Analysis of clean up mechanism of PCB-polluted sediment particles

Abstract

The authors previously proposed a clean up method for PCB-polluted sediment by the use of liquefied DME (dimethyl ether) gas. In a laboratory-scale experiment, 99% of PCB and water could be simultaneously removed from the sediment by solvent extraction using liquefied dimethyl ether. The energy consumed by this method was a half of latent heat of water; thus, this method using liquefied DME was confirmed to be effective and energy efficient. However, from a practical application standpoint, not only scale-up procedure but also basic microscopic consideration for clean up mechanism of PCB-polluted sediment particles are indispensable. In this study, we examined coexistence phenomena of binary Lennard-Jones liquid phases adsorbed on sediment particle by molecular dynamics simulation. The simulation results showed that surface coverage of PCB-like phase increased in proportion to PCB concentration in the bulk liquefied DME phase. Based on the results, this method was experimentally tested on oil-polluted soil by using a bench-scale experiment. The bench-scale experiment is successful in simultaneously removing both water and oil from soil powder. One application of this technology is expected to be the recovery of PCBs that leak into the urban rivers and other parts of the environment and from transformers that have been contaminated by oil containing PCBs. We would like to investigate the properties of PCBs in liquefied DME extracted from the sludge obtained from urban rivers etc. that contains PCBs and expand the range of materials to which the DME dewatering and deoiling technologies are applicable.