Synergistic Solvent Extraction Research Articles

Synergistic solvent extraction of neodymium form nitric acid medium using Cyanex 302 and D2EHPA

AbstractIn this research, a binary mixture of Cyanex 302 (bis‐2,4,4 trimethylpentyl monothiophosphinic acid) and D2EHPA (di‐2‐ethylhexyl phosphoric acid) in kerosene was used for extracting neodymium from nitric acid medium. The different variables affecting the extraction of Nd(III) such as contact time, solution acidity, extractant concentration, and temperature were investigated. Stripping of neodymium ions from the loaded organic phase using HCl, HNO3, and H2SO4 for the re‐extraction of neodymium was also carried out. Results indicated that the most efficient reagent for the stripping of neodymium was nitric acid. The extraction reaction of neodymium with the synergistic mixture was determined using graphical method to be NdH5A2B6. The organo‐metallic complex containing neodymium was examined by Fourier Transform Infrared Spectroscopy (FT‐IR). The values of stoichiometric coefficients and thermodynamic parameters were calculated for this mixture. The extraction was an endothermic process, and the thermodynamic functions, ΔH and ΔS were determined to be 10.532 kJ/mol and −123.681 j/mol °K, respectively for the system under study. The Cyanex 302+D2EHPA system not only increased the extraction efficiency of neodymium but also improved the selectivity significantly. The separation factor of neodymium and praseodymium suggested that this mixture would be of practical value in the separation of neodymium.

Separation of rare earth elements by synergistic solvent extraction with phosphonium-based ionic liquids using a β-diketone extractant and a neutral ligand

ABSTRACT We investigated the solvent extraction of four rare earth (RE) elements (Pr, Nd, Tb, and Dy) from Nd-Fe-B magnets using mixtures of 1-(2-thienyl)-4,4,4,-trifluoro-1,3-butanedione (Htta) or 4,4,4-trifluoro-1-phenyl-1,3-butanedione (Hbfa) chelating extractants and tri-n-octylphosphine oxide (TOPO) neutral ligand in phosphonium-based ionic liquids. Based on the results of slope analysis data, the following equations were proposed for the RE extraction: A synergistic effect was observed for the extraction of the RE elements with the combination of extractant and neutral ligand. The values of the equilibrium constant and separation factor were also evaluated in this study. The results reveal that the [NTf2]− anion did not participate in the extraction mechanism of the RE elements, and the Raman spectroscopic analysis of the extracted phase also supported the proposed stoichiometry of the extracted complex. Furthermore, the separation of Tb(III) and Dy(III) from other RE(III) components was investigated through a series of hydrometallurgical processes, which consisted of leaching, removal of [Fe(OH) x ]3-x , and solvent extraction. Finally, the separation of Tb(III) and Dy(III) from other RE(III) components was performed with seven extraction cycles using the HL + TOPO/[P2225][NTf2] system.

Synergetic formulation of Cyanex 272/Cyanex 302 for hexavalent chromium removal from electroplating wastewater

Hazardous hexavalent chromium (Cr(VI)) released from the electroplating industry beyond the discharge concentration limit has created great concern worldwide. Solvent extraction (SX) is an effective method for metal separation from an aqueous system. Throughout this work, novel synergistic solvent extraction of Cr(VI) from rinsed electroplating wastewater was performed using a mixture of two organophosphorus acidic extractants containing di-2,4,4-trimethylpentyl phosphinic acid (Cyanex 272) and di-2,4,4-trimethylpentyl mono-thio-phosphinic acid (Cyanex 302) in kerosene. The results showed almost 99±0.816% of Cr(VI) was synergistically reduced and extracted to the less toxic trivalent chromium (Cr(III)) using the total mixture concentration of 0.1 M (0.04 M Cyanex 272+0.06 M Cyanex 302). For recycling, the organic phase was recycled or reused up to 11 times for excellent extraction (99±0.471%) and stripping (99±0.942%) and became stable afterwards until a certain time. The total concentration of the mixture system was reduced by 50% (0.05 M) using 0.01 M Cyanex 272 and 0.04 M Cyanex 302, with almost 100% of Cr(VI) extraction as less toxic Cr(III). The Cr(III) in the loaded organic phase was completely recovered using 7.0 M hydrochloric acid (HCl). It is concluded that the synergistic extraction using Cyanex 272/Cyanex 302 system improved the Cr(VI) extraction and reduced the chemical consumption in the organic phase.

