Solvent Extraction Experiments Research Articles

Evaluation of an Extraction Chromatographic Resin Based on the DOODA Extractant: Characterization, Comparison to DGA, and Potential Applications

ABSTRACT The extraction of selected metal ions by an extraction chromatographic (EXC) resin containing N,N,N’,N’-tetraoctyl-3,6-dioxaoctane diamide (DOODA) on a porous methacrylate support was measured from nitric acid and hydrochloric acid. Metal ion extraction with the DOODA resin was compared to structurally similar diglycolamide (DGA) resins containing the extractants N,N,N’,N’-tetraoctyl-diglycolamide (TODGA; DGA, Normal resin) and N,N,N’,N’-tetra(2-ethyl-1-hexyl)-diglycolamide (TEHDGA; DGA, Branched resin). The EXC resins were studied via batch uptake, column elution, extraction capacity, and column stability experiments focusing on potential applications in analytical radiochemistry and nuclear medicine isotope production and purification. The DOODA resin exhibited similar extraction trends to the DGA resins for many metal ions, however, the capacity factors (k’) were reduced, typically following the trend of DGA, normal > DGA, branched > DOODA. The selectivity of DOODA resin towards rare earth elements, trivalent actinides, and some transition metal ions, particularly Cd, Ca, and Ac, is quite different from the existing DGA resins, but follows trends previously identified in solvent extraction experiments. The capacity for extraction of Ca(II) and Eu(III) from nitric acid was higher for the DOODA resin than either DGA resin, while all resins exhibited little extractant loss to the mobile phase over >18,000 bed volumes of elution.

Supported liquid membrane with selective stripping for separative recovery of copper and zinc from plating wastewater

For separation and recovery of different but chemically similar metal from dilute wastewater with reduced process complexity and cost, a supported liquid membrane (SLM) system that utilizes a single carrier together with strip dispersion for selective stripping of coextracted metal ions was proposed to enable concurrent separation and recovery. This study aims to investigate the effectiveness of the proposed SLM system for separative recovery of copper and zinc from real plating wastewater. Solvent extraction experiments were conducted to understand the effect of feed pH and carrier concentration on organic phase migration to the aqueous phase. The effect of stirring speed on the SLM transport rate was studied using synthetic feed. Combined with the insights from our previous study, appropriate settings were identified and applied to the SLM system. The SLM system could recover 83.7% copper with 91.0% purity and 85.5% Zn with 99.3% purity from the plating wastewater in 30 h. The findings indicate the feasibility of using SLM with selective stripping for the concurrent separation and recovery of copper and zinc from a dilute aqueous waste stream predominantly containing these two metals.

Process Optimization Using Box‐Behnken Design for the Solvent Extraction and Separation of Iron, Cobalt, and Nickel from Simulated Crud Solution

AbstractThe corrosion product deposit (crud) found on the surface of the fuel rod of the pressurized water reactors (PWRs) chiefly made up of nickel ferrite. Fe, Co, Ni and Cr are the major elements exist in PWR crud. Ascribable to the simplicity in execution, handling, and option for recyclability, solvent extraction technique has been broadly used in nuclear energy sector. In the present investigation, the recovery of iron, cobalt, and nickel has been studied from simulated crud solution in nitrate medium using a novel hydrophobic menthol‐decanoic acid‐based deep eutectic solvent. Process parameters such as pH, DES concentration and shaking time were considered as input variables, and concentration of Fe, Co, and Ni as response variables for the design of experiments. Response surface methodology via Box‐Behnken design using polynomial quadratic model was selected for optimization of solvent extraction experiments. A total of 17 runs were conducted and the results were used for optimization purpose. Complete separation of Co/Fe and Co/Ni is achievable under various extraction conditions. As per the BBD analysis, the optimization conditions obtained were pH=1.9, [DES]=2.99 mol/L and shaking duration=18.27 min. Under these conditions,the amount of Fe, Co and Ni extracted were found as 32.29 g/L, 0.2111 g/L, and 19.83 g/L, respectively.

