Recycling of Spent Hydrodehalogenation Catalysts - Problems Dealing with Separation of Aluminium

Abstract

Our study is focused on utilization and recycling of copper and nickel applicable for reductive degradation of tetrabromobisphenol A (TBBPA), the high use brominated flame retardant for printed circuit boards. Deactivated and/or poisoned hydrodebromination catalysts are produced by reductive destruction of brominated phenol (TBBPA) dissolved in alkaline aqueous solution using Raney Al-Ni and/or Devarda's Al-Cu-Zn alloys. Spent metallic slurry is treated with aqueous sulfuric acid to dissolve residual aluminium and/or zinc and decanted residual metal is subsequently treated under oxidation conditions and dissolved in excess of mineral acid by co-action of oxidant. The corresponding metal salt is separated from corresponding leachates containing excess of acid by evaporation and recycling of volatile components. Obtained copper or nickel salts were used as sources of Raney type hydrodebromination catalysts produced for in-situ by action of NaBH4.