ABSTRACT Pertraction of Np(IV) across a PTFE membrane containing two different aza-crown ether-based multiple diglycolamide (DGA) ligands termed as LI (3 DGA arms) or LII (4 DGA arms) was investigated using nitric acid as feed solution. A few of the studies were also carried out with Pu(IV) for comparison purposes. The kinetics of the extraction of Np(IV) and Pu(IV) was fast at 3 M HNO3 and within 10 min reaches the equilibrium distribution (D) ratio with both ligands. However, the stripping kinetics was slower especially with ligand LII. The extraction and transport studies were carried out using 1.0 × 10−3 M ligand solution in 95% n-dodecane + 5% isodecanol. The transport rates were slower with ligand LII than with LI at higher nitric acid concentrations (>1 M HNO3) and the transport rates decreased with nitric acid concentration with both ligands. The effective diffusion coefficients (Deff) of Np(IV) were estimated using the lag-time method as 6.2 × 10−8 cm2 s−1 (LI) and 4.6 × 10−8 cm2 s−1 (LII). The stability data suggest that the LI containing supported liquid membrane (SLM) is comparatively more stable than that of LII and the transport flux remains the same up to nine days of operation in case of ligand LI.

ABSTRACTEURO-GANEX is an innovative hydrometallurgical process for the group separation of transuranic actinides from future spent nuclear fuels. A flowsheet test of a process upset (or ‘maloperation’) has been carried out involving the reduction in the concentration of the scrub acid feed to the extract-scrub contactors. The experimental test was completed in two stages. First, the extract-scrub contactors were run under normal flowsheet conditions before initiating the process upset by reducing the scrub acidity from 0.5 to 0.05 mol/L HNO3. At low acidity, a change in the online UV-Vis spectra of the solvent phase indicated the formation of hydrolyzed plutonium species or plutonium colloid formation. Surprisingly, however, this did not lead to the recycle and accumulation of plutonium in the extract-scrub contactors as expected indicating that the EURO-GANEX process is quite robust towards this process upset. Further spectroscopic investigations of the organic-phase species were also performed to characterize the conditions under which the hydrolyzed plutonium species form in the EURO-GANEX solvent as well as separate TODGA and DMDOHEMA phases. The spectroscopic studies supported the view that Pu(IV) hydrolyses at low acidity but the hydrolysis is limited by the organic ligands and is consequently reversible on raising the acidity again. The hydrolysis was also observed in separate TODGA and DMDOHEMA phases.

ABSTRACTSolvent extraction plays a vital role in manufacturing high purity alkaloids from natural poppies. Cyanex® 923, which has been widely used in hydrometallurgical processes, is shown to be an effective extractant for natural alkaloid extraction. In this work, 0.2 M Cyanex® 923 in xylene (dispersed phase) was used to investigate the equilibrium isotherm of morphine at pH 9 and morphine extraction in two different reciprocating Karr columns. Two sources of morphine solution (continuous phase), including technical morphine with few impurities and industrial upstream morphine rich extract containing more impurities and other alkaloids, were studied to investigate morphine mass transfer efficiencies in the Karr columns based on different dispersed phase velocities and reciprocating frequencies. The mass transfer coefficients of technical morphine solution were calculated using a backflow model associated with axial dispersion, and the mass transfer coefficients were further used to regress a mass transfer correlation. The regressed correlation was further validated, and the process model was shown to be reliable to predict the extraction efficiency, and outlet morphine concentration of both aqueous phase and organic phase. This work provides insights to scale-up the process design in a short time, bridging the gap between bench scale research and pilot industry scale testing using a simple correlation method.

ABSTRACTThe study investigated the behavior of two amines, Trioctylamine (TOA) and Tris(2-Ethylhexyl) amine (TEHA), in the sulfuric acid extraction system, with varying concentrations of extractants and modifiers, as well as the temperature of the sulfuric acid extraction. The study found that TOA had a higher ability in the extraction of sulfuric acid and was less dependent on temperature. However, an increase in the initial sulfuric acid concentration resulted in a drop in acid extraction percentage when TOA was employed, while such a drop was not observed in the case of TEHA. The study also illustrated the necessity of using Octanol as a modifier, with different minimum levels required for TOA and TEHA. Additionally, Octanol showed a positive effect on the extraction level of sulfuric acid in the TEHA – H2SO4 extraction system, which can be considered an advantage in the facile stripping of the loaded organic phase. The slope analysis method revealed that more than 1 mol of TOA is necessary to extract 1 mol of sulfuric acid, while 1 mol of TEHA can absorb 2 mol of sulfuric acid. FTIR spectra analysis confirmed TOA's participation in the extraction of sulfuric acid and provided insights into the chemical bonds formed. Overall, the study provides a comprehensive understanding of the solvent extraction of sulfuric acid and can be useful in optimizing the extraction process for industrial applications.

