# Simultaneous Electrochemical Removal of Selenium and Strontium from Aqueous Solution
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Process** & **Conditions** &
\begin{tabular}{c} **Removal** \\ **Efficiency** \\ \end{tabular} & **Refs.** \\ \hline Hybrid EC membrane process & 1.5 L, 4 Fe anodes, 4 SS cathodes, 48 A m\({}^{-2}\), 20 min & 98.7\% of Se & [23] \\ EC & 0.5 L, Fe/Al anodes, 0.2/0.3 A, 60 min & 97/96\% of Se\({}^{0}\) & [16] \\ EC & 1 L, 2 Fe electrodes, 153 A m\({}^{-2}\), pH 5, added NaCl, & 90\% of Se & [24] \\ EC & 6 h, initial concentration of 0.3 mg L\({}^{-1}\) & & \\ EC & 3 L, 4 Al anodes, 4 Fe cathodes, 4 A m\({}^{-2}\), 15 mM & & \\ EC & NaCl, 52 min, initial concentration of 0.1 mg L\({}^{-1}\) & & \\ EC & 0.2 L, 2 SS/Al electrodes, 80 A m\({}^{-2}\), 50 min & 93/77\% of Sr & [15] \\ Simultaneous EC and adsorption process & 1.5 L, 4 Al electrodes, 75 A m\({}^{-2}\), 120 min & 72\% of Sr & [25] \\ EC & 0.4 L, 2 Fe electrodes, 11.5 A, 30 min, initial concentration of 1.14 mg L\({}^{-1}\) & 99.5\% of Sr & [26] \\ EC & 1 L, Mg anode, 8 A m\({}^{-2}\), pH 7 & 97\% of Sr & [4] \\ Sono-EC & 5.5 L, 4 Fe and 4 Al electrodes, 12.5 A, 10 min, initial concentration of 3 mg L\({}^{-1}\) & 93\% of Se & [27] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Literature review of electrochemical processes for the removal of Se and Sr.  
an electric current through the water containing some electrolyte [31,33]. This process fundamentally relies on two half-reactions occurring at the two electrodes (cathode and anode) immersed in the water. At the cathode, water is reduced to hydrogen gas and hydroxide ions. At the anode, the production of hydroxide ions increases the pH of the solution, making it more basic. Water is oxidized to oxygen gas and hydrogen ions at the anode [32]. The release of hydrogen ions decreases the pH of the solution, making it more acidic. By adjusting the electrical current and the duration of electrolysis, the amount of hydrogen ions (H\({}^{+}\)) or hydroxide ions (OH\({}^{-}\)) generated can be controlled, thereby adjusting the pH of the solution effectively [31,33]. Ion-selective membranes, such as cation-exchange and anion-exchange membranes, are often employed in electrochemical systems. These membranes selectively allow for specific ions to pass, effectively managing the ion transport to maintain or alter the pH in designated areas of the system [33]. Furthermore, membranes help concentrate ions in specific areas, reducing the overall energy required for ion movement and reaction processes. They also separate the electrodes to prevent the mixing of gases (hydrogen and oxygen) produced at each electrode, maintaining effective pH adjustments [33]. This method of pH control is advantageous because it avoids the addition of chemical reagents, allowing for a cleaner and potentially automated process of adjusting the pH in various applications, ranging from industrial processes to environmental management [31]. The aim of this study was to investigate the simultaneous electrochemical removal of Se and Sr from wastewater using a novel three-stage, two-phase (two-cycle) electrochemical reactor. To the best of our knowledge, this study was the first to explore the synergistic effects of electrochemical pH control combined with electrocoagulation for wastewater purification, primarily for the removal of Se and Sr from water. This research introduced an innovative approach where pH control was executed in two separate reactors, each set to different pH values, and across two phases (cycles) with an interchange of pH settings between the reactors in the second phase. Such a synergistic interaction resulted in a significantly greater efficiency for the contaminant removal compared with previously published studies, where it achieved higher purification levels in a substantially shorter time frame. Moreover, this method avoided the potential generation of harmful byproducts that can occur with chemical pH control.