Piezo-activation of peroxydisulfate by BaTiO3 for metronidazole removal in water

In this research, a new system was created using piezoelectric catalytic activation of peroxydisulfate (PDS) to eliminate organic contaminants from water. Barium titanate (BaTiO3) nanoparticles were employed as a representative piezoelectric catalyst to activate PDS under ultrasonic (US) conditions for the degradation of metronidazole (MNZ) in water. In the BaTiO3/PDS/US system, a degradation rate of up to 92% for MNZ was attained within 30 minutes, representing an increase of 76% and 80% compared to the BaTiO3/PDS/stirring system and PDS/US system, respectively. A significant synergistic effect was observed, with the reaction rate constant of BaTiO3/PDS/US being six times higher than the sum of the rates of the other two processes. The potential activation mechanism was postulated through analysis of reactive species, ESR measurements, and DFT calculations, suggesting that the accumulation of local charges on the surface of BaTiO3 disrupted the peroxide bond (O-O) in PDS, leading to the continuous generation of ·SO4-, which further converted into ·OH, ·O2-, and 1O2. Among these species, 1O2 played a major role in the degradation of MNZ. Overall, the findings suggest that BaTiO3 piezoelectricity can effectively trigger PDS to improve MNZ elimination, introducing new possibilities for utilizing piezoelectric catalysis in wastewater treatment.