Application of polymer-based membranes containing ionic liquids in membrane separation processes: a critical review
-
Edyta Rynkowska
Abstract
The interest in ionic liquids, particularly in polymerizable ionic liquids, is motivated by their unique properties, such as good thermal stability, negligible vapor pressure, and wide electrochemical window. Due to these features ionic liquids were proposed to be used in the membrane separation technology. The utilization of conventional ionic liquids is, however, limited by their release from the membrane during the given separation process. Therefore, the incorporation of polymerizable ionic liquids may overcome this drawback for the industrial application. This work is a comprehensive overview of the advances of ionic liquid membranes for the separation of various compounds, i.e. gases, organic compounds, and metal ions.
1 Introduction
Membrane techniques are widely applied nowadays thanks to their advantages over classical separation methods, such as good separation selectivity, lower energy consumption, possible utilization at ambient temperature, and moderate pressure (Jönsson and Mathiasson 1999, Smitha et al. 2004, Acharya et al. 2008, Shi et al. 2015). Membrane is the most important component in each membrane separation process, and therefore research on the improvement of membrane separation and transport properties is being intensively carried out. In order to enhance the membrane efficiency, membrane materials are modified with various additives such as zeolites or silica, metal ions or metal ion clusters, metal-organic frameworks (MOFs), and more recently with ionic liquids (ILs).
ILs are salts composed of the organic cation and inorganic or organic anion with melting point usually lower than 100°C. Room temperature ionic liquids (RTILs) are the class of ILs which are liquids at room temperature due to the large size of ions. A cation-anion pair of ILs can be combined in unlimited configuration, because of the variety of possible ions (Figure 1, Table 1). However, the type of chosen cation and anion has a significant impact on the IL properties such as hydrophobic/hydrophilic nature, melting point, viscosity, and ability of solvation (Hassan Hassan Abdellatif et al. 2016, Łuczak et al. 2016b, Lynam et al. 2016, Wang et al. 2016). Therefore, such ILs are commonly called “task-specific ionic liquids” (Armand et al. 2009, Eastman et al. 2010, Mahurin et al. 2011, Noble and Gin 2011, Yoon et al. 2011, Yue et al. 2011, Łuczak et al. 2016a). ILs can be characterized by numerous properties: good thermal stability, high ionic conductivity, negligible vapor pressure (Yoon et al. 2011, Yang et al. 2014), low melting point, and high viscosity (Liew et al. 2014a). Moreover, features of ILs, such as non-flammability (Liew et al. 2014a) and electrochemical stability (Liew et al. 2014b), can also be distinguished.
Chemical structure of cations and anions commonly used to form ionic liquids.
Abbreviations/commercial and chemical names of ionic liquids introduced in this review.
| Chemical name | Abbreviation/commercial name | Reference |
|---|---|---|
| Ammonium-based ILs | ||
| Diethylmethylammonium bis(trifluoromethane sulfonyl)amide | [DEMA][Tf2N] | (Lee et al. 2010) |
| Diethylmethylammonium trifluoromethanesulfonate | [DEMA][TfO] | (Lee et al. 2010) |
| Methyl trioctyl ammonium chloride | [MTOA][Cl] | (Hernández-Fernández et al. 2016) |
| Tetrabutylammonium glycinate | [N4444][Gly] | (Kasahara et al. 2016) |
| Tetrabutylammonium heptadecafluorooctanesulfonate | [NBu4][(PFOc)SO3] | (Pereiro et al. 2013) |
| Tetramethylammonium glycinate | [N1111][Gly] | (Kasahara et al. 2016) |
| Tetrapropylammonium tetracyanoborate | [Pr4N][B(CN)4] | (Izák et al. 2008b) |
| Tricaprylmethylammonium di(2-ethylhexyl)orthophosphinate | [A336][P507] | (Chen and Chen 2016) |
| Trioctylmethylammonium chloride | [A336][Cl]; Aliquat 336 | (Pospiech 2014) |
| Hydrazinium-based Ils | ||
| 1,1,1-Trimethylhydrazinium glycinate | [aN111][Gly] | (Kasahara et al. 2016) |
| Imidazolim-based Ils | ||
| 1-(3-Aminopropyl)-3-methyl-imidazolium tetrafluoroborate | [APMIM][BF4] | (Lu et al. 2014) |
| 1-(Silylpropyl)-3-methyl-imidazolium hexafluorophosphate | [SPMIM][PF6] | (Perdikaki et al. 2012) |
| 1-[n-(Methacryloyloxy)alkyl]-3-methylimidazolium bromides | [MAAMIM][Br] | (Põhako-Esko et al. 2013) |
| 1-Allyl-3-butylimidazilium bis(tri-fluoromethane sulfonyl)imide | [ABIM][TFSI] | (Uragami et al. 2016) |
| 1-Benzyl-3-butylimidazolium tetrafluoroborate | [BBIM][BF4] | (Kohoutová et al. 2009) |
| 1-Butyl-3-(3-hydroxy-2-methylpropyl)imidazolium hexabromidechlorogadolinium | [C11H21N2O]3[GdCl3Br3] | (Daniel et al. 2016) |
| 1-Butyl-3-methylimidazolium methanesulfonate | [BMIM][CH3SO3] | (Chen et al. 2012) |
| 1-Butyl-3-methylimidazolium acetate | [BMIM][Ac] | (Grünauer et al. 2015) |
| 1-Butyl-3-methylimidazolium bis(trifluoromethanesulfonimide) | [BMIM][Tf2N] | (Marcilla et al. 2006) |
| 1-Butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide | [BMIM][TFSI] | (Thanganathan and Nogami 2015) |
| 1-Butyl-3-methylimidazolium bromide | [BMIM][Br] | (Marcilla et al. 2006) |
| 1-Butyl-3-methylimidazolium chloride | [BMIM][Cl] | (Liew et al. 2014b, 2015) |
| 1-Butyl-3-methylimidazolium hexafluorophosphate | [BMIM][PF6] | (Perdikaki et al. 2012, Dong et al. 2015, Grünauer et al. 2015) |
| 1-Butyl-3-methylimidazolium tetrachloroferrate | [BMIM][FeCl4] | (Daniel et al. 2016) |
| 1-Butyl-3-methylimidazolium tetrafluoroborate | [BMIM][BF4] | (Izák et al. 2005, Yongquan et al. 2012, Lu et al. 2014, Dong et al. 2015, Ong and Tan 2016) |
| 1-Decyl-4-methylimidazole | DMIM | (Ulewicz and Radzyminska-Lenarcik 2014) |
| 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amid | [EMIM][TFSA] | (Gu and Lodge 2011) |
| 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide | [EMIM][Tf2N] | (Bara et al. 2008c, Hudiono et al. 2011, Grünauer et al. 2015, Singh et al. 2016) |
| 1-Ethyl-3-methylimidazolium dicyanoamide | [EMIM][DCA] | (Grünauer et al. 2015, 2016, Lam et al. 2016) |
| 1-Ethyl-3-methylimidazolium tetracyanoborate | [EMIM][TCB] | (Grünauer et al. 2016) |
| 1-Ethyl-3-methylimidazolium tetrafluoroborate | [EMIM][BF4] | (Põhako-Esko et al. 2013, Thanganathan and Nogami 2015, Lam et al. 2016) |
| 1-H-3-Methylimidazolium bis(trifluoromethanesulfonyl)imide | [HMIM][Tf2N] | (Eguizábal et al. 2013) |
| 1-Octyl-3-methylimidazolium hexafluorophosphate | [OMIM][PF6] | (Hernández-Fernández et al. 2016) |
| 1-Octyl-3-methylimidazolium tetrachloroferrate | [OMIM][FeCl4] | (Daniel et al. 2016) |
| 1,3-Di(3-methylimidazolium)propane bis(trifluoromethylsulfonyl)imide | pr[MIM]2[Tf2N]2 | (Shahkaramipour et al. 2014) |
| Phosphonium-based Ils | ||
| Bis(2,4,4-trimethylpentyl)phosphinic acid | Cyanex 272 | (Rodríguez de San Miguel et al. 2008, Pospiech and Chagnes 2015) |
| Bis(2,4,4-trimethylpentyl)monothiophosphinic acid | Cyanex 302 | (Costache et al. 2014) |
| Di(2-ethylhexyl)phosphoric acid | D2EHPA | (Costache et al. 2014) |
| Tetraoctylphosphonium oleate | [P8888][oleate] | (Parmentier et al. 2016) |
| Trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate | QPCy272; Cyphos IL 104 | (Regel-Rosocka et al. 2012) |
| Trihexyl(tetradecyl)phosphonium bromide | QPBr; Cyphos IL 102 | (Nowak et al. 2010, Matsumoto et al. 2011) |
| Trihexyl(tetradecyl)phosphonium chloride | QPCl; Cyphos IL 101 | (Regel-Rosocka 2009, Nowak et al. 2010, Regel-Rosocka et al. 2012) |
| Trihexyl(tetradecyl)phosphonium hexachlorogadolinium | [P6,6,6,14][GdCl6] | (Albo et al. 2012) |
| Trihexyl(tetradecyl)phosphonium tretrachlorocobalt | [P6,6,6,14][CoCl4] | (Albo et al. 2012) |
| Trihexyl(tetradecyl)phosphonium tretrachloroferrate | [P6,6,6,14][FeCl4] | (Albo et al. 2012) |
| Trihexyl(tetradecyl)phosphonium tretrachloromanganese | [P6,6,6,14][MnCl4] | (Albo et al. 2012) |
| Pyridinium-based ILs | ||
| 1-Ethyl-3-methylpyridinium perfluorobutanesulfonate | [EtMepy][(PFBu)SO3] | (Pereiro et al. 2013) |
| Ammonium-based polymerizable ionic liquids | ||
| Poly([2-(methylacryloyloxy)ethyl]trimethylammonium) chloride | poly[META][Cl] | (Samadi et al. 2010) |
| Imidazolium-based polymerizable ionic liquids | ||
| Poly(1-styrenemethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) | poly[SMIM][Tf2N] | (Singh et al. 2016) |
| Poly(1-vinyl-3-ethyl-imidazolium) bis(trifluoromethane sulfonyl)amide | poly[ViEtIm][Tf2N] | (Marcilla et al. 2006) |
| Poly(1-vinyl-3-ethyl-imidazolium) bromide | poly[ViEtIm][Br] | (Marcilla et al. 2006) |
| Poly(1-vinyl-3-ethyl-imidazolium) tetrafluoroborate | poly[ViEtIm][BF4] | (Marcilla et al. 2006) |
Due to their unique properties, ILs are used in order to tailor the separation properties of the developed membranes for metal ion separation (Agreda et al. 2011, Petra and Katalin 2011, Zhang et al. 2011, Guisao and Romero 2015), gas separation (Krull et al. 2008, Kebiche-Senhadji et al. 2011, Petra and Katalin 2011, Bakonyi et al. 2013, Yuan et al. 2013, Dahi et al. 2014, Martinez-Palou and Luque 2014, Ansaloni et al. 2015), pervaporation (Petra and Katalin 2011, Kárászová et al. 2014), and fuel cells (Lu et al. 2009, Padilha et al. 2010, Dharaskar et al. 2013a,b, van de Ven et al. 2013, Liu et al. 2014, Shaplov et al. 2015, Zhang et al. 2015).
The combination of ILs with the polymer membrane leads to the creation of supported liquid membranes (SLMs), polymer inclusion membranes (PIMs), or facilitated transport membranes (FTMs), where IL is entrapped in the membrane structure. The SLM is composed of a porous solid membrane matrix (polymer or ceramic) filled with the organic phase (solvent or IL) (Agreda et al. 2011). The PIM consists of a carrier (extractant), polymer matrix (mainly cellulose triacetate – CTA or poly(vinyl chloride) – PVC) and the plasticizer (Almeida et al. 2012). The FTM possesses a membrane polymer matrix with the incorporated selective carrier. The carrier ensures the reversible reaction between its functional groups and separated compound on the basis of carrier-mediated transport, which results in the facilitated separation (Deng and Hägg 2010).
The application of ILs in membranes used in fuel cells, pervaporation, and gas separation processes is somehow limited due to the losses of the unbound IL in the course of the exploitation (Izák et al. 2006b, Samadi et al. 2010, Gu and Lodge 2011, Bernardo et al. 2012, Friess et al. 2012, Yasuda et al. 2012, Cascon and Choudhari 2013, Jansen et al. 2013, Díaz et al. 2014a,b, 2015, Dong et al. 2015, Liew et al. 2015). In order to avoid leaching of the IL from the membrane during the process, different approaches have been studied. One of the approaches is a creation of the ionic gels consisting of networks of polymer swollen with IL (Lodge 2008, Imaizumi et al. 2012). Ionic gels possess the tunable mechanical properties and high ionic conductivity in order of 10−1–10−2 S cm−1 (Díaz et al. 2015). However, the simple ion gels applied as a membrane material in gas separation do not withstand the applied pressure (Lodge 2008). This drawback can be overcome by the polymerization of ion gels which should result in the increase of the attraction between ions (Lodge 2008). Another approach is the use of polymerizable ionic liquid (PIL) monomers (Shaplov et al. 2011, Li et al. 2013, Díaz et al. 2014a, 2015). PILs can be used to build an interpenetrating polymer-ionic liquid network by the in situ polymerization method (Murakami et al. 2007, Takegawa et al. 2009). On the other hand, PIL-based membranes can be produced by the direct polymerization of PIL monomers (Bara et al. 2007, Cowan et al. 2016).
The functional groups of PILs, such as acrylate, vinylbenzyl, and N-vinylimidazolium (Figure 2), can be polymerized via free radical polymerization or UV photopolymerization (Takegawa et al. 2009, Kadokawa 2011, Díaz et al. 2015, Lemus et al. 2015). The polymerization of ILs limits the loss of IL from the membrane; however, it simultaneously decreases the ions mobility and increases the glass transition temperature, thus decreasing the ionic conductivity from about 10−2 S cm−1 (which is an usual order of ionic conductivity of IL) to about 10−6 S cm−1 (Marcilla et al. 2006). This drawback can be overcome by the simultaneous incorporation of both PILs and non-PILs into the membrane structure (Marcilla et al. 2006, Põhako-Esko et al. 2013, Díaz et al. 2014b). The advantages of PIL are similar to conventional RTIL, i.e. the enhanced stability, better processability, improved flexibility, and durability (Díaz et al. 2014a, Jue and Lively 2015).
Functional groups commonly used in polymerizable ionic liquids.
This work is an overview of the advances in membrane technology based on ILs for the gas and liquid mixture separation, metal ions separation, as well as for fuel cells. This review will show the promising approaches to improve the separation effectiveness of the membranes using RTILs and PILs.
2 Separation of metal ions
Separation of metal ions can be carried out by adsorption of metal ions on resins, liquid-liquid extraction, or membrane separation processes using SLMs and PIMs. Liquid-liquid extraction is a conventional separation technique using two immiscible (aqueous and organic) phases. The organic phase traditionally consists of volatile organic compounds (VOCs), which are flammable and toxic (Zhao et al. 2005). ILs, thanks to their safe and environmentally friendly properties, are widely investigated as potentially promising “green” extracting agents for metal ion separation processes (Zhao et al. 2005). In general, the removal of metal ions from aqueous solution requires the hydrophobic ILs (Zhao et al. 2005, Nowak et al. 2010, Lee 2012). IL based on the hydrophobic fatty acid (tetraoctylphosphonium oleate) was investigated for continuous metal ion extraction of cobalt(II) ions from Co(II)/Na(I) and Ca(II)/Co(II)/K(I) mixtures (Parmentier et al. 2016). The efficiency of the extraction was found to be dependent on the contact time of the IL, tetraoctylphosphonium oleate ([P8888][oleate]). The Co(II) ion extraction using tetraoctylphosphonium oleate IL was efficient over time of experiment, i.e. up to 3 months. However, it was indicated that the IL-based metal ion separation process is not economical in comparison to ion-exchange resins, mainly due to the fact that the application of ILs requires high volumes of the stripping solution (Parmentier et al. 2016). The operational costs of the systems based on ILs were about 14 times higher than those for the systems using ion-exchange resin (Parmentier et al. 2016). Hence, the removal of metal ions using IL immobilized membranes has been developed as the efficient method of separation.
