Extraction Rate Equation Research Articles

Extraction kinetics of separating molybdenum(Ⅵ) over iron(Ⅲ) from high acid leach solutions with mixtures of P507 and N235

In view of the difficulty of separating molybdenumVI over ironIII from high acid leach solutions, the extraction kinetics of separating molybdenumVI/ironIII with mixtures of 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (P507) and long chain tertiary amine (N235) was investigated using a Lewis cell to enhance the separation efficiency. Parameters affecting the extraction process such as stirring speed, specific interfacial area, and temperature were studied. The results show that the extraction process of MoVI takes place in the bulk aqueous phase, and the extraction rate is controlled by diffusion (The apparent activation energy was calculated to be 16.66 kJ/mol). The rate constants (kf) of mean MoVI extraction was calculated as 100.3, and the extraction rate equation was established: - d[Mo]/dt = 100.3[Mo](a)[P507](o)0.35[N235](o)0.24. The extraction reaction of MoVI had a fast rate in the studied range of solution conditions, but FeIII was not extracted. Moreover, the separation mechanism was speculated by two-phase titration, Fourier transform infrared spectroscopy and Nuclearmagneticresonancespectroscopy.

The kinetics and thermodynamics investigation of lithium extraction from brine by TBP using Lewis cell technique

The extraction kinetics of lithium from brine by tri-n-butyl phosphate had been researched experimentally using Lewis cell technique. Different parameters such as interfacial area, temperature, agitation speed, the concentration of Li+, Fe3+ and TBP were studied separately to identify the reaction location and the extraction reaction regime. The experimental results demonstrated the control mode of the extraction reaction was a mixed control mode which occurred at the interfacial area. Further analysis suggested the extraction rate equation can be expressed as follows: R=3.145×10-3[Li+][FeCl4-][TBP]2The results of thermodynamic functions suggested the extraction reaction was an entropy increase process and extraction reaction was spontaneous.

Kinetics and the difference for extraction of praseodymium and neodymium from nitrate aqueous solution by [A336][NO3] using the single drop technique

The kinetics and the difference for Pr(III) and Nd(III) extraction from nitrate aqueous solution using trialkylmethylammonium nitrate ([A336][NO 3 ]) as extractant were investigated by the single drop technique. The dependence of the extraction rate of Pr(III) and Nd(III) on the concentrations of free Pr(III) and Nd(III) ions, the concentrations of NaNO 3 and H + in aqueous solutions, and the concentrations of [A336][NO 3 ] in kerosene solutions were discussed and the corresponding extraction rate equations for Pr(III) and Nd(III) were obtained. These equations demonstrated that the reaction rate constant of Pr(III) with [A336][NO 3 ] was double than that of Nd(III). The effect of the addition of diethylenetriaminepentaacetic acid (DTPA) on the difference in the extraction rate of Pr(III) and Nd(III) by [A336][NO 3 ] was also investigated. It was revealed that the difference in the complex formation rates of Pr(III) and Nd(III) with DTPA made a significant impact on the difference in the extraction rates of Pr(III) and Nd(III) with [A336][NO 3 ]. The ratio of extraction rates of Pr(III) to Nd(III) with [A336][NO 3 ] was in proportion to the ratio of complex formation rates of Pr(III) to Nd(III) with DTPA. The extraction rate difference for Pr(III) and Nd(III) with [A336][NO 3 ] increased due to a higher complex formation rate constant of DTPA with the free and un-complexed Nd(III) ions in the aqueous nitrate solution than that with Pr(III) ions. Therefore, the addition of DTPA in the aqueous nitrate solution is an effective method to intensify the separation of Pr(III) and Nd(III) in kinetics. The study on the extraction mechanism indicated that both the extraction of Pr(III) and Nd(III) by [A336][NO 3 ] were diffusion controlled, and the reactions obeyed S N 2 mechanism. The present work highlights a possible approach to strengthen the kinetic separation of Pr(III) and Nd(III). • The rate equations of Pr(III) and Nd(III) extracted by [A336][NO 3 ] are obtained. • Difference in the extraction rate of Pr(III) and Nd(III) increased due to the addition of DTPA. • Difference in the complexing rate of DTPA with Pr(III) and Nd(III) play a crucial role to intensify kinetic separation. • Extraction of Pr(III) and Nd(III) by [A336][NO 3 ] obeys S N 2 mechanism.

