Singlet Oxygen-Mediated Electrochemical Filter for Selective and Rapid Degradation of Organic Compounds

Singlet oxygen (O-1(2))-based homogeneous oxidation pro cesses have been extensively investigated for selective degradation of organic substrates. Herein, to address the existing limitations of these homogeneous systems, we rationally designed a heterogeneous O-1(2)-mediated flow-through electrochemical system based on a functional carbon nanotubes cathode filter. We showed that hydrogen peroxide (H2O2), which was produced in situ with the application of an electric field, reacted with the hypochlorous ion (CIO-) electrolyte to produce O-1(2). Electrochemical filtration of 0.03 mA/1 Methylene Blue (MB) at -2.5 V and a flow rate of 1.0 mL/min resulted in an oxidation flux of 2.62 +/- 0.04 mmol/(h m(2)). The flow-through design introduced more convection, which lead to enhanced mass transport and, in turn, faster oxidation kinetics of organic compounds. Moreover, the oxidation of a mixed solution of cationic MB, cationic Rhodamine 6G (R6G), and anionic Methyl Orange (MO) yielded the selective oxidation of only MB and R6G, where the oxidation flux of MB and R6G was 3.7 and 3.0 times, respectively, greater than that of MO. In particular, the flow-through system exhibited a remarkable 20-times-higher MB oxidation efficiency, when compared with a conventional batch configuration (95.8% vs 4.9%). Electron paramagnetic resonance (EPR) techniques and quenching experiments verified the essential role of O-1(2). The proposed flow-through system may provide a highly potent, efficient, and rapid approach for selective environmental remediation.