Effect of temperature and particle size on the thermal desorption of PCBs from contaminated soil
- 562 Downloads
Thermal desorption is widely used for remediation of soil contaminated with volatiles, such as solvents and distillates. In this study, a soil contaminated with semivolatile polychlorinated biphenyls (PCBs) was sampled at an interim storage point for waste PCB transformers and heated to temperatures from 300 to 600 °C in a flow of nitrogen to investigate the effect of temperature and particle size on thermal desorption. Two size fractions were tested: coarse soil of 420–841 μm and fine soil with particles <250 μm. A PCB removal efficiency of 98.0 % was attained after 1 h of thermal treatment at 600 °C. The residual amount of PCBs in this soil decreased with rising thermal treatment temperature while the amount transferred to the gas phase increased up to 550 °C; at 600 °C, destruction of PCBs became more obvious. At low temperature, the thermally treated soil still had a similar PCB homologue distribution as raw soil, indicating thermal desorption as a main mechanism in removal. Dechlorination and decomposition increasingly occurred at high temperature, since shifts in average chlorination level were observed, from 3.34 in the raw soil to 2.75 in soil treated at 600 °C. Fine soil particles showed higher removal efficiency and destruction efficiency than coarse particles, suggesting that desorption from coarse particles is influenced by mass transfer.
KeywordsPCBs Thermal desorption Dechlorination Destruction Particle size Soil remediation
This research work was financially supported by Major State Basic Research Development Program of China (973 Program) (No.2011CB201500), the National High Technology Research and Development Program of China (No.2009AA061304), and the Sino-Romania Scientific and Technological Cooperative Project (41–6).
- Lighty J (1988) Fundamentals of thermal treatment for the cleanup of contaminated solid wastes. Ph.D Dissertation, University of UtahGoogle Scholar
- Qiao S (2011) Handbook for testing soil physical and chemical properties. China University of Geosciences Press, Wuhan, China (in Chinese)Google Scholar
- USEPA (2008) Method 1668B: chlorinated biphenyl congeners in water, soil, sediment, biosolids, and tissue by HRGC/HRMS. USEPA, Washington, DCGoogle Scholar
- USEPA (2012) health effect of PCBs. http: //www.epa.gov/epawaste/hazard/tsd/pcbs/pubs/effects.htm. Accessed on August 28, 2013
- Van den Berg M, Birnbaum L, Denison M, De Vito M, Farland W, Feeley M, Fiedler H, Hakansson H, Hanberg A, Haws L, Rose M, Safe S, Schrenk D, Tohyama C, Tritscher A, Tuomisto J, Tysklind M, Walker N, Peterson R (2006) The 2005 World Health Organization reevaluation of human and mammalian toxic equivalency factors for dioxins and dioxin-like compounds. Toxicol Sci 93(2):223–241CrossRefGoogle Scholar
- Weber R, Gaus C, Tysklind M, Johnston P, Forter M, Hollert H, Heinisch E, Holoubek I, Lloyd-Smith M, Masunaga S, Moccarelli P, Santillo D, Seike N, Symons R, Torres JP, Verta M, Varbelow G, Vijgen J, Watson A, Costner P, Woelz J, Wycisk P, Zennegg M (2008) Dioxin- and POP-contaminated sites-contemporary and future relevance and challenges. Environ Sci Pollut Res 15(5):363–393CrossRefGoogle Scholar