Salophen Sol-Gel Hybrid Sorbent Material for the Sensing and Sequestration of Actinyl Ions
Radioactive materials require special management and considerations. From a non-proliferation standpoint, their presence may indicate a nuclear security threat. Whether they are elements to be recovered from used nuclear fuel or contaminants to be removed from a body of water, the separation, concentration and identification of these materials is imperative for nuclear energy and security to succeed. Functionalized sorbent materials can be designed for enhanced sequestration of radioactive materials present in these aqueous environments. The salophen Schiff base has demonstrated potential as a selective actinyl ion (U, Np, Pu) chelator during solvent extraction. Incorporating this ligand into a solid sorbent material may increase its potential by facilitating the concentration and containment of radioactive ions into a compact solid. In this work, a salophen Schiff-base sorbent material if formed through silica xerogel sol-gel co-condensation polymerization and a (triethoxysilyl)propyl modification to one side of the salophen for covalent inclusion. The nonsymmetrical ligand is therefore tethered to the xerogel at only one point, forming an actinyl ion-selective hybrid sorbent material. This sorbent has shown superior uptake to its symmetrically tethered counterpart as well as a commercial material for the removal of uranium from aqueous solutions. In addition, the sorbent can be further adapted utilizing a phenylene bridged polysilsesquioxane sol-gel polymerization. This sorbent material demonstrates potential to lessen the effects of ionizing radiation on the Schiff base ligand for the reprocessing of used nuclear fuel or the containment of high level radioactive waste. In the interest of nuclear security and owing to the chromophoric shift of the salophen ligand as it binds actinyl ions, the nonsymmetrical ligand can also be utilized as a solid optical thin film sensor for the detection of aqueous uranyl ions.