Enhancing Ion Transfer in Overlimiting Electrodialysis of Dilute Solutions by Modifying the Surface of Heterogeneous Ion-Exchange Membranes

Figure 3

Concentration dependence of Na⁺ mass-transfer coefficients across MK-40 and MK-40/Nf cation-exchange membranes and Cl⁻ across MA-40 and MA-40M anion-exchange membranes forming desalination channels in a cell shown in Figure 2 under different potential drops (Δ𝜑) per cell pair: 2.5 V (a), 4.0 V (b), and 6 V (c). The limiting mass-transfer coefficient for the DC without spacer, 𝑘^theor_lim, is calculated according to (7); the limiting mass-transfer coefficient for DC with spacer, 𝑘_lims, is evaluated as described in the text.

(a)

(b)

(c)