Voltage-regulated ion sieving assisted by a highly cationic polymer network achieves selective 99TcO4− adsorption with record-high capacity

The high salt content and strong ionic competition in real wastewater and contaminated fluids often result in subpar selectivity and capacity for 99TcO4− on adsorbents. To address this challenge, we present a voltage-regulated ion sieving (VRIS) technique aimed at enhancing the selectivity and capacity for nuclide ions on adsorption materials. As an example, a highly cationic polymer network (Cl@HCPN) is synthesized as anode material for the VRIS technique, designed for the efficient capture of 99TcO4−. Cl@HCPN is prepared through quaternization of 1,4-diazabicyclo[2.2.2]octane with 1,3,5-Tris(bromomethyl)benzene and possesses a high content of anion exchange sites (7.64 mmol g−1). The material achieves rapid capture (within 30 s) and a record-high adsorption capacity (1752.1 mg g−1) for ReO4− (a nonradioactive surrogate of 99TcO4−), as well as superior adsorption kinetics and efficiency for 99TcO4−. The VRIS employs precisely regulated step positive voltages to achieve meticulous control over ion adsorption and desorption on Cl@HCPN, enabling cyclic ions sieving and enhancing selectivity for ReO4− by ∼50 %. The VRIS technique is anticipated to emerge as a universal method for improving the selectivity of adsorption materials for 99TcO4−, with potential applications in efficient adsorption and separation of other pollutant ions.