Extraction kinetics and mechanism of Zr and Hf by DIBK−TOPO system using Lewis Cell

ABSTRACTKinetics studies on the extraction of Zr and Hf using the mixture of diisobutyl ketone (DIBK) and trioctylphosphine oxide (TOPO) as extractant were performed in a Lewis Cell. The results showed that the extraction rate of Zr was governed by chemical reaction in the bulk phase. The extraction rate of Hf was controlled by chemical reaction and mass diffusion at the interface. It testified that the overall extraction reaction was an exothermic and non-spontaneous process, which occurred via an SN2 mechanism. Under the given conditions, the overall extraction rate equation and rate-limiting chemical reaction step of Zr and Hf were proposed.

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) was investigated using a constant interfacial cell with laminar flow. The effects of stirring speed, temperature and specific interfacial area on the extraction rate were examined. The results indicate that mass transfer kinetics of La(III) is a mixed-controlled process influenced by interfacial reaction. On the basis of mass transfer kinetic results in the extraction of La(III) by [A336][CA-12], the extraction rate equation of La(III) is proposed in terms of pseudo-first-order constants, which is supported by the measured thermodynamic equations. The mass-transfer kinetic model deduced from the rate controlling step is adequate to interpret the experimental data qualitatively.

Kinetics and mechanism of Am(III) extraction with TODGA

In the present paper, N,N,N’,N’-tetraoctyl diglycolamide (TODGA) as the extractant and n-dodecane as the diluent, the extraction kinetics behavior of Am(III) in TODGA/n-dodecane–HNO3 system were studied, including stirring speed, the interfacial area, extractant concentration in n-dodecane, extracted ions concentration, acidity of aqueous phase and temperature. The results show that: the extraction process is controlled by diffusion mode under 130 rpm of stirring speed and by chemical reaction mode above 150 rpm. The extraction rate equation and the apparent extraction rate constant of Am(III) by TODGA/n-dodecane in 170 rpm and at 25 °C are followed as: $$ \begin{aligned} r_{0} = \left. {\frac{{{\text{d}}[{\text{M}}]_{{{\text{org}} .}} }}{{{\text{d}}{{t}}}}} \right|_{t = 0} & = k\,\frac{S}{V}\left[ {\text{Am}} \right]_{{{\text{aq}} . ,0}}^{0.94} \left[ {{\text{HNO}}_{3} } \right]_{{{\text{aq}} . ,0}}^{1.05} \left[ {\text{TODGA}} \right]_{{{\text{org}} . ,0}}^{1.19} \\ & \quad k = \left( {24.17 \pm 3.43} \right) \times 10^{ - 3} \,{\text{mol}}^{ - 2.18} \,L^{2.18} \,{ \hbox{min} }^{ - 1} \,{\text{cm}},\;E_{\text{a}} \left( {{\text{Am}}\left( {\text{III}} \right)} \right) = 25.94 \pm 0.98\;{\text{kJ/mol}} .\\ \end{aligned} $$

Kinetics of cobalt(II) extraction from sulfate aqueous solution by sodium salt of di-decylphosphinic acid (DDPA)

Kinetics of Co(II) extraction from sulfate aqueous solution by the sodium salt of di-decylphosphinic acid (Na-DDPA) was studied using a modified Lewis cell to disclose the mechanism of extraction. Parameters affecting the extraction rate, such as stirring speed, temperature, interfacial area, Na-DDPA concentration and Co(II) concentration, were investigated, respectively. The effect of diffusion resistance on extraction rate was negligible when the stirring operation was conducted in a plateau region of 95-110 r/min. Extraction rate increased with the increase in the temperature or specific interfacial area. The activation energy E was calculated to be 32.75 kJ/mol. These suggested that rate controlling mechanism of Co(II) extraction by Na-DDPA was chemical reaction regime and the rate-determining step of Co(II) extraction was chemical reaction at the interface. The initial extraction rate also increased with the increase in the concentrations of Na-DDPA and Co(II). The extraction rate equation and mechanism of Co(II) extraction by Na-DDPA were proposed.

