Study of stabilization mechanism—PVDF/PA-PEI/Fe³⁺ membrane achieving efficient volatile oil separation

This study elucidates the stabilization mechanism underpinning the efficient and long-term separation of Traditional Chinese Medicine (TCM) volatile oils from oil-in-water emulsions by polyvinylidene fluoride/phytic acid-polyethyleneimine/Fe3 + (PVDF/PA-PEI/Fe3 + ) membranes. Through integrated molecular docking and Schneider's thermodynamic analysis, we demonstrate that the exceptional stability arises from a dual-crosslinked architecture: (1) High-affinity coordination bonds between phytic acid (PA) and Fe³⁺ (binding energy: −5.2 kcal/mol; ΔH m = 1.05 × 10⁻³ cal/mol) establish a robust framework resistant to chemical and thermal degradation, while (2) Fe³⁺-mediated interfacial bridging—achieved through lone-pair electron sharing with fluorine atoms in PVDF (Polyvinylidene Fluoride) and electrostatic interactions with polyethyleneimine (PEI)—synergistically suppresses delamination. Experimental validation demonstrates exceptional durability: Fourier-transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) analyses confirm retention of Fe³⁺-phosphate coordination bonds and pore structural integrity following 24-h exposures to pH extremes (3–11), 100% ethanol, 95°C thermal treatment, and 0.25 MPa pressure. The membrane sustains >95% oil retention capacity and stable steady-state permeate flux (≈2750 L·m –2 ·h –1 (LMH), 2750 LMH·bar –1 ) throughout the 60-day cyclic operation (8h of filtration per day, with the membrane immersed in the turmeric oil-in-water emulsion during off-operation hours and characterized every 7 days). The high flux is attributed to the synergistic effect of the large-pore PVDF substrate (Molecular weight cut-off (MWCO) of 200,000 Da) and the superhydrophilic PA-PEI/Fe 3+ coating, Tests were conducted on 4 cm-radius membraneswith an effective filtration area of 0.005024 m² under the conditions of Transmembrane pressure (TMP) of 0.1 MPa and 25±1°C.With corrosion resistance demonstrated by negligible flux variation (flux recovery ratio, (FRR) <100%) when treating aggressive turmeric oil emulsions. This study establishes a dual-anchoring strategy that effectively mitigates volatility-induced membrane corrosion, thereby positioning PVDF/PA-PEI/Fe³⁺ membranes as an industrially viable platform for sustainable extraction of Traditional Chinese Medicine (TCM) volatile components. Download: Download high-res image (438KB) Download: Download full-size image