Metal Sorption by Materials with a Mobile Phase of Extractants

Data on sorption of rare, noble, radioactive, and nonferrous metals from aqueous solutions by impregnates and TVEXs were analyzed. These are materials combining the properties of sorbents and extractants and differing in the production method. Their distinctive feature is that the extractant is not chemically bonded to the solid support, which is responsible for high kinetic characteristics of sorption processes involving these materials, favorably comparing with conventional sorbents. As a mobile phase to be deposited on the carrier (mainly polymeric) in the case of impregnates or to be introduced during synthesis of TVEXs served organophosphorus extractants, amines, quaternary ammonium bases, etc. Information regarding the effect of various parameters (solution acidity, metal concentration, phase ratio, temperature, and concentration of impurity elements) on separating capability and metal sorption capacity and kinetics was provided for this type of materials. Methods used for stabilizing the properties of impregnates with the view to minimize the extractant loss during application were considered.

     

Synergistic solvent extraction of Eu, Sr and Cs into chlorobenzene solutions of the three conformers of tetrathiocalixarene and dicarbollide

Solvent extraction of several long-lived fission products from diluted nitric acid in pronounced synergistic systems involving dicarbollide and conformers of a specific thiacalix[n]arene were investigated using mainly chlorobenzene as the diluent. The following factors were experimentally investigated: molar ratio of the two extractants, total extractants concentration, aqueous acidity, nature of the mineral acid used, relative phase volumes, repeated extractions and metal concentration. Data are given on the rather slow kinetics of extraction and stripping, limited chemical stability of the extractants, selectivity and interference of foreign metals. The three different conformers of the basic compound with identical chemical composition exhibit very differing extraction properties. The plots of distribution ratios of all metals tested versus the varying concentration of one extractant keeping the concentration of the other extractant constant invariably exhibit maxima, interpreted as the result of an existence of several extracted species in the extract. Suggestions are given concerning possible practical applications of two of the conformers studied.     

Interfacial behavior of DEHEHP and the kinetics of cerium(IV) extraction in nitrate media

The effects of diluents, temperature, acidity, and ionic strength of the aqueous phase on the interfacial properties of DEHEHP have been extensively investigated using the Du Nouy ring method. In addition, the effect of cerium(IV) concentration loaded in the organic phase on the interfacial tension has also been studied. With the increase of DEHEHP concentration, the value of interfacial tension (gamma) decreases in the studied system, which shows that DEHEHP has interfacial activity as a kind of surfactant. The surface excess at the saturated interface (Gamma(max)) and the minimum bulk concentration of the extractant necessary to saturate the interface (C(min)) under the different conditions are calculated according to two adsorption equations such as the Gibbs and Szyszkowski functions to be presented in comprehensive tables and figures. The relationship between the interfacial activity of DEHEHP and cerium(IV) extraction kinetics by DEHEHP has been discussed by considering different factors such as the effects of diluents and temperature. However, the interfacial activity parameter of extractant only is a qualitative parameter, but cannot provide strong enough evidence to quantitatively explain the relationship between extraction kinetics and interfacial properties of an extractant.     

Adsorption at the liquid/liquid interface in mixed systems with hydrophobic extractants and modifiers 1. Study of equilibrium interfacial tension at the hydrocarbon/water interface in binary mixed systems

Equilibrium interfacial tension at the liquid/liquid interfaces for two chelating metal ion extractants, 2-hydroxy-5-nonylacetophenone oxime (HNAF) and 1-phenyldecane-1,3-dion (beta-diketone), two solvating extractants, trioctylphosphine oxide (TOPO) and tributyl phosphate (TBP), and a modifier, decanol, were obtained with a drop volume tensiometer. Moreover, four equimolar binary mixtures of extractant/extractant and extractant/modifier type were considered. The composition of the mixed adsorbed monolayer and the molecular interaction parameters beta were determined by the Rosen equation. It was found that in all the studied systems coadsorption exists; however, synergism in the reduction of interfacial tension was not observed. The obtained results indicate that in the case of three mixtures considered the composition of a mixed monolayer at the hydrocarbon/water interface was quite different from that in the bulk organic phase. Only for the TOPO/beta-diketone mixture were the compositions at the interface and in the bulk organic phase similar. The obtained results indicate that it is impossible to predict the composition of a mixed monolayer by taking into account the interfacial activity of individual components of the mixture. In some cases the compound shows lower interfacial activity (smaller efficiency and effectiveness of adsorption) and occupies a dominant position at the interface, regardless of the type of hydrocarbon used as the organic diluent.     

