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

以液化二甲醚为萃取剂，研究了溶剂萃取法去除河流底泥中多氯联苯和二恶英的效果。溶剂萃取去除有机污染物和水的效率相当高。而且，它可以在室温下在中等压力（0.6- 0.8MPa）下进行。萃取剂可以从萃取液中回收并重复使用。本文首先比较了连续法和间歇法的萃取特性。我们发现，后者表现出相当低的水提取效率与前者相比，虽然多氯联苯提取表现出较高的效率，在这两个。其次，我们估计了提取后回收的DME的量。实验结果表明，二甲醚的回收率为98.6~102.2%。回收的二甲醚萃取效率与纯二甲醚相当。第三，研究了芬顿反应处理萃取液时达到最佳PCBs降解率的最佳条件。在反应时间为120 min，Fe^<2+>：H_2O_2试剂浓度为30 mM：1000 mM，分四次加入的条件下，PCBs的降解率接近100%。结果表明，该工艺较其它工艺具有更好的净化效果，可达到526. 3 kg-CO_2/mgTEQ（分解-DXN）。

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.