Applied Science, Faculty of
Non UBC
Mechanical Engineering, Department of
DSpace
Membranes 12 (1): 80 (2022)
Bashiri, Atiyeh
Nikzad, Arash
Maleki, Reza
Asadnia, Mohsen
Razmjou, Amir
Recently, demands for raw materials like rare earth elements (REEs) have increased considerably due to their high potential applications in modern industry. Additionally, REEs’ similar chemical and physical properties caused their separation to be difficult. Numerous strategies for REEs separation such as precipitation, adsorption and solvent extraction have been applied. However, these strategies have various disadvantages such as low selectivity and purity of desired elements, high cost, vast consumption of chemicals and creation of many pollutions due to remaining large amounts of acidic and alkaline wastes. Membrane separation technology (MST), as an environmentally friendly approach, has recently attracted much attention for the extraction of REEs. The separation of REEs by membranes usually occurs through three mechanisms: (1) complexation of REE ions with extractant that is embedded in the membrane matrix, (2) adsorption of REE ions on the surface created-active sites on the membrane and (3) the rejection of REE ions or REEs complex with organic materials from the membrane. In this review, we investigated the effect of these mechanisms on the selectivity and efficiency of the membrane separation process. Finally, potential directions for future studies were recommended at the end of the review.
Citation: Bashiri, A.; Nikzad, A.;Maleki, R.; Asadnia, M.; Razmjou, A.Rare Earth Elements Recovery UsingSelective Membranes via Extractionand Rejection. Membranes 2022, 12, 80.https://doi.org/10.3390/membranes12010080Academic Editor: Marek BryjakReceived: 28 November 2021Accepted: 6 January 2022Published: 11 January 2022Publisher’s Note: MDPI stays neutralwith regard to jurisdictional claims inpublished maps and institutional affil-iations.Copyright: © 2022 by the authors.Licensee MDPI, Basel, Switzerland.This article is an open access articledistributed under the terms andconditions of the Creative CommonsAttribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).membranesReviewRare Earth Elements Recovery Using Selective Membranes viaExtraction and RejectionAtiyeh Bashiri 1, Arash Nikzad 2 , Reza Maleki 3 , Mohsen Asadnia 4 and Amir Razmjou 5,*1 School of Metallurgy and Materials Engineering, Iran University of Science and Technology,Tehran 16845-161, Iran; atie_bashiri@metaleng.iust.ac.ir2 Department of Mechanical Engineering, University of British Columbia, 2054-6250 Applied Science Lane,Vancouver, BC V6T1Z4, Canada; arash.nikzad@mech.ubc.ca3 Department of Physics, University of Tehran, Tehran 14395-547, Iran; rezamaleki96@gmail.com4 School of Engineering, Macquarie University, Sydney, NSW 2109, Australia; mohsen.asadnia@mq.edu.au5 UNESCO Centre for Membrane Science and Technology, School of Chemical Engineering, University of NewSouth Wales, Sydney, NSW 2052, Australia* Correspondence: amirr@unsw.edu.auAbstract: Recently, demands for raw materials like rare earth elements (REEs) have increased con-siderably due to their high potential applications in modern industry. Additionally, REEs’ similarchemical and physical properties caused their separation to be difficult. Numerous strategies for REEsseparation such as precipitation, adsorption and solvent extraction have been applied. However,these strategies have various disadvantages such as low selectivity and purity of desired elements,high cost, vast consumption of chemicals and creation of many pollutions due to remaining largeamounts of acidic and alkaline wastes. Membrane separation technology (MST), as an environ-mentally friendly approach, has recently attracted much attention for the extraction of REEs. Theseparation of REEs by membranes usually occurs through three mechanisms: (1) complexation ofREE ions with extractant that is embedded in the membrane matrix, (2) adsorption of REE ions on thesurface created-active sites on the membrane and (3) the rejection of REE ions or REEs complex withorganic materials from the membrane. In this review, we investigated the effect of these mechanismson the selectivity and efficiency of the membrane separation process. Finally, potential directions forfuture studies were recommended at the end of the review.Keywords: rare earth elements (REEs); polymer inclusion membrane (PIM); ion-imprinted membrane(IIM); nanocomposite membrane; solid membrane1. IntroductionIn recent years, the consumption of scarce raw materials such as rare earth elements(REEs) has exponentially increased due to their fundamental requirements in advancedtechnologies and industrial applications [1]. Lots of cutting-edge techniques such as newcatalysts in petroleum refining, rechargeable batteries for electric vehicles, phosphors inflat panel display and ceramics presently need the REEs-based materials [2–6]. Owing tothe necessity of REEs, they are famous as “the vitamins of modern industry” [7]. REEsinclude a large metallic group of 17 SC and Y elements besides the 15 lanthanide elements,La, Pr, Ce, Pm, Nd, Sm, Eu, Gd, Dy, Tb, Ho, Tm, Er and Yb [8,9], which typically consistof light REEs (LREEs, La-Eu) and heavy REEs (HREEs, Y and Gd-Lu) categories. REEsgenerally have similar electronic configurations, resulting in similar chemical and physicalproperties [10,11]. The REEs are not rare compared to precious metals, but their lowconcentrations (about ppb) and vast locations make them challenging to collect [2,8]. Themain ores of REEs comprise monazite, xenotime, lanthanite, allanite, bastnäsite, lopariteand phosphate rocks [3]. Currently, China is the leading REEs producer, accounting forabout 90% of REEs worldwide [12]. Nevertheless, China has limited its REE exports due toMembranes 2022, 12, 80. https://doi.org/10.3390/membranes12010080 https://www.mdpi.com/journal/membranesMembranes 2022, 12, 80 2 of 23growing domestic demand, leading to a global REE supply shortage [2,13]. Figure 1 showsthe diagram of production shares of REEs from different countries around the world in2020 [14].Figure 1. Schematic diagram of production shares of REEs from different countries around the worldin 2020, illustrating that China has the highest production share of up to 58%, followed by USA,Myanmar, and Australia, as mentioned on the diagram [14].Ironically, the industrial separation from REEs ores involves severe environmentalpollution and an increased economic price of these elements. In addition, because REEshave identical properties, their separation is a complex process [15]. Therefore, the REEsrecovery from wastewaters is of great importance and reduces their production cost [4,16].Meanwhile, recovering REEs from industrial wastewaters as secondary resources is stilla major challenge due to low concentrations. So far, various technologies have beenapplied to remove and recover REEs from different contaminated wastewaters, such assolvent extraction [17], ion exchange [18], precipitation [19,20], adsorption [21,22], andelectrochemical processes [23]. Because of its large production capacity and fast masstransfer, the primary industrial-scale method is a solvent extraction from their leachingsolution [24]. However, this is still facing some challenges such as low selectivity andpurity of the extracted elements, remaining large amounts of wastes and high consumptionof reagents [25]. In the precipitation process, created sludge needs further treatment. Inaddition, the attendance of other ions in the obtained stream can affect the extractionefficiency [26]. Also, a purification step after adsorption is required for the adsorptionprocess, which is associated with consuming chemical materials and increasing costs [27,28].Thus, new separation methods need to be developed for the efficient extraction of REEsfrom secondary resources. Recently, membrane separation technology (MST) has attracteda lot of attention due to its porous structure, good selectivity and environmentally friendlyessence. In this study, we evaluate MST for the recovery of REEs. The review provides theREEs separation mechanisms from various membrane techniques. The structure, selectivityand feasibility of these membranes are also investigated.2. Membrane Separation Technology (MST) for Recovery of REEsMST, a combined process of simultaneous removal and extraction without the needfor thermal operations, can be a promising method for a green separation approach. Inrecent years, the use of membrane technology for the recovery of REEs from effluentand wastewater due to many advantages, such as high selectivity and recovery, easyoperation, the minimum created volume of sludge and the limited production of wastematerial, has attracted much attention [29]. Significant research on the membrane processMembranes 2022, 12, 80 3 of 23for REEs separation has involved the liquid-liquid extraction method. Although thismethod is the most used and conventional way to extract REEs on an industrial scale [30],consistently low extraction efficiency, the presence of impurities in the final product, a lowcontact area and loss of the extractant in the aqueous phase are still present in large-scaleprocesses [31]. To solve these problems, various types of liquid membranes (LMs), such asemulsion liquid membrane (ELM), bulk liquid membrane (BLM) and electrostatic quasi-liquid membrane (ESPLM), have been developed to improve the extraction of REEs [32–37].In all these membranes, the separation mechanism is generally permeating lanthanideions (Ln3+) from feed solution through an organic phase to the stripping phase due tothe concentration gradient. However, because of the weak stability and low membranesurface of these methods, which is specified by the different solubility of the phase, newmethods such as the supported liquid membrane (SLM) [38–42] and the hollow fibersupported liquid membrane (HFSLM) [43–48]—upon which extractant is embedded on theporous support—have been developed [16]. For example, J. Martínez et al. [49] applied aneffective flat sheet-supported liquid membrane (SLM) for the recovery of Y3+-Nd3+-Dy3+,using bis (2-ethylhexyl) hydrogen phosphate (D2EHPA) as an extractant and polymericsupport. However, the most significant disadvantage of supported liquid membranesis that an aqueous solution usually wets the porous structure support