Constant Interfacial Area Cell Research Articles

Kinetics of Cerium(IV) Extraction from H 2SO 4–HF Medium with Cyanex 923

Studies of the extraction kinetics of cerium(IV) from H 2SO 4–HF solutions with Cyanex 923 in n-heptane have been carried out using a constant interfacial area cell with laminar flow. The experimental hydrodynamic conditions were chosen so that the contribution of diffusion to the measured rate of reaction was minimized. The data were analyzed in terms of pseudo-first order constants. The results were compared with those of the system without HF. It was concluded that the addition of HF reduces the activation energy for the forward rate from 46.2 to 36.5 kJ mol −1 while it has an opposite effect on the activation energy for the reverse process(the activation energy increased from 23.3 to 90.8 kJ mol −1). Thus, HF can accelerate the rate of cerium(IV) extraction. At the same time, the extraction rate is controlled by a mixed chemical reaction–diffusion rather than by a chemical reaction alone. A rate equation has also been obtained.

Kinetic Studies on the Esterification of a Substituted Phenylacetic Acid by Phase-Transfer Catalysis

The reaction rates for the esterification of a substituted phenylacetic acid by phase-transfer catalysis were measured using a constant interfacial area cell. Experiments were performed at different concentrations of aqueous-phase reactant, phase-transfer catalyst, NaOH, and organic-phase reactant. It was shown that the stirring significantly affected the reaction rates. An attempt was made to express the reaction rate as a function of the concentrations of reactive species. The effect of temperature on the reaction was also studied, and the activation energies were evaluated. A possible mechanism was proposed and discussed based on a mixed Makosza and modified interfacial mechanisms.

The kinetics study in liquid–liquid systems with constant interfacial area cell with Laminar flow

A novel constant interfacial cell with laminar flow is proposed as an approach to obtain extraction kinetics data in liquid–liquid systems. Applications and theoretical fundamentals of the apparatus have been elaborated. The equation which can express the mass transfer of liquid–liquid system run in the constant interfacial cell with laminar flow is deduced. Simulations from the equations indicate that diffusivity is a suitable factor to represent the characteristics of extraction kinetics rather than the extraction rate in the diffusion controlling step. The dependence of the aqueous phase concentration on time is recommended to determine the extraction regime. The diffusivities of the EuCl 3–HDEHP extraction system obtained by different methods are compared to certify the hydrodynamic theory of the cell. The diffusivities of the ErCl 3–HEH/EHP extraction system are determined, which show that this technique is a convenient method to obtain the diffusivities in the liquid–liquid system and to determine the extraction regime.

Mass transfer of phenol extraction between two phases in a constant interfacial area cell and stirring tank

In this work, a simple model is provided which accounts for any value of distribution coefficient of a solute, to describe the mass transfer for a batch process of extracting the solute between two immiscible fluids. A Lewis cell of constant interfacial area and a stirring tank were employed as the apparatuses for measuring the mass transfer rates of a solute between two immiscible phases. The model, which was based on the two‐film theory to determine the rate of mass transfer of solute across the interface, and the equilibrium concentration of solute at the interface, was derived and used to express the extraction of phenol. Experimental work, in which phenol was extracted from the aqueous phase to the organic phase by trioctylamine sulfate salts (TOA salts) dissolved in trioctylamine (TOA), was conducted to obtain the mass transfer coefficient. The effects of the operating conditions in a constant interfacial area cell and in the stirring tank are both discussed.

Kinetics and mechanism for copper(II) extraction from sulfate solutions with bis(2-ethylhexyl)phosphoric acid

The rate of copper(II) extraction from 500 mol/m 3 (Na,H,Cu)SO, aqueous solution with bis(2-ethylhexyl)phosphoric acid (D2EHPA, HR) dissolved in kerosene were studied at 25 o C, using a constant interfacial area cell. It was found that, under the conditions studied, the extraction rate could be satisfactorily described by the interfacial chemical reaction model accompanied by the complex diffusion in the organic stagnant film, and the stripping rate, mainly by the diffusion process of the complex.

KINETICS OF PHENOL EXTRACTION FROM AQUEOUS PHASE BY SULFURIC ACID SALTS OF TRIOCTYLAMINE

Abstract The kinetics of the extraction of phenol from the aqueous phase by sulfuric acid salts of trioctylamine (TOA salts) in kerosene and the stripping of phenol from the organic phase by sodium hydroxide solution were studied using a constant interfacial area cell. Measurements of the extraction and stripping rates were made by measuring the time-dependent phenol concentrations in the aqueous phase. It is found that the extraction rate of phenol is strongly dependent on the initial concentration of phenol in the aqueous phase and on the initial concentration of TOA salts in the organic solvent. However, the effect of the total sulfate concentration and the acidic concentration on the extraction rate are not significant. The stripping rate is only a function of the initial concentration of phenol in the TOA salt-organic phase. By analyzing the experimental data, it was recognized that the extraction of phenol occurs at the interface, rather than in the bulk of the solution. The diffusion resistance, ra...

Kinetics and mechanism of zinc extraction from sulfate medium with di(2-ethylhexyl) phosphoric acid.