Opposite selectivities of tri-n-butyl phosphate and Cyanex 923 in solvent extraction of lithium and magnesium.

The synergic solvent extraction system of tri‐n‐butyl phosphate (TBP) and FeCl3 (or ionic liquids, ILs) has been extensively studied for selective extraction of Li from Mg‐containing brines. However, Cyanex 923 (C923), which extracts many metals stronger than TBP, has not yet been examined for Li/Mg separation. Here, we report on the unexpected observation that the C923/FeCl3 system has opposite Li/Mg selectivity compared to the TBP/FeCl3 system. Detailed investigations show that the opposite selectivity of the C923/FeCl3 (or IL) system is due to three factors: (1) the strong extraction of Fe by C923 leads to a low concentration of [FeCl4]− in the system, which is essential for Li extraction; (2) C923 in combination with an IL extracts Mg strongly by an ion‐pair mechanism; (3) most importantly, C923 extracts Mg by solvation, resulting in an insufficient concentration of C923 for Li extraction. The unexpected poor Li/Mg selectivity of C923 highlights the irreplaceable role of TBP in the selective recovery of Li.

Synergistic solvent extraction of lanthanide ions with mixtures of D2EHPA and MIDPA in phosphonium-based ionic liquids

In this study, the synergistic solvent extraction of lanthanide(III) with mixtures of di-(2-ethylhexyl)phosphoric acid (D2EHPA, H2A2) and monoisodecyl phosphoric acid (MIDPA, H2B2) in phosphonium-based ionic liquid was investigated from amide acid medium. The method of slope analysis was used for the determination of the extraction reaction. In the case of D2EHPA or MIDPA single extractant system, Ln(III) (Ln = Pr and Nd) was extracted as [LnA3HA] or [LnB3HB], respectively. Tb(III) or Dy(III) were extracted as [TbH2A2B2(NTf2)] or [DyH2A2B2(NTf2)] instead of [TbA3HA(NTf2)] or [DyA3HA(NTf2)] for D2EHPA and MIDPA synergistic system. According to the equilibrium constants (KA, KB and KAB) and the formation constants (β1, β1 and β3), it was found that the extracted complex [TbHA2B2] or [DyHA2B2] was more stable than [LnA3HA] or [LnB3HB] due to the synergistic effect of D2EHPA and MIDPA. The thermodynamic functions (ΔH, ΔG, and ΔS) were estimated from the temperature dependence of the synergistic extraction system. The result indicated that the synergistic extraction reaction was endothermically driven for this extraction system. Furthermore, the synergistic extraction effects were investigated to study the possibility of separating Dy(III) from Pr(III) and Nd(III) according to their separation factors.

Recovery of scandium from spent sulfuric acid solution in titanium dioxide production using synergistic solvent extraction with D2EHPA and primary amine N1923

High-efficiency and good-selectivity extraction systems are very attractive in the solvent extraction process. A synergistic extraction of scandium (III) from a spent sulfuric acid solution of titanium dioxide production by using a mixture of bis-2-ethylhexyl phosphoric acid (D2EHPA, P204) and primary amine (N1923) has been proposed in this study. The effect of the molar fraction of N1923 in the mixed extractants on the extraction of scandium was studied and the synergistic enhancement coefficient R was calculated. The maximum synergistic coefficient was found to be 12.50 when the H2SO4 concentration was 0.5 mol·L−1 and the molar fraction of N1923 was 0.5. The synergistic extraction mechanism was also discussed. Appropriately 90% scandium could be stripped from the loaded organic phase in the synergistic extraction system when the nitric acid was 6 mol.L−1. The result of FT-IR spectra well verified the conclusion that the synergistic effect owed to the formation of hydrogen bond NH+···OP, causing a much easier dissociation of proton H of P204. Finally, after three-stage counter-current extraction and stripping, Sc2O5 product with a high purity of 90% was obtained from spent sulfuric acid solution by precipitation and calcination.

