Performance and mechanisms for tetrabromobisphenol A efficient degradation in a novel homogeneous advanced treatment based on S2O42− activated by Fe3+

Tetrabromobisphenol A (TBBPA), a representative brominated flame retardant (BFR), generally could be debrominated and degraded effectively in photolysis systems with the high energy consumption. In this study, the novel sulfate radical (SO4•-) generation resource of dithionite (S2O42-), activated by the common transition metal of Fe3+, has been applied for establishing an innovative homogeneous advance treatment system for BFR treatment in water. When coupling Fe3+ with S2O42-, TBBPA degradation efficiency could be remarkably improved from 38.7% to 93.8% with the debromination and mineralization efficiency of 83.9% and 18.5% in 60 min, respectively. The primary reactive species also have been identified as SO3•-, SO4•- and •OH responsible for TBBPA treatment and the contributions of SO4•- and •OH have been calculated as 43.8% and 28.4% for TBBPA degradation, respectively. In Fe3+/S2O42- system, TBBPA was effectively degraded in a wide initial pH range (3.0-9.0), whose activation energy was calculated as 32.01 kJ mol-1. Due to the only operation of reagents dosing, the energy consumption and cost could be decreasing significantly without any light energy input and reaction conditions (e.g., pH and dissolved oxygen) adjustment compared with the general photolysis process. Moreover, some possible degradation approaches of TBBPA also have been proposed via GC-MS including debromination, hydroxylation, methylation, and mineralization in Fe3+/S2O42- system. And these probable degradation pathways also have been confirmed with the decreased Gibbs free energy (ΔG) based on density functional theory (DFT). This study has revealed that it was promising of Fe3+/S2O42- system for BFRs degradation and detoxification efficiently through the simple operation and mild condtions.