Separation Of Lanthanide Ions Research Articles

Selective Separation of Rare Earth Ions from Mine Wastewater Using Synthetic Hematite Nanoparticles from Natural Pyrite

The separation of rare earth ions (RE3+) from aqueous solutions poses a significant challenge due to their similar chemical and physical characteristics. This study presents a method for synthesizing hematite nanoparticles (Fe2O3 NPs) through the high-temperature phase transition of natural pyrite for adsorbing RE3+ from mine wastewater. The characteristics of Fe2O3 NPs were studied using XRD, SEM, BET, XPS, FTIR, and Zeta potential. The optimal condition for RE3+ adsorption by Fe2O3 NPs was determined to be at pH 6.0 with an adsorption time of 60 min. The maximum adsorption capacities of Fe2O3 NPs for La3+, Ce3+, Pr3+, Nd3+, Sm3+, Gd3+, Dy3+, and Y3+ were 12.80, 14.02, 14.67, 15.52, 17.66, 19.16, 19.94, and 11.82 mg·g−1, respectively. The experimental data fitted well with the Langmuir isotherm and pseudo-second-order models, suggesting that the adsorption process was dominated by monolayer chemisorption. Thermodynamic analysis revealed the endothermic nature of the adsorption process. At room temperature, the adsorption of RE3+ in most cases (La3+, Ce3+, Pr3+, Nd3+, Sm3+, and Y3+) onto Fe2O3 NPs was non-spontaneous, except for the adsorption of Gd3+ and Dy3+, which was spontaneous. The higher separation selectivity of Fe2O3 NPs for Gd3+ and Dy3+ was confirmed by the separation factor. Moreover, Fe2O3 NPs exhibited excellent stability, with an RE3+ removal efficiency exceeding 94.70% after five adsorption–desorption cycles, demonstrating its potential for the recovery of RE3+ from mine wastewater.

Construction of zwitterionic ion imprinted polymer brushes on mixed matrix membranes for the separation of rare earth ions

In this article, zwitterionic ion imprinted polymer brushes were constructed on mixed matrix membranes (MMMs) for the separation of rare earth ions. A multi-step chemical grafting strategy to anchor amino groups and double bonds sequentially on the oxygen-containing sites at the edge of GO nanosheets were established at first. After incorporating these modified GO nanosheets into MMMs, the imprinting process was constructed via in-situ free radical polymerization initiated by oxidize-reduction initiators on these double bond sites of GO nanosheets in the MMMs. [2-(methylacryloxy)ethyl] dimethyl-(3-propyl sulfonate) ammonium hydroxide was firstly applied as functional monomers to generate the zwitterionic polymer brushes on the GO-mixed matrix membranes, together with the aid of ligand bis (2,4,4-trimethylpentyl) phosphonic acid (Cyanex272) in the MMMs matrix. Benefiting from these specific designed imprinted sites, the imprinted membranes had the highest adsorption capacity for Y3+, which was nearly twice as much as that of Ho3+ and Er3+. The significant difference in adsorption capacity and permeation efficiency between imprinted and non-imprinted membranes proved this imprinting strategy realized valid Y3+ imprinting sites construction. The separation coefficients of Y3+/Ho3+ and Y3+/Er3+ calculated from permeation experiments were 2.16 and 2.77, which were much higher than those of MMMs and NIMs. Imprinted factor βr of Y3+/Ho3+ and Y3+/Er3+ were calculated as 2.63 and 1.97.

Essence into the kinetic enhanced extraction induced by Marangoni convection on the surface of freely rising oil droplets

The enhanced separation of rare earth ions depending on different kinetic extraction behaviors can be achieved by extraction on the surface of rising droplets, where exists the nonhomogeneous chemical reaction. Marangoni instability might occur dependent on nonhomogeneous chemical reaction, which is conducive to the enhancement of interfacial mass transfer. To explore the influence from a nonhomogeneous chemical reaction on the generation of Marangoni instability, influences from the flow rate of oil droplets and the oil droplet size on interfacial extraction behaviors were performed, the interfacial tension was evaluated, and MD simulations combined DFT calculations were adopted. It was revealed that the higher interface renewal rate of the large oil droplet was favorable for the interfacial chemical reaction. Whether the interfacial extraction rate is greater than the interface renewal rate decided the occurrence of Marangoni convection. The current research highlights a novel viewpoint towards understanding microscopic nature of kinetic enhanced extraction.

