A new synthetically available resin SIR-SiO2@L was obtained by impregnating hydrophobic silica gel (SiO2@) with 2-(diphenylphosphoryl)-N,N-dioctylacetamide (L). The synthesis of L was carried out using an improved method. The hydrophobic material SiO2@ was first characterized using IR spectroscopy and thermogravimetric method, and its hydrophobicity was proven by IR spectroscopy and by determining of contact angle. For the first time, the interaction features of the SIR-SiO2@L resin with Nd(NO3)3 were studied using IR spectroscopy. The sorption characteristics of the SIR-SiO2@L towards Y, La, Nd, Pr, Sm, Ho, and Dy were studied using the extraction chromatography method. Using neodymium as an example, the sorption properties of SIR-SiO2@L were compared with those of known analogs. The possibility of separation of La/Y and Nd/Dy mixtures into individual components using SIR-SiO2@L from NH4NO3 solutions is shown.

The crystal structure of (2-methylpropane-1,2-diyl)bis(diphenylphosphine oxide) (L) has been determined for the first time. The complexes [UO2(NO3)2(L)]center dot CH3CN and [NpO2(NO3)2(L)] were isolated in crystalline form characterized by single-crystal X-ray diffraction, FTIR and electronic absorption spectroscopy. The [UO2(NO3)2(L)]center dot CH3CN complex was further characterized by PXRD and NMR methods. The complex of L with PuO22+ was characterized by FTIR and electronic absorption spectroscopy. The effect of introducing one or two methyl groups into the ethylene bridge on the spatial arrangement of the coordinating phosphoryl oxygen atoms in dioxides of ethylene diphosphines 1, 2 and L was investigated using quantum-chemical calculations in the framework of the electron density-functional theory (DFT). The synthesis of L has been conducted under thermal and microwave heating conditions.

2-Diphenylphosphoryl-4-nonylphenol, a lipophilic analogue of the well-known 2-diphenylphosphorylphenol, has been synthesized for the first time. Complex compounds with lithium, sodium, and potassium were obtained and studied by X-ray diffraction and IR spectroscopy for 2-diphenylphosphorylphenol. The extraction of Li, Na, and K with a solution of 2-diphenylphosphoryl-4-nonylphenol in methylisobutylketone was studied, and the compositions of the extracted complex compounds and the thermal effects of the extraction reactions were determined. The established lithium selectivity of the compound, characteristic of ortho-substituted phenols, allows lithium to be isolated from solutions with its low concentration in the presence of large amounts of sodium and potassium.

In this research the extraction chromatography method of separation the sum of rare earth elements (REE) from solutions obtained during the processing of E-wastes, followed by the recovery of individual Pr, Nd, and Dy using solvent impregnated resin (SIR) was developed. The offered method in comparison with the traditional ones has more advantages such as the higher selectivity, smaller material and power resources consumption, and the reduction of liquid wastes. N,N,N´,N´,-tetraoctyldiglycolamide was used as the stationary phase of SIR. The hyper crosslinked styrene-divinylbenzene copolymer was used as the inert carrier. SIRs were characterized by FTIR- spectroscopy. It has been established that the developed resin (SIR 3) significantly surpasses known analogue in terms of the efficiency of Nd recovery from solution of NH4NO3. The reason of this advantage was justified by the comparison of IR spectra of these resins. The features of the recovery and separation of Nd and Fe including the influence of extractant percentage, concentration of NH4NO3 in feed solution were studied by extraction chromatography method. Based on these results the effective method for the recovery of sum of REE from the magnet scarp, followed by separation of individual Pr, Nd, and Dy using SIR 3 was proposed. The technological scheme of developed method was suggested.

Dialkyl (5-ethyl-2-hydroxyphenyl)phosphonates are of O-donor ligands and have received considerable attention as a potential extractants for the selective extraction of lithium in the presence of large excesses of sodium and potassium ions. As part of the study of the relationship between the structure of the extractant and the ability to selectively bind lithium ions, the crystal structure of diethyl (5-ethyl-2-hydroxyphenyl)phosphonate HLEt was established by X-ray diffraction for the first time. HLEt coordination compounds with lithium, sodium, and potassium were synthesized for the first time; their composition and structure were established by elemental analysis, single-crystal X-ray diffraction analysis, and FTIR spectroscopy. Based on the obtained results, structural regularities of binding of dialkyl (5-ethyl-2-hydroxyphenyl)phosphonates with lithium, sodium and potassium cations were established for the first time. The ability of dialkyl (5-ethyl-2-hydroxyphenyl)phosphonates to form six-membered metallocycles with cations of alkali metals was confirmed.

