Supercriticalfluidtechnology For Remediation Of Pcb/pah-Contaminated Soils/sediments

Key words: soil/sediments remediation technology, supercritical fluids, PCBs, PAHs A two-stage technology employing green solvents such as supercritical CO 2 (SC-CO 2 ) and supercritical water (SCW) for the extraction and destruction of polychlorinated biphenyls (PCBs)/polycyclic aromatic hydrocarbons (PAHs) from contaminated soils/sediments is proposed. Results of our laboratory and benchscale investigations indicate that SC-CO 2 modified with 5% methanol, is an effective solvent and conditions have been defined to achieve sub 5 ppm in 45-60 minutes for 99.8% removal. Comprehensive data on PCB/PAH solubilities in SC-CO 2 /MeOH, partition equilibria, and desorbtion provide a solid basis to develop models regarding the extraction of these pollutants from solid matrices. Further, the supercritical water oxidation (SCWO) stage, coupled to the extraction process with three possible configurations, would provide clean effluent materials. The ultimate products of the proposed technology are mainly clean soil/sediments and inorganic species such as H 2 O, CO 2 , and small amounts of chlorides. Our SCWO studies indicate that 5245 ppm Aroclor 1248 in methanol-simulated soil extract solutions can be oxidized to 99.95% conversion in less than one minute at 550C. An economic analysis based on three possible configurations of the technological process indicates that the expected cost of $198-318 per m of soil processed is economically competitive