1
2
3
4
5
6
7
8
9
10
Centro Nacional de Investigaciones Metalurgicas (CSIC), Avda. Gregorio del Amo
8, Ciudad Universitaria, 28040 Madrid, Spain. *E-mail: fjalgua@cenim.csic.es
11
12
13
Abstract
The transport of chromium by the emulsion pertraction technology (EPERT) using
14
15
Hostarex A327 (tertiary amine) as a carrier has been investigated. The permeation of the metal is studied as a function of various experimental variables: hydrodynamic
16
17
18
19
20 conditions, concentration of Cr(VI) and HCl in the source phase, carrier concentration and diluent in the organic phase, strippant concentration in the stripping phase and support characteristics of the membrane. The mass transfer coefficient and the thickness of the aqueous source boundary layer were estimated from the experimental data. Furthermore, the selectivity of the Hostarex A327-bases
21
22
23
EPERT towards different metal ions and the behaviour of the system against other carriers are presented.

2
1 Keywords: Cr(VI) transport; Emulsion pertraction technology; Hostarex A327
2
3
4 1. Introduction
5
6 Cr(VI) is recognized to be one of the most toxic elements for living organisms due to
7 its effect in the development of cancer and non-cancer diseases (Casadevall and
8 Kortenkamp, 2002). Despite its toxicity, this element is used widely in different
9 industrial processes, thus, its recovery from the different effluents is a primary target
10 before their discharge to the environment.
11 Several technologies have been developed to remove and/or recover Cr(VI) from the
12 various effluents generated from these industrial processes (Beszedits, 1988; Ruffo et
13 al., 1996). In the case of liquid effluents or wastewaters, liquid membranes technologies
14 could be competitive when the targeted species is present at low concentrations in the
15 aqueous solution.
16 There are two types of liquid membranes: (1) non-supported liquid membranes,
17 category which includes bulk liquid membranes and emulsion liquid membranes, and
18 (2) supported liquid membranes (SLMs); being the characteristics of these various types
19 of membranes described in the literature (Alguacil and Villegas, 2002). Also the use of
20 these liquid membranes for the removal of metallic and non-metallic species from
21 aqueous solutions, wastewaters, fermentation broths, etc. (Alguacil and Alonso, 2005;
22 Alonso et al., 2006; Nghiem et al., 2006), has long been pursued by the scientific and
23 industrial community.

3
1 Though these processes are normally effective, their use have been hampered by their
2 relatively instability, however, the introduction of the SLMs with strip dispersion
3 apparently have solved the stability problem. In this operation mode, the aqueous source
4 solution, containing the species to be extracted is into contact with one side of the
5 support, whereas the aqueous strip solution is dispersed in an organic solution,
6 containing the corresponding carrier and diluent, in a mixer and the emulsion formed is
7 put into contact with the other side of the microporous support. The continuous organic
8 phase of the emulsion readily wets the pores of the hydrophobic support and a stable
9 liquid membrane supported in the pores of the microporous support, similarly to that
10 found in conventional SLMs, is formed. Thus, this type of membrane can be considered
11 as a conventional SLM with a constant supply of the organic solution into the pores.
12 After the operation is finished, the mixer for the strip dispersion is switch off, and the
13 dispersion is separated into the two phases, the organic solution and the strip solution,
14 which now contained the species. Thus, this was extracted from the source solution,
15 concentrated and separated from undesiderable species. This strip solution can be now
16 processed to obtain the final product of the corresponding process.
17 Before scaling-up the technology in the form of other SLMs configuration, i.e. hollow
18 fiber modules, which is more adequate for industrial use since it provides higher surface
19 area to volume ratio, first laboratory studies are needed in order to design a more
20 efficient recovery process. In this role, it is recognized that flat-sheet SLMs
21 configuration are useful for previous laboratory data.
22 The transport of Cr(VI) from different aqueous solutions using these liquid
23 membranes technologies is reported in the literature (Alguacil et al., 2004; Eliceche et
24 al., 2005; Galan et al., 2005; Kozlowski and Walkowiak, 2005; Bringas et al., 2006a;

