Anaerobic transformation of a technical pentabromo diphenyl ether product using superreduced vitamin B12

Abstract

Technical pentabromo diphenyl ether (DE-71) was anaerobically transformed using superreduced cyanocobalamin (vitamin B12). The principal pathway was identified to be reductive debromination. As a consequence, the proportion of higher brominated homologues decreased in favor of the lower brominated diphenyl ethers (BDEs) while the molar amount of BDE congeners was virtually constant throughout the experiment. As an example, the ratios of BDE 99/BDE 47 was >1 at the start, ∼1 after 1 week, and <1 after 2 weeks. A further feature identified was the alternating removal of bromine atoms from the two rings when two or more Br were substituted by hydrogen. BDE 49 and BDE 66 proved to be good indicators for the reductive debromination of both DE-71 and DE-79. Hence, a thorough study of BDE 49 and BDE 66 might be helpful to solve the question whether high amounts of key-PBDEs in technical pentabromo diphenyl ether in the environment originate from such sources or are debromination products of higher BDEs.