ABSTRACTAluminosilicates are one of the major class of species controlling the
volume of radioactive high-level waste that will be produced from future
remediation at Hanford site. Here we present studies of the phases and
structures of aluminosilicates as a function of sludge composition using
X-ray powder diffraction, solid state 27Al and 29Si
NMR, and Raman spectroscopy. The results show that the content of
NaNO3 in solution has significant effects on the nature of the
insoluble aluminosilicate phases produced. It was found that regardless of
the initial Si:Al ratio, nitrate cancrinite was the main phase formed in the
solution with pH of 13.5 and 5 MNaNO3. However, at lower
NaNO3 concentration with initial Si:Al ratios of 1.1, 2.2, and
11.0 in the solutions, a range of aluminosilicate zeolites was produced with
Si: Al ratios of 1.1, 1.3, and 1.5, respectively. Lowering the solution pH
appears to promote the formation of amorphous aluminosilicates. The results
presented here are important for the prediction of the solubility and
dissolution rate of Al in tank wastes.