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Significant Acceleration of PGMs Extraction with UCSTtype Thermomorphic Ionic Liquid at Elevated Temperature Soma Kono, Hiroyuki Kazama, Takahiro Mori, Tsuyoshi Arai, and Koichiro Takao ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b04447 • Publication Date (Web): 18 Jan 2018 Downloaded from http://pubs.acs.org on January 19, 2018
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ACS Sustainable Chemistry & Engineering
Significant Acceleration of PGMs Extraction with UCST-type Thermomorphic Ionic Liquid at Elevated Temperature Soma Kono†, Hiroyuki Kazama‡, Takahiro Mori‡, Tsuyoshi Arai§,*, and Koichiro Takao‡,*
†
Shibaura Institute of Technology Graduate School of Engineering, 3-7-5, Toyosu, Koto-ku, Tokyo 135-8548, Japan
‡
Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Technology, 2-12-1 N1-32, Ookayama, Meguro-ku, Tokyo 152-8550, Japan §
Shibaura Institute of Technology, 3-7-5, Toyosu, Koto-ku, Tokyo 135-8548, Japan
*To whom correspondence should be addressed. E-mail:
[email protected] (T.A.),
[email protected] (K.T.)
ABSTRACT: Dependency of extraction behavior of inert platinum group metals (PGMs) like Ru(III) and Rh(III) on temperature has been investigated in a biphasic system consisting of HNO3(aq) and betainium bis(trifluoromethylsulfonyl)amide ([Hbet][Tf2N]) ionic liquid. The extraction reactions of Ru(III) and Rh(III) took 3.5 days and 113 days, respectively, at 298 K, while were equilibrated within 1 h and 3 h to reach 99.2 % and 96.5 % extraction at 353 K. Further mechanistic studies clarified that the + complexation of these PGMs and [Hbet] is rate-determining in their extraction, and that it is successfully accelerated and enhanced by elevating the temperature.
+
and trimethylglycinium (or betainium, [Hbet] ) bis(trifluoromethylsulfonyl)amide ([Tf2N] ) is enough hydrophobic to form an organic phase immiscible with water at room temperature, whereas these layers are completely miscible with each other above 55°C, namely upper-critical solution temperature (UCST).18 24 Therefore, [Hbet][Tf2N] (Figure 1(a)) is highly promising for an energy-saving extraction process, because ultimately homogeneous mixing of the aqueous/IL biphasic system is facilitated only by heating.
KEYWORDS: Ionic liquid, Solvent extraction, Platinum group, Upper critical solution temperature, Thermomorphism, Betainium.
■ INTRODUCTION The ionic liquids (ILs) are commonly defined as organic salts which melt below 100°C. They have unique properties, e.g., nonflammability, nonvolatility, high conductivity, and diversity of combination of cation and anion. Especially, it is possible to synthesize an IL with potential to extract metal ions n+ (M ) due to introducing a functional groups on either its cationic or anionic components. Because of these properties, n+ the use of ILs as an extraction solvent for M has been fre1–8 quently investigated. The above characteristics make these extraction systems more environment-friendly compared with the ordinary organic/aqueous biphasic systems. One of 9 expected applications is treatment of radioactive wastes. For example, platinum group metals (PGMs) like Ru, Rh, and Pd in the high-level liquid wastes are sometimes problematic in 10,11 the vitrification process. Hence, removal of these PGMs is significantly required. On this context, we are investigating the potential of ILs in the PGMs extraction. A few ILs undergo a temperature-responsive behavior, which shows transition of miscibility of IL with an aqueous solution at a critical 12 – 17 temperature. Especially, an IL consisting of N,N,N-
