Extraction and separation of thorium and rare earths with 5,11,17,23-tetra （diethoxyphosphoryl）-25,26,27,28-tetraacetoxycalix[4] arene

A calixarene derivative, 5,11,17,23-tetra(diethoxyphosphoryl)-25,26,27,28-tetraacetoxycalix[4]arene (L), was studied for the extraction and separation of thorium and rare earths in nitrate medium. Thorium was extracted into the organic phase by a complex of Th(NO3 ) 4 ·L with the logarithm of the equilibrium constant of 2.77. Thermodynamic functions, ΔH, ΔG and ΔS were calculated to be-2.49,-15.55 kJ/mol and 44.53 J/(mol·K), respectively. The results indicated that this calixarene derivative might be used to separate thorium from rare earths and the separation factors were larger than 26. However, the salting-out agents affected the separation.     

铝在稀土萃取分离流程中的分布及分离方法研究(I)

本文对非稀土元素铝在P507-HCl体系稀土萃取分离流程Sm/Eu/Gd和～Gd/Tb/Dy中的分布和走向进行了研究,并对其各自的水相料液,进料级、水相出口、三出口和萃取有机相出口的两相稀土组成、浓度和铝含量进行了分析。结合进料级和三出口附近的元素组成计算了铝与钐的分离系数,通过物料平衡计算了铝的进出平衡情况。阐明了铝在其中的分布和走向规律,并提出了氢氧化钠和草酸沉淀等除铝方法。     

Enhanced separation of praseodymium and neodymium by kinetic“push and pull”system of[A336][NO_3]-DTPA in a column extractor

A new approach was suggested in present work for improving the separation between Pr(Ⅲ) and Nd(Ⅲ)by a so-called kinetic "push and pull" system consisting of [A336][NO_3] and DTPA in a column extractor.It is revealed that,when organic extractant [A336][NO_3] is continuously pumped into the column extractor in the form of dispersed oil droplets and at the same time DTPA was injected into the aqueous feed solution whet the extraction was just started,the separatiot factor of Pr(Ⅲ) to Nd(Ⅲ),βPr/Nd,increased obviously with the time,and could even achieve 21.7.Such an amazing increase in β_(Pr)/Nd value might be due to the extraction rate of Pr(Ⅲ) by [A336][NO_3] oil droplets being faster than that of Nd(Ⅲ),while the complexing rate of Nd(Ⅲ) with DTPA in the aqueous solutions being faster than that of Pr(III).The opposite order of the two rates for Pr(Ⅲ) and Nd(Ⅲ) result in their kinetic "push and pull" separation.In contrast,the β_(Pr)/Nd value in traditional thermodynamic separation reported in previous literatures is only around 5 or even less,even though using the same extractant [A336][NO3] and DTPA but by previously adding DTPA into the aqueous feed solutions for pre-complexing of Pr(Ⅲ) and Nd(Ⅲ).Various effects from the pH and addition amount of DTPA aqueous solutions,LiNO_3 concentrations in initial aqueous feed solutions,the initial concentration ratios of Pr(Ⅲ) to Nd(Ⅲ) ions,the initial pH of aqueous feed solutions,and the concentrations of [A336][NO_3] in organic phases,on the kinetic separatiot of Pr(Ⅲ) and Nd(Ⅲ) are discussed.The present work highlights a promising approach for separation of rare earths or other targets with extreme similarity in physicochemical properties.     

On the mechanism of iron oxide reduction by carbon

A theoretical analysis has been made to determine the conditions under which the reduction of iron oxide by carbon takes place according to the 2 step mechanism involving the Boudouard reaction. This is based on the concept of minimum temperature of reduction (T _min) below which the Boudouard reaction does not affect the reduction process. The effect of variables such as carbon reactivity, total pressure and so forth onT _min has been studied. TheT _min can be used to determine if metallization is possible under a given set of conditions.     