Kinetic studies of the extraction of zinc from aqueous sulfate solution by di(2-ethylhexyl) phosphoric acid in kerosene were made, using a constant interfacial area cell. Measurements of the extraction and stripping rates led to the identification of rate expressions and a suggested mechanism of this reaction. Based on the nature of the extractant and the reaction mechanism for the formation of zinc complex in the aqueous phase, a simple extraction scheme is proposed in which the rate-controlling step is interfacial. The mass-action constant obtained in the present kinetic study is considered to agree with the extraction constant obtained in the previous equilibrium study. Effects of the total sulfate concentration in the aqueous phase on the extraction and stripping rates were also investigated.

The kinetics and mechanism of solvent extraction of Fe(III) and Cu(II) by oxine reagents—I: The aqueous-phase reaction between Fe(III) and 8-hydroxy quinoline

The kinetics of extraction of Fe(III) from an aqueous nitrate solution into toluene or chloroform solutions of 8-hydroxyquinoline have been studied in a constant interfacial area cell. During this reaction a green ferric-oxine complex is formed in the aqueous phase, and the kinetics of this reaction are reported here. Activation energies for the reaction under various conditions have been calculated, and a detailed reaction mechanism is presented. It is shown that the reaction is controlled by diffusion in both the organic phase and the aqueous phase and that the relative contributions of organic and aqueous phase diffusion to the overall rate are a sensitive function of the iron and proton concentrations.

Mass transfer rate in liquid anion exchange processes—II: Kinetic of iron(III) transfer in the biphasic system trilaurylamine hydrochloride-aromatic diluent, HCl-water

The initial mass transfer rate of Fe(III) in the system trilaurylamine hydrochloride (TLAHCl)-aromatic diluent, HCl-water, has been studied in a constant interfacial area cell as function of the stirring speed of the phases, specific interfacial area and chemical composition of the system. The aromatic diluents benzene and toluene have been used. It has been shown that the rate of extraction is determined by interfacial chemical reactions occurring between the interfacially absorbed molecules of the liquid anion exchanger, TLAHCl, and the bulk species containing iron. Some evidence has been also obtained that the kinetically reactive aqueous iron species can be the neutral complex FeCl 3. A rate expression has been so derived and the rate constants of the interfacial reactions have been evaluated. The rate expression and rate constants have been found to be the same in both the organic diluents. By using the equilibrium law derived from the rate equation it has been demonstrated that distribution data can be predicted from kinetic measurements at time zero with a good degree of accuracy. Finally it has been proved that the proposed reaction mechanism does not vary with time and concentration vs time curves can be predicted from the calculated constants of the interfacial chemical reactions.

Transfer rate of K + ions from aqueous picrate solutions into 1,2 dichloroethane solutions of the macrocyclic polyether dibenzo-18-crown-6

The transfer rate of K + ions from aqueous picrate solutions into 1,2 dichloroethane solutions of the macrocyclic polyether dibenzo-18-crown-6, DBC, has been studied by potassium glass electrode potentiometry using a constant interfacial area cell, at 25°. The rate at time zero has been evaluated as function of the following variables: stirring speed of the phases, interfacial area, volume of aqueous and organic phase, chemical composition. The data have shown that the rate of extraction of potassium can be explained in terms of chemical reactions taking place at the water-organic interphase. The reaction order with respect to both K + and picrate ions has been found equal to one. The reaction order with respect to DBC was found to vary with the DBC concentration from an initial value of one down to zero.

Mass transfer rate in liquid anion exchange processes—III: Kinetics of plutonium(IV) transfer in the biphasic system trilaurylamine nitrate- o-oxylene, HNO 3-water

The mass transfer rate of Pu(IV) in the system trilaurylamine nitrate (TLAHNO 3)- o-xylene, HNO 3-water has been studied in a stirred constant interfacial area cell as function of the chemical composition of the system. Since stirring conditions have been chosen where the influence of film diffusion is considered quite negligible, the rate of extraction has been assumed to be determined by interfacial chemical reactions occurring between the interfacially adsorbed molecules of the liquid anion exchanger, TLAHNO 3, and the bulk species containing plutonium. A rate expression has been derived and the rate constants of the interfacial reactions have been evaluated. By using the equilibrium law derived from the rate equation it has been demonstrated that distribution data can be predicted from the rate constants with a good degree of accuracy. Finally it has been proved that the proposed reaction mechanism does not vary with time and concentration vs time curves can be predicted from the calculated rate constants of the interfacial chemical reactions.

Transfer rate of some tervalent cations in the biphasic system HClO 4, water-dinonylnaphthalenesulfonic acid, toluene—I : Transfer rate of iron(III) determined by chemical reactions

The transfer rate of iron(III) ions between aqueous perchloric acid solutions and toluene solutions of dinonylnaphthalenesulfonic acid has been studied by using a constant interfacial area cell. The initial forward and reverse transfer rates have been evaluated as function of the interfacial area, volume and chemical composition of the system. The results have been explained in terms of interfacial reactions which rate constants have been evaluated. An equation capable to describe the dependence of the transfer rate from both the composition of the system and the time has been derived.