Mechanochemical degradation of hexabromocyclododecane and approaches for the remediation of its contaminated soil

Hexabromocyclododecane (HBCD) has been listed in the Stockholm Convention for elimination due to its persistent and accumulative properties. In consideration of its sound disposal, mechanochemical (MC) method was employed using different co-milling reagents. Fe-Quartz was proven to a good reagent for HBCD destruction achieving both good degradation efficiency and high yield of bromide. The absence of organic matters after MC treatment was demonstrated by thermogravimetry and GC-MS analysis, indicating the complete degradation of HCBD and its conversion into inorganic compounds. No obvious intermediates could be detected due to the swift and spontaneous reaction between HBCD and Fe-Quartz. FTIR and Raman spectra further showed that the organic structures in HBCD were broken down while amorphous and graphite carbon were obtained as another final product besides bromide. After the successful destruction of HBCD, approaches to remediate its contaminated soil were also carried out. Fe-Quartz was also proven to be the best reagent for HBCD degradation in Kaolin, while CaO showed better performance for the remediation of HBCD contaminated Krasnozem. For practical application, preliminary experiments are necessary in order to select a suitable co-milling reagent and a proper milling time depending on the differences in soil properties and HBCD concentration.