Study on separation of rare earth elements in complex system

The effect of the feed acidity, acetic acid concentration and rare earth concentration on the distribution ratio, separation coefficient and extraction capacity of light rare earth elements were studied in the P204(DEHPA)-HCl system and P507(HEH/EHP)-HCl system both containing acetic acid, respectively. The results showed that the distribution ratio and separation coefficient decreased with increasing of acidity, and increased with increasing of acetic acid concentration and rare earths concentration, and the extraction capacity increased with increasing of acetic acid concentration. When pH value of feed was 2.0, [RE]/[acetic acid] was 1:1 and rare earth concentration 0.35 mol/L, in P204(DEHPA)- HCl system with acetic acid, the maximum separation coefficient(β) reached to β_{Ce /La}=4.09, β_Pr/Ce=1.96 and β_Nd/Pr=1.53, and the separation ability of this extraction system was better than P507(DEHPA)-HCl system.     

Mathematical Modelling of the Liquid-Liquid Extraction Separation of Rare Earths

Abstract

An empirical mathematical model has been developed for the simulation of an integrated solvent extraction circuit consisting of an extractor, scrubber and a stripper. This model is designed to simulate the separation of any lanthanide from a mixed lanthanide feed. The Kremser equation is used to calculate the separation occurring in each section of the circuit. The inputs required for the simulation are the feed composition, separation factors, equilibrium data of the key element under a wide range of conditions, the number of stages and flow rates of the aqueous and organic streams in the circuit. This model has been validated with the experimental data for the separation of Nd from a mixed lanthanide chloride feed with 2-ethylhexyl phosphonic acid mono 2-ethyl-hexyl ester (EHPNA) as an extractant.     

Solubility of oxygen and sulfur in copper-iron mattes

The concentrations of oxygen and sulfur in unsaturated and magnetite-saturated Cu-Fe mattes were measured as a function of oxygen and sulfur pressures and iron metal weight fraction of the matte (W _Fe = wt Fe/(wt Fe + wt Cu)). The liquid matte samples were equilibrated with streams of gas of known pressures of S₂ and O₂ at 1468 K. Empirical correlation equations were developed to describe the experimental results. The correlation for oxygen in unsaturated matte is wt pct O = 2.50P _{O 2} ^0.200 P _{S 2} ^-0.142 (1 + 9.0W _Fe ^2.19, and in magnetite-saturated matte it is wt pct O = 0.14 + 2.39W _Fe + 12.0W _Fe ² for 0.001 <P _{S 2} ≤ 0.01 atm and it is wt pct O = −3.06 + 2.39W _Fe + 12.0W _Fe ² − 1.60 logP _{S 2} for 0.01 <P _{S 2} < 0.023 atm. A single complex equation ofP _{O 2},P _{S 2}, andW _Fe describes the sulfur concentrations in both unsaturated and magnetite-saturated mattes. An erratum to this article is available at .     

Study of K~+ doping on structure and properties of γ-Ce_2S_3

In this study,K~+-doped γ-Ce_2 S_3 was successfully prepared via a gas-solid reaction method using CeO_2,K_2 CO_3,and CS_2 as raw materials.The effects of the suitable sulfide system and different molar ratios of K to Ce(n_(K/Ce)=0-0.30) on the phase composition,crystal structure,chromaticity and thermal stability ofγ-Ce_2 S_3 were systematically investigated.Pure γ-Ce_2 S_3 was obtained by calcining the doped samples at840℃ for 150 min.After calcination at the same temperature the undoped K+samples exhibit a pure α-phase.Samples with a K/Ce molar ratio(n_(K/Ce)) of 0.10-0.25 comprise only the γ-phase;and when n_(K/Ce) exceeds 0.25,a new heterogeneous phase,KCeS_2,emerges.For values of n_(K/Ce) in the range of0-0.25,the γ-Ce_2 S_3 lattice parameters gradually increases with increasing K~+ content.When n_(K/Ce)exceedes 0.25,the lattice parameters remains unchanged.As n_(K/Ce) increased,the synthesized color gradually changes from red to orange—red and finally,to yellow.The redness value a~* reaches the maximum(L~*=33.86,a~*=36.68,b~*=38.15) when n_(K/Ce)=0.10,The n_(K/Ce)=0.10 composition continues to exhibit the y-phase after heat treatment at 420℃ for 10 min in air.The K+doping fills the internal vacancies of γ-Ce_2 S_3 and formed a solid solution,which is beneficial for the stability of its lattice,thus improving the thermal stability of γ-Ce_2 S_3(from 350 to 420℃).     