and is inevitablyblocked by carriers. A solvent extraction process followed by a hollow fiber-supportedliquid membrane (HFSLM), with a 1 mol/L D2EHPA extractant, was studied by Achmadet al. [17]. The best recovery percentage achieved at 90 min for Nd3+, Dy3+ and Pr3+ was63.13%, 15.21% and 56.29%, respectively.Although the application and development of these methods have shown significantseparation effects, their utilization on an industrial scale still involves some problems.As a result, the REEs separation processes have shifted towards applying stable non-liquid membrane processes, in which carriers are chemically or physically attached to themembrane or a porous supporting structure [50]. Therefore, they can be used without theconcern of extractant loss into the aqueous phase. Polymer inclusion membrane (PIM) is arelatively new method for the solid extraction of REEs, which is inexpensive and has highflux and mechanical flexibility [51–53]Other solid extraction methods for separating REEs are mainly included in ion-imprinted techniques [54–57] on polymer membranes. Some other membranes, suchas metal-organic frameworks (MOFs) membranes, carbon membranes and stainless-steelmembranes, due to their unique properties, also have a high potential for separation ofREEs [58–61]. The separation mechanism of these methods is mainly involved in the ad-sorption or rejection of target ions from the surface and the transition of other ions throughthe membrane. Consequently, the extraction and separation mechanism of REEs can becategorized into three groups:1. Diffusion/permeation mechanism.2. Facilitated/retarded permeation mechanism.3. Rejection mechanism.In the following sections, the operation of these mechanisms for the extractionof REEs is discussed in detail. Also, the advantages and disadvantages of separatingdifferent REEs from various waste streams with respect to the use of these mechanisms,have been investigated.3. Diffusion/Permeation MechanismAs illustrated in Figure 2, the extraction of REE ions in a permeable membrane occursthrough co-transport and counter-transport mechanisms. In the co-transport mechanism,the RE3+ and its anions such as NO3−, Cl− or SO42− make complex with organic extractant(according to Equation (1)) and diffuse together through the membrane, appropriate forneutral extractants.RE3+ + 3X− + A(0) ↔ REX3.A(0) (1)Membranes 2022, 12, 80 4 of 23Figure 2. The extraction mechanism of REEs through permeable membranes, (a) cotransport of bothREE ions and anionic specious by mainly neutral organic extractant and (b) counter-transport ofREE ions and H+ due to concentration differences of H+ between both sides of membrane by mainlyacidic organic extractant [4].In the counter-transport mechanism, the RE3+ makes a complex with organic extractanta (according to Equation (2)) and diffuses through the membrane due to cation exchangewith H+, which usually happens for acidic extractants. Therefore, the permeation of REEions depends on the gradient of H+ concentration from feed solution to stripping solution.In these membranes, the extraction is influenced by the structure of support or membranematrix, the kind of extractant, the presence of competitive ions, the PH of the feed solutionand stripping solution and the concentration of initial concertation [4].RE3+ + 3HA(0) ↔ REA3(0) + 3H+ (2)Membranes 2022, 12, 80 5 of 23It is worth noting that the permeation coefficient is a key parameter for these mech-anisms to evaluate the efficiency of extraction of REEs and is calculated according toEquation (3):Ln([RE3+] f eed,t[RE3+] f eed,0)= −APtV(3)where [RE3+]feed,t, [RE3+]feed,0, A, V, t and P are the REE ions concentration in the feed solutionat t time, initial REE ions concentration in the feed solution, the membrane active surface area,the volume of source solution, the time and the permeability coefficient, respectively.3.1. Supported Liquid Membranes (SLMs)The liquid membrane technique (LMT) is a huge category of extraction processes, inwhich transportation of extracted specious occurs through the membrane phase. Liquidmembranes are classified into unsupported membranes such as emulsion liquid membranes(ELMs), bulk liquid membranes (BLMs) and supported liquid membranes (SLMs). SLMsconstructed of a porous support and carrier to extract target ions have become an effectivesystem due to their high selectivity and lower carrier consumption. SLMs have been widelyused for the extraction of REEs. However, the most significant disadvantages of SLMsare low stability and block support pores by aqueous solutions. So, new approaches havebeen applied for a more effective separation of REEs by SLMs. Liang et al. [39] studied anovel hybrid flat renewal SLM with a dispersion phase using D2EHPA as the extractantand HNO3 as the stripping phase for Nd3+ extraction. The dispersion phase was composedof the membrane phase (carriers dissolved in organic solutions) and the stripping phase.The stripping phase concentrated the REE ions after suspending and still standing in thedispersion phase. The dispersion stripping phase also preserved a renewable supply forthe extractant, which would prevent the re-impregnation of typical SLM and stabilize themembrane phase fixed in the matrix phase. In an optimum condition such as 0.1 mol/LD2EHPA, 4 mol/L HNO3, 2 × 10−4 mol/L, an initial concentration of Nd3+ and feedsolution PH pf 4.6 and a time of 75 min, the extraction of Nd3+ was near 92.9%. Themechanism of REEs extraction from the SLM process using D2EHPA as an extractant fromcoal fly ash leachate is reported by Smith et al. [22].Cui et al. [62] investigated the transportation mechanism of an SLM with PVDFsupport and TODGA carrier. PVDF membrane was selected as the support due to its highthermal, chemical and mechanical stability. The extraction of REEs with TODGA in HNO3media follows Equation (4):RE3++3NO−3 +3TODGA(0) ↔ (TODGA)3.RE(NO3)3(0) (4)the sign (0) refers to the organic phase, so the extraction constant of RE3+ would be calcu-lated according to the Equation (5):KH+ =[(TODGA)3.RE(NO3)3][RE3+].[3NO−3]3.[TODGA]3 (5)The REEs extraction constants reported as KLa3+ = 5.08 × 103, KPr3+ = 9.40 × 103,KCe3+ = 1.28 × 104, KNd3+ = 7.71 × 103. The increase in acidity caused the promotion of thecomplex formation. Nevertheless, with the acidity increase, nitric acid was also extracted,which led to the occupation of extractants by the HNO3 molecules and decreased extractionefficiency. So, they used a mixture of HNO3 and NaNO3. By increasing NO3− ions from2 mol/L to 3 mol/L, the best Nd3+ transportation of 99% was achieved. The transportationmechanism in the membrane phase is depicted in Figure 3a. The REE ion bound to theextractant, and a charge balance was reached with the formation of the neutral complexwith NO3−. The complex then transfers from feed solution to membrane phase because ofhigher distribution, and thus REEs are released into the stripping solution.Membranes 2022, 12, 80 6 of 23Figure 3. (a) the schematic of REE ions extraction through the supported liquid membrane, both REEions and NO3− pass through the membrane by formation complex with TODGA carriers, which are aneutral extractant, by co-transport mechanism [62]; (b) the schematic of REE ions extraction throughthe supported liquid membrane, REE ions pass through the membrane by formation complex withDODGAA carriers, which are acidic extractants by counter-transport mechanism [63].Asadollahzadeh et al. [64] studied a synergistic extractant containing [C6MIM][NTf2]ionic liquid, trioctyl phosphine oxide (TOPO) and Tributyl phosphate (TPB) for the ex-traction of Nd3+ from Pr3+ using a supported liquid membrane system. The results showthat when the TOPO was used as an extractant in the 1.8 M H2SO4 stripping phase, thepermeation coefficient for Nd3+ and Pr3+ were 0.8627 × 106 m/s and 0.2418 × 106 m/s,respectively, and when TPB was used, the permeation coefficient for Nd3+ and Pr3+ was0.4043 × 106 m/s and 0.0910 × 106 m/s, which indicate that the separation of Nd3+ fromPr3+ was not acceptable for both extractants. However, in the case of using both TOPOand TPB, the permeation coefficient for Nd3+ and Pr3+ changed to 1.4059 × 106 m/s and0.6275 × 106 m/s, respectively. However, when [C6MIM][NTf2] ionic liquid was added toTOPO and TPB, the obtained permeation coefficients for Nd3+ of 2.3200× 106 m/s and Pr3+of 0.7112 × 106 m/s, had considerable differences. Consequently, the utilization of ionicliquids can be a beneficial approach for enhancing the selectivity of SLMs. Baba et.al [63]used [C8mim][Tf2N] as a green solvent and DODGAA as the extractant for the separationof Dy3+ and Nd3+ against ferric ions by the SLM method. After 30 h, up to 100% of REEions were transported with just 10% transportation of ferric ions. The extraction constant ofDy3+ and Nd3+ were reported as 6.26 × 10−1 and 2.35 × 10−2, respectively, which showsthe separation capability of Dy3+ and Nd3+ after the separation of Fe ions by this membrane.The transportation mechanism in the membrane phase is illustrated in Figure 3b. In Table 1,the information about some SLMs used for REEs extraction is summarized.Membranes 2022, 12, 80 7 of 23Table 1. The compound of some supported liquid membranes for extraction and recovery of REEs.MembraneMatrix Carrier Solvent RE3+ Description References- D2EHPA 2 -Y3+Nd3+Dy3+Development of a mathematical transientmodel and utilization of a new extractionselectivity definition to study the extractionand separation of REE ion mixtures with theFSHSLM process[49]PTFE 1 Aliquat-336 - Gd3+Nd3+Improvement of 28.3% and 49.5% permeabilitycoefficient for Gd3+ and Nd3+ extraction usinghydrophobic nanoparticle SiO2[65]PVDF TODGA 3 n-OctaneLa3+Ce3+Pr3+Nd3+Very fast permeation and collection of morethan 95.0% of REE ions using 0.1 MTODGA as carrier[62]polyvinylidenefluoride D2EHPA Kerosene Nd3+Development of a novel flat renewalsupported liquid membrane (FRSLM) andobtaining an extraction percentage of 92.9 forNd3+ in 75 min[39]Polypropylene(PP)TODGACyanex 923TBP 4IsoparTM LNd3+Pr3+Dy3+Use the SLM coupled with hollow supportedfiber membrane for extraction of REE ionsfrom permanent magnets wastes in thepresence of non-REEs[2]-[C6MIM][NTf2]TOPO 5TPBKerosene Nd3+Pr3+Achievement of the highest permeabilitycoefficients with the synergistic extractantcontaining [C6MIM][NTf2] ionic liquid, TOPOand TPB carriers.