Smart and recyclable admicelle-coated Fe3O4 nanoparticles for treating oily wastewater

Abstract

Oily wastewater has become a serious environmental problem, which calls for various smart materials and sustainable separation technologies. Herein, a kind of recyclable and environment friendly SCA@Fe3O4 nanoparticle was designed and in situ fabricated by coating a self-crosslinked admicelle (SCA) of sodium conjugated linoleate on the nano-Fe3O4 surface via self-assembly and self-crosslink strategies, and its triple responses to pH/CO2−N2/magnetism were characterized. Liquid paraffin−in−water Pickering emulsions stabilized by SCA@Fe3O4 nanoparticle can be magnetically separated by an external magnetic field, and switched reversibly between unstable and stable states by altering pH or bubbling CO2−N2 alternately. Therefore, we applied SCA@Fe3O4 nanoparticle as the smart multipurpose materials (emulsifier/magnetic separating carrier/demulsifier) in an oil–water separation simulation. A formulated dilute oil−water dispersion (5 wt%) was concentrated into a high internal phase emulsion (Voil = 75%) by simply stirring with SCA@Fe3O4 as the emulsifier, and the magnetic Pickering emulsion was magnetically separated following broken by CO2-bubbling to turn SCA@Fe3O4 into the demulsifier, finally the CO2-hypnotized SCA@Fe3O4 nanoparticle was regenerated by N2-bubbling and used as the aroused emulsifier repeatedly. Moreover, liquid paraffin was recovered with excellent recyclability more than 95.5% in all four cycles. Therefore, SCA@Fe3O4 nanoparticle can be circularly employed as high separation material, which makes oily wastewater treatment more sustainable and higher efficient.