Figure 14.
Schematic diagram of the test for ion conductivity [106].
Bipolar Membranes
Some cases of membrane adaption have led to the use of bipolar membranes to sep-
arate the acids and bases from a mixture. This has been advantageously applied to lithium
extraction due to the aqueous nature of the feed solution [107]. By conjunction with bipo-
lar membranes and ion-exchange membranes, Li is efficiently separated from existing co-
ions as well as effectively separating boron in the same manner (Figure 15) [95].
Figure 15.
Schematic Diagram of Bipolar and Ion
−
exchange Membrane for Lithium and Boron Har-
vesting [95].
Hwang et al. designed an enhanced bipolar membrane electro-dialysis (BEDI) to re-
cover lithium ions from lithium manganese oxide (LMO) [108]. Three types of bipolar
membranes modules were designed; bipolar membrane modules with 2 sheets, 3 sheets,
and 4 sheets. The conditions for optimal lithium recovery such as pH, voltage and flow
rates were evaluated. The authors revealed that at the optimum conditions when the num-
ber of bipolar membrane sheets was 4, under a pH lower than 4, a voltage of 6.5 V and a
flow rate of 0.44 mL cm
−
2
min
−
1
, the desorption efficiency of lithium was approximately
Figure 15.
Schematic Diagram of Bipolar and Ion
−
exchange Membrane for Lithium and Boron
Harvesting [
95
].
Hwang et al. designed an enhanced bipolar membrane electro-dialysis (BEDI) to
recover lithium ions from lithium manganese oxide (LMO) [
108
]. Three types of bipolar
membranes modules were designed; bipolar membrane modules with 2 sheets, 3 sheets,
and 4 sheets. The conditions for optimal lithium recovery such as pH, voltage and flow rates
were evaluated. The authors revealed that at the optimum conditions when the number of
bipolar membrane sheets was 4, under a pH lower than 4, a voltage of 6.5 V and a flow rate
of 0.44 mL cm
−
2
min
−
1
, the desorption efficiency of lithium was approximately 70%, with
recovery time reduced by approximately 180 min compared to the chemical process.
Another type of bipolar membrane process for lithium and cobalt separation was
bipolar membrane electrodialysis coupled with metal-ion chelation (EDTA) reported by
Lizuka et al. [
42
]. The separation experiment was conducted using a three-cell type of
electrodialysis system as shown in Figure
16
[
42
]. The electrodialysis unit consists of three
cells divided by two bipolar membranes (BPM), one anion-exchange membrane (AEM),
and one cation-exchange membrane (CEM). The cobalt ions were chelated by EDTA and
lithium-ion was hardly chelated. The selectivity for each metal was approximately 99%.
Membranes
2022
,
12
, x
18 of 29
70%, with recovery time reduced by approximately 180 min compared to the chemical
process.
Another type of bipolar membrane process for lithium and cobalt separation was bi-
polar membrane electrodialysis coupled with metal-ion chelation (EDTA) reported by Li-
zuka et al. [42]. The separation experiment was conducted using a three-cell type of elec-
trodialysis system as shown in Figure 16 [42]. The electrodialysis unit consists of three
cells divided by two bipolar membranes (BPM), one anion-exchange membrane (AEM),
and one cation-exchange membrane (CEM). The cobalt ions were chelated by EDTA and
lithium-ion was hardly chelated. The selectivity for each metal was approximately 99%.
Do'stlaringiz bilan baham: |