Figure 1. Schematic structures of bis(trifluoromethylsulfonyl)amide salts of (a) trimethylglycinium ([Hbet][Tf2N]) and (b) trimethylpropylammonium ([TMPA][Tf2N]) employed in this study. Furthermore, [Hbet][Tf2N] has an extraction ability for varin+ 24, 25 ous M including PGMs. According to our previous report, we have preliminarily employed [Hbet][Tf2N] to recover Ru(III), Rh(III), and Pd(II) from HNO3(aq) under vigorous shaking at 25°C. In these attempts, high extractability (E% > 90%) was recorded for Pd(II). In contrast, E% of Ru(III) and Rh(III) were not high enough (35% and 68% at the maximum, respectively). According to a review by Helm and Merbach, lifetimes of a water molecule in the first coordina3+ 3+ tion sphere (τH2O) of Ru and Rh are in the order of days 2+ −3 and years, respectively, while that of Pd is 10 s.26 Therefore, the low extractability of Ru(III) and Rh(III) could be ascribed to their inertness in the ligand substitution reactions. In general, heating is effective as a method to accelerate a slow chemical reaction. In order to promote the extraction of these inert PGMs, we employed microwave (MW) 27 heating. As a result, we have demonstrated that the liquid− liquid extraction of the inert PGMs is significantly accelerat-
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ACS Sustainable Chemistry & Engineering ed under the MW heating. However, it is not still clearly un27 derstood what drives the extraction of the inert PGMs. To answer this question, we studied the extraction behavior of the above PGMs under the convection heating in the HNO3(aq)/[Hbet][Tf2N] systems. ■ EXPERIMENTAL SECTION
n+
n+
E% = 100 × ([M ]aq･init – [M ]aq)/[M ]aq･init n+
n+
n+
D = ([M ]aq･init – [M ]aq)/[M ]aq n+
n+
80 60 40
Ruthenium(III) nitrosyl nitrate solution (Strem Chemicals Co., Ltd), Rhodium(III) nitrate (Kanto Chemical Co., Ltd), and Pd nitrate solution (Tanaka Kikinnzoku Kogyo Co., Ltd) n+ were employed as M sources. [Hbet][Tf2N] used in this study was pre-equilibrated upon contact with aqueous solutions containing HNO3 in different concentrations, which were the same as the HNO3(aq) phase in the following extraction experiments. Note that extraction chemistry of each n+ M was individually studied in separate batches. The HNO3(aq) dissolving Ru(III), Rh(III), or Pd(II) were put into a centrifuge tube together with the pre-equilibrated [Hbet][Tf2N] in 1:1 (v/v) ratio. Each mixture was shaken at 160 rpm in a thermostatic shaking bath (ADVANTEC, TBK202HA). The aqueous layer was subjected to determine n+ the M concentration with ICP-AES (Thermo Fisher Scientific Co., Ltd, iCAP7200 DUO). Prior to this analysis, sample mixtures tested at > 328 K were cooled in an ice bath, and then centrifuged. The extraction efficiency (E%) and the disn+ tribution ratio (D) of each M were calculated by the following equations. n+
100
E%
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
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(1) (2)
: Ru(III) : Rh(III) : Pd(II)
20 0 0
1
2 hour
1
2
3
50
4 day
100
150 day
Time elapsed n+
Figure 2. Progress of extraction of each M in terms of E% n+ at 298 K as a function of elapsed time. Condition: [M ] = 3 mM, [HNO3] = 0.3 M. Note that any additional chemicals like extractants were not dissolved in the current extraction systems. As we reported n+ previously, the extraction of these M is initiated by coordination of the carboxylic group of the zwitterionic betaine + (bet) arising from deprotonation of [Hbet] .28 This means n+ that the hydrated water molecules bound to M have to be substituted by bet to form an extractable species. If the reacn+ tivity of M is extremely low, the rate of such a ligand substitution reaction is also slow, affording the slow extraction 3+ kinetics. This could be the reason why the extraction of Ru 3+ and Rh are extremely sluggish. In summary, the extraction n+ kinetics of M studied here is strongly governed by their intrinsic lability.