Extraction Kinetics of Cerium(III) from Chloride Medium by Di-(2-Ethylhexyl)phosphoric Acid in the Presence of Acetic Acid Using a Constant Interfacial Area Cell with Laminar flow

The Ce(III) extraction kinetics with di-(2-ethylhexyl)phosphoric acid (D2EHPA) in the presence of a complexing agent acetic acid(HAc) has been investigated using constant interfacial cell with laminar flow. The kinetics mechanism and extraction rate equation were achieved by the studies on the effect of stirring rate, temperature and specific interfacial area on the rate of extraction. The effect of temperature on the kinetics was analyzed, the value of the apparent activation energy was calculated as 11.96 kJ/mol, and it was found that the extraction process was a diffusion-controlled kinetics regime.

Study on Mass-Transfer Kinetics of Nd by 2-Ethylhexylphosphonic Acid Mono-(2-Ehylhexyl) Ester in the Presence of a Complexing Agent

The Nd(III) extraction kinetics by 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) ester (HEH/EHP) in the presence of a complexing agent acetic acid(HAc) has been investigated using constant interfacial cell. The kinetics mechanism and extraction rate equation were achieved by the studies on the effect of stirring rate, temperature and specific interfacial area on the rate of extraction. The effect of temperature on the kinetics was analyzed, the value of the apparent activation energy was calculated as 9.24 kJ/mol, and it was found that the extraction process was a diffusion-controlled kinetics process.

Kinetics and Mechanism of Mo(VI) Extraction with Trialkyl Amine Using a Constant Interfacial Cell with Laminar Flow

The extraction kinetics of molybdenum(VI) with trialkyl amine (N235, R3N, R = C8–C10) dissolved in heptane has been investigated by constant interfacial cell with laminar flow. The stiochiometry and the equilibrium constant of the extracted complex formation reaction between Mo(VI) and N235 are determined. The influences of stirring speed, temperature, concentrations of extractant and chlorine on the extraction rate has been studied. It can be concluded that the mass transfer process is a mixed chemical reaction - diffusion controlled. The extraction rate equations and the rate-determining step have been obtained under the experimental conditions by predictions derived from interfacial reaction models. Based on the approximate solutions of the flux equation, diffusion parameters and thickness of the diffusion film have been calculated.

Kinetics and mechanism of Re(VII) extraction and separation from Mo(VI) with trialkyl amine

The extraction kinetics of rhenium(VII) or molybdenum(VI) with trialkyl amine (N235, R 3N, R=C 8–C 10) dissolved in heptane were investigated by constant interfacial cell with laminar flow, which aimed to identify the extraction regime, reaction zone and rate equations. The influence of stirring speed, temperature, specific interfacial area, extraction concentration and chlorine concentration on the extraction of both metals was studied. It is concluded that the extractions of Re(VII) and Mo(VI) both take place at the liquid–liquid interface, while the extraction regimes are chemically-controlled for rhenium and mixed controlled for molybdenum, respectively. The extraction rate equations and the rate-determining step were obtained under the experimental conditions, and the extraction rate constant of Re(VII) or Mo(VI) with N235 was calculated. These obtained kinetics parameters are different between Re(VII) and Mo(VI), which provides better possibilities for Re(VII) and Mo(VI) separations at proper conditions.

Kinetics and mechanism of Re(VII) extraction with mixtures of tri-alkylamine and tri-n-butylphosphate

The extraction kinetics of rhenium(VII) with mixtures of tri-alkylamine (N235, R 3N, R = C 8 − C 10) and tri-n-butylphosphate (TBP) dissolved in heptane has been investigated by constant interfacial cell with laminar flow. The influence of stirring speed, temperature, specific interfacial area, extractant concentration and chloride concentration on the extraction rate has been studied. It is concluded that the extraction of Re(VII) takes place at the liquid–liquid interface, while the extraction regime belongs to kinetic control by chemical reaction. The extraction rate equations and the rate-determining step have been obtained under the experimental conditions, and the extraction rate constant is calculated. The results are also compared with the system with N235 alone as extractant which shows that the Re(VII) extraction rate is enhanced and the activation energy is decreased with the mixtures of N235 and TBP. The separation of Re(VII) from Mo(VI) by kinetics with the mixtures of N235 and TBP is similar to that with N235 alone. Nevertheless, the separation of Re (VII) from Mo(VI) is better under kinetic conditions than under thermodynamic equilibrium conditions.

