The kinetics, current efficiency, and power consumption of electrochemical dye decolorization by BD-NCD film electrode

Diamond film electrode has been known as a material with very wide potential window for water electrolysis which leads to its applicability in numerous electrochemical processes. Its capability to produce hydroxyl radicals, a very strong oxidants, prompts its popular application in wastewater treatment. Batch and batch recirculation reactor were applied to perform bulk electrolysis experiments to investigate the kinetics of dye decolorization under different operation conditions, such as pH, active species, and current density. Furthermore, COD degradation data from batch recirculation reactor operation was used as the basis for the calculation of current efficiency and power consumption in the decolorization process. The kinetics of decolorization process using boron-doped nanocrystalline diamond (BD-NCD) film electrode revealed that acidic condition is favored for the dye degradation, and the presence of chloride ion in the solution was found to be more advantageous than sulfate active species, as evidenced by the higher reaction rate constants. Applying different current density of 10, 20 and 30 mA cm−2, it was found that the higher the current density the faster the decolorization rate. General current efficiency achieved after nearly total decolorization and ~80% COD removal in batch recirculation reactor was around 74%, with specific power consumption of 4.4 kWh m−3 (in terms of volume of solution treated) or 145 kWh kg−1(in terms of kg COD treated).