Photo-electrocatalytic oxidation of atrazine using sputtured deposited TiO2: WN photoanodes under UV/visible light

Abstract

Abstract Herein were report on the UV/visible light driven photo-electrocatalytic (PEC) degradation of Atrazine (ATZ) and its major degradation by-products (DEA, DIA, DEDIA and ATZ-OH) in synthetic and real agricultural surface waters. For this purpose, sub-stoichiometric TiO2-x, and tungsten-nitrogen codoped TiO2:WN photoanodes were prepared by means of a radio frequency magnetron sputtering (RF-MS) deposition process. The codoping’s objective was to shift the material’s optical absorption from the UV towards the visible light, while minimizing defect formation. This was achieved, and directly demonstrated via UV–vis transmittance spectra analysis. Tauc plot extrapolation was used to determine the values of the band gaps of the films. We found that the band gap of TiO2-x is 3.0 eV and narrows to reach 2.3 eV for TiO2:WN. TiO2-x photoanodes crystallised in a predominantly rutile phase, whereas codoped TiO2:WN photoanodes crystallised in a predominantly anatase phase. Prior to PEC oxidation, agricultural surface water (ASW) containing ATZ was first treated by coagulation using metal salts (FeCl3 and Al2(SO4)3, respectively) as to reduce turbidity and colloidal particles. Optimal jar tests conditions allowed 52.9% and 39.7% DOC removal with FeCl3 and Al2(SO4)3, respectively. Subsequently, our TiO2:WN driven PEC process was investigated for the removal of ATZ (100 μg L−1) from ASW. Degradation of ATZ was performed in a homebuilt 5 L reactor with degradation times reaching 300 min. The scavengers of oxidants (e.g. S O 4 2 - , H C O 3 - and C l - ) reacted with oxidants generated during PEC process (e.g. H O • , H O 2 • , and O 2 • - ), so that the efficiency of PEC in removing ATZ from ASW was reduced.