Analysis of continuous solvent extraction of nickel from spent electroless nickel plating baths by a mixer-settler

It is urgent to develop an effective technique to treat the large amount of spent electroless nickel plating bath and recycle the high concentration nickel. In our previous study, high recycling efficiency of nickel from the model spent bath was obtained by continuous solvent extraction with 2-hydroxy-5-nonylacetophenone oxime (LIX84I) as the extractant and 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (PC88A) as the accelerator using a mixer-settler extractor. It was observed that the extraction efficiency was affected by the operation parameters such as the flow rates of the aqueous and organic phases and the total stage number. In the present study, the effects of the operation parameters on the extraction efficiency were quantitatively studied on the basis of the pseudo-first-order interfacial extraction rate equation together with the hydrodynamic properties in the mixer. The organic phase holdup, measured under varying conditions of the flow rates of both phases, was analyzed by the Takahashi-Takeuchi holdup model in order to estimate the specific interfacial area. The overall extraction rate coefficients defined by the product of the interfacial extraction rate constant and the specific interfacial area were evaluated using the experimental data and ranged from 3.5 × 10 −3 to 6.7 × 10 −3 s −1, which was close to the value of 3.4 × 10 −3 s −1 obtained by batch extraction. Finally, an engineering simulation method was established for assessing the extraction efficiency of nickel during a multistage operation.

Kinetic study of ytterbium(III) extraction from sulfate medium with Cyanex 923

AbstractThe kinetics of ytterbium(III) extraction from sulfate medium with Cyanex 923 in heptane has been investigated with a constant interfacial cell with laminar flow, which aimed to identify the extraction regime, reaction zone and rate equations. It was found that the extraction rate of ytterbium(III) increased linearly with stirring speed and specific interfacial area. The activation energy Ea (9.56 kJ mol−1), activation enthalpy ΔH± (7.05 kJ mol−1), activation entropy ΔS±298 (−0.31 kJ mol−1) and Gibbs free energy of activation ΔG±298 (98.3 kJ mol−1) were calculated from the dependence of extraction rate on temperature. The experiential rate equations were obtained by investigating the influence of the concentration of various species on the extraction rate. A diffusion regime has been deduced from evidence of the linear dependence of extraction rate on stirring speed and the low value of the activation energy. The liquid–liquid interface is most probably the reaction zone in view of the linear dependence of extraction rate on specific interfacial area, the high interfacial activity and low water‐solubility of extractant. Thus the mass transfer rate is controlled by interfacial film diffusion of species. Copyright © 2007 Society of Chemical Industry

Kinetics and Mechanism of Yb(III) Extraction and Separation from Y(III) with Mixtures of bis(2,4,4‐trimethylpentyl)phosphinic acid and2‐ethylhexyl phosphonic acid mono‐2‐ethylhexyl ester

The ytterbium(III) extraction kinetics and mechanism with mixtures of bis(2,4,4‐trimethylpentyl)phosphinic acid (Cyanex272) and 2‐ethylhexyl phosphonic acid mono‐2‐ethylhexyl ester (P507) dissolved in heptane have been investigated by constant interfacial cell with laminar flow. The effects of the stirring rate, temperature, extractant concentration, and pH on the extraction with mixtures of Cyanex272 and P507 have been studied. The results are compared with those of the system with Cyanex272 or P507 alone. It is concluded that the Yb(III) extraction rate is enhanced with mixtures extractant of Cyanex272 and P507 according to their values of the extraction rate constant, which is due to decreasing the activation energy of the mixtures. Atthe same time, the mixtures exhibits no synergistic effects for Y(III), which provides better possibilities for Yb(III) and Y(III) separations at a proper conditions than anyone alone. Moreover, thermodynamic extraction separation Yb(III) and Y(III) by the mixtures has been discussed, which agrees with kinetics results. Extraction rate equations have also been obtained, and through the approximate solutions of the flux equation, diffusion parameters and thickness of the diffusion film have been calculated.