[64]PTFEcombination ofionic liquidsTBPD2EHPA- Ce3+Observation of maximum permeationcoefficient of 30%, 20% and 10% v/v forD2EHPA, TBP and C6MIM.NTF2 extractant[66]PVDF DODGAA 6 [C8mim][Tf2N]Nd3+Dy3+More than 99% extraction and purification ofREEs from Fe ions with [C8mim][Tf2N]containing 10 mM DODGAA[63]1 polytetrafluoroethylene; 2 bis (2-ethylhexyl) hydrogen phosphate; 3 N,N,N′,N′-tetraoctyl diglycol amide;4 Tributyl-phosphate; 5 trioctyl-phosphine-oxide; 6 N,N-dioctyldiglycol amic acid.As discussed, the SLMs have good potential for utilization in REEs extraction. Despitethe BLMs and ELMs, they use lower chemical materials and are more easily operable withmore efficiency. So, they can be applied in industrial applications; however, some problemssuch as weak stability due to pore blockage and low lifetime still need to be eliminated.3.2. Polymer Inclusion Membranes (PIMs)Polymer inclusion membranes (PIMs), as a new class of polymeric membranes,have recently attracted more attention for the extraction of metal ions, especiallyREEs [52,67]. In PIM membranes, the extraction process with stripping procedureis combined simultaneously into one device. Moreover, due to long-time stability,low carrier loss, elimination of large volumes of diluents and no problems with phaseseparation, it seems that PIM could be a potential green alternative technology for con-centrating, separating and recovering REEs [4,68]. Figure 4a draws a typical diagram ofthe transport apparatus for the extraction of Lu3+ by a P227@PVDF polymer inclusionmembrane [7]. Thus, the separation process becomes more straightforward and occurscontinuously. Despite the benefits of PIM, very little research has been carried out onthe extraction and recovery of REEs to date.Membranes 2022, 12, 80 8 of 23Figure 4. (a) Transport apparatus for extraction of Lu3+ by a P227@PVDF by simultaneously extractingand recovering Lu3+ in one device ((1) feed solution, (2) stripping solution and (3) polymer inclusionmembrane), adapted from Ref. [7]. Copyright 2021 Elsevier; (b) extraction and stripping of Lu3+ byP227@PIM, adapted from Ref. [69]. Copyright 2020 Elsevier; the surface morphology of membraneindicate the asymmetric structure of membrane with hierarchically ordered pores. The pore sizesin the inner layer and outer layer are ~1 µm and ~8 µm, so the P277@ PIM (40 wt%) have highaccessibility to the solution causing the increase of transportation of Lu3+; and (c) cation exchangetransport mechanism of Cyanex272 and Lu3+ ion by E-PIMs, which shows the Lu3+ forms complexwith a functional group (−OH) of extractant and released the H+, adapted from Ref. [70]. Copyright2021 Elsevier.Huang et al. [7] used a new PIM for Lu3+ separation and extraction from a solution thatcontained Lu3+, La3+ and Sm3+. The membrane composition was PVDF with 60 wt% as theprimary matrix and 40 wt% P227 (di(2-ethylhexyl) phosphinic acid) as the extractant andthe plasticizer. A structure with hierarchically ordered pores of P227@PIM (40 wt%) dueto high surface roughness and a large contact area with the solution exhibited improvedmembrane accessibility to the solution. Moreover, the membrane acted as an effectiveselective transporter of Lu3+ from the small pore side to the large pore side. As the P227 isan acidic extractant, the PH has a crucial role in the membrane’s selectivity. At PH = 1.5 afterfive h, the recovery factor of Lu3+, La3+ and Sm3+ were 85%, 40% and 4%, respectively. Afterthe increase of PH to 2.4, the Sm3+ was selectively separated from La3+. However, with afurther increase of PH, the La3+ separation reached 50%. This indicated that P227@PIM(40 wt%) could be an excellent membrane for separating heavy and light REEs from eachother. Carrier content, stirring speed, temperature and stripping acidity also affected thePIM transport efficiency. They reported that the mechanism of extraction and strippingLu3+ by P227 existed in the dimer form in PIM, which is a cation exchange process. Briefly,Lu3+ and the extractant carrier first contact the interface between the membrane andthe feed solution to form a complex. In the second stage, the complex diffuses throughthe membrane into the stripping solution due to differences in both sides’ acidity andthe gradient concentration of Lu3+ and H+ as driving forces. In the end, Lu3+ from theextracted complex is replaced by H+ at the membrane interface and the stripping solutionand is released into the stripping solution. The process schematic is shown in Figure 4b.The transport efficiency of Lu3+ after 5 h and 12 h reached 85% and 96%, respectively [69].Chen et al. [70] have also reported the synthesis of a novel modified EVOH polymerinclusion membrane with Cyanex272 as a carrier to separate Y3+ and Lu3+. They concludedthat the utilization of EVOH caused no difference between P = O, P − OH in Cyanex272and Lu3+ coordination. SEM and AFM analyses indicated that adding a suitable amountMembranes 2022, 12, 80 9 of 23of EVOH could produce larger surface pores and internal channels. The membrane per-meability coefficients of Lu3+ and Yb3+ were 114.82 µm/s and 156 µm/s, respectively; theprimary fluxes were also 65.61 µm/m2.s and 190.17 µm/m2.s, respectively. The Lu3+ andYb3+ separation factor was measured as 1.37 in the optimized condition. All obtainedresults demonstrate that this novel synthesized PIM with serving EVOH as a hydrophilicadditive can be further used to extract heavy REEs. Figure 4c shows a brief illustration ofthe cation exchange transport mechanism of Cyanex272 and Lu3+ in the membrane.Kelov et al. [53] introduced a polymer inclusion membrane for the selective extractionand recovery of REE ions consisting of 45% D2EHPA and 55% PVC. The complete extractionand separation of Yb3+, La3+ and Ga3+ ions were attained. Selective and complete extractionof these REEs ions was reached in the different pH of the H2SO4 feed solution (Yb3+ atpH = 0.25, Gd3+ at pH = 1.25 and La3+ at pH = 2.25). The thermodynamic extractionconstants for Yb3+, Gd3+ and La3+ reported as equal to 92,700, 85.5 and 0.896, respectively.The considerable difference of extraction factors caused the possibility of the separationof light, middle and heavy REE ions by varying solution acidity. Table 2. summarizessome other PIMs for the separation of various REEs. Described research demonstratesthat the effective and selective transport of the desired ions by PIM depends directly onthe used carrier [71]. As appropriate carriers, ionic liquids (ILs) also have reports forimproving the selectivity of PIMs. Chen et al. [72] used [A336][P507] as a bifunctionalionic liquid without any plasticizer with a PVDF matrix for the extraction of Y3+ and Lu3+.PVDF matrix (62.5 wt%) and [A336][P507] carrier (37.5 wt%) had weak physical interactionand created an asymmetric structure, which accelerated the transport of Lu3+ from smallpores in the surface with feed solution to the large pores from the surface of strippingsolution. For Lu3+ extraction, in condition of 7.5 × 10−4 mol/L LuCl3, initial pH = 2.84,1.0 mol/L HCl stripping solution, the permeation coefficient was 2.80 µm/s. Moreover, theY3+ transportation was much faster than Lu3+, more selective compared to liquid–liquidextraction. Although the ionic liquids have efficient performance on REEs extraction, someproblems such as high costs and difficulty in their synthesis restricted their uses [73,74].Table 2. The compound of some polymer inclusion membranes for extraction and recovery of REEs.MembraneMatrix Carrier Plasticizer RE3+ Description ReferencesCTA 1D2EHPA andTBP 4 NPOE8 La3+Ce3+Selectivity order (Ce/La) for TBP carrier = 1.4Selectivity order (Ce/La) for D2EHPA carrier = 2.8 [75]CTA CMPO5 andTODGA 6- Ce3+Use of combined carriers withhigh effective transport of ceriumions[76]PVDF 2 P277 - Lu3+ Selective separation of Lu3+ from La3+ and Sm3+dependent on the PH of the feed solution[7]CTA Noncyclicionophores - Ce3+ A new combination of carriers for excellent separationof cerium ions [77]CTA TODGA NPOELa3+Eu3+Lu3+High transport percentage of La3+ = 60.4%,Eu3+ = 91.2% and Lu3+ = 98.0%[71]PVC 3 D2EHPA -La3+Yb3+Gd3+Selective extraction of Yb3+ with thermodynamicextraction constants of Yb3+ = 92,700, Gd3+ = 85.5 andLa3+ = 0.896 dependent on PH of the feed solution[53]PVDF [A336][P507] - Lu3+Use of bifunctional ionic liquid with good permeationcoefficient of 2.80 µm/s compared to liquid-liquidextraction[72]Membranes 2022, 12, 80 10 of 23Table 2. Cont.MembraneMatrix Carrier Plasticizer RE3+ Description ReferencesEVOH 7 Cyanex272 - Yb3+Lu3+High permeability coefficients of Lu3+ = 114.82 µm/sand Yb3+ = 156 µm/s[69]1 Cellulose-triacetate; 2 poly-vinylidene fluoride; 3 poly-vinyl chloride; 4 tributyl-phosphate-thylphosphine oxide;5 octyl(phenyl)-N,N-diisobutylcarbamoylme; 6 N,N,N,N-tetraoctyl-3-oxapentanediamide; 7 polyvinyl-alcohol-co-ethylene; 8 2-nitrophenyl-octyl-ether.PIMs are generally more stable and relatively longer in the lifetime than supportedliquid membranes (SLMs) and can easily be prepared. However, the main problem ofthese membranes is that, after a while, due to the fouling, the membrane permeabilityreduces. Therefore, using these membranes to extract REEs in the industry requires moreimprovement and development of their durability [78].4. Facilitated/Retarded Permeation MechanismREEs family are well-known for their similar chemical and physical properties [79],such as the similarity in their radius and oxidation states (+III), which makes them hard toseparate [80]. On the other hand, several REEs are valuable in economic aspects. Therefore,required methods with high-efficiency selectivity are required to extract a particular andsubstantial element from REEs in waste streams. Recently, the use of membranes calledion-imprinted membranes and nanocomposite membranes have been considered for theextraction of REEs due to their high selectivity to desired elements from others. In thesemembranes, due to the use of unique technologies in their synthesis, the target elementis absorbed in places embedded on the surface or inside the membrane, and interferingions pass freely through the membrane. Finally, the adsorbed ion can be recovered andextracted with high purity.4.1. Ion Imprinted Membranes (IIMs)The most exciting method for selectively recognizing and separating ions is the ion-imprinted technique (IIT), which has been developed