4
1 Bringas et al., 2006b; Chiha et al., 2006; Galan et al., 2006; Fresnedo San Roman et al.,
2 2007).
3 In the present work, results obtained for the transport of Cr(VI) using the tertiary
4 amine Hostarex A327 as carrier, are presented. This investigation deals the possibilities
5 of using the Emulsion Pertraction Technology (EPERT) in a conventional SLM cell to
6 obtain laboratory data prior to the scaling-up of the system to a continuous operation
7 mode using a hollow fiber module. Several variables, which could affect the permeation
8 process: stirring speed of the source and stripping phases, metal and carrier
9 concentrations, diluent of the organic phase, etc., are investigated. The selectivity of the
10 system against other metallic species and the behaviour of Hostarex A327 vs. other
11 carriers are also reported.
12
13 2. Experimental
14
15 2.1. Materials
16
17 The tertiary amine Hostarex A327, kindly donated by Hoechst through its Spanish
18 branch, was used as received. The purity was greater than 95% (experimentally
19 determined by titration with standard HCl solutions using bromothymol blue as
20 indicator). The organic phase was prepared by diluting a measured volume of the amine
21 or the corresponding extractant with reagent grade cumene. Extractants, TBP (tri-n-
22 butylphosphate, Fluka), Cyanex 923 (Cytec), Primene JMT (Rohm and Haas),
23 Amberlite LA2 (Fluka) and Aliquat 366 (Fluka), were also used without further
24 purification. The analytical grade diluents xylene, toluene, cumene and n-decane

5
1 (Fluka) were used as such. Stock Cr(VI) solutions were prepared by dissolving K
2
Cr
2
O
7
2 (Merck) or the corresponding metallic salt in distilled water. All other chemicals were
3 of analytical reagent grade.
4
5 2.2. EPERT preparation and measurements
6
7 The characteristics of the cell used in the present investigation were similar to those
8 described in a previous work (Alguacil and Alonso, 2005b). The source and the
9
10 organic/stripping phases emulsion were mechanically stirred at 800 and 1100 rpm, respectively, at 20±1 ºC. Once the membrane support was placed in the cell, the source
11 solution (200 mL) and the organic (100 mL) and stripping (100 mL) phases were placed
12 in their corresponding chambers and the operation begins. From the initial moment of
13 mixing, an organic/stripping phases emulsion was formed, and providing adequate
14 stirring speeds in the source phase and in the emulsion phase, the membrane stabilizes
15 similarly to conventional flat-sheet supported liquid membrane operation, i.e. the
16 organic phase wets and it is retained into the micropores of the hydrophobic support by
17 capillarity.
18 Membrane permeabilities were determined by monitoring metal concentration by
19 AAS in the source (or the stripping) phase as a function of time. The Cr concentration in
20 the source phase was found to be reproducible within ±3%. The permeation coefficient
21 (P) was computed using:
22
23 ln


Cr
Cr
 
 

 t
0
 
A
V source
Pt (1)
24

6
1 where A is the effective membrane area (11.3 cm
2
), V source
is the volume of the source
2 phase, [Cr(VI)] t
and [Cr(VI)]
0
are the concentration in the source phase at elapsed time t
3 and time zero, respectively. For the calculations of the chromium metal-accompanying
4 permeabilities, the same Eq. 1 was used.
5 The percentage of Cr recovered in the stripping phase was determined using:
6
7 % R


Cr
 s
V source
(
V stripping
)(

Cr

0


Cr
   t
)

100 (2)
8
9 by analyzing the Cr concentration in the stripping solution [Cr(VI)] s
, after the operation
10 was stopped (typically 3 h) and the organic and the stripping phases were separated.
11
12 3. Results and discussión
13
14 The extraction of Cr(VI) by the tertiary amine can be represented by the next set of
15 equations:
16 H
 aq

