Photoelectrocatalytic degradation of carbendazim using titanium‑tungsten oxide in a pilot-scale flow reactor

Carbendazim is a persistent emerging pollutant that poses environmental and health risks due to its toxicity and resistance to conventional wastewater treatment. This study evaluates the photoelectrocatalytic performance of nanotubular oxides grown on Ti and Ti W alloy in a pilot-scale flow reactor for CBZ degradation. Ti-xW alloys (x = 0.5, 2.5, and 5.0 wt% W) were synthesized in an electric arc furnace, rolled, and anodized to form nanotubular oxide layers (52 cm 2 ) of different thicknesses (1–6 μm). Titanium plates of similar dimensions were prepared for comparison. The reproducibility of the photoanode synthesis was compromised by anodization solutions aged over 95 h. Nanotubes exceeding 4 μm in length exhibited negligible dependence on the thermal crystallization treatment duration. Under optimized anodization conditions, uniform nanotubular oxide layers with a length of 5.5 (±0.5) μm and an inner diameter of ≈ 70 (±15) nm were obtained across the entire large-area substrate. Flow rates above 30 L h −1 reduced degradation efficiency due to shorter pollutant residence time and possible accumulation of reaction intermediates or by-products on the catalyst surface. NT/Ti-5 W electrode showed superior PEC performance due to Ti-O-W heterojunctions and surface states, enhancing charge separation. CBZ degradation in rinsing water revealed toxic intermediates affecting Aspergillus flavus , but toxicity reduced after 150 min, when the growth curve starts to increase, reaching the control one (without CBZ) in 180 min. The treated water costs were approximately 63% and 50% lower than those for photocatalysis and photoelectrocatalysis using only TiO 2 nanotubes, respectively. • Synthesis of Ti-O-W nanotubes of large area (≈50 cm 2 ) by anodization process • Photoelectrocatalytic degradation of commercial carbendazim (CBZ) in the flow reactor • Toxicity evaluation and by-product formation during PEC treatment of commercial CBZ • Removal of the toxicity of commercial CBZ and by-products after 180 min of PEC