since the counterions
permeate through the membrane and the co-ions are drawn
into the opposite direction. As a result, polarization occurred,
preventing counterions from passing this depleted region, and
the current density cannot be further increased. EG was
successfully retarded during the desalting process (Fig. 4).
Between 7 and 11 wt % of the EG passed the membrane after
5 h of electrodialysis. A correlation with the voltage was not
observed, indicating that diffusion was the driving force.
However, the EG permeation increased with the salt concentration,
since solvated ions carried EG molecules with
them when passing the membrane.
NaCl/EG
Pump
Deionized
water
Anion-exchange
membrane
Carbon electrodes
Cation-exchange
membrane
Naflon cell
Steel plates
Fig. 2 Electrodialysis stack
0 2 46
0
20
40
60
80
100
2V
4V
8V
12V
Cl− removal / %
Time / h
1 35 0246 0
20
40
60
80
100
2V
4V
8V
12V
Na+ removal / %
Time / h
135
(a) (b) Fig. 3 Effect of voltage on
(a) Cl- and (b) Na? removal
from NaCl/EG solution with
time. NaCl concentration:
0.5 wt %
J Mater Cycles Waste Manag (2013) 15:111–114 113
1