Sol-gel matrices for the separation of uranyl and other heavy metals

The development of simple, cheap, and efficient techniques for separating and recycling heavy metal cations, including radioactive species, motivated this study of the feasibility of using sol-gel matrices as ion exchange columns. The goal of this study was to elucidate the selectivity of a sol-gel matrix for heavy and radionuclide cations to separate heavy metal cations from a solution of heavy and radioactive metals. The effect of ligand incorporation in the host matrix on adsorption capacity was determined by measuring matrix capacities to adsorb the metal cations. Analysis of the results obtained by DFT calculations showed a good fit to the relative capacity values measured by the wet experiments, and they lead to some important conclusions: The higher capacity observed for the matrices prepared at pH 13 for all of the studied cations, indicates that this method could be applicable in the durable entrapment of cations. The sol-gel matrices were found to be selective for the uranyl, and the entrapment of nitrilotris(methylene)]tris(phosphonic acid) in these matrices increases the capacity and selectivity for cerium and accelerates the cation adsorption process (the measured capacities are 25.3 μmol/g sol-gel and 28.4 μmol/g sol-gel for the TMOS-Blank and TMOS-NTPH, respectively). Since uranyl and chromium reached their maximum capacities at different times, which also differed from the times for the other cations, these matrices can be used as ion exchange columns for the separation of chromium and uranyl from other cations and for the recycling of heavy and radioactive metals.