Role of natural deep eutectic solvents (NADESs) in coagulation bath for PVDF-based membranes on enhanced permeation and separation of rare earth ions

Efficient separation of single rare earth element such as neodymium (Nd) has become an important research topic due to the supply crisis which seriously restricts the application and promotion of rare earth permanent magnets. PVDF-based separation membranes prepared by non-solvent induced phase separation (NIPS) method usually exhibited hydrophobic surface properties resulting in performance attenuation and operation cost increase. This article applied an easily available NADES from betaine and lactic acid to regulate and control the coagulation bath of a polymer inclusion membrane (PIM) for the separation of Nd, Sm and Dy ions. Evidences for the formation of DES were characterized via 1H NMR and FT-IR, and betaine showed more obvious changes than lactic acid during the formation of DES via hydrogen bonds. With the help of DES, pores on the surface were much larger and richer, and the migration of PO and P–O groups to the lower epidermal layer of the membrane made the surface layer become more hydrophilic. DES accelerated the liquid-liquid demixing process and led to faster membrane-forming speed and typical finger-like macrovoids and short vertical penetration channels, which could be observed at high DES contents, and a DES content of 5 wt% was found the most optimal considering the overall permeability and separation performances. As an effective means to improve membrane's performances, adding hydrophilic NADESs at a proper ratio in the coagulation bath would be conducive to form more porous structures, higher surface hydrophilicity, optimized permeability and separation performances.

Separation of Rare-Earth Ions from Mine Wastewater Using B12S Nanoflakes as a Capacitive Deionization Electrode Material.

In this study, nanoflakes of B12S were fabricated by plasma-assisted reaction of sulfur dichloride in an ionic liquid at room temperature using europium boride as a hard template. The nanoflakes had an average width and thickness of about 3 1urn and 9.6 nm, respectively, and a large specific surface area of 1197.2 m² g 1. They behaved like typical electric double-layer capacitors with a capacitance of 201.2 F g 1 at 0.2 mA cm ² During capacitive deionization to recover rare-earth ions, the nanoflakes had higher adsorption selectivity for Sm3+ than for other competing ions present in real mine waste water. This is due to the strong interaction of the electron-concentered S-groups (S''') of the nanoflakes with S m3+. This provides an alternative to construct efficient systems to specifically remove Sm3+ from aqueous solution using B12S nanoflakes. This process demonstrates that other boron sulfide compounds can be used to recover valuable ions by capacitive deionization.

Antagonistic Role of Aqueous Complexation in the Solvent Extraction and Separation of Rare Earth Ions.

Solvent extraction is used widely for chemical separations and environmental remediation. Although the kinetics and efficiency of this process rely upon the formation of ion–extractant complexes, it has proven challenging to identify the location of ion–extractant complexation within the solution and its impact on the separation. Here, we use tensiometry and X-ray scattering to characterize the surface of aqueous solutions of lanthanide chlorides and the water-soluble extractant bis(2-ethylhexyl) phosphoric acid (HDEHP), in the absence of a coexisting organic solvent. These studies restrict ion–extractant interactions to the aqueous phase and its liquid–vapor interface, allowing us to explore the consequences that one or the other is the location of ion–extractant complexation. Unexpectedly, we find that light lanthanides preferentially occupy the liquid–vapor interface. This contradicts our expectation that heavy lanthanides should have a higher interfacial density since they are preferentially extracted by HDEHP in solvent extraction processes. These results reveal the antagonistic role played by ion–extractant complexation within the aqueous phase and clarify the advantages of complexation at the interface. Extractants in common use are often soluble in water, in addition to their organic phase solubility, and similar effects to those described here are expected to be relevant to a variety of separations processes.

