Formation of brominated by-products during the degradation of tetrabromobisphenol S by Co2+/peroxymonosulfate oxidation

Tetrabromobisphenol S (TBBPS) exposure causes gastric cell senescence and inflammation by inducing iron overload

Tetrabromobisphenol S (TBBPS) is a brominated flame retardants (BFRs). TBBPS is widely used as a new type of BFR to replace TBBPA. Here, we used gastric cells as a model for evaluating the effect of TBBPS on the toxicology of gastric cells. Biochemical assays such as indirect immunofluorescence, cell proliferation assay were performed to analyze the toxicological effects of TBBPS on gastric cells. Cell proliferation analysis showed that TBBPS caused inhibition of gastric cell proliferation, and TBBPS induced gastric cell death. Further analysis showed that TBBPS led to ferroptosis and senescence of gastric cells by detecting ferroptosis-related marker molecules. Further work showed that TBBPS treatment resulted in lowered ferritin expression alongside heightened transferrin levels, which may be a potential molecular mechanism for TBBPS-induced ferroptosis and senescence in gastric cells. Here, our team investigates the effects of TBBPS on gastric cells in an in vitro model, and found that TBBPS caused toxicological damage to gastric cells. This study indicates potential toxic effects of TBBPS on the gastric cells, thereby providing a basis for further research into the toxicology of TBBPS.

One electron oxidation-induced degradation of brominated flame retardants in electroactive membrane filtration system: Vital role of dichlorine radical-mediated process

Reactive chlorine species (RCS) are inevitably generated in electrochemical oxidation process for treating high-salinity industrial wastewater, thereby resulting in the competition with coexisting hydroxyl radicals (•OH) for oxidizing recalcitrant organic compounds. Due to the low redox potentials compared to •OH, the role of RCS has been often overlooked. In this work, we developed an electroactive membrane filtration (EMF) system that had a high removal efficiency (99.1 ± 0.5 %) for tetrabromobisphenol S (TBBPS) at low energy consumption (1.45 kWh m-3). Electron spin resonance spectroscopy and molecular probing tests indicated the predominance of Cl2•-, of which steady-state concentration (2.2 ×10-10 M) was extremely higher than those of ClO• (6.7 ×10-13 M), •OH (0.95 ×10-13 M), and Cl• (2.39 ×10-15 M). The density functional theory (DFT) and intermediate product analysis highlighted that Cl2•- radicals had a higher electrophilic attack efficacy than •OH radicals for inducing changes in the electron density of the carbon atoms around phenolic hydroxyl groups, thus leading to the generation of transition state intermediates and accelerating the degradation of TBBPS. Our work demonstrates the vital role of Cl2•- radicals for pollutant degradation, highlighting the potential of this technology for cost-effective removal of recalcitrant organic compounds from water and wastewater.

The mechanism of photodegradation reaction of different dissociation forms of tetrabromobisphenol S in water with free radicals and the ecotoxicity evaluation of related products

Tetrabromobisphenol S (TBBPS) is a widely used brominated flame retardant that has attracted environmental concern due to its abundant presence in water. The objective of this study is to systematically analyze the direct photolysis and degradation mechanisms of TBBPS in two different dissociation forms in water, as well as to evaluate their toxicological effects induced by •OH, 1O2, and •NO2 radicals. The degradation mechanism of TBBPS is investigated with density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods, and the toxicity of the degradation products is assessed through toxicological studies. The results of the study indicate that the OH-addition and H-abstraction reactions are favorable pathways for •OH-induced TBBPS degradation. The H-abstraction reaction of TBBPS0 with •OH was more favorable than the •OH addition reaction. However, in the degradation of TBBPS-, the •OH addition reaction was favored over the H-abstraction reaction. Additionally, the indirect photolysis of TBBPS by 1O2 and •NO2 in water was found to be easier for TBBPS- compared to TBBPS0, with degradation mechanisms involving Br-substitution and NO2-addition reactions. The higher Ea values calculated indicate that the degradation of TBBPS by 1O2 and •NO2 in water has been a secondary reaction. The direct photolysis reaction pathway of TBBPS in water has involved the cleavage of the S1-C7 and S1-C16 bonds. For TBBPS0 in the S1/T1 states, the primary reaction pathway is the cleavage of the S1-C16 bond, while for TBBPS-, the primary reaction pathway is the cleavage of the S1-C7 bond. Furthermore, the computational toxicology results indicate a slight increase in the toxicity levels of most products, highlighting the significance of investigating the degradation byproducts of TBBPS in greater detail.

Degradation of Tetrabromobisphenol S by thermo-activated Persulphate Oxidation: reaction Kinetics, transformation Mechanisms, and brominated By-products

Brominated flame retardants (BFRs) are a group of contaminants of emerging environmental concern. In this study, systematic exploration was carried out to investigate the degradation of tetrabromobisphenol S (TBBPS), a typical emerging BFRs, by thermally activated persulfate (PDS) oxidation. The removal of 5.0 μM TBBPS was 100% after 60 min oxidation treatment under 60°C. Increasing the temperature or initial PDS concentration facilitated the degradation efficiency of TBBPS. The quenching test indicated that TBBPS degradation occurred via the attack of both sulphate radicals and hydroxyl radicals. Natural organic matter (NOM) decreased the removal rate, however, complete disappearance of TBBPS could still be obtained. Six intermediate products were formed during reactions between TBBPS and radicals. Transformation pathways including debromination, β-Scission, and cross-coupling were proposed. Brominated disinfection by-products (DBPs) in situ formed during the degradation of TBBPS were also investigated, such as bromoform and dibromoacetic acid. The presence of NOM reduced the formation rates of brominated DBPs. Results reveal that although thermo-activated PDS is a promising method for TBBPS-contaminated water, it can lead to potential brominated DBPs risks, which should be paid more attention to when SO4•--based oxidation technology is applied.

New Insights into the Role of Nitrite in the Degradation of Tetrabromobisphenol S by Sulfate Radical Oxidation

Tetrabromobisphenol S (TBBPS) is a brominated flame retardant and a contaminant of emerging concern. Several studies found that sulfate radical (SO₄^•-) oxidation is effective to degrade TBBPS. Here, we demonstrate that the presence of nitrite (NO₂^-) at environmentally relevant levels causes dramatic changes in the kinetics and pathways of TBBPS degradation by SO₄^•-. Initially, NO₂^- suppresses the reaction by competing with TBBPS for SO₄^•-. At the same time, SO₄^•- oxidizes NO₂^- to form nitrogen dioxide radicals (NO₂^•), which actively react with some key TBBPS degradation intermediates, thus greatly altering the transformation pathway. As a result, 2,6-dibromo-4-nitrophenol (DBNP) becomes the primary TBBPS product. As TBBPS undergoes degradation, the released bromide (Br^-) is oxidized by SO₄^•- to form bromine radicals and free bromine. These reactive bromine species immediately combine with NO₂^• or NO₂^- to form nitryl bromide (BrNO₂) that in turn attacks the parent TBBPS, resulting in its accelerated degradation and increased formation of toxic nitrophenolic byproducts. These results show that nitryl halides (e.g., BrNO₂ or ClNO₂) are likely formed yet inadequately recognized when SO₄^•- is applied to remediate halogenated pollutants in the subsurface environment where NO₂^- is ubiquitously found. These insights further underscore the potential risks of the application of SO₄^•- oxidation for the remediation of halogenated compounds in realistic environmental conditions.