA₂^? acts as a bidentate ligand. Extraction rates were found to be rapid, even for nickel, and complete stripping of metal-loaded organic phases was effected by contact with 0.5 M mineral acid. Some practical applications, such as the recovery of nickel from acidic leach liquors, are envisaged.     

An Electrochemical Investigation of Fe(II) Dissolved in a Cryolite Melt

Chronopotentiometric studies were made on a cryolite melt containing 3.0 wt pct Al₂O₃ and 0.466 wt pct Fe(II) at 1293 K (1020 °C). The diffusion coefficient calculated from the time of the principal chronopotentiometric transition decreased as the current density was increased, and at the same time, a second subsequent transition appeared. The diffusion coefficient calculated from this second transition was constant at 5.44 × 10^?5 cm² s^?1. The results were interpreted to show that Fe(II) in the solution exists in two forms. Fe is deposited reversibly from an active form; its exchange current density must be >1 A cm^?2. Deposition from the other form is irreversible, and it occurs directly only at high overpotentials, leading to the second transition. The equilibrium constant [active]/[inactive] = 5.4. When the equilibrium is displaced by electrolysis of the active form, the inactive form decomposes to replenish it with a rate constant of 0.9 s^?1. The Tafel curve for the direct deposition of the inactive form shows a slope of 113 mV/decade, which is interpreted as n = 2 and a symmetry factor ≈1. The exchange current density is approximately 0.3 μA cm^?2. The active and inactive forms are identified tentatively as FeF ₃ ^? and FeF ₅ ^3? , respectively.     

Energy transfer process of Nd3+/Ho3+ co-doped fluoride halide glasses with anion substituted multi-wavelength tunable mid-infrared luminescence

Ho³⁺ doped ZBLAN glass with 2.0 and 2.9 μm emission was prepared. In order to further improve the luminescence of Ho³⁺, halogen ions (Cl, Br, I) were introduced to reduce the maximum phonon energy and phonon state density of the sample. At the same time, Nd³⁺ was introduced to transfer the energy to Ho³⁺ pumped with a 793 nm laser (Nd³⁺:⁴F_5/2,⁴F_3/2→Ho³⁺:⁵I₆). The effect of different halogen ion on the luminescent properties of the fluoride halide glass was compared. The results show that the luminescent intensity of infrared increases with the introduction of different halogen ions. By comparison, it is found that the sample with I^– has the strongest luminescence of 1064 nm, 2.0 μm and 2.9 μm. This is consistent with the calculated J-O intensity parameters. In addition, the 2.0 and 2.9 μm emission of Ho³⁺ pumped with a 450 nm laser will not disappear. A mid-infrared sample with multi-wavelength excitation and multi-wavelength emission can be obtained. Nd³⁺/Ho³⁺ co-doped fluoride halide glasses with 1064 nm, 2.0 μm and 2.9 μm luminescence were prepared by melt quenching method. The luminescent mechanism and the energy transfer process between the two ions of Nd³⁺/Ho³⁺ co-doped fluoride halide glass were studied. The J-O parameters, luminescence lifetime and absorption emission cross-sectional area of Ho³⁺ and Nd³⁺ were calculated, respectively. It is found that the value of Ω₂ in the glass matrix increases with the introduction of different halogen ions, while Ω₄ and Ω₆ do not change obviously in different glass compositions. This is because the environment of the crystal field around the rare earth ions changes. The crystal phase and phonon energy of the sample were analyzed by X-ray diffraction pattern and a Fourier transform infrared spectrometer, respectively. Based on the above spectra and data (phonon energy is 634.71 cm⁻¹), it can be predicted that Nd³⁺/Ho³⁺ co-doped fluoride halide glass is a potential mid-infrared luminescent material.     

Low temperature dielectric study on swift heavy ion irradiated 6H-SiC crystals

The effect of 150 MeV Ag¹²⁺ ion irradiation on the electrical behavior of 6H-SiC crystals has been studied by impedance spectroscopy. The study was carried out on the pristine, 8 ′ 10¹² ions/cm² and irradiated at 300 K and 80 K respectively. The present study elucidates the divergence of defect introduction due to irradiation at different temperatures through the electric polarizability and conductivity. The frequency and temperature dependent dielectric dispersions observed for the sample irradiated with 8 × 10¹² ions/cm² at 300 K are observed to be more than those of the sample irradiated at 80 K. The study reflects that more defects are produced in the case of 8 × 10¹² ions/cm² at 300 K irradiated sample than the sample irradiated with 8 × 10¹² ions/cm² at 80 K. The ac conductivity measured at 1 kHz over a temperature range from 100 – 300 K showed that complex defects are produced at 300 K for the swift heavy ion irradiated samples.     

