Synergistic Hydrophilic Modification of PVDF Membranes Via Catechol-Based Multicomponent Assembly for Efficient Oily Wastewater Remediation.

To overcome the limitations of polyvinylidene fluoride (PVDF) membranes in oily wastewater treatment, this study proposes an innovative oxidation-chelation synergistic modification strategy. Catechol (CA) was used as a hydrophilic backbone, 3-aminopropyltriethoxysilane (KH550) as a cross-linker, sodium periodate (SP) as an oxidation accelerator and Fe3+ as a chelation enhancer to achieve hydrophilic modification of the PVDF membrane through synergistic oxidative cross-linking and metal chelation. The modified membrane exhibits a uniform micro‑nanoparticle surface structure, imparting superhydrophilicity (water contact angle ≈ 0°) and underwater superoleophobicity (oil contact angle up to 160°). It demonstrates excellent separation performance, with a permeation flux of 25 902 L·m-2·h-1·bar-1 and an oil rejection rate of 99.37% for oil-in-water emulsions. The key innovation lies in the synergistic oxidation-chelation mechanism, allowing for rapid film formation while ensuring robust interfacial adhesion. After 180 days of immersion in acidic, alkaline, and saline environments, the membrane retained its structural integrity and underwater anti-oil performance, effectively overcoming the long-standing issue of coating delamination in complex media. The key innovation lies in the synergy between SP-induced oxidation and Fe3+ chelation, which facilitates the rapid and robust formation of coatings, representing a significant mechanistic advancement over single-component modifications.