Application of catalytic hydrodehalogenation for the removal of brominated flame retardants

The aim of this work is to evaluate the feasibility of aqueous-phase catalytic hydrodehalogenation (HDH) for the fast and environmentally-friendly degradation of the flame retardant tetrabromobisphenol A (TBBPA). TBBPA is a pollutant of emerging concern characterized by a strong persistence that has been associated with negative effects on both the environment and human health. The complete degradation of TBBPA during the HDH reaction ([TBBPA]0 = 1 mg L-1) was achieved in short reaction times (5 min) under ambient conditions using 1 g L-1 of a commercial Pd/Al2O3 (1% wt.) catalyst. Remarkably, bisphenol A, a known endocrine disruptor, was generated along reaction once TBBPA was completely debrominated. However, its complete removal was achieved by further hydrogenation. Although TBBPA suffered a strong adsorption on the catalyst surface, both adsorbed and free molecules reacted completely, and bromine balance was closed (>95%). HDH of TBBPA followed a pseudo-first order kinetic and a kinetic constant value of 1.03 min-1 was obtained. Furthermore, the effect of the temperature was evaluated between 15 and 35 ºC, obtaining higher degradation rates when the temperature increased. A resulting apparent activation energy of 36 kJ mol-1 was calculated. Notably, the catalyst showed a notable stability after three consecutive HDH runs.