The separated metal ions are transported from the feed to the stripping phase through the solvent or carrier immobilized in the porous membrane structure. The mechanism of the metal ion transport in the case of membrane-based separation technology depends on the nature of the extractant. In the case of the membranes with cation exchange nature and possessing quaternary ammonium salts, the counter-transport takes place, namely the metal ions separated from the feed and the counter-ions present in the stripping solution are transported in the opposite directions. The counter-transport is driven by the difference of the counter-ion concentrations between the feed and the stripping phase (de Gyves and de San Miguel 1999, Agreda et al. 2011). For the basic and solvation extractants the co-transport occurs, and, hence, the metal ion and co-ions are transported in the same directions. The driving force of the co-transport is the gradient of co-ion and metal ion concentration (de Gyves and de San Miguel 1999, Agreda et al. 2011).
The review of ILs applied for heavy metal ion extraction and membrane separation from aqueous solutions was recently published by Pospiech and Kujawski (2015) and constitutes the comprehensive knowledge about the last trends in metal ion separation.
2.1 SLMs and PIMs
In order to reduce the amount of IL in the extracting phase, SLMs (de Gyves and de San Miguel 1999, Fortunato et al. 2005, Venkateswaran et al. 2007, Rodríguez de San Miguel et al. 2008, Selvam et al. 2012) and PIMs were developed for the extraction of metal ions (Nghiem et al. 2006, Fontàs et al. 2007, Rodríguez de San Miguel et al. 2008, Mohapatra et al. 2009, Upitis et al. 2009, Arous et al. 2011, Gherasim et al. 2011, Almeida et al. 2012, Pospiech 2014, 2015a) (Table 2). The application of SLMs in metal ion separation revealed that the RTILs in SLMs were gradually removed from the membrane pores during the separation process (Nghiem et al. 2006, Karkhanechi et al. 2015). In order to minimize the leakage of IL from the membrane structure, PIMs with ILs were developed. The IL is incorporated into the porous support of SLM by capillary forces, while ILs in PIMs are doped into the dense polymer support (CTA or PVC) which allows us to reduce the losses of IL. Thus, an interest in PIMs has grown significantly, as this type of membranes possesses enhanced membrane stability and longer lifespan compared to SLMs (Nghiem et al. 2006, Ocampo et al. 2009, Pospiech 2015b). Separation of metal ions using SLMs and PIMs has been widely developed during the past few decades thanks to the energy saving and selectivity improvement, lower cost and simpler operation over the conventional liquid-liquid extraction (de Gyves and de San Miguel 1999, Nghiem et al. 2006, Almeida et al. 2012, Hopkinson et al. 2014). The asymmetric PIM based on poly(vinylidene fluoride) (PVDF) as a host polymer and containing tricaprylmethylammonium di(2-ethylhexyl)orthophosphinate ([A336][P507]) IL was studied in the separation of lutetium(III) cations (Chen and Chen 2016). The investigated PIM was prepared without a plasticizer as the previous studies revealed the lack of the plasticizer influence on the efficiency of the lutetium(III) ion separation (Chen and Chen 2016). The addition of IL [A336][P507] improved the crystalline properties of PVDF, as the increase of the crystallization temperature from 126.9°C to 131.3°C and the decrease of the enthalpy of crystallization from 42.49 to 27.16 J g−1 were revealed. IL acted as a nucleating agent, and thus the PVDF chain segments were enhanced to rearrange the crystal lattice. The transport of the lutetium(III) ions was favorable from the membrane side with small pores to the side with large pores, which led to the prevention of the retention of a transported complex inside the membrane. Table 2 summarizes the ILs used as metal carriers in SLMs and PIMs.
Ionic liquids used as metal carriers in SLMs and PIMs.
| Ionic liquid | Type of membrane | Polymer material | Separated metal ions | Reference |
|---|---|---|---|---|
| Cyphos IL101 | BLM | – | Fe(III) from Ni(II) | (Kogelnig et al. 2010) |
| D2EHPA/Cyanex 302 | BLM | Cr(III), Mn(II), and Zn(II) from aqueous solutions | (Costache et al. 2014) | |
| D2EHPA | SLM | PTFE | Cu(II) from copper plating wastewater | (Venkateswaran et al. 2007) |
| DMIM (1-decyl-4-methylimidazole) | SLM/PIM | Zn(II), Cd(II), Co(II), and Ni(II) from aqueous chloride solution | (Ulewicz and Radzyminska-Lenarcik 2014) | |
| Cyphos IL104 | PIM | CTA | Cd(II) from aqueous chloride solutions | (Pospiech 2015c) |
| Aliquat 336 | PIM | CTA | Zn(II) and Cu(II) | (Pospiech 2014) |
| Cyphos IL 101/Cyphos IL 104 | PIM | CTA | Cd(II) and Cu(II) from aqueous solutions | (Pospiech 2015a) |
| Cyanex 272 | PIM | CTA | In(III) | (Rodríguez de San Miguel et al. 2008) |
| Aliquat 336 | PIM | PVC | Cd(II) and Cu(II) | (Upitis et al. 2009) |
| D2EHPA/TOPO | PIM | CTA | Pb(II) and Cd(II) from aqueous nitrate solution | (Arous et al. 2011) |
| [A336][P507] | PIM | PVDF | Lu(III) | (Chen and Chen 2016) |
BLM, Bulk liquid membrane, PTFE, polytetrafluoroethylene.
According to the presented studies, it can be seen that the separation of metal ions using the supported ionic liquid membranes (SILMs) or PIMs is a popular research area; however, its development reached the limit. SILMs are still far from the industrial application due to their poor lifespan and gradual loss of IL during the process. More attention is paid to PIMs which usually possess better membrane stability and reduce the leakage of the IL from the membrane. In terms of tested RTILs, the commercial ILs, such as Cyphos or Cyanex, received the highest interest in metal ion separation and the inconsiderable interest in the novel ionic ILs has been noticed.
3 Gas separation
The separation of binary gas mixtures can take place using both non-porous and porous membranes. In general, the driving force of the separation is the difference in the partial pressures of gas between two sides of the membrane. However, the mechanism of gas separation strongly depends on the membrane morphology. In the case of porous membranes, different mechanisms can be distinguished depending of the membrane porosity: Knudsen’s diffusion, molecular sieving, Poiseuille flow, and/or capillary condensation (Bum Park et al. 2013). The separation in dense membranes is based on the solution-diffusion model involving preferential solubility of a given gas in the upstream side of the membrane, its diffusivity through the membrane, and gas desorption at the downstream side (Wijmans and Baker 1995, Yampolskii 2012). The efficiency of the separation is determined by the gas solubility and diffusivity through the membrane. Ceramic porous membranes were used for the uranium (235U) isotope enrichment for military application (Hoek and Tarabara 1999). Nowadays, porous materials are used as a supporting membrane matrix characterized by a narrow small pore size distribution, in order to stabilize the incorporated gas carriers, e.g. IL in SLMs (Grünauer et al. 2015, 2016).
Among the polymers used for the preparation of membranes applied in gas separation are polysulfone, phenylene oxide, cellulose acetate, polyimides (PI), PVDF, polyethersulfone (PES), and polyacrylonitrile (PAN) (Pinnau and Freeman 1999, Jue and Lively 2015, Grünauer et al. 2016). In order to improve the selectivity and transport properties of the polymer membranes, ILs were incorporated into a polymer structure, which resulted in the development of the SILMs (Luis et al. 2009, Neves et al. 2010c, 2012, Adibi et al. 2011, Malik et al. 2011, Dai et al. 2016), polymerized ionic liquid membranes (Bara et al. 2007, Bhavsar et al. 2014, Dai et al. 2016, Shaplov et al. 2016), mixed matrix membranes (MMMs) (Hudiono et al. 2011, Rezakazemi et al. 2014), and FTMs (Kasahara et al. 2012, 2016).
The removal of acid gas, particularly carbon dioxide from natural gases, is one of the most widely investigated membrane separation processes. The sweetening of natural gas has gained great attention due to the environmental protection problems referring to the global warming. The investigation regarding the CO2 capture has been carried out since the early 1980s. Yampolskii (2012) focused on the membrane material development characterized by the high permeability P(CO2) and separation factors α(CO2/N2). The studies of SILMs containing RTILs revealed that SILMs can be efficiently applied in the separation of CO2 from CH4 and CO2 from N2 (Blanchard et al. 1999, Mahurin et al. 2010, 2011, Samadi et al. 2010, Gu and Lodge 2011, Hudiono et al. 2011, Malik et al. 2011, Neves et al. 2012, Nguyen et al. 2013, Cheng et al. 2014, Kárászová et al. 2014, Shahkaramipour et al. 2014, Grünauer et al. 2015, Karkhanechi et al. 2015, Kasahara et al. 2016, Singh et al. 2016, Friess et al. 2017).
In general, the performance of a given membrane in terms of the selectivity and the permeability for the separated gases is evaluated with respect to the Robeson plot (Robeson 2008). The characteristic feature of the Robeson plot is the empirically defined upper bound based on the experimental results for the polymeric dense membranes obtained for the multitude pairs of the following gases: He, H2, O2, N2, CO2, and CH4. The upper bound is determined by the permeabilities (Pi ) (Eq. 1) and the selectivities (αi/j =Pi/Pj ) (Eq. 2) corresponding to the given pair of gases. The permeability of a gas refers to the flux at a stationary state (Jstat) normalized by the membrane thickness (L) obtained for the given pressure difference (Δp) between two sides of the membrane (Jue and Lively 2015):
The membrane selectivity (αij ) is defined as the permeability ratio obtained for two different gases investigated in the same membrane, which equals the solubility and diffusivity ratios (Eq. 2). In general, the gas permeation through the membrane material is described by the solution-diffusion mechanism; hence, the membrane permeability is determined by the solubility (S) and diffusivity of the gas in the tested membrane (Eq. 3) (Gu and Lodge 2011, Yampolskii 2012):
The exceeding of the upper bound became a target in the novel membrane development for gas separation processes (Robeson 2008, Robeson et al. 2009).
As was mentioned, the gas separation membrane efficiency is often presented as the Robeson plot and compared with the “upper bound.” However, the Robeson plot refers to isothermal measurement conditions. Regarding the fact that the gas separation studies discussed in this work were performed at different temperatures, the results are presented in Tables 3 and 4. These tables present the CO2 permeability and ideal selectivity values taken from the literature data introduced in this review for the CO2/N2 and CO2/CH4 gas pairs, respectively. The gas separation efficiency concerns the PIL-based membranes and membranes impregnated with ILs.
CO2 permeability and ideal CO2/N2 selectivity of PIL-based membranes and membranes containing ionic liquids as a gas carrier.
| Ionic liquid | Polymer material | CO2 permeability (Barrer) | CO2/N2 selectivity | Temperature (°C) | Reference |
|---|---|---|---|---|---|
| [EtMepy][(PFBu)SO3] | PES | 897 | 12.3 | 21 | (Pereiro et al. 2013) |
| [HMIM][Tf2N] | PTFE | 600 | 18 | 20 | (Nguyen et al. 2013) |
| [aN111][Gly] | PTFE | 600 | 20 | 100 | (Kasahara et al. 2016) |
| [TBzPBI-BuI][BF4] | PIL-based membrane | 31.5 | 17.6 | 35 | (Rewar et al. 2016) |
| [EMIM][BF4] | CTA | 20 | 28 | 35 | (Lam et al. 2016) |
| [P6,6,6,14][GdCl6] | PVDF | 176.35 | 30.80 | 25 | (Albo et al. 2012) |
| Styrene-based system containing methyl group | PIL-based membrane | 9.2 | 32 | 20 | (Bara et al. 2007) |
| [EMIM][TFSA] | PVDF | 985 | 39 | – | (Gu and Lodge 2011) |
| [EMIM][Tf2N] | PIL-based membrane | 44 | 39 | 22 | (Bara et al. 2008c) |
| [EMIM][Tf2N] | Styrene | 72.1 | 42.4 | 23 | (Hudiono et al. 2011) |
| [EMIM][DCA] | PAN | 41.514 | 58 | 30 | (Grünauer et al. 2016) |
| [EMIM][DCA] | PS-b-P4VP | 600 | 65 | 30 | (Grünauer et al. 2015) |
CO2 permeability and ideal CO2/CH4 selectivity of PIL-based membranes and membranes containing ionic liquids as a gas carrier.
| Ionic liquid | Polymer material | CO2 permeability (Barrer) | CO2/CH4 selectivity | Temperature (°C) | Reference |
|---|---|---|---|---|---|
| [EtMepy][(PFBu)SO3] | PES | 897 | 6.6 | 21 | (Pereiro et al. 2013) |
| [EMIM][TFSA] | PVDF | 985 | 19 | – | (Gu and Lodge 2011) |
| [TBzPBI-BoI][BF4] | PIL-based membrane | 31.5 | 19.9 | 35 | (Rewar et al. 2016) |
| [EMIM][Tf2N] | Epoxy-amine | 525 | 20 | 25 | (Friess et al. 2017) |
| [EMIM][Tf2N] | PIL-based membrane | 44 | 27 | 22 | (Bara et al. 2008a) |
| pr[MIM]2[Tf2N]2 | Alumina | 190 | 27.1 | 27 | (Shahkaramipour et al. 2014) |
| [EMIM][Tf2N] | Styrene | 72.1 | 32.2 | 23 | (Hudiono et al. 2011) |
| Styrene-based system containing methyl group | PIL-based membrane | 9.2 | 39 | 20 | (Bara et al. 2007) |
| [EMIM][BF4] | CTA | 20 | 42 | 35 | (Lam et al. 2016) |
| poly[SMIM][Tf2N] and [EMIM][Tf2N] | PIL-IL-zeolite | 260 | 90 | 25 | (Singh et al. 2016) |
3.1 Gas separation membranes containing RTILs
RTILs are widely used in gas separation thanks to possible tailoring of gas solubility and selectivity by an appropriate exchange of cation and/or anion in IL or by an incorporation of chosen functional groups (Bara et al. 2008b, Luis et al. 2009, Voss et al. 2009, Gu and Lodge 2011, Banu et al. 2013, Liang et al. 2014, Zhou et al. 2014, Kanakubo et al. 2016, Zhang et al. 2016). ILs possess a preferential solubility of CO2 over N2 and CH4 (Neves et al. 2010c, 2012, Erdni-Goryaev et al. 2012, 2014, Lam et al. 2016, Singh et al. 2016). Very low volatility and the non-volatile nature of ILs can prevent the loss of solvent by evaporation in comparison with the conventional liquid membranes. However, due to the fact that IL is held in pores of SILMs by weak capillary forces, the loss of IL due to the drop of pressure applied in gas separation is observed (Gu and Lodge 2011). RTIL mixed with the chemically crosslinked PIL or poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) allows us to avoid the losses of RTIL, as well as to enhance the mechanical strength and gas transport properties (Bara et al. 2008c, 2009, Gu and Lodge 2011, Jansen et al. 2011). The composite membranes containing PIL (1-[(4-ethenylphenyl)methyl]-3-alkylimidazolium bis(trifluoromethane)sulfonimide) and 20 mol % of RTIL (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][Tf2N]) resulted in an increase of the ideal CO2 permeability from 9.2 to 44 Barrer compared to pristine PIL (Bara et al. 2008c). Moreover, the incorporation of [EMIM][Tf2N] increased the ideal CO2/N2 selectivity from 32 to 39 and decreased the ideal CO2/CH4 selectivity from 29 to 27 (Bara et al. 2008c). The addition of [EMIM][Tf2N] up to 40 wt.% to PVDF-HFP resulted in a significant decrease of Young’s modulus of one order of magnitude and of the break strength of about 20 MPa compared to the pristine polymer. These results reveal that the addition of [EMIM][Tf2N] provokes the plasticization of PVDF-HFP as the decrease of the polymer crystallinity was confirmed by the X-ray and differential scanning calorimetry analysis (Jansen et al. 2011).
