Electrochemical degradation of triazole fungicides in aqueous solution using TiO2-NTs/SnO2-Sb/PbO2 anode: Experimental and DFT studies

Abstract

Triazole fungicides (TFs) are toxic and bio-refractory contaminants widely spread in environment. This study investigated electrochemical degradation of TFs in aqueous solution at TiO2-NTs/SnO2-Sb/PbO2 anode with particular attention to the effect of molecular structure. Three TFs with triazole ring in one biologically treated water including tricyclazole (TC), 1H-1,2,4-triazole (Tz) and propiconazole (PPC) were selected as the target compounds. Results of bulk electrolysis showed that degradation of all TFs was fit to a pseudo first-order equation. The three compounds were degraded with the following sequence: PPC > TC> Tz in terms of their rates of oxidation. Quantum chemical calculation using the density function theory (DFT) method was combined with experimental results to describe the degradation sequence of TFs. Atom charge was calculated by DFT method and active sites of TFs were identified respectively. Analysis of intermediates by GC-MS and LC-(ESI)-MS/MS showed agreement with calculation results. In addition, the acute toxicity of TC and PPC treated solution significantly decreased after treatment by electrochemical oxidation.