聚偏氟乙烯中空纤维膜器对钐传质性能的影响

以Ｐ５０７－煤油ＨＣｌ－Ｓｍ为实验体系,在两种聚偏氟乙烯中空纤维膜器中研究了溶胀性能、反萃酸度对基于水相的总传质系数及中空纤维膜孔径的影响,考察了料液酸度、萃取剂浓度、钐离子浓度与萃取速率的关系。获得了相应的反应级数。根据界面反应动力学,得到了速率常数值和动力学方程。     

Extractant Effect on the Retention of the Stationary Phase in a Rotating Coiled Column

The effects of physicochemical properties of two-phase liquid systems (interfacial tension and differences in density and viscosity) on the retention of the stationary phase in the column were examined. These effects mainly determine the separation parameters of compounds. Extractant/decane–aqueous phase systems were used; their physicochemical properties changed both as a result of adding an extractant (di-(2-ethylhexyl) phosphoric acid, trioctylamine, or tributyl phosphate) to the organic solvent and because of a change in the composition of the aqueous phase. Aqueous ammonium sulfate of varying concentration was used as a mobile phase. It was shown that interfacial tension substantially affects the behavior of the systems under consideration. An increase in the ammonium sulfate concentration only slightly affects the retention factor of the stationary phase in the column. With a proper choice of the stationary phase, countercurrent chromatography can be used for the extraction of components from salt solutions of various concentrations.     

膜基萃取中钕、钐的传质及界面反应动力学

采用自制聚偏氟乙烯中空纤维膜吕,在HEH／EHP煤油体系不,对钕,钐的萃取及界面反应进行了研究。结果表明,膜器中的萃取反应与液－液萃取相同,可视为准一级反应。考察了料液酸度,萃取剂浓度,钕,钐离子浓度与萃取速率的关系,获得了相应的反应级数,根据界面反应动力学,得到了动力学方程,速率常数及钕,钐的分离系数。     

Extraction of cobalt(Ⅱ) from aqueous solution by N,N'-carbonyl difatty amides

The development of economic and environmentally friendly extractants to recover cobalt metal is required due to the increasing demand for this metal.In this study,solvent extraction of Co(Ⅱ) from aqueous solution using a mixture of N,N’-carbonyl difatty amides(CDFAs) synthesised from palm oil as the extractant was carried out.The effects of various parameters such as acid,contact time,extractant concentration,metal ion concentration and stripping agent and the separation of Co(Ⅱ) from other metal ions such as Fe(Ⅱ),Ni(Ⅱ),Zn(Ⅲ) and Cd(Ⅱ) were investigated.It was found that the extraction of Co(Ⅱ) into the organic phase involved the formation of 1:1 complexes.Co(Ⅱ) was successfully separated from commonly associated metal ions such as Fe(Ⅱ),Ni(Ⅱ),Zn(Ⅲ) and Cd(Ⅱ).Co(Ⅱ) stripping from the loaded organic phase was studied in aqueous solution.These results are useful to recover Co(Ⅱ) from aqueous solution utilising(CDFAs) as an extractant.     

Liquid-supported membranes in chromium(VI) optical sensing: transport modelling

Flat sheet liquid-supported membranes (FSLSM) containing Aliquat 336 as a carrier have been evaluated as sample interface in an optical sensor for Cr(VI) monitoring. A model describing the transport mechanism of Cr(VI) through the membrane is reported. The model considers a diffusion process through a feed aqueous diffusion layer, a fast interfacial chemical reaction and a diffusion of ALQHCrO₄ and (ALQ)₂CrO₄ species through the membrane (Aliquat 336, ALQ). The mathematical equations describing the transport rate are derived and they correlate the membrane permeability coefficient to diffusional and equilibrium parameters as well as to the chemical composition of the system, i.e. extractant concentration in the membrane phase and acidity in the feed phase. The experimental data are explained by the derived equations and the diffusion resistances to mass transfer are evaluated. The influence of other experimental parameters, such as stirring speed in the feed phase and nature of the diluent and stripping agent on the transport is also discussed. Experiments with optical detection demonstrate the suitability of liquid-supported membranes (LSM) containing ALQ as interfaces for optical sensing.     

Separation of Uranium(VI) by Extraction with Dibutylditiophosphoric Acid

The extraction of uranium(VI) from aqueous solutions with dibutylditiophosphoric acid in organic solvents was studied. The influence of different factors as pH of the aqueous phase, extractant concentration and nature of solvent was investigated in order to find the optimum conditions for separation of metal from aqueous nitrate solutions. The effect of neutral donor extractants was also searched and the efficiency of the extraction was calculated.     

