Synthesis And Laccase-catalyzed Degradation Of Several Typical Hydroxylated Polybrominated Diphenyl Ethers And Polybrominated Biphenyls

As new kinds of persistent organic pollutants, the hydroxylated polybrominated diphenyl ethers (OH-PBDEs) and hydroxylated polybrominated biphenyls (OH-PBBs) have been frequently found in environment. They are of significant concerns because of its high toxicity and possibility of transformation to brominated dioxins under natural conditions. However, it is hard to get enough standard reagents of OH-PBDEs and OH-PBBs from markets, which has impeded the research of how do OH-PBDEs and OH-PBBs transform in environment. Herein, in this study, we synthesized several typical OH-PBDEs and OH-PBBs and explored the transformation of 2’-OH-BDE-68 by laccase. The main research results include:(1) 4 products of OH-PBDEs and OH-PBBs (2’-OH-BDE-68, 2’-OH-BDE-7,6’-OH-BDE-25 and 2,2’-OH-BB-80) were synthesized based on the basic organic reactions of coupling, oxidation and bromination. The crude products then were purified using a C18 column on a semi-preparative high-performance liquid chromatography, which improved the recovery rate of purification compared to the way of column chromatography. The recovery rate of 2’-OH-BDE-68, 2’-OH-BDE-7,6’-OH-BDE-25 and 2,2’-diOH-BB-80 were 80%,83%, 84% and 90% respectively. The purified products were identified by gas chromatography-mass spectrometer and 1-nuclear magnetic resonance. Results showed that the products obtained in this study were the target compounds with a purity> 99%。(2) The degradation kinetics of 2’-OH-BDE-68 by laccase were done. We also explored the influence of pH and temperature to this reaction and identified the formation products. Results showed:the decay did not fit the first-order kinetics but the model of Ct=Cblance+Creactivee-kt. Transformation of 2’-OH-BDE-68 by laccase was faster in acid environment (pH<7.0), and reached the fastest velocity at pH 5.0. Increasing the temperature can accelerate the reaction but laccase seemed to be partly inactive when the temperature higher than 35℃. The Michaelis equation for 2’-OH-BDE-68 catalyzed by laccase was Y=2.5677X+0.33541(R2=0.9807). The Michaelis constant (Km) was 7.655μmol/L, and Vmax was 2.98μmol/(L.min.U).2,4-DBP was identified as its formation product.