Waste chicken eggshell as a natural valuable resource and environmentally benign support for biosynthesis of catalytically active Cu/eggshell, Fe3O4/eggshell and Cu/Fe3O4/eggshell nanocomposites

• Green synthesis of Cu/eggshell, Fe3O4/eggshell and Cu/Fe3O4/eggshell nanocomposites.
• Orchis mascula L. leaf extract act as a stabilizing and reducing agent.
• Catalytic reduction of 4-nitrophenol, Methyl orange, Congo red, Methylene blue and Rhodamine B.
• Catalytic activity of Cu/eggshell is significantly higher than Fe3O4/eggshell and Cu/Fe3O4/eggshell.
• The catalysts could be easily recovered and reused several times.

This paper is reported on the green synthesis of Cu/eggshell, Fe3O4/eggshell and Cu/Fe3O4/eggshell nanocomposites through an environmental and economical method using aqueous extract of the leaves of Orchis mascula L. without any stabilizer or surfactant. The nanocomposites showed high catalytic activity in the reduction of a variety of dyes and characterized by Fourier transform infrared spectroscopy (FT-IR), differential thermal and thermogravimetric (DTA-TGA) analysis, field emission scanning electron microscopy (FESEM) equipped with an energy dispersive spectroscopy (EDS), elemental mapping, X-ray diffraction analysis (XRD), Brunauer–Emmett–Teller (BET), vibrating sample magnetometer (VSM) and UV–vis spectroscopy. The possible mechanism leading to the formation of copper nanoparticles (NPs) is also suggested. The facile and clean synthesis, simple preparation procedure, excellent properties, alterable supports and low cost allow these catalysts to be used in reduction of 4-nitrophenol (4-NP), Methyl orange (MO), Congo red (CR), Methylene blue (MB) and Rhodamine B (RhB) in water at room temperature. The progress of the reaction was monitored using UV–vis spectroscopy. The catalysts could be easily removed from the reaction media by mild centrifugation or an external magnet and reused several times without any negative effect on the initial results.

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