Linear attenuation current input mode: A novel power supply mode for electrochemical oxidation process

Abstract

At present, the most considerable defects of electro-catalytic process lie in low current efficiency and high specific energy consumption. Besides electrodes, current parameters and reaction system, the power supply mode is also of great significance for optimization of electrochemical oxidation. Traditional power supply modes include constant voltage mode, constant current mode and pulse mode. Based on the concept of limiting current density, this paper proposed a linear attenuation power supply mode and set up three different application modes. This novel power supply mode is to make the current input into the electro-catalytic system continuously decay over reaction time, which were simulated adopting a computer-controlled programmable DC power. Acid Red G, phenol, guaiacol, salicylic acid and actual water samples from sewage treatment plant were taken as the target organic substance, furthermore, the advantages and disadvantages of three linear attenuation modes and traditional constant current mode were compared through electrochemical oxidation experiments in terms of varying evaluation parameters. The experimental results indicated that Mode I (same initial current density, different attenuation rates) obtained higher average current efficiency and lower specific energy consumption than constant current mode in order to achieve the equivalent degradation performance. However, the decolorization rate and COD removal rate of Mode I were lower than those of traditional constant current mode. Mode II (direct linear attenuation) and Mode III (constant current before linear attenuation) were superior to the traditional constant current mode with the same input total power in the aspects of decolorization rate, COD removal rate, average current efficiency, specific energy consumption and etc. Those results were further verified in different organic matters wastewater samples and actual wastewater samples. For actual wastewater samples treatment, the experimental average current efficiency and specific energy consumption of Mode II (6.96 %, 0.237 kWh·gCOD-1), Mode III (8.89 %, 0.209 kWh·gCOD-1) and traditional constant current mode (5.18 %, 0.343 kWh·gCOD-1) indicated that, in practical engineering, more preferable current efficiency and lower energy consumption can be achieved by Mode II and Mode III over traditional constant current mode. Those demonstrated that the newly proposed linear attenuation mode (especially Mode III) can effectively improve the current efficiency of electrochemical oxidation process and reduce the specific energy consumption.