Selective Anchoring by Surface Sulfur Species Coupled with Rapid Interface Electron Transfer for Ultrahigh Capacity Extraction of Uranium from Seawater

Improving the adsorption selectivity, enhancing the extraction capacity, and ensuring the structural stability of the adsorbent are the key to realize the high efficiency recovery of uranium. In this work, we utilized the strong Lewis acid–base interaction between S^2– and U(VI)O₂²⁺ coupling rapid electron transfer at the MnS/U(VI)O₂²⁺ solid–liquid interface to achieve excellent selectivity, high adsorption capacity, and rapid extraction of uranium. The as-synthesized MnS adsorbent exhibited an ultrahigh uranium extraction capacity (2457.05 mg g^–1) and a rapid rate constant (K = 9.11 × 10^–4 g h^–1 mg^–1) in seawater with 100.7 ppm of UO₂(NO₃)₂ electrolyte. The kinetic simulation reveals that this adsorption process is a chemical adsorption process and conforms to a pseudo-second-order kinetic model, indicating electron transfer at the MnS/U(VI)O₂²⁺ solid–liquid interface. The relevant (quasi) in situ spectroscopic characterization and theoretical calculation results further revealed that the outstanding uranium extraction property of MnS could be attributed to the highly selective UO₂²⁺ adsorption of MnS with lower adsorption energy as a result of the strong interaction between S^2– and UO₂²⁺ and the rapid mass transfer and interface electron transfer from S^2– and low-valent Mn(II) to U(VI)O₂²⁺.