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.