THE KINETICS OF COBALT AND NICKEL EXTRACTION USING HEHEHP

The kinetics of the extraction of cobalt and nickel using purified mono 2-ethyl hexyl phosphonic acid mono 2-ethyl hexyl ester (HEHEHP) were studied using the Rotating Diffusion Cell (RDC) apparatus. The extraction of cobalt was Investigated over a wide range of cobalt concentration, extractant concentration, pH and temperature conditions. Nickel extraction was examined over a wide range of nickel concentrations.

The kinetic data were treated according to both interfacial and mass transfer with chemical reaction (MTWCR) models. The MTWCR model adequately described the kinetic data for both the cobalt and nickel extraction experiments. No variation of an interfacial model was adequate to describe the data. In the MTWCR model, the extraction rate was shown to be controlled by a mechanism involving diffusion of the extractant into the aqueous phase boundary layer with subsequent reaction involving the addition of the first ligand to the cobalt or nickel ion. This extraction mechanism was substantiated by supplementary results including the activation energy determination which indicated mixed diffusion and chemical reaction control, the significant measured rate of partition of the extractant to the aqueous phase, and the values of the cobalt and nickel complex formation constants in the aqueous phase.     

EXTRACTION OF COPPER SALTS WITH A MIXED EXTRACTANT

Equilibrium distribution measurements and spectroscopic studies were undertaken in order to investigate the extraction of copper salts into a mixed extractant consisting of 2-ethyl hexanoic acid and trioctylamine in toluene. The predominant species in the organic phase was found to be a large ion pair of the type [R₃NH⁺]₂[CuX₂(R'COO-)₂]A By contacting the copper-loaded organic phase with water, an aqueous salt solution, or dilute HCI, copper can easily be back-extracted into the aqueous phase.     

2-乙基己基膦酸单(2-乙基已基)酯萃取钴的动力学

引言膦类萃取剂萃取分离钴、镍已应用于工业生产，并在湿法冶金和其它领域得到广泛应用．对膦类萃取剂萃取钴的动力学已有多方面研究~〔1～6〕，但2-乙基已基磷酸单（2-乙基己基)酯（简称P_507,HEHEHP，H_2A_2）萃取钴的动力学研究报道较少~〔4,6〕，尤其缺乏不同水相介质对HEHEHP萃取钴的萃取速度的影响及其机制的探讨．本文在恒定界面池内，研究了HEHEHP-加氢煤油-NaNO_3体系萃取钴的动力学，主要在动力学坪区考察了萃取体系中各种因素和不同水相介质对萃取速度的影响，并对其机理进行探讨．l　实验部分1.1　仪器和试剂恒定界面…     

MACROSCOPIC AND MICROSCOPIC STUDIES ON THE INFLUENCE OF DIFFERENT ANIONS ON THE EXTRACTION OF NEODYMIUM WITH A NEUTRAL ORGANOPHOSPHINE EXTRACTANT

The determination of the thermodynamic constants for the extraction of the neodyrriium salts, Nd(NCS)₃, Nd(ClO₄)₃ and Nd(NO₃)₃ with Di(l-methyl-heptyl) methyl phosphonate, and the crystal and molecular structures of the respective extracted complexes with triphenyl phosphine oxide, used as a model molecule of neutral organophosphine extractants, are reported here. The influence of the different anions on these systems has been interpreted microscopically and macroscopically. The IR data of the saturated organic phases and the solid complexes have been discussed as well.     

THE KINETICS OF ZINC,COBALT AND NICKEL EXTRACTION IN THE D2EHPA-HEPTANE-HC104 SYSTEM USING THE ROTATING DIFFUSION CELL TECHNIQUE

The kinetics of the extraction of zinc, cobalt and nickel from perchlorate solutions using di 2-ethyl-hexyl phosphoric acid (D2EHPA) dissolved in heptane were studied using the Rotating Diffusion Cell technique. The extraction of each metal was investigated individually over a wide range of metal concentration, extractant concentration, pH and temperature conditions.