The extraction of lanthanides(III) from aqueous nitric acid solutions with novel unsymmetrical diglycolamide extactant, N,N′-dimethyl-N,N′-dicyclohexyldiglycolamide (DMDCHDGA) into bis(trifluoromethylsulfoyl)imide-based ionic liquids (ILs), namely 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][Tf2N]), 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C8mim][Tf2N]), benzyltriethylammonium bis(trifluoromethylsulfonyl)imide ([N222Bn][Tf2N]) methyltrioctylammonium bis(trifluoromethylsulfonyl)imide ([N1888][Tf2N]), and their mixtures with molecular organic diluent 1,2-dichloroethane (DCE), is studied. DMDCHDGA has been shown to interact with components of the IL [C4mim][Tf2N]. The effect of HNO3 concentration in the aqueous phase on the extraction of Ln(III) ions is studied. The stoichiometry of the extracted complexes is determined, and the mechanism of Ln(III) extraction in a system with [C4mim][Tf2N] is discussed. It is shown that the efficiency and intragroup selectivity of the extraction of Ln(III) ions with DMDCHDGA into [C4mim][Tf2N] is significantly higher than when using its symmetric analog TODGA.

The effect of the ionic liquid, 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, on the extraction of lanthanides(III) from nitric acid solutions with phosphoryl-containing podands (2-(2-diphenylphosphoryl)-4-ethylphenoxy)methyl)diphenylphosphine oxide (1), (2-(2-diphenylphosphoryl)-4-ethylphenoxy)ethyl)diphenylphosphine oxide (2), and 2-[2-(diphenylphosphoryl)-4-ethylphenoxy]-N,N-dioctylacetamide (3) was studied. The stoichiometry of the extracted complexes was determined. The efficiency of extraction of lanthanides(III) with solutions of compounds 1–3 in dichloroethane from nitric acid solutions increases in the order 3 < 2 < 1. It has been established that, when replacing dichloroethane with an ionic liquid as a diluent, the extraction efficiency enhances. The magnitude of this effect decreases in the series of compounds 3 > 2 > 1. In the case of compound 1, the replacement of dichloroethane with an ionic liquid as a solvent is accompanied by a decrease in the extraction of lanthanides(III) at [HNO3] > 1.5 M.

Extraction of U(VI), Th(IV), REE(III), and Sc(III) from nitrate and perchlorate solutions with solutions of phosphorylpodand 1,5-bis[di( p -tolyl)phosphoryl]-3-oxapentane (L) in 1,2-dichloroethane depending on the concentration of acids in the aqueous phase was studied. The stoichiometry of the extractable complexes was determined. The magnitude of the “perchlorate” effect was shown to diminish upon an increase in the acid concentration, and REE(III) ions, to be extracted by podand L from HClO 4 solutions less efficiently than from HNO 3 solutions at acid concentrations above 0.3 M. During the extraction of Sc(III) the “perchlorate” effect also manifests itself in the region of high acid concentration, which leads to an increase in the separation factors of Sc(III) and REE(III), U(VI), and Th(IV) during extraction with podand L from HClO 4 solutions.

Composite resins impregnated by different organophosphorus extractants were developed and used for the extraction chromatography recovery of rare earth elements from nitrate-based leachate of NdFeB permanent magnets. The influence of different factors on recovery of Nd(III) and Fe(III), as the most difficult to separate elements, by developed resins was studied. The influence of extractant structure, the composition of feed solutions, and concentrations of HNO3 and NH4NO3 on the recovery of Fe(III) and Nd(III) by prepared resins were considered. The best recovery of Nd(III) was shown by resin impregnated with N,N-dioctyl (diphenylphosphoryl) acetamide. For this material, sorption characteristics (values of the distribution coefficient, capacity, and the Nd(III)/Fe(III) separation factor) were obtained, and the reproducibility of the loading–stripping process was evaluated. This resin and its precursors were characterized by IR spectroscopy. It was found that the developed resin is more efficient for Nd(III) recovery than resin impregnated with TODGA. An effective approach to the Nd(III)/Fe(III) separation with developed resin in nitrate solution was proposed. This approach was used for recovery of Pr(III), Nd(III), and Dy(III) from the nitrate-based leachate of NdFeB magnets by the developed resin. The final product contained 99.6% of rare earths.

Alkyl esters (C3-C8) of salicylic acid (HL) together with trioctylphosphine oxide (TOPO) were considered in order to find new lithium-selective extraction agents for liquid extraction. The hydrolytic stability of salicylic acid alkyl esters in lithium extraction processes from alkaline solutions was studied. Factors were found to reduce the hydrolysis of the extractant. Compositions of extractable alkali metals (Li, Na, K) complexes by a mixture of octyl ether of salicylic acid (HL8) with TOPO have been determined. The enthalpy values of the extraction reactions were calculated. Extraction isotherms were obtained and laboratory simulation of lithium extraction from alkaline multicomponent solutions using HL8-TOPO mixture as an extractant was performed.

