OICC Press Journal of Nanostructure in Chemistry 2193-8865 12 1 (February 2022) 2021 04 16 Green synthesis of Fe (II, III) oxides nanoparticles in the subcritical water medium and evaluation of their catalytic performance in the oxidation of metoprolol 10.1007/s40097-021-00403-y EN Rasiha Nefise Mutlu Department of Chemistry, Faculty of Arts and Science, Mersin University, Çiftlikköy Campus, Mersin, 33343, TR Erdal Yabalak Department of Chemistry, Faculty of Arts and Science, Mersin University, Çiftlikköy Campus, Mersin, 33343, TR Department of Nanotechnology and Advanced Materials, Mersin University, Mersin, 33343, TR Ayşe Nur Acar Department of Mechanical Engineering, Faculty of Ceyhan Engineering, Cukurova University, Adana, 01950, TR A. Murat Gizir Department of Chemistry, Faculty of Arts and Science, Mersin University, Çiftlikköy Campus, Mersin, 33343, TR Department of Nanotechnology and Advanced Materials, Mersin University, Mersin, 33343, TR Journal Article 2021 04 16 Abstract In this study, iron (II, III) oxides were synthesized under room condition (303 K) and eco-friendly subcritical water medium (SCW) (383 and 403 K, 30 bar) and their catalytic activities were investigated. Characterization of synthesized catalysts was performed using the scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses and their magnetic properties were enlightened. The catalyst synthesized in room condition was a mixture of iron (III) oxide, hematite, and magnetite (100–800 nm), while it was magnetite with nano sizes (7–14 nm) which was synthesized in subcritical conditions. Besides, the ferromagnetic characteristics of the catalysts synthesized in subcritical conditions were higher than those synthesized in the room conditions. The nano-catalyst was used in the oxidation of metoprolol. Optimization of oxidation parameters was achieved using the surface response method (RSM). 4.84% and 48.64% of metoprolol removal were achieved when the temperature (353 K) and UV irradiation (254 nm) were separately applied, respectively, while the catalyst increased the removal efficiency to 93.41%. Graphic abstract