Experimental design approach for the optimization of supercritical fluid extraction of pyralene and aldrin in soil matrix

Characterisation and remediation of contaminated soils are crucial issues in environmental control. Extraction of pollutants with supercritical fluids is a competitive and viable technique on a laboratory scale and is of great interest for the treatment of contaminated soils in the future. Extraction by supercritical fluids (CO2 or modified CO2) has been carried out on a standard soil (EUROSOIL 1), artificially polluted by organochloride compounds, i.e. pyralene and aldrin. A commercialised extraction apparatus has been used in order to determine the optimal operating conditions for quantitative extraction. A systematic extraction study has been developed and interpreted according to the optimal design method. Several parameters influencing extraction have been identified and studied: pressure, temperature, extraction flow-rate, type of extracting fluid, water content of soil. The percentage recovery has been determined for each experiment. Linear regression of the resulting data has allowed the construction of a recovery response surface, which indicates that high recovery can be obtained over a wide range of extraction conditions.