The effect of the ionic liquid {trioctylammonium bis[(trifluoromethyl)sulfonyl]imide} on the extraction of REE(III) with tetraoctyldiglycolamide from nitric acid solutions has been studied. It has been found that efficiency and selectivity of the metal ions extraction from nitric acid solutions are significantly increased in the presence of the ionic liquid in the organic phase. The influence of the aqueous phase acidity on the change in the distribution ratios of REE(III) has been considered, and stoichiometry of the extracted complexes has been elucidated.

Eudialyte-group minerals are of scientific interest as important concentrators of rare elements (mainly Zr and REE) in agpaitic alkaline rocks and a potential source of REE, Zr, Hf, Nb, and Ta for industrial use. Extraction of uranium(VI), thorium(IV), zirconium(IV), hafnium(IV), titanium(IV), and scandium(III) by a binary extractant based on 1,5-bis[2-(hydroxyethoxyphosphoryl)-4-ethylphenoxy]-3-oxapentane and methyl trioctylammonium nitrate from eudialyte breakdown solutions is studied. Extraction isotherms were obtained and exhaustive extraction was investigated. It is shown that uranium, thorium, hafnium, zirconium, scandium, and titanium are almost completely recovered in two-stage extraction by a mixture of 1,5-bis[2-(hydroxyethoxyphosphoryl)-4-ethylphenoxy]-3-oxapentane and methyltrioctylammonium nitrate in 1,2-dichloroethane. Quantitative characteristics were compared for uranium(VI), thorium(IV), zirconium(IV), hafnium(IV), titanium(IV), and scandium(III). It was shown that the extraction efficiency of the metals by the binary extractant based on 1,5-bis[2-(hydroxyethoxyphosphoryl)-4-ethylphenoxy]-3-oxapentane and methyltrioctylammonium nitrate in 1,2-dichloroethane is much higher in comparison with the commercially available tributyl phosphate.

Extraction of microquantites of U(VI), Th(IV), and REE(III) from nitric acid solutions with solutions of (o-phenyleneoxymethylene)diphosphine dioxides with phenyl and butyl substituents at the phosphorus atom in the OCH2P(O)R-2 fragment was studied. The stoichiometry of the extracted complexes was determined. The influence of the extractant structure, the concentration of HNO3 in the aqueous phase, and the nature of the organic solvent on the extraction efficiency of REE(III), U(VI), and Th(IV) into the organic phase is considered. The presented data showed that the phosphoryl groups in the (o-phenyleneoxymethylene)diphosphine dioxide molecule are not equivalent. In contrast to the noticeable decrease in the efficiency of REE(III) extraction from nitric acid solutions when phenyl radicals are replaced by butyl radicals in the phosphoryl group P(O)R-2 directly attached to the phenylene ring, the replacement of the OCH2P(O)Ph-2 fragment in the dioxide molecule by OCH2P(O)Bu-2 only slightly reduces the REE(III) distribution factors in such media. At the same time, the extraction efficiency of U(VI) and Th(IV) from nitric acid solutions increases with this replacement.

1,3,5-Tris(2-diphenylphosphoryl-4-ethylphenoxymethyl)benzene (L′), a phosphorylcontaining tripodand, was synthesized for the first time in order to find extraction systems for efficient recovery of lanthanides. The main regularities of extraction of lanthanide(III) ions with mixtures of L′ and 4-benzoyl-5-methyl-2-phenyl-3-pyrazolone (HL) into CHCl3, 1,2-dichloroethane, toluene, and carbon tetrachloride from chloride solutions were elucidated. A significant synergistic effect, associated with the formation of hydrophobic mixed-ligand complexes of lanthanides(III), was found. The stoichiometry of the extracted complexes was determined by the equilibrium shift method. The equilibrium constants and values of the synergistic effect in the LnIII—L′—HL—dichloroethane system were calculated. The influence of the nature of the organic solvent and the composition of the aqueous phase on the efficiency of lanthanide(III) ion extraction into the organic phase was considered.

It was established that isopropyl salicylate can be used similarly to 1,3-diketones as a key component for a new efficient extraction system for selective separation of alkali metal cations. According to DFT modeling of complexes of isopropyl salicylate and 1,3-diketone with alkali metal cations (Li+, Na+, K+), six-membered metallacycles are formed whose stability decreases along the series Li > Na > K, which results in the observed enhanced affinity to lithium. The extraction ability of isopropyl salicylate is manifested in the presence of trioctylphosphine oxide (TOPO). The newly obtained complexes of isopropyl salicylate with alkali metal cations as well as their extracts in a mixture with TOPO are characterized by means of FT-IR, Raman, and NMR spectroscopy. The probable structure of the extracted lithium complex is presumed and the role of TOPO in the extraction process is investigated in detail. Extraction experiments showed extremely high separation coefficients for Li/Na and Li/K pairs in the extraction from a model multi-component solution.