The modification of a porous membrane by the IL was presented by Perdikaki et al. (2012). In this case, IL (1-butyl-3-methyl-imidazolium hexafluorophosphate [BMIM][PF6]) in a functionalized (1-(silylpropyl)-3-methyl-imidazolium hexafluorophosphate [SPMIM][PF6]) or a non-functionalized form was grafted onto the porous siliceous support, and ultrathin layers of IL were formed. The functionalized (silylated) IL had high affinity to the hydroxyl groups of the porous support surface, and thus IL was covalently grafted to the surface with anions facing the core of the pores. Thanks to that, the transport pathway was created, which facilitated the gas diffusion through the membrane along the pores between the anions, whereas the non-functionalized IL was randomly arranged in the support pores; therefore, the diffusion of the CO2 and CO was hindered, and the values of gas diffusion coefficient were two orders of magnitude lower than those of the functionalized IL (Perdikaki et al. 2012).
SILM prepared using porous PVDF polymer filled with RTIL possessing 1-butyl-3-methylimidazolium cation was studied for CO2 removal from lighter gases. The investigated membrane was characterized by the increased stability and good chemical affinity between the PVDF porous support and the chosen RTIL. An increase of the alkyl chain length in RTIL results in an increase of the gas permeability for all investigated gases, i.e. H2, O2, N2, CH4, and CO2, due to the better gas solubility (Bara et al. 2007, Neves et al. 2010c). On the other hand, the exchange of the anions in RTIL among [Tf2N]−, [BF4]−, and [PF6]− revealed that the permeability of all studied gases was the highest for RTIL with Tf2N− because of the lowest IL viscosity, whereas CO2 permeability was almost one order of magnitude higher than that for other investigated gases (Neves et al. 2010c).
Grünauer et al. (2016) compared two coating techniques, namely, spin coating and continuous dip coating, in order to choose the efficient method leading to thin selective layer of IL enabling to achieve high SLM permeance based on PAN. It was shown that the IL films obtained by spin coating on porous PAN substrate possessed defects and were heterogeneous. The investigation of dip coating method revealed that the detect-free coating was obtained only for membranes with narrow pore size distribution, i.e. the 1-ethyl-3-methylimidazolium tetracyanoborate [EMIM][TCB] IL. The time-lag experiments showed that membrane possessing average pore size equal to 10 nm and the surface porosity equal to 13.7% has a pinhole-free structure and is characterized by the normalized CO2 permeability equal to 41.5 Barrer and CO2/N2 selectivity of 58 (Grünauer et al. 2016). In general, it was indicated that for obtaining the defect-free flat sheet SLM, the pore size, viscosity and concentration of IL, and contact angle should be taken into consideration.
Grünauer et al. (2015) also investigated the isoporous polystyrene-block-poly(4-vinylpyridine) diblock copolymer (PS-b-P4VP)-based SLM containing 1-ethyl-3-methylimidazolium dicyanoamide [EMIM][DCA], 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [EMIM][Tf2N], 1-butyl-3-methylimidazolium acetate [BMIM][Ac] as well as reference IL – 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6] for the separation of CO2 from N2. The investigated SLM possessed high stability, whereas the membrane based on PS78-P4VP22 (with molecular weight 78,000 g mol−1) containing [EMIM][DCA] revealed high permeability and selectivity for CO2/N2 separation equal to about 480 Barrer and 65, respectively.
Another promising approach for improving the membrane efficiency in CO2/CH4 separation is a modification of cellulose ester-based membranes with the ILs (Scholes et al. 2012, Lam et al. 2016). The incorporation of 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) and 1-ethyl-3-methylimidazolium dicyanamide ([EMIM][DCA]) into CTA decreased the glass transition temperature (Tg) of CTA from 198°C (for a pristine CTA membrane) to 11°C (for a membrane containing 50 wt.% of IL). This result was related to the decrease of the CTA crystallinity degree and to the increase of the diffusivity and permeability through the membrane. As a result, CO2 permeability as well as selectivities of CO2/CH4 and CO2/N2 separation increased due to the high solubility of CO2 in IL. It was noticed that CTA containing more than 40 wt.% of [EMIM][BF4] possessed two glass transition temperatures, which reveal the immiscibility and phase separation in the amorphous phase. On the other hand, CTA blended with [EMIM][DCA] has one Tg, which indicates better compatibility of CTA with [EMIM][DCA] than with [EMIM][BF4] (Lam et al. 2016).
Lu et al. (2014) used ILs, 1-butyl-3-methyl-imidazolium tetrafluoroborate ([BMIM][BF4]) and 1-(3-aminopropyl)-3-methyl-imidazolium tetrafluoroborate ([APMIM][BF4]), as absorbents for CO2 capture in the membrane absorption coupling process consisting of the membrane absorption and membrane vacuum regeneration units. In order to decrease the viscosity, the aqueous ILs were used during the coupling process. It was revealed that the critical water content enhancing the CO2 mass transfer was evaluated as a water mole fraction at about 0.6 for [BMIM][BF4] and about 0.35 for [APMIM][BF4]. This result testifies to the fact that the high IL viscosity was observed at the lower water mole fraction for [BMIM][BF4], compared to [APMIM][BF4], thus hindering the CO2 diffusion.
3.2 Gas separation membranes containing other types of ILs
3.2.1 Fluorinated ionic liquids (FILs)
Pereiro et al. (2013) investigated the permeation properties of the SLMs with FILs – tetrabutylammonium heptadecafluorooctanesulfonate [NBu4][(PFOc)SO3] and 1-ethyl-3-methylpyridinium perfluorobutanesulfonate [EtMepy][(PFBu)SO3] toward N2, O2, CO2, and CH4. It was shown that the gas solubility in studied FILs was influenced by the length of fluoroalkyl chains, whereas gas diffusivity was more affected by the size of the gas molecule. In general, the elongation of the fluoroalkyl chains resulted in the increase of IL viscosity, which was attributed to the smaller gas permeability for [NBu4][(PFOc)SO3] in comparison to [EtMepy][(PFBu)SO3]. For example, the permeability of CO2 was equal to 649 and 897 Barrer for [NBu4][(PFOc)SO3] and [EtMepy][(PFBu)SO3], respectively. The gas diffusivity decreased with the increasing size of the molecule and was equal to 1046×1012 m2 s−1 for O2 and 46×1012 m2 s−1 for C3H8.
3.2.2 Magnetic ionic liquids (MILs)
Albo et al. (2012) studied CO2, N2, and air permeabilities for SLMs based on the MIL showing different behavior in the external magnetic field. The hydrophilic and hydrophobic PVDF porous supports and four paramagnetic ionic liquids (phosphonium tretrachlorocobalt [P6,6,6,14][CoCl4], phosphonium tretrachloroferrate [P6,6,6,14][FeCl4], phosphonium tretrachloromanganese [P6,6,6,14][MnCl4], and phosphonium hexachlorogadolinium [P6,6,6,14][GdCl6]) were studied. The membranes containing hydrophobic support and the phosphonium tretrachloroferrate presented the highest value of the CO2 permeability equal to 259.04 Barrer, whereas N2 and air permeability was 10.72 and 12.34 Barrer, respectively.
Daniel et al. (2016) investigated the transport properties of the SILMs with incorporated following MILs: [C11H21N2O]3[GdCl3Br3], [BMIM][FeCl4], and [OMIM][FeCl4] in the absence and the presence of the magnetic field with an intensity of 1.2 T. It was found that the magnetic field enhances the transport ability of SILMs reflected by the increase of the permeability (P) and mass transfer coefficient (K) of solutes, i.e. ibuprofen and α-pinene. The studied membranes containing [C11H21N2O]3[GdCl3Br3] indicated the increase of ibuprofen permeability P from 1.02 to 1.62×10−7 cm2 s−1 and mass transfer coefficient K from 2.7 to 4.3×10−6 cm s−1 without and with application of magnetic field, respectively (Daniel et al. 2016). The membranes investigated for α-pinene transport revealed the raise of the permeability P from 0.37 to 0.56×10−7 cm2 s−1 and mass transfer coefficient K from 0.987 to 1.49×10−6 cm s−1 for membranes containing [BMIM][FeCl4] after exposure to the magnetic field, whereas the membranes incorporated with and [OMIM][FeCl4] showed the increase of permeability P from 0.98 to 1.27×10−7 cm2 s−1 and mass transfer coefficient K from 2.6 to 3.35×10−6 cm s−1 when the magnetic field was applied. It was noticed that the permeability of the investigated solutes is enhanced in the presence of magnetic field as a result of the decrease of the MILs viscosity. Furthermore, it was pointed out that an increase of the α-pinene and ibuprofen solubility in MILs due to the magnetic field presence can also improve the membrane transport properties (Daniel et al. 2016).
3.2.3 Amino acid ionic liquids (AAILs)
AAILs are another type of ILs used for the CO2 separation (Kasahara et al. 2012, 2016, Li et al. 2016). AAILs incorporated into a membrane are known as FTMs and display very good CO2 permeability and CO2/N2 selectivity (Kasahara et al. 2012, 2016). Kasahara et al. (2016) investigated AAILs containing tetrabutylammonium glycinate ([N4444][Gly]), tetramethylammonium glycinate ([N1111][Gly]), and 1,1,1-trimethylhydrazinium glycinate ([aN111][Gly]). The fractional free volume was calculated using molecular dynamics simulation before and after the CO2 absorption in order to evaluate the amount of absorbed gas. The decreasing molecular size of AAIL, obtained by changing the substituents in the ammonium-based cation, reduced the fractional free volume, which affects the increase of the CO2 absorption and the decrease of the N2 absorption. The 1,1,1-trimethylhydrazinium glycinate containing two amino groups revealed higher CO2 absorption than tetramethylammonium glycinate due to the gas absorption by both amino functional groups. The absorption ability of the amino acid groups was also evaluated under humid conditions (Kasahara et al. 2016). The increase of the humidity up to 20% caused the decrease of the AAIL viscosity of about 2 mPa s after the CO2 absorption which was related to the loosely formed hydrogen bond network in the AAIL-CO2 complex. On the other hand, the IL viscosity at a higher humidity level remained almost constant. It was proved that the evaluation of gas absorption properties is important to determine the separation properties of AAIL-FTMs toward CO2.
3.3 Gas separation membranes containing PILs
PILs have also been investigated as the potential alternative for widely used CO2 sorbents, such as zeolites, carbon nanotubes, silica gels, mesoporous molecular sieves, and MOFs (Bara et al. 2008a, Hudiono et al. 2011, Jue and Lively 2015, Tomé et al. 2015, Horne et al. 2015, Dai et al. 2016, Rewar et al. 2016, Singh et al. 2016). It was shown that PILs possess the CO2 absorption capacity 2 times (Bara et al. 2007) or even 6.0–7.6 times (Tang et al. 2005a,b) higher than that of RTILs. The monomers of PILs revealed negligible absorption of CO2 due to their crystalline structure. Samadi et al. (2010) studied the efficiency of the sorbent for the CO2 separation from mixture of gases. The sorbent was prepared by grafting the PIL (poly([2-(methylacryloyloxy)ethyl]trimethylammonium chloride (poly[META][Cl])) nanolayers on macroporous regenerated cellulose (RC) by the surface-initiated atom transfer radical polymerization. The influence of the anion exchange in PIL from [Cl]− to [BF4]−, [CH3SO3]−, and [CF3SO3]− on the CO2 adsorption was investigated (Samadi et al. 2010). The prepared material was examined in terms of the adsorption of pure CO2 and N2. It was shown that the choice of the counter-ion in PIL had no significant role in the CO2 adsorption. The modification of RC with PILs resulted in higher selectivity for CO2 over N2, whereas cellulose without PIL was not CO2 selective (Samadi et al. 2010).
The CO2 separation was improved by an incorporation of PILs containing various anions, e.g. [Tf2N]−, [BF4]−, [Ac]− (Hudiono et al. 2011, Rewar et al. 2016, Singh et al. 2016). It was shown that the thermal stability and the permeability of the membranes depend on the chosen PILs anion. The thermal stability of the membranes varied with the change of anion in the following order: [Tf2N]−>[BF4]−>[Ac]−. PIL possessing [BF4]− showed CO2 permeability and permselectivity higher than that for N2 and CH4. The permeability coefficient for PIL with BF4− for CO2 was equal to 29.8 Barrer, and permselectivity for CO2/CH4 and CO2/N2 was equal to 18.6 and 15.9, respectively (Rewar et al. 2016).
The CO2/CH4 selectivity and CO2 permeability, obtained for MMMs containing PIL (50 wt.% of poly(1-styrenemethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) (poly[SMIM][Tf2N])), IL (20 wt.% of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) [EMIM][Tf2N]), zeolites (30 wt.% of SAPO-34), and 2 wt.% of divinylbenzene as a crosslinker, was equal to 90 and 260 Barrer, respectively (Singh et al. 2016). The investigated MMMs containing a balanced amount of the SAPO-34 and SSZ-13 zeolite particles revealed that CO2/CH4 separation performance is much higher than Robeson’s upper bound 2008 (Robeson 2008, Singh et al. 2016). The MMM containing SAPO-34 with the above-mentioned composition had the storage modulus value higher than 2200 MPa from −20°C to 0°C and this value maintained high up to the glass transition temperature equal to 63°C.
Nowadays, the membrane gas separation is one of the most widely investigated membrane-based research areas focused on the development of the new approaches and improvement of the existing strategies in CO2 capture. The studies on gas separation membranes containing RTIL revealed promising groups of ILs, such as MILs and AAILs used in SILMs. Nevertheless, the application of SILMs is still related to the loss of IL during their exploitation which resulted in the development of the PIL-based membranes. The incorporation of the PIL can enhance the membrane stability and lifespan, and simultaneously, it decreases the gas selectivity and permeability. Based on this knowledge, the successful attempts of the RTILs and PIL blends were tested.
4 Pervaporation
Pervaporation is assigned to separate binary or multicomponent liquid mixtures, such as azeotropes, isomers, and components with close boiling point. During this membrane process the given compounds are preferentially transported through the membrane from the feed to the permeate side in accordance with the solution-diffusion mechanism. The mass transport of permeants is driven by the difference in chemical potentials of separated compounds between two sides of the membrane. Unlike other membrane separation techniques, pervaporation involves a liquid to vapor phase change (Kujawski 1996, 2000, Ong et al. 2014). Hence, the transport in pervaporation is composed of the liquid sorption of the components into the membrane, diffusion of their vapors across the membrane, and desorption at the permeate side. The membranes used in pervaporation should possess a thin dense selective layer allowing us to obtain good efficiency during operation. In order to improve the membrane performance in pervaporative separation of organic-organic and aqueous-organic liquid mixtures, ILs were used to modify the dense and supported membranes (Fadeev and Meagher 2001, Izák et al. 2005, 2006a, 2008a, Kohoutová et al. 2009, Heitmann et al. 2012, Pereiro et al. 2012, Cascon and Choudhari 2013, Dong et al. 2015, Ong and Tan 2015, 2016) (Table 6).
The selective and transport properties of the membranes containing ILs in pervaporative separation of liquid mixtures have been investigated by a number of research groups. Kohoutová et al. (2009) investigated dense polydimethylsiloxane (PDMS)-based membranes containing 0–30 wt.% benzyl-3-butylimidazolium tetrafluoroborate ([BBIM][BF4]) IL, applied for the removal of butanol from aqueous solution. The membrane films were prepared by the spin-coating method using a mixture of PDMS with crosslinking catalyst and [BBIM][BF4]. The constant weight ratio between the polymer and catalyst equal to 9:1 was used. The concentration of butanol was equal to 5 wt.%, wherein at this butanol content the concentration of Clostridium acetobutylicum in fermentation broth starts to decrease. It was shown that an increased content of IL results in an increase of the membrane selectivity and total flux. The separation factor β increased up to 37 for 30 wt.% of IL. However, it was shown that [BBIM][BF4] and PDMS are not compatible. Despite being optically homogeneous, the investigated membranes contained both crystalline and amorphous phases of PDMS and dispersed phase of IL. The incorporation of 1-butyl-3-methyl-imidazolium-tetrafluoroborate [BMIM][BF4] IL into the PVDF-HFP membrane improved the diffusion coefficient of ethyl acetate during pervaporative removal of ethyl acetate from water. The total flux of the pristine PVDF-HFP membrane was equal to 433 g m−2 h−1, whereas the total flux of PVDF-HFP membrane containing 5 wt.% of [BMIM][BF4] was equal to 655 g m−2 h−1 (Kohoutová et al. 2009). At 45°C the separation factor β of the pristine membrane and the membrane with IL increased from 76 to 144 in contact with the ethyl acetate-aqueous mixture containing 4 wt.% of EtAc (Yongquan et al. 2012).
