Studies on bromination and evaporation of zinc oxide during thermal treatment with TBBPA

Thermodynamic considerations indicate that base metal oxides such as ZnO, PbO, Cu₂O, etc. should easily react with HBr, the main gaseous product from the thermal decomposition of tetrabromobisphenol A (TBBPA), to form low boiling point metallic bromides suitable for volatile separation. In this work a differential scanning calorimeter and laboratory-scale furnace was used to investigate the scope and conditions for the bromination of ZnO by the thermal decomposition of TBBPA. The formed solid, condensed, and gaseous products were analyzed by X-ray diffraction analysis, electron probe microanalysis, inductively coupled plasma analysis, ion chromatography, and gas chromatography coupled with mass spectrometry. The results obtained in this study indicate that the bromination of ZnO occurred at 272°C (DSC) and above 290 °C (furnace) with an effectiveness of 41, 64, and 81% dependent on the experimental conditions. Volatilization of the formed ZnBr₂ began at 340 °C and had a 45% yield at 650 °C. This yield corresponded to 28-36% of the original zinc content in the mixture under the present experimental conditions.