Silicate-Enhanced Heterogeneous Flow-Through Electro-Fenton System Using Iron Oxides under Nanoconfinement

Abstract

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.

Toward Selective Oxidation of Contaminants in Aqueous Systems

“…In contrast, the removal efficiency decreased by 31% in the control system of the nonconfined Co nanoparticles. Besides, the catalytic activity and stability was improved by using the nanoconfined yolk–shell system. − Moreover, the nanoscale interior cavity is likely to change the product distribution, which has been validated in various reactions in organic synthesis. An example in the wastewater treatment is from Li’s group that phenol was selectively oxidized to maleic acid by HO • in the nanoconfined space …”

Performance and mechanism of removal of antibiotics and antibiotic resistance genes from wastewater by electrochemical carbon nanotube membranes

“…Wu et al ( Wu et al, 2016 ) removed bisphenol A and norfloxacin from drinking water using acid-treated CNTs and polyvinyl chloride ultrafiltration membranes. Guo et al designed a silicate-enhanced fluidized electro-Fenton system with a nanoconfined catalyst for the removal of tetracycline ( Guo et al, 2021 ). Zheng et al designed an electrocatalytic filtration system with carbon nanotube supported nanoscale zerovalent copper toward ultrafast oxidation of organic pollutants ( Zheng et al, 2021 ).…”

Ultraviolet-coupled advanced oxidation processes for anti-COVID-19 drugs treatment: Degradation mechanisms, transformation products and toxicity evolution

“…3 . The anti-COVID-19 degradation kinetics at alkaline pH conditions could be attributed to the reduced H 2 O 2 decomposition to produce the reactive oxygen species (ROS) ( Guo et al, 2021 ). The results revealed that the k constantly decreased with increasing pH.…”