ABSTRACTA selective extraction process for recovering vanadium (IV) over chromium was proposed with use of a mixed extractant consisting of di(2-ethylhexyl) phosphate (D2EHPA) and tri-n-butyl phosphate (TBP). The influence of various factors, which included the initial aqueous pH value, the concentration of leach solution and D2EHPA, phase ratio (O/A), extraction equilibrium time and extraction temperature in the extraction process on the separation of V and Cr was investigated. Under the condition of the optimum extraction, vanadium extraction was above 94.0%. Meanwhile, under the optimum stripping conditions, the vanadium stripping was above 93.0% utilizing 1.5 mol/L sulfuric acid as the effective stripping reagent. The regeneration and reusability of the loaded organic phases after stripping were discussed. In addition, continuous three-stage extraction and stripping strategy indicated that the aggregate loss of vanadium was 0.885% and that the purity of vanadium was more than 99.9%. Under the condition of the optimum precipitation, when the pH value of the stripping solution was adjusted to 7.0 with ammonia water, the precipitation efficiency reached 99.93%. The calcination conditions (above 680 °C in air) were finally determined by TG-DTA and TG-MS experiments, and the V2O5 obtained by calcination was characterized by XRD. Additionally, a method for detecting impurity elements in vanadium matrix without interference was established. The recovery technology has practical significance in enlarging production scale, reducing specific energy consumption and cost, and realizing automatic control in vanadium leaching process.

ABSTRACTThe extraction of Am3+ and Eu3+ with 6,6’-bis(5-alkyl-1H-pyrazol-3-yl)-2,2’-bipyridine (BPzBPy, alkyl = i-Bu, n-Bu, n-Oct) from HNO3 medium and the complexation of BPzBPy with Eu3+ were investigated. By using meta-nitrobenzotrifluoride (F-3) as a diluent, iBu-BPzBPy ligand in combination with 2-bromohexanoic acid was able to extract Am3+ over Eu3+ with the nature of significantly high efficiency, relatively fast extraction kinetics, and easy stripping. Slope analysis showed the formation of a 1:2 metal/ligand extraction species. The analyses of electrospray ionization mass spectrometry (ESI-MS), Fourier transform infrared (FT-IR) and time-resolved laser fluorescence spectrum (TRLFS) revealed that the composition of the extracted complex was [Eu(H2O)L2]A3 (L = ligand; HA = 2-bromohexanoic acid). The complexation of iBu-BPzBPy ligand with Eu3+ was an enthalpy-driven spontaneous, exothermic, and entropy-decreasing process. Besides, the complex stability constants were also obtained via UV–vis spectrophotometric titration. Combining the results of solvent extraction and complexation studies, a cation exchange extraction model was also proposed.

ABSTRACTThe extraction of Nd(III), Eu(III), Am(III), and Cm(III), trivalent lanthanides and actinides in high level nuclear waste, by the extractant N,N-di(2-ethylhexyl)-thio-diglycolamic acid (HDEHSDGA, HA) is investigated via thermochemical and spectroscopic methods. In this study, HDEHSDGA behaves as a conventional mono-basic cation-exchanging ligand extracting Ln(III) and An(III) from nitrate solutions of pH region. The information obtained from the extraction experiments and the spectroscopic analyses indicate that the primary extracted complex species may be MA3 · 2H2O for these four cations and likely for the other trivalent f-elements. In the extracted complexes, the anionic monomer extractant A− coordinates to the metal ions presumably forming bidentate coordination via the carbonyl oxygen atom and one of the oxygen atoms of the carboxylate; it appears that the thio-ether does not directly participate in the complexation reaction. The results ultimately demonstrate that HDEHSDGA does not exhibit significant selectivity for An(III) over Ln(III), in contrast to results reported in a previous study conducted with unpurified extractant.

