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.     

EXTRACTION OF NICKEL FROM AQUEOUS SULFATE SOLUTION INTO BIS(2,2,4-TRIMETHYLPENTYL)PHOSPHINIC ACID,CYANEX 272TM -EQUILIBRIUM AND KINETIC STUDIES

ABSTRACT

Equilibrium and kinetic studies have been carried out on the extraction of nickel from sulfate solutions using bis(2,2,4 trimethylpentyl) phosphinic acid HDTMPP, “Cyanex 272tm”- It was found that nickel extraction in HDTMPP was favored by the presence of sodium in the organic phase and that equilibrium nickel concentration could be written in terms of the pre-equilibrated extractant concentration

Kinetic studies were carried out using the rising drop method, reaction orders were determined with respect to the aqueous phase nickel concentration, Ni²⁺, the aqueous phase sodium concentration, Na ⁺ the pH, the organic phase dimer concentration ------ and the organic phase sodium salt concentration ---- In addition, it was found that the extraction kinetics could be explained in terms of an aqueous phase interfacial reaction accompanied by diffusion through the interface. Mass transfer coefficient values were determined indicating extraction rates for metal extraction into HDTMPP were the same order of magnitude as those found for HDEHP.     

Extraction Kinetics of Rare Earth Metals with 2-Ethylhexyl Phosphonic Acid Mono-2-ethylhexyl Ester Using a Hollow Fiber Membrane Extractor

Abstract

A kinetic study concerning chemical complexation-based solvent extraction of rare earth metals with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester dissolved as an extractant in n-heptane was carried out using a microporous hydrophobic hollow fiber membrane extractor. The effects of concentration of chemical species in aqueous and organic feed solutions on the apparent permeabilities of metal species for extraction and stripping, respectively, were investigated to clarify the permeation mechanism. From the experimental results it was predicted that the permeation rate is controlled by diffusion of the chemical species in aqueous and organic phases and by interfacial chemical reaction. The experimental data were analyzed by the diffusion model accompanied with an interfacial reaction, taking into account the velocity distributions of the aqueous and organic phases through the inner and outer sides of the hollow fiber.     

5709萃取钴的宏观动力学研究

采用改进的恒界面池进行了异已基膦酸(1-甲基-庚基)酯(国内代号5709)-庚烷体系从硫酸介质中萃取钴(Ⅱ)的动力学研究.以组分活度代替浓度处理实验数据对有关参数进行了关联,并建立了相应的数学模型(?)=1.435×10~(-3)(a_c_o)-b[(a_(HA)_2)_b]~(1/2)·N~(1/2)/2.55×10~3(a_(H)_b·N~(1/2)+[(a_(HA)_2)_b]~(1/2)实验结果表明,5709萃取钴(Ⅱ)动力学的过程控制为混合控制机制,即为水相中钴离子的扩散和相界面钴的1—2络合物生成的化学反应为主要控制步骤.在水相pH值较高时,控制步骤以前者为主导;在水相pH值较低时,则以后者为主要控制步骤.     

Studies on the Separation and Recovery of Thorium from Nitric Acid Medium using (2-ethyl hexyl) Phosphonic Acid,Mono (2-ethyl hexyl) Ester (PC88A)/N-Dodecane as Extractant System

This paper deals with the studies on the separation and recovery of thorium and 233-uranium from nitric acid medium using (2-ethyl hexyl) phosphonic acid, mono (2-ethyl hexyl) ester/n-dodecane as an extractant system. The different extraction parameters were investigated. The distribution ratio of thorium decreased with increase in nitric acid concentration. The optimum solvent concentration for quantitative separation of thorium from aqueous feed solution was 0.75 M of PC88A whereas dodecane was the most suitable of diluents with an organic to aqueous phase ratio of 1:1. Among the various strippants used, 2 M solution of (NH₄)₂CO₃ was found to be the most suitable for back extraction of thorium. The developed method was used to recover thorium and ²³³U from radioanalytical waste generated during thorium analysis by ethylene diamine tetraacetic acid (EDTA) titremtric method and recoveries for both Th and U were more than 85%.     