Cl
 aq

R
3
N org

R
3
NH

Cl
 org
(3)
17
18 HCrO

4 aq

R
3
NH

Cl
 org

R
3
NH

HCrO

4 org

Cl
 aq
(4)
19
20 Accordingly with the above, the amine first reacts with hydrochloric acid to form the
21 amine salt (Eq. 3) which then reacts with the Cr species to form the corresponding
22 metal-amine complex in the organic phase, releasing chloride ions in the aqueous

7
1 solution. Thus, the proper metal- extraction reaction (Eq. 4) can be related to an anion
2 exchange process. However, the next reaction can be also responsible for the extraction
3 of Cr(VI):
4
5 HCrO

4 aq

H
 aq

R
3
N org

R
3
NH

HCrO

4 org
(5)
6
7 In either case, stripping using NaOH solution takes place as follows:
8
9 2 NaOH aq

R
3
NH

HCrO

4 org

R
3
N org

Na
2
CrO
4 aq

2 H
2
O aq
(6)
10
11 Taking into account the reactions shown in Eqs. 5 and 6, the facilitated transport
12 mechanism for the Cr(VI) transfer across the membrane is shown schematically in Fig.
13 1. The transport is related to a co-transport mechanism.
14
15 3.1. Influence of the stirring speed of the source solution
16
17 Previous experiments were carried out to establish adequate hydrodynamic conditions.
18 The permeability of the membrane was studied as a function of the stirring speed on the
19 source solution side. The agitation of the organic/stirring phases (O/S) emulsion was
20 kept constant at 1600 rpm. Constant permeability for stirring speeds higher than 500
21 rpm was obtained (Table 1). Consequently, the thickness of the aqueous diffusion layer
22 and the aqueous resistance to mass transfer were minimized and the diffusion
23 contribution of the aqueous species to mass transfer process is assumed to be constant.
24

8
1 3.2. Influence of the stirring speed of the O/S emulsion and concentration of the
2 stripping agent of the stripping solution
3
4 The effect of varying the stirring speed in the O/S emulsion was also investigated
5 using the same phases as described in Table 1, and maintaining a 1200 rpm constant
6 speed in the source solution. Results obtained show that the variation of the stirring
7 speed (1200-1600 rpm) in the O/S emulsion does not affect chromium permeability
8 (P average
= 3.8±0.2 cm s -1 ).
9 Different concentrations of NaOH were studied as stripping agents. The results are
10 given in Table 2, the permeability value increases with the increase of the NaOH
11 concentration in the stripping phase up to 0.1 M NaOH and then tends to level off,
12 whereas chromium recovery (%R) in the stripping phase have the same tendency as
13 above. From the above, Cr(VI) is released from the organic phase, to the stripping
14 phase and concentrated twice in this phase accordingly with the source to stripping
15 volume phases ratio used in this investigation. At the same time the carrier is
16 regenerated as in Eq. 6. As a result of the previous experiments, 0.1 M NaOH was used
17 as the stripping agent.
18
19 3.3. Influence of the HCl concentration in the source phase
20
21 In order to study the significance of the role of the HCl concentration in the source
22 phase solution during the permeation of Cr, HCl variation concentration studies in the
23 range 10 -3 -1 M were carried out, the receiving phase being 0.1 M NaOH.

9
1 As seen in Table 3, permeability of Cr(VI) increases with increasing HCl up to 10
-2
2 M, and then decreases with increasing aqueous acidity. This should be attributable to
3 the increase in the concentration of the amine chloride salt (Eq. 3), being this species
4 responsible of the extraction (transport) of Cr(VI) from the source to the organic phase
5 (Eq. 4); at higher acidities the decrease in Cr(VI) transport should be attributable to a
6 change in the extraction properties of the carrier.
7 In the absence of HCl in the source solution, Cr(VI) permeates and this is attributable
8 to that in the present condition, Cr(VI) transport responded to the mechanism shown in
9 Eq. 5.
10
11 3.4. Influence of the diluent
12
13 As seen from Fig. 2, the permeability of Cr(VI) depends on the nature of the organic
14 diluent. Removal of Cr(VI) from the source side is somewhat more effective when
15 cumene is used as the diluent for Hostarex A327. When n-decane is used as diluent for
16 the amine, the transport of Cr(VI) is less effective. With a straight chain configuration,
17 this aliphatic diluent has a relatively regular structure with strong Van der Waal´s forces
18 between the molecules, and suffers more disruption on transport of bulky complexes.
19 On the other hand, the percentage of Cr recovery in the stripping phase follows the
20 order: xylene (95%) = toluene (95%) > cumene (83%) >>> n-decane (15%).
21
22 3.5. Influence of the support characteristics on the chromium flux
23

