不同萃取体系分离微生物浸出液中低含量镍钴

采用P507一Cyanex272混合萃取体系分离微生物浸出液中的镍钴,实验结果表明该体系具有较好的协萃效应.结合低含量镍钴的微生物浸出液体系高酸度、低钴镍比的特点,对比了P507、Cyanex272和P507-Cyanex272三种萃取体系对镍钴的萃取分离效果,确定了在初始pH值1.5~2.2、对应的平衡pH值4.00~5.25条件下P507-Cyanex272协萃体系有较好的镍钴分离效果.系统考察了室温28℃下协萃体系各影响因素对镍钴分离的影响,确定协同萃取的最佳工艺为:P507与Cyanex272摩尔比3:2,皂化率60%,萃取剂体积分数10%,有机相(由萃取剂与煤油组成)和水相体积比1:4.在此条件下钻的一级萃取率为99.16%,镍钻分离系数为932.59.      

Extraction kinetics of neodymium from chloride medium using HEH/EHP saponified with magnesium bicarbonate solution

Magnesium bicarbonate solution is considered as an environmentally friendly extractant saponification agent for the solvent extraction of rare earth elements due to its advantage of minimum water pollution.In order to reveal the extraction regularity, optimize production-process and guide the use of this new extraction system, the extraction of Nd(Ⅲ) in chloride medium with HEH/EHP saponified by magnesium bicarbonate solution was investigated with the self-designed constant interfacial area cell. Besides, the effects of stirring rate, temperature, specific interfacial area and concentration of Mg-HEH/EHP on the extraction rate of Nd(Ⅲ) were systematically investigated. Results show that, the rate of extraction is governed by both diffusion and chemical reaction, and the extraction reaction takes place at the interface. The apparent activation energy of the extraction reaction is 16.88 kJ/mol. The corresponding rate equation is deduced. The mechanisms and rate-determining step are speculated based on interfacial reaction models, which is consistent with the experimental results.     

Solvent Extraction Separation and Recovery of Components from Scraps Containing Nickel and Cadmium

The solvent extraction separation of Cd²⁺ and Ni²⁺ by commercially available dialkyl-phosphoric (D2EHPA), phosphonic (PC-88A) and phosphinic acids (Cyanex 272) has been investigated. In each case cadmium is extracted at lower pH values than nickel. Under comparable conditions PC-88A and Cyanex 272 have an excellent ability to separate cadmium from nickel. The optimum pH ranges are 3.5-4.5 with PC-88A and 4.8-6.0 with Cyanex 272. The feasibility of cadmium-nickel separation by Cyanex 272 extractant have been tested in pilot-plant scale. Cadmium and nickel salt solutions have been recovered from solutions originating from the leaching of the electrode materials of Ni-Cd battery scraps. The nickel and cadmium salt solutions have further been processed to metal oxidehydrates which have been found in laboratory lists as suitable for production of negative and positive electrode materials of new Ni-Cd batteries.     

Studies on synergistic solvent extraction of rare earth elements from nitrate medium by mixtures of 8-hydroxyquinoline with Cyanex 301 or Cyanex 302

Synergistic solvent extraction of rare earth elements (REEs) from nitrate medium was investigated with mixtures of 8-hydroxyquinoline (HQ) and acidic organophosphorus extractants,bis(2,4,4-trimethylpentyl) dithiophosphinic acid (Cyanex 301) and bis(2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex 302).The extraction behavior of Cyanex 301/Cyanex 302 and their binary mixtures with HQ towards several lanthanoids (La,Nd,Sm,Tb,Ho,Tm) and yttrium (Y) was investigated.The separation ability of REEs was studied according to the various extraction effects.The extraction mechanisms for yttrium were studied with the methods of slope analysis and constant moles in the synergistic systems.The extracted compounds,the equilibrium constants,and thermodynamic functions were also determined.     

Determination of optimum process conditions for the extraction and separation of zirconium and hafnium by solvent extraction

Taguchi's method was used to determine the optimum conditions for separation of zirconium from hafnium by solvent extraction. The experimental conditions were studied in the range of 0.1 to 2.0 M for three different acids and TBP, D2EHPA or Cyanex 272 as extractant. The optimum extraction of zirconium was 71% when 2.0 M nitric acid and Cyanex 272 were used. The optimum zirconium/hafnium separation was also achieved using this combination.     

