Environ. Sci. Technol. 2010, 44, 7504–7508
Pseudo-Emulsion Membrane Strip Dispersion (PEMSD) Pertraction of Chromium(VI) Using CYPHOS IL101 Ionic Liquid as Carrier FRANCISCO JOSE ALGUACIL,* MANUEL ALONSO, FELIX A. LOPEZ, AND AURORA LOPEZ-DELGADO Centro Nacional de Investigaciones Metallurgicas (CSIC), Avda. Gregorio del Amo 8, Ciudad Universitaria, 28040 Madrid, Spain
Received April 26, 2010. Revised manuscript received July 28, 2010. Accepted July 30, 2010.
The transport of chromium(VI) from hydrochloric acid medium by pseudoemulsion membrane strip dispersion (PEMSD), using CYPHOS IL101 (phosphonium salt) as ionophore, is investigated under various experimental variables in the feed phase [hydrodynamic conditions, concentration of Cr(VI) (0.01-1 g/L), concentration of HCl (0.01-1M)], in the organic phase [carrier concentration (1-10% v/v)], and in the strip phase (stripping agent). Other variables investigated were the volume organic/strip phase ratios in the pseudoemulsion phase and also the type of membrane support. Under given experimental conditions, i.e., [Cr(VI)]0 ) 0.01 g/L and [HCl]0 ) 0.01 M in the feed phase and organic solution of 10% v/v CYPHOS IL101 in cumene, extractions exceeding 95% are obtained, and it is possible to strip using 1 M NaoH solution (also with recoveries in the 60% range). The performance of the system is also compared against other membrane operational configurations.
Introduction Because of the carcinogenic effects of Cr(VI) to humans, its removal from effluents is a primary target in many countries. Several technologies can be used for the effective Cr(VI) separation from liquid effluents, and among them liquid membranes (LMs) are considered very effective at reaching targeted values with respect to the removal of a given solute from a given liquid effluent. On the other hand, ionic liquids (ILs) as “green solvents” are a group of organic salts that exist as liquids at temperatures below 100 °C. Having specific features, they have been proposed for several applications in a number of fields as well as for separation processes of metals and other solutes. Some applications of these ILs, or even the so-called taskspecific ionic liquids (TSILs) in the separation of metals and other solutes appear regularly in the literature (1-16). One of these ILs available at industrial scale is CYPHOS IL101 (a phosphonium salt derivative), which had been used in separation processes of several metals (17-21). However and apparently, no data is available in the literature about the use of this ionic liquid in the removal of Cr(VI) from liquid effluents or even its use as a carrier in LMs technologies. Our group is carrying out a comprehensive investigation program for chromium(VI) removal from various aqueous * Corresponding author phone: (+34)915538900; fax: (+34)915347425; e-mail:
[email protected]. 7504
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 44, NO. 19, 2010
media using different LMs technologies and approaches (22-25), and in the present work, we presented data for Cr(VI) extraction from aqueous acidic solutions using CYPHOS IL101 in cumene as carrier in the pseudoemulsion membrane strip dispersion (PEMSD) technology. The investigation includes the effect of various hydrodynamic and chemical parameters, which should influence the extraction and stripping process.
