A sustainable activated carbon fiber/TiO 2 cathode for the photoelectro-Fenton treatment of pharmaceutical pollutant enalapril.

In this work, a TiO ₂ -decorated electrode was fabricated by dip coating activated carbon fibers (ACF) with TiO ₂ , which were then used as a cathode for the photoelectro-Fenton (PEF) treatment of the pharmaceutical enalapril, an angiotensin-converting enzyme inhibitor that has been detected in several waterways. The TiO ₂ coating was found to principally improve the electrocatalytic properties of ACF for H ₂ O ₂ production via the 2-e ^- O ₂ reduction, in turn increasing enalapril degradation by PEF. The effect of the current density on the mineralization of enalapril was evaluated and the highest TOC removal yield (80.5% in 3 h) was obtained at 8.33 mA cm ^-2 , in the presence of 0.5 mmol L ^-1 of Fe ²⁺ catalyst. Under those conditions, enalapril was totally removed within the first 10 min of treatment with a rate constant k = 0.472 min ^-1 . In contrast, uncoated ACF only achieved 60% of TOC removal in 3 h at 8.33 mA cm ^-2 . A degradation pathway for enalapril mineralization is proposed, based on the degradation by-products identified during treatment. Overall, the results demonstrate the promises of TiO ₂ cathodes for PEF, a strategy that has often been overlooked in favor of photoelectrocatalysis (PEC) based on TiO ₂ -modified photoanodes.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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