Green synthesis of Ag/Fe3O4/ZrO2 nanocomposite using aqueous Centaurea cyanus flower extract and its catalytic application for reduction of organic pollutants

In this work, at first, nano ZrO2 and Fe3O4/ZrO2 nanocomposite were prepared by sol-gel and co-precipitation methods, respectively. Then, Ag nanoparticles (Ag NPs) were mixed with themin environmentally friendly and mild conditions using C. cyanus flower extract as a reducing and stabilizing agent. The synthesized nanocomposites were characterized by FT-IR, XRD, FE-SEM, EDS, and VSM techniques. The experimental results confirmed formation of the Ag nanoparticles with the 30-90 nm diameter on the surface of supports at room temperature within a few minutes. After that, the catalytic activity of the prepared nanocomposites in reduction of 4-nitrophenol (4-NP) and methyl orange (MO) have been studied and our results showed that they have following sequence: Ag/ZrO2 > Ag/Fe3O4/ZrO2 > ZrO2 > ZrO2 (550 °C) > Fe3O4/ZrO2. Finally, the magnetically recoverable Ag/Fe3O4/ZrO2 nanocomposite could be reused three times without a considerable decrease in its catalytic activity. Observed results were presented here and the probable catalytic mechanism was discussed.