The data were analysed in terms of a mass transfer with chemical reaction (MTWCR) mechanism. Hughes and Rod'/s generalized MTWCR model was used to fit the cobalt data using kinetic and equilibrium parameters. The zinc and nickel data were quantitatively described within the framework of the MTWCR model. The zinc extraction rate was so fast that mass transfer alone was rate controlling. The nickel extraction experiments were so slow that the metal-ligand complex formation was incomplete in the aqueous film. Some reaction was determined to be occurring in the aqueous bulk solution as well.     

THE KINETICS OF ACETIC ACID EXTRACTION STUDIED WITH THE ROTATING STABILIZED CELL TECHNIQUE.APPLICATION OF THE BARRIER MODEL.

ABSTRACT

The kinetics of acetic acid extraction is studied with the use of an improved version of the rotating stabilized cell (RSG) technique at interfaces between an aqueous solution and an organic phase. The RSC is implemented as follows: the aqueous phase, containing the species of interest, is immobilized in a gel, placed in a rotating cylinder immersed in the organic phase. The transport processes in both phases are reliably controlled: pure diffusion in the gel, and rotating disc flow in the organic fluid. The amount of matter extracted from the gel is measured as a function of time; the data are analyzed at times much shorter than the mean diffusion time in the gel, in a transient regime. First, the reliability of the method is studied by examining the dependence of the aqueous-towards-organic rate constant upon the rotation speed; a critical value is found which corresponds to the maximum speed for a laminar flow. Then, the method is applied to the study of the kinetics of acetic acid extraction by several organic solvents. Lastly the modelling of the interfacial transfer as a barrier-crossing process is examined. Possible breakdown of the transition-state theory (TST) for the determination of activation free energies is discussed. The latter may be significantly lower than the classic TST result.     

SOLVENT EXTRACTION OF COBALT(II) WITH TRI-n-BUTYL PHOSPHATE FROM AQUEOUS-ORGANIC SOLUTIONS

Cobalt(II) has been extracted by 50% (v/v) TBP solution in benzene from HC1, HBr, and LiC1 solutions containing water miscible alcohols and nonbesic and basic aprotic solvents. All solvents used caused the distribution ratio of Co(II) to increase due to diminished water activity and shifts in equilibria of cobalt(II) complexes in solutions. Hexamethylphosphor-triamide (HMPTA) has been found to behave exceptionally in that it extracted Co(II) from LiC1 solutions into neat benzene and in the presence of TBP induced a weak synergism caused by extraction of at least two mixed solvates.     

正辛醇为稀释剂条件下二元羧酸的萃取平衡特性

以二元羧酸乙二酸、丙二酸、丁二酸、顺丁烯二酸和苹果酸为分离对象,三烷基氧膦（TRPO）为络合剂,正辛醇为稀释剂进行了系统的萃取相平衡实验.结果表明,溶质的pK_a1和羧酸的亲油性同时影响络合萃取平衡.红外光谱分析表明,萃取剂TRPO与正辛醇之间形成氢键,抑制了对羧酸的萃取,使得TRPO与有机羧酸之间形成1∶1的络合物;负载有机羧酸的红外谱图表明,TRPO萃取有机羧酸为氢键溶剂化历程,负载有机羧酸的TRPO中的P=O键吸收峰的位移与有机羧酸的酸性有关.采用质量作用定律分析方法建立了负载量的表达式,模型拟合精度令人满意.     

THE KINETICS OF H2S DECOMPOSITION OVER PRECIPITATED COBALT SULPHIDE CATALYST

Cobalt sulphide catalyst prepared via a new method involving the precipitation reaction between cobaltous acetate and ammonium sulphide solutions has been shown to be favourably active for the catalytic decomposition of H₂S when compared with data for other transition metal sulphides.

The BET surface area of this unsupported catalyst is about an order of magnitude higher than cobalt sulphide formed by direct sulphidation of cobalt oxide with H₂S gas. XRD, SEM and TEM analyses were used to obtain bulk composition and morphological characteristics. Catalyst specimen calcined at 823 K showed the best activity.