Experimental Section A stock solution of Cr(VI) was prepared from K2Cr2O7 AR grade (Merck). CYPHOS IL101 [active substance is a phosphonium salt: (trihexyl-tetradecyl) phosphonium chloride (R3′R′′P+Cl-, from here simplified as R4P+Cl-)] was kindly supplied by CYTEC, Canada; the organic diluent used in the transport studies was cumene AR grade (Fluka). Both CYPHOS IL101 and cumene were used as received. All other chemicals used in the investigation were of AR grade. The membrane GVHP04700 used in most of the experimentation was manufactured by Millipore, Ireland; this and the other membrane supports (also from Millipore) used in this work have different characteristics. The characteristics of the cell used in the present investigation were similar to those described in a previous work (28). The feed and pseudoemulsion phases were mechanically stirred at 1000 and 900 rpm, respectively, at 20 ( 1 °C. Once the membrane support was in the cell, the feed phase (200 mL) and organic (100 mL) and stripping (100 mL) solutions were placed in their corresponding chambers, and the operation begins. From the initial moment of mixing, an organic/stripping solution pseudoemulsion was formed. If adequate stirring speeds in the feed and in the pseudoemulsion phases are provided, the membrane stabilizes similarly to a conventional flat-sheet supported liquid membrane operation, i.e., the organic phase wets and it is retained into the micropores of the hydrophobic support by capillarity. Also, the characteristics of the pseudoemulsion should be such that it should have clear and fast phase separation (organic and strip solutions) when mixing is stopped. The recovery of chromium from pseudoemulsion can be accomplished (pseudoemulsion immediately breaks down after the stirring of the phases stopped), and organic and stripping phases are completely separated after 1 min. Thus, the pseudoemulsion containing chamber somewhat acts as a mixer-settler of the conventional liquid-liquid extraction operation. The experimental installation for the PEMSD process resembled that of a solid-supported liquid membrane. Small aliquots of the feed and stripping solutions were taken at selected times for the analysis of chromium concentration by standard AAS (Perkin-Elmer 1100B spectrophotometer, England), and the overall mass transfer coefficient K (reproducible within (3% was computed using the next relationship (29, 30), in which K is time-independent ln
[Cr]t A×K )×t [Cr]0 VF
(1)
In the pseudoemulsion membrane organic dispersion (PEMOD) configuration, the operational characteristics are similar to above, except that the organic phase is stirred and dispersed in the strip phase. In nondispersive extraction (NDSX), no pseudoemulsion phase is formed because one of the cell chambers contained the feed solution and the other contained the organic solution (thus, a second cell is needed in order to carry out the strip process, see below). The supported liquid membrane (SLM) operation is also a 10.1021/es101302b
2010 American Chemical Society
Published on Web 08/30/2010
TABLE 2. Effect of Stripping Solution Composition on the Overall Mass Transfer Coefficient Value and Chromium Recovery in the Stripping Solutiona strip solution
FIGURE 1. Schematic concentration profile for PEMSD operation. L ) carrier. Counter transport of Cl- and OH- ions to the feed phase act as the driving force for Cr(VI) transport.
TABLE 1. Effect of Stirring Speed on the Overall Mass Transfer Coefficient Valuea 400 rpm K (cm/s)
4.6 × 10
-3
800 rpm 5.5 × 10
-3
1200 rpm
10 g/L hydrazine sulfate and 0.01 M HCl 20 g/L hydrazine sulfate and 0.01 M HCl 10 g/L hydrazine sulfate and 1 M HCl 1 M NaOH 1 M LiCl 2 M LiCl
K (cm/s)
% chromium recovery
5.5 × 10-3
5.2
-3
5.0
10-3 10-3 10-3 0-3
5.7 35.4 19.0 14.7
5.5 × 10 5.4 5.5 5.3 5.2
× × × ×
a Feed phase: 0.01 g/L Cr(VI) and 0.01 M HCl. Organic phase: 5% v/v CYPHOS IL101 in cumene. Membrane support: GVHP04700.
5.5 × 10-3
a
Feed phase: 0.01 g/L Cr(VI) and 0.01 M HCl. Organic phase: 5% v/v CYPHOS IL101 in cumene. Stripping solution: 1 M NaOH. Membrane support: GVHP04700.
nonpseudoemulsion forming phase, in which one cell chamber contained the feed solution and the other contained the strip solution, whereas the organic solution is retained by capillarity into the pores of the solid support (if hydrophobic) separating both aqueous solutions.
