Palladium nanoparticles dispersed on functionalized macadamia nutshell biomass for formic acid-mediated removal of chromium(VI) from aqueous solution

• Published in: The Science of the total environment 2020-11, Vol.743, p.140614-140614, Article 140614
• Main Authors: Moyo, Malvin, Modise, Sekomeng Johannes, Pakade, Vusumzi Emmanuel
• Format: Article
• Language: English
• Subjects: Chromium(VI); Formic acid; Macadamia nutshell; Palladium nanoparticles
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.140614

Driven by the need for sustainably sourced catalysts and the use of reaction systems that generate environmentally benign by-products, the present study aimed to deposit stable, dispersed palladium (Pd) nanoparticles on the modified surfaces of granular macadamia nutshell (MNS) biomass for catalytic reduction of hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)). Through wet impregnation with Pd(II) ions and subsequent hydrazine-mediated reduction to Pd(0), Pd nanoparticles were embedded in a scaffold of polyethyleneimine grafted on bleached MNS previously coated with a chemically bound layer of polyglycidyl methacrylate. Imagery from scanning electron microscopy showed the formation of different layers of the polymeric coating and dispersed palladium resulting from surface modification and palladium nanoparticle synthesis, respectively. X-ray diffraction analysis confirmed the formation of Pd on the modified MNS surface and suggested an estimated crystallite size of 5.0 nm. The supported nanoparticles exhibited catalytic activity in formic acid-mediated Cr(VI) reduction and showed promising stability with consecutive reuse. These findings set the stage for advanced studies into performance optimization. [Display omitted] •Pd nanoparticles can be prepared on ligand grafted macadamia nutshells surfaces.•Ligand grafting dually facilitates Pd nanoparticle stabilization and Cr(VI) adsorption.•The doped Pd nanoparticles catalyze the dehydrogenation of formic acid.•Cr(VI) reduction by adsorbed hydrogen occurs on the Pd nanoparticles surfaces.