In-situ adsorptive pyrolysis of e-waste using coal and rice husk fly ash as alternative adsorbents for energy and precious metal recovery by solvent extraction

This paper aims to use in-situ adsorptive pyrolysis combined with ultrasonication and solvent extraction for precious metal recovery from e-waste. The pyrolysis of discarded printed circuit board (PCB) and waste cable (WC) resulted in pyrolysis oil yields of 4.2–13.0 and 6.8–13.5%, respectively. Aliphatic and single-ring compounds were the major components of the pyrolysis oil. The pyrolysis char was ultrasonicated at 40 kHz for 20, 30, and 40 min at 35 °C to separate precious metals in pyrolysis char. The amounts of Au and Ag recovered by solvent extraction experiments with 2%vol HCl/2%vol HNO3, 2%vol HNO3 and 2%vol I2/2%vol H2O2 were 36.3–61.4 and 60.7–79.9%, respectively. The total energy recovery from the pyrolysis char, oil, and gas obtained from the pyrolysis of PCB was 9.0–9.2 MJ/kg. These results indicated that in-situ adsorptive pyrolysis with ultrasonication and solvent extraction could potentially facilitate e-waste conversion for energy and metal recovery processes at a lower cost.

Separation of nickel and cobalt from nitrate leaching solutions of laterite ore by solvent extraction using trihexyltetradecylphosphonium bis (2,4,4-trimethyl pentyl) phosphinate

This study used solvent extraction to separate nickel and cobalt from nitrate leaching of mixed nickel-cobalt oxalate precipitate (MOP). Laterite ore was first leached using citric acid, and then leaching filtrate was mixed with oxalic acid to produce MOP. MOP was releached using nitric acid (1M) to prepare the aqueous phase as a feed for solvent extraction. Solvent extraction used the extractant trihexyltetradecylphosphonium bis (2,4,4-trimethyl pentyl) phosphate (Cyphos®IL 104) in kerosene. Solvent extraction experiments were conducted in the pH range of 6 to 7.6 (O/A ratio = 1 at 15 min). After separation, the concentration of the aqueous phase was analyzed using an ICP-Optical Emission Spectrometer (ICP-OES) to measure cobalt and nickel content. The results showed that the highest extraction efficiency of cobalt and nickel was obtained at pH 7.2, 99.97%, and 32.57%, respectively. At this optimum condition, the separation factor obtained for cobalt was 8008.66 and for nickel 0.0001, while cobalt was 3868.00 and nickel 0.48 for the ion distribution obtained. It indicates that at this condition, the extractant can extract cobalt to the organic phase, and nickel remains in the aqueous phase.

Solvent extraction separation of Au(III) from Pd(II), Cu(II), Ni(II) in HCl solution using cationic, neutral and basic extractants

AbstractBACKGROUNDEtching solutions of spent printed circuit boards (PCBs) contain precious metal ions like Au(III) and Pd(II) together with Cu(II). Therefore, it is crucial to recover Au(III) and Pd(II) from these solutions. To investigate the possibility of separating Au(III) from the etching solutions, solvent extraction experiments were conducted using synthetic hydrochloric acid solutions containing Au(III), Pd(II), Cu(II), and Ni(II). The solvent extraction behavior of these four metal ions was investigated by using cationic (Cyanex 301, LIX 63), neutral (Cyanex 923 and TBP), and basic (Alamine 336 and Aliquat 336) extractants in the HCl concentration range from 1 to 9 M.RESULTSTBP and Cyanex 923 were successful in separating Au(III) from other metal ions when the HCl concentration was higher than 7 M. When the concentrations of Au(III) and Pd(II) changed from 0.1 to 5 g L−1, TBP was able to selectively extract Au(III) from 7 M HCl solution, while Cyanex 923 was effective in separating Au(III) from 9 M HCl solution. However, Au(III) and Pd(II) were co‐extracted by Alamine 336 and Aliquat 336 from 1 M HCl solution. Thiourea or a mixture of thiourea and HCl solution effectively stripped Au(III) from the loaded organic phases of TBP, Cyanex 923, and amines.CONCLUSIONSAmong the six kinds of the extractants employed in this work, TBP was recommended as an extractant for the selective extraction of Au(III) from the HCl solutions containing Cu(II), Ni(II) and Pd(II) on the basis of high separation degree. © 2023 Society of Chemical Industry (SCI).