n+
where [M ]aq･init and [M ]aq denote the M concentrations in the aqueous phase at the initial state and after the extraction, respectively. UV-vis absorption spectra of sample solutions were recorded by Agilent 8453 photodiode-array spectrophotometer equipped with Peltier thermostatic controller. ■ RESULT AND DISCUSSION Extraction Kinetics at 298 K. We investigated extraction kinetics of Ru(III), Rh(III), and Pd(II) to [Hbet][Tf2N] at 298 n+ K. Figure 2 shows E% of each M as a function of the shaking time in 0.3 M HNO3(aq)/[Hbet][Tf2N] biphasic system at 298 K. To reach the extraction equilibrium of Ru(III) at 298 K, it took 3.5 days. The extraction kinetics of Rh(III) was even much slower, and took 113 days. In contrast, Pd(II) is rapidly extracted within 2 min. These results clearly indicate that Ru(III) and Rh(III) are extremely inactive in the current extraction system, but still possess potentials to be extracted in high efficiencies. The observed difference in the extraction n+ kinetics can be ascribed to reactivity of these M . A lifetime of a hydrated water molecule (τH2O) in the ligand exchange n+ reaction is known to be a measure of the lability of M . Ac3+ 3+ 2+ cording to Helm and Merbach, τH2O of Rh , Ru , and Pd 26 are 14 years, 3.3 days, and 1.8 ms, respectively, demonstratn+ ing that the reactivity of these M are greatly different from each other. The order of τH2O (Rh(III) > Ru(III) > Pd(II)) is exclusively in line with that of the progress of extraction shown in Figure 2.
Acceleration of Inert PGMs Extraction. From the experimental results at 298 K (Figure 2), it was clear that the extraction kinetics of Ru(III) and Rh(III) were much slower than Pd(II). At the same time, we can still expect high E% n+ even for these inert M . Thus, it is necessary to somehow improve their extraction kinetics. In general, heating is effective as a method to accelerate a slow chemical reaction. Herein, we investigated how the extraction kinetics of Ru(III) and Rh(III) are affected by temperature under convection heating. Figure 3 shows progress of extraction of Ru(III) and Rh(III) at different temperatures. As a result, the extraction of Ru(III) was completed within 1 h at 353 K, while that of Rh(III) was equilibrated within 3 h at the same temperature condition. These results are dramatically faster than those at 298 K shown in Figure 2 (3.5 days for Ru(III), 113 days for Rh(III)). Consequently, the extraction kinetics of both Ru(III) and Rh(III) were successfully much improved at the elevated temperatures as expected. Although kinetics of a chemical reaction is actually affected by temperature, we also know that the extraction kinetics may also depend on the phase transfer of an extractable species between the aqueous and organic phases. As described above, the thermomorphic behavior of the [Hbet][Tf2N]− water mixture to form a homogeneous phase above 328 K may facilitate the ultimate mixing of the aqueous and organ16,18-24 ic layers in the current extraction systems, which strongly assists the phase transfer of the extractable Ru(III) and Rh(III) species. Therefore, it is still unclear at this stage
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what actually drives the Ru(III) and Rh(III) extraction at the elevated temperatures in Figure 3.
0.8
100 0.28 90 0.26
0.6
80
Absorbance
100 80
60
E%
E%
60
40
E%
100
80 0.24 Rh(III)
70
0.22
: E%
0.4
: Abs.
