Aminomethylpyridine isomers functionalized cellulose microspheres for TcO₄^-/ReO₄^- uptake: Structure-properties...

Technetium-99 (⁹⁹Tc) is a long-lived radioactive nuclide that poses great threat to environment, hence selective removal of ⁹⁹Tc from aquatic system is always an issue. Aminomethylpyridine (AMP) equipped with pyridine and amino, is a promising receptor for TcO₄^- and its surrogate ReO₄^-, thus it is of interest to explore and understand the structure-properties relationship of ReO₄^- adsorption related to n-AMP structure that differ in amino methyl position. In this work, three n-AMP functionalized cellulose microspheres (n-AMPR, n = 2, 3, 4) were synthesized and employed for TcO₄^-/ReO₄^- uptake. The effect of aminomethyl position on adsorption properties of n-AMPR for ReO₄^- were investigated and compared. Adsorption kinetics and adsorption isotherm showed that adsorption speed and adsorption capacity were in order of 3-AMPR > 2-AMPR > 4-AMPR. DFT calculation verified that the adsorption of ReO₄^- by n-AMPR was attributed to electrostatic interaction and hydrogen bonding interaction, the order of adsorption abilities of n-AMPR was due to that steric effect and hydrogen bond collaborated in stabilizing n-AMPR-ReO₄^- complexes. The column experiments demonstrated that 3-AMPR can be selectively remove ReO₄^- from simulated groundwater. More importantly, ⁹⁹Tc column experiments showed that 3-AMPR had a better ability for actual radioactive TcO₄^-.