Study on the interfacial behaviors for extraction of heavy rare earths with PC-88A: A new strategy of thin oil film extraction

The traditional organic solvent extraction for selective recovery of target components from low-concentration solutions bears many disadvantages such as high consumption of extractant, low enrichment ratio of target components and multiple extraction stages. To promote extraction and separation of rare earth ions at oil–water two phases interface, a new strategy of thin oil film extraction was suggested in present work for selective recovery of rare earth ions with extremely low concentrations in the leaching solution of ion-adsorption type rare earth ores. Experimental results revealed that the distribution ratio and extraction rate of rare earths can be adjusted by oil film thickness, flow rate of feed liquid, extractant concentration and saponification degree of 2-ethylhexyl phosphonic acid mono (2-ethylhexyl) ester (PC-88A). The interfacial extraction reaction of rare earth ions was a pseudo-first-order reversible reaction in the thin oil film extraction system, conforming to the proposed extraction kinetics model. The change of extraction behaviors was dependent on the orientation, arrangement and mutual interaction behaviors of molecules at oil-water two phases interface. By MD simulations, it indicates that the extraction behavior of Er3+ ions in oil film extraction system has a close relationship with the interfacial behavior of extractant molecule. The present work provides a theoretical basis for developing a new method of strengthening extraction and separation of rare earth ions from low-concentration rare earth solutions.

Extraction kinetics and kinetic separation of La(III), Gd(III), Ho(III) and Lu(III) from chloride medium by HEHEHP

According to the tetrad-effect, 14 elements of lanthanides can be divided into four groups. In our previous study, a new approach was proposed for the kinetic separation of four rare earth ions La(III), Gd(III), Ho(III) and Lu(III) coming from four groups. In that study, four rare-earth ions were kinetically separated from their coexisting mixed aqueous solutions, by performing liquid-column elution using the aqueous solution containing four lanthanide rare-earth ions as the stationary phase and the dispersed organic oil droplets containing HEHEHP (2-ethyl hexyl phosphonic acid mono 2-ethyl hexyl ester) extractant as the mobile phase. The study of extraction kinetics is very important for understanding the kinetic separation of rare earth ions, which was carried out in this paper. The extraction kinetics of La(III), Gd(III), Ho(III) and Lu(III) by HEHEHP diluted in heptane were investigated using single drop method. The different parameters affecting the extraction rate such as column length, specific interfacial area, rare earth ion concentration, extractant concentration, hydrogen ion concentration and temperature were separately studied and the rate equations are deduced. It is first order with respect to rare earth ion and HEHEHP concentrations, and negative first order with respect to hydrogen ion concentrations. The rate constants at 293.15 K are 10−6.23, 10−5.73, 10−5.58 and 10−5.43, respectively. The experimental results demonstrate that the extraction rate of La(III), Gd(III), Ho(III) or Lu(III) is diffusion-controlled, and the extraction reaction takes place at the interface rather than in the bulk phase. The extraction model was proposed. Besides, the kinetic separation of rare earth ions by HEHEHP oil drops was discussed.

Magnetic Field Directed Rare-Earth Separations.

The separation of rare-earth ions from one another is challenging due to their chemical and physical similarities. Nearly all rare-earth separations rely upon small changes in ionic radii to direct speciation or reactivity. Herein, we show that the intrinsic magnetic properties of the rare-earth ions impact the separations of light/heavy and selected heavy/heavy binary mixtures. Using TriNOx3- ([{(2-t BuNO)C6 H4 CH2 }3 N]3- ) rare-earth complexes, we efficiently and selectively crystallized heavy rare earths (Tb-Yb) from a mixture with light rare earths (La and Nd) in the presence of an external Fe14 Nd2 B magnet, concomitant with the introduction of a concentration gradient (decrease in temperature). The optimal separation was observed for an equimolar mixture of La:Dy, which gave an enrichment factor of EFLa:Dy =297±31 for the solid fraction, compared to EFLa:Dy =159±22 in the absence of the field, and achieving a 99.7 % pure Dy sample in one step. These results indicate that the application of a magnetic field can improve performance in a molecular separation system for paramagnetic rare-earth cations.