Another type of membrane applied in pervaporation and containing ILs is SLM (Izák et al. 2008a,b, 2009, Matsumoto et al. 2011, Cascon and Choudhari 2013, Martínez-Palou et al. 2014, Ong and Tan 2016). Ong and Tan (2016) studied the SLM with [BMIM][BF4] and poly(vinyl alcohol) (PVA). The membrane was investigated in the pervaporation of ternary azeotrope containing ethyl acetate, ethanol, and water. Prior to pervaporation of a ternary liquid mixture, the binary mixtures (ethyl acetate-water, ethanol-water, and ethyl acetate-ethanol) were investigated in order to study their interactions as well as the interactions of solvents with the SILM. The investigated membranes possess good efficiency of dehydration of the ethyl acetate/ethanol/water azeotrope mixture. The composition of the EtAc/EtOH/H2O feed mixture was equal to 82.6/8.4/9.0 wt.%. At 30°C the separation factor β and the total permeate flux Jt during dehydration were equal to 247 and 385 g m−2 h−1, respectively.
The incorporation of 15 wt.% of IL (tetrapropylammonium tetracyanoborate) into the porous ultrafiltration membrane (pore size 60 nm), which was coated by thin film of PDMS, ensured high stability and selectivity of the SLM. Furthermore, it increased the productivity of C. acetobutylicum during the fermentation of the acetone, butanol, and ethanol by pervaporation at 37°C. The effectiveness of the fermentation product removal was equal to 2.34 g l−1 h−1 (Izák et al. 2008b). Izák et al. (2005) also showed that the use of RTIL [BMIM][BF4] in the PERVAP 2205 membrane shifted the equilibrium of the esterification reaction of (–)-borneol with acetic acid at 60°C toward the formation of the (–)-bornyl acetate. The addition of [BMIM][BF4] allowed the increase of the reaction conversion degree from 22% to 44% due to the selective removal of water from the reaction medium during pervaporation. Uragami et al. (2016) indicated that an increase in the content of hydrophobic IL (1-allyl-3-butylimidazilium bis(tri-fluoromethane sulfonyl)imide ([ABIM][TFSI])) in the poly(methylmethacrylate)-graft-poly(dimethylsiloxane) (PMMA-g-PDMS) membrane resulted in an increase of benzene removal selectivity and permeability during pervaporation because of the high IL affinity toward benzene.
The problem of the IL leakage from SLM pores is also present during the pervaporation process (Izák et al. 2006b, Heitmann et al. 2012, Cascon and Choudhari 2013). One of the solution used to prevent the leaching into the feed/permeate during organophilic pervaporation is the application of an additional coating layer which is also suitable for the pervaporative removal of organic compounds from aqueous solution (Heitmann et al. 2012, Dong et al. 2015, Wang et al. 2016). Dong et al. (2015) prepared the SILM by incorporating ILs based on 1-butyl-3-methylimidazole cation with different anions (BF4− and PF6−) into the porous anodic aluminum oxide (AAOM) support coated with the polyurethane (PU) layer. The impregnated membranes possessed good stability during the pervaporation of the benzene-cyclohexane mixture. The coating of AAOM-IL with PU prevented the leakage of ILs from the membrane pores. The addition of ILs to the AAOM-PU membrane decreased the permeate fluxes. Simultaneously, the separation factor increased from 5 (for a pristine AAOM-PU membrane) to 34 (for the membrane impregnated with 1-butyl-3-methylimidazole hexafluorophosphate).
Matsumoto et al. (2011) studied PIMs based on the PVC membrane doped with several ILs such as Aliquat 336, Cyphos 101, 102, and 104. The membranes were obtained on the hydrophobic PVDF support and applied in the pervaporative separation of butan-1-ol and propan-2-ol from their aqueous solutions. The most efficient IL for the removal of butan-1-ol and propan-2-ol was found to be Aliquat 336. It was pointed out that when the concentration of IL was equal to 60 and 70 wt.%, IL was not leaching from the membrane during pervaporation. However, the membrane films containing more than 70 wt.% of IL were not stable during pervaporation. The highest butan-1-ol flux (26.08 g m−2 h−1) and total flux Jt (1193 g m−2 h−1) were obtained for the membrane containing 70 wt.% of Aliquat 336 for 5 g l−1 of propan-2-ol and butanol concentrations in the feed mixture. Table 5 summarizes the pervaporation efficiencies of membranes containing ILs.
Pervaporative efficiency of the membranes containing ionic liquids.
| Ionic liquid | Polymer material | Separated system | Efficiency | Reference |
|---|---|---|---|---|
| [Pr4N][B(CN)4] | PDMS | Clostridium acetobutylicum fermentation of AcO, BuOH, EtOH | Fermentation products removal: 2.34 g l−1 h−1 | (Izák et al. 2008b) |
| [BMIM][BF4] | PVA (PERVAP 2205) | Removal of water from the esterification reaction of (–)-borneol with acetic acid | Reaction conversion degree: 44% | (Izák et al. 2005) |
| [ABIM][TFSI] | PMMA-g-PDMS | Removal of benzene from water | Sorption selectivity for 20 mol.% of IL: about 1800 | (Uragami et al. 2016) |
| [BMIM][BF4] | PVA | Ethyl acetate, ethanol, and water ternary liquid mixture | Separation factor: 247 | (Ong and Tan 2016) |
| [BMIM][PF6], [BMIM][BF4] | AAOM with PU coating | Benzene from cyclohexane mixture | Separation factor: 34.4 | (Dong et al. 2015) |
| [BBIM][BF4] | PDMS | Butanol from aqueous solution | Separation factor: 37 | (Kohoutová et al. 2009) |
| [BMIM][BF4] | PVDF-HFP | Ethyl acetate from water | Separation factor: 144 | (Yongquan et al. 2012) |
| Aliquat 336, Cyphos IL 101, Cyphos IL 102, and Cyphos IL 104 | PVC | Butan-1-ol and propan-2-ol from the aqueous solution | Separation factor: 7 | (Matsumoto et al. 2011) |
The usage of ILs in pervaporative separation is focused on employing SILMs and PIMs containing RTILs, whereas the application of PIMs is a more promising direction due to the reduced leaching of ILs during exploitation. The butanol recovery from aqueous mixtures using membranes containing ILs is one of the most studied methods; however, it is still beyond the industrial application. Taking into account a small amount of new approaches, pervaporative separation using membrane materials containing IL is a research area which can be developed.
5 Proton exchange membrane fuel cells (PEMFCs)
Fuel cell allows us to convert chemical energy to electrical energy thanks to the redox reaction. The PEMFC is fueled with oxygen, which undergoes the reduction reaction at the cathode, and hydrogen, which is oxidized at the anode. The proton exchange membrane (PEM) is a key component in the PEMFC as it carriers proton from the anode to the cathode. Therefore, membranes for fuel cell applications have to be highly proton conductive as well as low permeable for fuel cross-over (Liew et al. 2014b, Thanganathan and Nogami 2015). Moreover, such membranes should possess a good mechanical strength as well as thermal and chemical stability (Ceynowa et al. 1974, Liew et al. 2014b). The Nafion membrane is a reference for the PEMFC (Neves et al. 2006, 2010a, Martínez de Yuso et al. 2012). However, Nafion shows significant drawbacks, such as decreasing proton conductivity at temperatures higher than 80°C due to the evaporation of water and high price (Lozano et al. 2011, Yang et al. 2014, Kakati et al. 2015, Thanganathan and Nogami 2015). Thus, new membranes enabling us to work under anhydrous conditions and at high temperatures (>100°C) are widely investigated (Li et al. 2003, Ye et al. 2008, Lee et al. 2010, Yi et al. 2011, Eguizábal et al. 2013, Lin et al. 2013, Yang et al. 2014). From this point of view, the use of RTIL as a proton conductor is a very promising approach (Neves et al. 2006, 2010a,b, Martínez de Yuso et al. 2012, Saroj and Singh 2012, Yasuda et al. 2012, Liew et al. 2014b, 2015, Yang et al. 2014, Kakati et al. 2015, Thanganathan and Nogami 2015).
The incorporation of ILs into membranes results in the conductivity and electrochemical resistance values comparable to the typically used PEMs based on perfluorosulfonic acid (Jarosik et al. 2006, Hernández-Fernández et al. 2015, 2016) (Table 6). Hernández-Fernández et al. (2016) described the use of a PIM containing 1-octyl-3-methylimidazolium hexafluorophosphate ([OMIM][PF6]) and methyl trioctil ammonium chloride ([MTOA][Cl]) as a PEM in a microbial fuel cell. The membrane containing 70 wt.% of ammonium-based IL had the maximum power equal to 450 mW m−3 and the yield of the chemical oxygen removal more than 80%.
Conductivity of ionic liquids and ionic liquid-based polymer electrolyte membranes.
| Ionic liquid | Polymer material | Conductivity (S cm−1) | Temperature of experiment (°C) | Reference |
|---|---|---|---|---|
| [BMIM][CH3SO3], [BMIM][BF4] | SPEEK | 8.04×10−2, 1.02×10−1 (for 50% RH); 9.04×10−2, 1.18×10−1 (for 100% RH) | 90 | (Chen et al. 2012) |
| [BMIM][Cl] | PVA | 5.74×10−3 | Ambient temperature | (Liew et al. 2014b) |
| [BMIM][TFSI], [EMIM][BF4] | PVA | 0.83×10−3, 0.58×10−3 | 60 | (Thanganathan and Nogami 2015) |
| [EMIM][BF4], [MAAMIM][Br] | – | 10−4 (for 40% vol/vol [EMIM][BF4]) | – | (Põhako-Esko et al. 2013) |
| Poly[ViEtIm] with [BMIM][Tf2N], [BMIM][BF4], [BMIM][Br] | – | 10−2–10−5 | Room temperature | (Marcilla et al. 2006) |
| Poly(vinylimidazolium-co-3-sulfopropyl acrylate) with anionic spacer | – | 1.2×10−5 | 50 | (Yoshizawa et al. 2002) |
| [MITHn A], [EITHn A], [BITHn A], [EMITHn A] | – | 1.37×10−4 (IL with n=6), 1.1×10−4 (IL-based film) | 30 | (Washiro et al. 2004) |
| [DEMA][TfO], [DEMA][Tf2N] | – | 5×10−2 10−2 | 150 room temperature | (Lee et al. 2010) |
| Poly[2,2-(m-phenylene)-5,5-bibenzimidazole] with 1-H-3-methylimidazolium bis(trifluoromethanesulfonyl)imide | – | 5.4×10−2 | 200 | (Eguizábal et al. 2013) |
It was shown that the membrane based on poly[2,2-(m-phenylene)-5,5-bibenzimidazole] (PBI) with 1-H-3-methylimidazolium bis(trifluoromethanesulfonyl)imide encapsulated in NaY-type large pore zeolite possesses the proton conductivity of 54 mS cm−1 at 200°C for the optimum amount of protic IL and zeolite equal to 3 wt.% (Eguizábal et al. 2013). The addition of the IL-zeolite composition to the PBI membrane improved H+/H2 transport selectivity in comparison with the pristine PBI membrane due to the hydrogen bond-type interactions between ions of IL in the IL network (Eguizábal et al. 2013). The membranes are investigated in the H2/O2 single cell under anhydrous conditions up to 180°C showing that such a hybrid membrane is promising as the high-temperature PEM.
As was already mentioned, ILs can be used as plasticizers (Rahman and Brazel 2006, Yoon et al. 2011, Saroj and Singh 2012, Liew et al. 2014a, 2015), thus improving the ionic conductivity, thermal and mechanical properties, and also enhancing the flexible properties of the materials (Saroj and Singh 2012). Therefore, the SILM with ILs enables us to increase the operating temperature of a fuel cell without the membrane dehydration. Thanks to the high ionic conductivity of ILs, the redox cycle of the polymer can occur without the solvation of the membrane with water during the fuel cell operation. Moreover, the use of ILs in the PEM allows us to produce non-flammable and low-vapor-pressure electrolytes (Armand et al. 2009). Therefore, ILs are widely studied as the additives for supercapacitors and polymer electrolyte membranes used in fuel cells (Saroj and Singh 2012, Liew et al. 2014a, Thanganathan and Nogami 2015, Gorska et al. 2016) (Table 6).
The protic (Díaz et al. 2015, Thanganathan and Nogami 2015, Gorska et al. 2016) and Brönsted acidic ILs are un-reactive toward bases or acids (Armand et al. 2009, Yang et al. 2014) and are investigated as proton carriers in the PEM. Such ILs are often incorporated into PVA due to chemical resistance, mechanical stability, biodegradability, and the acceptable price (Yang et al. 2014, Kakati et al. 2015, Thanganathan and Nogami 2015). However, PVA is highly soluble in water; therefore, the crosslinking of polymers is required. The crosslinking agents, such as sulfosuccinic acid (SSA) or glutaraldehyde (GA), allow crosslinking of dense PVA-based membranes with the improved water resistance (Rhim et al. 2004, Higa et al. 2012, 2015, Kudoh et al. 2013). The crosslinking reaction occurs between the –OH group of PVA and the –COOH and –CHO groups in SSA and GA, respectively. It was shown that the dissolution rate of the crosslinked PVA membrane decreased up to 90% compared to the pristine PVA membrane. Moreover, the incorporation of SSA (possessing –SO3H groups) leads to an additional increase of the membrane proton conductivity (Rhim et al. 2004, Kudoh et al. 2013, Kakati et al. 2015).
It was shown that the incorporation of 1-butyl-3-methylimidazole methanesulfonate [BMIM][CH3SO3] and [EMIM][BF4], together with Y2O3, into the sulfonated polyetheretherketone (SPEEK) membrane improved the conductivity compared to the pristine SPEEK membrane (Chen et al. 2012). The conductivity of the doped SPEEK membrane increased with increasing temperature from 30°C to 90°C, whereas the conductivity of pure SPEEK decreased in the investigated temperature range. SPEEK/EB/Y2O3 and SPEEK/BS/Y2O3 possess the conductivity equal to 8.04×10−2 and 1.02×10−1 S cm−1 at 50% relative humidity (RH) and 9.04×10−2 and 1.18×10−1 S cm−1 at 100% RH, respectively. The SPEEK membranes doped with ILs had higher conductivities regardless of the tested temperature due to the proton transport by ILs. In the case of a pure SPEEK membrane, an increased temperature caused the evaporation of water responsible for the proton transport across the membrane resulting in the decrease of the ionic conductivity. The addition of IL and Y2O3 improved the mechanical properties of the formed membranes. The tensile strength at break of the pristine SPEEK membrane was equal to 1.94 MPa, whereas it was 2.61 and 2.33 MPa for SPEEK/EB/Y2O3 and SPEEK/BS/Y2O3 composite membranes, respectively (Chen et al. 2012).
Lee et al. (2010) investigated protic IL, based on diethylmethylammonium [DEMA] cation and different anions ([TfO] and [Tf2N]) in terms of their application as a proton conductor for a fuel cell. [DEMA][TfO] revealed high activity for the hydrogen oxidation reaction and oxygen reduction reaction at the Pt electrode in contrast to [DEMA][Tf2N], wherein the open circuit voltage for [DEMA][TfO] and [DEMA][Tf2N] was 1.03 and 0.7 V at 150°C, respectively. Despite the relatively low proton transport number (0.5–0.6) of [DEMA][TfO], the proton exchange reaction between ammonium cation and anions was fast due to continuous amine deprotonation during the fuel cell operation. The composite membrane of [DEMA][TfO] and six-membered sulfonated polyimides was successfully used in an anhydrous H2/O2 fuel cell at 30°C, 120°C, and 140°C with the current density equal to 250 mA cm−2 at 120°C (Lee et al. 2010).