Hydrogen reduction of spent copper electrolyte

The recovery of copper powder and the removal of arsenic from spent copper electrolyte by means of hydrogen reduction aimed at purifying the spent copper electrolyte were studied. About 90% of the copper in the electrolyte could be recovered in the form of pure copper powder after 20 min reduction at 180° at a hydrogen pressure of 20 kg cm^?2 (2.0 MPa). An induction period, due to slow hydrogen reduction of As⁵⁺ to As³⁺, could be eliminated as a result of the addition of copper powder as a reductant. Arsenic, antimony and bismuth in the liquor have been found to catalyze the hydrogen reduction of copper. When the copper concentration in the treated solution reached a certain low level, copper arsenide, Cu₃As₁ was formed on the surface of copper through hydrogen reduction of As³⁺ ions. This reaction was very slow and a long reaction time was required for complete removal of arsenic. Therefore, in order to purify spent copper electrolyte, some arsenic removal technique (e.g., solvent extraction) should be combined with hydrogen reduction.     

The oxidation of thiosulfates with copper sulfate. Application to an industrial fixing bath

This paper presents the transformation of thiosulfate using Cu(II) salts, such as copper sulfate, at pH between 4 and 5. The nature and kinetics of this process were determined. In the experimental conditions employed, the reaction between thiosulfates and Cu(II) ions produces a precipitate of CuS and the remaining sulfur is oxidized to sulfate, according to the following stoichiometry: 1 mol thiosulfate reacts with 1 mol Cu²⁺ and 3 mol H₂O, generating 1 mol copper(II), 1 mol sulfate and 2 mol H₃O⁺. In the kinetic study, the apparent reaction order was ≈ 0 with respect to H₃O⁺ concentration, in the interval 1.0 · 10^? 4–1.0 · 10^? 5M H₃O⁺; of order 0.4 with respect to Cu²⁺ in the interval 0.21–0.85 g L^? 1 Cu²⁺; and of order 0 with respect to S₂O₃^2? in the interval 0.88–2 g L^?1 S₂O₃^2?. The apparent activation energy was 98 kJ mol^? 1 in the interval 15–40 °C. On the basis of this behavior an empirical mathematical model was established, that fits well with the experimental results. The thiosulfate transformation process using copper(II) sulfate was applied to an industrial fixing bath that proceeded from the photographic industry; after this, the resulting effluent contained less than 10 mg L^? 1 of thiosulfates.     

Fabrication of Low—Permeability Gas-Flow Control Devices

Abstract

A commercially practicable P/M process for producing gas-flow control devices is outlined. Considerations favouring a P/M approach are presented and the importance of powder characteristics is stressed. The technology for producing units with a gas flow of the order of 10^?4cm³/s is outlined and the influences of sintering, compaction, and coining are discussed in detail. The generalizations resulting from this study are applicable to units ranging in flow rates from 10^?2 to 10^?8 cm³/s. Density reproducibility through compaction-pressure control is shown to be the most important factor in producing repeatable flow rates. Coining-tool geometry, compaction pressure, sintering kinetics, permeability, density, and pore size are variables considered in the analysis.     

Synthesis of N,O-rich active site porous polymers and their efficient recovery of Gd(Ⅲ) from solution

Our previous study found that the adsorption performance of porous carbon for Gd(Ⅲ) could be significantly improved by increasing the N,and O functional groups on its surface.Unfortunately,the adsorption capacity of porous carbon is low due to the limited number of N,and O functional groups that can be loaded on its surface.Due to the advantage of customizable functional groups of porous organic polymers(POPs),the triazine-based Tb-MEL and hydroxyl-modified triazine-based Tp-MEL were synthesized...     

Effects of Calcium and Chloride Ions in Iron Ore Reverse Cationic Flotation: Fundamental Studies

ABSTRACT

In this work, the simultaneous effects of Ca²⁺ and Cl^? ions in an aqueous solution at pH 10.5 on the flotation of quartz (the main impurity in itabiritic iron ore) and hematite by starch and amine was investigated. A strong depression in the flotation of both quartz and hematite conditioned with CaCl₂ was observed. This effect was higher for hematite than for quartz. Based on zeta potential measurements and the speciation diagram of calcium in aqueous solutions, the physical adsorption of Ca²⁺ on the surfaces of both minerals was inferred. The infrared spectrum of quartz conditioned with CaCl₂ at pH 10.5 was similar to its reagent-free reference spectrum. However, a new band at the wavenumber of 1465 cm^?1 was identified in the spectrum of hematite conditioned with CaCl₂; this band did not exist in its reference spectrum. This new band may indicate the chemical adsorption of Cl^? ions on the hematite surface. The complexation of Ca²⁺ by ethylenediaminetetraacetic acid enabled complete quartz recovery with amine. For hematite, recovery was partially restored, probably because of the positive chloro-complexes on the hydrated iron surfaces of hematite, which prevented the adsorption of aminium ions at these sites. Therefore, the selective inverse cationic flotation of itabiritic iron ore at pH 10.5 in water containing Ca²⁺ is possibly only after complexing them with EDTA.     

