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

研究了以液化二甲醚（DME）为萃取剂的溶剂萃取法对河流沉积物中多氯联苯（PCBs）和二恶英的去除效果。溶剂萃取法去除有机污染物和水的效率很高。在常温下，可在中等压力（0.6-0.8 MPa）下进行。萃取剂可以从萃取物中回收并在此过程中重复使用。首先，对连续处理和批量处理的特征提取进行了比较。我们发现，与前者相比，后者的水提取效率相当低，尽管两者的多氯联苯提取效率都很高。其次，我们估计提取后回收的二甲醚的数量。结果表明，DME的回收率为98.6% ~102.2%。回收二甲醚的萃取效率与纯二甲醚相似。第三，考察了Fenton反应处理提取液中pcb最佳分解速率的最佳条件。在反应时间为120 min的条件下，在30mM:1000mM的浓度下，4次加入Fe^<2+>:H_2O_2试剂，pcb几乎100%被分解。最后，对该工艺进行了LCCO_2分析。评价结果为526.3kg-CO_2/mgTEQ（分解- dxns），表明该工艺比其他工艺更合适。

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.