Reduction of Hexavalent Chromium Using Recyclable Pt/Pd Nanoparticles Immobilized on Procyanidin-Grafted Eggshell Membrane

Efficient immobilization of catalytic active metal nanoparticles into porous supporting materials is of important scientific interest in practice. We report on the fabrication of novel bionanocomposites, comprising a three-dimensional porous eggshell membrane (ESM) bioscaffold decorated with catalytic active metal (Pt, Pd) nanoparticles, to reduce highly toxic Cr(VI). Procyanidin (Pro), a natural plant polyphenol with abundant phenolic hydroxyls, was first covalently grafted on the ESM fiber surface to provide stable binding sites for chelating metal precursors. Highly dispersed Pt and Pd nanoparticles with small size were facilely generated and stably immobilized onto the surface of ESM followed by NaBH4 reduction. These metal nanoparticle-incorporating ESM composites were active heterogeneous catalysts for the reduction of toxic Cr(VI) to Cr(III) by employing formic acid as the reducing agent. Notably, it is easy to recover and recycle the catalysts, revealing the good stabilization of procyanidin-grafted ESM for nanoparticles.