Abstract
Supercritical C02was used to extract orgamc rruxtures from soil-water slurries. The extent of extraction and the equilibrium distribution of the mixture and of the individual components were determined. A single stage batch vessel was used to perform the extractions, and analyses were performed using either total organic carbon (TOC) analysis or BPLC analysis. The total extraction for the three phase system of soil-water-CO2 was predicted from two phase experimental data and theoretical correlations. The extractions of a complex phenolic mixture were analyzed by TOC. The two phase extractions from water were successful in closing the mass balance and yielding distribution coefficients which compared well to values in the literature. The three phase experiments, however, consistently yielded mass balance closures over 100%. It was determined that the soil organic matter was being extracted by the supercritical C02, the water, and the phenolic mixture. A four component phenolic mixture was successfully extracted from two phase and three phase systems and analyzed by BPLC. For the three phase system experiments, the distribution between the SCF phase and the aqueous phase, Ki. increased as the water solubility of the components decreased. Ki also increased as pressure increased. The partition coefficient between the soil and the water, Kd, decreased as temperature increased and showed an inverse relationship to water solubility. Predictions from the two phase system of water-CO2 yielded values of Ki which compared well to those for the three phase, but were consistently low. It seems that both the additional contaminants and the soil organic matter are acting as entrainers to facilitate extraction. The predicted values of Kdwere significantly lower than those for the three phase, but because the model is more sensitive to Ki than Kd, the predicted percent extractions were reasonable. The three phase distribution for the extraction of a mixture of polynuclear aromatic hydrocarbons (PAHS) was predicted based on two phase experimental data for the system of soil-CO2 and an empirical correlation based on octanol-water partition coefficients. These predictions were reasonable; although, some uncertainty in the analysis exists.
Green, Lynda Ann (1994). Supercritical extraction of organic mixtures from soil-water slurries. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1994 -THESIS -G796.