extensively due to the artificialspecific imprinting processes’ capability to recognize the target ions and their high toler-ance to acidic and basic environments. However, owing to some problems such as poorregeneration, high diffusion barriers and difficult separation for REEs, the utilization ofthis method in industrial applications is still limited. The combination of the ion-imprintedtechnique (IIT) and membrane separation technique (MST) was proposed in past decadesto solve these problems. The separation of REEs has shown high potential ion-imprintedmembranes (IIMs) to absorb and separate the specific ions from REEs with extremely highselectivity. The main ways for sorption of REEs by IIMs membrane are facilitated/retardedpermeation processes. As illustrated in Figure 5a, when the feed solution passes throughthe membrane, the template ion is adsorbed by the imprinted site, while the interferingions pass freely through the membrane. The utilization of IIMs for the extraction of REEswere reported firstly by Mosbach et al., in 1993. Accordingly, the new synthesis method(surface imprinting) and multilevel distributed structure of IIMs on membrane surfaceshave been developed for the extraction of REEs [74].Liu et al. [81] have invented a novel Dy3+ ion-imprinted 3D macroporous chitosanmembrane (II-MAC) by a simple immersion–precipitation–evaporation strategy for thesolid–liquid selective extraction of Dy3+. Chitosan, a material possessing many free hy-droxyl and amino agents with unshared pair electrons, can constitute complexes withREE ions. For the construction of the microporous structure, the silica particle as a poro-genic agent was also incorporated in imprinted material. The effect of solution pH, initialconcentration of Dy3+ and contact time were investigated. They showed that when thestream passed through the II-MAC membrane, the Dy3+ adsorbed through the rebindingof amino groups, which were positively charged during the leaching and creation of theMembranes 2022, 12, 80 11 of 23Dy3+ vacancy stage Dy3+ ions. As shown in Figure 5b, after adsorption experiments in theoptimal pH = 7 at 25 ◦C, the maximum Dy3+ adsorption capacity of the membrane Dy3+was 23.3 mg/g.Figure 5. (a) illustration of separation mechanism of ion-imprinted membranes, which REE ions areadsorbing in ion-imprinted sites and interfering ions pass through the membrane, adapted fromRef. [74]. Copyright 2021 Elsevier; (b) preparation producer of Dy3+ ion-imprinted 3D macroporouschitosan membrane (II-MAC) via a simple immersion–precipitation–evaporation strategy, adaptedfrom Ref. [81]. Copyright 2017 Elsevier; (c) producer of Eu3+ from Eu3+-imprinted membranes(Eu-IIMs) nanocomposite that shows after the creation of an active site of Eu3+ at 35 ◦C, the mem-brane gets stuck while the Eu3+ and other ions (La3+, Gd3+ and Sm3+) from membrane layers pass,adapted from Ref. [82]. Copyright 2018 Elsevier; and (d) Gd3+ separation schematic from a Gd3+-imprinted membrane (GIM) by one-dimensional carbon nanotubes and two-dimensional modifiedpolydopamine-graphene oxide adapted from Ref. [83]. Copyright 2019 Elsevier.Moreover, Nd3+, Pr3+ and Tb3+, as competitive ions with the most identical valencesand radius with Dy3+, were selected. The Dy3+ distribution coefficient in the presencewas 494.88 mL/g, that shows considerably higher than other ions. This novel II-MACcan improve the selective adsorption of Dy3+ and mass-transfer kinetics. Specifically, theprepared membrane is time-saving and convenient for Dy3+ extraction ions, which, afterfive times reusing, exhibited excellent absorption ability.Also, Wang et al. [82] developed Eu3+-imprinted membranes (Eu-IIMs) nanocom-posite for selectively separating Eu3+ from wastewaters that harm human bodies due toinhibiting prothrombin production from La3+, Sm3+ and Gd3+. The most important of thismembrane is its anti-fouling performance due to modification of the membrane surfaceMembranes 2022, 12, 80 12 of 23with Ag nanoparticles. The base of the membrane was Polydopamine (PDA) to enhancethe interfacial adhesion. Graphene oxide (GO) provides a lot of oxygen-containing func-tional groups, such as carboxyl, hydroxyl and modified silicon dioxide (kSiO2), to formhydrophilic nanocomposite membranes, which improve the low liquid fluxes and werestacked on PDA. They reported that the maximum rebinding capacity could be reachedat pH = 7 with a recovery percentage of 76.87%. At lower PH, due to the protonationof active sites, the adsorption capacity was decreased. Moreover, high Eu3+-rebindingcapacity (101.14 mg/g) with adsorptive selectivity 1.82 for Eu3+/La3+, 1.57 for Eu3+/Gd3+and 1.45 for Eu3+/Sm3+ proved the high potential of Eu-IIMs for selective separation ofEu3+. Figure 5c shows the schematic separation of Eu3+ from other REEs. For extraction ofEu3+ from the membrane after adsorption, 1 M HCl solution was used.Cui et al. [83] have recently reported the Gd3+ separation from a Gd3+-imprintedmembrane (GIM) that was constructed with interlaced stacking of Gd3+-imprinted one-dimensional carbon nanotubes (GICNTs) and two-dimensional modified polydopamine-graphene oxide (PDA@GO). Polydopamine was added to graphene oxide to increase theinterfacial adhesion. Next, the ion-imprinted polymerization was carried out on carbonnanotubes by a direct cross-link of linear polymers. Selectivity towards Gd (III) wasobtained by passing a feed solution with a concentration of 60 mg/L Gd3+, 250 mg/LLa3+ and 10 mg/L Eu3+. Isotherm and kinetic adsorption and time of permeation wereinvestigated. The results show that the GICNT membrane has high permeation selectivity(2.91 La/Gd and 2.49 Eu/Gd) towards Gd3+. To prove the membrane performance, theymeasured the adsorption capacity of Gd3+ by passing the feed from the Gd3+-imprintedmembrane (GIM) to the none-imprinted membrane (NIM). The results demonstrated theGIM had an adsorption capacity near 40 mg/g, while the NIM adsorption capacity wasless, at under 15 mg/g. So, the Gd3+-imprinted membrane had a high potential capacityfor Gd3+ separation. Figure 5d shows the scheme of Gd3+ separation from La3+ and Eu3+.Though IIMs have many benefits for the extraction of REEs, such as the easy formationof porous structure and installation, low price and high flexibility, and their applicationfor extraction of REEs seem promising in the future, their utilization is still scarce. Tra-ditional ionic imprinted polymer membranes are suffering from low sites accessibility.Thus, template ions must be completely imprinted onto the membrane surfaces to achievebetter imprinting efficiency [84,85]. Recently, a new three-dimensional (3D) wood-basedNd3+-imprinted with multilevel structure was introduced by Wu et al. [86]. Hereon, asillustrated in Figure 4a, the polydopamine (PDA)-modified layers were initially synthe-sized on the surfaces of basswood with a high macroporous structure. After that, thesandwich-like structure of 3DW-IIMs was made by carrying out an Nd3+-imprinted poly-merization process. So, uniform and abundantly dispersed Nd3+-recognition sites wereachieved on the surface, which improved the rebinding capacity (120.87 mg/g) and thehigh selectivity of Nd3+. Besides, they proved that the PDA-modified layers positivelyaffected the rebinding capacity promotion of 3DW-IIMs, which caused much more creationof Nd3+-imprinted sites due to the PDA-modified surfaces. It was demonstrated that theretarded permeation mechanism had played an influential role in the selective separationof Nd3+. Figure 4b schematically illustrates that the adsorption of Nd3+ ions occurredduring separation processes initially. Then, the same Nd3+ ions were bound onto theselective sites from the membrane. Inversely, non-template ions like Tb3+, Fe3+ and Dy3+were transported through the membrane without any ion-imprinted resistance. Basedon the obtained results, 3DW-IIMs showed excellent potential for the separation of REEions. Table 3. summarizes the conditional operation of some IIMs for the separation ofvarious REEs.IIMs are very new methods for extraction of REEs. So, their application in industryis still not popular. However, they can be an interesting alternative of liquid membranesdue to their high potential for separation of specific REE ions with high purified solution.Unfortunately, their production cost is high and new materials with low cost and easiersynthesis methods need to be developed for IIMs production.Membranes 2022, 12, 80 13 of 23Table 3. Conditional operation of some ion-imprinted membranes for extraction and recovery of REEs.TargetIon Membrane SubstancePH ofAdsorptionInitialConcentration(ppm)AdsorptionCapacity(mg/g)CompetitiveIons ReferencesDy3+ chitosan membrane 7 50 23.3Nd3+Pr3+Tb3+Fe3+[81]Eu3+Grapheme oxide(GO)/modified silicondioxide (kSiO2) onPDA-modifiedsubstrate7 50 101.14La3+Gd3+Sm3+[82]Gd3+Polydopamine/modifiedgraphene oxide(PDA@GO) and carbonnanotubes (GICNTs)on cellulose membrane7 60 - La3+Eu3+[83]Nd3+polydopamine(PDA)-modified onbasswood surfaces7 90 120.87Tb3+Fe3+Dy3+[86]Lu3+4-vinylpyridine–acetylacetone/EDMA 5.5 20 64.2Fe3+ −Mg2+Ca2+ −Al3+La3+ −Nd3+Y3+ −Gd3+Dy3+ −Tm3+Lu3+[87]4.2. Nanocomposite MembranesRecently, research into metal separation/extraction has led to a new class of materialscalled nanocomposites [88]. For example, pure polymeric membranes’ performance, selec-tivity, stability and permeability can be improved by incorporating nanoparticles such asiron, silver, aluminum, Palladium silica, zirconium, titanium and magnesium [89,90].Also, preparation of polymeric nanocomposite membranes, applying nanomaterialsbased on carbon-containing material such as single-walled nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO) nanoparticles, have beenreported due to their enhanced and more effective performance [91–93].Recently, Zolfonoun et al. [52] investigated the utilization of multi-walled carbonnanotubes membrane coated with cellulose acetate to extract REEs such as Y, Ce, La, Nd,Gd, Dy and Sm. The maximum capacity for Y3+, Ce3+, La3+, Nd3+, Dy3+, Sm3+, Gd3+ andsorption by membrane was reported 33, 23, 28, 35, 31, 41 and 37 mg/g, respectively. Themulti-walled (MWCNTs) nanotubes, because of high surface area in the range of 150 to1500 m2/g, can easily adsorb REEs and facilitate the separation process. Referred toreported results, this method is a quick and simple approach and can be noticed