Abstract
A new chelating resin (R-N resin) was prepared through the encapsulation of linear poly(octadecylvinyl-maleic anhydride) into a porous polyacrylate support (Amberlite XAD-7) with subsequent grafting of 2-aminomethylpyridine. Adsorption characteristics of the chelating resin for platinum group metals (Pd(II), Pt(IV), Rh(III)) were examined with respect to the adsorption rate and dependence on pH and temperature. The adsorption reaction of Pd(II) and Pt(IV) at pH 2 in the presence of Cl- ion (0.1 M) was exothermic, whereas that of Rh(III) was endothermic. Ion exchange reaction by electrostatic attraction between the protonated ligand with [PdCl4](2-) and [PtCl6](2-) is predominant for the adsorption of Pd(II) and Pt(IV) at pH 2.0. While Rh(III) was retained by a complex formation from pH 2.0 to pH 6.5, adsorption of Rh(III) was remarkably accelerated by microwave irradiation: more than 91% of Rh(III) was retained for 1 h, while it was less than 50% by conventional heating. Repeated use of resin after regeneration was also demonstrated.