10
1 Three solid supports, Durapore GVHP 4700, Fluoropore FGLP and Durapore HVHP
2 4700, with different characteristics (Alguacil et al., 2002), were used to study their
3 effect on Cr transport. The flux values:
4
5 J


Cr
  
TOT
P (7)
6
7 were averaged as J average
= 2.6±0.2x10
-6 mol cm
-2
s
-1
, showing no apparent effect of the
8 solid support on Cr(VI) transport. In the above series of experiments, the experimental
9 conditions used were summarized as, source phase: 0.02 g L
-1
Cr(VI) and 10
-2
M HCl,
10 membrane: Durapore GVHP 4700, organic phase: 10% v/v Hostarex A327 in cumene,
11 stripping phase: 0.1 M NaOH.
12
13 3.6. Influence of initial metal concentration
14
15 Figure 3 shows a plot of the initial Cr(VI) flux (J) vs. the concentration of chromium
16 in the source phase. In the range of metal concentrations used in the present work, the
17 initial flux is a function of the initial concentration of Cr(VI) in the source phase, thus,
18 the permeation process is controlled by diffusion of metal species.
19
20 3.7. Evaluation of limiting permeability (P lim
)
21
22 The influence of different Hostarex A327 concentrations on permeability was studied
23 in the range 2.5-40% v/v. Results obtained are shown in Fig. 4; it can be seen that at
24 higher carrier concentrations, P is independent of Hostarex A327 concentration and this

11
1 region is representative of an aqueous diffusion film-controlled permeation process.
2 This constant permeability value P lim
, known as limiting permeability, can be expressed
3 as:
4 P lim

1
 aq

D aq d aq
(8)
5
6 Assuming the value of D aq
(average aqueous diffusion coefficient of the metal-
7 containing species) as 10
-5
cm
2 s
-1
(Alguacil et al., 2000) and P lim
as 9.2x10
-3
cm s
-1
, the
8 value of the thickness of the aqueous boundary layer (d aq
) is estimated to be 1.1x10
-3
9 cm. This value is the minimum thickness of the stagnant aqueous diffusion layer in the
10 present experimental conditions.
11
12 3.8. Selective transport of Cr(VI) vs. Mn(VII), Fe(III), Cr(III), Cu(II), Zn(II), Ni(II)
13
14 Because Cr is widely used in a number of industries, the corresponding wastewaters
15 may contain a wide range of concentrations of Cr(VI) and other heavy metals, i.e.
16 coating plants (Cr(VI) 0.005-5.0 mg L -1 , iron 0.41-170 mg L -1 ), chemical milling and
17 etching (Cr(VI) 0.005-335 mg L
-1
, copper 0.21-270 mg L
-1
, zinc 0.112-200 mg L
-1
, iron
18 0.0075-260 mg L
-1
), printed board industry (Cr(VI) 0.004-3.54 mg L
-1
, copper 1.6-540
19 mg L
-1
, nickel 0.027-9 mg L
-1
, lead 0.044-10 mg L
-1
), anodizing plants (total chromium
20 0.27-80 mg L
-1
, Cr(VI) 0.005-5.0 mg L
-1
).
21 Table 4 shows results obtained in the transport of Cr(VI) when the source phase also
22 contained other accompanying metals. A highly selective transport of Cr(VI) is obtained
23 within the experiments that allow recovery of high purity Cr(VI) from the stripping
24 solution. However, Cr(VI) permeation is negatively influenced in the presence of the

