OICC Press Iranian Journal of Catalysis 2345-4865 9 1 2024 02 25 Green synthesis of Ag/Fe3O4/ZrO2 nanocomposite using aqueous Centaurea cyanus flower extract and its catalytic application for reduction of organic pollutants EN Akbar Rostami-Vartooni Department of Chemistry, Faculty of Science, University of Qom, Qom 3716146611, Iran. 0000-0002-5395-9966 Abolfazl Moradi-Saadatmand Department of Chemistry, Faculty of Science, University of Qom, Qom 3716146611, Iran. Mojtaba Bagherzadeh Reactor and Nuclear Safety School, Nuclear Science and Technology Research Institute, 81465-1589, Isfahan, Iran Mohammad Mahdavi Department of Chemistry, Malek-ashtar University of Technology, Shahin-shahr P.O. Box 83145/115, Iran. Journal Article 2024 02 25 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.