INTEKFACIAL ACTIVITY OF 2-HYDH0XY-5-ALKYLBEKZALDEHYDE OXIMES AHD MECHANISM AND KINETICS OF COPPER EXTRACTION

Different adsorption isotherms such as the Gibbs, Szyszkowski,Frumkln and Temkin and polynomial were found as fits well to experimental interfacial tension isotherms for 2-hydroxy-5-alkylbenzaldehyde oximes at octane/water and xylene/water interfaces. The values of surface excess computed according to them increase as the length of the alkyl chain length increases for xylene/water system. Different behaviour was found at octane/water interface.

The interfacial activity data were used to predict reaction orders against hydroxyoxime for different proposed mechanisms of copper extraction from acid sulphate solution.It was shown that an interfacial mechanism is very probable for compounds with long alkyl chains. For these compounds the extraction limiting step is the reaction between hydroxyoxime molecules present near the interface and the intermediate 1:1 complex.     

RATE OF COPPER EXTRACTION AND INTERFACUL ACTIVITY OF MODEL β-DHCETONES

ABSTRACT

Interfacial tension isotherms and rate of copper extraction were studied for model β-diketones of LIX 54 and of pyrazolone type. The effect of the position and structure of the hydrophobic alky1 group upon interfacial activity and rate of extraction is discussed. The preadsorption of extractant molecules at the water/hydrocarbon interface is not needed to obtain a quick and effective extraction.     

The surface excess and the rate of copper extraction by hydroxyoximes

The interfacial tension is determined for some model 2-hydroxy-5-alkylbenzophenone E-oximes, and the surface excess is calculated according to the different adsorption isotherms. The relationship between the rate of copper extraction and the surface excess is discussed. It is shown that, depending upon the adsorption isotherm used to calculate the surface excess, different relations both between the extraction rate and the surface excess and between the surface excess and the oxime concentration are obtained. The interfacial activity of hydroxyoximes is only a qualitative parameter suggesting the interfacial mechanism for copper extraction, and it cannot give strong evidence quantitatively supporting this mechanism. The predicted reaction orders against oxime demonstrate that the reaction between the oxime molecules from the sublayer and the absorbed intermediate complex is probably the limiting step.     

Interfacial activity of 4-alkylphenylamines and the rate of palladium(II) extraction

Interfacial tension isotherms were determined in hydrocarbon-water systems for 4-alkylphenylamines containing from 6 to 16 carbon atoms in their alkyl chains, and the surface excess isotherms were computed and interpreted using various adsorption isotherms. Palladium(II) was extracted with 4-alkylphenylamines from 3 M HCI solutions. The maximum extraction rate of palladium(II) is observed for 4-decyl- and 4-dodecylphenylamines which exhibit good interfacial activity. Compounds soluble in the aqueous phase (4-hexylphenylamine) or in toluene (4-hexadecylphenylamine) extract palladium(II) slower than 4-decyl- and 4-dodecyl- phenylamines.     

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。     

微通道中液-液萃取传质特性的研究

研究了在一个内径为400 μm管式直线型玻璃微通道中的液-液两相的传质特性,其中去离子水为水相, 煤油（溶质是苯甲酸）为油相, 氮气为气相。实验研究了表面张力、黏度和气体分散相对体积传质系数的影响,结果表明：在内径为400 μm的微通道内,当停留时间为15 s时微通道内的萃取已达到平衡;水相的表面张力和液体黏度显著影响微通道内的传质效率;在液-液系统中引入气相后,水油两相之间的传质效率显著增加。     

An improved dynamic combined model for evaluating the mass transfer performances in extraction columns

