Bi0.5Na0.5TiO3 perovskite for visible-light and ultrasonic cavitation-driven piezo-photocatalysis for wastewater treatment

Abstract Piezo-photocatalysis has emerged as a promising AOP for wastewater treatment, harnessing the synergistic effect of converting mechanical and solar energy into chemical reactivity for oxidant synthesis. Bi 0.5 Na 0.5 TiO 3 (BNT) is a non-toxic perovskite semiconductor, capable of spontaneously polarizing (intrinsic piezo-ferroelectric properties) and generating electron–hole pairs under light. This study evaluates BNT for degrading methylene blue, by coupling ultrasonic cavitation (24 kHz) as mechanical stress for polarization and visible light for photocatalysis. High-purity rhombohedral-BNT microparticles ( E g = 2.9 eV) were synthesized via a simple, cost-effective sol–gel Pechini method. The combined piezo-photocatalytic process achieved 90% degradation within 1 h, significantly surpassing individual piezocatalysis (46%) and photocatalysis (44%). BNT coatings on titanium mesh (electron acceptor) enhanced charge separation and pollutant removal. This approach demonstrates the feasibility of integrating renewable and accessible energy sources, visible sunlight and ultrasonic cavitation, already applied in water treatment plants, into AOPs. Graphical Abstract