Wettability and fluid characterization in shale based on T1/T2 variations in solvent extraction experiments

Rock wettability and pore fluid properties are critical parameters for evaluating shale reservoirs, enhancing oil recovery, sequestering waste, and storing energy. Multiple petrophysical and geochemical experiments are routinely used to characterize these properties of shales. Two-dimensional nuclear magnetic resonance (NMR)-based shale evaluation methods usually rely on T1/T2 difference in various fluids. However, T1/T2 value is inadequate for petrophysical characterization due to the similar T1/T2 value of different hydrogen types in shales. A brand-new characteristic parameter, T1/T2 variation during a solvent extraction experiment, is proposed for the characterization of shale petrophysical properties. The theoretical ranges of T1/T2 variation for different hydrogen components were determined from the type and content changes of hydrogen during extraction based on surface relaxation model. Joint experiments of multi-step solvent extraction and NMR T1-T2 were designed to validate the theoretical results. Both theoretical and experimental results show that the heterogeneity of shale is responsible for the different hydrogen components with a similar T1/T2 value. The results of joint experiment (1) show that the T1/T2 variation ranges for different hydrogen components are different, and (2) indicate that T1/T2 variations can be used to quantitatively evaluate the hydrogen type and saturation. The experimentally determined ranges and patterns of T1/T2 variation are consistent with the theoretical results. The quantitative relationship between T1/T2 variation and saturation, mobility, or wettability was further determined based on the theoretical variation of correlation time. Finally, a new interpretation scheme was established for the quantitative evaluation of wettability and fluid properties based on T1/T2 variations.

A Preliminary Study of Cobalt Solvent Extraction from Nickel Sulphate Solution using Organic Extractant-PC-88A

In present study, a solvent extraction experiment has been done to separate cobalt from the nickel sulfate solution by using 2-ethythexyl phosponic acid mono-2-ethylhexyl ester (PC-88A) as extractant. The experiment was carried out on a laboratory scale by using a separating funnel to extract cobalt from the nickel sulfate solution with PC88A. The mixed solution was shake in separating funnel for a specified period of time, and after the solvent extraction experiment was finished the organic phase PC88 was separated from the nickel sulfate solution by decantation. The nickel and cobalt content in the aqueous nickel sulfate solution were then analyzed using Atomic absorption spectrophotometry (AAS). In this experiment, the variable for experiments were covering solution pH from 2 to 6, shaking time from 30 minutes to 120 minutes, shaking speed from 20 revolutions per minute (rpm) to 80 rpm, and the volumeratio of aqueous to organic phase (A:O ratio) was from 1:1 to 1:4. The effects that experimental variables to the cobalt extraction were observed in this experiment. The result of experiment at room temperature, solution pH 5, shaking speed 60 rpm, shaking time 90 minutes, A:O ratio 1:4 and concentration of PC- 88A 40% show 97.21% of cobalt can be extracted by PC-88A from nickel sulfate solution, thererfore it was necessary to conduct two stage extraction process to extract 100% of the cobalt from the nickel sulfate solution.

Synergistic Extraction of Ga(III) from Chloride Solution by Mixture of Cyanex 272 and Alamine 336

Aming to select a suitable system for the synergistic solvent extraction of Ga(III), solvent extraction (SX) experiments were carried out by using acidic organo-phosphorous extractants, namely P204, P507 and Cyanex 272, and their mixtures with neutral extractants (TBP, N503) or amine extractants (Alamine 336). Among the studied mixtures, a remarkable synergistic effect for Ga(III) extraction was resulted by the combination of Cyanex 272 and Alamine 336 and the maximal synergistic enhancement coefficient reached 3.11. Compared to the single Cyanex 272, higher equilibrium pH values were observed when mixture of Cyanex 272 and Alamine 336 was employed. The extraction of hydrogen ions by Alamine 336 during the reaction was considered to be responsible for the synergistic extraction, and thus the the extraction of Ga(III) by Cyanex 272 was promoted. Finally, the synergistic extraction stoichiometry of mixture of Cyanex 272 and Alamine 336 for Ga(III) was projected by slope analysis. Ga(OH)A2 was resulted to be the composition of extracted complexes.