60 0
50
100
Abs.@400 nm
Time / min :0 :2 :5 : 10 : 30 : 60 : 120 : 180 : 240
0.2
150
Time elapsed / min
0.2
40 Ru(III) : 298 K
20
: 333 K
Rh(III) : 333 K
: 353 K
0
0
: 298 K
20
300
: 353 K
400
0
0
50
100
150
Time elapsed / min
0 100 200 300
1250
Time elapsed / min n+
Figure 3. Progress of extraction of each inert M in terms of E% at different temperatures (298, 333, 353 K) as a function n+ of elapsed time. [M ] = 3 mM, [HNO3] = 0.3 M. Left: Ru(III), right: Rh(III). Based on these considerations, we decided to study the pron+ gress of the ligand substitution reaction of M by means of the UV–vis absorption spectroscopy. [Hbet][Tf2N] and 0.3 M HNO3(aq) dissolving 3 mM Rh(III) were mixed in 1:1 (v/v) ratio at 353 K, followed by recording UV-vis absorption spectra of this mixture sequentially. Figure 4 shows a series of the recorded spectra. As a result, the intensity of the absorption 1 1 band centered at 400 nm arising from the T1g ←A1g transition 3+ , of Rh 29 30 increased with elapse of time. This result indicates that the complex formation of Rh(III) with + [Hbet][Tf2N], probably the carboxylic group of [Hbet] , proceeds. As displayed in the inset of Figure 4, E% of Rh(III) shows the similar trend to the absorbance at 400 nm with elapse of time. Therefore, the formation of the extractable complex is the rate-determining step of the Rh(III) extraction in the current system. We also performed the same experiments for Ru(III) and Pd(II). The results are shown in Figure S1 in the Supporting Information. Although Ru(III) does not exhibit any distinctive absorption bands in the UV-vis region, formation of its extractable species also seems to be correlated with the extraction kinetics as shown in the inset. Any large deviation from the initial spectrum has not been observed in the Ru(III) absorption spectrum, implying that the 3+ nitrosyl ligand still remains coordinated to Ru even after the formation of the extractable species. Regarding Pd(II), its reaction with [Hbet][Tf2N] is immediately equilibrated within 2 min as shown in Figure S1. This result is enough predict2+ able from the lability of Pd , and in line with its rapid extraction even at 298 K (Figure 2).
500
600
Wavelength / nm Figure 4. UV-visible absorption spectra of a 1:1(v/v) mixture 3+ of [Hbet][Tf2N] and 0.3 M HNO3(aq) containing Rh (1.5 mM 3+ in total) at 353 K together with Rh (1.5 mM) in 0.3 M HNO3(aq) (black curve). Inset: progress of extraction (E%) and absorbance at 400 nm at 353 K as functions of elapsed time. Effect of [HNO3] at Different Temperature. Our next concern is whether or not the temperature of the system also affects the extraction behavior of PGMs under different [HNO3] conditions. Based on the results of Figure 3, the equilibration time was set to 1 h for Ru(III) and 3 hours for Rh(III). The extraction behavior of Ru(III), Rh(III), and Pd(II) in the HNO3(aq)/[Hbet][Tf2N] systems at different [HNO3] and temperature are shown in Figure 5. 100 Ru(III)
Rh(III)
Pd(II)
80 60
E%
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40 20 0 -1 10
: 298 K : 333 K : 353 K 0
10
1 10 10
-1
10
0
1
10 10-1
100
101
[HNO ] / M 3
Figure 5. Dependence of the extraction efficiency (E%) of n+ M on [HNO3] in HNO3(aq)–[Hbet][Tf2N] systems. n+
As seen from this figure, the highest E% of each M was n+ observed for each M at [HNO3] = 0.3 M. From this result, it was clarified that [HNO3] should be as low as possible for efficiently extracting Ru(III), Rh(III), or Pd(II). However, we also have to pay attention to the hydrolysis of them. As we discussed previously, the minimum [HNO3] should be 0.3 M n+ 25 to prevent significant hydrolysis of these M . Taking into account the slow development of E% observed in Figure 2, the extraction of Ru(III) and Rh(III) at 298 K and 333 K has not been equilibrated in the current experimental conditions. In contrast, the extraction of Pd(II) is extremely rapid under any of [HNO3] conditions tested here. As a general
