## 3 Results
### Electroflotation of Clays in NaCl Solutions  
The electroflotation process was performed using a modified Hallimond tube with a pair of cylindrical Ti Gr. 2 electrodes, which were connected from the bottom of the device to a variable power supply as shown in Figure 1. The parameter employed to assess the water quality treated by these electrochemical methods is the electroflotation efficiency (Equation (1)). Figure 5 shows images of the slurries before and after the electroflotation process. In the figure, it is possible to observe the changes in the solution appearance, where a large part of the clays was separated. During the electroflotation process, the produced foam revealed a sticky consistency, which is a characteristic inherent to clays when they are in contact with aqueous mediums. Through experiments employing applied cell potentials of 10, 15, and 20 V over durations of 10, 15, and 20 min, it was observed that the current intensity varies significantly, as does the amount of clay recovered over time, reaching a steady-state value close to 0.04 A at the end of the electroflotation process, as is tabulated in Table 2. Under these electroflotation conditions, no notable difference was observed in the cell current at the end of the process. However, changes in this variable could be attributed to several factors, including variations in the solution chemistry due to the presence of multiple ions such as Al\({}^{+3}\), Fe\({}^{+2}\), Fe\({}^{+3}\), Mg\({}^{+2}\), and Na\({}^{+1}\), which come from the dissolution of kaolinite and montmorillonite clays due to their solubility [38]. Additionally, the cell current intensity can be affected by the reduction in the number of active sites on the anodic electrode surface and near the solid-liquid interface, caused by the oxidation of the anodic electrode and further formation of a passive  
Figure 4: XRD patterns of (**a**) montmorillonite and (**b**) kaolinite clays. film composed mainly of TiO\({}_{2}\), following the sequence of electrochemical and chemical reactions [39]:  
\[\text{Ti}\ ^{-2\text{e}^{-}}\ \text{Ti}^{2+}\ ^{-\text{e}^{-}}\ \text{Ti}^{3+}\ ^{-\text{e}^{-}}\ \text{Ti}^{4+} \tag{6}\]  
\[\text{Ti}^{4+}+4\text{OH}^{-}\ \rightarrow\text{TiO}_{2}+2\text{H}_{2}\text{O} \tag{7}\]  
Although the cell current values decreased in magnitude (ranging between 0.03 and 0.05 A, equivalent to 68 and 114 A/m\({}^{2}\)) compared to the beginning of the electrofolotation process (t = 0 min), under the studied conditions (10, 15, and 20 V), water electrolysis was not unfavorable, and oxygen and hydrogen bubble generation was maintained over time. This confirms that cell current densities between 68 and 114 A/m\({}^{2}\) are sufficient for this process. This observation could be related to the increased passive film growth with high anodic oxygen bubble generation at the beginning of the process, where transitions in the crystalline phase of TiO\({}_{2}\) have occurred, which are caused by higher applied cell current densities [40; 41]. However, the good corrosion resistance of TiO\({}_{2}\) passive film in saline environments can be compromised by the high cell voltage and current intensity, promoting the formation of titanium oxychlorides over the passive film by the action of chloride ions, according to the chemical reaction [29]:  
\[\text{Ti}_{\text{x}}\text{O}_{\text{y}}+2\text{Cl}^{-}\rightarrow\text{Ti}_{ \text{x}}\text{O}_{\text{y}}\text{Cl}_{2}+2\text{e}^{-} \tag{8}\]