Fabrication of Ag nanoparticles supported on amino-functionalized peeled-watermelon structured silica-coated nano-Fe3O4 with enhanced catalytic activity for reduction of 4-nitrophenol

In this work, novel silver nanoparticles supported on amino-functionalized peeled-watermelon-like silica-coated magnetic catalysts (Fe3O4@SiO2-NH2-Ag) were successfully synthesized for the catalytic reduction of 4-nitrophenol (4-NP) in wastewater. The Fe3O4 nanoparticles were further coated with silica forming a structure similar to peeled watermelon to improve the stability of magnetic Fe3O4 and inhibit their aggregation. Furthermore, surface modification of Fe3O4@SiO2 particles with amino groups was used for the immobilization of silver nanoparticles. As a result, the Fe3O4@SiO2-NH2-Ag (10%) exhibits excellent catalytic activity to reduce 4-NP, which obtained the first-best reaction rate constant of 0.026 s−1. Besides, the Fe3O4@SiO2-NH2-Ag could be easily recovered under an external magnetic field and was reused for 25 catalytic cycles without a significant decline in catalytic activity. The related catalytic mechanism of the reaction was discussed. Overall, the excellent magnetic recyclable nature and immortal catalytic activity make Fe3O4@SiO2-NH2-Ag a very promising material for practical use.