Enhanced electric field intensity in transverse microchannel charcoal electrode for facilitating electrochemical demulsification rate of oil-in-water droplets.

Microchannel cathodes achieve superior emulsified oil removal performance compared to flat electrodes, owing to their capacity to drastically reduce oil droplet migration distance to the micrometer scale and generate electrical polarization. However, in reported reactor designs, the cathode microchannels' axial profile parallel to the anode considerably restricts the efficiency of electrical polarization effect. In this work, we report a novel reactor featuring a transverse microchannel charcoal (TMC) cathode with shortened, ordered microchannels and higher packing density. This configuration orients the radial surface of microchannels parallel to the anode, substantially enhancing the electric field intensity in microchannels and resulting in an exceptional electrochemical demulsification rate. Here, the emulsified oil droplet coalescence time dropped from 20 s to just 2.7 s. Additionally, the energy consumption decreased from 10.3 kWh/t (reported configurations) to 2.08 kWh/t. Moreover, electrochemical demulsification within the TMC cathode was successfully observed in situ. Consistent with expectations, treating actual oily emulsified wastewater from a steel plant (initial oil concentration 362 mg/L) achieved removal rate exceeding 86.2% over 20 h of continuous operation. For metallurgical wastewater with an initial concentration of 127 mg/L, the effluent oil concentration was consistently maintained below 8 mg/L over 100 h, satisfying both the national indirect discharge limit for petroleum hydrocarbons (<15 mg/L, GB 25467-2010) and the stricter internal standard of the enterprise (<10 mg/L). Remarkably, the used electrode can be efficiently regenerated to nearly 100% performance via simple backwash process using ultrapure water. These results provide new perspectives for improving the practicability of electrochemical demulsification using microchannel electrodes.