as asuitable method for the determining and preconcentration of REEs.Armentano et al. [94] also use a modern bio-MOF-based single-walled carbon nan-otube buckypaper (SWCNTBP) to recover lanthanides. This MOF-carbon-based membraneintroduced for the recovery of REEs for the first time exhibits high efficiency and perfor-mance in recovering Ce3+ from aqueous streams. Affected parameters such as concentrationand PH were investigated. Results showed a sorption capacity of 263.30 mg/g for Ce3+ byBioMOF@SWCNT-BP membrane. As shown in Figure 6a, the separation mechanism of Ce3+is involved in Ce3+ interaction with the COOH functional groups from SWCNTBP, followedby an uptake of MOF. As a result, BioMOF@SWCNT-BPs can be considered a cheap andMembranes 2022, 12, 80 14 of 23effective membrane technique for minimizing pollution from streams and recovering REEsfrom water.Figure 6. (a) Schematic of the recovery process of Ce3+ by BioMOF@SWCNT-BP membrane and purifyof water stream, adapted from Ref. [94]. Copyright 2021 Wiley-VCH GmbH. and (b) The separationof REEs by a layer-by-layer composite of polyvinyl amine and p-octasulfonato-calix[8]arene. Thepolyvinyl amine with a positive charge is interacted with a negative surface charge and forms thefirst layer. In the following, the second layer is constructed by p-octasulfonato-calix[8]arene witha positive charge on the first layer. So, REE positive ions can be adsorbed on the surface of porouspolymer membrane and other ions pass within the membrane, then extraction and purification arecarried out [95].Additionally, due to its high accessibility and selectivity, a new type of layer-by-layercomposite can be used to separate various kinds of REEs. Toutianoush et al. [95] haveconstructed a porous polymer membrane with layer-by-layer composition p-octasulfonato-calix[8]arene and polyvinyl amine on the surface of the membrane for separation of REEs,such as LaCl3 and YCl3. The schematic of membrane layers can be seen in Figure 6b. Theyexhibited that at suitable conditions. Permeation rates of YCl3, LaCl3, CeCl3, PrCl3 andSmCl3 were 0.08 × 10−4 m/s, 0.09 × 10−4 m/s, 0.101 × 10−4 m/s, 0.091 × 10−4 m/sand 0.093 × 10−4 m/s, respectively, which are extremely low. This can be ascribed to thecomplex formation of REE ions on the calixarenes sulfonate groups. So, the membraneis permeable for other ions but approximately impermeable for REEs ions. The strongrejection of the REE ions made the membrane useful for the enrichment of REEs ions.Membranes 2022, 12, 80 15 of 23As mentioned above, nanocomposite materials can modify membranes’ selectivityand recovery performance, but their application in the recovery of REEs from wastewaterrequires more academic research.5. Rejection MechanismIn a semipermeable membrane, separation of REEs in waste streams occurs by arejection mechanism. Accordingly, when the stream is passing through the membrane, dueto sieving mechanism (the difference between pore size of the membrane and REEs ions orREEs-complex size) or electrostatic rejection mechanism as a result of Donnan phenomenonand Nernst–Planck equation, the REEs that have been rejected from the surface of themembrane and the stream are purified. Then, the rejected REEs in a concentrated solutionare extracted. These membranes have different characteristics, which are classified intonanofiltration (NF) with a pore size lower than 2 nm, ultrafiltration (UF) with a pore sizebetween 2 nm and 50 nm and microfiltration (MF) with a pore size higher than 50 nm. Dueto the large size of their pores, the MF membranes cannot reject REE ions, but they areusually used in a pre-treatment process to remove unfavorable ions such as sodium ions,which have a severe effect on the rejection of REEs from waste streams or acidic leachates.A selective complexation method can be used to increase the REE ions rejection fromthese membranes for the information of complex between desired ions and water-solublechelates. Therefore, the complexes are rejected quickly from the membrane surface, whilethe non-complexed ions transport through the membrane.Kose-Mutlu [96] reported the micelle enhanced ultrafiltration (MEUF) method forREE ions separation from a feed solution of mixed-metal using a sodium dodecyl sulfate(SDS) achelating agent. MEUF is a separation method that combines the solubilization andultrafiltration process in which the desired ions are absorbed with micelles, so the largesize ion-complexes reject from the surface of the UF membrane from the aqueous solution.Firstly, pre-treatment by pH adjustment with NaOH was carried out by microfiltration(MF). Then, two different membrane models, UP020 and UP150 with MWCO of 20 kDa and150 kDa, respectively, were used to extract Tb3+, Nd3+, Eu3+, Er3+, Y3+ and Dy3+. Figure 7shows the removal of REE ions from the surface of the membrane. They evaluated the SDSconcentration as an important parameter on the MEUF at concentrations lower and higherthan the CMC. The increase of the SDS concentration near CMC led to an increase of REErejections and, at lower concentrations from CMC, the formation of micelles does not occurin the bulk suspension but near membrane surface due to the increase of concentrations.Concentration polarization took place and rejection of REEs was increased.On the other hand, during the UF process, rejected molecules of the surfactant stickon the membrane surface and form a micelle aggregation layer (MAL) or a gel layer on themembrane surface and cause the REEs to bind on the surface. At higher SDS concentrationsfrom CMC, the rejection of REE ions decreases, which is attributed to the shape change ofmicelles into worm-shaped with a smaller size that can easily pass through the membrane.UP020 membrane with an optimal parameter such as pH = 3.5, 60 min contact time at 25 ◦C,3 bar operation pressure and SDS concentration of 8.0 mM, have a high REEs rejection of 97%.Favre-Reguillon [97] et al., studied the Gd3+ rejection by NF-assisted complexationprocess using Desal G10 membrane and DTPA chelating agent. Without using DTPA, therejection of Gd3+ was lower than 10%, but using DTPA in PH range of 1–3, an optimumcondition (P = 4 bar, Gd3+ and DTPA concentration = 0.3 mM and T = 20), the rejectionvaried from 5% to 95%. This wide range of rejection was due to the formation and increasedconcentration of [Gd–DTPA]2− complex as a function of PH.Murthy and Choudhary [98] also studied the Rejection of Nd3+ using NF membrane(NF-300) with EDTA as complexation agent and SDS as surfactant. Using SDS and EDTA infeed solution led to an increase of Nd3+ rejection from 86.74 to 99.5% and 99.4%, respectively.Polymer complexation UF process (PCUF) is another UF-assisted method for therejection of metal ions that formed a large size of polymer complex. Various kinds ofwater-soluble polymers such as polyacrylic acid (PAA) or sodium salts of PAA can beMembranes 2022, 12, 80 16 of 23used in this method. Gong et al. [99] used Amicon Ultra-15 centrifugal membrane withMWCO of 30 KDa and PAA as a polymer complexation agent to recover several REEs.They reported that more than 90% of REEs at PH between 8–9 by 30 mg/L of PAA wererejected from the membrane.Figure 7. Schematic showing the rejection of REE ions from the surface of the membrane. The REEions that formed complexes with SDS have a larger size than membrane pores, then they are rejectedfrom the surface of the membrane, but free REE ions could easily pass through the membrane due totheir smaller size [96].ValentinaInnocenzi et al. [100] used Micellar-enhanced monotubular ceramic mem-branes with sodium dodecyl sulfate (SDS) as an anionic surfactant for Y3+ and Zn2+ removalfrom from effluents obtained from waste electrical equipment recycling plants. Two modelmonotubular ceramic ultrafiltration membranes with MWCO of 1 kDa and 210 kDa wereused. The concentration of Y3+ and Zn2+ in synthetic liquid was 30 mg/L and 2 mg/L,respectively. An excellent removal performance near 99% was obtained for both Y3+ andZn2+, which shows that retentate solution was rich in targeted ions that, for their recovery,further processed should be carried out.Ceramic membranes with multi-layered structures as an inorganic membrane werealso studied for the separation of REEs. J.López et al. [101] applied a TiO2 supported Al2O3ceramic membrane with the specification of 44.92 cm2 active area in tubular configurationwith 2 mm thickness and 6.5 mm internal diameter and 1 nm mean pore size. TiO2 was theactive layer, and MWCO of the membrane was 200 Da with 4.5 and 5.5 isoelectric points(IEP). The membrane rejection mechanism can be attributed to the protonation and deproto-nation of the TiO2 active layer surface groups (R–TiOH). The surface charge depends on pH,which is an acidic condition, the positively charged (R–TiOH2+) and negatively charged(R–TiO−) formed at basic condition. Rejection efficiencies of TiO2 ceramic membrane wereapproximately 60% which shows low selectivity of ceramic membrane for REEs becauseof the rejection of Al, Zn and Cu, alongside REE ions. A smaller pore size for ceramicmembranes should be developed to reduce transportation of undesired ions, which helpsincrease REE ions rejections. As mentioned, ceramic membranes have attracted attentiondue to their superior chemical, thermal and mechanical resistance, hydrophilic nature, easeof cleaning, lower fouling and high operational lifetime, especially in harsh feedstock [102]that can be a good selection for REEs separation. However, due to the high cost of ceramicmembranes, they are less used even in laboratory research.In general, NF and UF membranes would be excellent for the treatment of veryacidic streams, which are essential concerns for the environment due to the separation ofmonovalent ions such as H+, HSO4−, Na+, NO3− and Cl− that can pass freely throughMembranes 2022, 12, 80 17 of 23the membrane, alongside high rejection of REE trivalent ions at very low concentrations.Table 4 summarizes the information of some NF and UF membrane for REEs removal.Table 4. A compound of some NF and UF membranes for removal and recovery of REEs.MembraneTypeActiveLayerOrganicChelate RE3+ MWCO(Da) PHRejection(%) ReferencesNF270 Polyamide on a thinflm composite -La3+Pr3+Nd3+Sm3+Dy3+Yb3+180 ± 20 1 >98 [103]Amicon Ultra-15centrifugal filterunits- PAA La3+Sm3+30 7.5 >89 [99]NF-300 Polyamide EDTASDSCe3+Nd3+300 2–10 >90 [98]Single