The kinetics of the decomposition reaction has been studied over this new preparation. Experiments conducted at atmospheric pressure between 933-983 K using about 11 feed compositions showed that below 40% H₂S/Ar the reaction was essentially 1st order with respect to H₂S partial pressure. Beyond this point, rate remained invariant with feed composition. A mechanism involving catalysis via co-ordinative unsaturation sites on the CoS was proposed and kinetic model based on the cleavage of the surface H-S bond as the rate-determining step appeared to be the most adequate representation of the rate data. Hydrogen production rates at all temperatures also paralleled the behaviour seen for H₂S decomposition. Activation energy for H₂S decomposition and H₂ production rates were estimated as 111 kJ mol^-1 and 88 kJ mol^-1 respectively     

EXTRACTION OF COPPER SALTS WITH A MIXED EXTRACTANT (III): AGGREGATION AND MOLECULAR STRUCTURE

A study of the extraction of copper salts from aqueous solutions into an equimolar solution of a long-chain amine and a long-chain carboxylic acid in toluene has shown that a cationic copper aggregate is formed in the organic phase. A mechanism of the extraction process and a model structure of the aggregate are proposed based on UV-visible, and NMR spectra, water solubilization, and computer-aided model design (CAMD).     

MODELING ANALYTICAL TESTS OF SUPERCRITICAL FLUID EXTRACTION FROM SOLIDS WITH LANGMUIR KINETICS

A model for the analytical supercritical fluid extraction (SFE) tests from solid samples in which desorption of the solute from the surface of the solid is the rate determining step is presented. The desorption process is described by the Langmuir kinetics. The two stages of the test (static and dynamic) are modeled, where each of the two phases (solid and supercritical fluid) are considered well mixed. The resulting ordinary differential equations are solved analytically for the static stage and numerically for the dynamic stage. Dimensionless curves of concentrations of the two phases and fractional recovery during the two stages of the tests are predicted. These curves are characterized by two dimensionless parameters for the static stage, the equilibrium constant and the fractional initial capacity, in addition to one parameter for the dynamic stage, the desorption coefficient. The model provides a good fit to experimental results for SFE from solids. The trends in the fitted parameters with respect to pressure and temperature are in agreement with theory.     

INFLUENCE OF SALTING-OUT EFFECTS,TEMPERATURE AND THE CHEMICAL STRUCTURE OF THE EXTRACTANT ON THE RATE OF COPPER(II) EXTRACTION FROM CHLORIDE MEDIA WITH DIALKYL PYRIDINE DICARBOXYLATES

ABSTRACT

The kinetics of copper(II) extraction from chloride solutions with ACORGA CLX-50 and three model dipentyl pyridine dicarboxylates having ester groups at various positions in the pyridine ring is investigated. It is shown that the extraction occurs in a diffusional regime and that both the ionic strength and temperature have a strong effect on the rate of copper extraction. Basically, the initial rate of copper extraction (denoted hereafter J₀) increases as the ionic strength is increased, whereas J₀ increases or decreases versus temperature depending on the ionic strength. Such phenomena are explained in terms of salting-out effects and diffusion properties. Furthermore, ACORGA CLX-50 is shown to exhibit a good kinetic performance compared to the three model dipentyl pyridine dicarboxylates.     

THE EXTRACTION OF SOME BASE METAL IONS BY CYANEX 30L CYANEX 302 AND THEIR BINARY EXTRACTANT MIXTURES WITH ALIQUAT 336

ABSTRACT

The extraction behaviour of Cyanex 301, Cyanex 302 and their binary extractant mixtures with Aliquat 33b towards copper(II), zinc(II), iron(III), iron(II), cobalt(II), nickel(II) and manganese(Il) is indicated. The extraction data were collected from sulphate solutions with acidities ranging from pH 10 to 8 mol/dm³ sulphuric acid. Cyanex 301 is a more efficient extractant than Cyanex 302 and is able to effect extraction at greater acidities. In combination with the organic base Aliquat 336 the extraction power of these extractants is lowered and in some cases the extraction is suppressed appreciably. However, the suppression of extraction can be useful in metal separation and affords greater control over the back-extraction. The suppression is ascribed to the high stability of the acid-base couple which must dissociate in order to effect extraction.     

