Polybenzimidazole resin based new chelating agents uranyl ion selectivity of resins with immobilized glyoxal-bis-2-hydroxyanil and salicylaldehyde-ethylenediimine

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 glyoxal-bis-2-hydroxyanil (GHA) and salicylaldehyde-ethylenediimine (SED) at ordinary temperatures, using a quaternary ammonium salt as the phase-transfer catalyst. The resulting new sorbents EPBI(GHA) and EPBI(SED) have been compared with the base resin PBI and the conventional ion-exchange resins Dowex 50W-X8(H +) and Dowex 1-X8(SO 4 2−) in respect of uranyl sorption in sulfate system. In UO 2SO 4 solution at pH 4.7, the saturation capacities (mmol U/g dry wt. of resin) of the five resins, in the aforesaid order, are 1.03, 1.20, 2.79, 2.10 and 1.35, respectively. Both EPBI(GHA) and EPBI(SED), however, show greater sorption capacities than PBI at low substrate concentrations of uranium (< 60 mg U/L) due to their significantly higher binding constants than PBI. Both PBI and its derivatives EPBI(GHA) and EPBI(SED) have considerably greater salt tolerance than the Dowex resins. Thus, in the presence of twenty fold molar equivalents of sodium ions, the uranium selectivities of Dowex 50W-X8(H +) and Dowex 1-X8(SO 4 2−) are, respectively, 0.32 and 0.50 in NaCl solution and 0.15 and 0.87 in Na 2SO 4 solution. In comparison, PBI and its derivatives have selectivities of 1.0 in NaCl and 0.75–0.80 in Na 2SO 4, thus yielding greater uranium sorptions than the Dowex resins against a high salt background.