Results and Discussion The chemistry of the extraction of chromium(VI) from acidic aqueous solutions by CYPHOS IL101, though not yet described in the literature, can be estimated using the speciation for Cr(VI) derived from calculations using the MEDUSA program (31). It can be concluded that at low and medium Cr(VI) and HCl concentrations in the feed solution, HCrO4- is the predominant species, whereas Cr2O72- species becomes more important as the Cr(VI) concentration in the aqueous solution is increased. Regardless of the initial concentration of Cr(VI) at high HCl concentrations, i.e., 1M in the feed phase, CrO3Clis the predominant species. Thus, on the basis of the above description and the anionexchange properties of CYPHOS IL101, the following three extraction reactions must be considered when chromium(VI) is extracted by CYPHOS IL101 HCrO4-aq + R4P+Clorg S R4P+HCrO4-org + Claq
(2)
Cr2O72+ 2R4P+Clorg S (R4P+)2Cr2O72+ 2Claq aq org
(3)
CrO3Claq
+ R4P
+
Clorg
S R4P
+
CrO3Clorg
+
Claq
The agitation of the pseudoemulsion phase was kept constant at 900 rpm. Constant overall mass transfer coefficient values (Table 1, K ) 5.5 × 10-3 cm/s) for stirring speeds in the range 800-1200 rpm were obtained. Thus, the thickness of the aqueous diffusion layer and the aqueous resistance to mass transfer were minimized, and the diffusion contribution of the aqueous species to mass transfer process is assumed to be constant. In this condition
Klim )
where the subscripts aq and org represent the aqueous feed and organic solutions of the present membrane system, respectively. Figure 1 shows a possible transport scheme for chromium(VI) using this membrane technology. Such a process is called coupled facilitated counter-transport, where the counterion Cl- (contained in the extractant molecule) is released into the feed solution when the various Cr(VI) species are bonded to the cation side of the ionic liquid molecule. Influence of the Stirring Speed of the Feed Solution. Previous experiments were carried out to establish adequate hydrodynamic conditions, using the phases and support indicated in Table 1. The transport of the metal was studied as a function of the stirring speed on the feed solution side.
(5)
and assuming a value of Daq in the 10-5 cm2/s range (24) and Klim ) 5.5 × 10-3 cm/s, the value of daq is calculated as 1.8 × 10-3 cm; this value being the minimum thickness of the aqueous diffusion layer within the present experimental conditions. Influence of the Stripping Solution Composition. Different stripping solutions were investigated in order to evaluate their performance on the recovery of chromium from loaded organic solutions. Table 2 shows the experimental conditions used in this set of experiments, together with the results obtained from it. As seen in Table 2, the change in the strip solution composition has a negligible effect on chromium transport because the values of the overall mass transfer coefficient remained almost constant. On the other hand, results on the percentage of chromium recovered in the strip solution, calculated as
% Stripping ) (4)
Daq daq
[Cr]S × 100 VF ([Cr]0-[Cr]t) VS
(6)
showed that only the NaOH solution is moderately effective as a strip agent for chromium. Moreover, because this stripping difference did not affect the chromium transport, these results suggest that the interfacial mass transfer resistance due to the extraction reaction may be dominant. Thus, considering the extraction reactions shown in eqs 2-4, the next reactions can be derived to explain the strip of chromium(VI) from loaded organic solutions S CrO42+ R4P+OHorg +H2O R4P+HCrO4-org + 2OHaq aq
