Extraction mechanism of cerium（Ⅳ） in H2SO4/H3PO4 system using bifunctional ionic liquid extractants

The extraction of Ce（Ⅳ） in H2SO4/H3PO4 system was investigated systematically using bifunctional ionic liquid extractants（Bif-ILES） [A336][P507],[A336][P204] and [A336][C272] in n-heptane.The effects of H2SO4 concentration,extractant concentration and salting-out agent concentration were observed in detail.The extraction mechanism of Ce（Ⅳ） in H2SO4/H3PO4 system was obtained.The comparison with other extractants such as Cyanex923,TBP was also studied.Thermodynamic functions of the extraction reaction were calculated,showing that the extraction was an exothermic process.The separation of Ce（Ⅳ） from RE（Ⅲ） and Th（Ⅳ） was also investigated.The result indicated that Ce（Ⅳ） could be selectively extracted in this system.CePO4 nanoparticles were obtained in the process of stripping using H2O2 in H2SO4/H3PO4 system.X-ray diffraction（XRD）,scanning electron microscopy（SEM） and spectroscopy were adopted for the characterization of the sample.     

Thermodynamic and application study of complicated extraction system Ce(IV)–HF–H3BO3–H2SO4 using Cyanex 923

This article aims to reduce the environmental pollution while maximizing the recovery of REEs as well as associate resource-fluorine (F) from bastnaesite. This paper investigates the extraction equilibrium process and mechanism of Ce(IV)–HF–H₃BO₃–H₂SO₄ system using Cyanex 923. Extraction equilibrium process of different systems, including HF–H₂SO₄, H₃BO₃–HF–H₂SO₄, and Ce(IV)–HF–H₂SO₄, were studied in detail and the corresponding extraction mechanisms were also determined. It is noteworthy that a synergistic effect between B–F and an antagonistic effect between Ce(IV)–F were discovered first in the extraction process by Cyanex 923. Besides, H₃BO₃ is found to be able to promote the extraction of F in quantitation by Cyanex 923. FTIR and ¹¹B and ¹⁹F NMR were adopted to characterize the different loaded organic phase. Based on these results, the extraction mechanism of complicated system Ce(IV)-HF-H₃BO₃–H₂SO₄ was further determined. Besides, the effect of H₃BO₃ on the extraction and stripping of Ce(IV) in complicated system was studied. Moreover, it shows that the addition of H₃BO₃ has nothing to do with the purity of obtained CeF₃ particle from bastneasite liquor in the practical system. Adding H₃BO₃ into bastnaesite leach liquor, on the one hand, will be beneficial for the recovery yield of Ce and F. On the other hand, it can avoid from environmental pollution caused by emission of F-containing waste water as well as reducing the waste residue.     

Experimental measurements and modelling of viscosity in CaO–Al2O3–MgO slag system

Abstract

The viscosity of the CaO–Al₂O₃–MgO slag system has been measured by the rotating cylinder method up to 1823 K. The MgO content was between 0·39 and 11·33 wt-%, and the mass ratio of CaO/Al₂O₃ was between 0·60 and 1·28. The results indicated that both the MgO content and the mass ratio of CaO/Al₂O₃ have an influence on the viscosity of the slag. The effect of the mass ratio of CaO/Al₂O₃ is larger than that of the MgO content. The viscosity decreased with increasing MgO content and then increased. The effect of the mass ratio of CaO/Al₂O₃ on the viscosity was similar. The main mineralogical compositions of the slag were determined by X-ray diffraction, and their effects on viscosity were investigated. The measured results were in good agreement with those given by the Iida model.     

High-temperature phase equilibria of Cu–O–Al2O3 system in air

Phase equilibria of Cu–O–Al₂O₃ system were experimentally investigated in a temperature range of 1100–1400°C under 0.21?atm oxygen pressure. The experiments were conducted employing a high-temperature equilibration and quenching method. Microstructures of the quenched samples were observed with scanning electron microscope. The phase compositions in the samples were analysed with electron probe microanalysis technique. Measured solubility of Al₂O₃ into the molten oxide ranged from 0.0 to 1.8?wt-%. A small solubility of Cu₂O into Al₂O₃ was also observed ranging from 1.20 to 1.58?wt-%.     