In addition to the modification of the commonly used PEMs, such as Nafion or SPEEK, the novel alternative polymers are also investigated as potential separators for fuel cells (Schmidt et al. 2008, Liew et al. 2014a,bThanganathan and Nogami 2015). Liew et al. (2014b, 2015) studied PVA-based membranes containing ammonium acetate (CH3COONH4) and 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]). The increasing temperature and content of [BMIM][Cl] resulted in the increase of ionic conductivity. The PVA membrane containing 50 wt.% of IL possessed the highest value of ionic conductivity and operational current equal to 5.74 mS cm−1 and 750 mA, respectively. The enhancement of the ionic conductivity of the investigated membrane was also related to the increased amorphous degree (χc) of the polymer matrix up to 92% for the membrane containing 60 wt.% of tested IL. The addition of salt and IL to the PVA membrane resulted in the improvement of the membrane thermal stability due to the complexation between the components of the obtained polymer electrolyte, which was proved by the FTIR-ATR analysis. The application of the PVA/CH3COONH4/[BMIM][Cl] membrane as the PEM allowed us to achieve the power density of the electrochemical cell of 18 mW cm−1 at room temperature and the thermal stability of the membrane up to 250°C.
In general, the incorporation of inorganic fillers, such as tetraethyl orthosilicate (TEOS-Si(OC2H5)4) and phosphomolybdic acid (PMA)-H3(P(Mo3O10)4), and ILs, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide [BMIM][TFSI] and 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF4], into the PVA matrix enhances the thermal stability with the onset degradation temperature higher than 200°C (Thanganathan and Nogami 2015). The hybrid PVA/PMA/SiO2 membrane with [BMIM][TFSI] and [EMIM][BF4] revealed the highest proton conductivity equal to 0.83×10−3 and 0.58×10−3 S cm−1 at 60°C and 50% RH, respectively. It was pointed out that the ionic conductivity decreased with increasing IL content as the presence of the ILs decreased the hydrophilic character of the membrane due to the enhanced membrane crosslinking density. In addition, such crosslinking promotes the decrease of water uptake compared to pure PVA/PMA/SiO2 from 50.1% to 42.8% and from 50.3% to 45.9% for [EMIM][BF4] and [BMIM][TFSI], respectively (Thanganathan and Nogami 2015).
Põhako-Esko et al. (2013) studied the influence of the non-polymerizable IL ([EMIM][BF4]) on the ionic conductivity of different PILs 1-[n-(methacryloyloxy)alkyl]-3-methylimidazolium bromides (MAAMIM][Br]). It was shown that an increase of the [EMIM][BF4] content increased the ionic conductivity of the investigated materials. The composites containing 40% vol/vol of [EMIM][BF4] showed the conductivity of 10−4 S cm−1, whereas the pristine PIL possessed the conductivity of 10−5 S cm−1. Marcilla et al. (2006) prepared polymer electrolytes based on the analogues of PIL and non-PIL by mixing poly[1-vinyl-3-ethyl-imidazolium] (poly[ViEtIm]) containing different counter-ions ([Tf2N], [BF4], and [Br]) with the corresponding ILs – 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonimide) [BMIM][Tf2N], 1-butyl-3-methylimidazolium tetrafluoro-borate [BMIM][BF4], and 1-butyl-3-methylimidazolium bromide [BMIM][Br], respectively. The increase of the non-PIL content resulted in the increase of the conductivity of the obtained polymer electrolytes from 10−5 up to 10−2 S cm−1 and at room temperature. Moreover, it was noted out that due to the chemical affinity between IL and PIL achieved by choosing the same anion, more stable polymer electrolytes can be obtained (Marcilla et al. 2006).
Another approach to raise the PIL conductivity is an incorporation of the spacer between the anionic charge and the main polymer PIL chain (Yoshizawa et al. 2002, Díaz et al. 2014a), as the freedom of the proton conductive ion is a crucial parameter in ion transport. Yoshizawa et al. (2002) developed a poly(vinylimidazolium-co-3-sulfopropyl acrylate) copolymer with a flexible spacer between the main polymer chain and the anionic charge. The presence of the spacer resulted in the increase of the ionic conductivity up to 1.2×10−5 S cm−1 at 50°C compared to the conductivity of the polymer without the spacer (1×10−9 S cm−1 at 50°C). The influence of the spacer length and structure of the imidazolium cation was studied (Ohno et al. 2004). The investigated polycation with a flexible long spacer possesses the same ionic conductivity equal to 10−4 S cm−1 at room temperature as the IL polyanion without a spacer. In both cases, low glass transition temperature (approximately −60°C) after polymerization was maintained. The ionic conductivity of polyanions with and without a spacer was quite similar due to the fact that the decrease of the glass transition temperature improved the ionic conductivity of PILs.
It was observed that PILs possess reduced mechanical stability after polymerization, which can be eventually improved by the additional crosslinking (Washiro et al. 2004, Shaplov et al. 2011, Lemus et al. 2015). Washiro et al. (2004) studied the influence of the crosslinking on the mechanical properties and the ionic conductivity of the IL of polymer brush type. The investigated polymers possess different hydrocarbon chain lengths between polymerizable groups and the imidazolium rings. It was shown that crosslinking with tri(ethylene glycol) divinyl ether (E3V) improved the polymer mechanical strength. However, high amount of the added crosslinker increases the Tg value, which is associated with the restricted motion of the polymer backbone. Therefore, a decrease of ionic conductivity is observed after crosslinking with an excess of E3V. The addition of 0.5 mol % of tetra(ethylene glycol)diacrylate (E4A) resulted in the highest ionic conductivity of the obtained films of 1.1×10−4 S cm−1 at 30°C. Moreover, the prepared membranes were transparent and flexible. The E4A crosslinker was found to possess a suitable spacer length maintaining high ionic conductivity despite its smaller amount used. It was mentioned that the high segmental motion of the matrix requires the addition of the polymerizable groups and ethylene oxide as a spacer (Washiro et al. 2004).
According to the presented research works, it can be seen that the incorporation of RTILs in the membranes as a proton carrier leads to stable membrane materials characterized by conductivity and electrochemical resistance comparable to the classical PEM based on perfluorosulfonic acid. Moreover, the use of RTILs enables us to exploit the membrane under anhydrous conditions at an elevated temperature of >100°C; hence up to date, this research area is one of the most widely investigated areas. Another significant research direction is the use of PIL in order to reduce the RTIL loss during PEM exploitation. However, the replacement of RTIL into PIL is far from the practical application due to the drop of the proton conductivity. This resulted in attempts to elaborate RTIL and PIL blends with improved membrane efficiency and lifespan.
6 Conclusions
The application of ILs for the preparation and modification of membranes used in metal ion separation, gas separation, pervaporation, and PEMFC is a very promising approach. ILs have been studied extensively due to their outstanding properties; however, they still do possess some drawbacks which need to be addressed. Thanks to the almost infinite possibility of tailoring the selectivity of the membranes by changing the cations and/or anion as well as by the inclusion of the chosen functional groups, a vast number of composite RTIL membranes can be proposed. The application of ILs is the notable possibility for the replacement of the flammable and toxic VOCs used in metal ion separation. The incorporation of ILs into membranes can improve the separation and transport properties of the membranes in separation of gas and liquid mixtures. Moreover, very low volatile nature of ILs can prevent the loss of solvent by evaporation in comparison with conventional liquid membranes. The application of ILs also leads to creation of a novel class of membrane materials for PEMFCs which can operate under anhydrous conditions and at elevated temperatures (>100°C). However, it was revealed that RTIL used in membranes for gas and liquid mixture separation may leach out from the membrane pores during the process. Thus, the promising approach to limit the IL losses from the membrane is the use of PILs, despite the fact that such kind of ILs will simultaneously decrease the ion mobility, increase the glass transition temperature, and thus decrease the ionic conductivity. The research on ILs carried out up to now proved that the choice of the suitable IL in a given separation process requires compromise between the IL properties and the achievable efficiency of the material.
Acknowledgments
This work has received funding from the Polish National Science Centre (grant agreement no. DEC-2015/18/M/ST5/00635). Edyta Rynkowska has received the French Government Scholarship (grant no. 848642E, 878205J). This work is a part of the joint PhD of Edyta Rynkowska (Nicolaus Copernicus University, Torun, Poland, and Université de Rouen, France).
References
Acharya NK, Kulshrestha V, Awasthi K, Jain AK, Singh M, Vijay YK. Hydrogen separation in doped and blend polymer membranes. Int J Hydrogen Energy 2008; 33: 327–331.10.1016/j.ijhydene.2007.07.030Suche in Google Scholar
Adibi M, Barghi SH, Rashtchian D. Predictive models for permeability and diffusivity of CH4 through imidazolium-based supported ionic liquid membranes. J Membr Sci 2011; 371: 127–133.10.1016/j.memsci.2011.01.024Suche in Google Scholar
Agreda DD, Garcia-Diaz I, López FA, Alguacil FJ. Supported liquid membranes technologies in metals removal from liquid effluents. Rev Metal 2011; 47: 146–168.10.3989/revmetalmadrid.1062Suche in Google Scholar
Albo J, Santos E, Neves LA, Simeonov SP, Afonso CAM, Crespo JG, Irabien A. Separation performance of CO2 through supported magnetic ionic liquid membranes (SMILMs). Sep Purif Technol 2012; 97: 26–33.10.1016/j.seppur.2012.01.034Suche in Google Scholar
Almeida MIGS, Cattrall RW, Kolev SD. Recent trends in extraction and transport of metal ions using polymer inclusion membranes (PIMs). J Membr Sci 2012; 415–416: 9–23.10.1016/j.memsci.2012.06.006Suche in Google Scholar
Ansaloni L, Nykaza JR, Ye Y, Elabd YA, Giacinti Baschetti M. Influence of water vapor on the gas permeability of polymerized ionic liquids membranes. J Membr Sci 2015; 487: 199–208.10.1016/j.memsci.2015.03.065Suche in Google Scholar
Armand M, Endres F, MacFarlane DR, Ohno H, Scrosati B. Ionic-liquid materials for the electrochemical challenges of the future. Nat Mater 2009; 8: 621–629.10.1142/9789814317665_0020Suche in Google Scholar
Arous O, Saoud FS, Amara M, Kerdjoudj H. Efficient facilitated transport of lead and cadmium across a plasticized triacetate membrane mediated by D2EHPA and TOPO. Mater Sci Appl 2011; 2: 615–623.10.4236/msa.2011.26083Suche in Google Scholar
Bakonyi P, Nemestóthy N, Bélafi-Bakó K. Biohydrogen purification by membranes: an overview on the operational conditions affecting the performance of non-porous, polymeric and ionic liquid based gas separation membranes. Int J Hydrogen Energy 2013; 38: 9673–9687.10.1016/j.ijhydene.2013.05.158Suche in Google Scholar
Banu LA, Wang D, Baltus RE. Effect of ionic liquid confinement on gas separation characteristics. Energy Fuels 2013; 27: 4161–4166.10.1021/ef302038eSuche in Google Scholar
Bara JE, Lessmann S, Gabriel CJ, Hatakeyama ES, Noble RD, Gin DL. Synthesis and performance of polymerizable room-temperature ionic liquids as gas separation membranes. Ind Eng Chem Res 2007; 46: 5397–5404.10.1021/ie0704492Suche in Google Scholar
Bara JE, Gabriel CJ, Hatakeyama ES, Carlisle TK, Lessmann S, Noble RD, Gin DL. Improving CO2 selectivity in polymerized room-temperature ionic liquid gas separation membranes through incorporation of polar substituents. J Membr Sci 2008a; 321: 3–7.10.1016/j.memsci.2007.12.033Suche in Google Scholar
Bara JE, Gin DL, Noble RD. Effect of anion on gas separation performance of polymer–room-temperature ionic liquid composite membranes. Ind Eng Chem Res 2008b; 47: 9919–9924.10.1021/ie801019xSuche in Google Scholar
Bara JE, Hatakeyama ES, Gin DL, Noble RD. Improving CO2 permeability in polymerized room-temperature ionic liquid gas separation membranes through the formation of a solid composite with a room-temperature ionic liquid. Polym Adv Technol 2008c; 19: 1415–1420.10.1002/pat.1209Suche in Google Scholar
Bara JE, Noble RD, Gin DL. Effect of “free” cation substituent on gas separation performance of polymer–room-temperature ionic liquid composite membranes. Ind Eng Chem Res 2009; 48: 4607–4610.10.1021/ie801897rSuche in Google Scholar
Bernardo P, Jansen JC, Bazzarelli F, Tasselli F, Fuoco A, Friess K, Izák P, Jarmarová V, Kačírková M, Clarizia G. Gas transport properties of Pebax®/room temperature ionic liquid gel membranes. Sep Purif Technol 2012; 97: 73–82.10.1016/j.seppur.2012.02.041Suche in Google Scholar
Bhavsar RS, Kumbharkar SC, Kharul UK. Investigation of gas permeation properties of film forming polymeric ionic liquids (PILs) based on polybenzimidazoles. J Membr Sci 2014; 470: 494–503.10.1016/j.memsci.2014.07.076Suche in Google Scholar
Blanchard LA, Hancu D, Beckman EJ, Brennecke JF. Green processing using ionic liquids and CO2. Nature 1999; 399: 28–29.10.1038/19887Suche in Google Scholar
Bum Park H, Hoek EMV, Tarabara VV. Gas separation membranes. In: Encyclopedia of membrane science and technology. Hoboken, NJ: John Wiley & Sons, Inc., 2013.Suche in Google Scholar
Cascon HR, Choudhari SK. 1-Butanol pervaporation performance and intrinsic stability of phosphonium and ammonium ionic liquid-based supported liquid membranes. J Membr Sci 2013; 429: 214–224.10.1016/j.memsci.2012.11.028Suche in Google Scholar
Ceynowa J, Narębska A, Wódzki R. Membrane fuel cells. Part II: decomposition in the ion-exchange membranes applied in the fuel cell. Rocz Chem 1974; 48: 1537–1543.Suche in Google Scholar