Selective removal of magnesium from lithium-rich brine for lithium purification by synergic solvent extraction using β-diketones and Cyanex 923.

In the production of battery‐grade and high‐purity Li2CO3, it is essential to remove magnesium impurities. The state‐of‐the‐art solvent extraction (SX) process using Versatic Acid 10 and D2EHPA co‐extracts 3.3–5.5% lithium, while removing 86–98% magnesium. Here, we demonstrate that synergic SX systems containing a β‐diketone (HPMBP, HTTA or HDBM) and Cyanex 923 are highly selective for magnesium extraction over lithium (separation factor α > 1,000). The extracted magnesium and lithium complexes have the stoichiometry of [Mg∙A2∙(C923)2] and [Li∙A x ∙(C923)2] (x = 1, 2), respectively (A represents deprotonated β‐diketone). The three β‐diketone synergic SX systems all considerably outperformed the Versatic Acid 10 system for magnesium removal from a synthetic solution containing 24 g L−1 Li and 0.24 g L−1 Mg. In a three‐stage batch counter‐current extraction, the HPMBP and Cyanex 923 synergic SX system removed 100% magnesium with only 0.6% co‐extraction of lithium. This excellent Mg/Li separation is the best result reported so far.

Synergistic Solvent Extraction of Lanthanides(III) with Mixtures of 4-Benzoyl-3-Methyl-1-Phenyl-5-Pyrazolone and Phosphoryl-Containing Podands

The solvent extraction of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu from weak acidic chloride solutions into an organic phase containing 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone (HP) and phosphoryl-containing podands (L) has been studied. A considerable synergistic effect was observed in the presence of neutral ligands L in the organic phase containing HP. The stoichiometry of the Ln(III) extracted species was determined by slope analysis and the equilibrium constants were calculated. It was found that the lanthanide(III) ions are extracted with mixtures of HP and neutral ligands in toluene from weak acidic solutions as LnLP3 complexes.

Mass transfer evaluation in a multi-impeller extractor for reactive Mo (VI) extraction from aqueous Sulphate solution by utilizing coupling of acid and solvating Extractants

In this study, mass transfer experimental data from the present column with 70 cm active column length and 11.3 cm internal diameter were interpreted for molybdenum extraction with a mixture of D2EHPA and TBP in terms of the axial diffusion model. The influence of extractants concentration and the initial aqueous pH have studied in the bench-scale experiments. The experimental finding demonstrated that the synergistic solvent extraction increases the constancy of the extracted complexes for transfer into the organic phase. The effect of operating parameters, including agitation speed and inlet phase velocities on the overall mass transfer coefficients under the chemical reaction system, is discussed. By considering the reactive extraction system in this column, the results showed that the overall mass transfer coefficients increase with an increase in the agitation speed and inlet phase velocities. It was also found that the column performance is significantly dependent on agitation speed and dispersed phase velocity. However, it slightly depends on the continuous phase velocity. The experiments for solvent extraction processes have performed to obtain the concentration profile along the column in both the aqueous and organic phases as a function of the operating conditions. The available models for the prediction of mass transfer performance were studied, and their predictions have compared with the present mass transfer data. Because of the column geometry and chemical reaction condition, the available empirical models failed to predict the mass transfer data accurately. Therefore, a new correlation had developed to predict the enhancement factor. The values calculated by the proposed model had compared with the experimental data, and a good agreement between them had obtained.

Combining Selective Extraction and Easy Stripping of Lithium Using a Ternary Synergistic Solvent Extraction System through Regulation of Fe3+ Coordination

Lithium is becoming increasingly important due to its essential role in lithium-ion batteries. Over 70% of the global lithium resources are found in salt lake brines, where lithium is always accomp...

