Transfer of Monovalent and Divalent Cations in Salt Solutions by Electrodialysis

Abstract

The selectivity mechanism of transport of Na þ , Ca 2þ and Mg 2þ through commercial monovalent-cation permselective membranes is investigated in batch electrodialysis experiments with synthetic salt solutions containing monovalent and divalent cations. The role of hydration energy, steric effect, kinetic effect as well as effects of permselectivity of cation exchange membrane has been elucidated with electrodialysis of single solutions (NaCl, CaCl 2 , MgCl 2 ). The mechanism of interferences is investigated in (Na þ /Ca 2þ , Na þ /Mg 2þ , Ca 2þ /Mg 2þ and Na þ /Ca 2þ /Mg 2þ ) mixtures.

How physico-chemical and surface properties of cation-exchange membrane affect membrane scaling and electroconvective vortices: Influence on performance of electrodialysis with pulsed electric field

“…It appears that CMX-SB-1 with less water uptake value is more hydrophobic what may indicate that its structure would contain more compressed internal nanochannels than for CMX-SB-2 [14,15]. In addition, it is known, that migration of Mg 2+ through CEM is the slowest in comparison with Na + and Ca 2+ due to: 1) larger hydration radius and hydration energy of Mg 2+ [51,52] what plays the role of obstacle for the entrance in CEM; 2) higher affinity of Mg 2+ to the SO 3 − groups [49] (Fig. 12a), which prevents it from jumping from site to site inside the CEM.…”

“…This fact leads to the differences in the scaling phenomena and ED performances. Concerning the scaling composition, it can be proposed based on the model previously described elsewhere [14][15][16] that the membrane hydrophobicity and consequently the dimension of membrane internal channels played important role in the competitive migration of Na + , Ca 2+ and Mg 2+ [49,50]. It appears that CMX-SB-1 with less water uptake value is more hydrophobic what may indicate that its structure would contain more compressed internal nanochannels than for CMX-SB-2 [14,15].…”

Treatment of model inland brackish groundwater reverse osmosis concentrate with electrodialysis — Part III: Sensitivity to composition and hydraulic recovery

“…o Ions move at different speeds depending on solution composition and membrane properties [20][21][22]. More specifically, it has been observed that binary salts of potassium were removed more efficiently than sodium salts, and the sulfate salts were removed less efficiently than others [7].…”

Synthesis of a monovalent selective cation exchange membrane to concentrate reverse osmosis brines by electrodialysis

“…Thus, the diffusion theory of cations through a CEM can be applied to explain the selectivity of the membranes. Firdaous et al [10] explains that the hydration shell is the responsible of the cations diffusion in a membrane, although the passing of solution/membrane interface requires overcoming the energy barrier caused by the necessity of partial dehydration of ions. In order to break this barrier, the hydration energy of cations is the effective parameter.…”

“…However, the current efficiency of the resulting membranes decreases due to the strong binding of the cation exchange groups to the bivalent cations, which causes inactivation of cation exchange groups. Attempts were also made to decrease the charge density on the membrane surface, but results according to this method were ineffective [9,10] . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 3 Three influencing parameters have been classified to describe the selective permeation of ions through membranes.…”