Degradation of the insecticide propoxur by electrochemical advanced oxidation processes using a boron-doped diamond/air-diffusion cell

Guelfi, Diego Roberto Vieira; Gozzi, Fábio; Sirés, Ignasi; Brillas, Enric; Machulek, Amílcar Jr; de Oliveira, Silvio César

Degradation of the insecticide propoxur by electrochemical advanced oxidation processes using a boron-doped diamond/air-diffusion cell

2017

A solution with 0.38 mM of the pesticide propoxur (PX) at pH 3.0 has been comparatively treated by electrochemical oxidation with electrogenerated H₂O₂ (EO-H₂O₂), electro-Fenton (EF), and photoelectro-Fenton (PEF). The trials were carried out with a 100-mL boron-doped diamond (BDD)/air-diffusion cell. The EO-H₂O₂ process had the lowest oxidation ability due to the slow reaction of intermediates with •OH produced from water discharge at the BDD anode. The EF treatment yielded quicker mineralization due to the additional •OH formed between added Fe²⁺ and electrogenerated H₂O₂. The PEF process was the most powerful since it led to total mineralization by the combined oxidative action of hydroxyl radicals and UVA irradiation. The PX decay agreed with a pseudo-first-order kinetics in EO-H₂O₂, whereas in EF and PEF, it obeyed a much faster pseudo-first-order kinetics followed by a much slower one, which are related to the oxidation of its Fe(II) and Fe(III) complexes, respectively. EO-H₂O₂ showed similar oxidation ability within the pH range 3.0–9.0. The effect of current density and Fe²⁺ and substrate contents on the performance of the EF process was examined. Two primary aromatic products were identified by LC-MS during PX degradation.

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