Removal of Pollutants from High Polychlorinated Biphenyl Level Contaminated Soil at Different Thermal Treated Time

Abstract

High contaminated level of polychlorinated biphenyl (PCBs) in soil could not be easily removed by routine method. Since thermal treatment technology becomes a promising method especially for removal of volatile organic compounds, it has not yet been widespread in China for some technical and economic reasons. Experiments were conducted in a horizontal quartz tube furnace with nitrogen as the unique carrier gas, and heating temperature was set at 500oC with retention time of flue gas desorbed from soil was about 1 min. It has been found that total removal efficiency of PCBs from soil increased with the heating time was prolonged. Thermal treated time of 60 min seems suitable for the removal of PCBs, with the removal efficiency of 95.8% in solid phase. It has also been concluded that the removal mechanism of PCBs from soil endures dechlorination and destruction reactions with anticipation of catalytic metals. Normal gaseous pollutants desorbed from soil were also studied, H2O evaporation was favored with at the beginning of thermal process; after H2O evaporation, the organic matters began to decompose; when the thermal treated time was longer than 20 min, the desorption of the normal gaseous pollutants were almost finished (except for NH3).