Thermodynamic modeling of Zr-Ti-Cu-Ni-Be bulk metallic glass

In the present thermodynamic model, the optimization of bulk metallic glass forming compositions in Zr-Ti-Cu-Ni-Be system using enthalpy of chemical mixing (ΔH_chem) as thermodynamic, mismatch entropy (ΔS _σ /k_B) as topological and configurational entropy (ΔS_config/R) as statistical parameters were studied. The product of ΔH_chem and ΔS _σ /k_B which is termed as ΔP_HS in the ΔS_config/R range of 0.9 to 1.0 can be strongly correlated to glass forming ability. Using the contributions of ΔP_HS values of all ternary compositions possible in Zr-Ti-Cu-Ni-Be system, the final quinary composition is designed. Composition obtained from present model was found to closely match with compositions reported in literature.     

Effect of constraint on fracture parameters of piping materials

Fracture behaviour under quasi-static tearing load has been studied through fracture toughness tests on SA333 Grade 6 and 20MnMoNi55 steels using single-edge notched bend (SENB) specimens. To understand the response of variation of constraint, J-R curves were obtained from specimens precracked to a/W ratio in the range of 0.25 to 0.75, in steps of approximately 0.1. Stretch zone widths (SZW) were measured on the fractured surfaces of broken specimens. The stretch zone dimensions that were determined have been used in conjunction with the experimentally derived J-R curve to obtain a value of the ductile fracture toughness parameter J _SZW. The initiation toughness, J _i, obtained at the intersection of the blunting line and the power-law fit to the J-R curve, and the critical toughness, J _c, determined following the procedure of the ASTM standard, were estimated. Comparisons of J _SZW with J _i and J _c have been made for 20MnMoNi55 and SA333 steels as a function of the a/W ratio. The J _i and J _c values are higher at lower a/W, i.e. under low constraint, and fall with increasing a/W. A loss of constraint thus enhances these parameters. It was observed that J _SZW does not effect by a/W, and that its value is lower bound to J _i and J _c values for both the materials investigated.     

Investigation of Cobalt (II)-Tungsten (VI)-Oxide Reduction in Hydrogen: Part I

CoWO₄ reduction in dry hydrogen, at temperatures lower than 550°C brings about an intermediate unstable phase of cubic structure, (a = 10.846Å) and composition Co₄W_2.5O; the tungsten which is not retained in this phase appears in the form ofβ- W (A-15 structure,a = 5.039Å). Another phase (noted ?@#@) which does not give any X-ray diffraction pattern forms by further reduction of Co₄W_2.5O. The whole set of these transformations is characterized by a kinetic global law described by a Johnson-Mehl equationξ = 1- exp(-kt) ^3/2 and an activation energy, 24 kcal/Mole, determined byβ-W continuous growth. The rate of C03W crystallization from? becomes substantial, only from around 700°C, temperature at whichβ-W is also converted into α-W. The final alloy Co₇W₆ is formed from about 800°C on, through reaction of Co₃W and α-W. In wet hydrogen, WO₂ forms instead ofβ- W and Co₄W_2.5O—which may be stabilized under certain conditions-is directly reduced into Co₃W after WO₂ reduction into α-W.     

Study on the Formation and Characterization of the Intermetallics in Friction Stir Welding of Aluminum Alloy to Coated Steel Sheet Lap Joint

Multimaterial fabrication such as joining of steel and aluminum is currently prominent in a variety of industries. Friction stir welding is a novel solid-state welding process that causes good joint strength between steel and aluminum. However, the phenomenon contributing significant strength at the interface is not yet clear. In the present study, the interface of the friction stir lap-welded aluminum and coated steel sheet having joint strength maximum (71.4 pct of steel base metal) and minimum, respectively, under two parameter combinations, i.e., 1000 rpm 50 mm min^?1 and 500 rpm 100 mm min^?1, was exclusively characterized by X-ray diffraction, transmission electron microscopy (TEM), concentration profile, and elemental mapping by electron-probe microanalysis. A TEM-assisted EDS study identifies the morphologies of large size Al₁₃Fe₄ and small size Fe₃Al-type intermetallic compounds at the interface. The diffusion-induced intermetallic growth (thickness) measured from a backscattered image and concentration profile agreed well with the numerically calculated one. The growth of these two phases at 1000 rpm 50 mm min^?1 is attributed to the slower cooling rate (~3.5 K/s) with higher diffusion time (44 seconds) along the interface in comparison to the same for 500 rpm 100 mm min^?1 with faster cooling rate (~10 K/s) and less diffusion time (13.6 seconds). The formation of thermodynamically stable and hard intermetallic phase Al₁₃Fe₄ at 1000 rpm and travel speed 50 mm min^?1 in amounts higher than 500 rpm and a travel speed of 100 mm min^?1 results in better joint strength, i.e., 71.4 pct, of the steel base metal.     

