Electrochemical Oxidation of Atrazine and Clothianidin on Bi-doped SnO2–TinO2n–1 Electrocatalytic Reactive Electrochemical Membranes

This research focused on improving mineralization rates during the advanced electrochemical oxidation treatment of agricultural water contaminants. For the first time, bismuth-doped tin oxide (BDTO) catalysts were deposited on Magnéli phase (Ti _nO_{2 n-1}, n = 4-6) reactive electrochemical membranes (REMs). Terephthalic acid (TA) was used as a OH^• probe, whereas atrazine (ATZ) and clothianidin (CDN) were chosen as model agricultural water contaminants. The BDTO-deposited REMs (REM/BDTO) showed higher compound removal than the REM, due to enhanced OH^• production. At 3.5 V/SHE, complete mineralization of TA, ATZ, and CDN was achieved for the REM/BDTO upon a single pass in the reactor (residence time ∼3.6 s). Energy consumption for REM/BDTO was as much as 31-fold lower than the REM, with minimal values per log removal of <0.53 kWh m^-3 for TA (3.5 V/SHE), <0.42 kWh m^-3 for ATZ (3.0 V/SHE), and 0.83 kWh m^-3 for CDN (3.0 V/SHE). Density functional theory simulations provided potential dependent activation energy profiles for ATZ, CDN, and various oxidation products. Efficient mass transfer and a reaction mechanism involving direct electron transfer and reaction with OH^• were responsible for the rapid and complete mineralization of ATZ and CDN at very short residence times.