(7) VOL. 44, NO. 19, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
7505
+ H2O + 2R4P+OHorg + 4OHaq S 2CrO42(R4P+)2Cr2O72org aq (8)
TABLE 5. Influence of Initial HCl Concentration on the Overall Mass Transfer Coefficient Valuea
+ + 3OHaq S CrO42+ R4P+OHorg + Claq R4P+CrO3Clorg aq H2O (9)
and/or:
[HCl]0 (g/L)
K (cm/s)
0.01 0.1 1
3.8 × 10-3 3.1 × 10-3 6.6 × 10-4
a
R4P
+
CrO3Clorg
+
2OHaq
S
CrO42-aq
+ R4P
+
+H2O Clorg
(10) where the subscripts org and aq refer to the organic and stripping solution, respectively. It is apparent, that the R4P+OH- can acts as an anion exchanger in the same manner (eqs 2-4) as the R4P+Cl- species; similar behavior had been shown in the literature using other extractants and/or strip solutions (11, 21, 32, 33). Taking into account the above description, we released the counterion OH- (also contained in the extractant molecule as a consequence of the strip reaction) into the feed solution in the complexation of Cr(VI) species with the cationic moiety of the ionic liquid. Thus, in the present system, both Cl- and OH- ions, released into the feed solution as a consequence of the counter-transport process, are considered as the driving force for Cr(VI) transport. Influence of the Volume Ratio of Organic and Stripping Solutions. The influence of the variation in the volume ratio of organic and stripping solutions in the pseudoemulsion phase (total volume 200 mL) on transport of Cr(VI) was investigated. The results of this investigation, together with the experimental conditions used, are shown in Table 3. In terms of metal transport, it is shown that the most effective volume ratio is 1:1, whereas in terms of the percentage of chromium stripped the best results are obtained when a 3:1 (organic:strip solutions) ratio was used in the pseudoemulsion phase. Influence of Initial Metal Concentration in the Feed Solution. Table 4 shows, together with the experimental conditions, the variation of the chromium overall mass transfer coefficient at various metal concentrations ranging
TABLE 3. Influence of the Organic/Strip Volume Phase Ratio in the Pseudo-Emulsion Phase on the Overall Mass Transfer Coefficient Value and in the Percentage of Chromium Recovery in the Strip Solutiona organic/strip phases volume ratio
K (cm/s)
% chromium recoveryb
3:1 1:1 1:3
3.4 × 10-3 5.5 × 10-3 4.7 × 10-3
58.3 35.4 31.1
a Feed phase: 0.01 g/L Cr(VI) and 0.01 M HCl. Organic phase: 5% v/v CYPHOS IL101 in cumene. Stripping solution: 1 M NaOH. Membrane support: GVHP04700. b After 3 h.
TABLE 4. Influence of Initial Chromium(VI) Concentration on the Overall Mass Transfer Coefficient Valuea [Cr(VI)]0 (g/L)
K (cm/s)
0.01 0.1 1
3.8 × 10-3 3.8 × 10-3 8.5 × 10-4
a Feed phase: Cr(VI) and 0.1 M HCl. Organic phase: 5% v/V CYPHOS IL101 in cumene. Stripping solution: 1 M NaOH. Membrane support: GVHP04700.
7506
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 44, NO. 19, 2010
Feed phase: 0.01 g/L Cr(VI) and HCl. Organic phase: 1% v/v CYPHOS IL101 in cumene. Stripping solution: 1 M NaOH. Membrane support: GVHP04700.
TABLE 6. Effect of Initial Carrier Concentration on the Overall Mass Transfer Coefficient Valuea [CYPHOS IL101]0 (% v/v)
K (cm/s)
1 5 10
8.2 × 10-4 3.8 × 10-3 7.9 × 10-3
a Feed phase: 0.1 g/L Cr(VI) and 0.1 M HCl. Organic phase: CYPHOS IL101 in cumene. Stripping phase: 1 M NaOH. Membrane support: GVHP04700.
