Mechanochemical conversion of brominated POPs into useful oxybromides: a greener approach

Several brominated flame retardants (BFRs) have been found to have adverse effect on human health and the environment and classified as persistent organic pollutants (POPs). Mechanochemical destruction is a promising technology for the safe disposal of POPs because it can achieve their complete carbonization by solvent-free high energy ball milling at room temperature, thus preventing unintentional dioxins formation during the destruction process. With the financial support by the National High Technology Research and Development Program of China (2013AA06A305), we employed stoichiometric quantities of Bi₂O₃ or La₂O₃ as co-milling reagent (Bi/La-to-Br atomic ratio = 1) to destroy four BFRs (viz. decabromodiphenyl ether, decaBDE; hexabromocyclododecane, HBCDD; tetrabromobisphenol A, TBBPA; hexabromobenzene, HBB), which were selectively and completely converted into their corresponding oxybromides (i.e. BiOBr and LaOBr). These products possess very peculiar catalytic and optical properties, so can be used for some actual and many more potential industrial applications. In this way, bromine is beneficially reused in the final product, while POPs carbon skeleton is safely destroyed to amorphous carbon and CO₂.