Electrochemical activation of persulfate by Al-doped blue TiO2 nanotubes for the multipath degradation of atrazine

Abstract

The combination of electrolysis and persulfate activation (E/PDS) is a cost-effective method for the treatment of refractory organics. However, persulfate is difficult to be activated into radicals at the anode, resulting in insufficient electro-activation efficiency. Herein, Al doped blue TiO2 nanotube electrodes (Al-bTNT) were first employed as cost-effective anode materials to fully activate PDS to radicals. In E/PDS, the kinetic constant of atrazine removal by Al-bTNT (0.048 min−1) substantially outperformed the other anodes, including the blue TiO2 nanotube electrodes (bTNT) (0.024 min−1), Ti4O7 (0.02 min−1), and B doped diamond (BDD) anodes (0.023 min−1). The Al-bTNT-E/PDS exhibited a low energy consumption (EEO = 0.72 kWh m−3) and a high mineralization rate. Based on the results of electron paramagnetic resonance, quenching experiments, and probe experiments, we propose that atrazine degrades in the Al-bTNT-E/PDS system mainly via a novel radical pathway that involves both·OH and SO4·- and the generated SO4·- is responsible for the enhanced removal rate. The oxygen vacancies (VO) generated from interstitial Al may serve as the active sites to adsorb and dissociate the persulfate molecules based on extensive characterizations. The attempt at soil-washing wastewater disposal indicated the synergistic system possessed good potential for future practical application.