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ACS Sustainable Chemistry & Engineering n+
Extraction Mechanism. To gain further mechanistic insights into the PGMs extraction in the current system, the n+ extraction behavior of each M was carefully investigated in terms of the distribution ratio (D). We already know that + [Hbet] is certainly involved in the extraction mechanism. However, it is quite difficult to vary its concentration, because the organic phase consists of [Hbet][Tf2N] itself. On this context, we decided to employ [TMPA][Tf2N] as a “spectating diluent”, where [Hbet][Tf2N] was dissolved as an “ex+ tractant”. Figure 6 shows the dependency of D on [[Hbet] ] + and [H ]. 2.4 (b)
1.6
log D
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
trend, E% of M tends to decrease with an increase in + [HNO3]. This implies that deprotonation from [Hbet] is included in the extraction process. When [TMPA][Tf2N] (Figure 1(b)) is employed instead of [Hbet][Tf2N], no extraction of Ru(III), Rh(III), and Pd(II) were detected even at 353 K (Figure S2, Supporting Information). This result clearly + indicates that the carboxylic group of [Hbet] plays an important role in the extraction of Ru(III), Rh(III), and Pd(II) in the HNO3(aq)/[Hbet][Tf2N] systems.
0.8
0
-0.8 -0.4
0
+
0.4
0.8
log [H ]
Figure 6. Distribution ratio (D) of Ru(III), Rh(III), and Pd(II) + as functions of (a) [[Hbet] ] in 0.3 M + HNO3(aq)/[TMPA][Tf2N] and (b) [H ] in (H,Na)NO3(aq)/[Hbet][Tf2N] (total [NO3 ]: 3.00 M). Initial condition: [Ru(III)] = 7 mM, [Rh(III)] = 3 mM, [Pd(II)] = 5 mM, T = 353 K.
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mechanism of Ru(III), Rh(III), and HNO3(aq)/[Hbet][Tf2N] system as follows. 3+
RuNO 3+
Rh Pd
2+
aq
aq
+ 2[Hbet]
+ 2[Hbet]
aq + [Hbet]
+
+ IL
+ IL
= [RuNO(bet)2]
= [Rh(bet)2] +
IL = [Pd(bet)]
2+ IL
+
2+
IL + + 2H aq
+
2H
+
IL + H
Pd(II)
aq
aq
in
(3) (4) (5)
where the subscripted “aq” and “IL” indicate location of species. The nitrosyl ligand is supposed to remain coordinated 3+ to Ru in accordance with the above discussion regarding the absorption spectrum. To compensate the charge balance − between the phases, [Tf2N] might be involved in the extraction process to form an ion-pair with the extractable species of PGMs. Alternatively, cation exchange of the PGM-bet + complexes with an additional [Hbet] IL could also be another choice to compensate the charge distribution between the phases. ■ CONCLUSION To answer what drives the extraction of the inert PGMs from HNO3(aq) to the thermomorphic [Hbet][Tf2N] ionic liquid, we studied the distribution behavior of Ru(III) and Rh(III) at different temperatures as well as that of Pd(II), the labile PGM. As a result, the kinetics of the extraction reactions of the inert PGMs were successfully improved at the elevated + temperatures. Their interaction with [Hbet] to form extractable species is the rate-determining step, which has been successfully accelerated by the convection heating. Thus, the extraction of these inert PGMs seems to be simply temperature-controlled regardless of the heating methods like convection and microwave. The extraction mechanism of Ru(III), Rh(III) and Pd(II) in the current extraction system is concluded to follow the formation of the PGM:bet complexes + to release H to the aqueous phase. Further detailed investigations are currently ongoing, for instance, separation from n+ other M , preparation and characterization of the extractable PGM:bet complexes, and stripping behavior of the extracted PGMs from [Hbet][Tf2N]. We wonder that the backextraction kinetics would also be affected by the temperature.
