Thermosensitive Microgels-Decorated Magnetic Graphene Oxides for Specific Recognition and Adsorption of Pb(II) from...

Herein, we report a novel type of smart graphene oxide nanocomposites (MGO@PNB) with excellent magnetism and high thermosensitive ion-recognition selectivity of lead ions (Pb²⁺). The MGO@PNB are fabricated by immobilizing superparamagnetic Fe₃O₄ nanoparticles (NPs) and poly(N-isopropylacrylamide-co-benzo-18-crown-6 acrylamide) thermosensitive microgels (PNB) onto graphene oxide (GO) nanosheets using a simple one-step solvothermal method and mussel-inspired polydopamine chemistry. The PNB are composed of cross-linked poly(N-isopropylacrylamide) (PNIPAM) chains with numerous appended 18-crown-6 units. The 18-crown-6 units serve as hosts that can selectively recognize and capture Pb²⁺ from aqueous solution, and the PNIPAM chains act as a microenvironmental actuator for the inclusion constants of 18-crown-6/Pb²⁺ host-guest complexes. The loaded Fe₃O₄ NPs endow the MGO@PNB with convenient magnetic separability. The fabricated MGO@PNB demonstrate remarkably high ion-recognition selectivity of Pb²⁺ among the coexisting metal ions because of the formation of stable 18-crown-6/Pb²⁺ inclusion complexes. Most interestingly, the MGO@PNB show excellent thermosensitive adsorption ability toward Pb²⁺ due to the incorporation of PNIPAM functional chains on the GO. Further thermodynamic studies indicate that the adsorption of Pb²⁺ onto the MGO@PNB is a spontaneous and endothermic process. The adsorption kinetics and isotherm data can be well described by the pseudo-second-order kinetic model and the Langmuir isotherm model, respectively. Most importantly, the Pb²⁺-loaded MGO@PNB can be more easily regenerated by alternatively washing with hot/cold water than the commonly used regeneration methods. Such multifunctional graphene oxide nanocomposites could be used for specific recognition and removal of Pb²⁺ from water environment.