Rhenium(VII) and technetium(VII) separation from aqueous solutions using a polyethylenimine-epichlorohydrin resin

The ReO₄^- and ⁹⁹TcO₄^- removal from aqueous solutions using a polyethylenimine-epichlorohydrin resin was investigated in absence and presence of background electrolyte (0.01 and 0.50 M NaCl). Re(VII) and Tc(VII) sorption isotherms were obtained for solutions with 2.3 B pH B 8.9 and concentration 0.21-26.9 mmol Re/L and 5 9 10^-3 - 5 x 9 10^-2 mmol ⁹⁹Tc/L. The highest uptake for both elements (R_d ∼ 10⁴ mL/g) was observed for solutions with pH ≤ 4 and C_NaCl B 0.01 M, hinting towards the existence of protonated groups contributing to the sorption of anions under acidic conditions and to the competition of Cl^-. The sorption data were modeled using the Langmuir and Freundlich equations. (author)