Mechanochemical dehalogenation of brominated flame retardants and preliminary application for recycling BFR-containing plastic waste

Hexabromocyclododecane (HBCD) is one of the most widely used brominated flame retardant (BFR), which has attracted increasing attention due to the persistence, bioaccumulation and adverse effect to wildlife and human. Considering the strong need for the disposal of HBCD containing waste, mechanochemical (MC) pretreatment technology was investigated to destroy BFRs as a dehalogenation method in this study. Silica and aluminium powders were used as additives, and mechanochemical method was applied to degrade BFRs for both HBCD powder and waste plastics. The results showed that HBCD was effectively degraded during mechanochemical treatment with the aid of Si-Al-based additives. The optimized condition was determined to be a SiO2/Al ratio = 7:2 with a reagent ratio of 15:1. The optimized mechanochemical method was applied to dispose BFRs contained waste plastics. The results showed that dehalogenation of plastics occurs during mechanochemical destruction and that smaller plastic particles accelerated dehalogenation. Finally, the reaction process and intermediates were studied to provide insight into the mechanochemical degradation mechanism of HBCD, and a possible reaction pathway was proposed.

Automated summary

Mechanochemical pretreatment technology was used to effectively degrade hexabromocyclododecane (HBCD) by adding silica and aluminium powders as additives. The optimized method was also applied to dispose brominated flame retardants (BFRs) contained waste plastics, and the smaller plastic particles accelerated the dehalogenation process. The study also proposed a possible reaction pathway for the mechanochemical degradation of HBCD.