Experimental evaluation of synthetic recyclable magnetic nanodemulsifier for desalting unit oily wastewater treatment

Oil–water emulsions pose significant environmental challenges due to their complex treatment requirements. Conventional chemical demulsifiers, while effective, often pose environmental risks and are non-recyclable, limiting their long-term viability. This study explores a sustainable alternative: a recyclable magnetic demulsifier based on graphene oxide nanocomposites coated with oleic acid (Fe₃O₄@OA@GO). The morphology, particle size, and structure of the demulsifier were analyzed using TEM, XRD, and TGA, while its functional groups were identified through FTIR spectroscopy. XRD analysis confirmed the cubic spinel structure of Fe₃O₄, with characteristic peaks at 2θ = 30.1°, 35.5°, 43.1°, 53.4°, 57.0°, and 62.6°. TGA revealed the thermal stability of Fe₃O₄, with weight loss corresponding to the decomposition of organic components (oleic acid and graphene oxide) and a stable residue at high temperatures. Adsorption characteristics of oil on the particles followed the Freundlich isotherm model, while the kinetics were described by the pseudo-second-order model. Structural analysis revealed a particle size of approximately 30 nm. Performance tests demonstrated that the demulsifier's structure, featuring functional groups such as C–OH, C=O, C–O, and Fe–O, promotes the aggregation of organic compounds within the emulsion, leading to destabilization. A dosage comparison indicated that 100 ppm of the demulsifier achieved optimal efficiency of over 90%. Higher dosages resulted in excessive accumulation of magnetic particles, reducing effectiveness. UV tests confirmed enhanced water clarity at this concentration. This study highlights the potential of Fe₃O₄@OA@GO as an eco-friendly, recyclable solution for treating oily wastewater in desalting units.