Solvent Extraction Chemistry Research Articles

Chemical and mechanistic modelling of green solvent extraction of metallic species with 4-acylpyrazolones

Solvent extraction chemistry of metals needs the use of suitable organic ligands like 4-acylpyrazolones to coordinate the studied cation, to make it soluble in an organic phase and then allow its phase transfer from the aqueous phase. The competitive solvent extraction test of almost 25 metal ions by one powerful ligand, i.e. 3-methyl-1-phenyl-4-(4-trifluoromethylbenzoyl)-pyrazol-5-one diluted in one ionic liquid ([C1Cnim+][Tf2N−]) has been conducted to get a snapshot of its efficacy. Effect of diluents on the liquid–liquid extraction of 4f-ions with a series of chelating ligands of 4-acylpyrazolones family (∼5) is presented comparing ionic liquids and typical organic diluents: 14 in number. In addition, the solvent extraction of 12 refractory metals with a series of chelating extractants is investigated in five diluents: four 4-acylpyrazolones with different radicals. The solvent extraction stoichiometry of MoO42− and Zr4+ is studied in detail using molecular and ionic diluent for comparative purposes through slope analysis method. Ethylene glycol is used to develop a non-aqueous process for Gd3+ switchable extraction, i.e. boost of two immiscible organic phases. Furthermore, EPR, NMR, IR and DTA-TG-MS spectroscopies have been used to study the extracted d- and f-species in the obtained organic extracts in ionic liquid solutions.

Assessment of the Equilibrium Constants of Mixed Complexes of Rare Earth Elements with Acidic (Chelating) and Organophosphorus Ligands

A survey of the experimental equilibrium constants in solution for the mixed complexes of 4f ions with acidic (chelating) and O-donor organophosphorus ligands published in the period between 1954 and 2022 is presented. These data are widely used in both analytical and solvent extraction chemistry. Important data evaluation criteria involved the specification of the essential reactions, process conditions and the correctness of techniques and calculations used, as well as appropriate equilibrium analysis of experimental data. Higher-quality data have been evaluated, compiled and presented herein, providing a synoptic view of the unifying theme in this area of research, i.e., synergism.

Chemistry of Solvent Extraction of Nd(NO3)3 and Pr(NO3)3 from Nitrate Solutions with TOMAN–TBP Mixtures in Toluene

Chemistry of Solvent Extraction of Nd(NO3)3 and Pr(NO3)3 from Nitrate Solutions with TOMAN–TBP Mixtures in Toluene

Synergistic Extraction of Dysprosium and Aggregate Formation in Solvent Extraction Systems Combining TBP and HDBP

During treatment of nuclear fuel in the Plutonium/URanium EXtraction (PUREX) process, the extractant tri-n-butyl phosphate (TBP) is known to degrade to dibutylphosphoric acid (HDBP), which increases the extraction of metal ions, thereby inhibiting their stripping from the organic phase. To better understand this phenomenon, we investigated how mixtures of TBP and HDBP influenced the extraction of metal, nitric acid, and water, and correlated the results to aggregated structures in the organic phase. The mole ratios of TBP-HDBP mixtures had a non-linear effect on the extraction of Dy3+ and water from 0.2 M HNO3, indicating synergism. In 2 M HNO3, the TBP:HDBP mole ratio had a more linear relation to Dy3+ and water extraction, so the synergistic effect was less pronounced than in the low acid system. The extraction of nitric acid showed no synergistic effect and follows closely what would be expected in a system using TBP only. The small-angle X-ray scattering (SAXS) data of the 0.2 M acid system showed maximum contrast at a TBP:HDBP mole ratio of 0.25, so that the synergistic mixture is also the most aggregated at 0.2 M acid. The 2 M acid system also showed that the mixed system is more aggregated than the end members, although this does not result in peak extraction. Previous studies of synergistic extraction of metal cations explain the enhanced extraction by increased dehydration of the metal ion. Although our data do not rule out the formation of mixed complexes according to the classical mechanism of synergism, our evidence of increased water extraction and aggregate formation in systems combining TBP and HDBP are complementary to the metal-centric dehydration aspects of the process. The findings in this study give insights into the complex chemistry of solvent extraction, providing a possible link between formation of aggregates in the organic phase and synergistic extraction.

