Engineering Mass-Transfer-Optimized Lamellar Structures for Enhanced Uranium Extraction From Seawater

Efficient uranium extraction from seawater (UES) offers a potential strategy to alleviate the growing pressure on terrestrial uranium resources and support sustainable nuclear energy development. Notably, polyamidoxime (PAO)-based adsorbents have emerged as promising candidates for UES application due to their high hydrophilicity and multi-site coordination capability. Herein, monolithic aerogels composed of PAO and hydroxyapatite nanowires (HAPNWs), abbreviated as PAOHNs, with optimized mass transfer efficiency were synthesized via a directional freeze casting process. Depending on the PAO-to-HAPNWs mass ratio, the aerogel morphology exhibited distinct evolution from a continuous porous network structure (PAOHNs-1) to a vertically aligned lamellar structure (PAOHNs-3), which facilitates improved diffusion pathways and efficient adsorption of uranyl ions. Based on COMSOL Multiphysics simulations, key structural parameters such as pore structure, channel size, and the Langmuir constants were systematically optimized, thereby bridging material innovation with computational modeling to guide the rational design of high-performance UES adsorbents. Although PAOHNs-1 possessed higher specific surface area and pore volume, PAOHNs-3 exhibited a higher overall adsorption rate toward uranyl ions. After 20 days of cyclic filtration in 100 L of natural seawater, PAOHNs-3 achieved the uranium extraction capacity of 12.5 mg g^-1, which highlights its potential for practical deployment and long-term uranium recovery in complex marine environments.