Piezoceramic membrane with built-in ultrasound for reactive oxygen species generation and synergistic vibration anti-fouling

Abstract

Piezoceramic membranes have emerged as a prominent solution for membrane fouling control. However, the prevalent use of toxic lead and limitations of vibration-based anti-fouling mechanism impede their wider adoption in water treatment. This study introduces a Mn/BaTiO₃ piezoceramic membrane, demonstrating a promising in-situ anti-fouling efficacy and mechanism insights. When applied to an Alternating Current at a resonant frequency of 20 V, 265 kHz, the membrane achieves optimal vibration, effectively mitigating various foulants such as high-concentration oil (2500 ppm, including real industrial oil wastewater), bacteria and different charged inorganic colloidal particles, showing advantages over other reported piezoceramic membranes. Importantly, our findings suggest that the built-in ultrasonic vibration of piezoceramic membranes can generate reactive oxygen species. This offers profound insights into the distinct anti-fouling processes for organic and inorganic wastewater, supplementing and unifying the traditional singular vibrational anti-fouling mechanism of piezoceramic membranes, and potentially propelling the development of piezoelectric catalytic membranes.

Fig. 1. Fabrication, characterization and anti-fouling mechanism insights of the Mn/BaTiO₃ piezoelectric membrane.

a Membrane fabrication process. b Anti-fouling mechanism insights. c–e ESEM images of the surface (with an optical image insert in (c) and g–i cross-section of the membrane. f STEM-HAADF image with EDS elemental mapping of Mn/BaTiO₃ grains, scale bar, 100 nm.

Fig. 2. Oil fouling control of the Mn/BaTiO₃ piezoelectric membranes.

a AC frequency variation (5–600 kHz, example at 10 V). b, c Time-based normalized membrane flux under different AC conditions for oil emulsion treatment. Comparative ESEM and the corresponding EDS elemental mapping images of oil-fouled Mn/BaTiO₃ piezoelectric membranes surface at 20 V, 265 kHz (d) and 0 V (e), scale bar: 5 μm.

Fig. 3. Membrane retention results.

Particle size distributions of the colored oil emulsion before (a, 2500 ppm) and after (b, c) Mn/BaTiO₃ piezoelectric membrane treatment (optical images of water samples, inset). FEEMs analysis of feed (d) and filtrates (e, f, filtration duration of 180 min) across different filtration processes.

Fig. 4. Effects of the Mn/BaTiO₃ piezoelectric membrane against different foulants.

a–c Normalized membrane flux trends with various AC conditions for typical membrane foulants. d ESEM images of foulant-impacted membranes at different AC voltages (265 kHz), scale bar, 5 μm, representative foulants are delineated with yellow dashed lines for clarity.

Fig. 5. Insights into the anti-fouling mechanism of Mn/BaTiO₃ piezoelectric membrane: synergistic effects of membrane built-in ultrasonic vibration and in-situ ROS generation.

a Elemental mapping of SiO₂ and Al₂O₃ on the surface of the Mn/BaTiO₃ membrane post-filtration. b Finite element simulations of membrane displacement at 20 V across different AC frequencies. c ROS detection during membrane processes, 20 V, 265 kHz. d Distinct contributions of ROS and membrane built-in piezoelectric ultrasonic vibration to anti-organic (oil) fouling. e The impact of ROS generated by Mn/BaTiO₃ piezoelectric membrane on anti-inorganic (near-neutral charge SiO₂ particles) fouling.