ABSTRACTThis article describes several extraction chromatographic materials aiming to offer improved potential for isolating trace elements with high charge/ionic radius ratio from accompanying matrix elements in natural samples. Starting with commercially available, field-proven, TRU- and RE-Spec materials (Eichrom Technologies), three resins containing less TBP in the CMPO-TBP mixtures, or even neat CMPO only, have been prepared and characterized through measurement of the distribution ratios of some fifty elements in HNO3 and HCl media of variable strength. These resins were further evaluated for analytical applications on geochemical samples. The results highlight a strong enhancement of weight distribution ratios of many elements of interest in geochemistry, cosmochemistry, and environmental sciences (Lanthanides, naturally occurring Actinides, High Field Strength Elements). Combined with good chromatographic characteristics, these high Dw’s make it possible to achieve excellent group separations by using very small columns operated at relatively high, gravity-driven flow rate. Moreover, in an attempt to further improve the selectivity against Fe(III) and Ti(IV), preliminary investigations were made on an additional pair of resin prototypes impregnated with a CMPO-substituted calixarene. Although promising distribution ratio data were obtained, these prototypes did not permit to prepare columns with satisfactory chromatographic characteristics, and this approach still waits for a better impregnation methodof the porous inert support.

ABSTRACTCrystalline silicotitanate (CST) ion exchanger is currently used to remove cesium (137Cs) from the aqueous phase of Hanford tank wastes in preparation for vitrification at the Waste Treatment and Immobilization Plant (WTP). The CST is a non-elutable inorganic ion exchanger targeted to maintain a decontamination factor of ≥1,000 prior to the column effluent reaching a waste acceptance criterion. In an effort to reduce costs generated by ion exchange processing, system optimization of the waste treatment has been conducted. Decreasing the tank waste supernate sodium molarity prior to processing through the ion exchange columns showed that it can significantly reduce the number of columns used while maintaining the necessary sodium throughput. Optimization of this process can result in significant cost savings and ultimately result in less waste production.

ABSTRACTIn this work, solvent extraction of In(III) from sulfate solutions by using mixtures of D2EHPA with octyl alcohol and octanoic acid was investigated. The introduction of the additives into the organic phase was shown to lead to an antagonistic effect thus facilitating efficient indium stripping from the loaded organic phase. The antagonistic effect is significantly higher in the D2EHPA (HR) and octyl alcohol (HA) mixtures. The formation of stable associates between D2EHPA and HA leads to a decrease in the extraction efficiency of indium. In the presence of alcohol, almost complete stripping of indium from a D2EHPA loaded phase can be achieved to produce a strip liquor containing>33.0 g/L In. Based on the analysis of the extraction data and by using nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy of the organic phases, it was concluded that indium extraction with D2EHPA in octyl alcohol is due to the formation of the extracted compound InR3. The equilibrium constant (logK) for indium extraction with solutions of D2EHPA in octyl alcohol was found to be − 0.12 ± 0.05. Extraction systems containing D2EHPA and octyl alcohol can be used to recover indium from various industrial solutions, in particular from the solutions derived from lead-zinc production and from liquid crystal display panel wastes.

ABSTRACTPhycobiliprotein (PB), which is produced by cyanobacteria, has potential applications as a valuable pharmaceutical product. In this study, PB was separated by using a nonwoven-fabric membrane (Rx-1) that contained quaternary amino groups. PB was extracted from a Nostoc commune, which is a type of microalga, by disrupting the cell walls by a freeze–thaw method. Two types of biomolecules, namely PB and other biomolecules X, were identified by gel permeation chromatography. Permeation of the PB-containing solution through Rx-1 increased the purity of the PB in the filtrate from 0.25 to 0.45. The adsorption constant (Kp) and maximum adsorbed amount of each protein on Rx-1 (qmax) were determined by fitting the experimental data to a mathematical model. The obtained values for Kp and qmax were used to simulate scaled-up treatment of a PB-containing solution. Permeation of a PB-containing solution (3.0 L at 1.2 × 10−3 m3/h) through Rx-1 (volume of scale-up membrane, 8.0 × 10−4 m3) enabled PB separation for 26 h. Further PB purification could be achieved by using the Rx-1 membrane in combination with precipitation with ammonium sulfate solution and an ultrafiltration membrane.

