Comparison of single layer Graphite/MnO_x and Ti/MnO_x electrodes: Using in electrochemical oxidation treatment of real saline wastewater

In this study, the electrodeposition method was used to fabricate MnO_x electrode on titanium and graphite substrates for use in real saline wastewater treatment systems by the electro-oxidation. Comparison of electrochemical efficiency in treatment systems between these two substrates showed that the best fabricating conditions are current density: 2.5 mA/cm², time: 1 and 5 min, temperature: 50 and 35 °C, solution concentration: 0.1 and 0.05 M and calcination at a temperature of 500 and 300 °C for 1 h, which leads to the formation of a crystal structure of Mn₂O₃ and α-MnO₂ in the case of using titanium and graphite substrate, respectively. The results showed the capacity of 8210 µF/cm² and 70 % Chemical Oxygen Demand (COD) removal after 2 min for titanium substrate and 84,000 µF/cm² and 98.2 % COD removal after 70 min for graphite substrate. The energy consumption in the fabricating process on the titanium substrate is more than that of graphite (7 × 10⁻³ > 2.78 × 10⁻³ kWh) and the energy consumption of produced water treatment with graphite substrate is more than that of titanium (7.7 × 10⁻³ > 0.32 × 10⁻³ kWh/mg COD removal). The results showed that titanium substrate has high resistance against chemical and physical degradation, while graphite showed high resistance against electrochemical degradation. This study also demonstrates the integration of machine learning, specifically Artificial Neural Network (ANN), for process optimization. The ANN model accurately identified optimal parameters for electrode fabrication. To achieve maximum electrochemical capacity, these results show that the proposed MnO_x electrode is very efficient in treating real saline produced water by electro-oxidation method and also in electrochemical energy storage.