tubeMembraloxO Tl-70ceramic membrane- SDS Y3+ 1 5–6 99 [100]UP020 - SDSTb3+Nd3+Eu3+Er3+Y3+Dy3+20 3.5 >97 [96]TiO2 supportedAl2O3 ceramicmembraneTiO2 -REE ionsAl3+Zn2+Cu2+200 - 60 [101]6. ConclusionsAs the demand for rare earth elements (REEs) is intensively increasing worldwide,newly developed methods for extracting and recovering these precious metals seem con-siderably necessary. In this review, we investigated the efficient extraction of REEs bymembrane process and their extraction mechanism. The various kinds of membrane pro-cesses, their feasibility, selectivity and extraction performance were also studied. The mostcommonly used methods for REEs are precipitation, ion exchange, adsorption, solventextraction and membrane process. However, the precipitation, ion exchange and adsorp-tion due to utilization of high chemical reagents are not economical. Moreover, they arenot suitable for high concentration streams, so the amount of extractable REEs is low.The post treatment is also required to achieve high purified REEs. Currently, the solventextraction method is the most common existing method for separating and extracting REEs.However, some restrictions such as low separation selectivity, low purity of the extractedelements and high energy consumption limits their application in industry and no drasticprogress in scale-up applications has been made until now. Moreover, the remaining largeamount of acidic and alkaline wastewater is a matter of concern. Therefore, researchershave recently focused on the extraction of REEs towards using a new and environmentallyfriendly method called membrane separation technology (MST). This method has excellentpotential for scale-up extraction of REEs due to the use of lower chemical materials andeasy operation. So, MST is more economical than other mentioned methods. Additionally,high concentrated streams with various conditions such as streams with different PH orwith the presence of different undesirable ions, can be treated by this method.Membranes 2022, 12, 80 18 of 23Porous supported membranes that carrier embedded into its pores as the supportedliquid membrane (SLM) is the most popular technique for the extraction of REEs. SLMsusually consume lower carrier and is more economical. Moreover, REEs’ extraction andstripping process coincide in one apparatus, which simplifies the extraction process, makingit easier to use. However, the concern of carrier loss during extraction remains. On theother side, the selectivity of SLMs towards various REEs existed in a specific solutionis low. So, using new extractants like ionic liquids, which have high selectivity andlow toxicity than organic carriers, or other new strategies such as using two or threeextractant simultaneously, could be the focus of future research within REEs extraction.Other membrane types called solid membranes are novel membranes for the extractionof REEs due to their easy preparation and green performance, which can be an effectivealternative for liquid membranes. Polymer inclusion membranes (PIMs) are newly usedfor the extraction of various REEs. The extraction mechanism by these membranes isthe permeation of REE ions through the membrane organic phase exactly like liquidmembranes but the efficiency and performance period time are considerably higher dueto immobilization of extractant in the membrane matrix. The future perspective of PIMsfor REE extraction seems to be promising. However, more research on their feasibility andstability needs to be carried out for scale-up applications. For example, using new materialsor synthesis processes can be the main topics for future research of PIMs.Other types of new solid membranes are ion-imprinted membranes and nanocompos-ite membranes like carbon-based membranes or metal-organic framework (MOF) mem-branes; rare research has been carried out on their performance for recovery of REEs.However, they can be easily prepared, and because of their separation mechanism asfacilitated/retarded permeation mechanism and adsorption of target ion in active siteswithin the membrane, they can be used for separation and extraction of a specific REE.The utilization of IIMs and MOF membranes for REE extractant is extremely new so it isnecessary to conduct more research on their feasibility and performance. The main problemof IIMs is low stability of the template holes, especially for scale-up applications. Themost important issue for the use of these membranes on an industrial scale is the highcost of manufacturing them that need to be considered. So new synthesis method needsto be developed for producing IIMs with more stable cavities and holes with economicalprice. Moreover, MOF and nanocomposite membranes have a more promising perspectivebecause they had effective performance for water treatment in previous studies.Other membranes, which typically act as a filter, separate the REE ions by rejectionmechanism because of their pore size or surface charge of the membrane. These membranesare more useful for acidic solutions or leachate such as acid mine waters (AMWs), whichhave a low concentration of REEs and high concentration of hydrogen ions. These mem-branes usually allow the hydrogen ions to pass and reject the REE ions, so concentratedretentate of REE ions is obtained. Although NF and UF membranes are green approach forREEs recovery, they have low stability in aggressive acidic environments. Consequently,new materials like ceramic or nanocomposite materials can have positive effects on theirdevelopment for use in industrial applications. NF membranes are more applied andUF membranes are usually integrated with other methods to improve the extraction ofREEs. However, they currently have low efficiency for REEs recovery. As it turns out, thecombination of these membrane with other new routes can be more promising. Table 5summarizes the characteristics of various membranes examined in this review.We believe that improvement and development on the performance of membranes dueto their high potential properties for recovery of REEs will have a promising perspectivein the future and can have positive effects on economic feasibility and the selectivityseparation of REEs.Membranes 2022, 12, 80 19 of 23Table 5. The characteristics of various membranes for REEs extraction.Membrane Type Functional PH Selectivity Life Time PriceSupported liquidmembrane (SLM)Acidic and neutralconditions Higher for LREEsLow due to poreblockageLow for continuous extractionprocess, few consuptionchemical materials and easilyoperationPolymer inclusionmembrane (PIM)Acidic and neutralconditions Higher for HREEsLow due to fouling,low thermal, andchemical stabilityLow for continuous extractionprocess, few consuptionchemical materials and easilyoperationIon imprintedmembrane (IIM) 5–7 HighLow due to loss ofactive sites after aperiodHigh for production cost andneeded post treatmentNanocompositemembraneAcidic and neutralconditions lowLong for highchemical and thermalstabilityHigh for production costUltrafiltrationMore suitable forhigh acidicconditionsLowLong for highchemical andmechanical stabilityHigh for production cost andneeded pre-treatmentNanofiltration More suitable forhigh acidic conditions LowLong for highchemical andmechanical stabilityHigh for production cost,needed pre-treatment andconsumption of chelatingagentAuthor Contributions: All authors contributed in Conceptualization, Writing, Review and Editing.All authors have read and agreed to the published version of the manuscript.Funding: This research received no external funding.Institutional Review Board Statement: The study did not require ethical approval.Informed Consent Statement: Not applicable.Data Availability Statement: The study did not report any data.Conflicts of Interest: The authors declare no conflict of interest.References1. Pramanik, B.K.; Nghiem, L.D.; Hai, F.I. Extraction of strategically important elements from brines: Constraints and opportunities.Water Res. 2020, 168, 115149. [CrossRef]2. Kim, D.; Powell, L.; Delmau, L.H.; Peterson, E.S.; Herchenroeder, J.; Bhave, R.R. A supported liquid membrane system for theselective recovery of rare earth elements from neodymium-based permanent magnets. Sep. Sci. Technol. 2016, 51, 1716–1726.[CrossRef]3. Ali, A.H.; Dakroury, G.A.; Hagag, M.S.; Abdo, S.M.; Allan, K.F. Sorption of Some Rare Earth Elements from Acidic Solution ontoPoly (acrylic acid–co-acrylamide/16, 16-dimethylheptadecan-1-amine) Composite. J. Polym. Environ. 2021. [CrossRef]4. Chen, L.; Wu, Y.; Dong, H.; Meng, M.; Li, C.; Yan, Y.; Chen, J. An overview on membrane strategies for rare earths extraction andseparation. Sep. Purif. Technol. 2018, 197, 70–85. [CrossRef]5. Li, F.; Yang, Z.; Weng, H.; Chen, G.; Lin, M.; Zhao, C. High efficient separation of U(VI) and Th(IV) from rare earth elements instrong acidic solution by selective sorption on phenanthroline diamide functionalized graphene oxide. Chem. Eng. J. 2018, 332,340–350. [CrossRef]6. Balaram, V. Rare earth elements: A review of applications, occurrence, exploration, analysis, recycling, and environmental impact.Geosci. Front. 2019, 10, 1285–1303. [CrossRef]7. Huang, S.; Chen, J.; Zou, D. A preliminary study of polymer inclusion membrane for lutetium(III) separation and membraneregeneration. J. Rare Earths 2021, 39, 1256–1263. [CrossRef]8. Liu, J.; Martin, P.F.; Peter McGrail, B. Rare-earth element extraction from geothermal brine using magnetic core-shell nanoparticles-techno-economic analysis. Geothermics 2021, 89, 101938. [CrossRef]9. Hidayah, N.N.; Abidin, S.Z. The evolution of mineral processing in extraction of rare earth elements using solid-liquid extractionover liquid-liquid extraction: A review. Miner. Eng. 2017, 112, 103–113. [CrossRef]Membranes 2022, 12, 80 20 of 2310. Elbashier, E.; Mussa, A.; Hafiz, M.; Hawari, A.H. Recovery of rare earth elements from waste streams using membrane processes:An overview. Hydrometallurgy 2021, 204, 105706. [CrossRef]11. Asadollahzadeh, M.; Torkaman, R.; Torab-Mostaedi, M. Extraction and Separation of Rare Earth Elements by AdsorptionApproaches: Current Status and Future Trends. Sep. Purif. Rev. 2020, 50, 417–444. [CrossRef]12. Zhao, Z.; Qiu, Z.; Yang, J.; Lu, S.; Cao, L.; Zhang, W.; Xu, Y. Recovery of rare earth elements from spent fluid catalytic crackingcatalysts using leaching and solvent extraction techniques. Hydrometallurgy 2017, 167, 183–188. [CrossRef]13. Kose Mutlu, B.; Cantoni, B.; Turolla, A.; Antonelli, M.; Hsu-Kim, H.; Wiesner, M.R. Application of nanofiltration for Rare EarthElements recovery from coal fly ash leachate: Performance and cost evaluation. Chem. Eng. J. 2018, 349, 309–317. [CrossRef]14. Drobniak, A.; Mastalerz, M. Rare Earth Elements: A brief overview. Indiana J. Earth 2022, 4. [CrossRef]15. Hammache, Z.; Bensaadi, S.; Berbar, Y.; Audebrand, N.; Szymczyk, A.; Amara, M. Recovery of rare earth elements from electronicwaste by diffusion dialysis. Sep. Purif. Technol. 