Construction of a Microchannel Electrochemical Reactor with a Monolithic Porous-Carbon Cathode for Adsorption and Degradation of Organic Pollutants in Several Minutes of Retention Time

A monolithic porous-carbon (MPC) electrode was fabricated to simultaneously intensify mass transfer and enhance reaction activity. The MPC involved channel arrays (about 50 μm of diameter for each channel) with mesopores and micropores in channel walls. The abundant surface pores may improve the reaction efficiency of the reduction of O2 to produce H2O2 and •OH. The function of channel arrays was to shorten the mass-transfer distance not only from O2 to the electrode surface but also from pollutants to the electrode surface and •OH. A microchannel electrochemical reactor was assembled to evaluate the performance of the MPC cathode. For 20 mg/L of phenol, sulfamethoxazole or atrazine, effluent concentration and total organic carbon (TOC) decreased down to 1.5 and 3 mg/L, respectively, in a retention time of only 100–300 s. Phenol removal was dominated by the MPC cathode, and the contribution of cathodic adsorption, cathodic degradation, and anodic reaction was 46, 33, and 8%, respectively. The proper working potential for the MPC cathode was +0.26 to +0.6 V versus reversible hydrogen electrode; in this potential range, no scaling was observed. For the real surface water (the initial TOC was 41.5 mg/L), TOC in effluent (the retention time was 335 s) was stable at 31.0 mg/L.