Abstract: This study investigated the removal characteristics of dibenzofuran and its mechanisms of physical desorption and chemical conversion during the thermal desorption of oil-contaminated soil. The results demonstrated that after remediation at 300 °C, the residual mass fraction of dibenzofuran in the soil was below 24.46 μg/g, which is lower than the risk screening values for Class I construction land as stipulated by the local standards of Hebei and Guangdong provinces. Among the kinetic models, three types of exponential decay models (basic, composite, and modified) were found to be more suitable for exploring the physical desorption behavior of dibenzofuran under heating conditions than first/second-order kinetic models. Analysis based on the Criado and Coats-Redfern models revealed that the most appropriate models for describing the chemical transformation behavior of dibenzofuran were the power function model P2 (initial stage), the contracting surface model R2 (middle stage), and the contracting surface model R2, contracting model R1, and contracting volume model R3 (late stage). The frequency of effective molecular collisions of dibenzofuran was significantly higher during the Contracting model R1 stage than in other model stages. Furthermore, the initial pyrolysis stage required the highest activation energy, substantially greater than that required in the middle and late stages.

Key words: petroleum-contaminated soil, dibenzofuran, thermal desorption, desorption mechanism, chemical conversion mechanism