Extraction of cadmium (II) from phosphoric acid media using the di(2-ethylhexyl)dithiophosphoric acid (D2EHDTPA): Feasibility of a continuous extraction-stripping process

The extraction of cadmium from phosphoric media has been studied. The D₂EHDTPA was used as extractant and dodecane as diluent. No third phase was observed in the investigated conditions.A continuous micro-pilot scale mixer-settler was successfully tested for both extraction and stripping. More than 99% extraction rate was obtained in steady-state conditions with a flow rate ratio Aqueous/Organic equal to 1.1. Continuous stripping was performed using HCl 4 M. More than 96% of the cadmium was stripped in one continuous mixer-settler stage for flow rate ratio equal to 0.7. Results were in good agreement with the predicted values based on the McCabe–Thiele method. Experimental mixer-settler stages behave as ideal ones (Murphree efficiency > 98%).An optimal flow sheet is proposed to purify the Wet Phosphoric Acid (WPA) and to recover a relatively concentrated cadmium solution (1 g L^? 1). Two ideal stages operating at phase ratio A/S equal to 5/1 are required for the extraction step leading to a very depleted raffinate (< 0.2 µg L^? 1). For the stripping step, six stages are required (S/A = 5/1). The recovered organic phase contains less than 2 µg L^? 1 and could be recycled in the extraction step.     

Rate analysis of sorption of Ce3+, Sm3+, and Yb3+ ions from aqueous solution using Dowex 50W-X8 as a sorbent in a continuous flow reactor

Kinetic analysis of removal of three rare earth elements metals, Ce³⁺, Sm³⁺, and Yb³⁺ ions from aqueous solutions in a continuous flow fixed bed reactor using Dowex 50W-X8 ion-exchange resin was conducted. The performance of the fixed bed sorption was evaluated using the concept of the sorption breakthrough process. Parameters characteristic of a fixed bed sorption such as breakthrough times, saturation times, critical reactor lengths, and lengths of mass transfer zone were inferred from the metal ion concentration breakthrough curves. The sorption capacity of Dowex 50W-X8 ion-exchange resin for Ce³⁺, Sm³⁺, and Yb³⁺ are 191, 252, and 294 mg/g, respectively. The sorption kinetics were evaluated using a zero-order, first-order and second-order reaction models. The kinetics of the sorption process follows a zero-order model which has not been reported before. The rate constants of sorption using the zero-order kinetic model are obtained. Two different analysis were conducted to identify whether the diffusion is intraparticle or film diffusion. Both analysis confirms that the film diffusion is the controlling mechanism in reactor bed.     

Reduction of iron oxides from liquid slags using a graphite rotating disc

Research work has been carried out on the reduction of FeO from liquid slags of the CaO‐FeO‐SiO₂ ternary system using a graphite rotating disc technique. The investigations were conducted on slags with a basicity of CaO/SiO₂ = 1.27 and FeO contents of 20 and 60%, at temperatures of 1350 and 1420°C. The calculated viscosity range for these slags is within 2.53 – 0.43 dPa·s. It has been found that the factor controlling the reduction process is diffusion of FeO towards the disc surface, both in the case of the reduction from the slag with 20% FeO and in the case of the reduction from the slag with 60% FeO fraction. The diffusion coefficient of FeO at the reduction temperature of 1350°C is of the order of magnitudes of 10^?7 cm²/s, while at 1420°C it reaches the order of 10^?6 cm²/s. The calculated thickness values for the limiting diffusion layers range from 8.54·10^?3 to 0.70·10^?3 cm. It has been found that with increasing reduction rate also Boudouard's reaction starts to be important to the overall reduction rate. The limiting reduction rate at which Boudouard's reaction starts to be important to the entire process is dependent on temperature, being approximately 10.0·10^?6 mol FeO/cm² s at 1350°C, and approximately 15.0·10^?6 mol FeO/cm² s at 1420°C.     