Effects of plasticity on the crack propagation resistance of a metal/ceramic interface

Fracture experiments have been conducted on a gold/sapphire interface. The interface is found to fail by interface separation in a nominally “brittle” manner with a critical strain energy release rate, G_c ≈ 50 Jm⁻², substantially larger than the work of adhesion, W_ad ≈ 0.5 Jm⁻². Evidence of plastic deformation on the gold fracture surface, such as blunting steps and slip steps, suggest that plastic dissipation is the primary contribution to the measured G_c. Calculations suggest that the majority effect occurs in the plastic zone through the crack wake. The interface is also found to be susceptible to slow crack growth.     

Thermodynamic studies of the V3S4−V5S8 system at temperatures from 650 to 800°C

Phase equilibria in the composition range between VS_1.33 and VS_1.60 were studied by varying the partial pressure of sulfur at 650, 700 and 750°C. Phase separation in the V₃S₄ phase was observed at these temperatures in contrast to the results in the previous work at 800°C. The separated phase was regarded as V₂S₃. The standard free energies of sulfurization from the stoichiometric V₃S₄ to the stoichiometric V₅S₈ at above temperatures have been calculated from the data of the equilibrium partial pressure of sulfur and each activity at which phase transition was caused. The standard enthalpy and the entropy changes of the above sulfurization reaction have been evaluated, from the free energy data obtained.     

萃取流量参数对稀土槽分布的影响

以国内某稀土厂生产萃取线A的La/CePr/Nd萃取过程为研究对象,通过采集和分析萃取槽各级有机相和水相中稀土元素的含量,明确不同皂化有机相流量、料液流量、酸流量等条件对各级稀土元素含量分布和稀土总量的影响。适当提高皂化有机相流量、料液流量和酸流量,可使水相出口处La的含量较高,从而保证出口产品纯度,但会使55级有机相出口处有机相中Ce组分含量较高,Pr、Nd组分含量较低,增加下一系列分离Pr、Nd的压力。     

The activities of sulfide and oxide components and the solubility of oxygen in copper-iron-sulfur-oxygen mattes at 1300 °C

The activities of iron and copper and the solubilities of oxygen in copper-iron-sulfur-oxygen mattes have been determined by equilibrating mattes with CO−CO₂−SO₂ gas mixtures of fixed partial pressures of oxygen and sulfur and equilibrating a small mass of platinum with the melt. Iron and copper transferred from the matte to form a platinum-iron-copper alloy in which the activities of iron and copper are the same as in the matte. The activities of iron and copper in the matte were then determined from knowledge of the activities of iron and copper in the system platinum-iron-copper. Sulfides ofW _Fe=0.1, 0.3, and 0.5 were studied, whereW _Fe=wt pct Fe/(wt pct Fe+wt pct Cu), and sulfur pressures of 0.005, 0.0158, and 0.025 atm and oxygen pressures of 3.16×10⁻¹⁰, 7.94×10⁻¹⁰, 2.00×10⁻⁹, and 3.16×10⁻⁹ were used. The activity of copper, which varied in the range 0.06 to 0.165, decreases with increasingp _{O 2} at constantW _Fe andp _{S 2} and decreases with increasingp _{S 2} at constantW _Fe and constantp _{O 2}. The activity of iron, which varied in the range 0.002 to 0.06, increases with increasingp _{O 2} at constantW _Fe andp _{S 2} and decreases with increasingp _{S 2} at constantW _Fe andp _{O 2}. The activities of the components Cu₂S, FeS, Cu₂O, FeO, and Fe₃O₄ were calculated from the activities of iron and copper, the partial pressures of oxygen and sulfur, and the approapriate equilibrium constants. The variations of the activities of these components with matte grade, oxygen pressure, and sulfur pressure are presented and discussed. Within the range of experimental conditions studied, the solubility of oxygen in the melts is given by wt pct O=2.59pO₂/0.225pS₂/−0.18 (1+9.0W _Fe)^1.86     