Quantum chemical study of extraction characteristics of kinetic synergist OT in liquid membrane using HPMBP as carrier

Kinetic synergic extraction in solvent extraction chemistry was investigated by quantum chemical computations. Density functional theory (DFT) and conceptual DFT studies were carried out for us to analyze the extraction characteristics of kinetic synergist OT (Manoxol OT) in liquid membrane containing HPMBP (1-phenyl-3-methyl-4-benzoyl-pyrazolone-5) as the carrier to separate Cu(II) from Cu–Zn sulfate binary mixture solution. Reactivity indices verify that all the copper(II) complexes are more reactive than the zinc(II) complexes and the Cu(II) site of the copper(II) species is more electrophilic than the Zn(II) site of all the corresponding zinc(II) species in the presence of OT. The quantum chemistry computation demonstrates that the extraction of Cu(II) ions is composed of the two chemical reactions and M(H2O)2A2 (M=Cu and Zn) is an intermediate product. The LUMO of Cu(H2O)2A2 contains high anti-bonding characters and the molecule has a smaller HOMO–LUMO gap. The formation of the intermediate product, Cu(H2O)2A2, evidently improves the selectivity and the extraction rate for Cu(II) ions. The different polarity for CuR2 and ZnR2 provides the evidence on the selectivity of the extraction system for Cu(II) species. Through theoretical computations and the analysis for the intermediate product M(H2O)2A2,we can also forecast the probability of the separation for the different metal ions based on M(H2O)2A2 before solvent extraction and liquid membrane separation experiments, as shown in this work.

Complexation of Palladium(II) with Unsaturated Dithioethers – A Systematic Development of Highly Selective Ligands for Solvent Extraction (Eur. J. Inorg. Chem. 14/2012)

AbstractThe cover picture shows an opened door to a new route in solvent extraction chemistry. By studying a number of unsaturated dithioethers, H.‐J. Holdt et al. have been systematically searching for a selective extractant for the recovery of palladium(II). With the help of a combination of basic research methods, such as theoretical calculations and spectroscopic measurements (magnifying glass), the structure of the chelates has been tuned to fulfill the requirements for use in practice. The washcoat of used automotive catalysts (REM picture) contains, besides palladium, a wide spectrum of other metals. As denoted in the “door” diagram showing two immiscible phases, the ligand of choice exhibits very good extraction performance and is able to selectively transfer palladium(II) from the aqueous phase (dissolved catalyst) into the organic one. This enables recovery of this precious metal from (chemically) challenging secondary sources. Details are discussed in the article on p. 2341 ff. magnified image

Recent advances on the chemistry of solvent extraction applied to the reprocessing of spent nuclear fuels and radioactive wastes

After a brief description of the PUREX process as a starting point, this paper aims to point out some of its most recent developments, always from the viewpoint of the chemistry involved in the solvent extraction methods. In addition to PUREX, other well-known technological approaches devoted to the reprocessing of irradiated uranium and thorium nuclear fuels and general radioactive wastes — TRUEX, DIAMEX, TRPO, DIDPA and UNEX — are also presented and discussed.

Aggregation, Metal Ion Extraction, and Solubility Properties of Silyl-Substituted Alkylenediphosphonic Acids

Partially esterified alkylenediphosphonic acids were shown to be effective solvent extraction reagents for the removal of actinide cations from acidic aqueous solutions into conventional organic solvents. As a first step in an effort to design diphosphonic acid extractants that are soluble in supercritical carbon dioxide, we prepared and characterized a novel series of silyl-substituted alkylenediphosphonic acids. The aggregation of these extractants in toluene at 25°C was studied by vapor pressure osmometry. Their solvent extraction chemistry was investigated by employing radiotracers to determine the distribution ratios for selected metal ions between an acidic aqueous phase and an organic phase containing the diphosphonic acid extractant. To determine the effect of incorporating a silicon functionality into diphosphonic acids, the aggregation and solvent extraction properties of the silyl-substituted alkylenediphosphonic acids were compared with those of the conventional alkyl-substituted di(2-ethylhexyl) alkylenediphosphonic acids. The aggregation and solvent extraction properties of these ligands were shown to vary dramatically as a function of the number of methylene groups bridging the phosphorus atoms of the extractant. Factors including aggregation, P=O basicity, POH acidity, and chelate-ring size were explored to explain features of the solvent extraction data. Additionally, the solubility of the silyl- and alkyl-substituted ligands in supercritical carbon dioxide was studied.