n+
In Figure 6(a), log D of each M linearly increases with an + + increase in [[Hbet] ]. The slopes of these log D-log [[Hbet] ] plots for Ru(III), Rh(III), and Pd(II) were evaluated as 2.05 ± 0.16, 1.99 ± 0.07, and 1.15 ± 0.03, respectively. These results + are suggestive of the stoichiometry of [Hbet] involved in the n+ n+ extraction of each M , namely the M :bet ratios in the extractable species of Ru(III), Rh(III), and Pd(II) would be 1:2, 1:2, and 1:1, respectively. This means that the equal number of + + H should be released from [Hbet] in the extraction process. n+ Similarly, in Figure 6(b), log D of each M linearly decreases + + with an increase in [H ]. The slopes of these log D-log [H ] plots for Ru(III), Rh(III), and Pd(II) were evaluated as -2.16 ± 0.11, -1.88 ± 0.05, and -0.92 ± 0.09, respectively. These results + are suggestive of the stoichiometry of [H ] involved in the n+ extraction of each M , namely the deprotonation of carboxyl + group with decreasing [H ] should promote the complex n+ formation with each M . In Figure S3, any significant dependency of E% and log D on [NO3 ] have not been observed, − indicating little effect of [NO3 ] to the extraction. Referring n+ to the M :bet stoichiometry, we propose the extraction
■ ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: UV-visible absorption spectra of a 1:1(v/v) mixture of 3+ 2+ [Hbet][Tf2N] and 0.3 M HNO3(aq) containing Ru or Pd at n+ 353 K; Extraction behavior of each M in [Hbet][Tf2N]– HNO3(aq) and [TMPA][Tf2N]–HNO3(aq) systems at 353 K; Extraction behavior of each PGM as a function of [NO3 ] in HNO3(aq)/[Hbet][Tf2N] (PDF) ■ AUTHOR INFORMATION Corresponding Authors *T. Arai. E-mail:
[email protected]. *K. Takao. E-mail:
[email protected]. Notes
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ACS Sustainable Chemistry & Engineering The authors declare no competing financial interest. ■ ACKNOWLEDGMENT We thank Prof. Emer. Yasuhisa Ikeda for stimulating discussion and helpful advice. This work is the result of the “Development of Rapid Extraction Method for Platinum-Group Metals Difficult to Be Extracted” entrusted by Japan Oil, Gas and Metals National Corporation. ■ REFERENCES (1) Wei, T. G.; Yang, Z.; Chen. J. C. Room temperature ionic liquid as a novel medium for liquid/liquid extraction of metal ions.
Anal. Chim. Acta 2003, 488, 183–193. DOI: 10.1016/S0003-2670(03)00660-3 (2) Visser, E. A.; Swatloski, P. R.; Reichert, M. W.; Mayton, R.; Sheff, S.; Wierzbicki, A.; Davis, Jr, H. J.; Rogers, D. R. Taskspecific ionic liquids for the extraction of metal ions from aqueous solutions. Chem. Commun. 2001, 135–136. DOI: 10.1039/B008041L (3) Nakashima, K.; Kubota, F.; Maruyama, T.; Goto, M. Ionic Liquids as a Novel Solvent for Lanthanide Extraction. Anal. Sci. 2003, 19, 1097–1098. DOI: 10.2116/analsci.19.1097 (4) Shimojo, K.; Goto, M.; Solvent Extraction and Stripping of Silver Ions in Room-Temperature Ionic Liquids Containing Calixarenes. Anal. Chem. 2004, 76, 5039–5044. DOI: 10.1021/ac049549x (5) Zhao, H.; Xia, S.; Ma, P.
