Research on the Properties of Wasteforms after Direct Involvement of Uranium-Containing Silica Gel in Glass Network Formation.

ABSTRACT

Uranium-containing silica gel (UCSG) is a secondary waste generated during the advanced treatment of nuclear wastewater. In order to reduce the growing storage pressure for UCSG, from the perspective of building a borosilicate glass network, UCSG was used to replace SiO2 in the glass-cured formula to directly achieve the immobilization of UCSG. SEM-EDS results showed that uranium was uniformly distributed in the matrix, and the maximum solid solubility of UCSG (two components silica gel and uranyl ions) in the formula was as high as 55 wt %. At the same time, TG-MS proved that silica gel lost OH groups (down about 4.61 wt %) and formed Si-O-Si bond by condensation. FT-IR and XPS proved a change in the number of Si-O-Si bond, and new Si-O-B and Si-O-Al bond appeared on the spectrum. This was evidence that silica gel could self-involved participate in the construction of glass networks. EPR analysis obtained the changes in the coordination environment of U atom, the U atom decreased spin electrons number in the glass than in uranyl crystals. The glass also has good physical properties (hardness 6.51 ± 0.23 GPa; density 2.3977 ± 0.0056 g/cm3) and chemical durability (normalized leaching rate LRU = 2.34 × 10-4 ± 2.05 × 10-6 g·m2·days-1 after 42 days), this research provided tactics for simple treatment of uranium-containing silica gel in one step.