Abstract
A tannin gel (TG), synthesized from condensed tannin molecules, has a remarkable ability to adsorb metal ions in aqueous solutions. In the present report, the author introduces his recent work on the amine-modification of the TG to improve the adsorbability for precious metal ions. The solid-state 13C-NMR measurements revealed that some hydroxy groups in the TG are substituted by amino groups through a simple ammonia treatment. The adsorption experiments for palladium, platinum, and rhodium ions, Pd(II), Pt(IV), and Rh(III), were conducted using the amine-modified tannin gel (ATG), and it was found that the adsorbability of the ATG for these precious metal ions is significantly higher than that of the TG.
