Facile and rapid separation of oil from emulsions by hydrophobic and lipophilic Fe3O4/sawdust composites

A novel method is demonstrated for effective separation of surfactant-free oil-in-water emulsions via hydrophobic and lipophilic Fe 3 O 4 /sawdust composites (HFSCs) under magnetic stirring. The HFSCs were able to capture micron-sized oil droplets from the emulsion under electromagnetic stirring due to its adsorption, underwater lipophilicity and exceptional magnetic property. Surfactant-free oil-in-water emulsions, such as diesel, toluene and soybean, were separated less than 1.5   min. After being measured by a total organic carbon analyzer, the initial content of toluene was reduced by 97.6% in separated emulsion, demonstrating that the toluene was almost entirely removed from the emulsion. Furthermore, for water-in-oil emulsions, the oil is selectively allowed to pass through HFSCs-based composite membranes with initial flux of ∼1134   L   m −2   h −1 and oil purity of the filtrate more than 99.9%. Moreover, the HFSCs can be reused for emulsion separation at least 10 times with little reduction of water contact angles (WCAs) and initial fluxes. The purity of the toluene filtrate was no less than 97% in the last separation. Therefore, the cost-effective and easily-operated preparation, reusable and eco-friendly material and convenient and efficient emulsions separation methodology offer great technological promise in the field of wastewater treatment , cleanup of oil spills, and fuel purification .