Chen L, Chen J. Asymmetric membrane containing ionic liquid [A336][P507] for the preconcentration and separation of heavy rare earth lutetium. ACS Sustainable Chem Eng 2016; 4: 2644–2650.10.1021/acssuschemeng.6b00141Suche in Google Scholar
Chen J, Guo Q, Li D, Tong J, Li X. Properties improvement of SPEEK based proton exchange membranes by doping of ionic liquids and Y2O3. Prog Nat Sci 2012; 22: 26–30.10.1016/j.pnsc.2011.12.005Suche in Google Scholar
Cheng L-H, Rahaman MSA, Yao R, Zhang L, Xu X-H, Chen H-L, Lai J-Y, Tung K-L. Study on microporous supported ionic liquid membranes for carbon dioxide capture. Int J Greenhouse Gas Control 2014; 21: 82–90.10.1016/j.ijggc.2013.11.015Suche in Google Scholar
Costache LN, Szczepanski P, Olteanu C, Lica CG, Teodorescu S, Orbeci C. Bulk liquid membrane separation of different cations using D2EHPA and Cyanex 302 as carriers. Rev Chim 2014; 65: 26–32.Suche in Google Scholar
Cowan MG, Gin DL, Noble RD. Poly(ionic liquid)/ionic liquid ion-gels with high “free” ionic liquid content: platform membrane materials for CO2/light gas separations. Acc Chem Res 2016; 49: 724–732.10.1021/acs.accounts.5b00547Suche in Google Scholar PubMed
Dahi A, Fatyeyeva K, Langevin D, Chappey C, Rogalsky SP, Tarasyuk OP, Benamor A, Marais S. Supported ionic liquid membranes for water and volatile organic compounds separation: sorption and permeation properties. J Membr Sci 2014; 458: 164–178.10.1016/j.memsci.2014.01.031Suche in Google Scholar
Dai Z, Noble RD, Gin DL, Zhang X, Deng L. Combination of ionic liquids with membrane technology: a new approach for CO2 separation. J Membr Sci 2016; 497: 1–20.10.1016/j.memsci.2015.08.060Suche in Google Scholar
Daniel CI, Rubio AM, Sebastião PJ, Afonso CAM, Storch J, Izák P, Portugal CAM, Crespo JG. Magnetic modulation of the transport of organophilic solutes through Supported Magnetic Ionic Liquid Membranes. J Membr Sci 2016; 505: 36–43.10.1016/j.memsci.2015.11.025Suche in Google Scholar
de Gyves J, de San Miguel ER. Metal ion separations by supported liquid membranes. Ind Eng Chem Res 1999; 38: 2182–2202.10.1021/ie980374pSuche in Google Scholar
Deng L, Hägg M-B. Techno-economic evaluation of biogas upgrading process using CO2 facilitated transport membrane. Int J Greenhouse Gas Control 2010; 4: 638–646.10.1016/j.ijggc.2009.12.013Suche in Google Scholar
Dharaskar SA, Wasewar KL, Varma MN, Shende DZ, Yoo CK. Deep removal of sulfur from model liquid fuels using 1-butyl-3-methylimidazolium chloride. Procedia Eng 2013a; 51: 416–422.10.1016/j.proeng.2013.01.058Suche in Google Scholar
Dharaskar SA, Wasewar KL, Varma MN, Shende DZ, Yoo CK. Ionic liquids: the novel solvent for removal of dibenzothiophene from liquid fuel. Procedia Eng 2013b; 51: 314–317.10.1016/j.proeng.2013.01.042Suche in Google Scholar
Díaz M, Ortiz A, Ortiz I. Progress in the use of ionic liquids as electrolyte membranes in fuel cells. J Membr Sci 2014a; 469: 379–396.10.1016/j.memsci.2014.06.033Suche in Google Scholar
Díaz M, Ortiz A, Vilas M, Tojo E, Ortiz I. Performance of PEMFC with new polyvinyl-ionic liquids based membranes as electrolytes. Int J Hydrogen Energy 2014b; 39: 3970–3977.10.1016/j.ijhydene.2013.04.155Suche in Google Scholar
Díaz M, Ortiz A, Isik M, Mecerreyes D, Ortiz I. Highly conductive electrolytes based on poly(HSO3-BVIm TfO)/HSO3-BMIm TfO mixtures for fuel cell applications. Int J Hydrogen Energy 2015; 40: 11294–11302.10.1016/j.ijhydene.2015.03.109Suche in Google Scholar
Dong Y, Guo H, Su Z, Wei W, Wu X. Pervaporation separation of benzene/cyclohexane through AAOM-ionic liquids/polyurethane membranes. Chem Eng Process 2015; 89: 62–69.10.1016/j.cep.2015.01.006Suche in Google Scholar
Eastman SA, Lesser AJ, McCarthy TJ. Quantitative poly(vinyl alcohol) modification in ionic liquids: esterification and urethanation with low surface tension producing reagents. Macromolecules 2010; 43: 4584–4588.10.1021/ma100458vSuche in Google Scholar
Eguizábal A, Lemus J, Pina MP. On the incorporation of protic ionic liquids imbibed in large pore zeolites to polybenzimidazole membranes for high temperature proton exchange membrane fuel cells. J Power Sources 2013; 222: 483–492.10.1016/j.jpowsour.2012.07.094Suche in Google Scholar
Erdni-Goryaev EM, Alent’ev AY, Belov NA, Ponkratov DO, Shaplov AS, Lozinskaya EI, Vygodskii YS. Gas separation characteristics of new membrane materials based on poly(ethylene glycol)-crosslinked polymers and ionic liquids. Pet Chem 2012; 52: 494–498.10.1134/S0965544112070031Suche in Google Scholar
Erdni-Goryaev EM, Alent’ev AY, Shaplov AS, Ponkratov DO, Lozinskaya EI. New membrane materials based on crosslinked poly(ethylene glycols) and ionic liquids for separation of gas mixtures containing CO2. Polym Sci Ser B 2014; 56: 900–908.10.1134/S1560090414060062Suche in Google Scholar
Fadeev AG, Meagher MM. Opportunities for ionic liquids in recovery of biofuels. Chem Commun 2001; 3: 295–296.10.1039/b006102fSuche in Google Scholar
Fontàs C, Tayeb R, Dhahbi M, Gaudichet E, Thominette F, Roy P, Steenkeste K, Fontaine-Aupart M-P, Tingry S, Tronel-Peyroz E, Seta P. Polymer inclusion membranes: the concept of fixed sites membrane revised. J Membr Sci 2007; 290: 62–72.10.1016/j.memsci.2006.12.019Suche in Google Scholar
Fortunato R, Gonzalez-Munoz MJ, Kubasiewicz M, Luque S, Alvarez JR, Afonso CAM, Coelhoso IM, Crespo JG. Liquid membranes using ionic liquids: the influence of water on solute transport. J Membr Sci 2005; 249: 153–162.10.1016/j.memsci.2004.10.007Suche in Google Scholar
Friess K, Jansen JC, Bazzarelli F, Izák P, Jarmarová V, Kačírková M, Schauer J, Clarizia G, Bernardo P. High ionic liquid content polymeric gel membranes: correlation of membrane structure with gas and vapour transport properties. J Membr Sci 2012; 415–416: 801–809.10.1016/j.memsci.2012.05.072Suche in Google Scholar
Friess K, Lanč M, Pilnáček K, Fíla V, Vopička O, Sedláková Z, Cowan MG, McDanel WM, Noble RD, Gin DL, Izak P. CO2/CH4 separation performance of ionic-liquid-based epoxy-amine ion gel membranes under mixed feed conditions relevant to biogas processing. J Membr Sci 2017; 528: 64–71.10.1016/j.memsci.2017.01.016Suche in Google Scholar
Gherasim CV, Cristea M, Grigoras CV, Bourceanu G. New polymer inclusion membrane. Preparation and characterization. Dig J Nanomater Biostruct 2011; 6: 1499–1508.Suche in Google Scholar
Gorska B, Timperman L, Anouti M, Pernak J, Beguin F. Physicochemical and electrochemical properties of a new series of protic ionic liquids with N-chloroalkyl functionalized cations. RSC Adv 2016; 6: 55144–55158.10.1039/C6RA12152GSuche in Google Scholar
Grünauer J, Shishatskiy S, Abetz C, Abetz V, Filiz V. Ionic liquids supported by isoporous membranes for CO2/N2 gas separation applications. J Membr Sci 2015; 494: 224–233.10.1016/j.memsci.2015.07.054Suche in Google Scholar
Grünauer J, Filiz V, Shishatskiy S, Abetz C, Abetz V. Scalable application of thin film coating techniques for supported liquid membranes for gas separation made from ionic liquids. J Membr Sci 2016; 518: 178–191.10.1016/j.memsci.2016.07.005Suche in Google Scholar
Gu YY, Lodge TP. Synthesis and gas separation performance of triblock copolymer ion gels with a polymerized ionic liquid mid-block. Macromolecules 2011; 44: 1732–1736.10.1021/ma2001838Suche in Google Scholar
Guisao JPT, Romero AJF. Interaction between Zn2+ cations and n-methyl-2-pyrrolidone in ionic liquid-based gel polymer electrolytes for Zn batteries. Electrochim Acta 2015; 176: 1447–1453.10.1016/j.electacta.2015.07.132Suche in Google Scholar
Hassan Hassan Abdellatif F, Babin J, Arnal-Herault C, David L, Jonquieres A. Grafting of cellulose acetate with ionic liquids for biofuel purification by a membrane process: influence of the cation. Carbohydr Polym 2016; 147: 313–322.10.1016/j.carbpol.2016.04.008Suche in Google Scholar PubMed
Heitmann S, Krings J, Kreis P, Lennert A, Pitner WR, Górak A, Schulte MM. Recovery of n-butanol using ionic liquid-based pervaporation membranes. Sep Purif Technol 2012; 97: 108–114.10.1016/j.seppur.2011.12.033Suche in Google Scholar
Hernández-Fernández FJ, de los Ríos AP, Mateo-Ramírez F, Godínez C, Lozano-Blanco LJ, Moreno JI, Tomás-Alonso F. New application of supported ionic liquids membranes as proton exchange membranes in microbial fuel cell for waste water treatment. Chem Eng J 2015; 279: 115–119.10.1016/j.cej.2015.04.036Suche in Google Scholar
Hernández-Fernández FJ, de los Ríos AP, Mateo-Ramírez F, Juarez MD, Lozano-Blanco LJ, Godínez C. New application of polymer inclusion membrane based on ionic liquids as proton exchange membrane in microbial fuel cell. Sep Purif Technol 2016; 160: 51–58.10.1016/j.seppur.2015.12.047Suche in Google Scholar
Higa M, Nishimura M, Kinoshita K, Jikihara A. Characterization of cation-exchange membranes prepared from poly(vinyl alcohol) and poly(vinyl alcohol-b-styrene sulfonic acid). Int J Hydrogen Energy 2012; 37: 6161–6168.10.1016/j.ijhydene.2011.06.003Suche in Google Scholar
Higa M, Feng S, Endo N, Kakihana Y. Characteristics and direct methanol fuel cell performance of polymer electrolyte membranes prepared from poly(vinyl alcohol-b-styrene sulfonic acid). Electrochim Acta 2015; 153: 83–89.10.1016/j.electacta.2014.11.155Suche in Google Scholar
Hoek EMV, Tarabara V, editors. Encyclopedia of membrane science and technology. Hoboken, NJ: John Wiley & Sons, Inc., 1999.Suche in Google Scholar
Hopkinson D, Zeh M, Luebke D. The bubble point of supported ionic liquid membranes using flat sheet supports. J Membr Sci 2014; 468: 155–162.10.1016/j.memsci.2014.05.042Suche in Google Scholar
Horne WJ, Andrews MA, Shannon MS, Terrill KL, Moon JD, Hayward SS, Bara JE. Effect of branched and cycloalkyl functionalities on CO2 separation performance of poly(IL) membranes. Sep Purif Technol 2015; 155: 89–95.10.1016/j.seppur.2015.02.009Suche in Google Scholar
Hudiono YC, Carlisle TK, LaFrate AL, Gin DL, Noble RD. Novel mixed matrix membranes based on polymerizable room-temperature ionic liquids and SAPO-34 particles to improve CO2 separation. J Membr Sci 2011; 370: 141–148.10.1016/j.memsci.2011.01.012Suche in Google Scholar
Imaizumi S, Kokubo H, Watanabe M. Polymer actuators using ion-gel electrolytes prepared by self-assembly of aba-triblock copolymers. Macromolecules 2012; 45: 401–409.10.1021/ma2022138Suche in Google Scholar
Izák P, Mateus NMM, Afonso CAM, Crespo JG. Enhanced esterification conversion in a room temperature ionic liquid by integrated water removal with pervaporation. Sep Purif Technol 2005; 41: 141–145.10.1016/j.seppur.2004.05.004Suche in Google Scholar
Izák P, Kockerling M, Kragl U. Stability and selectivity of a multiphase membrane, consisting of dimethylpolysiloxane on an ionic liquid, used in the separation of solutes from aqueous mixtures by pervaporation. Green Chem 2006a; 8: 947–948.10.1039/B608114BSuche in Google Scholar
Izák P, Kragl U, Köckerling M. Multiphase membrane, Rostock Uo, Germany, 2006b.Suche in Google Scholar
Izák P, Ruth W, Fei Z, Dyson PJ, Kragl U. Selective removal of acetone and butan-1-ol from water with supported ionic liquid–polydimethylsiloxane membrane by pervaporation. Chem Eng J 2008a; 139: 318–321.10.1016/j.cej.2007.08.001Suche in Google Scholar
Izák P, Schwarz K, Ruth W, Bahl H, Kragl U. Increased productivity of Clostridium acetobutylicum fermentation of acetone, butanol, and ethanol by pervaporation through supported ionic liquid membrane. Appl Microbiol Biotechnol 2008b; 78: 597–602.10.1007/s00253-008-1354-0Suche in Google Scholar
Izák P, Friess K, Hynek V, Ruth W, Fei Z, Dyson JP, Kragl U. Separation properties of supported ionic liquid–polydimethylsiloxane membrane in pervaporation process. Desalination 2009; 241: 182–187.10.1016/j.desal.2007.12.050Suche in Google Scholar
Jansen JC, Friess K, Clarizia G, Schauer J, Izák P. High ionic liquid content polymeric gel membranes: preparation and performance. Macromolecules 2011; 44: 39–45.10.1021/ma102438kSuche in Google Scholar
Jansen JC, Clarizia G, Bernardo P, Bazzarelli F, Friess K, Randová A, Schauer J, Kubicka D, Kacirková M, Izak P. Gas transport properties and pervaporation performance of fluoropolymer gel membranes based on pure and mixed ionic liquids. Sep Purif Technol 2013; 109: 87–97.10.1016/j.seppur.2013.02.034Suche in Google Scholar
Jarosik A, Krajewski SR, Lewandowski A, Radzimski P. Conductivity of ionic liquids in mixtures. J Mol Liq 2006; 123: 43–50.10.1016/j.molliq.2005.06.001Suche in Google Scholar
Jönsson JÅ, Mathiasson L. Liquid membrane extraction in analytical sample preparation: I. Principles. Trends Anal Chem 1999; 18: 318–325.10.1016/S0165-9936(99)00102-8Suche in Google Scholar
Jue ML, Lively RP. Targeted gas separations through polymer membrane functionalization. React Funct Polym 2015; 86: 88–110.10.1016/j.reactfunctpolym.2014.09.002Suche in Google Scholar
Kadokawa J-I. Preparation of polysaccharide-based materials compatibilized with ionic liquids. In Kokorin A, editor. Ionic liquids: applications and perspectives. Rijeka: InTech, 2011; 95–114.Suche in Google Scholar
Kakati N, Maiti J, Das G, Lee SH, Yoon YS. An approach of balancing the ionic conductivity and mechanical properties of PVA based nanocomposite membrane for DMFC by various crosslinking agents with ionic liquid. Int J Hydrogen Energy 2015; 40: 7114–7123.10.1016/j.ijhydene.2015.04.004Suche in Google Scholar
Kanakubo M, Makino T, Umecky T, Sakurai M. Effect of partial pressure on CO2 solubility in ionic liquid mixtures of 1-butyl-3-methylimidazolium acetate and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide. Fluid Phase Equilib 2016; 420: 74–82.10.1016/j.fluid.2016.01.034Suche in Google Scholar
Kárászová M, Kacirková M, Friess K, Izák P. Progress in separation of gases by permeation and liquids by pervaporation using ionic liquids: a review. Sep Purif Technol 2014; 132: 93–101.10.1016/j.seppur.2014.05.008Suche in Google Scholar
Karkhanechi H, Salmani S, Asghari M. A review on gas separation applications of supported ionic liquid membranes. ChemBioEng Rev 2015; 2: 290–302.10.1002/cben.201500001Suche in Google Scholar
