Hibiscus Rosasinensis L. aqueous extract-assisted valorization of lignin: Preparation of magnetically reusable Pd NPs@Fe3O4-lignin for Cr(VI) reduction and Suzuki-Miyaura reaction in eco-friendly media.

Hibiscus Rosasinensis L. extract mediated biosynthesis of Pd nanoparticles (NPs) and their deposition on the magnetic calcium lignosulfonate (MCaLig), as a simple and eco-friendly process for the preparation of Pd NPs@Fe3O4-lignin, is reported. The Pd NPs@Fe3O4-lignin was characterized by TEM, XRD, EDS, FE-SEM, FT-IR, VSM, and UV-Vis. The magnetic NPs were employed as exceptional catalysts in the catalytic reduction of Cr(VI) and Suzuki-Miyaura reaction between PhB(OH)2 and substituted aryl halides in EtOH:H2O as well as under ligand free conditions in the presence of K2CO3 with satisfactory product yields. Regeneration of the Pd NPs@Fe3O4-lignin was carried out by a magnet after the preparation of biphenyls. Catalytic efficiency retention was achieved after seven cycles.