Leaching of saltstone

A modified IAEA leach test was used to evaluate the relative performance of potential saltstone formulations. The effects of sample size and leach rates for specific ions were determined. Leaching mechanisms were determined for NO3-, NO2-, SO4-2, Na+, Ca+2, and Si. NO2-, NO3-, Na+, and SO4-2 are listed in order of decreasing leach rates. These ions exhibited high initial leach rates which decreased rapidly with time. High initial rates were attributed to surface wash off and diffusion. Within 10 days leach rates stabilized and can be explained by diffusion. Effective diffusivities for nitrite, nitrate, sodium, and sulfate were calculated from the leaching data. They are 6.4 x 10-10, 4.1 x 10-10, 3.2 x 10-10, and 0.9 x 10-10 cm2/sec, respectively. Negative leach rates were measured for Ca+2 and Si in some formulations. This was attributed to precipitation of CaCO3 and hydrated calcium silicate phases on the surfaces of the samples. 4 refs., 11 figs., 1 tab