Solubility of some solid triazine herbicides in supercritical carbon dioxide

Supercritical fluids can be applied for decontamination of soils and other solid materials containing residual pesticides. The solubility of solid s-triazine derivatives: ametryne, prometryne, atrazine and simazine in supercritical CO2 were measured by a static-analytic method in the pressure range from 100 to 300 bar at temperatures of 40, 60 and 80 degrees C. The solubilities of atrazine and simazine are lower (for atrazine from 0.5 x 10(-5) to 31.5 x 10(-5) and for simazine from 1.7 x 10(-5) to 19.4 x 10(-5) mole fraction at pressures between 100 and 290 bar), than solubilities of ametryn and prometryn (for ametryn from 0.46 x 10(-5) to 133.04 x 10(-5) and for prometryn from 3.06 x 10(-5) to 101.91 x 10(-5) mole fraction for the same pressure range) because of their greater polarity. The specific functional group in s-triazines change the polarity of the compound. Atrazine and simazine have different solubilities, which also reflects the dissimilarities in their chemical structure. An analogous fact is observed for the second group of compounds (ametryn and prometryn). The solubilities depends on the solvent density and therefore the experimental binary solid-fluid equilibrium data were correlated as a function of solvent density by two different models. (C) 1998 Elsevier Science B.V. All rights reserved.