Role of driven approach on the piezoelectric ozonation processes: Comparing ultrasound with hydro-energy as driving forces

Abstract Driven approach is vital for evaluating degradation and energy efficiencies of piezocatalysis process. Thus, piezoelectric ozonation processes driven by hydraulic (HPE-O3) and ultrasonic (UPE-O3) forces were compared systematically, using BaTiO3 as piezoelectric material for ibuprofen (IBP) degradation. The synergy indexes of HPE-O3 and UPE-O3 processes were 4.51 and 5.78, respectively. Besides, UPE-O3 process (88.84%) achieved better mineralization efficiency than HPE-O3 process (68.80%) in 90 min. Nevertheless, the energy consumptions of HPE-O3 process was only 4.01‰ of UPE-O3 process. The formation rate and concentration of •OH (the dominant active species in both processes) in UPE-O3 process were 2–3 times higher than that in HPE-O3 process. Notably, piezoelectric potential and current density driven by ultrasound were approximately 47500-fold and 40-fold than those by hydro-energy, respectively. These led to the difference of •OH paths between HPE-O3 and UPE-O3 processes. Further analyses indicated that •OH was mainly generated by single-electron transfer without H2O2 generation in HPE-O3 process, whereas both single- and double-electron transfer (with H2O2 generation) contributed to the production of •OH in UPE-O3 process. This study revealed the mechanism of piezoelectric ozonation process with different driven approaches and may provide valuable reference for selection of driven approaches in piezocatalytic study and application.