2021, 254, 117641. [CrossRef]16. Pavón, S.; Fortuny, A.; Coll, M.T.; Sastre, A.M. Improved rare earth elements recovery from fluorescent lamp wastes applyingsupported liquid membranes to the leaching solutions. Sep. Purif. Technol. 2019, 224, 332–339. [CrossRef]17. Ni’am, A.C.; Wang, Y.-F.; Chen, S.-W.; Chang, G.-M.; You, S.-J. Simultaneous recovery of rare earth elements from waste permanentmagnets (WPMs) leach liquor by solvent extraction and hollow fiber supported liquid membrane. Chem. Eng. Process.—ProcessIntensif. 2020, 148, 107831. [CrossRef]18. Dong, Z.; Mattocks, J.A.; Deblonde, G.J.P.; Hu, D.; Jiao, Y.; Cotruvo, J.A.; Park, D.M. Bridging Hydrometallurgy and Biochemistry:A Protein-Based Process for Recovery and Separation of Rare Earth Elements. ACS Cent. Sci. 2021, 7, 1798–1808. [CrossRef][PubMed]19. Goode, J.R. Options for the separation of rare earth elements. In Proceedings of the IMPC 2016 28th International MineralProcessing Congress, Quebec City Convention Center, Quebec City, QC, Canada, 11–15 September 2016.20. Hassas, B.V.; Rezaee, M.; Pisupati, S.V. Effect of various ligands on the selective precipitation of critical and rare earth elementsfrom acid mine drainage. Chemosphere 2021, 280, 130684. [CrossRef]21. Park, D.; Middleton, A.; Smith, R.; Deblonde, G.; Laudal, D.; Theaker, N.; Hsu-Kim, H.; Jiao, Y. A biosorption-based approach forselective extraction of rare earth elements from coal byproducts. Sep. Purif. Technol. 2020, 241, 116726. [CrossRef]22. Smith, R.C.; Taggart, R.K.; Hower, J.C.; Wiesner, M.R.; Hsu-Kim, H. Selective Recovery of Rare Earth Elements from Coal Fly AshLeachates Using Liquid Membrane Processes. Environ. Sci. Technol. 2019, 53, 4490–4499. [CrossRef]23. Pramanik, B.K.; Shu, L.; Jegatheesan, J.; Shah, K.; Haque, N.; Bhuiyan, M.A. Rejection of rare earth elements from a simulatedacid mine drainage using forward osmosis: The role of membrane orientation, solution pH, and temperature variation. ProcessSaf. Environ. Prot. 2019, 126, 53–59. [CrossRef]24. Oleinikova, M.; Muñoz, M. Transport of rare earth metal ions through activated composite membranes containing DEHPA.Solvent Extr. Ion Exch. 2000, 18, 401–419. [CrossRef]25. Tian, M.; Jia, Q.; Liao, W. Studies on Synergistic solvent extraction of rare earth elements from nitrate medium by mixtures of8-hydroxyquinoline with Cyanex 301 or Cyanex 302. J. Rare Earths 2013, 31, 604–608. [CrossRef]26. Zhou, H.; Wang, Y.; Guo, X.; Dong, Y.; Su, X.; Sun, X. The recovery of rare earth by a novel extraction and precipitation strategyusing functional ionic liquids. J. Mol. Liq. 2018, 254, 414–420. [CrossRef]27. Kegl, T.; Košak, A.; Lobnik, A.; Novak, Z.; Kralj, A.K.; Ban, I. Adsorption of rare earth metals from wastewater by nanomaterials:A review. J. Hazard. Mater. 2020, 386, 121632. [CrossRef] [PubMed]28. Korenevsky, A.A.; Sorokin, V.V.; Karavaiko, G.I. Biosorption of rare earth elements. Process Metall. 1999, 9, 299–306. [CrossRef]29. Xin, W.; Lin, C.; Fu, L.; Kong, X.Y.; Yang, L.; Qian, Y.; Zhu, C.; Zhang, Q.; Jiang, L.; Wen, L. Nacre-like Mechanically RobustHeterojunction for Lithium-Ion Extraction. Matter 2021, 4, 737–754. [CrossRef]30. Brewer, A.; Chang, E.; Park, D.M.; Kou, T.; Li, Y.; Lammers, L.N.; Jiao, Y. Recovery of Rare Earth Elements from GeothermalFluids through Bacterial Cell Surface Adsorption. Environ. Sci. Technol. 2019, 53, 7714–7723. [CrossRef] [PubMed]31. Li, C.; Ramasamy, D.L.; Sillanpää, M.; Repo, E. Separation and concentration of rare earth elements from wastewater usingelectrodialysis technology. Sep. Purif. Technol. 2021, 254, 117442. [CrossRef]32. Xie, Z.; Chen, Q.; Zhao, L. Extraction of trace rare earth by liquid surfactant membranes from phosphate rock. Zhongguo XituXuebao/J. Chin. Rare Earth Soc. 2013, 31, 269–274.33. Davoodi-Nasab, P.; Rahbar-Kelishami, A.; Safdari, J.; Abolghasemi, H. Application of emulsion nanofluids membrane for theextraction of gadolinium using response surface methodology. J. Mol. Liq. 2017, 244, 368–373. [CrossRef]34. Wang, J.; Dang, Y.; Fei, D.; Fan, W.; Dong, W. Recovery of trace lanthanum from phosphoric acid using liquid membrane extraction.Zhongguo Xitu Xuebao/J. Chin. Rare Earth Soc. 2012, 30, 13–20.35. Tang, J.; Wai, C.M. Transport of trivalent lanthanides through a surfactant membrane containing an ionizable macrocyclicpolyether. J. Membr. Sci. 1989, 46, 349–356. [CrossRef]36. Yang, X.J.; Fane, A.G.; Soldenhoff, K. Comparison of liquid membrane processes for metal separations: Permeability, stability, andselectivity. Ind. Eng. Chem. Res. 2003, 42, 392–403. [CrossRef]37. Gaikwad, A.G.; Rajput, A.M. Transport of yttrium metal ions through fibers supported liquid membrane solvent extraction. J.Rare Earths 2010, 28, 1–6. [CrossRef]38. Pei, L.; Yao, B.; Zhang, C. Transport of Tm(III) through dispersion supported liquid membrane containing PC-88A in kerosene asthe carrier. Sep. Purif. Technol. 2009, 65, 220–227. [CrossRef]Membranes 2022, 12, 80 21 of 2339. Pei, L.; Wang, L.; Yu, G. Study on a novel flat renewal supported liquid membrane with D2EHPA and hydrogen nitrate forneodymium extraction. J. Rare Earths 2012, 30, 63–68. [CrossRef]40. Pei, L.; Wang, L.; Yu, G. Separation of Eu(III) with supported dispersion liquid membrane system containing D2EHPA as carrierand HNO3 solution as stripping solution. J. Rare Earths 2011, 29, 7–14. [CrossRef]41. Doležal, J.; Moreno, C.; Hrdlicˇka, A.; Valiente, M. Selective transport of lanthanides through supported liquid membranescontaining non-selective extractant, di-(2-ethylhexyl)phosphoric acid, as a carrier. J. Membr. Sci. 2000, 168, 175–181. [CrossRef]42. Pei, L.; Yao, B.; Fu, X. Study on transport of Dy(III) by dispersion supported liquid membrane. J. Rare Earths 2009, 27, 447–456.[CrossRef]43. Ambare, D.N.; Ansari, S.A.; Anitha, M.; Kandwal, P.; Singh, D.K.; Singh, H.; Mohapatra, P.K. Non-dispersive solvent extraction ofneodymium using a hollow fiber contactor: Mass transfer and modeling studies. J. Membr. Sci. 2013, 446, 106–112. [CrossRef]44. Ramakul, P.; Mooncluen, U.; Yanachawakul, Y.; Leepipatpiboon, N. Mass transport modeling and analysis on the mutualseparation of lanthanum(III) and cerium(IV) through a hollow fiber supported liquid membrane. J. Ind. Eng. Chem. 2012, 18,1606–1611. [CrossRef]45. Yadav, K.K.; Anitha, M.; Singh, D.K.; Kain, V. NdFeB magnet recycling: Dysprosium recovery by non-dispersive solvent extractionemploying hollow fibre membrane contactor. Sep. Purif. Technol. 2018, 194, 265–271. [CrossRef]46. Pei, L.; Wang, L.; Guo, W.; Zhao, N. Stripping dispersion hollow fiber liquid membrane containing PC-88A as carrier and HCl fortransport behavior of trivalent dysprosium. J. Membr. Sci. 2011, 378, 520–530. [CrossRef]47. Geist, A.; Weigl, M.; Müllich, U.; Gompper, K. Application of novel extractants for actinide(III)/lanthanide(III) separation inhollow-fibre modules. Membr. Technol. 2003, 2003, 5–7. [CrossRef]48. Kubota, F.; Kakoi, T.; Goto, M.; Furusaki, S.; Nakashio, F.; Hano, T. Permeation behavior of rare earth metals with a calix[4]arenecarboxyl derivative in a hollow-fiber membrane. J. Membr. Sci. 2000, 165, 149–158. [CrossRef]49. Martínez, J.; Rodríguez Varela, R.; Forsberg, K.; Rasmuson, Å. Factors influencing separation selectivity of rare earth elements inflat sheet supported liquid membranes. Chem. Eng. Sci. 2018, 191, 134–155. [CrossRef]50. Li, X.; Sun, Y. Progress in solid-liquid extraction resin for separation of rare earth elements. J. Rare Earths 2005, 23, 581–592.51. Nghiem, L.D.; Mornane, P.; Potter, I.D.; Perera, J.M.; Cattrall, R.W.; Kolev, S.D. Extraction and transport of metal ions and smallorganic compounds using polymer inclusion membranes (PIMs). J. Membr. Sci. 2006, 281, 7–41. [CrossRef]52. Zolfonoun, E.; Yousefi, S.R. Simultaneous Determination of Rare Earth Elements by ICP OES After On-Line Enrichment UsingMulti-Walled Carbon Nanotubes Coated Cellulose Acetate Membrane. J. Braz. Chem. Soc. 2016, 27, 2348–2353. [CrossRef]53. Croft, C.F.; Almeida, M.I.G.S.; Cattrall, R.W.; Kolev, S.D. Separation of lanthanum(III), gadolinium(III) and ytterbium(III) fromsulfuric acid solutions by using a polymer inclusion membrane. J. Membr. Sci. 2018, 545, 259–265. [CrossRef]54. Yusoff, M.M.; Mostapa, N.R.N.; Sarkar, M.S.; Biswas, T.K.; Rahman, M.L.; Arshad, S.E.; Sarjadi, M.S.; Kulkarni, A.D. Synthesis ofion imprinted polymers for selective recognition and separation of rare earth metals. J. Rare Earths 2017, 35, 177–186. [CrossRef]55. Kala, R.; Biju, V.M.; Rao, T.P. Synthesis, characterization, and analytical applications of erbium(III) ion imprinted polymer particlesprepared via γ-irradiation with different functional and crosslinking monomers. Anal. Chim. Acta 2005, 549, 51–58. [CrossRef]56. Zhang, N.; Hu, B.; Huang, C. A new ion-imprinted silica gel sorbent for on-line selective solid-phase extraction of dysprosium(III)with detection by inductively coupled plasma-atomic emission spectrometry. Anal. Chim. Acta 2007, 597, 12–18. [CrossRef]57. Wang, J.; Wei, J.; Li, J. Straw-supported ion imprinted polymer sorbent prepared by surface imprinting technique combined withAGET ATRP for selective adsorption of La3+ ions. Chem. Eng. J. 2016, 293, 24–33. [CrossRef]58. Hou, H.; Jing, Y.; Wang, Y.; Wang, Y.; Xu, J.; Chen, J. Solvent extraction performance of Ce(III) from chloride acidic solution with2-ethylhexyl phosphoric acid-2-ethylhexyl ester (EHEHPA) by using membrane dispersion micro-extractor. J. Rare Earths 2015, 33,1114–1121. [CrossRef]59. Hou, H.; Wang, Y.; Xu, J.; Chen, J. Solvent extraction of La(III) with 2-ethylhexyl phosphoric acid-2-ethylhexyl ester (EHEHPA) bymembrane dispersion micro-extractor. J. Rare Earths 2013, 31, 1114–1118. [CrossRef]60. Qiu, S.; Xue, M.; Zhu, G. Metal–organic framework membranes: From synthesis to separation application. Chem. Soc. Rev. 2014,43, 6116–6140. [CrossRef] [PubMed]61. Carboni, M.; Abney, C.W.; Liu, S.; Lin, W. Highly porous and stable metal–organic frameworks for uranium extraction. Chem. Sci.2013, 4, 2396–2402. [CrossRef]62. Xu, D.; Shah, Z.; Sun, G.; Peng, X.; Cui, Y. Recovery of rare earths from phosphate ores through supported liquid membraneusing N, N, N′, N′-tetraoctyl diglycol amid. Miner. Eng. 2019, 139, 105681. [CrossRef]63. Baba, Y.; Kubota, F.; Kamiya, N.; Goto, M. Selective recovery of dysprosium and neodymium ions by a supported liquidmembrane based on ionic liquids. Solvent Extr. Res. Dev. 2011, 18, 193–198. [CrossRef]64. Asadollahzadeh, M.; Torkaman, R.; Torab-Mostaedi, M.; Hemmati, A.; Ghaemi, A. Efficient recovery of neodymium andpraseodymium from NdFeB magnet-leaching phase with and without ionic liquid as a carrier in the supported liquid membrane.Chem. Pap. 2020, 74, 4193–4201. [CrossRef]65. Mohammad Tehrani, B.; Rahbar-Kelishami, A. A novel mass transfer coefficient correlation for improved rare earth metalsextraction via supported nanoliquids membrane. Chem. Eng. Process.