One-step fabrication of imprinted mesoporous cellulose nanocrystals films for selective separation and recovery of Nd(III)

Previously, we investigated imprinted silica films templated by cellulose nanocrystals for the selective adsorption of rare earth ions from acidic systems, but the cost of organosilane limits the application of silica film adsorbents. Considering the cost and outstanding properties of cellulose, converting this renewable biological resource into an adsorbent material is a vital step towards sustainable development. One-step fabrication of imprinted mesoporous cellulose nanocrystals films (IMCFs) was implemented via ionic imprinting technology and they were applied to efficiently and selectively separate neodymium ions [Nd(III)]. Transmission photographs clearly demonstrated there is a highly ordered mesoporous structure after removal of silicon source. Nitrogen adsorption measurements showed two obtained materials possess high specific surface area, providing a good premise for efficient separation. When employed as absorbents, the maximum adsorption capacity of IMCFs is almost three folds than that of NIMCFs, reaching 18.22 mg g−1. The distribution coefficient of IMCFs for Nd(III) reached 435.46 mL g−1, much higher than other interfering ions. Repeatability tests showed IMCFs retained 81.55% of initial adsorption capacity after five adsorption cycles. In summary, this work presents a new avenue to construct imprinted mesoporous cellulose nanocrystals films for separation of rare earth ions.

Separation of Rare Earths from the Transition Metals Using a Novel Ionic-Liquid-Based Aqueous Two-Phase System: Toward Green and Efficient Recycling of Rare Earths from the NdFeB Magnets

An ionic-liquid-based aqueous two-phase system (iL-ATPS) consisting of an ionic liquid, tributylmethylammonium nitrate (N4441NO3), and NaNO3 aqueous solutions was developed for the extraction and separation of rare-earth ions, for example Nd(III), from transition-metal ions. The excellent selectivity of a green nonfluorinated ionic liquid and the low-viscosity feature of an aqueous two-phase system were combined in our suggested iL-ATPS. The results indicated that efficient separation of Nd(III) from transition-metal ions, Fe(III), Ni(II), and Co(II), could be obtained in our suggested iL-ATPS. Furthermore, different parameters of the separation process, including the concentrations of HNO3 and NaNO3 and the added amount of N4441NO3, were optimized. Notably, the extraction kinetics of Nd(III) could be improved significantly in the present iL-ATPS compared with the conventional organic-solvent-based ionic-liquid extraction systems. The similar environment across the liquid–liquid interface was revealed by ...

Anti-fouling and thermosensitive ion-imprinted nanocomposite membranes based on grapheme oxide and silicon dioxide for selectively separating europium ions

The increasing amount of europium in aqueous environment from rare earth industry has become a serious environmental challenge. Significant efforts have been focused on ion-imprinting membranes (IIMs) for selective separation of ions from analogues. Based on ion-imprinting technique, we have developed Eu3+-imprinted nanocomposite membranes (Eu-IIMs) for selectively separating Eu3+ from La3+, Gd3+ and Sm3+. Polydopamine (pDA) was previously synthesized on basal membranes to augment the interfacial adhesion. Grapheme oxide (GO) and modified silicon dioxide (kSiO2) were synergistically stacked on pDA-modified substrates to form hydrophilic nanocomposite membranes. Ag nanoparticles were modified on the surface to enhance anti-fouling performance. The temperature-controlled selective recognition sites were formed using N-isopropylacrylamide (NIPAm) and acrylamide (Am) as functional monomers as well as europium ions as templates by RAFT (reversible addition-fragmentation chain transfer) method. Large enhanced Eu3+-rebinding capacity (101.14 mg g−1), adsorptive selectivity (1.82, 1.57, 1.45 for Eu3+/La3+, Eu3+/Gd3+, Eu3+/Sm3+) and permselectivity (3.82, 3.47, 3.34 for La3+/Eu3+, Gd3+/Eu3+, Sm3+/Eu3+) were achieved on Eu-IIMs with superior regeneration performance. Additionally, the negligible damage of the membranes after buried for 20 d indicated the superior anti-fouling property of the Eu-IIMs. The ion-imprinted nanocomposite membranes synthesized in this work have shown great potentials for selective separation of rare earth ions.

Ethylenediaminetriacetic Acid-Functionalized Activated Carbon for the Adsorption of Rare Earths from Aqueous Solutions

A novel and low-cost ethylenediaminetriacetic acid-functionalized activated carbon (EDTA-AC) was synthesized by anchoring N-[(3-trimethoxysilyl)propyl]ethylenediaminetriacetic acid (TMS-EDTA) to oxidized activated carbon (AC). Material characterization was done by FTIR and Raman spectroscopy, TGA, N2 physisorption, SEM and the Boehm titration method, the latter being used to determine the amount and type of oxygen functional groups present in carbon samples. EDTA-AC was tested for the adsorption and separation of rare-earth ions from aqueous solutions, in order to evaluate the feasibility of using this material for the recovery of rare earths from industrial wastewater, tailings and electronic waste, like batteries, magnets and lamp phosphors. The maximum adsorption capacity of EDTA-AC was derived for Nd(III) by constructing an adsorption isotherm and fitting the data to the Langmuir adsorption model. A kinetic and thermodynamic study were performed by varying the contact time and the temperature and plot...