Use of ionic liquids as ‘green’ solvents for extractions. Chem. Technol. Biotechnol. 2005, 80, 1089– 1096. DOI: 10.1002/jctb.1333 (6) Billard, I.; Ouadi, A.; Gaillard, C. Liquid–liquid extraction of actinides, lanthanides, and fission products by use of ionic liquids: from discovery
to understanding. Anal. Bioanal. Chem. 2011, 400, 1555–1566. DOI: 10.1007/s00216-010-4478-x (7) Dietz, L. M.; Dzielawa, A. J. Ion-exchange as a mode of cation transfer into room-temperature ionic liquids containing crown ethers: implications for the ‘greenness’ of ionic liquids as diluents in liquid–liquid extraction. Chem. Commun. 2001, 20, 2124–2125. DOI: 10.1039/B104349H (8) Park, J.; Jung, Y.; Kusumah, P.; Lee, J.; Kwon, K.; Lee, K. C. Application of Ionic Liquids in Hydrometallurgy. Int. J. Mol. Sci. 2014, 15, 15320–15343. DOI: 10.3390/ijms150915320 (9) Sun, X.; Luo, H,; Dai, S. Ionic Liquids-Based Extraction: A Promising Strategy for the Advanced Nuclear Fuel Cycle. Chem. Rev. 2012, 112, 2100–2128. DOI: 10.1021/cr200193x (10) Kolarik, Z.; Renard, V. E. Recorvery of Value Fission Platinoids from Spent Nuclear Fuel. Platinum Met. Rev. 2003, 47, 74– 87. (11) Newman, R. J.; Smith, F. J. Platinum Metals from Nuclear Fission. Platinum Met. Rev. 1970, 14, 88–92. ( 12 ) Kohno, Y.; Ohno, H. Temperature-responsive ionic liquid/water interfaces: relation between hydrophilicity of ions and dynamic phase change. Phys. Chem. Chem. Phys. 2012, 14, 5063– 5070. DOI: 10.1039/C2CP24026B (13) Kohno, Y.; Saita, S.; Murata, K.; Nakamura, N.; Ohno, H. Extraction of proteins with temperature sensitive and reversible phase change of ionic liquid/water mixture. Polym. Chem. 2011, 2, 862–867. DOI: 10.1039/C0PY00364F (14) Kohno, Y.; Arai, H.; Saita, S.; Ohno, H. Material design of ionic liquids to show temperature-sensitive LCST-type phase transition after mixing with water. Aust. J. Chem. 2011, 64, 1560– 1567. DOI: 10.1071/CH11278
(15) Onghena, B.; Jacobs, J.; Meervelt, L. V.; Binnemans, K. Homogeneous liquid-liquid extraction of neodymium(III) by choline hexafluoroacetylacetonate in the ionic liquid choline bis(trifluoromethylsulfonyl)imide. Dalton Trans. 2014, 43, 11566–11578. DOI: 10.1039/c4dt01340a (16) Dupont, D.; Depuydt, D.; Binnemans, K. Overview of the effect of salts on biphasic ionic liquid/water solvent extraction systems: anion exchange, mutual solubility, and thermomorphic properties. J. Phys. Chem. B 2015, 119, 6747–6757. DOI: 10.1021/acs.jpcb.5b02980 (17) Nitta, A.; Morita, T.; Saita, S.; Kohno, Y.; Ohno, H.; Nishikawa, K. solution of ionic liquid with lower critical solution temperature: Mixture of tetrabutylphosphonium trifluoroacetate and water. Chem. Phys. Lett. 2015, 628, 108–112. DOI: 10.1016/j.cplett.2015.03.026 (18) Nockemann, P.; Thijs, B.; Pittois, S.; Thoen, J.; Glorieux, C.; Van Hecke, K.; Van Meervelt, L.; Kirchner, B.; Binnemans, K. Task-specific ionic liquid for solubilizing metal oxides. J. Phys. Chem. B 2006, 110, 20978−20992. DOI: 10.1021/jp0642995 (19) Nockemann, P.; Van