from 0.01 to 1 g/L in the feed phase. The lowest K value obtained for the highest concentration of Cr(VI) is 1 g/L. This should be because the organic solution filling the membrane micropores becomes saturated with extracted metal complexes increasing the chromium concentration in the feed phase. In this condition, the extracted complexes diffused slowly into the bulk of organic solution, resulting in a decrease in the mass transfer in the organic phase. Influence of HCl Concentration in the Feed Solution. The variation in Cr(VI) transport at the conditions shown in Table 5 was also investigated. Results are shown in this same table in which a decrease in chromium transport occurs as the initial HCl concentration in the feed phase increases. This result can be tentatively attributable to the various extractions reactions (eqs 2-4) involved in the extraction of Cr(VI) by CYPHOS IL101. Influence of CYPHOS IL101 Concentration in the Organic Solution. The influence of carrier concentration on Cr(VI) transport was also studied. Table 6 shows the overall mass transfer coefficient values within the present experimental conditions. As seen in Table 6, the transport of chromium increases with an increase in carrier concentration in the organic phase; thus, it can be considered that the transport process is controlled by membrane diffusion. Assuming that the carrier concentration in the membrane is constant, the next equation can be used to determine the apparent diffusion coefficient of chromium (34) Dorg,a )
J·dorg [carrier]
(11)
where J is defined as J ) K × [Cr]0
(12)
The average value of Dorg,a was estimated as 1.1 × 10-6 cm2/s, taking the GVHP04700 support of thickness (dorg) 12.5 × 10-3 cm and using CYPHOS IL101 concentrations from 1 to 10% v/v in cumene. Estimation of the Local Resistance Contribution to the Overall Transport of Cr(VI). The transport of chromium(VI) by CYPHOS IL101 involves various sequential steps and assumptions which may be similar to those described in the literature for other systems (35-37). On the basis of these,
TABLE 7. Contribution of the Fractional Mass Transfer Resistances to the Overall Resistance Under Various Experimental Conditions
TABLE 8. Chromium(VI) Transport Using Various Membrane Supporta support
condition
R (s/cm)
RF(s/cm)
RF0
Rm0
0.01-1 g/L [Cr]a 0.01-1 M [HCl]a 1-10% v/v [carrier]a
263-1176 263-1515 1219-126
181 181 181
69-0 69-0 0
31-100 31-100 100
a
Other experimental conditions as in Tables 4, 5, and 6, respectively.
a final expression for the overall mass transfer coefficient can be defined by the present system as ∆m 1 ) ∆F + K C
+
-
C ) Kext × [R4P Cl ]org ×
-1 [Cl-]aq
(14)
for eq 2, being similarly defined for eqs 3 and 4. In the case that the three extraction reactions contributed to the transport of the metal, the three C values may appear in the denominator of eq 13. From eq 13, the overall resistance is R ) RF+Rm
(15)
thus being the sum of the local resistances due to the feed phase and the membrane. Table 7 resumed the values of the overall resistances obtained from the present work under various experimental conditions, and the feed resistance experimentally obtained from this investigation. Furthermore, the fractional resistance (RF0 and Rm0) contributions to the overall process could be estimated as RF0 )
Durapore GVHP04700 Durapore HVHP04700 Fluoropore FGLP04700
RF × 100 R
(16)
KN (cm/s)
-6
5.5 × 10-6 5.6 × 10-6 5.7 × 10-6
5.5 × 10 5.6 × 10-6 3.4 × 10-6
a
Feed phase: 0.01 g/L Cr(VI) and 0.01 M HCl. Organic phase: 5% v/v CYPHOS IL101 in cumene. Stripping solution: 1 M NaOH.
TABLE 9. Chromium(VI) Transport Using Various Membrane Operation Mode and CYPHOS IL101 as Carriera operation mode
(13)
where C is a numerical value defined for each extraction equilibrium involved in the transport of the metal; thus, in the present case
K (cm/s)
NDSX PEMOD PEMSD FSSLM
K (cm/s) 4.9 5.7 5.5 2.7
× × × ×
10-3 10-3 10-3 10-3
a Feed phase: 0.01 g/L Cr(VI) and 0.01 M HCl. Organic phase: 5% v/v CYPHOS IL101 in cumene. Stripping phase: 1 M NaOH (except in NDSX operation). Membrane support: GVHP04700.
and nearly the same overall mass transfer coefficient values were obtained for the three supports. Chromium(VI) Transport Using Various Membrane Operational Modes. The transport of chromium(VI), using the experimental conditions given in Table 9, had been investigated in various operational modes of the membrane contactor. These different operational modes were also summarized in Table 9, together with the results in the form of K values, derived from this investigation. It is shown that best results are obtained when PEMSD and PEMOD operations are used. It should be mentioned that NDSX technology had been investigated using only a single cell for extraction, very probably the performance of the technology can be improve if an integrated membrane process, with two cells contactors (extraction and stripping performed together but separately in each cell), is used.