Extraction and Stripping of Ytterbium （Ⅲ） from H2SO4 Medium by Cyanex 923

Ytterbiumand other lanthanide oxides are widelyused in the preparation of optical glasses ,glass fibersfor optical purposes ,gasoline-cracking catalysts ,pol-ishing compounds and carbon arcs , and in the ironand steel industriestoremove sulfur ,carbon ,and oth-er electronegative elements fromiron and steel[1].Themain sources of ytterbiumand other heavy rare earthelements are monazite and bastnasite . Withincreasingdemand for rare earth elements ,the separation andpurification of these elements…     

Leaching of a sphalerite concentrate with H2SO4–HNO3 solutions in the presence of C2Cl4

The enhanced leaching of sphalerite concentrates in H₂SO₄–HNO₃ solutions and the extraction of sulfur with tetrachloroethylene were studied. Variables of the process were investigated including leaching temperature, reaction time, liquid / solid ratio, and tetrachloroethylene concentration. The number of cycles that tetrachloroethylene could be recycled did not have a significant effect on zinc extraction. The results indicated that 99.6% zinc extraction was obtained after three hours of leaching at 85 °C and 0.1 MPa O₂, when 20 g of sphalerite concentrate were leached in a 200 ml solution containing 2.0 mol/L H₂SO₄ and 0.2 mol/L HNO₃, in the presence of 10 ml C₂Cl₄. Leaching rates were significantly improved under these conditions.     

Phase diagram assessment of CaO–Al2O3–La2O3 system

Considering the significance of CaO–Al₂O₃–RE₂O₃ (RE?=?rare earth) phase diagrams, the Redlich–Kister expression was employed to evaluate the binary phase diagrams of CaO–Al₂O₃, La₂O₃–Al₂O₃ and CaO–La₂O₃ systems in the present work. Also, the activities of CaO and Al₂O₃ in the CaO–Al₂O₃ binary system were calculated. The phase diagram of the CaO–Al₂O₃–La₂O₃ ternary system was first assessed by Kohler extrapolation method. The accuracy of calculated phase diagrams was validated by comparing with existing experimental points and the calculation results from the literature. The obtained diagrams will lay a foundation for Al-killed steelmaking process, metallurgical flux and other fields’ industrial application.     

Extraction du nickel d'un concentré de pentlandite par HNO3/H2SO4

Abstract

The sulphuric and nitric acid leaching of natural and synthetic nickel sulphides has been investigated. Optimum leaching conditions of the factors influencing the extraction of metals (Ni, Cu, Co) from a pentlandite bearing-concentrate have been determined. These factors are: temperature, time concentration and sulphuric and nitric acids and pulp density. The activation energies of the process are 4.6 ± 0.1 Kcal/mole for the copper and cobalt and 4.7 ± 0.1 Kcal/mole for the nickel. These values indicate that the rate of metal extraction is controlled by the diffusion phenomena through the precipitate layer which is deposited on the mineral surface during the leaching. This layer is composed of elemental sulphur and basic ferric sulphate. A schematical flowsheet of the process is presented.

Résumé

La lixiviation par les acides sulfurique et nitrique des sulfures naturels et synthétiques de nickel a été etudiée en vue de l'optimisation des facteurs qui influencent la mise en solution des métaux (Ni, Cu, Co) à partir d'un concentre de pentlandite. Ces facteurs sont: la température, le temps, la concentration des acides sulfurique et nitrique et la densité de la pulpe. Les energies d'activation du procede sont 4.6 ± 0.1 Kcal/mole pour le cuivre et le cobalt et 4.7 ± 0.1 Kcal/mole pour Ie nickel. Ces valeurs indiquent que la vitesse d'extraction des métaux est contrôlée par les phenomenes de diffusion s'établissant à travers la couche de précipité qui se depose sur la surface minérale au cours de la lixiviation. Cette couche est composée de soufre élémentaire et de sulfate basique de fer ferrique. Le rhéogramme schématique du prócédé est présenté.     

