Green synthesis of Pd/walnut shell nanocomposite using Equisetum arvense L. leaf extract and its application for the reduction of 4-nitrophenol and organic dyes in a very short time.

Palladium nanoparticles (PdNPs) have been immobilized on the surface of walnut shell powder using Equisetum arvense L. leaf extract as reducing and stabilizing agents in this work. FT-IR spectroscopy, UV-Vis spectroscopy, photoluminescence spectroscopy, X-ray diffraction (XRD) pattern, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM) have been used in the characterization of the nanocomposites thus prepared. High catalytic activity was shown by these nanocomposites in the reduction of different dyes. The PdNPs' diameter on the walnut shell was predominantly found within the 5-12-nm range. The advantages of these catalysts include facile and clean synthesis, simple preparation procedure, excellent properties, alterable supports, and low cost, which make them applicable in reduction of 4-nitrophenol (4-NP), Congo red (CR), methylene blue (MB), and rhodamine B (RhB) in the presence of aqueous NaBH4 at room temperature. Pd/walnut shell nanocomposites were highly active catalysts for reduction of these dyes. Moreover, Pd/walnut shell nanocomposite can be recovered and recycled seven times without any appreciable loss of catalytic activity. Graphical abstract Waste walnut shell as a natural valuable resource support for green synthesis of Pd/walnut shell nanocomposite using Equisetum arvense L. leaf extract and its application for the reduction of 4-nitrophenol and organic dyes in a very short time.