Application of Pulsed Electrochemistry to Enhanced Water Decontamination

In this study, we report the application of pulsed electrochemistry to enhanced water decontamination by electrochemical oxidation. By applying square current waveforms, the alternating pulse-on/-off operation results in periodic oscillation of anode potential, which is favorable for periodic renewal of electrical double layer (EDL) and alternant conditions for oxidation of organic pollutants. Under mass-transfer dominance at a current density of 20 mA cm–2, the rate constant for phenol oxidation under pulsed-current mode (PC, k = 1.48 h–1) is 52.5% higher than that under direct-current mode (DC, k = 0.97 h–1), accounting for a 57.1% decrease in energy consumption. In comparison with DC, PC does not change the pathway of phenol oxidation but is more selective for less accumulation of characteristic intermediates and efficient mineralization. The duty ratio and pulse period are shown to have a significant impact on the removal of chemical oxygen demand (COD), current efficiency, and energy consumption. The nonsteady diffusion models based on Fick's second law illustrate that the transient local phenol concentration at the anode surface and limiting current density under PC condition are approximately 2.8 times that under DC, which provides a theoretical verification for the EDL-renewal mechanism of pulsed electrochemistry. This study suggests a simple, reliable, and economic route to enhance the performance of electrochemical oxidation, which can also be generalized to other kinds of electro-processes for water purification.