Acknowledgments
and
We thank the CSIC (Spain) for support. 0 ) 100 - RF0 Rm
(17)
From results showed in Table 7, it can be inferred that the rate-controlling step is due to the feed phase at low metal and hydrochloric acid concentrations in the aqueous feed solution, whereas resistance due to the membrane is predominant at higher metal and acid concentrations in the feed phase and at all the carrier concentrations investigated in the present work. Influence of the Membrane (Support) Characteristics. Three membrane supports with different characteristics were investigated in the experimental conditions shown in Table 8. In this same table, the obtained overall mass transfer coefficient values are given; it can be seen that best values are obtained when GVHP04700 and HVHP04700 supports were used. However, to correct the fact that the diffusion path is greater than the distance perpendicular to the interface, values of the overall mass transfer coefficient were normalized (KN) to the thickness, porosity, and tortuosity of the GVHP04700 support using the next equation (26, 38):
(
KN ) K
dorg × τ εGVHP ε τGVHP × dorg,GVHP
)
(18)
Appendix NOMENCLATURE A [Cr]t [Cr]0 [Cr]S Daq daq Dorg,a dorg J K Kext Klim KN R RF
membrane effective area chromium concentration in the feed phase at an elapsed time chromium concentration in the feed phase at time zero chromium concentration in the strip solution diffusivity of chromium species in the feed phase thickness of the feed phase diffusion layer apparent diffusion coefficient in the organic solution membrane thickness flux overall mass transfer coefficient extraction equilibrium constant limiting overall mass transfer coefficient normalized overall mass transfer coefficient overall resistance resistance due to the feed solution
VOL. 44, NO. 19, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
7507
RF0 Rm Rm0 VF VS t ∆F ) daq/Daq ∆m ) dorg/Dorg ε τ
fractional resistance due to the feed solution resistance due to the membrane fractional resistance due to the membrane volume of feed solution volume of stripping solution time transport resistance due to the feed solution transport resistance due to the membrane membrane thickness membrane tortuosity
Supporting Information Available Tables for the characteristics of the various supports used and Cr(VI) speciation and a representation of the PEMSD experimental device. This information is available free of charge via the Internet at http://pubs.acs.org/.
Literature Cited (1) Visser, A. E.; Swatloski, R. P.; Reichert, W. M.; Mayton, R.; Scheff, S.; Wierzbick, A.; Davis Jr, J. H.; Rogers, R. D. Task-specific ionic liquids incorporating novel cations for the coordination and extraction of Hg2+ and Cd2+: Synthesis, characterization, and extraction studies. Environ. Sci. Technol. 2002, 36, 2523–2529. (2) Zhao, H.; Xia, S.; Ma, P. Use of ionic liquid as “green” solvents for extractions. J. Chem. Technol. Biotechnol. 2005, 80, 1089– 1096. (3) Lee, S. Functionalized imidazolium salts for task-specific ionic liquids and their applications. Chem. Commun. 2006, 1049– 1068. (4) Han, X.; Armstrong, D. W. Ionic liquids in separations. Acc. Chem. Res. 2007, 40, 1079–1086. (5) Papaiconomou, N.; Lee, J.