Abstract: In view of the long-term problem that hexachlorobenzene ( HCB) is difficult to degrade in soil, based on mechanochemical method,this study systematically investigated the degradation effect of aluminum silicate ( kaolin,muscovite and bentonite) in soil,and discussed the influence of milling speed,milling time and initial concentration of HCB on the degradation efficiency of HCB. When the concentration of HCB is 50 000 mg / kg,after 2 h ball milling at 600 r / min,the HCB removal ability of aluminoid silicate minerals is ranked as follows:kaolin,muscovite and bentonite. The removal rates of HCB by kaolin and muscovite are 90. 13% and 85. 72%,respectively,and the bentonite hardly degrades HCB. The removal rate of HCB increased with the increase of milling time and was positively correlated with the rotational speed. The decrease of the initial concentration of HCB is conducive to the degradation and dechlorination efficiency of HCB. When HCB is at a high concentration level of 50 000 mg / kg,the dechlorination efficiency of kaolin and muscovite is low;When HCB is at a low concentration level of 2 500 mg / kg,the dechlorination effect of kaolin and muscovite is improved,and the dechlorination effect of kaolin is better than that of muscovite. Using ESR to detect the free radical signal,it was found that kaolin produced high reactive oxygen species free radicals under mechanochemical action,while muscovite and bentonite did not produce free radicals. GC-MS was used to analyze the degradation intermediates of HCB. When kaolin was used as an additive,the free radicals generated caused C—Cl of HCB to fracture. After continuous dechlorination process,the stable structure of HCB was broken and a series of unstable Cl-containing intermediates were formed. In summary,aluminum silicate minerals can degrade HCB efficiently under mechanical and chemical action,and are cheap and easy to cause no secondary pollution,which has a wide range of application potential in the field of soil remediation.

Key words: mechanochemical method,aluminum silicate,hexachlorobenzene,soil remediation,dechlorination,degradation mechanism