Dispersed phase droplet behavior research is very important for the design and scaling up of extraction columns. Recently, the droplet velocities at high holdup were found to be uniform, which means the conventional concept of forward mixing needs correction. The drop size distribution only influences the mass transfer coefficients and not the residence time distribution of droplets. In this work, an improved dynamic combined model considering the influence of drop size distribution has been developed, by which the axial mixing can be easily evaluated using a one-dimension search. A typical experimental system of 30% tributyl phosphate (TBP) (in kerosene)-nitric acid-water with interfacial tension of 0.00995 N/m was used to investigate the mass transfer performances in a coalescence-dispersion pulsed-sieve-plate extraction column (CDPSEC) with 150 mm in diameter. The two-point dynamic method was used to obtain the stimulus-response curves. With these results, the axial mixing in the CDPSEC was evaluated. The calculated results showed that the response curves could be predicted by the dynamic combined model with a deviation less than 0.001. This model has marked advantages over previous models in literature because of its accuracy, simple boundary conditions, and single parameter optimization.     

INTERFACIAL ACTIVITY OF HDEHP AND KINETICS OF NICKEL EXTRACTION IN VARIOUS DILUENTS

ABSTRACT

The interfacial behavior of HDEHP at various diluents/0.05M (H₂,Na₂)SO₄ interfaces was examined using the Drop Volume Method. Different adsorption isotherms such as the Gibbs and Szyszkowski were found as fits well to the experimental interfacial tension isotherms. The values of surface excess at saturated interface,calculated according to them by using the concentration of individual species (e.g. organic monomeric species),increase in the order: MIBK<chloroform <benzene～toluene～xylene<CCl₄ <n-hexane～n-heptane

The interfacial activity data were used to discuss the mechanism and kinetics of nickel extraction. It was shown that the interfacial mechanism is very probable and the extraction limiting step is the reaction between HDEHP molecules present near the interface and the intermediate 1:2 complex just as following

Ni(H₂O) ₄A_2(int,0) +2H₂A_2(int,0) =Ni(H₂O) ₂A₂˙2H₂A_2(int,0) +2H₂O_(int,0)

The investigation of the influence of diluent on the extraction rate supports the mechanism suggested.     

HYDRODYNAMICS AND MASS TRANSFER IN A NEW TYPE (FG) STACK PACKED EXTRACTION COLUMN

1 INTRODUCTIONOne of the major objectives in the study of extraction column is to minimize column di-mensions to fulfill a certain specific separation process.This has led to the intensiveemployment of structured packings in extraction columns [1].One of the recentdevelopments targeted for greater interfacial areas without excessive dispersion is the useof structure packings contactive claiming advantages,such as lower fluid flow friction     

环丁砜芳烃抽提体系界面性质的研究

采用悬滴张力仪和计算机图象采集系统研究了环丁砜芳烃抽提体系的界面性质及其对传质的影响。结果表明：在存在传质的条件下，相界面存在强烈的Marangoni现象。界面张力随芳烃浓度的增加而减小，但苯、甲苯和对二甲苯等组分的变化幅度不同。非平衡液的界面张力与组分所在的相及传递方向有关，平衡液的界面张力则与芳烃初始所在的相无关。实验还表明，非平衡液产生界面扰动所需的浓度与芳烃的分配系数(即Marangini数Ma)有关。传质推动力越大，Ma越大，界面扰动的程度也越剧烈。     

Interfacial Behavior of Cyanex 272 and Mass Transfer Kinetics of Ytterbium Using the Constant Interfacial Area Cell

The interfacial behavior of Cyanex 272 has been investigated using the Du Nouy ring method. Different adsorption isotherms such as the Gibbs and Szyszkowski isotherms have been found as fitting well to the experimental data. The values of interfacial excess at the saturated interface increase in the following order: n-heptane > cyclohexane > CCl₄ > toluene > benzene > chloroform, explained according to the stronger solution effect of aromatic hydrocarbon. The effects of temperature, acidity, and ionic strength of the aqueous phase on the interfacial activity of Cyanex 272 are also examined and explained in detail. Moreover, the reaction orders against Cyanex 272 predicted from the interfacial tension isotherms are in agreement with the order determined experimentally, which suggests that the interfacial activity of Cyanex 272 can provide enough strong evidence quantitatively supporting the interfacial mechanism.     

