Biguanide-functionalized magnetic nanoparticles for rapid and efficient removal of free fatty acids from edible Oils

A novel magnetically recoverable adsorbent was developed for rapid removal of free fatty acids (FFA) from edible oils as an alternative to conventional alkali refining. Silica-coated iron oxide nanoparticles functionalized with biguanide groups (Fe2O4@SiO2@Met) were synthesized and characterized (FT-IR, SEM, XRD, and VSM) and evaluated for FFA adsorption via batch optimization, kinetics, isotherms, real sunflower oil validation, and regeneration studies. The adsorbent achieved >97% oleic acid removal within 20 min (20 mg/10 mL, 900 ppm), with pseudo-second-order kinetics and fitted the Langmuir isotherm model (maximum capacity of 440.8 mg·g−1). The adsorbent was regenerated with 95% efficiency using ethanol-NaOH over multiple cycles and magnetically separable in <30 s (20 emu·g−1). In real-sample testing, 93.1% FFA removal was achieved from commercial sunflower oil. In comparison, amine-functionalized mesoporous silica has been reported to achieve 90% removal from olive oil. Although alkaline neutralization achieves similarly high efficiency, our method requires only 20 min (vs. 60 min) and avoids major drawbacks such as neutral oil loss and wastewater treatment challenges. Fe2O4@SiO2@Met offered a rapid, high-capacity, reusable and environmentally friendlier alternative to conventional FFA removal, with potential to reduce oil loss and waste in edible oil refining.