Garlic-Extract-Functionalized Fe3O4 Magnetic Colloids as Building Blocks for Gel-like Emulsified-Oil Capture

Stable emulsified oil droplets are difficult to separate because of persistent interfacial films and colloidal stability. Garlic-extract-functionalized Fe3O4 magnetic colloids, operationally denoted Allicin@Fe3O4, were prepared by in situ coprecipitation as organic–inorganic building blocks for gel-like interfacial capture. The sample name identifies the allicin-containing garlic-extract route and does not imply that allicin was proven to be the predominant surface species. SEM, FTIR, and XRD supported deposition of an organic, sulfur/oxygen-containing surface layer and retention of crystalline Fe3O4, but these methods are not species-specific. The colloids removed more than 95% of emulsified oil within 20 min and reached an experimental equilibrium apparent uptake of approximately 380 mg·g−1. Tests across pH 3–11, 0–50 g·L−1 NaCl, 15–55 °C, and representative coexisting ions showed robust but condition-dependent removal. Removal remained above 90% after five reuse cycles and was approximately 84% after ten cycles. Calculations using allicin as a representative garlic organosulfur molecule suggest how polar sulfur/oxygen regions and allyl segments could favor oil–droplet anchoring and association; they do not establish the surface composition of the extract-derived coating. The capture behavior is consistent with transient, gel-like particle–droplet association coupled to magnetic recovery. These results connect bio-derived surface functionalization, gel-related colloidal structuring, and magnetic separation under the tested batch conditions.