Removal of PCDDs/DFs and PCBs from contaminated sediment using liquefied dimethyl ether as an extractant.

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We investigated whether polychlorinated biphenyls (PCBs) and dioxins could be removed from river sediment by solvent extraction using liquefied dimethyl ether (DME) as the extractant. The efficiency of solvent extraction for the removal of organic contaminants and water is quite high. Moreover, it can be carried out under moderate pressure (0.6-0.8 MPa) at room temperature. The extractant can be recovered from the extract and reused in this process.Firstly, we compared extracting characteristics of the continuous processing with that of batch processing. We found that the latter showed quite low water extraction efficiency in comparison with the former although PCBs extraction showed high efficiency in both. Secondly, we estimated the amount of DME that was recovered after extraction. We found that 98.6～102.2% of DME could be recovered. The extraction efficiency of the recovered DME is similar to that of the pure DME.Thirdly, we investigated the optimum condition for reaching best PCBs decomposition rate in Fenton's reaction to treat extract. Under the condition of 120 min reaction time and the four times addition of Fe^<2+>:H_2O_2 reagent at the concentration of 30mM:1000mM, almost 100% of PCBs was discomposed.Finally, we carried out the LCCO_2 analysis of this process. It was evaluated 526.3kg-CO_2/mgTEQ(decomposed-DXNs) and we concluded that this process is more suitable than the other processes.