ABSTRACTSulfadiazine Schiff base (SDSB) was prepared using an inexpensive technique by modification of sulfadiazine drug (SD) to be used as an adsorbent material for recovery of Y(III) ions from aqueous solutions. Chemical and physical characterizations of SDSB were performed using different techniques. The maximum static adsorption capacity of the modified SD was 0.9 mmolg−1 for Y(III) ions and at pH 5.0. The kinetics results revealed that the sorption of Y(III) ions upon the synthesized SDSB followed the pseudo-second-order with R2 of >0.999. Temkin, Dubinin – Radushkevich, Freundlich, and Langmuir models accurately described the adsorption isotherm data. The activation energy (Ea) for adsorption was 17.52 kJmol−1, indicating the process is to be chemisorption. Thermodynamic characteristics with ΔHo of 11.33 kJmol−1 and a ΔSo 110.2 Jmol−1K−1. Using FT-IR and EDAX analysis proved the yttrium adsorption upon the SDSB. The desorption process for Y(III) ions was successfully achieved using 1 M HNO3 and it reduced from 95% to 70% after five consecutive cycles. A pre-concentration process for yttrium ions presented in a waste solution was achieved using SDSB adsorbent with a pre-concentration factor of about 10. As a result, it is regarded as a promising adsorbent for Y(III) ions in a variety of industrial applications.

ABSTRACTThe separation of trace hafnium from bulk tungsten alloys is of interest for isotope harvesting at the National Superconducting Cyclotron Laboratory and the Facility for Rare Ion Beams because 172Hf, the parent of 172Lu, accumulates in tungsten alloy beam blockers at these facilities. In this work, a procedure for the separation of trace hafnium from a bulk tungsten alloy (454 g) was established using tracer isotopes (175Hf, 88Zr, 173Lu, and 88Y). The procedure employed dissolution in an HF–HNO3 solution followed by a calcium fluoride precipitation, and then extraction chromatography was used for more selective separation steps. Two stages of column separations using LN resin (HDEHP based) and TRU resin (CMPO based) were performed. Gamma-ray spectroscopy and mass spectrometry were used to analyze the final hafnium sample and follow the steps in the chemical processing. The final recovery of hafnium was high (90 ± 8)%, and the mass of tungsten and other transition metals was reduced to near background levels (as determined by ICP-MS of the blank acid solutions). Zirconium follows hafnium quantitatively in this procedure; there was no detectable 173Lu in the final hafnium sample.

ABSTRACTThe crown ether strontium extraction (CESE) process has been developed for the recovery or removal of Sr from acidic high-level liquid waste (HLLW) in China, where the extractant is 4’,4”(5”)-di-(tert-butyldicyclohexano)-18-crown-6 (DtBuCH18C6) and the diluent is n-octanol. When the CESE process was operated in annular centrifugal extractors (ACEs) for demonstration by cold and hot tests, it was found that the outlet aqueous phases had organic-phase entrainment even though ACEs operated at a low rotor speed. For the successful operation of the CESE process in ACEs, effects of the operating and geometrical parameters on the liquid hold-up volume and phase ratio (aqueous phase/organic phase, A/O) of the HNO3–DtBuCH18C6/n-octanol system in a ϕ20 ACE were systematically investigated to find the cause of the above-mentioned hydrodynamic performance problem of the CESE process using the liquid-fast-separation method. It is shown that the operating and geometrical parameters have effects on the liquid hold-up volume and phase ratio (A/O). Moreover, the phase ratio (A/O) in the separation zone of the rotor is less than 1.5 under most of the present experimental conditions, which shows organic-phase entrainment may easily occur in the outlet aqueous phase. The cause can be that the density difference of two phases is small, viscosity of the organic phase is large, and interfacial tension of the extraction system is low.

ABSTRACTThe extraction performance and mechanism of 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]triazin-3-yl)-1,10-phenanthroline (CyMe4BTPhen) in the room temperature ionic liquid 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][NTf2]) have been studied and are herein reported. Americium is extracted from nitric acid solutions by cation exchange and is most efficient at low ( 3000 were achieved although decontamination factors for americium from more complex matrices were non-competitive with extraction using traditional molecular diluents. Modest improvements in decontamination factor were attained by the addition of the hydrophilic reagent N,N,N’,N’-tetraethyl diglycolamide (TEDGA).

