Expanding the application of photoelectro-Fenton treatment to urban wastewater using the Fe(III)-EDDS complex

Zhihong Ye; Enric Brillas; Francesc Centellas; Pere Lluís Cabot; Ignasi Sirés

doi:10.1016/j.watres.2019.115219

Expanding the application of photoelectro-Fenton treatment to urban wastewater using the Fe(III)-EDDS complex

Water Res. 2020 Feb 1:169:115219. doi: 10.1016/j.watres.2019.115219. Epub 2019 Oct 23.

Authors

Zhihong Ye¹, Enric Brillas¹, Francesc Centellas¹, Pere Lluís Cabot¹, Ignasi Sirés²

Affiliations

¹ Laboratori d'Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028, Barcelona, Spain.
² Laboratori d'Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028, Barcelona, Spain. Electronic address: i.sires@ub.edu.

PMID: 31689603
DOI: 10.1016/j.watres.2019.115219

Abstract

This work reports the first investigation on the use of EDDS as chelating agent in photoelectro-Fenton (PEF) treatment of water at near-neutral pH. As a case study, the removal of the antidepressant fluoxetine was optimized, using an electrochemical cell composed of an IrO₂-based anode an air-diffusion cathode for in-situ H₂O₂ production. Electrolytic trials at constant current were made in ultrapure water with different electrolytes, as well as in urban wastewater (secondary effluent) at pH 7.2. PEF with Fe(III)-EDDS (1:1) complex as catalyst outperformed electro-Fenton and PEF processes with uncomplexed Fe(II) or Fe(III). This can be explained by: (i) the larger solubilization of iron ions during the trials, favoring the production of ^•OH from Fenton-like reactions between H₂O₂ and Fe(II)-EDDS or Fe(III)-EDDS, and (ii) the occurrence of Fe(II) regeneration from Fe(III)-EDDS photoreduction, which was more efficient than conventional photo-Fenton reaction with uncomplexed Fe(III). The greatest drug concentration decays were achieved at low pH, using only 0.10 mM Fe(III)-EDDS, although complete removal in wastewater was feasible only with 0.20 mM Fe(III)-EDDS due to the greater formation of ^•OH. The effect of the applied current and anode nature was rather insignificant. A progressive destruction of the catalytic complex was unveiled, whereupon the mineralization mainly progressed thanks to the action of ^•OH adsorbed on the anode surface. Despite the incomplete mineralization using BDD as the anode, a remarkable toxicity decrease was determined. Fluoxetine degradation yielded F^- and NO₃^- ions, along with several aromatic intermediates. These included two chloro-organics, as a result of the anodic oxidation of Cl^- to active chlorine. A detailed mechanism for the Fe(III)-EDDS-catalyzed PEF treatment of fluoxetine in urban wastewater is finally proposed.

Keywords: Ethylenediamine-N,N′-disuccinic (EDDS) acid; Fluoxetine; Gas-diffusion electrode; Hydrogen peroxide; Photoelectro-Fenton; Urban wastewater.

MeSH terms

Electrodes
Ferric Compounds
Hydrogen Peroxide
Iron
Oxidation-Reduction
Wastewater*
Water Pollutants, Chemical*

Substances

Ferric Compounds
Waste Water
Water Pollutants, Chemical
Hydrogen Peroxide
Iron