Uranyl ion adsorption kinetics and equilibrium on TBP-impregnated styrene-divinylbenzene resin with varying cross-linking degree

Tributyl phosphate (TBP)-impregnated styrene-divinylbenzene (STY-DVB)-SiO2 composite resins with controlled cross-linking degree (CL = 34, 56, 68, and 90%) were evaluated for U(VI) uptake in acidic media (5 M HNO3 and 9 M HCl) using a feed containing U, Th, Sr, Ag, and Cs. Selectivity tests showed dominant U(VI) adsorption, with negligible uptake of Sr and Cs and only trace Ag; Th exhibited moderate adsorption in HNO3. Kinetic profiles (1–240 min) were analyzed by pseudo-first-order and pseudo-second-order models, and PSO provided the better fit within the linearized analysis used here. The intermediate CL resin (CL = 56%) showed the fastest uptake. Apparent equilibrium isotherms (0.1–10 mg L−1) were well described by both linearized Langmuir and Freundlich models; Langmuir RL values (0–1) indicated favorable uptake. Overall, the results indicate that CL strongly influences the accessibility and uptake rate of TBP-containing domains under the present conditions.