Deun, R.; Thijs, B.; Huys, D.; Vanecht, E.; Van Hecke, K.; Van Meervelt, L.; Binnemans, K. Uranyl complexes of carboxyl-functionalized ionic liquids. Inorg. Chem. 2010, 49, 3351−3360. DOI: 10.1021/ic902406h (20) Hoogerstraete, T. V.; Onghena, B.; Binnemans, K. Homogeneous Liquid−Liquid Extraction of Metal Ions with a Functionalized Ionic Liquid. J. Phys. Chem. Lett. 2013, 4, 1659−1663. DOI: 10.1021/jz4005366 (21) Hoogerstraete, T. V.; Onghena, B.; Binnemans, K. Homogeneous Liquid–Liquid Extraction of Rare Earths with the Betaine—Betainium Bis(trifluoromethylsulfonyl)imide Ionic Liquid System. Int. J. Mol. Sci. 2013, 14, 21353–21377. 10.3390/ijms141121353 (22 ) Dupont, D.; Binnemans, K. Rare-earth recycling using a functionalized ionic liquid for the selective dissolution and revalorization of Y2O3:Eu3+ from lamp phosphor waste. Green Chem. 2015, 17, 856−868. DOI: 10.1039/C4GC02107J (23) Dupont, D.; Binnemans, K. Recycling of rare earths from NdFeB magnets using a combined leaching/extraction system based on the acidity and thermomorphism of the ionic liquid [Hbet][Tf2N]. Green Chem. 2015, 17, 2150 − 2163. DOI: 10.1039/C5GC00155B ( 24 ) Onghena, B.; Binnemans,
K. Recovery of Scandium(III) from Aqueous Solutions by Solvent Extraction with the Functionalized Ionic Liquid Betainium Bis(trifluoromethylsulfonyl)imide. Ind. Eng. Chem. Res. 2015, 54, 1887 − 1898. DOI: 10.1021/ie504765v (25) Sasaki, K.; Takao, K.; Suzuki, T.; Mori, T.; Arai, T.; Ikeda, Y. Extraction of Pd(II), Rh(III) and Ru(III) from HNO3 aqueous solution to betainium bis(trifluoromethanesulfonyl)imide ionic liquid. Dalton Trans. 2014, 43, 5648 − 5651. DOI: 10.1039/C4DT00091A (26) Helm, L.; Merbach, A. E. Inorganic and bioinorganic solvent exchange mechanisms. Chem. Rev. 2005, 105, 1923−1959. DOI: 10.1021/cr030726o (27) Ikeda, S.; Mori, T.; Ikeda, Y.; Takao, K Microwave-Assisted Solvent Extraction of Inert Platinum Group Metals from HNO3(aq) to Betainium-Based Thermomorphic Ionic Liquid. ACS Sustainable Chem. Eng. 2016, 4, 2459–2463. DOI: 10.1021/acssuschemeng.6b00186 (28) Mori, T.; Takao, K.; Sasaki, K.; Suzuki, T.; Arai, T.; Ikeda, Y. Homogeneous liquid–liquid extraction of U(VI) from HNO3 aqueous solution to betainium bis(trifluoromethylsulfonyl)imide
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ionic liquid and recovery of extracted U(VI). Sep. Purif. Technol. 2015, 115, 113–138. DOI: 10.1016/j.seppur.2015.01.045 (29) Jørgensen, C. K. Complexes of the 4d- and 5d-Groups I. Crystal Field Spectra of Rhodium(III) and Iridium(III). Acta Chem. Scand. 1956, 10, 500–517. DOI: 10.3891/acta.chem.scand.10-0500 (30) Schmidtke, H.-H. Electronic Spectra of Rh(III)- and Ir(III)Hexamminechloride. J. Mol. Spectrosc. 1963, 11, 483-485. DOI: 10.1016/0022-2852(63)90048-1
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Extraction kinetics of Ru(III) and Rh(III) from HNO3(aq) to [Hbet][Tf2N] are much improved at the elevated temperature under convection heating.
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