Recovery of Nickel and Cobalt Metal Powders from the Leaching Solution of Spent Lithium-Ion Battery by Solvent Extraction and Chemical Reduction

ABSTRACT Spent lithium-ion batteries (LIBs) contain some valuable metals. Smelting reduction of spent LIBs produces metallic alloys containing Co, Cu, Fe, Mn, and Ni. Leaching of the metallic alloys with inorganic acid solutions and subsequent separation of Cu(II), Fe(III) and Mn(II) results in a solution containing Co(II) and Ni(II). In this work, solvent extraction and chemical reduction experiments were performed to recover pure metals from this solution. Cobalt(II) was first separated from Ni(II) by solvent extraction with saponified Cyanex 272. Batch simulation experiments based on the McCabe-Thiele diagram for the extraction of Co(II) verified the complete separation of Co(II) from Ni(II). Hydrazine was then employed as a reducing agent for Co(II) and Ni(II) from the stripping solution and the raffinate, respectively. The effect of several variables on the reduction such as the molar ratio of hydrazine to metal ion, reaction time, temperature, and solution pH was investigated. It was found that the reduced metals could be dissolved owing to the oxidizing action of hydrazonium in acidic solution. Addition of NH4Cl was effective in suppressing the dissolution of the reduced metals. Especially, there was an optimum molar ratio of NH4Cl at which maximum reduction of Co(II) was obtained. The recovery percentages of Co and Ni powder were higher than 99.1% and 99.9%, respectively, and the purity of the reduced metals was higher than 99.9%.

The performance evaluation of Alamine336 in solvent extraction and polymer inclusion membrane methods for valuable ions extraction: A case study of Te(IV) separation intensification

In this research, extraction of Te(IV) from chloride solution was studied using Alamine336 extractant. In the solvent extraction experiments, Response Surface Methodology was employed to evaluate the effect of operating parameters on the extraction and stripping of Te(IV). According to results, two models were proposed for Te(IV) extraction and stripping. The ANOVA study verified the ability of the presented models to predict the experimental results. under the optimum operating parameters (Alamine336 concentration of 0.03 mol L−1, feed solution acidity of 2.36 mol L−1, temperature of 25°C, initial Te(IV) concentration of 210 mg L−1 and stripping phase pH of 8.5), Te(IV) extraction and stripping efficiency were 99.05% and 79.32%, respectively.In the polymer inclusion membrane (PIM) experiments, maximum transport of Te(IV) ions (64.58%) was achieved for membrane containing 40 wt.% Alamine336, initial acid concentration of 4 mol L−1, and receiving phase pH of 8.5.Under the optimum conditions, the extraction of Te(IV) from anodic copper sludge leach solution was 62.16% and 55.56% using the SX and the PIM processes, respectively. However, the PIM method had a higher selectivity towards Te(IV) ions.

Indium extraction from nitrate medium using Cyphos ionic liquid 104 and its mathematical modeling.

The treatment and recovery of pollutants in aquatic system is one of the greatest challenges for environmentalists throughout the world. In this study, solvent extraction of indium using phosphonium ionic liquid (Cyphos IL 104) as an extractant and its mathematical model was proposed for prediction of In(III) ion transport across a FSSLM (flat-sheet-supported liquid membrane). Solvent extraction experiments on indium have been carried out under various experimental conditions in order to assert some fundamental parameters using mathematical analysis for mass transfer process. Diffusion is the process which facilitates metal ion transport across liquid membrane, indicating the applicability of Fick's law of diffusion in model formulation. The influence of different parameters like composition of diluent, feed acidity, and ligand concentration on In(III) ion transport rate has been reported. At different extractant concentrations, the modeling outputs and experimental indium extraction were observed to be in reasonably good agreement.

