Optimization and mechanism of Tetrabromobisphenol A removal by dithionite under anaerobic conditions: Response surface methodology and degradation pathway

In this study, dithionite (DTN) was used to degrade Tetrabromobisphenol A (TBBPA), a widely applied brominated flame retardants, under anaerobic conditions with the reaction terminator of nitrate. The optimization of reaction parameters including TBBPA concentration, DTN concentration and pH value were conducted by response surface methodology (RSM) based on central composite design (CCD). The degradation process could be simulated accurately by a quadratic model with the correlation coefficient R-2 of 0.9550. The interaction between pH and DTN concentration was significant with the p-value of 0.0017. Moreover, the maximum TBBPA removal was 87.6 +/- 3.2% and obtained at TBBPA concentration of 2.00 mu M, the DTN concentration of 322.31 mu M, and the pH of 6.14 under anaerobic conditions. It was found that the factors influenced TBBPA removal followed the order: pH > DTN concentration > TBBPA concentration. The major active products from DTN are SO32- and S2O32-. In addition, different inhibitions of natural water matrix including chloride, bicarbonate, sulfide and humic acid on TBBPA degradation had been confirmed. According to the identified six intermediates via gas chromatography-mass spectrometry (GC-MS), two steps of the degradation pathways were speculated, including the breakage of C-Br bond and C-C bond. This study provides a convenient way to degrade TBBPA.

Automated summary

In this study, dithionite was used to degrade Tetrabromobisphenol A under anaerobic conditions with nitrate as the reaction terminator. The optimization of reaction parameters and the degradation pathways were investigated. The results provide a convenient way to degrade TBBPA.