Polybenzimidazole resin-based new chelating agents. Uranyl and ferric ion selectivity of resins with anchored dimethylglyoxime

Abstract

Microporous polybenzimidazole (PBI) of 250–500 μm spherical bead size from Celanese has been reacted with epichlorohydrin and sodium hydroxide and the resulting epoxidized product (EPBI) further reacted with dimethylglyoxime (DMG) using a quaternary ammonium salt as the phase transfer catalyst, to obtain a new sorbent EPBI (DMG) having high sorption capacity for UO 2 2+ (172 mg U/g dry weight of resin) and for Fe 3+ (188 mg Fe/g dry wt of resin). The sorption of UO 2 2+ is maximum in weakly acidic or neutral solutions (pH 5–7), falling sharply both at lower and higher pH, while the uptake of Fe 3+, sorbed mainly as anionic complexes, is relatively unaffected by pH in HCl and H 2SO 4 media. Among the transition metal ions tested, Co 2+ has the highest binding constant for sorption on the resin, followed by Fe 3+, Cu 2+, Ni 2+, Mn 2+ and UO 2 2+, in that order, although the sorption capacities of all these metal ions, except Fe 3+ and UO 2 2+, are rather poor. The sorbed UO 2 2+ is readily stripped by 1 N HCl and 10% (w/v) ammonium carbonate solution while removal of the sorbed Fe 3+ complexes is considerably more difficult, requiring strong phosphoric acid solution for effective stripping.