Influence of acid treatment on the surface activity and mass transfer inhibition of a splittable surfactant

A splittable surfactant, Triton SP‐190, was used to evaluate the effects of acid treatment on the mass transfer rate of an extraction process and on the interfacial tension‐lowering activity of a system containing this surfactant. Equilibrium and dynamic interfacial tensions at the interface of CCl₄ and the aqueous phase containing surfactant were measured by using pendent drop tensiometry enhanced by video digitization. A single‐drop extraction apparatus was used to obtain the extraction percentage of acetic acid from the dispersed CCl₄ droplets to the aqueous phase. The results indicate that the inorganic acid treatment can inhibit the dynamic and equilibrium interfacial tension‐lowering activity of Triton SP‐190. The mass transfer resistance induced by the addition of Triton SP‐190 can also be reduced by the pre‐treatment of acid. The effectiveness of acid treatment on both properties was greater at low pH values, lower surfactant concentrations, and longer treatment times. With HCl treatment, the equilibrium interfacial tension was not able to increase to the value of a surfactant‐free system, but approached a maximum value which was independent of the pH value, but dependent on surfactant concentration. On the contrary, the extraction percentage, which has decreased due to the presence of surfactant, can be recovered completely to that of a surfactant‐free system by acid treatment. The acid‐treatment time required to achieve a significant recovery of mass transfer rate was much longer than that required to recover the interfacial tension. The present results also demonstrate that the constituents contained in an acid‐treatment system had different effectiveness in affecting the interfacial tension and mass transfer rate due to the different mechanisms involved. Copyright © 2004 Society of Chemical Industry     

“FORWARD MIXING” MODEL: APPLICATION TO PULSED PLATE EXTRACTION COLUMN OPERATION IN THE EMULSION REGION

The “Forward Mixing” model has been applied to data obtained from a 22 cm diameter pulsed plate extraction column. Measurements of drop size distributions, dispersed phase hold-up and concentration profiles for two systems (toluene-acetone-water and n-butanol-succinic acid-water) of quite different properties were made with the column operating in the emulsion region. Generated drop size distribution function parameters, size-dependent slip velocities and mass transfer coefficients, and continuous phase axial dispersion coefficients were accurate in predicting dispersed phase hold-up and extraction efficiencies (or the related plug flow number of transfer units). These parameters were correlated with phase superficial velocities and pulse velocities. The influence of continuous phase axial dispersion was much greater than the influence of drop size variation, and was not accurately predicted by most previous tracer-based correlations. An inlet dispersed phase distributor was beneficial to the performance with the high interfacial tension system.     

The Interaction of solute transfer,contaminants and dro break-up in rotating disc contactors: Part II. The coupling of the mass transfer and breakage processes via interfacial tension

In order to investigate the influence of solute transfer and of surface active agents on the drop breakage process in liquih liquid extraction columns, their effect on the interfacial tension has to be studied in detail. The difficulty encountered is that the interfacial tension during solute transfer continuously changes and that no simple apparatus is commercially available which can measure these varying interfacial tension values. An attempt has been made here to theoretically predict them. The equations developed to predict the interfacial tension variation can be combined with a model for the breakage process and hence drop size distributions can be calculated from stage to stage. Applying a new combined film mass transfer coefficient model which takes into account the effect of contaminants, single drop extraction performance has been calculated for simplified conditions of constant bulk concentration in the continuous phase. Calculated efficiencies have been compared with experimental data and a good simulation of contaminant effects and dependency on drop size has been found. The calculations were restricted to low dispersed phase hold-up values, so that coalescence effects could be ignored. This work provides the required support for a procedure to be applied to counter-current flow extraction columns.     

