Formation and transport of PCDD/Fs in the packed bed of soil containing organic chloride during a thermal remediation process.
The authors previously proposed the concept of a new thermal remediation process for particulate/powder materials contaminated by polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and experimentally verified its validity on the basis of process efficiency. However, contaminees such as soils and fly ashes from waste incinerators often contain a considerable amount of other chlorides, which may act as a main source of chlorine in the formation of PCDD/Fs via thermal processes. The present study aims to examine the formation and transport of PCDD/Fs in the packed bed of soil containing a chloride during the process. Polyvinyl chloride (PVC) polymer was mixed with soil sample as an organic chloride model. A laboratory-scale apparatus was employed as a process simulator. Further, a technique to quench the process was applied to observe the concentration distribution of PCDD/Fs in the solid bed in the vertical direction. The result shows that the PCDFs tend to form dominantly in the high temperature (calcination and/or combustion) zone and are successively trapped in the low temperature (wet) zone. Especially, TeCDF is the most dominant homologue contained in the wet zone and outlet gas. Although PCDD/Fs are once trapped at the wet zone, the concentration of the remediated materials gives fairly low value (1.9 pg/g-dry, 0.04 pg-TEQ/g-dry). It signifies that organic chlorides mingled in the solid contaminee not affect the removal efficiency of PCDD/Fs in the process. Nevertheless, attention should be paid to the potential emission of PCDD/Fs in the outlet gas due to the presence of organic chloride in the soil.
Harjanto
Sri
S
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan.
Kasai
Eiki
E
Terui
Toshikatsu
T
Nakamura
Takashi
T
D001572:Benzofurans / Q000032:analysis*; D002712:Chlorides / Q000737:chemistry*; D003247:Conservation of Natural Resources; D000072338:Dibenzofurans, Polychlorinated; D004787:Environmental Pollution / Q000517:prevention & control*; D017745:Incineration; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000032:analysis*; D012037:Refuse Disposal; D012989:Soil Pollutants / Q000032:analysis*; D013696:Temperature
D001572:Benzofurans; D002712:Chlorides; D000072338:Dibenzofurans, Polychlorinated; D000072317:Polychlorinated Dibenzodioxins; D012989:Soil Pollutants