Interaction Analysis between Gravity-Driven Ceramic Membrane and Smaller Organic Matter: Implications for Retention and Fouling Mechanism in Ultralow Pressure-Driven Filtration System.

Gravity-driven membranes (GDM) generally achieve high retention performance in filtration of organic matter with a smaller size than the membrane pore, yet the in-depth mechanism remains unclear. Thorough analysis of the retention mechanism is crucial for optimizing GDM properties and improving GDM filtration performance. The performance and interaction mechanism of gravity-driven ceramic membrane (GDCM) filtrating smaller organic matter (SOM) were systematically studied. Rejection rate grew noticeably for like-charged foulant, whereas it only grew slightly for opposite-charged foulant as operation height decreased. Flux declined more seriously at lower operation height, probably due to heavier cake fouling caused by the rejected foulant. Interactions of ceramic membrane-SOM were analyzed through extended Derjaguin-Landau-Verwey-Overbeek theory (XDLVO) and hydrodynamic permeation drag (PD). Among van der Waals (LW), acid-base (AB), and electrostatic (EL) forces in XDLVO, EL played a significant role on GDCM filtrating SOM, and altering membrane electrostatic property could greatly influence SOM filtration. Furthermore, the rising PD force largely weakened the EL dominant zone with operation height increasing, while barely influencing the LW and AB dominant zones. Therefore, the weakened EL-dominant repulsive zone caused less rejection of like-charged foulant with operation height increasing. Fe2O3- and MnO2-modified membranes further validated the comprehensive influence of LW, AB, EL, and PD interactions on GDCM filtration. The possible "trade-off" of pore blocking-cake fouling with operation height decreasing demonstrated potential enhancement for both rejection and antifouling performance by electrically modified membrane under ultralow pressure. This study provides insight on membrane selection/preparation/modification and performance control of ultralow pressure-driven filtration.

Peracetic acid integrated catalytic ceramic membrane filtration for enhanced membrane fouling control: Performance evaluation and mechanism analysis.

Endowing ceramic membrane (CM) catalytic reactivity can enhance membrane fouling control in the aid of in situ oxidation process. Peracetic acid (PAA) oxidant holds great prospect to integrate with CM for membrane fouling control, owing to the prominent advantages of high oxidation efficacy and easy activation. Herein, this study, for the first time, presented a PAA/CM catalytic filtration system achieving highly-efficient protein fouling alleviation. A FeOCl functionalized CM (FeOCl-CM) was synthesized, possessing high hydrophilicity, low surface roughness, and highly-efficient activation towards PAA oxidation. Using bovine serum albumin (BSA) as the model protein foulant, the PAA/FeOCl-CM catalytic filtration notably alleviated fouling occurring in both membrane pores and surface, and halved the flux reduction degree as compared with the conventional CM filtration. The PAA/FeOCl-CM catalytic oxidation allows quick and complete disintegration of BSA particles, via the breakage of the amide I and II bands and the ring opening of the aromatic amino acids (e.g., Tryptophan, Tyrosine). In-depth investigation revealed that the in situ generated •OH and 1O2 were the key reactive species towards BSA degradation during catalytic filtration, while the organic radical oxidation and the direct electron transfer pathway from BSA to PAA via FeOCl-CM played minor roles. Overall, our findings highlight a new PAA/CM catalytic filtration strategy for achieving highly-efficient membrane fouling control and provide an understanding of the integrated PAA catalytic oxidation - membrane filtration behaviors.