12
1 accompanying elements, despite that some of the metals were not detected in the
2 receiving phase or are slightly transported. Such behaviour may be explained in various
3 ways: a negative salting-out effect, formation of metal-chlorocomplexes which also
4
5 decreases the initial acidity of the of the source phase, the transport of the companion element and also to a “crowding effect” in the source phase due to the presence of these
6 elements in it. On the other hand and under the experimental conditions used in these
7 series of tests, Cr(III) is very slightly transported (P = 3.3x10
-4
cm s
-1
)
8
9 3.9. Behaviour of the Hostarex A327 carrier system compared to other potential Cr(VI)
10 carriers
11
12 The transport of Cr(VI) was also studied using other carriers to compare with results
13 obtained using Hostarex A327. The carriers investigated were TBP (phosphoric ester),
14 Cyanex 923 (phosphine oxide), Primene JMT (primary amine), Amberlite LA2
15 (secondary amine) and Aliquat 366 (quaternary ammonium salt). Results are
16 summarized in Table 5, showing the best and comparable Cr(VI) permeabilities when
17 Hostarex A327 and Aliquat 366 are used as carriers.
18
19 4. Conclusions
20
21 The transport of Cr(VI) can be effectively carried out, in a SLM permeation cell,
22 using Hostarex A327 in cumene as carrier using the emulsion pertraction operation
23 mode. Metal transport is influenced by a number of variables of the source phase
24 (stirring speed, HCl concentration, metal concentration), the organic phase (diluent,

13
1 carrier concentration) and the stripping phase (composition of the solution). Cr(VI)
2 permeation is independent of carrier concentration when higher concentrations are used,
3 and thus, the transport process is controlled by the diffusion in the aqueous stagnant
4 film. The values of the mass transfer coefficient of the aqueous film and the thickness of
5 the aqueous boundary layer are estimated as 9.2x10
-3
cm s
-1
and 1.1x10
-3
cm,
6 respectively. Cr(VI) can be separated from other metals present in the source phase,
7 however, Cr(VI) transport is negatively affected. The advantage of using Hostarex
8 A327 in cumene, as carrier for Cr(VI) transport, against other extractants is
9 demonstrated, a comparable permeation coefficient value is obtained that when using
10 Aliquat 366 and with a slightly higher Cr(VI) recovery in the stripping phase
11
12 Acknowledgements
13
14 To the CSIC for support. Also to Mr. Bascones for technical assistance.
15
16 References
17
18 Alguacil, F.J., Alonso, M., 2005. Description of transport mechanism during the
19 elimination of copper(II) from wastewaters using supported liquid membranes and
20 Acorga M5640 as carrier. Environ. Sci. Technol. 39, 2389-2393.
21 Alguacil, F.J., Alonso, M., Sastre, A.M., 2002. Copper separation from nitrate/nitric
22 acid media using Acorga M5640 extractant Part II: Supported liquid membrane study.
23 Chem. Eng. J. 85, 265-272.

