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

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.