ABSTRACT
Understanding mechanistic pathways to radiolytic hydrogen generation by metal oxyhydroxide nanomaterials is challenging because of the difficulties of distinguishing key locations of OH bond scission, from structural interiors to hydroxylated surfaces to physi-sorbed water molecules. Here we exploited the interface-selectivity of vibrational sum frequency generation (VSFG) to isolate surface versus bulk hydroxyl groups for gibbsite and boehmite nanoplatelets before and after 60Co irradiation at dose levels of approximately 7.0 and 29.6 Mrad. While high-resolution microscopy revealed no effect on particle bulk and surface structures, VSFG results clearly indicated up to 83% and 94% radiation-induced surface OH bond scission for gibbsite and boehmite, respectively, a substantially higher proportion than observed for interior OH groups by IR and Raman spectroscopy. Electron paramagnetic spectroscopy revealed that the major radiolysis products bound in the mineral structures are trapped electrons, O, O2- and possibly F-centers in gibbsite, and H, O and O3- in boehmite, which persist on the time frame of several months. The entrapped radiolysis products appear to be highly stable, enduring re-hydration of particle surfaces, and likely reflect a permanent adjustment in the thermodynamic stabilities of these nanomaterials.
ABSTRACT
An improved synthesis of a 3,4 hydroxypyridinone (HOPO) functionalized mesoporous silica is described. Higher 3,4-HOPO monolayer ligand loadings have been achieved, resulting in better performance. Performance improvements were demonstrated with the capture of U(VI) from human blood, plasma and filtered river water.
ABSTRACT
The chloromethylation of activated carbon is described. Chloromethylation was found to produce a carbon derivative with a surface area of 1310 m(2)/g and no significant change in the pore structure. The product was found to contain ~1.5 mmole of -CH(2)Cl groups per g of material, similar to the functional density reported in the original Merrifield resin synthesis. Displacement of the benzylic chloride was achieved by treating this material with an excess of sodium thiosulfate in refluxing aqueous methanol. The resulting Bunte salt was then hydrolyzed by treatment with warm 3 M HCl to afford the corresponding thiol ("AC-CH(2)-SH") cleanly and in high yield. AC-CH(2)-SH was found to be an effective heavy metal sorbent, efficiently capturing Hg, Pb, Ag, and Cu. Sorption kinetics were rapid, with equilibrium achieved in less than 30 minutes.
