Quaternary Ammonium‐Containing Polyelectrolyte Brush Particles for Removal of Perrhenate Anion From Water: Effect of N ‐Substituents

Abstract Radioactive pertechnetate (TcO 4 − ) from the nuclear fuel cycle presents a severe risk to the environment due to its large solubility in water and non‐complexing nature. By utilizing the chaotropic properties of TcO 4 − and its nonradioactive surrogate perrhenate (ReO 4 − ) and the principle of chaotropic interactions, a series of quaternary ammonium‐containing polyelectrolyte brush‐grafted silica particles are designed and applied to remove ReO 4 − from water. These cationic hairy particles (HPs) are synthesized by surface‐initiated atom transfer radical polymerization of 2‐( N , N ‐dimethylamino)ethyl methacrylate and subsequent quaternization with various halogen compounds. Dynamic light scattering (DLS) studies showed that the HPs with sufficiently long N ‐alkyl and N ‐benzyl substituents underwent sharp size reduction transitions in water when titrated with a KReO 4 solution, indicating strong chaotropic interactions between the brushes and ReO 4 − . All the HPs exhibited fast adsorption kinetics; the HPs with longer N ‐alkyl and N ‐benzyl substituents showed higher capabilities of removing ReO 4 − than those with shorter N ‐alkyls. Moreover, the brush particles with longer N ‐substituents displayed a significantly stronger ability in selective adsorption of ReO 4 − than the particles with shorter N ‐substituents in the presence of competing anions, such as F − , Cl − , NO 3 − , and SO 4 2− . This work opens a new avenue to design high‐performance adsorbent materials for TcO 4 − and ReO 4 − .