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 ≤ pH ≤ 8.9 and concentration 0.21–26.9 mmol Re/L and 5 × 10−3 – 5 × 10−2 mmol 99Tc/L. The highest uptake for both elements (R d ≈ 104 mL/g) was observed for solutions with pH ≤ 4 and CNaCl ≤ 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.