Study on the diffusion kinetics of adsorption of heavy rare earth with Cyanex272-P507 impregnated resin

Kinetics of adsorption of heavy rare earth with Cyanex272-P507 impregn ated resin was studied. The influences of temperature,concentration,granularit y of resin on the exchange degree were investigated by the limited bath method. The result showed that the controlling factor of RE3+/H+ diffusion on Cyanex272-P507 extraction resin was particles diffusion. The process of diffuse kinetics f itted well with the expression developed by Body model. The apparent activation energy was determined as 23.20 kJ/mol. The reaction order was 0.452. In addition,the constant of particles diffusion(D0) was 1.352×10-8 m2/S and the entropy of diffusion was-47.055 J/(mol·K).     

新型萃取剂Cyanex272在溶剂萃取稀土中的应用

通过新型萃取剂Ｃｙａｎｅｘ２７２同Ｐ２０４和Ｐ５０７的对比预示了Ｃｙａｎｅｘ２７２分离稀土的景，并介绍了近期Ｃｙａｎｅｘ２７２溶剂萃取分离稀土的研究动态，在此基础上提出几点建议。     

Rate Processes in Solvent Extraction of Metal Ion

Abstract

The mechanism and kinetics of metal extraction with several extractants, including chelating agents, acidic organophosphorous extractant and neutral extractants are discussed in this paper.

Firstly the extraction rate of metal ion for the general extraction system is formulated by solving the diffusional equation with chemical reaction, in which the interfacial reaction is considered by the boundary conditions. The overall rate expressions of the complex formation with chelating agents are obtained both in aqueous phase and at the interface. The general formula of the extraction rate is simplified by considering the rate-determining steps.

Next, the extraction rate of metal ion with chelating agents and acidic organophosphorous extractants is discussed. For the chelating agents, the most important properly to determine the locus of complex formation is the distribution constant between the organic and aqueous phases. The contribution of the interfacial reaction to the extraction rate increases with the increase in the distribution constant of chelating agents. The extraction rate of many metal ions with acidic organophosphorous extractant are determined by the diffusion process of final complex in the organic phase.

Finally, the extraction rate of palladium ion with some neutral extractants is also discussed. The extraction rate is determined by the complex reaction in the aqueous phase and at the interface. The contribution of the interfacial reaction increases with the distribution constant of extractants.     

Solvent extraction characteristics of thiosubstituted organophosphinic acid extractants

Organophosphorus reagents are well known in solvent extraction. Commercial operations for the separation of cobalt from nickel have been successfully carried out using organophosphoric, -phosphonic, and -phosphinic acid extractants. Two new reagents in this class are the mono and dithio analogs of the commercial dialkylphosphinic acid, Cyanex 272. The replacement of oxygen by sulfur in these reagents enables extraction to be carried out at much lower pH.Characterization of Cyanex 272, Cyanex 302 (bis-(2,4,4-trimethylpentyl)-thiophosphinic acid), and Cyanex 301 (bis-(2,4,4-trimethylpentyl)-dithiophosphinic acid) has been undertaken. A comparison of the solvent extraction behavior of metallurgically important first-row transition metal ions from acidic sulfate solution by these reagents is reported. Distribution coefficients shift to lower pH with increasing sulfur substitution and decreasing pK_a of the extractant, the greatest effect being observed for nickel. Stoichiometry of the extraction reactions, and the nature of the metal complexes formed have been determined using slope analysis techniques and spectroscopic measurements.     

Cyanex 272在溶剂萃取分离钴镍中的研究与应用

评述了新型有机膦类萃取剂Ｃｙａｎｅｘ ２７２ 在钴镍溶剂萃取分离中的应用进展, 并与现行的有机磷类萃取剂进行了比较。     

Study on Transfer and Interfacial Kinetics of Neodymium and Samarium in Membrane Based Extraction

Ｔｈｅｅｘｔｒａｃｔｉｏｎｔｅｃｈｎｏｌｏｇｙｏｆｈｏｌｌｏｗｆｉｂｂｅｒｍｅｍｂｒａｎｅ (ＨＦＭ ) ,ｗｈｉｃｈｗａｓｄｅｖｅｌｏｐｅｄｉｎｅａｒｌｙ 1 980ｓ ,ｉｓａｎｅｗｋｉｎｄｏｆｓｅｐａｒａｔｉｏｎｍｅｔｈｏｄｃｏｍｂｉｎｅｄｐｒｏｃｅｓｓｅｓｏｆｌｉｑｕｉｄ -ｌｉｑｕｉｄａｎｄｍｅｍｂｒａｎｅｅｘｔｒａｃｔｉｏｎ .Ｔｈｉｓｍｅｔｈｏｄｃａｎｏｆ ｆｅｒｓｅｖｅｒａｌａｄｖａｎｔａｇｅｓｃｏｍｐａｒｅｄｗｉｔｈｃｏｎｖｅｎ ｔｉｏｎａｌｅｘｔｒａｃｔｏｒｓ[1～ 2 ] .Ｉｔｃａｎａｌｓｏｐｒｏｖ…     

