Abstract: In order to investigate the degradation and the degradation time of degradable polyethylene(PE) film residues after removing the visual pollution into the soil, it is necessary to establish the method of separation and recovery PE residues from soil. PE wax powders (PEW, M_w=5 000) was taken as simulated PE residue, and then they were extracted in soil through the Soxhlet apparatus extraction method on the high-temperature by using mixed solvent (V_heptane∶V_xylene =1∶4). The PEW samples were characterised by Fourier transform infrared spectroscopy (FT-IR), high temperature gel permeation chromatography (HT-GPC), thermal analyzer (DSC) after the separation. The effection of the extraction time and soil types on the molecular structure and thermal properties of PEW were studied. At the same time, the molecular weight of the PEW after buried 1~3 years were determinated by the root cellar experiment. The results showed that the extraction rate increases with extraction time, and it reaches the maximum after 2.5 h (92.5%). The FT-IR spectra illustrates that the molecular structure of PEW is not destroyed during the extraction, but the extraction time has a certain influence on the crystallization of PEW which its melting temperature and crystallization temperature were raised by 1~3 ℃, respectively. The extraction time does not have much influence on average molecular of PEW, but it makes the molecular weight distribution narrow. The PEW recovery is independent of soil type. The root cellar experiment results show that the extraction method can be used to evaluate the degradation of actual PEW residue in soil and assess the total degradation time of PE after long-term tracking down.

Key words: separation, high-temperature Soxhlet extraction, polyethylene wax residues, soil, degradation, root cellar