Highly efficient immobilization of uranium(VI) from aqueous solution by phosphonate-functionalized dendritic fibrous nanosilica (DFNS)

A novel phosphonate assisted fabrication dendritic fibrous nanosilica (DFNS)-based adsorbing material was successfully synthesis via organic modification with 3-aminopropyltriethoxysilane (KH550), epichlorohydrin (ECH) and phytic acid (PA) on the grounds of hard-soft-acid-base theory, in which organic phosphorous can be applied for efficient chelating uranium(VI) (U(VI)). The adsorption properties can be evaluated by setting a series parameters (pH, adsorbent dose, contact time, initial U(VI) concentration). It is clear that uranium as a "hard" lewis acid can easily form chelating bond with "hard" donor-ligands so that as-papered PA-DFNS has an excellent adsorption capacity (qm = 1106 mg g-1, 298.15 K), which exhibits a 163% increment compared with that of original DNFS under the same condition. In the meantime, the adsorption equilibrium time of PA-DNFS (t = 60 min) was shortened by 33% compared with that of pristine DNFS. Besides, the PA-DFNS exhibited good removal efficiency and stability under the 0.1 M HNO3 after 6 cycles, extending the application of PA-DFNS in the field of adsorption.