Metal extraction by silyl-substituted diphosphonic acids. II. Effect of alkylene bridge length on aggregation and metal ion extraction behavior

In an ongoing effort to determine the relationship between structure and function in diphosphonic acids, the aggregation and solvent extraction chemistry of four novel silicon-substituted diphosphonic acids, P,P′-di[3-(trimethylsilyl)-1-propyl] propylene- (H2DTMSP[PrDP]), butylene- (H2DTMSP[BuDP]), pentylene- (H2DTMSP[PDP]), and hexylene diphosphonic acid (H2DTMSP[HDP]), were investigated. Vapor pressure osmometry indicates that H2DTMSP[PrDP] and H2DTMSP[PDP] are dimeric in toluene at 25°C, while H2DTMSP[BuDP] and H2DTMSP[HDP] are primarily trimeric and hexameric, respectively. The solvent extraction of selected alkaline earth cations (Ca, Sr, and Ba) and representative tri-, tetra-, and hexavalent actinides [Am(III), Th(IV), and U(VI)], from nitric acid solutions into o-xylene solutions of the ligands has been studied and compared to results reported previously for some analogous di(2-ethylhexyl)-substituted diphosphonic acids. Differences observed in the magnitude of distribution ratios, based on the number of bridging methylene groups, have been explained considering factors such as ligand aggregation, chelate ring size, P=O basicity (qualitatively determined by 31P nuclear magnetic resonance and infrared spectroscopy), and the relative acidities of the ligands.

METAL ION EXTRACTION BY SILYL-SUBSTITUTED DIPHOSPHONIC ACIDS. I. P,P′-DI-[3-(TRIMETHYLSILYL)-1-PROPYLENE] METHYLENE- AND ETHYLENEDIPHOSPHONIC ACIDS

In conjunction with efforts to develop novel actinide extractants that exhibit solubility in supercritical carbon dioxide (SCCO2), the effect of adding silicon-based functionalities to diphosphonic acids on their aggregation and solvent extraction chemistry was investigated. Two silyl-derivatized diphosphonic acids, P,P′-di[3-(trimethylsilyl)-1-propylene] methylenediphosphonic acid (H2DTMSP[MDP]) and P,P′-di[3-(trimethylsilyl)-1-propylene] ethylenediphosphonic acid (H2DTMSP[EDP]), were prepared and their aggregation and metal ion extraction properties compared to those of the previously studied P,P′-di(2-ethylhexyl) alkylenediphosphonic acids. Vapor pressure osmometry of H2DTMSP[MDP] and H2DTMSP[EDP] in toluene (25°C) indicates that, as is the case for the 2-ethylhexyl-substituted alkylenediphosphonic acid analogs, the compounds are dimeric and (primarily) hexameric, respectively, in the concentration range investigated. Distribution ratio measurements for the alkaline earth cations Ca2+, Sr2+, Ba2+, and Ra2+ as well as the representative tri-, tetra-, and hexavalent actinides Am3+, Th4+, and UO2+ 2 between solutions of H2DTMSP[MDP] and H2DTMSP[EDP] in o-xylene and nitric acid indicate that the behavior of these silyl-derivatized compounds closely mimics that of the analogous P,P′-di(2-ethylhexyl) alkylenediphosphonic acids, indicating that incorporation of a silyl functionality has no adverse impact on the metal ion extraction properties of diphosphonic acids.

