Superhydrophilic, multi-level antifouling PVDF microfiltration membrane with ionically crosslinked “organic-inorganic” bridging in oily wastewater treatment

Polyvinylidene difluoride (PVDF) microfiltration membranes hold significant potential for oily wastewater treatment due to their exceptional mechanical and chemical stability. However, PVDF's inherent hydrophobicity leads to severe fouling, limiting its use in heavily contaminated waters, and particularly hindering continuous operation in pollutant-rich environments. Thus, modifying PVDF to establish robust hydrophilicity is urgently needed for sustainable, multifaceted antifouling purposes. Inspired by organic–inorganic bridges, we developed a phase-controlled strategy to fabricate an Al 3+ -crosslinked ionic polymer-PVDF membrane. This was achieved by integrating favorable bridging structures into the PVDF matrix. Specifically, 2-Acrylamido-2-methylpropanesulfonic acid (AMPS) and diethanolamine (DEA), polymerized in situ in the casting solution, undergo Al 3+ -OH and Al 3+ -SO 3 − coordination-driven crosslinking during the phase separation process. This process enabled simultaneous Al 3+ -polymer coordination, resulting in a stable organic–inorganic bridging network in the porous membrane. PVDF/P(AMPS-DEA)@Al 3+ exhibited superhydrophilicity (0° water contact angle in 20 s) and high pure water flux (2600 L·m −2 ·h −1 under 0.1 bar) at room temperature (25 °C). Additionally, the membranes demonstrated robust and sustained performance in separating oily wastewater (with mineral oil used as model foulant) (864 L·m −2 ·h −1 high flux and > 98.5 % oil rejection rate after three oil-water separation cycles). Lastly, PVDF/P(AMPS-DEA)@Al 3+ exhibited remarkable resistance to multiple types of biofouling, including bovine serum albumin (BSA) protein, B. Subtilis and E. Coli bacteria, and diatoms. This work introduces a novel organic–inorganic bridging strategy for PVDF modification, offering a robust approach toward scalable.