14
1
2
Alguacil, F.J., Alonso, M., Sastre, A.M., 2005. Facilitated supported liquid membrane transport of gold(I) and gold(III) using Cyanex
®
921. J. Membrane Sci. 252, 237-244.
3 Alguacil, F.J., Coedo, A.G., Dorado, M.T., 2000. Transport of chromium (VI) through a
4 Cyanex 923-xylene flat sheet supported liquid membrane. Hydrometallurgy 57, 51-56.
5 Alguacil, F.J., Lopez-Delgado, A., Alonso, M., Sastre, A.M., 2004. The phosphine
6 oxides Cyanex 921 and Cyanex 923 as carriers for facilitated transport of chromium
7 (VI)-chloride aqueous system. Chemosphere 57, 813-819.
8 Alguacil, F.J., Villegas, M.A., 2002. Liquid membranes and the treatment of metal-
9 bearing wastewaters. Rev. Metal. MADRID 38, 45-55.
10 Alonso, M., Lopez-Delgado, A., Sastre, A.M., Alguacil, F.J., 2006. Kinetic modelling
11 of the facilitated transport of cadmium (II) using Cyanex 923 as ionophore. Chem. Eng.
12 J. 118, 213-219.
13 Beszedits, S., 1988. Chromium removal from industrial wastewaters. In: Nrigau, J.O.,
14 Nieboer, E., (Eds.). Chromium in the Natural and Human Environment. Wiley, New
15 York.
16 Bringas, E., Fresnedo San Roman, M., Ortiz, I. 2006b. Separation and recovery of
17 anionic pollutants by the emulsion pertraction technology. Remediation of polluted
18 groundwaters with Cr(VI). Ind. Eng. Chem. Res. 45, 4295-4303.
19 Bringas, E., San Roman, M.F., Urtiaga, A.M., Ortiz, I., 2006a. Intensification of
20 membrane processes. Remediation of groundwaters by emulsion pertraction as a case
21 study. Desalination 200, 459-461.
22 Casadevall, M., Kortenkamp, A., 2002. Chromium and cancer. In: Sarkar, B., (Ed.).
23 Heavy Metals in the Environment. Marcel Dekker, New York.

15
1 Chiha, M., Samar, M.H., Hamdaoui, O. 2006. Extraction of chromium (VI) from
2 sulphuric acid aqueous solutions by liquid surfactant membrane (LSM). Desalination
3 194, 69-80.
4 Eliceche, A.M., Corvalan, S.M., Fresnedo de San Roman, M., Ortiz, I. 2005. Minimum
5 membrane area of an emulsion pertraction process for Cr(VI) removal and recovery.
6 Comput. Chem. Eng. 29, 1483-1490.
7 Fresnedo San Roman, M., Bringas, E., Ortiz, I., Grossman, E. 2007. Optimal synthesis
8 of an emulsion pertraction process for the removal of pollutant anions in industrial
9 wastewater systems. Comput. Chem. Eng. 31, 456-465.
10 Galan, B., Calzada, M., Ortiz, I., 2006. Recycling of Cr(VI) by membrane solvent
11 extraction: Long term performance with the mathematical model. Chem. Eng. J. 124,
12 71-79.
13 Galan, B., Castañeda, D., Ortiz, I., 2005. Removal and recovery of Cr(VI) from polluted
14 ground waters: A comparative study of ion-exchange technologies. Water Research 39,
15 4317-4324.
16 Kozlowski, C.A., Walkoviak, W., 2005. Applicability of liquid membranes in
17 chromium (VI) transport with amines as ion carriers. J. Membrane Sci. 266, 143-150.
18 Nghiem, L.D., Mornane, P., Potter, I.D., Perera, J.M., Cattrall, R.W., Kolev, S.D., 2006.
19 Extraction and transport of metal ions and small organic compounds using polymer
20 inclusion membranes (PIMs). J. Membrane Sci. 281, 7-41.
21 Ruffo, J., Miret, A., Cortina, J.L., Sastre, A., 1996. Recovery of chromium (VI) using
22 solid-supported liquid membranes. In: Piccini, N., Delorenzo, R., (Eds.). Proceedings
23 of the European Meeting of Chemical Industry and Environment II, Cerdeña.
24

16
1 Table 1
2 Influence of the stirring speed in Cr(VI) permeation
Speed (rpm)
250
500
1000
P (cm s
-1
)
1.5x10
-3
3.7x10
-3
3.6x10
-3
3.8x10
-3 1500
3
4
Source phase: 0.02 g L -1 Cr(VI) and 1 M HCl. Membrane: Durapore GVHP 4700. Organic phase: 10% v/v Hostarex A 327 in cumene. Stripping phase: 0.1 M NaOH.
5
6
7
8
9
10
11 Table 2
12 Influence of the composition of the stripping phase on Cr(VI) transport and recovery
Stripping phase (M NaOH) P (cm s -1 ) % R Phase separation
0.01
0.05
0.1
1.6x10
-3
2.5x10
-3
3.8x10
-3
3.6x10
-3
39
60
83
Good
Fair
Fair
0.2 79 Poor
13
14
15
Source phase: 0.02 g L -1 Cr(VI) and 1 M HCl. Membrane: Durapore GVHP 4700. Organic phase: 10% v/v Hostarex A 327 in cumene.