Rate Equation of Antisynergic Extraction of Cadmium with D2EHDTPA-TOA

The kinetics of antisynergic extraction of cadmium with D2EHDTPA (di-(2-ethylhexyl)-dithiophosphoric acid)-TOA(trioctylamine) under the condition of interfacial reaction controlling model was investigated by using an improved constant interfacial area stirred cell. The extraction course was composed of several interphase transfer processes (transfer between bulk phase and interfacial phase (or boundary phase)) and several chemical reactions. The extraction rate equation was: r = 1.42 x 10(-7)[Cd2+](0.42)[BHA](O)(0.47)/[B](O)(0.85)[H+](0.21) (mol . m(-2) . s(-1)) The interfacial concentration was associated with the bulk concentration by using Freundlich adsorption equation. The concentration exponents in the extraction rate equation were decided by the two factors of the interfacial chemical reactions and the interphase transfer processes. The physical meaning of the fractional reaction order in the rate equation was analyzed. The bigger the Freundlich power n of a reactant, the more the repulsion exerted by the interfacial layer. The apparent extraction activation energy E = 44.2 kJ . mol(-1), the extraction enthalpy DeltaH = 72.9 kJ . mol(-1). The inconsistency in extraction mechanism due to different interface models was also discussed.

2-Ethylhexanal OximeによるNi<sup>2+</sup>の抽出速度におよぼす添加剤の効果

In the previous work, it was found that the extraction rate of Ni2+ with 2-ethylhexanal oxime (abbreviated as EHO) from wasted FeCl3 etching solution was extremely slow. This is because the substitution reaction of the hydrated Ni2+ ions, Ni(H2O)62+ with the extractant is a rate determining step.In order to improve the extraction rate of Ni2+, the extraction rate was investigated by adding D2EHPA or TBP as a second extractant to the main extractant EHO. The big enhancement of Ni2+ extraction rate is found when the second extractants, D2EHPA or TBP, are added in a small amount to EHO. As an example, the addition of 0.1mol/dm3 D2EHPA and TBP results in 18 and 30 times enhancement of Ni2+ extraction. The extraction rate equation for Ni2+ is induced so as to be a reversible reaction. Then, the apparent rate constants for forward and backward reactions were calculated according to the induced rate equation. The forward extraction rate is proportional to the 1st order of Ni2+ concentration, TBP concentration and EHO concentration, while the backward extraction rate is proportional to the 1st order of Ni2+ concentration, which is written as,-d[Ni2+] / dt = kf*[Ni2+]aq [EHO]org [TBP]org -kb*[Ni2+]aqThe above extraction rate expression is reasonably explained by imaging the following elementary reactions and assuming the second reaction to be a rate determining step,Ni(H2O)62+ + TBPad ⇔ Ni(H2O)52+ · TBPadNi(H2O)52+ · TBPad + EHOad → Ni(H2O)52+ · EHOad + TBPad

Extraction kinetics of lanthanum with purified Cyanex 923 from nitrate medium

Solvent extraction kinetics of lanthanum with purified Cyanex 923 in heptane from nitrate medium was investigated by using a constant interfacial cell with laminar flow at 303 K. The effects of stirring speed, temperature and specific interface on the extraction rate were studied. The experimental results showed that the extraction apparent activation energy was 32.0 kJ · mol−1 and the extraction process was controlled by both chemical reaction and diffusion. The extraction rates were measured at different chemical compositions by varying ionic strength, pH value and the concentration of purified Cyanex 923. The initial extraction rate equation was obtained.

The methematical modeling of the removal of phenol with emulsified liquid membranes

In this paper, a modified advancing reaction front model, which includes the resistances for mass transfer in the water boundary layer, the oil film and the emulsion, is presented. The model was solved by numerical method with computer. The agreements between the modelic predications and the experimental results are quite good. In addition, the effective diffusivity of phenol in emulsion has been thoroughly discussed. A method of measuring D eff is established and a formula of calculating D eff based on D m, D i and φ is also given. Furthermore, a simplified mass transfer model, the flat model, is also put forward and based on this model, an approximate extraction rate equation is given.

Extraction rate equations for paprika and turmeric with certain organic solvents

Extraction rate equations for paprika and turmeric with certain organic solvents