Separation of Cobalt and Nickel with Phenylphosphonic Acid Mono-4-tert-octylphenyl Ester by Liquid Surfactant Membranes

Abstract

The separation of cobalt and nickel with liquid surfactant membranes (LSMs) was carried out in a stirred cell using a newly synthesized extractant. The effect of a surfactant on the kinetics of cobalt and nickel extraction was investigated to elucidate the role of a surfactant used in LSMs. The extraction equilibrium of these metals was also examined. Further, the interfacial tension between the organic and aqueous phases was measured to elucidate the adsorption equilibrium of a surfactant. It was found that the interfacial activity of the extractant is as high as that of a surfactant. In the extraction equilibrium study of these metals, extraction equilibrium constants were obtained for cobalt and nickel for the following equations:

Co²⁺ + 2(HR)₂=CoR₂(HR)₂ + 2H⁺ Ni²⁺ + 3(HR)₂=NiR₂2(HR)₂ + 2H⁺ The effects of the extractant and surfactant on the extraction rate of cobalt and nickel in LSMs were studied. The results were analyzed by a proposed model with an interfacial reaction, and rate constants were obtained for each metal. It was found that the new extractant has a very strong extractability for each metal compared with a conventional commercial extractant such as 2-ethylhexylphosphonic acid mono-2-elhylhexylester (commercial name, PC-88A) or di(2-ethylhexyl)phosphoric acid (D2EHPA). Further, a surfactant strongly affected the extraction rate and the separation of these metals, and a cationic surfactant was selected.     

5709-庚烷从硫酸介质中萃取钴、镍体系的界面特性——(Ⅱ)钴、镍萃取动力学反应控制步骤的判定

在实验测定5709-庚烷草取钴、镍体系界面张力的基础上建立了相应体系的界面张力等温线模型。探索了由萃取体系界面特性数据判定萃取动力学过程控制机制的途径,即由界面张力等温线计算得到界面超量等温线,然后再与界面化学反应机制进行关联,进而确定反应中对应萃取剂的反应级数。按此论证了5709-庚烷萃取钴、镍的界面化学反应过程为: 其中被萃金属离子的1-2络合物的生成反应为过程控制步骤。     

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…     

Separation of Cobalt and Nickel by Liquid Surfactant Membranes Containing a Synthesized Cationic Surfactant

ABSTRACT

Separation of cobalt(II) and nickel(II) by using a hydroxyoxime extractant has been investigated both in liquid-liquid extraction and in a liquid surfactant membrane(LSM) system. In the liquid-liquid equilibrium extraction studies, hydroxyoximes showed significant extractability for nickel ions, although LIX 84 was found to have exceptional chelating affinity for nickel ions. In the LSM system functionalized by hydroxyoxime, the cobalt ions were efficiently separated from nickel ions as a result of slower permeation of nickel chelates across the emulsion membrane. More complete cobalt recovery was achieved in the LSMs dosed with LIX 860 than when the same carrier was applied to the liquid-liquid extraction system. Furthermore, cobalt permeation rate was enhanced threefold when a quaternary ammonium type of cationic surfactant was used as an emulsifier due to carrier interaction with surfactant at the reaction interface. The permeation mechanism of ions in LSMs was elucidated by an interfacial reaction model which took into account the adsorption of the carrier and surfactant at the reaction interface.     

异辛醇-甲苯萃取盐湖卤水中硼酸的动力学

引言 硼及其化合物在国民经济中用途极为广泛[1],但是我国主要的硼原料之一硼镁矿石却日趋枯竭,于是开发液体硼矿资源--含硼盐湖卤水成为当务之急.近年来杨卉芃等[2]、李文强[3]、杨存道等[4]分别以沉淀法、离子交换法和结晶法对盐湖卤水提硼工艺进行了研究,并取得了一定的成果.     