Selective separation of rare earth ions from aqueous solution using functionalized magnetite nanoparticles: kinetic and thermodynamic studies

Separation of rare earth ions (RE3+) from aqueous solution is a tricky problem due to their physico-chemical similarities of properties. In this study, we investigate the influence of the functionalized ligands on the adsorption efficiency and selective adsorption of La3+, Nd3+, Gd3+ and Y3+ from aqueous solution using Magnetite (Fe3O4) nanoparticles (NPs) functionalized with citric acid (CA@Fe3O4 NPs) or l-cysteine (Cys@Fe3O4 NPs). The microstructure, thermal behavior and surface functionalization of the synthesized nanoparticles were studied. The general adsorption capacity of Cys@Fe3O4 NPs was found to be high (98mgg−1) in comparison to CA@Fe3O4 NPs (52mgg−1) at neutral pH 7.0. The adsorption kinetic studies revealed that the adsorption of RE3+ ions follows a pseudo second-order model and the adsorption equilibrium data fits well to the Langmuir isotherm. Thermodynamic studies imply that the adsorption process was endothermic and spontaneous in nature. Controlled desorption within 30min of the adsorbed RE3+ ions from both Cys@Fe3O4 NPs and CA@Fe3O4 NPs was achieved with 0.5M HNO3. Furthermore, Cys@Fe3O4 NPs exhibited a higher separation factor (SF) in the separation of Gd3+/La3+, Gd3+/Nd3+, Gd3+/Y3+ ions compared to CA@Fe3O4 NPs.

Separation of rare-earth ions from ethylene glycol (+LiCl) solutions by non-aqueous solvent extraction with Cyanex 923

Mixtures of rare earths are separation by non-aqueous solvent extraction with two immiscible organic phases.

リン酸エステル配位高分子を利用するランタノイド相互分離

水を溶媒として用いる環境調和型な高選択的ランタノイド相互分離法の開発を目指して，リン酸エステルが形成する配位高分子を利用するイオン交換と沈殿分離を検討した．イオン交換では，ランタノイド系列における選択性に差があり，水溶液系でランタノイド相互分離できる可能性が示唆された．さらに，イオン交換率に依存して選択性が変化する現象を捉えた．これは，配位子─金属イオン間の"静電力"に加えて，"配位高分子骨格に対するイオンサイズ適合性"が寄与するためと考えられ，従来のイオン交換とも溶媒抽出とも異なる選択性の発現に成功したと言える．さらに，リン酸エステル配位高分子の微粉末をクライオゲル化してモノリス形状にする方法を考案し，イオン交換の分配係数と速度定数の向上が可能であることを示した．分別沈殿では，Nd3＋とDy3＋の相互分離に焦点を絞り，無機塩生成を利用する場合よりもはるかに優れた分離が可能であることを明らかにした．

Tributyl phosphate-[C<sub>n</sub>min][Tf<sub>2</sub>N]を用いた塩酸溶液からの希土類元素の抽出および逆抽出

Mutual separation of rare earth ions is very difficult because of their similar chemical properties. In this study, extraction of Nd (III), Dy (III), and Pr (III) from hydrochloric acid solution and their back extraction have been investigated using the mixture of tributyl phosphate, TBP, and 1-alkyl-3-methylimidazoliumbis[ (trifluoromethyl) sulfonyl]imide, [Cnmim][Tf2N] (n, the alkyl chain length, was 2, 4, and 6), in order to clarify the possibility of mutual separation and recovery of these elements. Synergistic effect between TBP and [Cnmim][Tf2N] was found because the extraction was highly enhanced using their mixture, while the extraction by the individual reagent was very low. Although the extraction was increased with a decrease in the n value, mutual separation was difficult because the extraction behavior was similar to one another. Ammonium formate was found to be effective as a back extraction reagent because Pr (III) and Nd (III) were precipitated out as formates while Dy (III) was quantitatively back extracted without precipitation. Precipitation formation was faster in Pr (III) than Nd (III). Based on these results, a possibility of the mutual separation among these three ions was shown.