Purification of concentrated nickel sulfuric liquors via synergistic solvent extraction of calcium and magnesium using mixtures of D2EHPA and Cyanex 272

A synergistic solvent extraction circuit consisting of D2EHPA and Cyanex 272 was applied to purify a concentrated Ni sulfuric solution ([Ni] = 88 g L−1, [Mg] = 3.1 g L−1, [Ca] = 0.5 g L−1) similar to the MHP industrial liquors that feed the electrowinning step. The temperature was identified as a key parameter to optimize Mg extraction as well as to promote the selective recovery of co-extracted Ni in the extraction stages and make the stripping of Ca feasible using HCl as a stripping agent. Ca was crowded out by Ni from the loaded D2EHPA + Cyanex 272 solution and limited the operating pH range between 2 and 4. Under optimum conditions, 98.0% Ca and 98.4% Mg were simultaneously extracted in two and three theoretical stages by D2EHPA (0.30 M) + Cyanex 272 (0.32 M) mixture (pH 4, A/O ratio = 0.7 and 50 °C). Co-extracted Ni was selectively recovered (99.7%) from the loaded D2EHPA + Cyanex 272 using [H2SO4] = 0.063 M in three stages (O/A ratio = 1 and 50 °C). Ca and Mg can be completely stripped out from the loaded D2EHPA + Cyanex 272 at 50 °C in only 1 ([HCl] = 3 M, O/A ratio = 5) or two theoretical stages ([H2SO4] = 1 M, O/A ratio = 2). The purified liquor containing 80 g L−1 Ni (99.9% purity) can be directed for the electrowinning step to produce Ni cathodes. Extraction and stripping kinetics are rapid (equilibrium reached within 5 min). Thermodynamic analysis was done to support the synergism/antagonism trends observed experimentally.

Synergistic solvent extraction of heavy rare earths from chloride media using mixture of HEHHAP and Cyanex272

The synergistic extraction of heavy rare earths from chloride medium was investigated using the mixture of heptylaminomethylphosphonic acid mono-(2-ethyl-hexyl) ester (HEHHAP, HA) and bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex272, HB) in heptane. The extraction efficiency of heavy rare earths and the separation factors between adjacent lanthanides with the HEHHAP-Cyanex272 mixture are both better than those for the sole HEHHAP or Cyanex272 system. The separation factors between adjacent heavy rare earths are also higher than those for other synergistic systems. The rare earth extraction is a cation exchange process deduced by both slope analysis method and constant molar method. The extracted complexes are determined to be LnH2Cl2A2B (Ln = Yb, Lu). The loaded metal ions can be easily stripped by HCl or H2SO4. The stripping efficiency is over 90% when the concentration of HCl was more than 1 mol/L. The synergistic extraction of heavy rare earths with the mixed HEHHAP-Cyanex272 system is an endothermic reaction. The negative values of ΔG indicates that the extraction reaction of Ln(III) is spontaneous and favorable.

Direct extraction of Mo(VI) from sulfate solution by synergistic extractants in the rotation column

Direct extraction of molybdenum from sulfate solution with synergistic extractants (mixture of D 2 EHPA and TBP) was studied in the rotation column. The influence of extractant concentration and initial pH of aqueous phase was studied in the bench scale experiments. The outcomes demonstrated that the synergistic solvent extraction enhances the constancy of the extracted complexes for transfer into the organic phase. In the continuous experiments, the effect of different operating parameters such as speed of agitation, inlet solvent flow rate and inlet aqueous flow rate on the holdup, mean drop size, drop size distribution, slip and characteristic velocities and extraction percentage were examined. Modified correlations were proposed for prediction of hydrodynamic parameters with consideration of reaction extraction condition in the rotation column. Furthermore, these correlations were compared with the experimental data. According to the results, the direct extraction of Mo(VI) from aqueous solution and sulfuric media with extraction efficiency of 90.4% was obtained at higher rotor speed (240 r·min –1 rpm) in this column.

Synergistic Solvent Extraction Is Driven by Entropy.

