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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