EXTRACTION OF COPPER SALTS WITH A MIXED EXTRACTANT (II): WATER UPTAKE AND OSMOMETRIC MEASUREMENTS

A mixture, consisting of trioctylamine and 2-ethyl hexanoic acid dissolved in toluene, extracts metal salts as well as water from aqueous salt solutions. Water uptake measurements showed a linear increase with salt concentration. IR spectra revealed -OH vibrations of both “free” and “associated” hydroxyl, which differ from those of bulk water. Data treatment of water uptake in accordance with Hogfeldt's model indicated the formation of mixed reversed micelles consisting of metal-salt-loaded mixed extractant and free extractant molecules. Micellization was also confirmed by osmometric measurements.     

THE USE OF THE ROTATING DIFFUSION CELL TECHNIQUE FOR THE STUDY OF SOLVENT EXTRACTION KINETICS

The application of the Rotating Diffusion Cell (RDC) to the study of solvent extraction kinetics has been described. In the RDC the two phases are brought into contact at the surface of a membrane filter. The filter la rotated on a cylinder, establishing well defined rotating disk hydrodynamics on either side of the filter surface- It is therefore possible to characterize precisely the diffusional processes of the reactant and product species on the aqueous and organic sides of the interface. The area of interfacial contact may be varied without affecting the diffusional processes. It is the characterization of the diffusional processes and the ability to vary the area of interfacial contact which makes this technique very useful in solvent extraction kinetic studies. A few experiments from the cobalt-HEHEHP system have been described to illustrate the use of the RDC.     

钴镍协同萃取体系

评述了自１９６６年以来报道的有关钴镍协同萃取的文献．主要介绍了磷酸、羧酸以及磺酸类萃取剂与含氮螯合萃取剂或非螯合萃取剂组成的协同萃取体系．此外，对一些由胺类萃取剂加磺酸或羧酸类萃取剂加吡啶羧酸酯组成的协同萃取也作了简单介绍．讨论了这些协同萃取体系萃取钴镍的反应机理、特点及其潜在的应用价值．     

石灰石与SO2反应动力学的研究

石灰石与ＳＯ２的高温短时的硫酸化反在夹带流反应器中被实验研究，硫酸化反应是一个两阶段反应：初始是一个非常快的零级表面反应且活化能的２１．０ｋＪ／ｍｏｌ，接着是活化能为８０．１ｋＪ／ｍｏｌ的产物层扩散控制反应，初始阶段约０．３ｓ．吸收剂的种类、Ｃａ／Ｓ比、停留时间、反应温度和ＳＯ２分压影响着脱硫反应速率，脱硫反应过程能用缩芯模型来模拟。在Ｃａ／Ｓ＝２、１０００℃Ｔ ２Ｓ的实验条件下，喷射Ｆ－石灰石能     

ANAEROBIC EXTRACTION OF COBALT IN A PULSE COLUMN

The effects of excluding air (oxygen) from a cobalt solvent extraction circuit were studied for LIX 64N extractant. After solvent extraction of divalent cobalt from ammoniacal solutions with chelating extractants such as LIX 64N, the loaded Co-chelate is believed to oxidize to a stable trivalent complex which resists subsequent stripping with mineral acids. To Improve stripping efficiency, cobalt was extracted and stripped in the absence of oxygen in pulsed, perforated-plate columns that were designed and constructed by the Bureau of Mines. When the ammoniacal cobalt(II) sulfate and LIX 64N solutions were purged, blanketed, and pulsed with argon, cobalt extraction exceeded 99%, and stripping with 1 vol % H₂SO₂ reached 98.5%. The stripped extractant was recycled to the extraction column with no loss of extraction efficiency in six passes through the circuit.