In solvent extraction, the self-assembly of amphiphilic molecules into an organized structure is the phenomenon responsible for the transfer of the metal ion from the aqueous phase to the organic solvent. Despite their significance for chemical engineering and separation science, the forces driving the solute transfer are not fully understood. Instead of assuming the simple complexation reaction with predefined stoichiometry, we model synergistic extraction systems by a colloidal approach that explicitly takes into account the self-assembly resulting from the amphiphilic nature of the extractants. Contrary to the current paradigm of simple stoichiometry behind liquid-liquid extraction, there is a severe polydispersity of aggregates completely different in compositions, but similar in the free energy. This variety of structures on the nanoscale is responsible for the synergistic transfer of ions to the organic phase. Synergy can be understood as a reciprocal effect of chelation: it enhances extraction because it increases the configurational entropy of an extracted ion. The global overview of the complex nature of a synergistic mixture shows different regimes in self-assembly, and thus in the extraction efficiency, which can be tuned with respect to the green chemistry aspect.

Selective recovery of Rhenium from industrial leach solutions by synergistic solvent extraction

In our previous work, the selective precipitation of rhenium from an acidic washing solution present in the copper smelting process was studied. The precipitate formed is a polymetallic sulfide that contains rhenium, copper, arsenic, and bismuth. To recover rhenium from the precipitate, the separation of perrhenate ions from industrial leach solutions using synergistic solvent extraction was investigated. For the synergistic extraction system of Alamine 336 and TBP, Alamine 336 is the primary compound that combines with the anions in the leach solution. The solubility of the extraction complex in the organic phase is enhanced by TBP bonding with the neutral complex. For the extraction of perrhenate ion from the chloridizing leach solution, the difference in the distribution coefficient of rhenium and bismuth is small due to the formation of bismuth polychloride complex ion in aqueous solution. For the acidic leach solution using sulfuric acid and ammonia persulfate, the separation percentage of perrhenate ion is more than 99.90 wt% using four-stage countercurrent extraction. This is because the bismuth and arsenic in the leach solution forms an insoluble compound (BiO)2SO4 and arsenic acid. The loaded organic phase is stripped by a 4 mol/L ammonium solution, recovering 98.78% Re. The content of arsenic, copper, bismuth, and lead in the ammonia perrhenate formed from the evaporation and crystallization process using the stripping liquor is less than 0.5 mg/kg and 1.0 mg/kg, respectively.

Methyl-isobutyl ketone and 1-octanol as synergistic agents and phase modifiers in solvent extraction of cobalt(II) by the N-(2-hydroxybenzylidene)aniline from sulfate medium

The synergistic solvent extraction of cobalt(II) from sulfate medium with N-(2-hydroxybenzylidene) aniline in association of two synergistic agents, the methyl-isobutyl ketone (MIBK) and 1-octanolin chloroform at 25 °C, has been studied. Synergistic and antagonistic effects are observed for the title metal at low and high concentration ratios of the synergistic agents. The synergistic extraction of cobalt(II) with the mixtures has been investigated with the methods of slope analysis. The extracted species with the mixtures are CoL2(S)2 and CoL2 (HL) (S) (L, denoted N-(2-hydroxybenzylidene) aniline ion and S denoted MIBK or 1-octanol).

Extraction of Molybdenum (VI) and Vanadium (V) from Nitrate Solutions Using Coupling of Acid and Solvating Extractants (RESEARCH NOTE)

In this study, solvent extraction method has been utilized for separation of molybdenum and vanadium from nitrate solution by utilizing coupling of acid and solvating extractants (D2EHPA and TBP extractants). The outcomes demonstrated that synergistic solvent extraction improves stability of formatted complexes for transfer to the organic phase. The main parameters such as pH value, concentration of extractants, NH4OH concentration as the stripping agent and contact time were optimized at 0.4, 15% (v/v) D2EHPA, 10% (v/v) TBP, 2 M and 30 min, respectively. The maximum separation factor of 24.84 was obtained with a new synergistic mixture of D2EHPA and TBP diluted with kerosene. According to McCabe-Thiel diagram, more than 99% of the Mo (VI) was obtained in counter current procedure and three stage numbers using 15% (v/v) D2EHPA and its mixture with 10% (v/v) TBP in kerosene, initial aqueous pH value equal to 0.4 and A/O ratio of 4/1 at room temperature for 30 min. In addition, stripping of Mo (VI) reached 98.75% in three counter current stages using 2 M NH4OH as stripping agent and A/O ratio of 1/4 for 30 min.