-M.; Salminen, J.; von Stosch, M.; Prausnitz, J. M. Selective extraction of copper, mercury, silver, and palladium ions from water using hydrophobic ionic liquids. Ind. Eng. Chem. Res. 2008, 47, 5080–5086. (6) Kogelnig, D.; Stojanovic, A.; Galanski, M.; Groessl, M.; Jirsa, F.; Krachler, R.; Keppler, B. K. Greener synthesis of a new ammonium ionic liquids and their potential as extracting agents. Tetrahedron Lett. 2008, 49, 2782–2785. (7) Sun, X.; Peng, B.; Ji, Y.; Chan, J.; Li, D. The solid-liquid extraction of yttrium from rare earths by solvent (ionic liquid) impregnated resin coupled with complexing method. Sep. Purif. Technol. 2008, 63, 61–68. (8) Ajioka, T.; Oshima, S.; Hirayama, N. Use of 8-sulfonamidoquinoline derivatives as chelate extraction reagents in ionic liquid extraction system. Talanta 2008, 63, 61–68. (9) Huang, J.-F.; Luo, H.; Liang, C.; Jiang, D.; Dai, S. Advanced liquid membranes based on novel ionic liquids for selective separation of olefin/paraffin via olefin-facilitated transport. Ind. Eng. Chem. Res. 2008, 47, 881–888. (10) Srncik, M.; Kogelnig, D.; Stojanovic, A.; Ko¨rner, W.; Krachler, R.; Wallner, G. Uranium extraction from aqueous solutions by ionic liquids. Appl. Radiat. Isot. 2009, 67, 2146–2149. (11) Alguacil, F. J.; Alonso, M.; Lopez, F. A.; Lopez-Delgado, A. Application of pseudo-emulsion based hollow fiber strip dispersion (PEHFSD) for recovery Cr(III) from alkaline solutions. Sep. Purif. Technol. 2009, 66, 586–590. (12) Lee, J. S.; Luo, H.; Baker, G. A.; Dai, S. Cation cross-linked ionic liquids as anion-exchange materials. Chem. Mater. 2009, 21, 4756–4758. (13) Mallah, M. H.; Shemirani, F.; Maragheh, M. G. Ionic liquids for simultaneous preconcentration of some lanthanoids using dispersive liquid-liquid microextraction technique in uranium dioxide powder. Environ. Sci. Technol. 2009, 43, 1947–1951. (14) Egorov, V. M.; Djigailo, D. I.; Momotenko, D. S.; Chernyshov, D. V.; Torocheshnikova, I. I.; Smirnova, S. V.; Pletnev, I. V. Taskspecific ionic liquid trioctylmethylammonium salicylate as extraction solvent for transition metals. Talanta 2010, 3, 1177– 1182. (15) Alguacil, F. J.; Alonso, M.; Lopez, F. A.; Lopez-Delgado, A.; Padilla, I.; Tayibi, H. Pseudo-emulsion based hollow fiber with strip dispersion pertraction of iron (III) using (PJMTH+)2 (SO42-) ionic liquid as carrier. Chem. Eng. Journal 2010, 157, 366–372. (16) de los Rios, A. P.; Hernandez-Fernandez, F. J.; Lozano, L. J.; Sanchez, S.; Moreno, J. I.; Godinez, C. Removal of metal ions from aqueous solutions by extraction with ionic liquids. J. Chem. Eng. Data 2010, 55, 605–608.
7508
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 44, NO. 19, 2010
(17) Vincent, T.; Parodi, A.; Guibal, E. Pt recovery using Cyphos IL101 immobilized in biopolymer capsules. Sep. Purif. Technol. 2008, 62, 470–479. (18) Campos, K.; Domingo, R.; Vincent, T.; Ruiz, M.; Sastre, A. M.; Guibal, E. Bismuth recovery from acidic solutions using Cyphos IL-101 immobilized in a composite biopolymer matrix. Water Res. 2008, 42, 4019–4031. (19) Vincent, T.; Parodi, A.; Guibal, E. Immobilization of Cyphos IL-101 in biopolymer capsules for the synthesis of Pd sorbents. React. Funct. Polym. 