溶剂挥发法制备萃取剂微胶囊

萃取剂微胶囊的制备是利用微囊化方法将萃取剂包覆起来 ,解决传统液液萃取中的两相相分散、相混合、相分离以及溶剂的损失和设备结构复杂等问题 .用简单易控制的溶剂挥发法成功制备了聚砜及聚苯乙烯材料包覆的多种萃取剂 (如磷酸三丁酯 ,2 乙基己基磷酸 ,三辛胺和Aliquat 336 )微胶囊 ,并考察了壁材和分散剂的选择对不同萃取剂进行包覆的影响 ,同时研究了搅拌速度和膜溶液组成对微胶囊的形态、萃取剂包覆量的影响 .结果表明 ,(1)用聚砜作壁材可以包覆磷酸三丁酯、2 乙基己基磷酸 ,而用聚苯乙烯可以包覆三辛胺、Aliquat336 ;(2 )对于不同的O W乳液体系 ,只有选择合适的分散剂 ,才能得到理想球形状、分散性好的微胶囊 ;(3)增大搅拌速度可以降低液滴尺度 ,从而减小微胶囊粒径 ;(4)膜溶液组成的影响则表现在两个方面 ,一是膜溶液的粘度和两相界面张力是除搅拌速度外微胶囊粒径的决定因素 ,二是膜溶液中壁材与萃取剂的比例优化时 ,才能得到萃取剂包覆量高的微胶囊 .     

Adsorption at the liquid/liquid interface in mixed systems with hydrophobic extractants and modifiers. 2. Dynamic interfacial tension at the hydrocarbon/water interface in binary mixed systems

The dynamic interfacial tension for binary mixtures of hydrophobic metal ion extractants and a modifier were measured by using the drop volume technique. Four types of equimolar mixtures were considered: two chelating extractants: 2-hydroxy-5-nonylacetophenone oxime (HNAF) and beta-diketone (1-phenyldecan-1,3-dion), two solvating extractants: trioctylphosphine oxide (TOPO) and tributyl phosphate (TBP), chelating and solvating extractants TOPO and beta-diketone, and the chelating extractant HNAF and the modifier (decanol). With the aid of the Ward and Torday equation the values of the diffusion coefficients of individual compounds and their equimolar mixtures were estimated. It was found that in the case of two types of investigated mixtures, i.e., HNAF + beta-diketone and HNAF + decanol the compound HNAF that was dominant in the mixed adsorbed monolayer and the more interfacially active also determined the kinetics of adsorption in mixed systems. In contrary to the mixture of two chelating reagents, in the case of a mixture of two solvating extractants the mixed system behaves like the less active, though dominant at the interface, reagent TBP. The same effect was observed in both of the considered diluents (toluene and octane).     

Interfacial Activity of Trioctyloamine in Hydrocarbon/Water Systems with Nonorganic Electrolytes

Interfacial tension and surface excess isotherms for trioctylamine (TOA) were determined and interpreted. Despite its high hydrophobicity, TOA adsorbs at the hydrocarbon/water interfaces and decreases effectively the interfacial tension, especially in systems containing acidic aqueous phase. Interfacial activity of TOA rises with an increase of the aqueous phase acidity. The effect of amine protonation is clearly observed. Interfacial tension isotherms obtained experimentally can be well matched with the Szyszkowski equation. The interfacial activity of TOA is affected by the type of the organic diluent and the composition of the aqueous phase, i.e., the kind and concentration of nonorganic electrolyte present in the system. Copyright 2001 Academic Press.     

Solvent extraction of metals with hydroxamic acids

Solvent extraction with hydroxamic acids has been investigated. with comparison of aliphatic and aromatic reagents for the extraction of iron, copper, cobalt and nickel. Caprylohydroxamic acid has been evaluated for use in extraction systems for titanium, vanadium, chromium, molybdenum and uranium, both in terms of acidity of aqueous phase and oxidation state of the metal. It has been established that caprylohydroxamic acid in 1-hexanol is a suitable extractant for the removal of titanium(IV), vanadium(V), chromium(VI), molybdenum(VI) and uranium(VI) from 6M hydrochloric acid.     

Estimation of trioctylphosphine oxide (TOPO) diffusion coefficients by dynamic adsorption measurements in model extraction systems

Equilibrium interfacial tension and surface excess isotherms for trioctylphosphine oxide (TOPO) were determined and interpreted. Despite its high hydrophobicity, TOPO adsorbs at the hydrocarbon/water interfaces and decreases effectively the interfacial tension. The interfacial activity of TOPO is affected by the type of organic diluent and the composition of the aqueous phase, i.e., the kind (HNO(3), KNO(3)) and the concentration of nonorganic electrolyte present in the system. Significant lowering of TOPO interfacial activity is observed with an increase of the aqueous phase acidity. The dynamic interfacial tension for TOPO was measured by using the drop volume technique. With the aid of the Ward and Tordai equation the values of the diffusion coefficients of TOPO were estimated. The values determined were in the right order of magnitude compared with the literature data.     

