Controlled Formation of Hematite—Magnetite Nanoparticles by a Biosynthesis Method and Its Photocatalytic Removal Potential Against Methyl Orange Dye

It is presented a green synthesis method to obtain hematite (or magnetite) as a function of the concentration of Coffea arabica L extract mixed with a single iron salt precursor. The crystal structure, microstructural and phase formation of the iron oxide nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, Mössbauer spectroscopy and DC magnetometry. The particle sizes of the obtained nanoparticles are of the order of 5 nm. Optical properties were studied with UV–Vis spectroscopy from which a band gap energy of E g = 3.09 eV for hematite and E g = 3.23 eV for magnetite were deduced. The photocatalytic activity of the synthesized nanoparticles was tested by degradation of methyl orange dye under UV radiation, showing their potential application in wastewater treatment.