Highly selective uranium separation using sulfonic acid‑functionalized hierarchically porous zirconium phosphate: Modelling and mechanism study

The growing challenges of nuclear pollution necessitate the development of advanced sorption materials with high efficiency and improved selectivity. In this work, a hierarchical porous zirconium phosphate sorbent (H-ZrP) was synthesized via a facile self-assembly strategy, and its sulfonic acid-functionalized derivative (H-ZrP-SO₃H) was developed for selective U(VI) removal. Comprehensive characterization demonstrates that H-ZrP possesses a unique hierarchical pore architecture, high specific surface area, and excellent thermal stability. Batch experiments reveal that both materials exhibit exceptional U(VI) sorption capacities: 372.4 mg g⁻¹ for H-ZrP and 290.5 mg g⁻¹ for H-ZrP-SO₃H. Kinetic and isotherm analyses confirm chemisorption-dominated monolayer sorption, well-described by pseudo-second-order (R² > 0.99) and Langmuir models (R² > 0.98). H-ZrP-SO₃H achieves higher selectivity in V/U systems despite reduced porosity due to optimized surface charge interactions. H-ZrP and H-ZrP-SO₃H demonstrate outstanding reusability, retaining > 99 % removal efficiency after five sorption–desorption cycles with preserved structural integrity. Surface complexation modelling reveals that the sorption process is dominated by a multi-stage sorption mechanism: electrostatic attraction and surface complexation via oxygenated groups. In summary, this work presents highly efficient functionalized phosphate-based sorbents to regulate interfacial charge dynamics for enhanced U(VI) sorption.