Comprehensive characterization of petrophysical properties in shale by solvent extraction experiments and 2D NMR

Shale oil is one of the important unconventional fossil fuels resources. Understanding the petrophysical properties of shale contributes to the exploration and clean production of shale oil resources. 1H nuclear magnetic resonance (NMR) is a potential technique that can provide for shale petrophysical properties. However, current NMR-based technique for shale petrophysical characterization, due to the complexity of shale, usually requires some auxiliary geochemical experiments. Since a multi-step solvent extraction (MSSE) experiment has a merit in separating hydrocarbons and water in shale, in this work, two-dimensional (2D) NMR measurements combined with MSSE experiments were proposed for the first time to study the petrophysical properties of shale. A mixture of dichloromethane and methanol in a ration of 9:1 was prepared as a solvent for the extraction. Sufficient natural air-drying time allows for the removal of dichloromethane while retaining methanol. The comprehensive experiments show that the signal change induced by residual methanol from T1/T2-T2 map, before and after extraction and natural air-drying, can be used to identify pore-fluid and evaluate the mobility of hydrocarbon. For insight into the essence of experimental phenomena, quasi-1D/2D translational diffusion model were employed to analyze the T1/T2 and T2 responses of pore fluids. Wettability characteristics and detailed hydrocarbon mobility of shale were obtained from the theoretical analyses based on the translational diffusion models and T1/T2-T2 map. Combined the experimental results with the theoretical analysis, a comprehensive interpretation scheme was established for shale based on the T1/T2-T2 map, including fluid identification, wettability evaluation, and hydrocarbon mobility characterization.

Separation and Complexation of Trivalent Actinides and Lanthanides by Two Novel Asymmetric N,O-Hybrid Pyridyl Ligands: A Combination of Phosphoryl and Triazinyl Groups.

Two novel asymmetric hard-soft combined ligands, diphenyl(6-(5,9,9-trimethyl-5,6,7,8-tetrahydro-5,8-methanobenzo-[1,2,4]triazin-3-yl)pyridin-2-yl)phosphine oxide (Ph2-MTP) and butylphenyl(6-(5,9,9-trimethyl-5,6,7,8-tetrahydro-5,8-methanobenzo-[1,2,4]triazin-3-yl)pyridin-2-yl)phosphine oxide (BuPh-MTP), were designed based on the combination of the nature of phosphoryl and triazinyl groups for the selective extraction of trivalent minor actinides from lanthanides. The synthesis of these two ligands and their solvent extraction and complexation behaviors with Am(III) and typical lanthanides were investigated using UV-vis and time-resolved fluorescence spectrophotometry, 1H/31P NMR spectrometry, single-crystal X-ray diffraction, and DFT calculation methods. Solvent extraction experiments showed that both the ligands had strong extraction ability and high selectivity toward Am(III) over Eu(III) from the highly acidic HNO3 solution. The separation factors (SFAm/Eu) of these two ligands ranged from 17 to 26, with the concentrations of HNO3 increasing from 1.0 to 4.0 M. Slope analysis showed that the 3:1 ligand/metal complex was the prevailing species formed during extraction. The formation of the 3:1 ratio of the species of these two ligands with lanthanides was also identified by UV-vis spectrophotometry and single crystallography methods. The stability constants for the formation of the 1:3 complexes of Ph2-MTP and BuPh-MTP with Nd(III) were determined as 7.06 ± 0.015 and 6.67 ± 0.007, respectively. The geometric structures of the 1:3 complexes were clearly illustrated using the single-crystal X-ray diffraction technique and DFT theoretical calculation. This work provides an effective strategy to design new asymmetric hard-soft mixed actinide extractants by combining two different functional groups in one ligand, and the interaction mechanism between the functional groups and metal ions needs to be further investigated.

