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A new 3D-printed photoelectrocatalytic reactor combining the benefits of a transparent electrode and the Fenton reaction for advanced wastewater treatment

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Abstract

A new TiO2-coated stirred glass reactor was designed, comprising a film of fluorine-doped tin oxide (FTO) coated on a transparent glass anode. The potential of FTO for the O2 evolution reaction – determined by linear scan voltammetry – was equal to 2.1 V vs. the SHE, high enough to form hydroxyl radicals (˙OH) through anodic oxidation (AO). By letting UVA light shine through the glass reactor coated with an optimal TiO2 loading of 0.311 mg cm−2, heterogeneous photocatalysis occurred, which led to a second source of ˙OH. Coupled with a three-dimensional (3D) carbonaceous cathode and with the addition of a catalytic amount of Fe2+, four more sources of ˙OH could be implemented through H2O2 electro-activation, the Fenton reaction, H2O2 photolysis and Fe(III)-hydroxy complex photolysis. This combined photoelectrocatalytic Fenton process allowed reaching a phenol (chosen as a model pollutant to allow for easy comparison with other processes) degradation rate of 0.0168 min−1 and a mineralization yield of 97% after 8 h of treatment, far better than those of each individual process. Notably, the phenol degradation rate of the combined process was 37% higher than that of electro-Fenton (EF) alone and 42% higher than that of AO alone. A synergy was observed (with a photocatalytic synergy value of SPC = 1.26) in the presence of TiO2, which improved on UV photolysis alone (UV synergy value, SUV = 0.97) and could be further augmented in a novel 3D-printed flow-cell reactor, designed to maximize the distance of electrode separation and the contact between gaseous O2 and the carbon cathode. Indeed, UVA radiation shining through the FTO anode – with a transmissivity of 65% – improved the kinetics of photolytic reactions as compared to dark processes, with a synergy value (SUV) as high as 1.87. Thanks to these enhancements, the overall phenol degradation rate could be further increased to 0.0175 min−1, 14% higher than that within the stirred glass reactor (0.0153 min−1). Following optimization of the current density and Fe2+ concentration, a kinetic rate of degradation of 0.0214 min−1 was attained, an all-time high showcasing the promise of the novel photoelectrocatalytic reactor.

Graphical abstract: A new 3D-printed photoelectrocatalytic reactor combining the benefits of a transparent electrode and the Fenton reaction for advanced wastewater treatment

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Publication details

The article was received on 16 Sep 2017, accepted on 10 Nov 2017 and first published on 10 Nov 2017


Article type: Paper
DOI: 10.1039/C7TA08182K
Citation: J. Mater. Chem. A, 2017, Advance Article
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    A new 3D-printed photoelectrocatalytic reactor combining the benefits of a transparent electrode and the Fenton reaction for advanced wastewater treatment

    E. Mousset, V. Huang Weiqi, B. Foong Yang Kai, J. S. Koh, J. W. Tng, Z. Wang and O. Lefebvre, J. Mater. Chem. A, 2017, Advance Article , DOI: 10.1039/C7TA08182K

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