EX-SITU THERMAL DESORPTION BEHAVIORS OF LOW-RINGS PAHS

With the rapid development of China's industries and urbanization, the massive use of fossil energy has led to an increasing amount of PAHs residues in the environment, which poses serious hazards to the environment and human health. The effects of thermal desorption temperature, time and the structure of PAHs themselves on the thermal desorption were investigated with 2~4 ring PAHs. Additionally, the effect of thermal desorption on soil properties were briefly analyzed, and the energy consumption of thermal desorption in a tube furnace was also evaluated. The results showed that the desorption removal efficiency of low ring PAHs showed an increasing trend with the increase of desorption temperature and desorption time. Under the conditions of 300 ℃ and 30 min of desorption, 2 ring-PAHs was completely removed, and the removal efficiency of 3 ring-PAHs and 4 ring-PAHs was 93.22% and 83.85%, respectively. The preferred conditions for each PAHs component to meet the objective values of the remediation standard(DB11/T 811—2011) were as follows: Nap was remediated at a desorption temperature of 100 ℃ for 10 min; Phe and Ant were remediated at 250 ℃ for 30 min and 150 ℃ for 60 min, respectively; the residues of Fla and Pyr were basically higher than the standard screening values, which required further adjustment of the thermal desorption working parameters or the addition of modifiers for synergistic remediation to reduce the cost. Moreover, the proportion of coarse soil particles decreased after thermal desorption, which was consistent with the fragmentation of large particles into small particles in SEM. The results can provide theoretical references for application of thermal desorption technology in remediation of PAHs contaminated soil.