Dual-Responsive Pickering Emulsions Stabilized by Amphiphilic Fe3O4 Nanoparticle for Dye Contaminant Removal

This study presented the redox and magnetically responsive water-in-oil (W/O) Pickering emulsions stabilized by amphiphilic Fe3O4 nanoparticles. The magnetic nanoparticles synthesized by a conventional solvothermal method were further modified and characterized by Fourier-transform infrared (FT-IR), scanning electron microscopy (SEM) and energy-dispersive system (EDS). The results showed that Fe3O4 nanoparticles modified by 3-pyridyl-5-ferrocenyl-2-pyrazoline (PFP) showed strong interfacial activity, which could be used to emulsify toluene and water to prepare stable water-in-toluene emulsions. Moreover, due to the good redox properties of PFP, the emulsions could be switched between stable/unstable by adding trace amounts of oxidant and reducing agents alternately. At the same time, the emulsion droplets could be moved by applying magnetic field due to the superparamagnetic nature of Fe3O4 nanoparticles. Moreover, based on the electrostatic interaction, pi-pi stacking and solubilization effect, the obtained Pickering emulsions could be used as an excellent extraction system for dye molecules Congo red with extraction efficiency up to 97%. In addition, the droplets of the emulsion could be reused by simple washing, which provided a new method for dye contaminant removal.