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 mu m Pressing and sintering of that powder resulted in a structure with porosity of 22 %, pore size of 1 mu m, 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 similar to 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.