Predictive and Experimental Methods for the Choice of Cosolvent in the Supercritical Fluid Extraction of Pesticides

The extraction of pesticides from oils and other solids using supercritical fluids can be significantly improved through the use of cosolvents. The difficulty in predicting which cosolvents will produce the largest solubility enhancement with individual pesticides is due in part to the lack of physical and chemical data available for most pesticides. Solubility data for lindane in supercritical fluid CO2-cosolvent mixtures are reported at 313.1 K. These data have beeen correlated directly with the Peng-Robinson equation of state. In order to predict the effect of cosolvents on the solubility of lindane in supercritical CO2 the interactions between lindane and each cosolvent must be known. One technique, that has been successfully used to predict the vapour liquid equilibria of many binary systems, utilises relevant Henry's constant data to calculate interaction parameters for equations of state. This technique has been extended to ternary soild-supercritical fluid-cosolvent systems. Appropriate Henry's constant data describing the equilibrium between the pure cosolvents and lindane have been measured and subsequently used to predict the ternary system solubility data. These predicted data have been directly compared with the measured solubilty data.