Herein, a silicate-enhanced flow-through electro-Fenton system with a nanoconfined catalyst was rationally designed and demonstrated for the highly efficient, rapid, and selective degradation of antibiotic tetracycline. The key active component of this system is the Fe2O3 nanoparticle filled carbon nanotube (Fe2O3-in-CNT) filter. Under an electric field, this composite filter enabled in situ H2O2 generation, which was converted to reactive oxygen species accompanied by the redox cycling of Fe3+/Fe2+. The presence of the silicate electrolyte significantly boosted the H2O2 yield by preventing the O–O bond dissociation of the adsorbed OOH*. Compared with the surface coated Fe2O3 on the CNT (Fe2O3-out-CNT) filter, the Fe2O3-in-CNT filter demonstrated 1.65 times higher k L value toward the degradation of the antibiotic tetracycline. Electron paramagnetic resonance and radical quenching tests synergistically verified that the dominant radical species was the 1O2 or HO· in the confined Fe2O3-in-CNT or unconfined Fe2O3-out-CNT system, respectively. The flow-through configuration offered improved tetracycline degradation kinetics, which was 5.1 times higher (at flow rate of 1.5 mL min–1) than that of a conventional batch reactor. Liquid chromatography–mass spectrometry measurements and theoretical calculations suggested reduced toxicity of fragments of tetracycline formed. This study provides a novel strategy by integrating state-of-the-art material science, Fenton chemistry, and microfiltration technology for environmental remediation.

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Singlet oxygen ( 1 O 2 )-based homogeneous oxidation processes 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 1 O 2mediated flow-through electrochemical system based on a functional carbon nanotubes cathode filter. We showed that hydrogen peroxide (H 2 O 2 ), which was produced in situ with the application of an electric field, reacted with the hypochlorous ion (ClO − ) electrolyte to produce 1 O 2 . Electrochemical filtration of 0.03 mM 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 1 O 2 . The proposed flow-through system may provide a highly potent, efficient, and rapid approach for selective environmental remediation.