Effect of temperature and particle size on the thermal desorption of PCBs from contaminated soil

Abstract

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.

Effect of co-contaminated soil mixtures as fixed/fluidized bed media on pollutants emission under thermal treatment

“…Since the treatments of co-contaminated soils are limited, it is widely agreed that multiple costly techniques are required (Khan et al 2004). A number of investigations have shown that thermal treatment (thermal desorption, incineration, pyrolysis, gasification, and vitrification) is one of the effective processes for complex substances remediation (González-Corrochano et al 2012;Qi et al 2014;Qin et al 2015;Taube et al 2008;Van Caneghem et al 2012).…”

Persistent Threats by Persistent Pollutants: Chemical Nature, Concerns and Future Policy Regarding PCBs—What Are We Heading For?

“…Another method is to add alkali metal carbonates, which will react and lead to pyrolysis [ 108 ]. Highly effective is thermal desorption for removing PCBs from soils [ 109 ]. Microbial degradation of soils is possible by adding Shewanella oneidensis to contaminated soils [ 110 ].…”

Planned Heating Control Strategy and Thermodynamic Modeling of a Natural Gas Thermal Desorption System for Contaminated Soil

“…Bulmau et al [19] studied the effect of heating temperature on soils polluted by polycyclic aromatic hydrocarbons (PAHs) and indicated that the removal efficiency increased from 5% at 350 • C to 80% at 650 • C when processed for the same time. Qi et al [20] found that the removal efficiencies after heating at 600 • C for 20 min, 40 min and 60 min are 20.86%, 64.47% and 95.7% respectively. The removal rate for polychlorinated biphenyls (PCBs) within the 20-40 min interval is greater than that of the first 20 min.…”