Simultaneous solvent extraction of cobalt and magnesium in the presence of nickel from sulfate solutions by Ionquest 801

The simultaneous extraction of Co(II) and Mg(II) from nickel sulfate solutions has been carried out using the organophosphonic extractant Ionquest 801 diluted in Exxsol D‐80. Statistical design and analysis of experiments were used in order to determine the main effects and interactions of the solvent extraction parameters, which were the extraction pH at equilibrium, the temperature, the extractant concentration and the organic/aqueous phase ratio. A statistically designed experiment was also carried out to study the stripping of the Ionquest 801 organic phase loaded with cobalt and magnesium by sulfuric acid solution. The number of stages required for both extraction and stripping processes of cobalt and magnesium was evaluated. The results of continuous counter‐current mini‐plant tests demonstrated the simultaneous recovery of cobalt and magnesium from nickel sulfate solution. Copyright © 2005 Society of Chemical Industry     

有机磷(膦)酸萃取钴和镍的动力学行为比较

依据实验结果和文献数据讨论了有机磷酸类萃取剂萃取钴及镍的动力学行为.结果表明,有机磷酸酸性强,溶入水相的速度快,则萃取速度亦快,钴和镍的萃取速度差异由溶剂交换速度决定.     

IDENTIFICATION OF THE RATE LIMITING STEP LOCUS IN THE EXTRACTION OF Ni(II) By DINONyLNAPHTHALENESULPHONIC ACID

Experimental results are presented and discussed that demonstrate the interfacial character of the rate-limiting step (RLS) in the liquid-liquid extraction of Ni(II) by n-hexane solutions of dinonylnaphthalenesulphonic acid (HDNNS) in a non-dispersing stirred reactor. The possibility of a RLS in the bulk aqueous phase was excluded based on the classical criterion of volume-independent transfer rates per unit volume, and a criterion involving dissolution fluxes of the extractant into the aqueous phase. The aqueous diffusion film was excluded as the site to the RLS on the basis of HDNNS partition results. The combination of extractant distribution and dynamic transfer results is shown able to unequivocally identify the site of the RLS for this reactive system.     

Back Extraction of HCl from TOA Dissolved in N-Octanol by Aqueous Ammonia in a Microchannel Device

To recover the extractant in the preparation of KH₂PO₄ using the extraction method, studies for the back extraction of HCl by aqueous ammonia from TOA (trioctylamine) dissolved in n-octanol were conducted. First, the reaction of HCl back extraction from TOA in n-octanol with aqueous ammonia was examined in shaking flasks and the equilibrium of this reaction was validated. The equilibrium constant of the stripping reaction was determined in the temperature range of 297.7-318.2 K and the reaction enthalpy was found to be -17.8 kJ/mol indicating that the stripping reaction was exothermic. Then kinetic experiments were performed in a microchannel device with the elimination of mass transfer limitations, as demonstrated by the experimental results. A kinetic model was established to obtain the forward and backward interfacial reaction rate constants with the help of the obtained equilibrium constant of the stripping reaction. This model described the measured data well and predicted correctly the change of HCl concentration in the oil phase along with the residence time in our experiments. Furthermore, the activation energy for the forward (8.21 kJ/mol) and backward (26.0 kJ/mol) reaction was determined and subsequently the forward and backward interfacial reaction rate constants were determined in the temperature range of 298.7-313.2 K.     

Extraction Kinetics of Lanthanum in Chloride Medium by Bifunctional Ionic Liquid [A336][CA-12] Using a Constant Interfacial Cell with Laminar Flow☆

The extraction kinetics of La(III) from aqueous chloride solutions into n-heptane solutions of bifunctional ionic liquid extractant [A336][CA-12] (tricaprylmethylammonium sec-octylphenoxy acetic acid) ...     

