Selective capture of radionuclides (U, Pu, Th, Am and Co) using functional nanoporous sorbents

This work evaluated sorbent materials created from nanoporous silica self-assembled with monolayer (SAMMS) of hydroxypyridinone derivatives (1,2-HOPO, 3,2-HOPO, 3,4-HOPO), acetamide phosphonate (Ac-Phos), glycine derivatives (IDAA, DE4A, ED3A), and thiol (SH) for capturing of actinides and transition metal cobalt. In filtered seawater doped with competing metals (Cr, Mn, Fe, Co, Cu, Zn, Se, Mo) at levels encountered in environmental or physiological samples, 3,4-HOPO-SAMMS was best at capturing uranium (U(VI)) from pH 2–8, Ac-Phos and 1,2-HOPO-SAMMS sorbents were best at pH < 2. 3,4-HOPO-SAMMS effectively captured thorium (Th(IV)) and plutonium (²³⁹Pu(IV)) from pH 2–8, and americium (²⁴¹Am(III)) from pH 5–8. Capturing cobalt (Co(II)) from filtered river water doped with competing metals (Cu, As, Ag, Cd, Hg, Tl, and Pb) was most effective from pH 5–8 with binding affinity ranged from IDAA > DE4A > ED3A > Ac-Phos > SH on SAMMS. Iminodiacetic acid (IDAA)-SAMMS was also outstanding at capturing Co(II) in ground and seawater. Within 5 min, over 99% of U(VI) and Co(II) in seawater was captured by 3,4-HOPO-SAMMS and IDAA-SAMMS, respectively. These nanoporous materials outperformed the commercially available cation sorbents in binding affinity and adsorption rate. They have great potential for water treatment and recovery of actinides and cobalt from complex matrices.