A self-cleaning piezoelectric PVDF membrane system for filtration of kaolin suspension

Exploring innovative membrane material is an important approach to mitigate membrane fouling. This study investigated a self-cleaning polyvinylidene fluoride (PVDF) piezoelectric membrane system which can vibrate at controlled frequencies, amplitudes and waveforms to mitigate membrane fouling. Among different PVDF films, the one of the highest content beta-phase PVDF was selected because of the greatest piezoelectric coefficient. The film was pin punched to 0.14 +/- 0.02 mm holes for filtration purpose. The characteristic peaks of vibration velocity and amplitude were identified by measurements of a Scanning Laser-Doppler vibrometer with tiered driving voltages. The piezoelectric membrane was tested in a dead-end filtration system fed with 0.5 g L-1 kaolin suspension of 907.7 nm Z-average diameter at a constant filtration pressure of 34.5 kPa. The results indicate vibration velocity is more important than amplitude to choose the vibration frequency in order to optimize membrane fouling control. The piezoelectric membrane with continued vibration driven by 24 V (peak-to-peak) and sine wave at the frequency of 1601 Hz (the peak of vibration velocity) yielded 87 +/- 3% higher permeate flux than control test, compared to 30 +/- 3% increase at the frequency of 664 Hz (the peak of vibration amplitude). However, the antifouling effect was not apparent with intermittent vibration, possibly due to interrupted processes of cleaning and fouling prevention. The mechanistic explanation of cleaning suggests lift force brought by hydraulic shearing is more important than inertial lift force of vibration.