Selective Extraction of Cu(II) from the Hydrochloric Acid Leaching Solution of Spent Lithium-Ion Batteries by a Mixture of Aliquat 336 and LIX 63

The smelting reduction of spent LIBs produces metallic alloys containing Co, Cu, Fe, Mn, and Ni. These metallic alloys can be completely dissolved by 2 M HCl solution containing H2O2 as an oxidizing agent. Extraction of the leaching solution with D2EHPA results in a Fe(III) free raffinate. In this work, solvent extraction experiments were performed with a mixture of Aliquat 336 and LIX 63 to separate Cu(II) from the Fe(III) free raffinate. This mixture showed selectivity for Cu(II) over Co(II), Mn(II), Ni(II), and Si(IV). The mixture of 0.3 M Aliquat 336 and 0.2 M LIX 63 had the highest synergistic coefficient for the extraction of Cu(II) from the solution. The Cu(II) in the loaded mixture was easily stripped by weak sulfuric acid solution, which facilitates the recovery of copper sulfate from the stripping solution. McCabe-Thiele diagrams for the extraction of Cu(II) by the mixture and for the stripping with sulfuric acid solution were constructed. Three stages of counter-current extraction and stripping experiments verified that only Cu(II) was completely extracted, and the purity of Cu(II) in the stripping solution was higher than 99.9%. Considering the selectivity and easy stripping of Cu(II) from the loaded organic, this mixture can be employed in real operation for the recovery of valuable metals from the leaching solutions of spent LIBs.

Separation of cobalt and nickel via solvent extraction with Cyanex-272: Batch experiments and comparison of mixer-settlers and an agitated column as contactors for continuous counter-current extraction

The separation of cobalt and nickel was carried out via solvent extraction using the commercial extractant bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex-272). Solvent extraction experiments were performed on a batch scale to optimize the extractant concentration, saponification degree, equilibration time, organic-to-aqueous phase ratio (O/A), and stripping conditions. High selectivity of cobalt over nickel was obtained at an extractant concentration as low as 0.2 M (or 20% v/v), with a saponification degree of 40% and a phase ratio O/A of 1/1. Furthermore, eleven diluents, covering different aliphatic– aromatic compositions were tested to evaluate their effect on the separation of cobalt and nickel. Cobalt extraction efficiencies were not significantly impacted by the nature of the diluent. However, the co-extraction of nickel was approximatively 10% higher when toluene was used as a diluent in comparison with the aliphatic diluent Shell GS270. The process was validated in continuous mode using a battery of mixer-settlers and an agitated Kühni column. High recovery of cobalt and negligible co-extraction of nickel were achieved in both cases. The specificities, advantages, and challenges of the operation of both types of liquid-liquid extraction equipment were further discussed.

Separation of vanadium and iron from the steelmaking slag convertor using Aliquat 336 and D2EHPA: Effect of the aqueous species and the extractant type

• For efficient separation of V and Fe, transformation of ferric to ferrous was found essential. • V +4 and V +5 species were both extracted through cation exchange reactions. • Through anion exchange reactions, only V +5 species were extracted. • Proper aqueous species of V/Fe were prepared prior to SX, through leaching and cementation operations. • Flow diagram of vanadium recovery from convertor slag was proposed. In this study, a selective process for separation of vanadium and iron from the steelmaking slag was proposed. The proposed process has a potential to be considered industrially due to its relative simplicity. The process for the separation of vanadium and iron is consisted of three main stages: leaching, cementation, and solvent extraction. The leaching and cementation stage, were designed such that the proper aqueous species of vanadium and iron for the solvent extraction stage got generated. In the solvent extraction experiments, the effect of vanadium and iron aqueous species and the extractant type (extraction through anion and cation exchange reactions) on the separation of these elements were studied. In the solvent extraction stage, D2EHPA (cationic exchange) and Aliquat 336 (anionic exchange) were used. The results, for both extractants, showed that for selective separation of vanadium and iron, conversion of ferric to ferrous is essential. By converting ferrous to ferric ion, almost no iron was extracted through the anion exchange. Through cation exchange, however, ferrous extraction was started at significantly higher pH values comparing to ferric ion. D2EHPA was shown to have the ability to extract vanadium with both oxidation states of +4 and +5. Aliquat 336, however, showed no extraction toward V +4 , and only extracted V +5 species. This was found due to the absence of anionic complexes of V +4 in a sulfuric acid solution. The extraction mechanism of vanadium through both anion and cation exchange reactions were studied. The results showed the formation of VO 2 R(RH) through cationic extraction and VO 2 SO 4 R 4 N for the anionic extraction. Finally, 90% vanadium stripping efficiency from D2EHPA and Aliquat 336 loaded organics were obtained using 2 M H 2 SO 4 and 3 M HCl solutions, respectively.