Kasahara S, Kamio E, Ishigami T, Matsuyama H. Effect of water in ionic liquids on CO2 permeability in amino acid ionic liquid-based facilitated transport membranes. J Membr Sci 2012; 415–416: 168–175.10.1016/j.memsci.2012.04.049Suche in Google Scholar
Kasahara S, Kamio E, Shaikh AR, Matsuki T, Matsuyama H. Effect of the amino-group densities of functionalized ionic liquids on the facilitated transport properties for CO2 separation. J Membr Sci 2016; 503: 148–157.10.1016/j.memsci.2016.01.007Suche in Google Scholar
Kebiche-Senhadji O, Bey S, Clarizia G, Mansouri L, Benamor M. Gas permeation behavior of CTA polymer inclusion membrane (PIM) containing an acidic carrier for metal recovery (DEHPA). Sep Purif Technol 2011; 80: 38–44.10.1016/j.seppur.2011.03.032Suche in Google Scholar
Kogelnig D, Stojanovic A, Jirsa F, Körner W, Krachler R, Keppler BK. Transport and separation of iron(III) from nickel(II) with the ionic liquid trihexyl(tetradecyl)phosphonium chloride. Sep Purif Technol 2010; 72: 56–60.10.1016/j.seppur.2009.12.028Suche in Google Scholar
Kohoutová M, Sikora A, Hovorka Š, Randová A, Schauer J, Tišma M, Setničková K, Petričkovič R, Guernik S, Greenspoon N, Izák P. Influence of ionic liquid content on properties of dense polymer membranes. Eur Polym J 2009; 45: 813–819.10.1016/j.eurpolymj.2008.11.043Suche in Google Scholar
Krull FF, Fritzmann C, Melin T. Liquid membranes for gas/vapor separations. J Membr Sci 2008; 325: 509–519.10.1016/j.memsci.2008.09.018Suche in Google Scholar
Kudoh Y, Kojima T, Abe M, Oota M, Yamamoto T. Proton conducting membranes consisting of poly(vinyl alcohol) and poly(styrene sulfonic acid): crosslinking of poly(vinyl alcohol) with and without succinic acid. Solid State Ionics 2013; 253: 189–194.10.1016/j.ssi.2013.09.047Suche in Google Scholar
Kujawski W. Membrane selectivity in pervaporation. Sep Sci Technol 1996; 31: 1555–1571.10.1080/01496399608001413Suche in Google Scholar
Kujawski W. Application of pervaporation and vapor permeation in environmental protection. Pol J Environ Stud 2000; 1: 13–26.Suche in Google Scholar
Lam B, Wei M, Zhu L, Luo S, Guo R, Morisato A, Alexandridis P, Lin H. Cellulose triacetate doped with ionic liquids for membrane gas separation. Polymer 2016; 89: 1–11.10.1016/j.polymer.2016.02.033Suche in Google Scholar
Lee J-M. Extraction of noble metal ions from aqueous solution by ionic liquids. Fluid Phase Equilib 2012; 319: 30–36.10.1016/j.fluid.2012.01.033Suche in Google Scholar
Lee SY, Ogawa A, Kanno M, Nakamoto H, Yasuda T, Watanabe M. Nonhumidified intermediate temperature fuel cells using protic ionic liquids. J Am Chem Soc 2010; 132: 9764–9773.10.1021/ja102367xSuche in Google Scholar PubMed
Lemus J, Eguizábal A, Pina MP. UV polymerization of room temperature ionic liquids for high temperature PEMs: study of ionic moieties and crosslinking effects. Int J Hydrogen Energy 2015; 40: 5416–5424.10.1016/j.ijhydene.2015.01.078Suche in Google Scholar
Li Q, He R, Jensen JO, Bjerrum NJ. Approaches and recent development of polymer electrolyte membranes for fuel cells operating above 100°C. Chem Mater 2003; 15: 4896–4915.10.1021/cm0310519Suche in Google Scholar
Li M, Yang B, Wang L, Zhang Y, Zhang Z, Fang S, Zhang Z. New polymerized ionic liquid (PIL) gel electrolyte membranes based on tetraalkylammonium cations for lithium ion batteries. J Membr Sci 2013; 447: 222–227.10.1016/j.memsci.2013.07.007Suche in Google Scholar
Li J, Dai Z, Usman M, Qi Z, Deng L. CO2/H2 separation by amino-acid ionic liquids with polyethylene glycol as co-solvent. Int J Greenhouse Gas Control 2016; 45: 207–215.10.1016/j.ijggc.2015.12.027Suche in Google Scholar
Liang L, Gan Q, Nancarrow P. Composite ionic liquid and polymer membranes for gas separation at elevated temperatures. J Membr Sci 2014; 450: 407–417.10.1016/j.memsci.2013.09.033Suche in Google Scholar
Liew C-W, Ramesh S, Arof AK. Good prospect of ionic liquid based-poly(vinyl alcohol) polymer electrolytes for supercapacitors with excellent electrical, electrochemical and thermal properties. Int J Hydrogen Energy 2014a; 39: 2953–2963.10.1016/j.ijhydene.2013.06.061Suche in Google Scholar
Liew C-W, Ramesh S, Arof AK. A novel approach on ionic liquid-based poly(vinyl alcohol) proton conductive polymer electrolytes for fuel cell applications. Int J Hydrogen Energy 2014b; 39: 2917–2928.10.1016/j.ijhydene.2013.07.092Suche in Google Scholar
Liew C-W, Arifin KH, Kawamura J, Iwai Y, Ramesh S, Arof AK. Electrical and structural studies of ionic liquid-based poly(vinyl alcohol) proton conductors. J Non-Cryst Solids 2015; 425: 163–172.10.1016/j.jnoncrysol.2015.06.008Suche in Google Scholar
Lin B, Qiu B, Qiu L, Si Z, Chu F, Chen X, Yan F. Imidazolium-functionalized SiO2 nanoparticle doped proton conducting membranes for anhydrous proton exchange membrane applications. Fuel Cells 2013; 13: 72–78.10.1002/fuce.201200096Suche in Google Scholar
Liu S, Zhou L, Wang PJ, Zhang FF, Yu SC, Shao ZG, Yi BL. Ionic-liquid-based proton conducting membranes for anhydrous H2/Cl2 fuel-cell applications. ACS Appl Mater Interfaces 2014; 6: 3195–3200.10.1021/am404645cSuche in Google Scholar PubMed
Lodge TP. A unique platform for materials design. Science 2008; 321: 50–51.10.1126/science.1159652Suche in Google Scholar PubMed
Lozano LJ, Godínez C, de los Ríos AP, Hernández-Fernández FJ, Sánchez-Segado S, Alguacil FJ. Recent advances in supported ionic liquid membrane technology. J Membr Sci 2011; 376: 1–14.10.1016/j.memsci.2011.03.036Suche in Google Scholar
Lu J, Yan F, Texter J. Advanced applications of ionic liquids in polymer science. Prog Polym Sci 2009; 34: 431–448.10.1016/j.progpolymsci.2008.12.001Suche in Google Scholar
Lu J-G, Lu C-T, Chen Y, Gao L, Zhao X, Zhang H, Xu Z-W. CO2 capture by membrane absorption coupling process: application of ionic liquids. Appl Energy 2014; 115: 573–581.10.1016/j.apenergy.2013.10.045Suche in Google Scholar
Łuczak J, Paszkiewicz M, Krukowska A, Malankowska A, Zaleska-Medynska A. Ionic liquids for nano- and microstructures preparation. Part 1: properties and multifunctional role. Adv Colloid Interface Sci 2016a; 230: 13–28.10.1016/j.cis.2015.08.006Suche in Google Scholar PubMed
Łuczak J, Paszkiewicz M, Krukowska A, Malankowska A, Zaleska-Medynska A. Ionic liquids for nano- and microstructures preparation. Part 2: application in synthesis. Adv Colloid Interface Sci 2016b; 227: 1–52.10.1016/j.cis.2015.08.010Suche in Google Scholar PubMed
Luis P, Neves LA, Afonso CAM, Coelhoso IM, Crespo JG, Garea A, Irabien A. Facilitated transport of CO2 and SO2 through Supported Ionic Liquid Membranes (SILMs). Desalination 2009; 245: 485–493.10.1016/j.desal.2009.02.012Suche in Google Scholar
Lynam JG, Chow GI, Coronella CJ, Hiibel SR. Ionic liquid and water separation by membrane distillation. Chem Eng J 2016; 288: 557–561.10.1016/j.cej.2015.12.028Suche in Google Scholar
Mahurin SM, Lee JS, Baker GA, Luo H, Dai S. Performance of nitrile-containing anions in task-specific ionic liquids for improved CO2/N2 separation. J Membr Sci 2010; 353: 177–183.10.1016/j.memsci.2010.02.045Suche in Google Scholar
Mahurin SM, Dai T, Yeary JS, Luo H, Dai S. Benzyl-functionalized room temperature ionic liquids for CO2/N2 separation. Ind Eng Chem Res 2011; 50: 14061–14069.10.1021/ie201428kSuche in Google Scholar
Malik MA, Hashim MA, Nabi F. Ionic liquids in supported liquid membrane technology. Chem Eng J 2011; 171: 242–254.10.1016/j.cej.2011.03.041Suche in Google Scholar
Marcilla R, Alcaide F, Sardon H, Pomposo JA, Pozo-Gonzalo C, Mecerreyes D. Tailor-made polymer electrolytes based upon ionic liquids and their application in all-plastic electrochromic devices. Electrochem Commun 2006; 8: 482–488.10.1016/j.elecom.2006.01.013Suche in Google Scholar
Martínez de Yuso MV, Neves LA, Coelhoso IM, Crespo JG, Benavente J, Rodríguez-Castellón E. A study of chemical modifications of a nafion membrane by incorporation of different room temperature ionic liquids. Fuel Cells 2012; 12: 606–613.10.1002/fuce.201100168Suche in Google Scholar
Martinez-Palou R, Luque R. Applications of ionic liquids in the removal of contaminants from refinery feedstocks: an industrial perspective. Energy Environ Sci 2014; 7: 2414–2447.10.1039/C3EE43837FSuche in Google Scholar
Martínez-Palou R, Likhanova NV, Olivares-Xometl O. Supported ionic liquid membranes for separations of gases and liquids: an overview. Pet Chem 2014; 54: 595–607.10.1134/S0965544114080106Suche in Google Scholar
Matsumoto M, Murakami Y, Kondo K. Separation of 1-butanol by pervaporation using polymer inclusion membranes containing ionic liquids. Solvent Extr Res Dev Jpn 2011; 18: 75–83.10.15261/serdj.18.75Suche in Google Scholar
Mohapatra PK, Lakshmi DS, Bhattacharyya A, Manchanda VK. Evaluation of polymer inclusion membranes containing crown ethers for selective cesium separation from nuclear waste solution. J Hazard Mater 2009; 169: 472–479.10.1016/j.jhazmat.2009.03.124Suche in Google Scholar PubMed
Murakami M-a, Kaneko Y, Kadokawa J-i. Preparation of cellulose-polymerized ionic liquid composite by in-situ polymerization of polymerizable ionic liquid in cellulose-dissolving solution. Carbohydr Polym 2007; 69: 378–381.10.1016/j.carbpol.2006.12.002Suche in Google Scholar
Neves LA, Dabek W, Coelhoso IM, Crespo JG. Design of new selective Nafion membranes using room temperature ionic liquids. Desalination 2006; 199: 525–526.10.1016/j.desal.2006.03.119Suche in Google Scholar
Neves LA, Benavente J, Coelhoso IM, Crespo JG. Design and characterisation of Nafion membranes with incorporated ionic liquids cations. J Membr Sci 2010a; 347: 42–52.10.1016/j.memsci.2009.10.004Suche in Google Scholar
Neves LA, Coelhoso IM, Crespo JG. Methanol and gas crossover through modified Nafion membranes by incorporation of ionic liquid cations. J Membr Sci 2010b; 360: 363–370.10.1016/j.memsci.2010.05.033Suche in Google Scholar
Neves LA, Crespo JG, Coelhoso IM. Gas permeation studies in supported ionic liquid membranes. J Membr Sci 2010c; 357: 160–170.10.1016/j.memsci.2010.04.016Suche in Google Scholar
Neves LA, Afonso C, Coelhoso IM, Crespo JG. Integrated CO2 capture and enzymatic bioconversion in supported ionic liquid membranes. Sep Purif Technol 2012; 97: 34–41.10.1016/j.seppur.2012.01.049Suche in Google Scholar
Nghiem LD, Mornane P, Potter ID, Perera JM, Cattrall RW, Kolev SD. Extraction and transport of metal ions and small organic compounds using polymer inclusion membranes (PIMs). J Membr Sci 2006; 281: 7–41.10.1016/j.memsci.2006.03.035Suche in Google Scholar
Nguyen PT, Voss BA, Wiesenauer EF, Gin DL, Noble RD. Physically gelled room-temperature ionic liquid-based composite membranes for CO2/N2 separation: effect of composition and thickness on membrane properties and performance. Ind Eng Chem Res 2013; 52: 8812–8821.10.1021/ie302352rSuche in Google Scholar
Noble RD, Gin DL. Perspective on ionic liquids and ionic liquid membranes. J Membr Sci 2011; 369: 1–4.10.1016/j.memsci.2010.11.075Suche in Google Scholar
Nowak Ł, Regel-Rosocka M, Marszałkowska B, Wiśniewski M. Removal of Zn(II) from chloride acidic solutions with hydrophobic quaternary salts. Pol J Chem Technol 2010; 12: 24–28.10.2478/v10026-010-0028-8Suche in Google Scholar
Ocampo AL, Aguilar JC, Rodríguez de San Miguel E, Monroy M, Roquero P, de Gyves J. Novel proton-conducting polymer inclusion membranes. J Membr Sci 2009; 326: 382–387.10.1016/j.memsci.2008.10.010Suche in Google Scholar
Ohno H, Yoshizawa M, Ogihara W. Development of new class of ion conductive polymers based on ionic liquids. Electrochim Acta 2004; 50: 255–261.10.1016/j.electacta.2004.01.091Suche in Google Scholar
Ong YT, Tan SH. Synthesis of the novel symmetric buckypaper supported ionic liquid membrane for the dehydration of ethylene glycol by pervaporation. Sep Purif Technol 2015; 143: 135–145.10.1016/j.seppur.2015.01.021Suche in Google Scholar
Ong YT, Tan SH. Pervaporation separation of a ternary azeotrope containing ethyl acetate, ethanol and water using a buckypaper supported ionic liquid membrane. Chem Eng Res Des 2016; 109: 116–126.10.1016/j.cherd.2015.10.051Suche in Google Scholar
Ong YT, Yee KF, Cheng YK, Tan SH. A review on the use and stability of supported liquid membranes in the pervaporation process. Sep Purif Rev 2014; 43: 62–88.10.1080/15422119.2012.716134Suche in Google Scholar
Padilha JC, Basso J, da Trindade LG, Martini EMA, de Souza MO, de Souza RF. Ionic liquids in proton exchange membrane fuel cells: efficient systems for energy generation. J Power Sources 2010; 195: 6483–6485.10.1016/j.jpowsour.2010.04.035Suche in Google Scholar
Parmentier D, Paradis S, Metz SJ, Wiedmer SK, Kroon MC. Continuous process for selective metal extraction with an ionic liquid. Chem Eng Res Des 2016; 109: 553–560.10.1016/j.cherd.2016.02.034Suche in Google Scholar
Perdikaki AV, Vangeli OC, Karanikolos GN, Stefanopoulos KL, Beltsios KG, Alexandridis P, Kanellopoulos NK, Romanos GE. Ionic liquid-modified porous materials for gas separation and heterogeneous catalysis. J Phys Chem C 2012; 116: 16398–16411.10.1021/jp300458sSuche in Google Scholar
Pereiro AB, Araújo JMM, Esperança JMSS, Marrucho IM, Rebelo LPN. Ionic liquids in separations of azeotropic systems – a review. J Chem Thermodyn 2012; 46: 2–28.10.1016/j.jct.2011.05.026Suche in Google Scholar
Pereiro AB, Tomé LC, Martinho S, Rebelo LPN, Marrucho IM. Gas permeation properties of fluorinated ionic liquids. Ind Eng Chem Res 2013; 52: 4994–5001.10.1021/ie4002469Suche in Google Scholar
Petra C, Katalin B-B. Application of ionic liquids in membrane separation processes. In Kokorin A, editior. Ionic liquids: applications and perspectives. Rijeka: InTech, 2011: 561–586.10.5772/14862Suche in Google Scholar
Pinnau I, Freeman BD. Formation and modification of polymeric membranes: overview. In Membrane formation and modification. Washington, DC: American Chemical Society, 1999: 1–22.10.1021/bk-2000-0744Suche in Google Scholar
Põhako-Esko K, Timusk M, Saal K, Lõhmus R, Kink I, Mäeorg U. Increased conductivity of polymerized ionic liquids through the use of a nonpolymerizable ionic liquid additive. J Mater Res 2013; 28: 3086–3093.10.1557/jmr.2013.330Suche in Google Scholar