Synergism and Aggregation in Multi-Extractant Solvent Extraction Systems

ABSTRACT Several combinations of lipophilic extractants have been studied with the objective of investigating the synergistic behavior of metal ion extraction and its relation to reverse micelle formation. Combinations of acidic and neutral extracting reagents that have displayed synergic behavior in other studies were tested. While most of these either showed limited synergy or no correlation with water uptake under the conditions used here, two of the systems showed extraction synergy. These two extraction systems: 2-bromodecanoic acid with 2,2ʹ:6ʹ,2ʺ-terpyridine; and tributyl phosphine oxide with 2-thenoyltrifluoroacetone were modeled based on two different theoretical approaches: microemulsion-assisted extraction; or the formation of mixed complexes in the organic phase. Comparisons between the two models showed that in the case of bromodecanoic acid and terpyridine the approach of mixed complexes provided a somewhat better fit while the second system was not modeled well with either approach. Further work on the species present in the organic phase is needed to determine the role, if any, of aggregates in synergistic solvent extraction systems.

Application of the data on dielectric constant and viscosity of binary mixtures to the selection of synergistic solvent extraction-binary mixtures of Cyanex and tertiary amine (TEHA)

The binary mixtures of Cyanex compounds and tertiary amine have been employed for the synergistic solvent extraction of metal ions. Viscosities and dielectric constants of the binary mixtures consisting of Cyanex compounds (Cyanex 301, Cyanex 272, Cyanex 921 and Cyanex 923) and tertiary amine (TEHA) were measured at 293 K. The interaction between the constituents in the binary mixture was interpreted by analyzing the deviation values and Grunberg-Nissan interaction parameters (d) of viscosity and dielectric constant. Among the binary mixtures employed in this work, the mixture of Cyanex 301 and TEHA showed the strongest interaction (the maximum magnitude of deviations of viscosity and dielectric constant for this mixture was 3.30 mPa·s and 157.55), which was in good agreement with the FT-IR data. The necessary parameters for Redlich-Kister equation were successfully estimated from measured values of the deviation of the viscosity and dielectric constant of the mixture of Cyanex 301 and TEHA. Our results indicated that excess properties and Grunberg-Nissan interaction constant of a binary mixture might provide some information on the nature of the intermolecular interactions in the binary mixture and on the selection of an appropriate mixture for the solvent extraction of metal ions.

HYDROMETALLURGICAL PROCESSING OF NICKEL LATERITES- A BRIEF OVERVIEW ON THE USE OF SOLVENT EXTRACTION AND NICKEL/COBALT PROJECT FOR THE SEPARATION AND PURIFICATION OF NICKEL AND COBALT

In this study, a brief overview of the solvent extraction (SX) application for the separationand purification of nickel and cobalt in hydrometallurgical processing of laterite nickel ores ispresented. This paper consists of two parts: firstly, the SX of nickel and cobalt from sulphateleach solutions is described; and secondly, the development of hydrometallurgical plants forthe processing of laterite nickel ores that involve solvent extraction technique is discussed. Themost important extractants are shortly given in the first part of the study. It is seen that theextraction and separation of nickel and cobalt from the impure leach solution of laterite nickelores can be performed by either using a single extractant system that is called as a direct solventextraction (DSX) or a mixture of two or more extractant which is known as a synergistic solventextraction system (SSX). Mixed sulphide precipitation (MSP) and mixed hydroxide precipitation(MHP) processes are mentioned. This paper is also addressed advantage and disadvantages ofeach extraction system. It is shown that capital investment expenditure, operational investmentexpenditure and mineralogical content are the most important factors that can affect the selectionof the appropriate hydrometallurgical process for lateritic nickel ore.