Colorimetric estimation and some physicochemical properties of purified Cyanex 272

A technique for the colorimetric estimation of purified Cyanex 272 has been developed. The technique consists of the digestion of pure sample or its aqueous solution with concentrated nitric acid (70%)–perchloric acid (70%) mixture for 1 h. The oxidizing mixed acid quantitatively converts Cyanex 272 to a clear solution of orthophosphate that can be easily estimated by the molybdenum-blue colorimetric method at 830 nm. The method is sensitive with a molar extinction coefficient of ∼2.6×10⁴ and reproducible within ±2%. Applying this technique of analysis, the dimerization constant (K₂), distribution or partition coefficient (K_d) and ionization constant (K_a) of the purified Cyanex 272 (bis-2,4,4-trimethylpentylphosphinic acid, BTMPPA) have been estimated to be 190, 53 and 5.52×10⁻⁴, respectively.     

Study on the diffusion kinetics of adsorption of heavy rare earth with Cyanex272-P507 impregnated resin

Kinetics of adsorption of heavy rare earth with Cyanex272-P507 impregnated resin was studied. The influences of temperature, concentration, granularity of resin on the exchange degree were investigated by the limited bath method. The result showed that the controlling factor of RE³⁺/H⁺ diffusion on Cyanex272-P507 extraction resin was particles diffusion. The process of diffuse kinetics fitted well with the expression developed by Body model. The apparent activation energy was determined as 23.20 kJ/mol. The reaction order was 0.452. In addition, the constant of particles diffusion (D₀) was 1.352×10^?8 m²/S and the entropy of diffusion was ?47.055 J/(mol·K).     

Solvent extraction and separation of light rare earth elements (La,Pr and Nd) in the presence of lactic acid as a complexing agent by Cyanex 272 in kerosene and the effect of citric acid,acetic acid and Titriplex III as auxiliary agents

At present, the use of rare earth elements (REEs) has become an inevitable necessity in many modern industries. In general, liquid extraction is the best commercial method for extracting REEs due to its ability to control high volumes of liquids with electrical load. With the aim of improving a separation technology that would be superior to the existing extraction systems, the extraction behaviors of La(III), Pr(III), and Nd(III) from an HCl medium with Cyanex 272 in the presence of the complexing agent lactic acid (HLac) and auxiliary agents citric acid (H₃Cit), acetic acid (HAc), and Titriplex III have been reported. The effect of pH and lactic acid concentration has been examined. The use of lactic acid as a complexing agent leading to a high extraction of REEs with Cyanex 272 at pH = 5 was compared with systems without lactic acid. The results show that the use of acetic acid along with lactic acid leads to an increase in the extraction percentage of LREEs. While use of citric acid and Titriplex III reduces the extraction percentage of LREEs. Finally, the presence of Titriplex III together with lactic acid could lead to an increase in the separation factor of Pr and Nd.     

Mass Transfer in Slag Refining of Silicon with Mechanical Stirring: Transient Interfacial Phenomena

Experiments have been carried out to study the rates of mass transfer between liquid silicon and CaO-SiO₂ slag with impeller stirring at 1823 K (1550 °C). The occurrence of transient interfacial phenomena related to the mass transfer of calcium has been observed; the evidence suggests that the reduction of calcium oxide at the interface leads to a rapid, temporary drop in the apparent interfacial tension. At low apparent interfacial tension, mechanical agitation facilitates the dispersion of metal into the slag phase, which dramatically increases the interfacial area; here, it has been estimated to increase by at least one order of magnitude. As the reaction rate slows down, the apparent interfacial tension increases and the metal recoalesces. The incidental transfer of calcium very likely promotes the transfer of boron by increasing the interfacial area. Mechanical mixing appears to be an extremely effective means to increase the reaction rate of boron extraction and could feasibly be implemented in the industrial slag refining of silicon to improve reaction rates.     

