178
L. Brown et al.
Aqueous Phase
Ionic Phase
Fig. 7.10 A photograph of nickel(II) chloride (left), cobalt(II) chloride (center), and copper(II)
chloride (right) dissolved in a water/[P 6 6 6 14 ][Cl]/ethyl ethanoate (4:1:1 v/v/v) biphasic solvent
system. The upper phase is the ionic liquid [P 6 6 6 14 ][Cl]/ethyl ethanoate mixture and the lower
phase is water saturated with ethyl ethanoate (7.6 wt%)
Table 7.2 The distribution ratios of the metal(II) chloride complexes in the biphasic
water/[P 6 6 6 14 ][Cl]/ethyl ethanoate (4:1:1 v/v/v) solvent system
Metal Temp. (°C) Peak maximum (min) DR from ILLC
separation
DR from UV-Vis
spectrometer
Ni
30
23.5
0.31
0.2
Co
30
29.5
0.62
0.6
Cu
30
56.8
2.22
2.2
Ni
40
20.8
0.16
0.2
Co
40
29.8
0.66
0.6
Cu
40
55.3
2.07
2.1
DR = Distribution Ratio
The metals are presumed to exist as the tetrahedral [MCl 4 ]
2− complexes in the ionic
phase (Fig. 7.11) [55].
The separation was carried out at 30 and 40 °C and is shown in Fig. 7.12. A
partial separation was obtained with the cobalt(II) chloride peak overlapping the
start of the copper peak and the end of the nickel peak. At 40 °C, the performance
of the separation improved, and the separation time was reduced from 68 to 61 min.
M
OH 2
H 2 O
O H 2
OH 2
H 2 O
OH 2
M
Cl
Cl
Cl
Cl
+ 4 Cl
-
+ 6 H 2 O
2 +
2 -
Fig. 7.11 The behavior of metal(II) chloride complexes (Co, Ni, or Cu) in the biphasic
water/[P 6 6 6 14 ][Cl]/ethyl ethanoate (4:1:1 v/v/v) solvent system