A fundamental study on selective extraction of Li+ with dibenzo-14-crown-4 ether: Toward new technology development for lithium recovery from brines

The present study has proposed a selective Li+ extraction process using a novel extractant of dibenzo-14-crown-4 ether functionalized with an alkyl C16 chain (DB14C4–C16) synthesized based on the ion imprinting technology (IIT). Theoretical analysis of the possible complexes formed by DB14C4–C16 with Li+ and the competing ions of Na+, K+, Ca2+ and Mg2+ was performed through density functional theory (DFT) modeling. The Gibbs free energy change of the complexes of metal ions with DB14C4–C16 and water molecules were calculated to be −125.81 and −166.01 kJ/mol for lithium, −55.73 and −117.77 kJ/mol for sodium, and −196.02 and −291.52 kJ/mol for magnesium, respectively. Furthermore, the solvent extraction experiments were carried out in both single Li+ and multi-ions containing solutions, and the results delivered a good selectivity of DB14C4–C16 towards Li+ over the competing ions, showing separation coefficients of 68.09 for Ca2+-Li+, 24.53 for K+-Li+, 16.32 for Na+-Li+, and 3.99 for Mg2+-Li+ under the optimal conditions. The experimental results are generally in agreement with the theoretical calculations.

Pyridine diglycolamide: A novel ligand for plutonium extraction from nitric acid medium

A novel ligand N, N, N’, N’ tetra-isobutyl pyridine diglycolamide (PDGA) was synthesized and tested for extraction of actinides and fission products present in high level liquid waste (HLLW). The ligand was studied in presence of two different diluents- nitrobenzene (NB), a molecular diluent and 3-methyl-1-octyl immidazolium bis[(trifluoromethyl)sulfonyl] imide, an Ionic Liquid (IL). Unusual selectivity towards tetravalent plutonium over minor actinides and alkali & alkaline metal ions present in nuclear waste was showed by PDGA in presence of NB as diluent. The trend in kinetics of extraction as well as dependency of DPu(IV) values with nitric acid concentration was found to be different for two diluents studied. Mechanism of extraction was also varied for the two diluents studied. It followed solvation mechanism for NB whereas for IL it was a combination of solvation and ion-exchange mechanism. The calculated Gibbs free energy of extraction, ΔGext for Pu(IV) using density functional theory was found to be higher than that of other competitive metal ions corroborating the results from solvent extraction experiment. Further, ΔGext was found to be highly negative for metal and ionic liquid cations thus complimenting the experimental findings of ion exchange mechanism for a metal cation with cation of the ionic liquid.

Pyridine-di-phosphonates as chelators for trivalent f-elements: kinetics, thermodynamic and interfacial study of Am(III)/Eu(III) solvent extraction.

The fractionation of high-level radioactive waste from nuclear power plants simplifies the handling of its components, and facilitates the reduction of radiotoxic effects on the environment. The search and study of new ligands for solvent extraction, as one of the methods in fractionation, remains a complex and important research task. In this work, four pyridine diphosphonate ligands were synthesized. These ligands are part of the class of the N,O-donor extractants, which are selective towards Am(III). The separation factor SF(Am/Eu) for the best extractant reached values up to 10. The influence of the substituents on the efficiency of extraction and complexation of trivalent f-elements, the kinetics of extraction, and the behavior of the ligand at the interface were described. The effect of nitric acid concentration on the extraction was shown. The stoichiometry of the complexes was determined by slope analysis in solvent extraction experiment and verified by spectrophotometric titration in acetonitrile. Liquid tension experiments with a pendant drop method revealed the interfacial properties of the ligands in "F-3 solvent/H2O" and "F-3 solvent/HNO3" systems. The relationship between the surface activity and the ligand structure was shown. Studies of the extraction kinetics were performed in a modified Lewis cell. The effect of the ligand structure on the extraction rate was shown. The DFT calculation with the B3LYP density functional was used to explain the extraction properties of the ligands, including selectivity. The calculation of the pre-organization energy of the ligands explained the kinetics and extraction patterns for the studied series.