The extraction mechanism of thulium in di(2-ethyl hexyl) phosphoric acid-nitric acid system

Distribution ratios (D) and interfacial mass transfer coefficients in the case of extraction of thulium(III) with di(2-ethyl hexyl) phosphoric acid (HDEHP) in cyclohexane have been measured at different concentrations of nitric acid and HDEHP as well as at various stirring speeds of the two phases in a constant interface cell. From a study of the effect of stirring on the mass transfer coefficients it is observed that the overall extraction process is controlled by interfacial chemical reaction as well as by diffusion of interfacial chemical species across the interface. The latter is dependent on the rate of stirring. At stirring rates up to ～75 min^?1 the diffusional process is the rate determining step. On the other hand, when the stirring rate is ～400 min^?1, the diffusional step becomes very fast. At such high stirring speeds, the system belongs to a true kinetic regime, which was evaluated through computer simulation.     

Extraction technology of purification of sulfate nickel solutions of impurities with the use of dialkylphosphine acid

The data of laboratory investigations of the removal of impurities (Fe, Cu, Zn, Mg, Ca) from sulfate nickel solutions are presented. It is shown that Cyanex 272 [di(2,4,4-dimethylpenthyl)phosphinic acid] is the most efficient extractant. For two extraction steps by a nickel form of Cyanex 272 from a solution (after iron purification) that contained: Ni 120–130, Cu 0.8–1.0, Zn 3.0–4.0, Mg 1.5–2.0, Ca 0.4–0.8, and Fe 0.01–0.02 g/l, raffinates of the following composition are obtained: Ni 120–130, Cu, Zn, and Fe ≤ 2 × 10^?3 each, Mg ≤ 0.1, and Ca 0.2–0.3 g/l. Purification of raffinates of organic impurities (extractant, diluent) after extraction is performed on the DAK-activated charcoal. Reextraction of metals and, correspondingly, extractant regeneration, is easily performed by solutions of mineral acids (H₂SO₄ and HNO₃). Extraction of nickel from the solution at the extraction step is ≥99.8%.     

Rates of extraction of cobalt from an aqueous solution to D2EHPA in a growing drop cell

A technique has been developed to study the rate of extraction of cobalt from an aqueous phase into a growing drop of heptane containing di(2-ethylhexyl) phosphoric acid (D2EHPA). The hydrodynamics of the growing drop are accounted for. Experiments have been carried out at the single temperature of 25 ± 0.1°C Sphere the pH, aqueous cobalt concentration and the organic D2EHPA concentration have been varied. A mathematical model is given which is based upon the control of rate by mass transfer with chemical reaction. The model fits the experimental data well considering the experimental errors and the complexity of the transfer of solute where fresh surfaces are continually produced by the growing drop.     

DIBK-TBP体系萃取铪和锆的动力学研究

在恒界面池中研究DIBK-TBP协同萃取体系萃取铪、锆的动力学,考察了温度、界面积和搅拌强度等对萃取速率的影响。结果显示,DIBK-TBP体系萃取铪和锆的过程符合一级动力学反应;对铪的萃取为相内反应和扩散共同影响的混合控制类型,表观活化能-43.106kJ/mol;对锆的萃取与搅拌强度、比界面积无关,为相内反应控制类型,表观活化能-16.024kJ/mol。     

Dynamic and equilibrium interfacial phenomena in liquid steel-slag systems

The equilibrium interfacial energy between a liquid iron alloy and a liquid slag is a key physical parameter in the design of steel-refining processes as high interfacial energies are desired to avoid emulsification of slag in steel and the creation of casting defects. During a chemical reaction between a liquid iron alloy droplet and a liquid slag, it is possible to observe by X-ray photography a number of dynamic interfacial phenomena such as droplet flattening, interfacial turbulence, and spontaneous emulsification that can potentially lead to serious processing problems. These dynamic phenomena have been studied during reactions between Fe-Al and Fe-Ti alloys and silica-containing slags, and the presence of significant interfacial disturbance has been observed during the times of high reaction rate between the slag and the metal. It is suggested that interfacial chemical reactions induce Marangoni and natural convection at the slag-metal interface. This interfacial flow gives rise to interfacial waves due to a Kelvin-Helmholtz instability. The waves grow, become unstable, and lead to spontaneous emulsification of slag in steel and steel in slag. Experiments using industrial samples and controlled laboratory tests have indicated that this phenomenon may be more common than once thought and could lead to some serious problems in the processing of steel alloys containing high quantities of aluminum and/or titanium. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium,” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS.