Enhanced Adsorption Performance for ReO₄–/⁹⁹TcO₄– Using Amino-Functionalized Cellulose Microspheres with Halogen Microregulation

There is a critical need to develop cost-effective and efficient adsorption materials for the removal of technetium-99 (99Tc) from contaminated water sources. This research presents the synthesis of amino-modified cellulose microspheres (CM-APTS) through the addition of 3-amino-propyl triethoxysilane (APTS) to regenerated cellulose microspheres (CM), followed by a subsequent reaction with ethylene dibromide (EDB) to produce halogen-modified amino cellulose microspheres (CM-APTS-EDB). These are engineered for the effective absorption of ReO4–, serving as a chemical surrogate for TcO4–. By altering the amount of ethylene dibromide used, two variations of bromine-modified cellulose microspheres, CM-APTS-EDBs and CM-APTS-EDBe, are synthesized. Among these, CM-APTS-EDBe exhibits robust adsorption capabilities for ReO4– across a pH spectrum of 2.5–10, attaining a peak capacity of 281 mg·g–1, and demonstrates selective adsorption of ReO4– even in the presence of competing anions such as NO3–, Cl–, and SO42–. Characterization through X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) indicates that the adsorption mechanism predominantly involves interactions between ReO4– and N+, hydrogen bonding with amino hydrogen, and σ-hole-anion interactions between Re–O and C–Br. After eight adsorption–desorption cycles, CM-APTS-EDBe retains notable stability and reusability. Additionally, the material efficiently captures ReO4– from simulated Hanford Low Activity Waste (LAW) wastewater, achieving an adsorption efficiency of 77.26% at a solid–liquid ratio of 40 g·L–1. This investigation underlines the potential of halogenated regenerated cellulose microspheres in designing advanced adsorbents for the removal of radioactive pollutants like TcO4–/ReO4–, offering a strategy for environmental remediation efforts.