Pospiech B. Synergistic solvent extraction and transport of Zn(II) and Cu(II) across polymer inclusion membranes with a mixture of TOPO and aliquat 336. Sep Sci Technol 2014; 49: 1706–1712.10.1080/01496395.2014.906456Suche in Google Scholar
Pospiech B. Application of phosphonium ionic liquids as ion carriers in polymer inclusion membranes (PIMs) for separation of cadmium(II) and copper(II) from aqueous solutions. J Solution Chem 2015a; 44: 2431–2447.10.1007/s10953-015-0413-2Suche in Google Scholar PubMed PubMed Central
Pospiech B. Highly efficient facilitated membrane transport of palladium(II) ions from hydrochloric acid solutions through plasticizer membranes with cyanex 471X. Physicochem Probl Miner Process 2015b; 51: 281–291.Suche in Google Scholar
Pospiech B. Studies on extraction and permeation of cadmium(II) using Cyphos IL 104 as selective extractant and ion carrier. Hydrometallurgy 2015c; 154: 88–94.10.1016/j.hydromet.2015.04.007Suche in Google Scholar
Pospiech B, Chagnes A. Highly selective solvent extraction of Zn(II) and Cu(II) from acidic aqueous chloride solutions with mixture of cyanex 272 and aliquat 336. Sep Sci Technol 2015; 50: 1302–1309.10.1080/01496395.2014.967777Suche in Google Scholar
Pospiech B, Kujawski W. Ionic liquids as selective extractants and ion carriers of heavy metal ions from aqueous solutions utilized in extraction and membrane separation. Rev Chem Eng 2015; 31: 179–191.10.1515/revce-2014-0048Suche in Google Scholar
Rahman M, Brazel CS. Ionic liquids: new generation stable plasticizers for poly(vinyl chloride). Polym Degrad Stab 2006; 91: 3371–3382.10.1016/j.polymdegradstab.2006.05.012Suche in Google Scholar
Regel-Rosocka M. Extractive removal of zinc(II) from chloride liquors with phosphonium ionic liquids/toluene mixtures as novel extractants. Sep Purif Technol 2009; 66: 19–24.10.1016/j.seppur.2008.12.002Suche in Google Scholar
Regel-Rosocka M, Nowak Ł, Wiśniewski M. Removal of zinc(II) and iron ions from chloride solutions with phosphonium ionic liquids. Sep Purif Technol 2012; 97: 158–163.10.1016/j.seppur.2012.01.035Suche in Google Scholar
Rewar AS, Shaligram SV, Kharul UK. Polybenzimidazole based polymeric ionic liquids possessing partial ionic character: effects of anion exchange on their gas permeation properties. J Membr Sci 2016; 497: 282–288.10.1016/j.memsci.2015.09.019Suche in Google Scholar
Rezakazemi M, Ebadi Amooghin A, Montazer-Rahmati MM, Ismail AF, Matsuura T. State-of-the-art membrane based CO2 separation using mixed matrix membranes (MMMs): an overview on current status and future directions. Prog Polym Sci 2014; 39: 817–861.10.1016/j.progpolymsci.2014.01.003Suche in Google Scholar
Rhim J-W, Park HB, Lee C-S, Jun J-H, Kim DS, Lee YM. Crosslinked poly(vinyl alcohol) membranes containing sulfonic acid group: proton and methanol transport through membranes. J Membr Sci 2004; 238: 143–151.10.1016/j.memsci.2004.03.030Suche in Google Scholar
Robeson LM. The upper bound revisited. J Membr Sci 2008; 320: 390–400.10.1016/j.memsci.2008.04.030Suche in Google Scholar
Robeson LM, Freeman BD, Paul DR, Rowe BW. An empirical correlation of gas permeability and permselectivity in polymers and its theoretical basis. J Membr Sci 2009; 341: 178–185.10.1016/j.memsci.2009.06.005Suche in Google Scholar
Rodríguez de San Miguel E, Aguilar JC, de Gyves J. Structural effects on metal ion migration across polymer inclusion membranes: dependence of transport profiles on nature of active plasticizer. J Membr Sci 2008; 307: 105–116.10.1016/j.memsci.2007.09.012Suche in Google Scholar
Samadi A, Kemmerlin RK, Husson SM. Polymerized ionic liquid sorbents for CO2 separation. Energy Fuels 2010; 24: 5797–5804.10.1021/ef101027sSuche in Google Scholar
Saroj AL, Singh RK. Thermal, dielectric and conductivity studies on PVA/Ionic liquid [EMIM][EtSO4] based polymer electrolytes. J Phys Chem Solids 2012; 73: 162–168.10.1016/j.jpcs.2011.11.012Suche in Google Scholar
Schmidt C, Glück T, Schmidt-Naake G. Modification of nafion membranes by impregnation with ionic liquids. Chem Eng Technol 2008; 31: 13–22.10.1002/ceat.200700054Suche in Google Scholar
Scholes CA, Stevens GW, Kentish SE. Membrane gas separation applications in natural gas processing. Fuel 2012; 96: 15–28.10.1016/j.fuel.2011.12.074Suche in Google Scholar
Selvam T, Machoke A, Schwieger W. Supported ionic liquids on non-porous and porous inorganic materials – a topical review. Appl Catal A 2012; 445–446: 92–101.10.1016/j.apcata.2012.08.007Suche in Google Scholar
Shahkaramipour N, Adibi M, Seifkordi AA, Fazli Y. Separation of CO2/CH4 through alumina-supported geminal ionic liquid membranes. J Membr Sci 2014; 455: 229–235.10.1016/j.memsci.2013.12.039Suche in Google Scholar
Shaplov AS, Vlasov PS, Lozinskaya EI, Ponkratov DO, Malyshkina IA, Vidal F, Okatova OV, Pavlov GM, Wandrey C, Bhide A, Schönhoff M, Vygodskii YS. Polymeric ionic liquids: comparison of polycations and polyanions. Macromolecules 2011; 44: 9792–9803.10.1021/ma2014518Suche in Google Scholar
Shaplov AS, Marcilla R, Mecerreyes D. Recent advances in innovative polymer electrolytes based on poly(ionic liquid)s. Electrochim Acta 2015; 175: 18–34.10.1016/j.electacta.2015.03.038Suche in Google Scholar
Shaplov AS, Morozova SM, Lozinskaya EI, Vlasov PS, Gouveia ASL, Tome LC, Marrucho IM, Vygodskii YS. Turning into poly(ionic liquid)s as a tool for polyimide modification: synthesis, characterization and CO2 separation properties. Polym Chem 2016; 7: 580–591.10.1039/C5PY01553GSuche in Google Scholar
Shi GM, Zuo J, Tang SH, Wei S, Chung TS. Layer-by-layer (LbL) polyelectrolyte membrane with Nexar™ polymer as a polyanion for pervaporation dehydration of ethanol. Sep Purif Technol 2015; 140: 13–22.10.1016/j.seppur.2014.11.008Suche in Google Scholar
Singh ZV, Cowan MG, McDanel WM, Luo Y, Zhou R, Gin DL, Noble RD. Determination and optimization of factors affecting CO2/CH4 separation performance in poly(ionic liquid)-ionic liquid-zeolite mixed-matrix membranes. J Membr Sci 2016; 509: 149–155.10.1016/j.memsci.2016.02.034Suche in Google Scholar
Smitha B, Suhanya D, Sridhar S, Ramakrishna M. Separation of organic-organic mixtures by pervaporation – a review. J Membr Sci 2004; 241: 1–21.10.1016/j.memsci.2004.03.042Suche in Google Scholar
Takegawa A, Murakami M, Kaneko Y, Kadokawa J. A facile preparation of composites composed of cellulose and polymeric ionic liquids by in situ polymerization of ionic liquids having acrylate groups. Polym Compos 2009; 30: 1837–1841.10.1002/pc.20756Suche in Google Scholar
Tang J, Sun W, Tang H, Radosz M, Shen Y. Enhanced CO2 absorption of poly(ionic liquid)s. Macromolecules 2005a; 38: 2037–2039.10.1021/ma047574zSuche in Google Scholar
Tang J, Tang H, Sun W, Plancher H, Radosz M, Shen Y. Poly(ionic liquid)s: a new material with enhanced and fast CO2 absorption. Chem Commun 2005b; 26: 3325–3327.10.1039/b501940kSuche in Google Scholar
Thanganathan U, Nogami M. Investigations on effects of the incorporation of various ionic liquids on PVA based hybrid membranes for proton exchange membrane fuel cells. Int J Hydrogen Energy 2015; 40: 1935–1944.10.1016/j.ijhydene.2014.11.099Suche in Google Scholar
Tomé LC, Isik M, Freire CSR, Mecerreyes D, Marrucho IM. Novel pyrrolidinium-based polymeric ionic liquids with cyano counter-anions: high performance membrane materials for post-combustion CO2 separation. J Membr Sci 2015; 483: 155–165.10.1016/j.memsci.2015.02.020Suche in Google Scholar
Ulewicz M, Radzyminska-Lenarcik E. Application of polymer and supported membranes with 1-decyl-4-methylimidazole for pertraction of transition metal ions. Sep Sci Technol 2014; 49: 1713–1721.10.1080/01496395.2014.906453Suche in Google Scholar
Upitis A, Peterson J, Lukey C, Nghiem LD. Metallic ion extraction using polymer inclusion membranes (PIMs): optimising physical strength and extraction rate. Desalin Water Treat 2009; 6: 41–47.10.5004/dwt.2009.641Suche in Google Scholar
Uragami T, Fukuyama E, Miyata T. Selective removal of dilute benzene from water by poly(methyl methacrylate)-graft-poly(dimethylsiloxane) membranes containing hydrophobic ionic liquid by pervaporation. J Membr Sci 2016; 510: 131–140.10.1016/j.memsci.2016.01.057Suche in Google Scholar
van de Ven E, Chairuna A, Merle G, Benito SP, Borneman Z, Nijmeijer K. Ionic liquid doped polybenzimidazole membranes for high temperature Proton Exchange Membrane fuel cell applications. J Power Sources 2013; 222: 202–209.10.1016/j.jpowsour.2012.07.112Suche in Google Scholar
Venkateswaran P, Gopalakrishnan AN, Palanivelu K. Di(2-ethylhexyl)phosphoric acid-coconut oil supported liquid membrane for the separation of copper ions from copper plating wastewater. J Environ Sci 2007; 19: 1446–1453.10.1016/S1001-0742(07)60236-8Suche in Google Scholar
Voss BA, Bara JE, Gin DL, Noble RD. Physically gelled ionic liquids: solid membrane materials with liquidlike CO2 gas transport. Chem Mater 2009; 21: 3027–3029.10.1021/cm900726pSuche in Google Scholar
Wang J, Luo J, Feng S, Li H, Wan Y, Zhang X. Recent development of ionic liquid membranes. Green Energ Environ 2016; 1: 43–61.10.1016/j.gee.2016.05.002Suche in Google Scholar
Washiro S, Yoshizawa M, Nakajima H, Ohno H. Highly ion conductive flexible films composed of network polymers based on polymerizable ionic liquids. Polymer 2004; 45: 1577–1582.10.1016/j.polymer.2004.01.003Suche in Google Scholar
Wijmans JG, Baker RW. The solution-diffusion model – a review. J Membr Sci 1995; 107: 1–21.10.1016/0376-7388(95)00102-ISuche in Google Scholar
Yampolskii Y. Polymeric gas separation membranes. Macromolecules 2012; 45: 3298–3311.10.1021/ma300213bSuche in Google Scholar
Yang Y, Gao HJ, Lu F, Zheng LQ. Preparation and characterization of composite membranes with Bronsted acidic ionic liquid. Colloid Polym Sci 2014; 292: 2831–2839.10.1007/s00396-014-3324-7Suche in Google Scholar
Yasuda T, Nakamura S, Honda Y, Kinugawa K, Lee SY, Watanabe M. Effects of polymer structure on properties of sulfonated polyimide/protic ionic liquid composite membranes for nonhumidified fuel cell applications. ACS Appl Mater Interfaces 2012; 4: 1783–1790.10.1021/am300031kSuche in Google Scholar PubMed
Ye H, Huang J, Xu JJ, Kodiweera NKAC, Jayakody JRP, Greenbaum SG. New membranes based on ionic liquids for PEM fuel cells at elevated temperatures. J Power Sources 2008; 178: 651–660.10.1016/j.jpowsour.2007.07.074Suche in Google Scholar
Yi S, Zhang F, Li W, Huang C, Zhang H, Pan M. Anhydrous elevated-temperature polymer electrolyte membranes based on ionic liquids. J Membr Sci 2011; 366: 349–355.10.1016/j.memsci.2010.10.031Suche in Google Scholar
Yongquan D, Ming W, Lin C, Mingjun L. Preparation, characterization of P(VDF-HFP)/[bmim]BF4 ionic liquids hybrid membranes and their pervaporation performance for ethyl acetate recovery from water. Desalination 2012; 295: 53–60.10.1016/j.desal.2012.03.018Suche in Google Scholar
Yoon J, Lee HJ, Stafford CM. Thermoplastic elastomers based on ionic liquid and poly(vinyl alcohol). Macromolecules 2011; 44: 2170–2178.10.1021/ma102682kSuche in Google Scholar
Yoshizawa M, Ogihara W, Ohno H. Novel polymer electrolytes prepared by copolymerization of ionic liquid monomers. Polym Adv Technol 2002; 13: 589–594.10.1002/pat.261Suche in Google Scholar
Yuan JY, Mecerreyes D, Antonietti M. Poly(ionic liquid)s: an update. Prog Polym Sci 2013; 38: 1009–1036.10.1016/j.progpolymsci.2013.04.002Suche in Google Scholar
Yue CB, Fang D, Liu L, Yi TF. Synthesis and application of task-specific ionic liquids used as catalysts and/or solvents in organic unit reactions. J Mol Liq 2011; 163: 99–121.10.1016/j.molliq.2011.09.001Suche in Google Scholar
Zhang Y, Kogelnig D, Morgenbesser C, Stojanovic A, Jirsa F, Lichtscheidl-Schultz I, Krachler R, Li Y, Keppler BK. Preparation and characterization of immobilized [A336][MTBA] in PVA-alginate gel beads as novel solid-phase extractants for an efficient recovery of Hg(II) from aqueous solutions. J Hazard Mater 2011; 196: 201–209.10.1016/j.jhazmat.2011.09.018Suche in Google Scholar PubMed
Zhang G-R, Munoz M, Etzold BJM. Boosting performance of low temperature fuel cell catalysts by subtle ionic liquid modification. ACS Appl Mater Interfaces 2015; 7: 3562–3570.10.1021/am5074003Suche in Google Scholar PubMed
Zhang Y, Ji X, Xie Y, Lu X. Screening of conventional ionic liquids for carbon dioxide capture and separation. Appl Energy 2016; 162: 1160–1170.10.1016/j.apenergy.2015.03.071Suche in Google Scholar
Zhao H, Xia S, Ma P. Use of ionic liquids as “green” solvents for extractions. J Chem Technol Biotechnol 2005; 80: 1089–1096.10.1002/jctb.1333Suche in Google Scholar
Zhou HL, Su Y, Wan YH. Phase separation of an acetone-butanol-ethanol (ABE)-water mixture in the permeate during pervaporation of a dilute ABE solution. Sep Purif Technol 2014; 132: 354–361.10.1016/j.seppur.2014.05.051Suche in Google Scholar
©2019 Wojciech Kujawski et al., published by De Gruyter, Berlin/Boston
This work is licensed under the Creative Commons Attribution 4.0 Public License.
Artikel in diesem Heft
- Frontmatter
- In this issue
- Kinetic theory based multiphase flow with experimental verification
- Advances in chemical product design
- Application of polymer-based membranes containing ionic liquids in membrane separation processes: a critical review
- Liposomes as colloidal nanovehicles: on the road to success in intravenous drug delivery
- On the performance of immobilized cell bioreactors utilizing a magnetic field
- An overview of the reaction conditions for an efficient photoconversion of CO2
- Adsorption removal of malachite green dye from aqueous solution
Artikel in diesem Heft
- Frontmatter
- In this issue
- Kinetic theory based multiphase flow with experimental verification
- Advances in chemical product design
- Application of polymer-based membranes containing ionic liquids in membrane separation processes: a critical review
- Liposomes as colloidal nanovehicles: on the road to success in intravenous drug delivery
- On the performance of immobilized cell bioreactors utilizing a magnetic field
- An overview of the reaction conditions for an efficient photoconversion of CO2
- Adsorption removal of malachite green dye from aqueous solution
