Abstract: 2,4-dichlorophenol contaminated soil was treated by ball milling mechanochemical method. Particle size analysis, scanning electron microscopy, XRD, IR and GC-MS were used to characterize the 2,4-dichlorophenol contaminated soil before and after ball milling. The mechanism of ball milling mechanochemical treatment of organic contaminated soil was studied, and the possible degradation path of 2,4-dichlorophenol was analyzed. The results showed that the content of 2,4-dichlorophenol in the soil was degraded from 9 009.0 mg/kg to 70.7 mg/kg after ball milling at 400 r/min for 4 h, and the degradation rate reached 99%. At the same time, the concentrations of phenol, dimethyl phthalate and benzo （b） fluoranthene were also degraded simultaneously. In the process of ball milling, with the increase of milling time, the particle size of soil decreased, the area of reaction surface increased, the reaction speed was accelerated, the shape and structure of soil particles were changed, and the chemical energy was increased; meanwhile, C-Cl bond broke, C-H and C=C bonds appeared, H and C replaced the Cl on 2, 4-dichlorophenol and Cl was removed from 2, 4-dichlorophenol. In this process, SiO₂ did not participate in the reaction. It was speculated that the degradation path of 2,4-dichlorophenol was as follows： With the increase of chemical energy, 2,4-dichlorophenol collided with calcium oxide, electron transfer occurred, free radical hydrogen was generated, C-Cl bond was broken, and 2-chlorophenol was further degraded into small molecule organic matter, which was gradually degraded to amorphous carbon and inorganic chlorine.

Key words: mechanochemical method, soil, ball milling, 2,4-dichlorophenol, degradation