Cyclic Fouling and Flux Recovery in a Piezoelectrically Actuated Polytetrafluoroethylene Membrane Module

Membrane fouling limits pressure-driven filtration by increasing hydraulic resistance and cleaning demand. Here, an external lead zirconate titanate actuator (PZT) was coupled to a passive polytetrafluoroethylene (PTFE) microfiltration membrane to examine cyclic fouling and short-term flux recovery. The primary pressure series comprised chronological sodium-alginate filtration stages at 6-30 kPa using a nominal 5 μm membrane from two membrane histories; additional actuation-duration, dosing, imaging, and interfacial analyses were treated as separate evidence streams. Across 31 adjacent activation events, endpoint flux increased in 28 events and decreased in three, with a median change of 1351 L/m²h. These events were repeated observations within the two histories and did not constitute independent replicates or a matched sham control. Segment-wise Hermia fitting retained 39 decline windows, for which cake filtration gave the minimum Akaike information criterion (AIC) in 34 windows (87.2%); however, the selected model was recovered in fewer than 80% of bootstrap resamples for 15 windows, underscoring that the fits are empirical descriptors rather than unique mechanism identifiers. The measured real electrical input was about 1.5 W, whereas the estimated viscosity-related flux gain from the recorded temperature change was only 0.08-2.68%, indicating that bulk heating alone could not explain the observed recovery. Separate microscopy and extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) analyses were consistent with removal or redistribution of surface deposits and altered post-treatment attachment propensity. Overall, the data establish a reproducible within-history temporal association between actuator operation and flux recovery, while the absence of a matched sham experiment precludes attribution to a single mechanical, hydraulic, electrical, or pressure-transient pathway.