Isothermal enriching and separation of perovskite phase from CaO–TiO2–SiO2–Al2O3–MgO melt by centrifugal force

Abstract

A new approach to isothermal enriching combined with separating perovskite phase from CaO–TiO₂–SiO₂–Al₂O₃–MgO melt by centrifugal force was investigated. Using a two-stage centrifugal separation process, the recovery ratio of Ti in the second concentrate was 99·34% and the tailings were 0·66%, thus demonstrating excellent Ti separation. These materials can be considered as suitable raw materials for titanium white and cement respectively.     

Influence of reaction of Al2O3 and carbonaceous materials in Al2O3–C refractories on aluminum and carbon pick-up of iron

Carbon-containing Al2O3 refractory crucibles and pure Al2O3 refractory crucible were fabricated to study the effect of carbon-containing Al2O3-C refractories on aluminum and carbon pick-up of iron.Refractory crucibles with pure iron powder were placed in a vacuum induction furnace and heated at 1600℃ for regular time under flowing argon atmosphere.The Al and C contents of iron samples were analyzed,and iron samples were also investigated using a field scanning electron microscope equipped with energy-dispersive spectroscope.The results showed that carbon materials did affect the interac?tion of(Al2O3-C)/Fe system,carbothermal reduction in alumina occurred in the reaction system and the extent of reactions depended on the kinds of carbon materials.     

Effects of Cerium Oxide on Ni／Al2O3 Catalysts for Decomposition of CH4 and C2H4

Characteristics of carbon deposition of CH4 and C2H4 decomposition over supported Ni and Ni-Ce catalysts were studied by using a pulse reaction as well as BET, TPR, XPS and hydrogen chemisorption techniques. It is found that there is a metal-semiconductor interaction (MScI) in the Ni-Ce catalyst, and the effect of MScI on the carbon deposition of CH4 decomposition is opposite to that of C2H4. A novel model of carbon deposition of CH4 or C2H4 decomposition was proposed.     

An empirical formula for accurate calculation of liquidus temperature of blast furnace slags in SiO2–Al2O3–CaO–MgO system

Precise numerical simulations of blast furnace (BF) rely on accurate and convenient thermophysical property models of BF slags. Liquidus temperature (T_liq) is one of the most fundamental properties of BF slag, however, the conventional phase equilibrium diagram method for T_liq calculation can be hardly used in numerical simulations. In this work, an accurate and simple empirical formulation suitable for T_liq calculation of BF slags in numerical simulations is established. The model was calibrated by 707 measurement representing 11 primary phase fields in SiO₂–Al₂O₃–CaO–MgO system. The calculated T_liq in present work agrees very well with the measured values, with an average error of only 17.1°C, which is much more accurate than CalPhad method. Present work also suggests that the liquidus region of BF slag at 1500°C should be slightly extended based on the classic phase equilibrium diagram.     

Corrosion mechanism of commercial doloma refractories in contact with CaO–Al2O3 –SiO2 – MgO slag

Abstract

The dissolution of three doloma based refractories in liquid CaO–Al₂O₃–SiO₂–MgO slag was studied. Cylindrical refractory specimens of doloma, carbon bonded doloma, and magnesia doloma were rotated in a stationary crucible of molten slag under forced convection conditions. Slag composition, temperature, rod rotation speed and rod immersion time were varied. The refractory dissolution rate was determined from the change in diameter of the cylindrical specimens. The corrosion rate was found to increase with temperature and rod rotation speed and decrease when the slag was nearly saturated with MgO. The findings of the study substantiate the assumption that the diffusion of magnesium oxide through the slag boundary layer controls the corrosion process. The results indicated the overall corrosion process to be the dissolution of refractory material into the slag, followed by slag penetration of the pores and grain boundaries and finally, dispersion of the grains into the slag.     

