Selective Uranium Adsorption of Phosphorylated Silica Gel With High Capacity and Ultrafast Kinetics

ABSTRACT A simple and scalable ultrasonic‐acid‐assisted grafting method was applied to synthesize phosphorylated silica gel adsorbent (SGB‐P2), which significantly enhanced the adsorption capacity and selectivity for uranium. The obtained SGB‐P2 exhibited a maximum uranium adsorption capacity of 400 mg·g −1 greatly surpassing those of the unmodified sample (50.54 mg·g −1 ), and achieved ultrafast adsorption equilibrium within just 1 min and retained over 80% efficiency after five adsorption–desorption cycles. The adsorption process followed the pseudo‐second‐order kinetics and Langmuir isotherm models, indicating chemisorption‐dominated monolayer adsorption. Combined spectroscopic analyses and density functional theory (DFT) calculations revealed that the coordination between uranium and the phosphate groups (P─O/P═O) constitutes the primary adsorption mechanism. This study demonstrates great potential for practical application of silica gel in the treatment of uranium‐contaminated wastewater.