Encapsulation of Nitrate Salts Using Vinylmethylpolysiloxane

Abstract

The Department of Energy has an immediate need for multiple technologies to transport and dispose of low level mixed waste. Solidification/stabilization (S/S) processes offer one possible solution that encapsulates sludge and dry hazardous wastes in a low permeability solid form. The advantage of vinylmethylpolysiloxane over other organic solidification processes is its ability to cure at ambient temperature. This paper examined compressive strength, metal leaching, and void area measurements of vinylmethylpolysiloxane-encapsulated waste as a function of waste loading (28–48wt%) for three surrogate wastes having compositions similar to those found at national laboratories. Compressive strength was greater than 4,390 kPa for all but one sample (48 wt% waste load-High Chloride waste). Image analysis shows void area increases linearly with increasing waste load, attributed to an increasing total sample volume physically occupied by the waste. Leaching test results indicate metal specific behavior and waste composition effects on Toxicity Characteristic Leaching Procedure (TCLP) concentrations. Cadmium diffusion from the encapsulated waste is slow (leach index >10 at all waste loads). Cost comparison of vinylmethylpolysiloxane to cement shows that it could be an economical waste disposal alternative.