Magnetic separation of Dy(III) ions from homogeneous aqueous solutions

The possibility to enrich paramagnetic dysprosium(III) ions in a magnetic field gradient is proved by means of interferometry, which may open the route for a magnetic separation of rare earth ions from aqueous solutions. The separation dynamics are studied for three different concentrations of DyCl3 and compared with those found recently in a sulphate solution of the 3d ion Mn(II). In view of the similar-sized hydration spheres for Dy(III) and Mn(II), the slower separation dynamics in DyCl3 is attributed to both a higher densification coefficient and the strong impact of Brownian motion due to the absence of ion-pair clusters.

Study on recognition and separation of rare earth ions at picometre scale by using efficient ion-surface imprinted polymer materials

The graft-polymerization of hydroxyethyl methylacrylate (HEMA) on micro-sized silica gel particles was first conducted by initiating of a surface-initiating system, which was constituted by the bonded amino groups on the modified silica gel particles and persulfate in the solution, obtaining the grafted particles PHEMA/SiO2 with a high grafting degree of 40g/100g. Subsequently, 8-hydroxyquinoline as a ligand with strong chelating ability for metal ions was bonded on the side chains of the grafted macromolecule PHEMA through the substitution reaction between 5-chloromethyl-8-hydroxyquinoline (CHQ) and the hydroxyl group of the grafted macromolecule PHEMA, preparing the functional grafted particles HQ-PHEMA/SiO2. On the basis of examining the chelating adsorption property of HQ-PHEMA/SiO2 particles for Pr3+ ion, the Pr3+ ion surface-imprinting was carried out by using the effective surface-imprinting technique of “pre-grafting and post-crosslinking/imprinting” established by our group. During the surface-imprinting process, Pr3+ ion was used as a template ion, and 2,2′-dichlorodiethyl ether was used crosslinked, resulting in the Pr3+ ion surface-imprinted material IIP-HQP/SiO2. The recognition and binding characters of IIP-HQP/SiO2 towards Pr3+ ion were investigated in-depth with La3+ and Ce3+ ions as two contrast ions. The experimental results show that the IIP-HQP/SiO2 particles possess special recognition selectivity and high binding ability for Pr3+ ion. The binding capacity of IIP-HQP/SiO2 for Pr3+ ion reaches 0.13mmol/g, and relative to La3+ and Ce3+ ions, the selectivity coefficients of IIP-HQP/SiO2 for Pr3+ ion are 5.22 and 5.12, respectively. La, Ce and Pr are three neighbouring rare earth elements, and the ion radius differences between La3+, Ce3+ and Pr3+ ions are only in a range of 2–5pm. Obviously, in this investigation, the mutual separation of La3+, Ce3+ and Pr3+ ions at picometre scale is realized successfully by using the ion surface-imprinted polymer material with high performance.

Acid-Stable Magnetic Core–Shell Nanoparticles for the Separation of Rare Earths

Core–shell Fe3O4@SiO2 nanoparticles were prepared with a modified Stober method and functionalized with N-[(3-trimethoxysilyl)propyl]ethylenediamine triacetic acid (TMS-EDTA). The synthesis was optimized to make core–shell nanoparticles with homogeneous and thin SiO2 shells (4.8 ± 0.5 nm) around highly superparamagnetic Fe3O4 cores (14.5 ± 3.0 nm). The core–shell Fe3O4@SiO2(TMS-EDTA) nanoparticles were then used for the extraction and separation of rare-earth ions. By comparing them with previously published results for Fe3O4(TMS-EDTA) and SiO2(TMS-EDTA) nanoparticles, it was clear that the core–shell nanoparticles combine the advantage of magnetic retrieval observed for Fe3O4(TMS-EDTA) nanoparticles with the higher selectivity observed for SiO2(TMS-EDTA). The advantages of the SiO2 shell include a lower specific weight and a larger grafting density compared to Fe3O4 surfaces, but also the improved resistance to acidic environments required for the stripping of rare-earth ions.