ABSTRACTThe physicochemical parameters of tris(2-methylbutyl) phosphate (T2MBP), a molecule possessing the essential characteristics required to be considered as a promising extractant in the solvent extraction stage of fast reactor fuel reprocessing, have been evaluated in the present study. In this context, the density, viscosity and interfacial tension (IFT), which are considered to be few among the important solvent selection criteria prior to its deployment in the plant scale have been measured for T2MBP in n-dodecane (n-DD) based systems. Similar studies have been performed with its straight chain isomer, tri-n-amyl phosphate (TAP) as well as the widely utilized commercial extractant, tri-n-butyl phosphate (TBP) so as to emphasize on the structural effects. Though the trends on the physicochemical behaviour of TBP based systems (temperature and ligand concentration effects) are well known in the literature, the data on TBP have been generated in the present work for comparison with the T2MBP results under similar experimental conditions. Solutions of trialkyl phosphates (TalP) in n-DD of different concentrations have been used to generate the data on the variation of density, IFT and viscosity with the change in the ligand concentration. In addition, the transformation in their properties has been assessed after subjecting the solvents to various levels of gamma absorbed doses. Overall, it has been observed that there was no significant variation in the density of the irradiated TalPs; however, there was a significant rise in the viscosity and reduction in the IFT of the TalP samples upon irradiation. The data on the Gibbs energy change of activation of various 1.1 M TalP/n-DD solutions have been generated by fitting their respective dynamic viscosity value as a function of temperature using Andrade’s equation. Moreover, from the IFT value, the parameters relating to the interfacial activity of TalP/n-DD solutions have been determined using the Szyszkowski adsorption isotherm.

ABSTRACTRemoval of Cs isotopes, one of the heat generators present in used fuel/reprocessing waste, is one of the most challenging obstacles in the disposal of these materials. For this purpose, a new silica-calix[4]crown material, CBisC6@SiO2, has been prepared. The material was created coupling a symmetric calixcrown derivative CBisC6 into the pores and channels of the SiO2-P particles through vacuum hybridization and immobilization. SEM, 29Si solid-state CP/MAS NMR, N2 adsorption-desorption isotherms, TGA-DSC and XPS were used to characterize the structure of the final material. The adsorption of Cs and some representative metals onto CBisC6@SiO2 has been investigated in the range of 0.4 to 6.0 M HNO3. CBisC6@SiO2 showed strong adsorption ability and selectivity for Cs over all of others except for Rb in 3.0 M HNO3. The adsorption mechanism of Cs was verified using XRD and FT-IR spectra. The separation of Cs from other waste materials by CBisC6@SiO2 was performed through six adsorption-desorption cycles. The removal efficiency of Cs was 99.5%, while other fission products were weakly absorbed except for Rb with the removal efficiency of 85.3%. A nearly quantitative removal of Cs by CBisC6@SiO2 was achieved.

ABSTRACTThe current study is a new method for liquid–liquid extraction of copper (II) and zinc that was carried out using an efficient solvent called trifluoroacetylacetone in a hollow fiber membrane contactor (HFMC). To analyze the extraction process and understand its underlying mechanisms, computational fluid dynamics (CFD) was employed. The extraction was performed in three domains by coupling the mass and momentum equation to express the solute transport from the tube side to the shell side through the membrane in a hollow fiber membrane contactor. The finite element approach simulates the governing equation and validates the results. This work aims to obtain the distribution of copper (II) and zinc by performing a simulation. The effect of some crucial parameters was investigated. The results illustrate that the extraction efficiency increases by increasing the partition coefficient and decreasing the flow rate on the tube side. Also, the temperature significantly affects extraction, and by enhancing the temperature from 298 to 313 K, the efficiency increases by 12% for copper (II) and 6.6% for zinc. Furthermore, the membrane porosity was found to be another influential parameter. By increasing the membrane porosity of 25% to 90%, the efficiency increases to 95% for copper (II) and 98% for zinc.

ABSTRACTIn this work, we studied the complex formation (1H, 31P NMR-titration, UV–vis titration, luminescent titration) and solvent extraction of lanthanides with pyridine diphosphonates. The stoichiometry of the complexes was determined: ML and ML2 forms are present. This is confirmed by all of the above methods. It was found that the pyridine ring and P=O groups are involved in the coordination of the metal cation. The coordination environment of the Eu(III) cation was studied more thoroughly using the EXAFS method in solution. Coordination numbers and distances were determined for the complex in solution. The influence of the lanthanide radius on the value of the stability constant was shown. The change in extraction efficiency in the series of lanthanide is described. A new pattern, unusual for other phosphorus-containing ligands, was obtained. To explain the change in the parameters of complexation depending on the system, DFT calculations were carried out. The effect of various initial states of the extracted cations was shown. The initial state with a large amount of nitrates corresponds to a two-phase system during extraction, and with a smaller amount, to a single-phase system with acetonitrile. Additionally, the luminescent properties of the complexes were described in detail as one more applied aspect of the work. .

(2022). Special Issue on Hierarchical Organization in Solvent Extraction. Solvent Extraction and Ion Exchange: Vol. 40, Special Issue on Hierarchical Organization in Solvent Extraction, pp. 1-5.