Facile Fabrication of Cyclodextrin-Modified Magnetic Particles for Effective Demulsification from Various Types of...

Effective oil-water phase separation from various emulsions, especially those stabilized by surfactant, is of great importance. Although superhydrophobic and superoleophilic materials have attracted considerable attention in recent years, they are incapable of directly separating all types of oil-water mixtures. To separate various types of emulsions, one of the most important features of particles is that they can be dispersed in the continuous phase for delivery and target dispersed phases. In this study, cyclodextrin-modified magnetic composite particles (M-CDs) have been fabricated for this goal, based on their special interfacial activity and response to an external magnetic field. Though M-CDs are hydrophilic, the intelligent M-CDs can switch from hydrophilicity to hydrophobicity spontaneously, due to the formation of CD-oil inclusion complexes (ICs) at the oil-water interface. Physicochemical characterization reveals that M-CDs can adsorb at the oil-water interface and locate at the droplet surface as an effective Pickering emulsifier. By applying an external magnetic field, M-CDs are removed from the droplet surface and a rapid oil-water phase separation occurs. Our M-CDs can demulsify, for the first time, surfactant-free or surfactant-stabilized oil-in-water (O/W) and water-in-oil (W/O) emulsions directly, with high separation efficiency. Furthermore, the recycled MNPs still show high demulsification efficiency. In view of the sustainability of cyclodextrin and effective recycling ability of MNPs, M-CDs provides a new opportunity to develop an environmentally friendly interfacial material for practical applications in wastewater treatment.