Magnetically separable h-Fe3O4@Au/polydopamine nanosphere with a hollow interior: A versatile candidate for nanocatalysis and metal ion adsorption

The organic pollutants and heavy metal ions are critical harmful substances in waste water because they destroy the ecological systems and lead diseases to animals and human beings. Unfortunately, the simultaneously remove of them in one system is still a challenge due to their different treating mechanism. Herein, a novel magnetic h-Fe3O4@Au/Polydopamine (Au/PDA) hybrid hollow nanosphere which can both absorb the potentially toxic U(VI) ions and catalyze the reduction of the 4-nitrophenol is reported. By using a simple in situ redox-oxidizing polymerization method, the h-Fe3O4 hollow nanosphere is well encapsulated by the Au/PDA hybrid shell to form the dual-functional magnetic hollow nanocomposites. Owing to the hollow interior, uniform and functional PDA coating, and high active Au nanocrystals, the final h-Fe3O4@Au/PDA hollow nanosphere possesses high potential in nanocatalysis, heavy metal ions adsorption, and drug delivery. Because of the PDA protection, the h-Fe3O4@Au/PDA nanosphere can even keep 90% activity after 7 cycling catalytic reactions on reduction of 4-nitrophenol. Similarly, the h-Fe3O4@Au/PDA exhibits a good adsorption effect for U(VI) in nuclear waste and its adsorption capability reaches to 82.9 mg·g−1 by 6 successive adsorption–desorption experiments. Due to the facile magnetic separation, the h-Fe3O4@Au/PDA nanosphere can be easily collected by applying an external magnetic field. In summary, such a multifunctional recyclable h-Fe3O4@Au/PDA nanosphere with green and facile synthesis, easy manipulation, efficient adsorption performance and good catalytic activity possesses broad application potential in treatment of coexisting toxic water pollution.