Enhanced Versatility in Thorium Removal: Mesoporous Silica-Coated Magnetic Nanoparticles Functionalized by...

In order to promote the sustainable development of nuclear energy through thorium (Th(IV)) recycling, we synthesized SiO₂-coated magnetic functional nanocomposites (SiO₂@Fe₃O₄) that were modified with 2,9-diamide-1,10-phenanthroline (DAPhen) to serve as an adsorbent for Th(IV) removal. SiO₂@Fe₃O₄-DAPhen showed effective Th(IV) adsorption in both weakly and strongly acidic solutions. Owing to its porous structure that facilitated rapid adsorption kinetics, equilibrium was achieved within 5 and 0.5 min at pH 3 and 1 mol L^-1 HNO₃, respectively. In weakly acidic solutions, Th(IV) primarily formed chemical coordination bonds with DAPhen groups, while in strongly acidic solutions, the dominant interaction was electrostatic attraction. Density functional theory (DFT) calculations indicated that electrostatic attraction was weaker compared to chemical coordination, resulting in reduced diffusion resistance and consequently faster adsorption rates in strongly acidic solutions. Furthermore, SiO₂@Fe₃O₄-DAPhen exhibited a high adsorption capacity for Th(IV); it removed Th(IV) through chelation and electrostatic attraction at pH 3 and 1 mol L^-1 HNO₃, with maximum adsorption capacities of 833.3 and 1465.7 mg g^-1, respectively. SiO₂@Fe₃O₄-DAPhen also demonstrated excellent tolerance to salinity, adsorption selectivity, and radiation resistance, thereby highlighting its practical potential for Th(IV) removal in diverse contaminated water sources. Hence, SiO₂@Fe₃O₄-DAPhen represents a promising choice for the rapid and efficient removal of Th(IV).