Unique structural and magnetic traits of Nd3+-substituted Co–Zn nanoferrites

Because of the technological potential of magnetic spinel nanoferrites, we prepared neodymium ion (Nd³⁺)-substituted cobalt-zinc ferrites (CZFs) with the form Co_0.5Zn_0.5Nd_xFe_2–xO₄ (0.0 ≤ x ≤ 0.05) via a hydrothermal method. The as-prepared samples were thoroughly characterized using various analytical techniques. XRD, FTIR and FESEM analyses confirm the formation of a cubic spinel phase of the CZFNPs (CZF nanoparticles). A decrease in the lattice parameter due to the substitution of Fe³⁺ by Nd³⁺ in the lattice structures is manifested in the XRD refinement data. The magnetic properties of the proposed CZFNPs were evaluated in terms of the saturation magnetization, remanence, coercivity, squareness ratio and magnetic moment. These CZFNPs exhibit superparamagnetic behaviors at room temperature. Moreover, the Nd³⁺ inclusion does not significantly affect the measured magnetizations and coercivities of the CZFNPs. Samples containing 0.01 and 0.03 Nd³⁺ exhibit lower saturation magnetizations than that of the pristine product. The squareness ratios much less than 0.53 are ascribed to surface spin disordering. The unique magnetic traits of the synthesized CZFNPs are primarily attributed to the substitution of Fe³⁺ ions, with smaller ionic radii, by Nd³⁺ ions, with larger ionic radii. The proposed CZFNPs may be useful for diverse magneto-optic applications.     

Optical properties and Judd–Ofelt analysis of Nd2O3 nanocrystals embedded in polymethyl methacrylate

PMMA matrices were doped with nano-crystalline neodymium oxides synthesized by thermal decomposition process. X-ray diffraction and high-resolution transmission electron microscopy measurements were carried out to investigate the structure, phase, and the morphology of the Nd_2O_3 nanocrystals and those embedded in the PMMA matrix. The average grain sizes were estimated 35 ± 6 nm and 46 ± 4 nm for non-annealed and annealed Nd_2O_3 particles, respectively. The grain size distributions(GSD) were calculated from the diffraction peaks of the annealed and non-annealed Nd_2O_3 powders and doped PMMA samples. The mass density, refractive index. UV-Visible absorption spectra were measured and the data were analyzed using the Judd-Ofelt approach to determine the oscillator strengths, the spontaneous emission probabilities and the branching ratios as a function of the nano-crystalline Nd_2O_3 content in the range of 0.1 wt.%-20 wt.% of MMA. Luminescence spectra upon 808 nm diode laser excitation were carried out in the wavelength range of 850-1550 nm at room temperature. The photoluminescence study has shown that the reasonably sharp emission peaks were observed upon heat treatment at 800 ℃ for 24 h for all concentrations of Nd_2O_3 nanopowders in PMMA. The infrared laser transition of Nd~(3+) ions at about 1.06 μm due to the ~4F_(3/2)→~4I_(11/2) transition was analyzed and discussed in Nd_2O_3 system for their possible applications in the photonic technology.     

Transient liquid phase sintering of high density Fe3Al using Fe and Fe2Al5–FeAl2 powders Part 2 – Densification mechanism analysis

Abstract

The use of Fe₂Al₅–FeAl₂ prealloyed powders and heating rates >150 K min^?1 overcomes the formation of density restricting Kirkendall porosity in the Fe–Al system. X-ray diffraction, electron probe micro analysis and differential thermal analysis suggest that the absence of a persistent liquid, experienced when liquid phase sintering with elemental powders, is overcome. Homogenisation is greater during heating at a rate of 20 K min^?1 than for 150, 250 or 400 K min^?1 and homogenous Fe₃Al forms across the compact at temperatures below the melting point of the liquid forming constituent, indicating that a liquid will not form under such processing conditions. The maximum density achieved under the processing conditions in the present study is 92% of theoretical density. The presence of large pores shortly after liquid formation suggests that the remaining porosity is largely due to powder agglomeration during mixing.