## 3 Results and Discussion
### ED Using Two-Compartment Cell  
In order to test the influence of the imposed current density on Li+ transport through the LCM and its selectivity towards Li+, ED experiments were performed for 4 h using a solution at equal concentrations [Li+]F = [Na+]F = 0.05 M. These experiments were performed in the ED two-compartment cell. The obtained results are summarized in Figure 3.  
An increase of the current density from 0.5 to 12.0 mA\(\cdot\)cm\({}^{-2}\) improves the transport of both cations through the LCM. Hence, the recovered ionic concentration increased from 0.592 to 6.920 mmol\(\cdot\)L\({}^{-1}\) for Li+ (that is 11.7-times more) and from 0.019 to 0.875 mmol\(\cdot\)L\({}^{-1}\) for Na+ (that is 46.1 times more). The more rapid increase rate in the concentration of Na+ in the receiver, than that of Li+, leads to a significant reduction of membrane selectivity from 31.7 to 7.9 (that is four-times less). This difference in the transport rate of the two cations can be explained by a combination of numerous factors detailed here below. The transport of the two cations Li+ and Na+ through the LCM membrane is carried out in two ways: (i) mainly by successive jumps between vacancy sites of the interconnected LICGC particles [50], (ii) and slightly by leakage through the polymer containing positively charged sites and the membrane imperfections [51; 52] by diffusion (under concentration gradient) or by migration (under the applied current). The transport of Li+ takes place preferably through the particles of LICGC, which have very high selectivity towards this cation. The Li+ leakage through the positively charged polymer and membrane imperfections remains possible but much less important than that of Na+ due to the difference in their hydrated radius and mobilities when they are in aqueous solutions, as shown in Table 2. However, this difference is amplified when it comes to a dense medium, such as a charged polymer. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Cations**} & **Hydrated Radius** & **Mobility** & **Diffusion Coefficients** \\  & **R\({}_{\text{H}}\) (Å)**[53] & **u (10\({}^{-8}\) m\({}^{2}\cdot\)s\({}^{-1}\cdot\)v\({}^{-1}\))**[54] & **D (10\({}^{-9}\) m\({}^{2}\cdot\)s\({}^{-1}\))**[55] \\ \hline H+ & - & 36.23 & 9.31 \\ Na+ & 3.58 & 5.19 & 1.33 \\ Li+ & 3.82 & 4.01 & 1.03 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Characteristics of involved cations in aqueous solutions. Figure 3: Effect of imposed current density on the Li+/Na+ separation performance of LCM using a two-compartment cell and for [Li+]F = [Na+]F = 0.05 M.  
As a function of current density, Li\({}^{+}\) transport continuously/correspondingly increases across the entire membrane section; it rises more rapidly through the interconnected LICGC particles and more slightly through the used polymer when compared to Na\({}^{+}\) ones. It should be noted that, under the effect of the applied current, the Na\({}^{+}\) ions can also compete with the Li\({}^{+}\) ions through the LICGC particles; however, this mode of Na\({}^{+}\) transport remains marginal under our operating conditions (a relatively weak current and a fairly dilute solution). Furthermore, proton production at the anode compartment influences the separation performance of the LCM. These generated protons compete with other cations (Li\({}^{+}\) and Na\({}^{+}\)), and they carry a portion of the electrical charge through the LCM. According to the data in Table 2, these H\({}^{+}\) have a much higher mobility and diffusion coefficient than other cations; therefore, they can more easily pass through the different components of the LCM membrane: they can pass through the LICGC by Li\({}^{+}\)/H\({}^{+}\) exchange (as Lithium Ions Sieves) [56] and through the used charged polymer by protons leakage [57]. Gases are also produced at the electrode surface (H\({}_{2}\) in the cathode, O\({}_{2}\) and especially Cl\({}_{2}\) in the anode).