Only very few abiotic reductants have been reported to be capable of transforming hexabromocyclododecane (HBCD), one of the most frequently used brominated flame retardants (BFRs). In this study, the kinetics, mechanism and influencing factors of reductive transformation of HBCD by a novel abiotic reductant (sulfidated nanoscale zerovalent iron, S-nZVI) were explored systematically. Nearly 100% of the initial HBCD (20 mg L-1) in reaction solution was transformed by S-nZVI within 12 h, leading to a high transformation rate that was 1.4-9.3 times greater than those of the two newly reported abiotic reductants for HBCD (e.g., FeS and nZVI). Specially, the kinetics of HBCD transformation by S-nZVI fitted well with a pseudo-first-order kinetic model and the transformation rate constant for β-HBCD was much higher than those for α- and γ-HBCD. Analysis of transformation products suggested that S-nZVI could debrominate HBCD to form tetrabromocyclododecene and dibromocyclododecadiene. XPS data suggested that both Fe(II) and S(-II) on the surface of S-nZVI were involved in the transformation of HBCD. The optimal pH for the transformation of HBCD by S-nZVI was approximately 5.0. The presence of different inorganic ions typically encountered in groundwater (e.g., Ca2+, Mg2+, NO3-, HCO3- and Cl-) had adverse effects on the transformation of HBCD by S-nZVI. An increase in ionic strength, solvent content and HBCD concentration resulted in a decrease in transformation rate of HBCD by S-nZVI, while an opposite trend was observed for reaction temperature and S-nZVI dose. Taken together, our results have important implications for the future use of S-nZVI as an efficient agent for remediating anoxic aquatic environments by contaminated HBCD.

Abiotic transformation of hexabromocyclododecane by sulfidated nanoscale zerovalent iron: Kinetics, mechanism and influencing factors

253rd National Meeting (2017)

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