Interfacial tension in polymer melts. Part II: Effects of temperature and molecular weight on interfacial tension

Interfacial tension is one of the most important parameters that govern the morphology of polymer blends and the quality of adhesion between polymers. However, few data are available on interfacial tension due to experimental difficulties. A pendant drop apparatus was used for the determination of the interfacial tension for the polymer pair polypropylene/polystyrene (PP/PS). The effects of temperature and molecular weight were evaluated. The range of temperatures used was from 178° to 250°C, and the range of molecular weights used was from 1590 to 400,000. The interfacial tension decreased linearly with increasing temperature. With only one exception, higher molecular weight systems showed weaker dependence of interfacial tension on temperature than lower molecular weight systems. Also, polydisperse systems showed a stronger dependency on temperature than the monodisperse systems. The value of the interfacial tension, which increases with molecular weight, appears to level off at molecular weights above the entanglement chain length. For the polymer pair PP/PS, the dependency of the interfacial tension on the number average molecular weight appears to follow the well-known semi-empirical (?2/3) power rule over most of the range of molecular weights. Comparable correlations were obtained with values of the power between ?1/2 and ?1.0.     

Thermodynamic treatment of interfacial curvature in electrocapillarity

The thermodynamic theory of electrocapillarity is extended to include the explicit dependence of the interfacial tension of an ideal polarized electrode on interfacial curvature. Interfacial curvature adds one additional independent variable to the electrocapillary equation. At any constant curvature, the form of the Lippmann equation, the other first partial differential coefficients of the interfacial tension and the relationship between interfacial tension and differential capacitance depend upon curvature. However, the second cross partial differential coefficients of interfacial tension and the Esin and Markov coefficient have the same form as for a planar electrode. The effect of varying curvature is investigated on the basis of a theory of Tolman, and the results obtained are applied to the estimation of the probable curvature dependence of a mercury electrode.     

The interaction of solute transfer,contaminants and drop break-up in rotating disc contactors: Part I. Correlation of drop breakage probabilities

The breakage process of single drops in RDC liquid-liquid extraction columns has been investigated. The breakage probability and daughter drop size distribution were the measured characteristics. Binary systems, non-equilibrated ternary systems with mass transfer in both directions (c → d and d → c) and systems with surface active agent added were used in the experiments. A model of the breakage probability was developed based on a modified Weber number, taking into account the applied shearing stress and the resisting interfacial tension force. It is shown that breakage probability can be estimated if interfacial tension is known as a function of interfacial conditions.     

Effect of transfer on droplet size in liquid-liquid dispersions

Mean droplet diameter of the dispersed phase in pulsed plate extraction columns was measured for binary and ternary systems. A change in the droplet size in the presence of solute, dependent on such factors as the direction of mass transfer, droplet size in the binary system, radio of diffusion coefficients, viscosity of the continuous phase, interfacial tension and driving force for extraction was observed. Two new empirical correlations of mean droplet sizes in mass transfer conditions are proposed. These correlations have been successfully applied to other extraction columns.     

A CRITICAL REVIEW: SURFACE AND INTERFACIAL TENSION MEASUREMENT BY THE DROP WEIGHT METHOD

The drop weight method has been used as a standard method for surface and interfacial tension measurement. However, lack of appropriate guidelines in using this method has resulted in errors. The specific objective of this critical review is to present the experimental setup, the limitations on the correction factors, and the principle of the drop weight method. Mathematical models of correction factors were evaluated by using a proposed error analysis. The use of the proposed Lee-Chan-Pogaku model and HG-Equation 2 for correction factor determination is suggested. However, further investigations would be required to justify the validity of the correction factors at low r/V^1/3 range and their use for viscous fluids. The physics of drop detachment is complicated; more investigations would be required to form a rigid theory of this method.     

Poly(vinyl alcohol) as a stabilizer in the suspension polymerization of styrene: The effect of the molecular weight

The interfacial tension of the water-(PVA)/styrene system was measured as a function of the poly(vinyl alcohol) (PVA) concentration and temperature. Average size and particle-size distribution were obtained for a suspension of styrene in water using PVA as a stabilizer. We discuss the interfacial tension through the Zykonski equation to establish the behavior of the adsorption isotherms in unstirred systems and discuss the apparently contradictory results of the stirred experiment. We propose a simple configuration model that is congruent with both results. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 71–77, 1998