Measurement of tracer diffusivities of Ca45 and Fe59 in silica saturated FeO-CaO-SiO2 melts with the porous frit technique

The tracer diffusivities of Ca⁴⁵ and Fe⁵⁹ in silica saturated FeO-CaO-SiO₂ melts have been determined, at 1600 °C, using the porous frit technique. The frits were made by sintering silica powder into quartz tubing. Diffusion occurred in a semi-infinite medium from a plane source of doped material with the same chemical composition. The tortuosity of each frit was determined by calibration with a resistivity cell. The diffusivity values obtained are about 2.0 · 10^?6 cm² s^?1 for Ca⁴⁵ and 1.0 · 10^?5 cm² s^?1 for Fe⁵⁹. The higher diffusivity of iron is possibly due to the different bonding by oxygen which causes a transition state in the jumps of Fe²⁺ ions from one site to the next.     

Optical and magnetic properties of GaN epilayers implanted with ytterbium

We have studied the optical and magnetic properties of ytterbium implanted GaN epilayer grown on(0001)sapphire by metalorganic chemical vapor by deposition(MOCVD).Samples were implanted at room temperature with Yb ions at dose 4x1015 cm-2 and energy of 150 keV.The implanted samples were annealed at 1000 ℃ in N2 at atmospheric pressure to recover implantation damages.The photoluminescence (PL),PL excitation(PLE),and PL kinetics have been studied with continuous and pulse photo-excitations in 360-1100 nm spectral range at different temperatures.The characteristic Yb3+ion emission spectra were observed in the spectral range between 970-1050 nm.Theoretical fittings of the experimental PL temperature and PL kinetics data suggest that Yb3+ions are involved in at least two major luminescence centers.The PLE spectra indicate that excitation of the Yb3+ion occurs via electron-hole pair generation and complex processes.Magnetization versus magnetic field curves shows an enhancement of magnetic order for Yb-implanted samples in 5 K to 300 K temperature range.The Yb-implanted GaN sample showing weak ferromagnetic behavior was compared with the ferromagnetic in situ doped GaYbN material.     

Separation and preconcentration of trace indium(III) from environmental samples with nanometer-size titanium dioxide

This work assesses the potential of an adsorptive material, nanometer TiO₂, for the separation and preconcentration of trace indium ions from various aqueous media. The adsorption behavior of nanometer TiO₂ for indium ions was investigated. It was found that the adsorption percentage of the indium ions was more than 96% in pH 3.5–4.0, and the desorption percentage of In(III) ions was more than 99% in pH ≤ 1.5. Good relative standard deviate (1.5%) and lower analytical detection limit (0.45 µg?mL^? 1) were obtained. The adsorption equilibrium was well described by the Langmuir isotherm model with monolayer adsorption capacity of 4566 µg g^? 1 (25 °C). The accuracy of the method is confirmed by analyzing the certified reference material (GBW-07405, GBW07406). The results demonstrated good agreement with the certified values.     

Production of high purity cobalt oxalate from spent ammonia cracker catalyst

A process was developed to produce > 99.9% pure cobalt oxalate from spent ammonia cracker catalyst pellets containing ∼ 20% Co generated at heavy water plants. A pilot plant for producing kilograms of cobalt oxalate of required purity has been set up. The process consists of leaching, oxidation, solvent extraction, ion exchange and oxalate precipitation. The major impurities present in the leach liquor after nitric acid oxidation were Fe³⁺, Al³⁺ and Ni²⁺. Fe³⁺ and Al³⁺ were separated from the leach liquor by using a solvent extraction (SX) process employing a mixed extractant system consisting of D2EHPA and TBP. Ni²⁺ was separated by ion exchange (IX) employing Dowex M4195 resin.     

Optical properties of Nd3+ ions doped GdTaO4 for pressure and temperature sensing

Pressure- and temperature-dependent luminescence properties of ³F_3/2 → ⁴I_9/2 transition of Nd³⁺:GdTaO₄ were studied for potential applications in optical sensing. Two isolated emission lines corresponding to ³F_3/2 (R_{2, 1}) → ⁴I_9/2 (Z₅) transitions, located at 920 and 927 nm under ambient condition, are very sensitive to pressure with coefficients of ?15.6 and ?14.5 cm^?1/GPa determined in a pressure range up to about 9 GPa. The luminescence intensity ratio between the two emission lines exhibits a large dependence with temperature in a range from 80 to 620 K, the corresponding temperature sensitivity at room temperature is similar to that of Nd³⁺:YAG. These advantages, together with the other observed features of high stable position relationship under pressure and low thermal shifts for the two emission lines indicate that Nd³⁺:GdTaO₄ is a promising candidate to be used as pressure and temperature sensors in the near-infrared spectral range.