Effects of Cu²⁺, Ag⁺, and Pd²⁺ on the reductive debromination of 2,5-dibromoaniline by the ferrous hydroxy complex

Abstract

The ferrous hydroxy complex (FHC), composed of structural Fe^Ⅱ, has been shown to reduce a range of organic and inorganic contaminants. This study focused on the catalytic effects of Cu²⁺, Ag⁺, or Pd²⁺ on the reactivity of FHC suspensions towards 2,5-debromination (2,5-DBA). It was found that the target compound (2,5-DBA, 50 mg/L) could hardly be debrominated by FHC alone. However, Cu²⁺, Ag⁺, or Pd²⁺ had a significant promotion effect on the catalytic reactivity of structural Fe^Ⅱ on 2,5-DBA reduction. Pd²⁺ exhibited the best catalytic activity followed by Ag⁺ and Cu²⁺ in this study and the reductive debromination by Pd/FHC and Ag/FHC followed the pseudo-first-order kinetic model. Products distribution was highly dependent on the metal ions used. A reaction pathway was proposed in which the by-products were produced by hydrogenolysis and the elution order of bromines depended on the metal ions used. The enhanced reduction of 2,5-DBA by FHC suspensions modified by metal ions may prove useful in the development of improved materials for the treatment of halogenated organic compounds.

Keywords:

• ferrous hydroxy complex
• metal ions
• catalysis
• reductive debromination
• halogenated organic compounds

Acknowledgements

This study was financially supported by the Natural Science Foundation of China (Grant No. 50808136 and 41172210), the Foundation of The State Key Laboratory of Pollution Control and Resource Reuse, China (Grant No. PCRRY11013) and the National Key Technology R&D Program (Grant No. 2013BAC01B01).