–Process Intensif. 2019, 143, 107635. [CrossRef]66. Asadollahzadeh, M.; Torkaman, R.; Torab-Mostaedi, M.; Ghaemi, A.; Hemmati, A. Green imidazolium ionic liquid selectivelyfacilitates Ce(III) ion transport through supported liquid membrane. Int. J. Environ. Anal. Chem. 2020, 1–16. [CrossRef]Membranes 2022, 12, 80 22 of 2367. Bhattacharyya, A.; Mohapatra, P.K.; Hassan, P.A.; Manchanda, V.K. Studies on the selective Am3+ transport, irradiation stabilityand surface morphology of polymer inclusion membranes containing Cyanex-301 as carrier extractant. J. Hazard. Mater. 2011, 192,116–123. [CrossRef] [PubMed]68. Baczyn´ska, M.; Waszak, M.; Nowicki, M.; Przadka, D.; Borysiak, S.; Regel-Rosocka, M. Characterization of Polymer InclusionMembranes (PIMs) Containing Phosphonium Ionic Liquids as Zn(II) Carriers. Ind. Eng. Chem. Res. 2018, 57, 5070–5082. [CrossRef]69. Huang, S.; Chen, J.; Chen, L.; Zou, D.; Liu, C. A polymer inclusion membrane functionalized by di(2-ethylhexyl) phosphinic acidwith hierarchically ordered porous structure for Lutetium(III) transport. J. Membr. Sci. 2020, 593, 117458. [CrossRef]70. Chen, L.; Dong, H.; Pan, W.; Dai, J.; Dai, X.; Pan, J. Poly (vinyl alcohol-co-ethylene) (EVOH) modified polymer inclusionmembrane in heavy rare earths separation with advanced hydrophilicity and separation property. Chem. Eng. J. 2021, 426, 131305.[CrossRef]71. Ansari, S.A.; Mohapatra, P.K.; Manchanda, V.K. Cation transport across plasticized polymeric membranes containing N, N, N′,N′-tetraoctyl-3-oxapentanediamide (TODGA) as the carrier. Desalination 2010, 262, 196–201. [CrossRef]72. Chen, L.; Chen, J. Asymmetric Membrane Containing Ionic Liquid [A336][P507] for the Preconcentration and Separation ofHeavy Rare Earth Lutetium. ACS Sustain. Chem. Eng. 2016, 4, 2644–2650. [CrossRef]73. Lozano, L.J.; Godínez, C.; Ríos, A.P.d.l.; Hernández-Fernández, F.J.; Sánchez-Segado, S.; Alguacil, F.J. Recent advances insupported ionic liquid membrane technology. Membr. Sci. 2011, 376, 1–14. [CrossRef]74. Liu, T.; Chen, J. Extraction and separation of heavy rare earth elements: A review. Sep. Purif. Technol. 2021, 276, 119263. [CrossRef]75. Makowka, A.; Pospiech, B. Synthesis of Polymer Inclusion Membranes based on Cellulose Triacetate for Recovery of Lan-thanum(III) from Aqueous Solutions. Autex Res. J. 2019, 19, 288–292. [CrossRef]76. Kusumocahyo, S.P.; Kanamori, T.; Sumaru, K.; Aomatsu, S.; Matsuyama, H.; Teramoto, M.; Shinbo, T. Development of polymerinclusion membranes based on cellulose triacetate: Carrier-mediated transport of cerium(III). J. Membr. Sci. 2004, 244, 251–257.[CrossRef]77. Hiratani, K.; Kusumocahyo, S.P.; Kameta, N.; Sugaya, K.; Shinbo, T.; Kanamori, T. Synthesis of noncyclic carriers for cerium iontransport through polymer inclusion membrane. Chem. Lett. 2005, 34, 1636–1637. [CrossRef]78. Guo, W.; Ngo, H.H.; Li, J. A mini-review on membrane fouling. Bioresour. Technol. 2012, 122, 27–34. [CrossRef]79. Kojiro, S.; Iori, F.; Kiyoshi, F.; Hiroyuki, O.; Tsuyoshi, S.; Tatsuya, O.; Yoshinari, B.; Hirochika, N. Extraction behavior of Rare-earthelements using a Mono-alkylated Diglycolamic acid extractant. Solvent Extr. Res. Dev. Jpn. 2016, 23, 151–159.80. Abdollahi, H.; Maleki, S.; Sayahi, H.; Gharabaghi, M.; Darvanjooghi, M.H.K.; Magdouli, S.; Brar, S.K. Superadsorbent Fe3O4-coated carbon black nanocomposite for separation of light rare earth elements from aqueous solution: GMDH-based NeuralNetwork and sensitivity analysis. J. Hazard. Mater. 2021, 416, 125665. [CrossRef]81. Liu, E.; Xu, X.; Zheng, X.; Zhang, F.; Liu, E.; Li, C. An ion imprinted macroporous chitosan membrane for efficiently selectiveadsorption of dysprosium. Sep. Purif. Technol. 2017, 189, 288–295. [CrossRef]82. Lu, J.; Wu, Y.; Lin, X.; Gao, J.; Dong, H.; Chen, L.; Qin, Y.; Wang, L.; Yan, Y. Anti-fouling and thermosensitive ion-imprintednanocomposite membranes based on grapheme oxide and silicon dioxide for selectively separating europium ions. Hazard. Mater.2018, 353, 244–253. [CrossRef]83. Cui, K.; Gao, B.; Tai, M.; Su, B. A facile bionic strategy towards Gd(III)-imprinted membranes via interlaced stacking ofone-dimensional/two-dimensional nanocomposite materials. J. Taiwan Inst. Chem. Eng. 2019, 95, 652–659. [CrossRef]84. Zheng, X.; Zhang, Y.; Zhang, F.; Li, Z.; Yan, Y. Dual-template docking oriented ionic imprinted bilayer mesoporous films withefficient recovery of neodymium and dysprosium. J. Hazard. Mater. 2018, 353, 496–504. [CrossRef] [PubMed]85. Wu, Y.; Lu, J.; Xing, W.; Ma, F.; Gao, J.; Lin, X.; Yu, C.; Yan, M. Double-layer-based molecularly imprinted membranes fortemplate-dependent recognition and separation: An imitated core-shell-based synergistic integration design. Chem. Eng. J. 2020,397, 125371. [CrossRef]86. Wu, Y.; Lin, R.; Ma, F.; Xing, W.; Pan, J. Three-dimensional macroporous wood-based selective separation membranes decoratedwith well-designed Nd(III)-imprinted domains: A high-efficiency recovery system for rare earth element. J. Colloid Interface Sci.2021, 587, 703–714. [CrossRef]87. Lai, X.; Hu, Y.; Fu, Y.; Wang, L.; Xiong, J. Synthesis and Characterization of Lu(III) Ion Imprinted Polymer. Inorg. Organomet.Polym. Mater. 2012, 22, 112–118. [CrossRef]88. Comandella, D.; Bonani, W.; Ciscar, J.B.; Ponti, J.; Cologna, M.; Popa, K.; Gilliland, D. Recovery of rare earth elements bynanometric CeO2embedded into electrospun PVA nanofibres. RSC Adv. 2021, 11, 19351–19362. [CrossRef]89. Ouda, M.; Hai, A.; Krishnamoorthy, R.; Govindan, B.; Othman, I.; Kui, C.C.; Choi, M.Y.; Hasan, S.W.; Banat, F. Surface tunedpolyethersulfone membrane using an iron oxide functionalized halloysite nanocomposite for enhanced humic acid removal.Environ. Res. 2022, 204, 112113. [CrossRef] [PubMed]90. Sarkar, S.; Chakraborty, S. Nanocomposite polymeric membrane a new trend of water and wastewater treatment: A short review.Groundw. Sustain. Dev. 2021, 12, 100533. [CrossRef]91. Ng, L.Y.; Chua, H.S.; Ng, C.Y. Incorporation of graphene oxide-based nanocomposite in the polymeric membrane for water andwastewater treatment: A review on recent development. J. Environ. Chem. Eng. 2021, 9, 105994. [CrossRef]92. Kim, Y.-S.; Seo, K.-S.; Choi, S.-H. Polymeric nanocomposite proton exchange membranes prepared by radiation-inducedpolymerization for direct methanol fuel cell. Radiat. Phys. Chem. 2016, 118, 35–41. [CrossRef]Membranes 2022, 12, 80 23 of 2393. Liang, B.; He, X.; Hou, J.; Li, L.; Tang, Z. Membrane Separation in Organic Liquid: Technologies, Achievements, and Opportunities.Adv. Mater. 2019, 31, e1806090. [CrossRef] [PubMed]94. Tursi, A.; Mastropietro, T.F.; Bruno, R.; Baratta, M.; Ferrando-Soria, J.; Mashin, A.I.; Nicoletta, F.P.; Pardo, E.; De Filpo, G.;Armentano, D. Synthesis and Enhanced Capture Properties of a New BioMOF@SWCNT-BP: Recovery of the EndangeredRare-Earth Elements from Aqueous Systems. Adv. Mater. Interfaces 2021, 8, 2100730. [CrossRef]95. Toutianoush, A.; El-Hashani, A.; Schnepf, J.; Tieke, B. Multilayer membranes of p-sulfonato-calix[8]arene and polyvinylamineand their use for selective enrichment of rare earth metal ions. Appl. Surf. Sci. 2005, 246, 430–436. [CrossRef]96. Kose-Mutlu, B.; Hsu-Kim, H.; Wiesner, M.R. Separation of rare earth elements from mixed-metal feedstocks by micelle enhancedultrafiltration with sodium dodecyl sulfate. Environ. Technol. 2020, 1–13. [CrossRef]97. Sorin, A.; Favre-Reguillon, A.; Pellet-Rostaing, S.; Sba, M.; Szymczyk, A.; Fievet, P.; Lemaire, M. Rejection of Gd(III) bynanofiltration assisted by complexation on charged organic membrane: Influences of pH, pressure, flux, ionic strength andtemperature. Membr. Sci. 2005, 267, 41–49. [CrossRef]98. Murthy, Z.V.P.; Choudhary, A. Application of nanofiltration to treat rare earth element (neodymium) containing water. J. RareEarths 2011, 29, 974–978. [CrossRef]99. Duan, H.; Lin, J.; Gong, Z.; Huang, J.; Yang, S. Removal of high-salinity matrices through polymer-complexation–ultrafiltration forthe detection of trace levels of REEs using inductively coupled plasma mass spectrometry. Talanta 2015, 143, 287–293. [CrossRef]100. Innocenzi, V.; Prisciandaro, M.; Tortora, F.; Mazziotti di Celso, G.; Vegliò, F. Treatment of WEEE industrial wastewaters: Removalof yttrium and zinc by means of micellar enhanced ultra filtration. Waste Manag. 2018, 74, 393–403. [CrossRef]101. López, J.; Reig, M.; Vecino, X.; Gibert, O.; Cortina, J.L. Comparison of acid-resistant ceramic and polymeric nanofiltrationmembranes for acid mine waters treatment. Chem. Eng. J. 2020, 382, 122786. [CrossRef]102. Ag˘tas¸, M.; Dilaver, M.; Koyuncu, I˙. Ceramic membrane overview and applications in textile industry: A review. Water Sci. Technol.2021, 84, 1059–1078. [CrossRef] [PubMed]103. López, J.; Reig, M.; Gibert, O.; Cortina, J.L. Recovery of sulphuric acid and added value metals (Zn, Cu and rare earths) fromacidic mine waters using nanofiltration membranes. Sep. Purif. Technol. 2019, 212, 180–190. [CrossRef]
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rare earth elements (REEs)
polymer inclusion membrane (PIM)
ion-imprinted membrane (IIM)
nanocomposite membrane
solid membrane
Rare Earth Elements Recovery Using Selective Membranes via Extraction and Rejection
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