Solvent Extraction of Cobalt and Nickel—The Chemistry and its Application*

The paper presents a review of the chemistry of solvent extraction of cobalt and nickel with reference to the application in the industry. The electronic configuration and the coordination chemistry of the cobalt and nickel ions provide fundamental basis relating to the extraction and separation.

ChemInform Abstract: Application of the Kamlet and Taft Model in Solvent Extraction Chemistry of Metals

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Application of the Kamlet and Taft model in solvent extraction chemistry of metals

The Kamlet and Taft model is presented in terms of its application in solvent extraction of metals. The following aspects are discussed: (i) effect of diluents upon distribution of extractants; (ii) properties of mixed hydrocarbon diluents and their effect upon solubility of copper(II) complexes with β-diketones; (iii) distribution of different metal complexes with the same ligand or family of ligands; (iv) effect of diluents upon stability of metal chelate adducts with neutral ligand.

Bi- and Tridentate Organophosphorus Compounds for Extraction and Complexation of Metal Ions

Abstract. Studies of structure-reactivity relations were carried out in solvent extraction and coordination chemistry of metal ions Mz+ {Na(I), Mg(II), Ca(II), Sr(II), Ba(II), Ln(III) (Sc, Y, La...Lu), Hf(IV), Fe(II), Co(II), Ni(II), Pd(II), Cu(II), Ag(I), Au(III), Zn(II), Cd(II), Hg(II), Tl(I), Pb(II), and Bi(III)} with 38 bi- and tridentate μ-imido organophosphorus compounds with oxygen and sulfur donor atoms. These compounds are Bronsted acids, HA, and form chelate complexes MAz in most cases. Different modes of coordination are observed. The extraction of metal ions depends not on only on the set of donor atoms, and the acidity and dimerization constant of the organophosphorus compound. In some cases steric effects are dominant. It was also observed an important influence of the diluent.

What's happening at the liquid—liquid interface in solvent extraction chemistry?

The role of the liquid—liquid interface in extraction mechanisms of metal ions is briefly reviewed for chelate extraction, ion-association extraction, and synergistic extraction systems. Recent studies employing the high-speed stirring method uncovered the principal factors governing the role of interfacial phenomena in the kinetics of solvent extraction.

The chemistry of gold solvent extraction from alkaline cyanide solution by solvating extractants

The chemistry of gold extraction from alkaline cyanide solution by solvating extractants, particularly TBP and DBBP, is described. Undiluted TBP is an effective extractant for gold at high ionic strengths, whereas undiluted DBBP needs little ionic strength adjustment in order to extract gold. Other alkyl phosphorus esters, phosphine oxides, sulfoxides, and sulfones also act as solvation extractants. The solvation extraction of gold is thought to occur by ion pair solvation according to the following reaction: ▪ Infrared spectroscopic analysis indicates that there is no specific coordination of the TBP or DBBP to the gold center in the Au (CN) 2 − complex. The significance of the solvation extraction phenomenon in the extraction of gold by modified amines is discussed, and analogies with the adsorption of gold onto activated carbon are drawn.

The chemistry of gold solvent extraction from cyanide solution using modified amines

The concept of amine basicity is discussed and used to explain the selective extraction of gold from alkaline cyanide solution. The apparent basicity of simple weak base amines with respect to Au(CN) 2 can be increased as much as 5 orders of magnitude by the addition of organic phosphorus oxide compounds (TBP, DBBP, etc.). It has been shown that the modified amines do not exhibit this effect to the same extent for other cyanoanions, such as Cu(CN) 3− 4 and Zn(CN) 2− 4. The reasons for this selectivity as well as the stoichiometry of the gold extraction reaction and the nature of the extracted species are described from the results of slope analysis and infrared spectroscopy.

界面活性剤を用いる溶媒抽出法

界面活性剤を用いる溶媒抽出法

Solvent extraction in nuclear technology

Abstract

An introduction to some aspects of solvent extraction chemistry in hydrometallurgy

An introduction to some of the chemical aspects of solvent extraction is given. Terms such as extractants, diluents and accelerators are considered and exemplified by consideration of the extraction of copper using hydroxyoximes. Processes which involve changes in stereochemistry, ligand exchange, and rates of extraction are considered.