The extraction of U(VI), Th(IV), Am(III), and lanthanide(III) ions and HNO3 from nitric acid solutions with 1,2-dichloroethane solutions of 3-oxapentane-1,5-diylbis(diphenylphosphine)dioxide and its structural analogues was studied. The stoichiometry of the extractable complexes was determined. The effects of the extractant structure and HNO3 concentration in the aqueous phase on the efficiency of the metal ions extraction into the organic phase were considered. The successive replacement of two methylene groups connecting the ether oxygen atom with Ph2P(O) groups in the podand molecule by o-phenylene groups leads to an increase in the efficiency of Th(IV) Am(III), and Ln(III) extraction from nitric acid solutions, but has little effect on the efficiency of U(VI) extraction.

Novel solvent-impregnated resins (SIRs) were prepared by treatment of styrene–divinylbenzene copolymer (LPS-500) with mixtures of the promising polydentante extractant (2-diphenylphosphoryl)-4-ethylphenoxy)methyl)diphenylphosphine oxide (L) and an ionic liquid [C4mim]+[Tf2N]−for the extraction chromatography recovery of Nd(III) from nitric acid solutions. It was shown that introduction of the ionic liquid into the SIR composition results in considerable enhancement of the Nd(III) recovery efficiency compared with resin impregnated only by L in slightly acidic media. The influence of the L: ionic liquid molar ratio in the SIRs composition, their percentages, concentration of metal and HNO3 in the eluent, and acid type on the value of synergistic effect and adsorption efficiency of Nd(III) recovery was studied. The SIR containing 40% of mixture of L and [C4mim]+[Tf2N]− with molar ratio 2:1 turned out to be the most efficient. The selectivity of Nd(III) separation from light and heavy rare-earth elements was studied and the optimal conditions of Nd(III) adsorption recovery and stripping by this SIR were chosen. It was found that in recovery efficiency of Nd(III) developed SIR exceeded the SIR containing Cyanex 923 (a mixture of monodentate trialkylphosphine oxides) and [C4mim]+[Tf2N]−.

New phosphonium ionic liquids, alkyldiphenylethylphosphoniumbis[(trifluoromethyl)sulfonyl]imides (Alk =C4H9,C8H17, andC12H25) have been synthesized.The effect of the obtained ionic liquids on the extraction of rare-earthelements(III) ions from nitric acid solutions of 2,2′-oxybis(N,N-dioctylacetamide) in 1,2-dichloroethane has been studied. Thestoichiometry of the extracted complexes has been determined, and the effect ofthe size of alkyl substituents in the ionic liquid molecule and theconcentration of HNO3 in the aqueous phase on theefficiency of extraction of metal ions into the organic phase has beenconsidered. The efficiency and selectivity of the extraction of ions ofrare-earth elements(III) is significantly increased in the presence of a ionicliquid in the organic phase.

With the aim to find new efficient extractants for recovery of f-block elements from processing wastes of different origin, we have compared a series of phosphoryl-containing podands, including (2-(diphenylphosphorylmethoxy)phenyl)diphenylphosphine oxide 1 and its analogues 5–7, where the ArP(O)Ph2 group of phosphine oxide type is replaced by phosphonic fragments. Quantum-chemical modelling of the structures of phosphoryl-containing podands 1 and 5–7 has been performed, which was later confirmed by the data of X-ray diffraction. The features of extraction of nitric acid, as well as U(VI), Th(IV), Nd(III), and Ho(III) with compounds 1 and 5–7 from nitric acid media into 1,2-dichloroethane have been studied. The compositions of extracted complexes have been determined.

ABSTRACT In this work we demonstrated, that machine learning opens a way for real design of ligands with required metal ion selectivity. We performed the ensemble QSPR modelling of the Li+/Na+ complexation selectivity and the stability constants for the Li+L and Na+L complexes of phosphoryl podands in nonaqueous solvent THF/СНCl3 (4:1 v/v). The models were built and cross-validated using MLR with the ISIDA QSPR program and SVM with the libSVM package. The program SVMsmf was implemented to fulfil an ensemble modelling using libSVM and the Substructural Molecular Fragments (SMF) descriptors. SMF were used as descriptors for the ensemble modelling, properties predictions by consensus models and design of combinatorial library of new ligands. SMF such as the P=O group, the ether and P=O groups bound through the aromatic ring contribute significantly to the Li+/Na+ selectivity. The developed models were applied for the prediction of the studied properties for a focused virtual library of 3057 phosphoryl podands generated using SMF contributions promising for selective binding of lithium. Consensus models selected hits for a synthesis by combinatorial library screening. Among the constructed selective ligands – hits, three new podands were synthesized, for which the experimentally estimated selectivity is in satisfactory agreement with that predicted.