2008, 68, 1159–1169. (20) Campos, K.; Vincent, T.; Bunio, P.; Trochimczuk, A.; Guibal, E. Gold recovery from HCl solutions using Cyphos IL-101 (a quaternary phosphonium ionic liquid) immobilized in biopolymer capsules. Solvent Extr. Ion Exch. 2008, 26, 570–601. (21) 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. (22) Alguacil, F. J.; Coedo, A. G.; Dorado, M. T.; Sastre, A. M. Uphill permeation of chromium (VI) using Cyanex 921 as ionophore across an immobilized liquid membrane. Hydrometallurgy 2001, 61, 13–19. (23) Alguacil, F. J.; Alonso, M. Chromium (VI) renoval through facilitated transport using Cyanex 923 as carrier and reducing stripping with hydrazine sulfate. Environ. Sci. Technol. 2003, 37, 1043–1047. (24) Alguacil, F. J.; Alonso, M.; Lopez, F. A.; Lopez-Delgado, A. Uphill permeation of Cr(VI) using Hostarex A327 as ionophore by membrane-solvent extraction processing. Chemosphere 2008, 72, 684–689. (25) Alguacil, F. J.; Alonso, M.; Lopez, F. A.; Lopez-Delgado, A.; Padilla, I. Dispersion-free solvent extraction of Cr(VI) from acidic solutions using hollow fiber contactor. Environ. Sci. Technol. 2009, 43, 7718–7722. (26) Stolwijk, T. B.; Sudho¨lter, E. J. R.; Reindhoudt, D. N. Crown ether transport: A kinetic study of potassium perchlorate transport through a supported liquid membrane containing dibenzo-18-crown-6. J. Am. Chem. Soc. 1987, 109, 7042–7047. (27) Sastre, A.; Madi, A.; Cortinal, J. L.; Miralles, N. Modelling of mass transfer in facilitated supported liquid membrane transport of gold (III) using phospholene derivatives as carriers. J. Membr. Sci. 1998, 139, 57–65. (28) Sastre, A. M.; Alguacil, F. J.; Alonso, M.; Lopez, F. A.; LopezDelgado, A. On cadmium (II) membrane-based extraction using Cyanex 923 as carrier. Solvent Extr. Ion Exch. 2008, 26, 197–207. (29) Winston Ho, W. S.; Wang, B. Strontium removal by new alkylphenylphosphonic acids in SLMs with strip dispersion. Ind. Eng. Chem. Res. 2002, 41, 381–388. (30) Bringas, E.; San Roman, M. F.; Irabien, J. A.; Ortiz, I. An overview of the mathematical modelling of liquid membrane separation processes in hollow fiber contactors. J. Chem. Technol. Biotechnol. 2009, 84, 1583–1614. (31) Puigdomenech, I. MEDUSA (Make Equilibrium Diagrans Using Sophisticated Algorithms), version 3.1; Royal Institute of Technology: Stockholm, Sweden, 2002; http://www.kemi.kth.se/ medusa/. (32) Galan, B.; Castan ˜ eda, D.; Ortiz, I. Removal and recovery of Cr(VI) from polluted ground waters: A comparative study of ionexchange technologies. Water Res. 2005, 39, 4317–4324. (33) Wionczyk, B.; Apostoluk, W.; Charewicz, W. A. Solvent extraction of chromium (III) from spent tanning liquors with Aliquat 336. Hydrometallurgy 2006, 82, 83–92. (34) Alguacil, F. J.; Alonso, M.; Sastre, A. M. Copper separation from nitrate/nitric acid media using Acorga M5640 extractant. Part II. Supported liquid membrane study. Chem. Eng. J. 2002, 85, 265–272. (35) Kumar, A.; Sastre, A. M. Hollow fiber supported liquid membrane for the separation/concentration of gold(I) from aqueous cyanide media: Modeling and mass transfer evaluation. Ind. Eng. Chem. Res. 2000, 39, 146–154. (36) Alonso, M.; Lopez.Delgado, A.; Sastre, A. M.; Alguacil, F. J. Kinetic modelling of the facilitated transport of cadmium (II) using Cyanex 923 as ionophore. Chem. Eng. J. 2006, 118, 213–219. (37) Pei, L.; Yao, B.; Zhang, C. Transport of Tm(III) through dispersion supported liquid membrane containing PC-88A in kerosene as the carrier. Sep. Purif. Technol. 2009, 65, 220–227. (38) Babcock, W. C.; Baker, R. W.; Lapochelle, E. D.; Smith, K. L. Coupled transport membranes. 2. The mechanism of uranium transport with tertiary amines. J. Membr. Sci. 1980, 7, 71–87.
ES101302B
