Abstract
Multiple discs coated with hierarchically-organized TiO2 anatase nanotubes served as photoelectrodes in a novel annular photoelectrocatalytic reactor. Electrochemical characterization showed light irradiation enhanced the current response due to photogeneration of charge carriers. The pharmaceutical acetaminophen was used as a representative water micropollutant. The photoelectrocatalysis pseudo-first-order rate constant for acetaminophen was seven orders of magnitude greater than electrocatalytic treatment. Compared against photocatalysis alone, our photoelectrocatalytic reactor at <8 V reduced by two fold, the electric energy per order (EEO; kWh m−3 order−1 for 90% pollutant degradation). Applying a cell potential higher than 8 V detrimentally increased EEO. Acetaminophen was degraded across a range of initial concentrations, but absorbance at higher concentration diminished photon transport, resulting in higher EEO. Extended photoelectrocatalytic reactor operation degraded acetaminophen, which was accompanied by 53% mineralization based upon total organic carbon measurements. This proof of concept for our photoelectrocatalytic reactor demonstrated a strategy to increase photo-active surface area in annular reactors.
Highlights
The advanced oxidation processes (AOPs) are used in drinking water and both municipal and industrial wastewater purification to transform organic pollutants into less toxic by-products [1].Among many AOPs, photoelectrocatalysis is an emerging and promising hybrid AOP [2]
Photoelectrocatalysis relies on semiconductor materials to photo-generate charge carriers according to Equation (1); applying a constant voltage across semiconductors supported on solid surfaces prevents recombination within the material [5,6]
The parallel arrangement of Ammonium was continuously released from the breakage of the amide bond and reached a maximum disc photoanodes and cathodes defined a hydraulic pathway for the recirculated solution while providing the requirements for homogeneous current distribution in electrolytic reactors and light delivery for charge carriers’ photogeneration. This novel reactor system can provide an alternative framework when considering the scaling-up of photoelectrocatalytic water treatment
Summary
Among many AOPs, photoelectrocatalysis is an emerging and promising hybrid AOP [2]. This technology provides synergistic benefits from the interaction between photocatalytic and electrocatalytic processes [3,4]. Photoelectrocatalysis relies on semiconductor materials to photo-generate charge carriers according to Equation (1); applying a constant voltage across semiconductors supported on solid surfaces prevents recombination within the material [5,6]. The photoexcitation of electrons from the filled semiconductor valence band to the empty conduction band generates charge carriers when irradiated with photons of energy superior to the band gap (Eg ) [7,8]. Electron (ecb − ) photoexcitation generates a vacancy at the valence band (hvb + ). The hvb + are highly–oxidizing species that can mineralize organic
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