2026/07/01 by Estefanny Quispe Cardenas, Arnd Garsuch, Maximilian Rang +2
Materials Science · Environmental Science · Engineering · #Magnesium Oxide Properties and Applications #Phosphorus and nutrient management #Membrane-based Ion Separation Techniques
paper · pdf · doi:10.1016/j.desal.2026.120549
Electrochemical precipitation can remove hardness-forming ions such as calcium (Ca 2+ ) and magnesium (Mg 2+ ) from seawater during desalination. Increasing the pH necessary to precipitate these cations typically uses high-energy water splitting reactions. Here we studied oxygen reduction at activated carbon (AC) cathodes as a potentially lower-energy reaction to increase pH and drive precipitation in synthetic seawater. We directed influent through AC cloth electrodes fixed at applied whole-cell voltages of 1.2 to 1.8 V. We evaluated the effects of electrode configuration, charging duration, bicarbonate concentration, and dissolved oxygen concentration on mineral precipitation and ion selectivity. Capacitive deionization cycling (repeated charge/discharge cycles) did not improve precipitation nor decrease energy demands compared to applying a constant voltage, indicating that capacitive current was not beneficial for precipitation. In the best performing single-pass operation (two cathodes, one anode, 1 mL min −1 , constant 1.8 V, supplemental oxygen), Ca 2+ and Mg 2+ precipitation reached 32.2 ± 1.3%, and 1.8 ± 0.1%, respectively, primarily as CaCO 3 and Mg-bearing minerals. Visual MINTEQ modeling predicted the formation of these mineral phases, but overestimated precipitation, likely due to slow precipitation kinetics relative to the hydraulic residence time (~14 min). Specific energy consumption was 4.51 ± 1.47 kWh kg −1 of combined Ca 2+ and Mg 2+ precipitated. The highest precipitation occurred in recirculation mode, reaching 58.40 ± 3.54% Ca 2+ and 9.80 ± 0.28% Mg 2+ . Collectively these results show how operational variables influence Ca 2+ and Mg 2+ precipitation driven mainly by oxygen reduction reactions on AC electrodes.