Superhydrophobic supported liquid membrane contactor for enhanced selective recovery of long-chain fatty acids from food-waste-derived microalgae

In this study, we systematically investigated the selective recovery of long-chain fatty acids (LCFAs) from food waste condensate (FWC) following microalgae cultivation, using polyvinylidene fluoride (PVDF) membranes modified with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) and impregnated with 5 or 10 wt% trioctylphosphine oxide (TOPO) extractant. Among the tested configurations, the PVDF@P_TES@TOPO(10) membrane exhibited the best performance, particularly for stearic acid (C₁₈:0) recovery, achieving a recovery efficiency of 98.7 ± 1.6 % and a mass flux of 23.3 ± 1.1 g/(m²·d). The overall LCFA selectivity, defined as the total mass flux ratio of LCFAs (C₁₄–C₁₈) to short-chain fatty acids (SCFAs, C₂–C₄), markedly increased from 0.08 for the virgin PVDF membrane to 3.14 for the PVDF@P_TES@TOPO(10) membrane, a 39-fold enhancement. Real-time monitoring using optical coherence tomography (OCT) revealed pronounced differences in wetting behavior between membranes. The virgin PVDF membrane underwent severe wetting, structural collapse, and exhibited high surface energy, whereas the PVDF@P_TES@TOPO(10) membrane maintained its structural integrity and hydrophobicity throughout 30 days of continuous operation. The enhanced anti-wetting and anti-fouling performance is attributed to the synergistic effects of fluorosilane surface modification and TOPO impregnation, which together create a robust chemical and physical barrier against aqueous permeation and foulant deposition. This engineered membrane platform offers a highly efficient and sustainable solution for the selective recovery of high-value biochemicals from complex aqueous matrices, while simultaneously mitigating the persistent challenges of wetting and fouling inherent to liquid–liquid extraction processes.