17
1 Table 3
2 Influence of HCl concentration on Cr(VI) transport
HCl (M) P (cm s
-1
)
2.9x10
-3
Nil
10
-3
10
-2
10 -1
6.4x10
6.8x10
-3
-3
5.0x10
-3
3.8x10
-3
1
3
4
5
Source phase: 0.02 g L -1 Cr(VI) at different HCl concentrations. Membrane: Durapore GVHP 4700.
Organic phase: 10% v/v Hostarex A 327 in cumene. Stripping phase: 0.1 M NaOH.
6
7
8 Table 4
9 Cr(VI) transport in presence of different metallic ions
System
Cr (VI)
P
Cr
(cm s
-1
)
6.8x10
-3
Remark
Cr(VI)-Mn(VII)
Cr(VI)-Fe(III)
Cr(VI)-Ni(II)
3.3x10
-3
2.8x10
-3
3.5x10
-3
No Mn transport
No Fe transport
No Ni transport
Cr(VI)-Cu(II)
Cr(VI)-Zn(II)
3.8x10
-3
3.2x10
-3
No Cu transport
P
Zn
: 8.0x10
-4
cm s
-1
10
11
12
Source phase: 0.02 g L -1 Cr(VI) and 0.02 g L -1 of each metal and 10 -2 M HCl. Membrane: Durapore
GVHP4700. Organic phase: 10% v/v Hostarex A327 in cumene. Stripping phase: 0.1 M NaOH.

18
13
14
15
16
17
18
8
9
10
11
12
1 Table 5
2 Cr(VI) transport using different carriers
Extractant
Hostarex A327
P (cm s
-1
)
6.8x10
-3
Amberlite LA2
Primene JMT
Aliquat 366
Cyanex 923
TBP
6.0x10
-3
5.7x10
-3
6.6x10
-3
1.6x10
-3
8.1x10
-4
% R
83
92
46
71
42
Phase separation
Fair
Good
Fair
Good
Poor
38 Poor
3
4
5
Source phase: 0.02 g L -1 Cr(VI) and 10 -2 M HCl. Membrane: Durapore GVHP 4700. Organic phase: 10% v/v of extractant in cumene. Stripping phase: 0.1 M NaOH.
6
7

19
1 Fig.1. Schematic profile of the species across the supported liquid membrane.
2 Fig.2. Effect of various diluents on permeability of Cr(VI). Source phase: 0.02 g L
-1
3 Cr(VI and 10 -2 M HCl. Membrane: Durapore GVHP4700. Organic phase: 10% v/v
4 Hostarex A327 in each diluent. Stripping phase: 0.1 M NaOH.
5 Fig.3. The influence of initial concentration of Cr(VI) on the permeability flux (J) of the
6 metal. Source phase: various Cr(VI) concentrations and 10
-2
M HCl. Membrane:
7 Durapore GVHP4700. Organic phase: 10% v/v Hostarex A327 in cumene. Stripping
8 phase: 0.1 M NaOH.
14
15
16
24
25
26
27
21
22
23
17
18
19
20
9 Fig.4. The influence of Hostarex A327 concentration on permeability of Cr(VI). Source
10 phase: 0.02 g L
-1
Cr(VI) and 10
-2
M HCl. Membrane: Durapore GVHP4700. Organic
11 phase: Hostarex A327 in cumene. Receiving phase: 0.1 M NaOH.
12
13

32
33
34
35
36
28
29
30
31
25
26
27
19
21
22
23
24
13
14
15
16
9
10
11
12
17
18
3
5
6
7
8
1
2
Fig.1
Fig.2
20

25
26
27
28
21
22
23
24
29
30
31
11
12
13
14
9
10
7
8
15
16
17
19
20
32
2
3
4
5
6
Fig.3
Fig.4
21