Thermosensitive poly(N-isopropylacrylamide)-grafted magnetic nanoparticles for efficient treatment of emulsified oily wastewater

A class of thermosensitive and reusable magnetic nanoparticles (MNPs) was developed for removing emulsified oil droplets from aqueous media. Magnetic iron oxide (MIO) nanoparticles were prepared with a coprecipitation method, followed by coating with silica layer and further modification with γ-methacryloxypropyl triisopropoxidesilane (MPS). Poly( N -isopropylacrylamide) (PNIPAM) molecular chains were then anchored onto the surfaces of MNPs via a “grafting through” reaction. The efficiency of synthetic MNPs for treating emulsified oily wastewater was evaluated as a function of dosage, pH, temperature and reusability. PNIPAM-grafted MNPs exhibited high demulsification efficiency at lower temperature, while decreased dramatically when the temperature exceeded the lower critical solution temperature (LCST) of PNIPAM (∼33 °C); moreover, MNPs could be facilely regenerated by rinsing with hot water and could be reused up to 7 cycles. The results indicated that PNIPAM-grafted MNPs could potentially be a new promising and environmentally friendly approach for effectively treating emulsified oil in wastewater.