Preparation of hydrophilic PVDF membranes through in situ assembly of phytate-polyethyleneimine-Fe³⁺ for efficient separation of herbal volatile oil from oily water

In the realm of oil–water separation technologies, membrane-based separation emerges as an efficacious approach. Nevertheless, crafting a hydrophilic membrane capable of effectively segregating herbal volatile oil remains a formidable challenge. Our study introduces a facile in situ assembly strategy for fabricating a double-crosslinked composite coating comprising phytate (PA)-polyethyleneimine (PEI) polyelectrolyte complexes and PA-Fe³⁺ assemblies. The PA within the PA-PEI/Fe³⁺ coatings form a double cross-linking layer through interactions with amine groups and metal ions, thereby enhancing interfacial interactions and structural integrity of the membranes. Consequently, the resultant PVDF/PA-PEI/Fe³⁺ membranes exhibit improved coating stability, pronounced hydrophilicity, and exceptional antifouling capabilities, rendering them highly suitable for the separation of diverse herbal volatile oil-in-water emulsions. Furthermore, they possess the capability for reuse with an average retention ratio exceeding 90% and a pure water flux reaching up to 3200 L·m⁻²·h⁻¹. Additionally, they demonstrate long-term stability and resistance to corrosion. With a simplistic yet efficient preparation process, the PVDF/PA-PEI/Fe³⁺ membrane holds significant potential for the extraction of oils from herbal volatile oil-in-water emulsions.