Gradient Structure of the Layer Applied to Hardox 450 Steel by Fe–C–Cr–Nb–W Powder Wire after Electron-Beam Treatment

Surfacing with composite coatings strengthened by carbide, boride, and other particles is currently of great interest in materials physics. The performance of the applied layer is primarily determined by the phase composition of the coating. To permit the selection of coatings capable of withstanding extremal operating conditions, including high loads and abrasive wear, their properties and structure must be investigated in detail. In the present work, state-of-the-art techniques in materials physics are used to study the structure, phase composition, and tribological properties of coatings applied to Hardox 450 low-carbon martensitic steel by Fe–C–Cr–Nb–W powder wire and then subjected to electron-beam treatment. The electron-beam parameters are as follows: in the first stage, energy density per pulse E_S = 30 J/cm²; pulse length τ = 200 μs; and number of pulses N = 20; in the second stage, E_S = 30 J/cm²; τ = 50 μs; and N = 1. These conditions are selected on the basis of calculations of the temperature field formed in the surface layer of the material by a single pulse. It is found that electron-beam treatment of an applied layer of thickness about 5 mm leads to modification of a thin surface layer (about 20 μm), consisting largely of α iron and the carbide NbC; small quantities of the carbides Fe₃C and Me₆C (Fe₃W₃C) are also present. This modified surface layer differs from the unmodified coating mainly in terms of the morphology and dimensions of the secondary-phase inclusions. In the modified surface layer, the inclusions are smaller and take the form of thin layers along the grain boundaries. In the unmodified coating, the inclusions are mainly rounded particles, chaotically distributed within the grain. After electron-beam treatment, the wear resistance of the applied layer increases by a factor greater than 70 with respect to Hardox 450 steel, while the frictional coefficient is significantly less (about a third as much).     

Dissolution rate of lead(II) oxide in an equimolar KCl-PbCl2 melt

Dissolution rates (W) of lead(II) oxide in a KCl-PbCl₂ equimolar melt are determined experimentally using the gravimetric method at T = 773, 823, and 873 K. It is shown that, as the temperature increases from 773 to 873 K, the initial magnitude of W increases from 23.9 to 45.6 mg/(cm² min) with a conventional roughness coefficient of 10. Then the values of W for all temperatures are leveled, being close to zero after 25 min, which indicates the diffusion mode of the process in natural convection conditions. The activation energy of the interaction between PbO and the KCl-PbCl₂ melt was 37.370 ± 0.118 kJ/mol. The limiting concentration of PbO in the equimolar KCl-PbCl₂ melt was determined, being 9.1, 10.6, and 13.5 wt % at T = 773, 823, and 873 K, respectively.     

Study on separation technology of Pr and Nd in D2EHPA-HCl-LA coordination extraction system

The separation coefficient of Nd/Pr was lower in D₂EHPA-HCl system. Pointing to this problem, the effect of the acidity of feed and the concentration of lactic acid on the distribution ratio, separation coefficient and extraction capacity was investigated in unsaponified D₂EHPA-HCl-LA system, and the regression equations were calculated in this paper. The results showed that the distribution ratio and separation coefficient both increased with decreasing of feed acidity and increasing of the lactic acid concentration, and the extraction capacity increased with increasing of lactic acid concentration in D₂EHPA-HCl-LA system. When the pH value of the feed was 3.5 and lactic acid concentration was 0.6 mol/L, the max separation coefficient was 1.57, and the extraction capacity was 27.87 g/L.     

Thermodynamic studies of the V3S4-V5S8 system at temperatures from 650 to 800?C

Phase equilibria in the composition range between VS1.33 and VS_1.60 were studied by vary-ing the partial pressure of sulfur at 650, 700 and 750‡C. Phase separation in the V3S4 phase was observed at these temperatures in contrast to the results in the previous work at 800‡C. The separated phase was regarded as V₂S₃. The standard free energies of sul-furization from the stoichiometric V₃S₄ to the stoichiometric V₅S₈ at above temperatures have been calculated from the data of the equilibrium partial pressure of sulfur and each activity at which phase transition was caused. The standard enthalpy and the entropy changes of the above sulfurization reaction have been evaluated from the free energy data obtained.