酰胺荚醚类萃取剂结构对Gd(Ⅲ)萃取性能的影响

本文合成了4种新型不对称酰胺荚醚萃取剂:N,N′-二甲基-N,N′-二苯基-3-氧戊二酰胺(DMDPhDGA)、N,N′-二甲基-N,N′-二己基-3-氧戊二酰胺(DMDHDGA)、N,N′-二甲基-N,N′-二辛基-3-氧戊二酰胺(DMDODGA)、N,N′-二甲基-N,N′-二癸基-3-氧戊二酰胺(DMDDDGA)。以氯仿为稀释剂,研究了N,N,N′,N′-四丁基-3-氧戊二酰胺(TBDGA)及上述4种萃取剂从硝酸体系中萃取Gd(Ⅲ)的反应机理,得出萃取能力顺序为:DMDHDGA>DMDDDGA>DMDODGA>DMDPhDGA>TBDGA。考察了水相酸度和萃取剂浓度对萃取分配比的影响,得出萃合物中有3个萃取剂分子同时参与配位;并结合红外光谱解释了萃取剂结构与萃取性能的关系。     

Influence of Alkyl Chain Length and Structure on the Extraction of Copper(II) from Aqueous Acid by 5-Alkyl-2-hydroxybenzaldoximes in Hydrocarbon Solvents: Diffusion Coefficients of Extractants and Their Complexes

Measurement of the kinetics of extraction of copper(II) by 19 different 5-alkyl-2-hydroxybenzaldoximes (alkyl is C7H15 and C9H19) from acidic (hydrogen sulfate buffer) aqueous solution in the range pH 3.4-2.0, into 20% v/v toluene in n-hexane is reported. The lowering of the interfacial tension has been measured in some cases. The solubility of the extractants in water has been measured spectrophotometrically. A modified Taylor-Aris dispersion technique has been used to measure the diffusion coefficients in n-hexane and Orfom SX7 of some of the extractants and of the copper(II) complexes which they form. At low initial bulk concentrations (<10 mol m-3) of the extractants, the rate of extraction is controlled by the rate of diffusion of the extractant from the bulk to the organic-aqueous interface. The diffusion coefficient is related to the steric bulk of the alkyl substituent. At higher initial bulk concentrations (200 mol m-3) of the extractants, when the interface is saturated, the rate of extraction is inversely related to the apparent steric bulk of the alkyl substituent. Copyright 1999 Academic Press.     

Bisacylated diethylenetriamines as extractants for nonferrous metals from hydrochloric acid solutions

A series of bisacylated polyethylenepolyamines with linear and α-and α,α′-branched substituents were synthesized. The effects of the number of the nitrogen atoms in the polyethylenepolyamine fragment of the reagent and of the length and branching of its alkyl radicals on the extractant distribution between the organic and aqueous phases was studied. The performance characteristics of the extractants, such as the loss with the aqueous phase, hydrolytic stability, back extraction conditions for nonferrous metals, and Zn(II)/Fe(III) and Zn(II)/Cu(II) partition coefficients, were examined.     

溶剂萃取法处理含六甲基磷酰三胺的废水

六甲基磷酰三胺 (Ｈｅｘａｍｅｔｈｙｌｐｈｏｓｐｈｏｒａｍｉｄｅ ,简称ＨＭＰＡ)是一种无色的极性非质子有机溶剂 ,具有较高的沸点、较高的介电常数、较强的碱性等特性 ,广泛应用于化学反应的介质、离析金属络合物、溶解气体如乙炔、溶解有机和无机盐类以及溶解高聚物 ,也可用作聚合反应的共催化剂 ,是一种十分重要的有机溶剂[1,2 ] 。国内的聚苯硫醚合成研究广泛采用了ＨＭＰＡ作为溶剂 ,目前 ,聚苯硫醚正处于产业化阶段 ,ＨＭＰＡ的用量增加 ,生产产生的废水必须经过处理才能排放 ,否则会对环境造成严重的污染和资源的浪费。但由于ＨＭ…     

Interfacial activity of benzyloctadecyldimethyl ammonium chloride in a liquid/liquid extraction system

Interfacial tension and interfacial adsorption parameters for benzyloctadecyldimethyl ammonium chloride (BODMAC) in three organic diluents were determined and interpreted. The interfacial activity of BODMAC is affected by the type of the organic diluent and the composition of the aqueous phase. The general order of interfacial activity of BODMAC is n-heptane (5% isobutanol) > carbon tetrachloride > chloroform. The effectiveness of adsorption of BODMAC is not only dependent on the organic diluent, but also on the inorganic electrolytes in the aqueous phase.