Synthesis and characterization of valonea tannin resin and its interaction with palladium (II), rhodium (III) chloro complexes

Abstract

Valonea tannin (TA) and formaldehyde condensation reaction was carried out under alkaline condition to prepare the valonea tannin–formaldehyde resol resin (TAR). Obtained resin was used as adsorbent for recovery of palladium (II) and rhodium (III) ions from chloride-containing solutions. This kind of recovery was very simple and useful for generating little secondary wastes. Interaction of adsorption also was investigated: Chloropalladium (II) species were reduced to Pd(0), while hydroxyl groups of TAR were oxidized during the adsorption. Proposed adsorption of the aquachlororhodium (III) species mostly takes place via ligand exchange mechanism. TAR, Rh-adsorbed TAR, and Pd-adsorbed TAR were characterized by scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction spectroscopy, and Fourier transform infrared–attenuated total reflection spectroscopy.