High-performance self-cleaning piezoelectric membrane integrated with in-situ ultrasound for wastewater treatment

Porous membrane structures containing piezoelectric materials can generate ultrasound from within during filtration to prevent fouling. Here, we report a high-performance porous lead zirconate titanate (PZT) substrate obtained in a two-step sintering process. A PZT green body was firstly sintered to nearly full density and crushed to obtain powders with a large grain size of 2.5 μm. Pressing and sintering of that powder resulted in a structure with porosity of 22 %, pore size of 1 μm, permeance of 814 LMH/bar and ultrasound response at 210 kHz of 385 mV. Then, an Al₂O₃ microfiltration membrane was coated on the PZT substrate with average pore size of ∼100 nm, permeance of 220 LMH/bar, and ultrasound response of 320 mV. The MF membrane showed > 99.5 % rejection of oil from oil-in-water emulsions. With in-situ ultrasound generation, the stationary permeance was 48 % improvement as opposed to without for emulsions with 2000 ppm by weight.