Separation of cobalt and nickel from acidic sulfate solutions using mixtures of di(2‐ethylhexyl)phosphoric acid (DP‐8R) and hydroxyoxime (ACORGA M5640)

DP‐8R and ACORGA M5640 extractants diluted in Exxsol D100 were used to co‐extract cobalt and nickel from aqueous acidic sulfate media. The influences of equilibration time, temperature, equilibrium pH and reagent concentrations on the extraction of both metals have been studied. It was observed that both cobalt and nickel extraction are slightly sensitive to temperature but are pH dependent. Metal extraction equilibria are reached within about 5 min contact time. In addition, cobalt extraction depends on the extractant concentration in the organic phase. For a solution containing 0.5 g dm^?3 each of cobalt and nickel and an initial pH of 4.1, conditions were established for the co‐extraction of both metals and selective stripping (with H₂SO₄) of cobalt and nickel. Using the appropriate reagent concentrations the yield (extraction stage) for both metals exceeded 90%, and stripping of cobalt and nickel was almost quantitative. Copyright © 2004 Society of Chemical Industry     

Interfacial Mass Transfer in Ligand Accelerated Metal Extraction by Liquid Surfactant Membranes

Abstract

Interfacial mass transfer rates were determined for the extraction of Co(II), Ni(II), and Cu(II) by di-(2-ethyl hexyl) phosphoric acid by using a modified Lewis cell. This allowed us to elucidate the effect of ligands on liquid surfactant membrane extraction of heavy metal ions by ligand addition to the external aqueous phase. The effects of different ligands on the kinetics of extraction and the influence of surfactant on interfacial resistance to mass transfer were then examined.     

Metal extraction of a spiked solid with supercritical carbon dioxide

A mixture of D2EPHA (Di-2-Ethyl Hexyl Phosphoric Acid) and n-hexane is used as the extractant solution to extract cobalt ions from a fireproof board in the environment of supercritical carbon dioxide. It is found that the cobalt on the spiked sample can be totally removed in a pilot unit. The influence of the carbon dioxide flow rate, the flow rate of the extractant solution, the ratio of D2EHPA to hexane in the extractant solution, the temperature and the replacement of hexane by methanol are investigated in this study. Upon extraction, the cobalt complex with D2EHPA is precipitated with the extractant solution in a separation tank through depressurization, and the amount of extracted cobalt in the separation tank is sampled and analyzed by ICP-OES. The accumulation of the removed cobalt along the extraction time is plotted as an extraction curve, and a kinetic model is established to predict the extraction. It is found that the kinetic model reasonably fits the experimental data. From the model, it is concluded that the metal extraction depends on reactivity, that the extent of the extraction is determined by the reversible reaction of the ion-exchange between D2EHPA and the cobalt ions and that the adsorption kinetics of the extractant in the environment of supercritical carbon dioxide may play an important role in the initial stage of extraction. The proposed model, which successfully provides an easy and accurate prediction for metal extraction from a porous solid matrix, can help to reveal the extraction mechanism and optimize the operational conditions for future scale-up designs.     

THE KINETICS OF COBALT(II) EXTRACTION WITH EHEHPA IN HEPTANE FROM ACETATE SYSTEM USING AN IMPROVED LEWIS CELL TECHNIQUE†

ABSTRACT

The cobalt(II) extraction kinetics and mechanism with EHEHPA (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) were investigated by an improved constant interfacial area stirred cell. The effects of the buffer species, stirring rate, temperature, specific interfacial area and surfactants on the extraction rate showed that the extraction regime was dependent on the extraction conditions and the most probable reaction zone was at the liquid-liquid interface. This extraction process was reaction controlled at lower concentration of the reactants, while it was mixed chemical reaction-diffusion or diffusion controlled only for higher concentration of the reactants. An interfacial extraction reaction model with diffusion was derived. The kinetics of the extraction process was simulated with this model.