Debromination Of Tetrabromobisphenol A Research Articles

One-step process for debromination and mineralization of tetrabromobisphenol a by a layered double oxide-supported sulfurized nanoscale zero-valent iron under ambient conditions

Tetrabromobisphenol A (TBBPA), currently the most widely used brominated flame retardant, has attracted significant attention. However, traditional methods for deep debromination or mineralization of TBBPA usually include multiple steps and require external oxidants. In this study, we report a complete degradation of TBBPA through a one-step process of only adding a layered double oxide-supported sulfurized nanoscale zero-valent iron (S-nZVI@LDO) under ambient conditions. TBBPA was rapidly removed by S-nZVI@LDO with an efficiency of 95.6 % (10 mg⋅L-1) within 12 h. The kinetic rate constant (0.0035 min−1) was greater when compared with traditional reductants. The produced Br- ion occupied 76.7 % of total Br content, and the concentration of total organic carbon decreased by over 50 %, suggesting a deep debromination and mineralization of TBBPA by S-nZVI@LDO. It is caused by the substantial improvement of electron transfer, O2 adsorption, and hydrophobicity of S-nZVI@LDO facilitating synchronous reductive debromination and O2 activation to produce ·O2– and ·OH, as approved by electrochemical test, O2-TPO analysis, EPR analysis, and density functional theory calculations. The enriched structural S(−II) and enhanced Fe(III)/Fe(II) redox cycling exerted vital roles in maintaining the reduction potential of the composite. The degradation pathways analysis confirmed that debromination-mineralization mechanisms dominated the complete degradation of TBBPA. This study demonstrates the feasibility of the one-step mineralization removal of TBBPA only using S-nZVI@LDO under ambient conditions and offers insight into external oxidant-free in-situ elimination of halogenated persistent organic pollutants in a natural environment.

Rapid reactivation of aged NZVI/GO by Shewanella CN32 for efficient removal of tetrabromobisphenol A and associated reaction mechanisms

Tetrabromobisphenol A (TBBPA) is one of the most widely applied brominated flame retardants, which has consequently resulted in severe environmental contamination. Graphene oxide-loaded nanoscale zero-valent iron (NZVI/GO) has previously shown excellent performance for potential TBBPA removal. However, the aging of NZVI/GO resulted in reduced reaction rates. In this study, Shewanella CN32 was used to reactivate the performance of aged NZVI/GO. The results demonstrated that CN32 significantly reactivated aged NZVI/GO (27%) and consequently improved the removal of TBBPA by 240% in aged NZVI/GO+CN32 (92%). Compared to aged NZVI (0.07 mM), CN32 rapidly decomposed the iron oxide passivation layer of aged NZVI/GO, with a subsequent increase in the release of Fe2+ ions (0.12 mM). Moreover, Fe(II) vivianite (FeII3(PO4)2·8H2O) and SO42− type green rust (Fe3.6Fe0.9(O,OH,SO4)9) formed at the surface of aged NZVI/GO+CN32. GO accelerated the reduction of dissimilatory iron (α-Fe2O3) and the formation of vivianite crystals. Vivianite further improved the debromination of TBBPA. Furthermore, the semiquinone radicals (C=O) in the interface of the aged NZVI/GO effectively mediated electron transfer and reactivated the performance of aged NZVI/GO by CN32. It could therefore be concluded that CN32-induced iron oxide reduction and NZVI exposure, C=O mediated electron transfer, and vivianite-induced debromination were the main removal mechanisms of TBBPA in the system. It is a potential technology for convenient remediation of soil, groundwater, and lake.

Catalytic hydrodehalogenation of the flame retardant tetrabromobisphenol A by alumina-supported Pd, Rh and Pt catalysts

Tetrabromobisphenol A (TBBPA) is one of the most used BFRs, being characterized by a strong persistence and leading to negative effects on both the environment and human health. 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 brominated flame retardant TBBPA. Pd, Rh, and Pt on alumina commercial catalysts (1% wt.) were tested and reactions were performed under ambient operating conditions. TBBPA (1 mg L−1) was completely removed in short reaction times (< 5 min) using the Pd catalyst while longer reaction times were required in the case of Rh and Pt catalysts as active phase. Furthermore, although TBBPA suffered a strong adsorption on the catalyst surface, both adsorbed and free molecules reacted. Bromine balance was closed (> 95%) in 15 min using Pd/Al2O3. Nevertheless, employing Rh and Pt alumina-supported catalysts debromination of TBBPA increased progressively requiring much longer times and only 83% and 78% debromination yields were achieved after 2 h reaction, respectively. Bisphenol A (BPA), a well-known endocrine disruptor, was generated as reaction intermediate but it was further hydrogenated with both Pd and Rh catalysts, whereas it remained as reaction product with the Pt catalyst. A series reaction pathway considering both hydrodebromination and hydrogenation steps was proposed based on the obtained results. The experimental data obtained with the Pd/Al2O3 catalyst were successfully described by a pseudo-first order kinetic model, obtaining an apparent activation energy of 36 kJ mol−1. Notably, this catalyst showed a reasonable stability after three consecutive HDH runs.

Debromination of TetraBromoBisphenol-A (TBBPA) depicting the metabolic versatility of Dehalococcoides

TetraBromoBisphenol-A (TBBPA) is a widely used brominated flame retardant and an emerging contaminant that has amassed significant environmental impacts. Though there are a few studies that report the bioremediation of TBBPA, there is no direct evidence to suggest a metabolic use of TBBPA as the sole electron acceptor, which offers an advantage in the complete and energy-efficient process of debromination under anaerobic conditions. In this study, Dehalococcoides mccartyi strain CG1 was identified to be capable of utilizing TBBPA as the sole electron acceptor at its maximum soluble concentrations (7.3 μM) coupled with cell growth. A previously characterized reductive dehalogenase (RDase), PcbA1, and six other RDases of strain CG1 were detected during TBBPA debromination via transcriptional and proteomic analyses. Furthermore, as a commonly co-contaminated brominated flame retardant of TBBPA, penta-BDEs were debrominated synchronously with TBBPA by strain CG1. This study provides deeper insights into the versatile dehalogenation capabilities of D. mccartyi strain CG1 and its role in in situ remediations of persistent organic pollutants in the environment.

Cu-Catalyzed Hydrodehalogenation of Brominated Aromatic Pollutants in Aqueous Solution

The catalytic effect of copper in Devarda’s Al-Cu-Zn alloy (Dev. alloy) and sole metallic copper, copper salts and copper oxides in the coaction of NaBH4 within the hydrodehalogenation (HDH) of polybrominated phenols, such as the herbicide Bromoxynil in alkaline aqueous solution has been investigated. Namely, the hydrodebromination (HDB) activity of Dev. alloy/NaOH system has been compared to heterogeneous Cu-based catalysts using NaBH4 as a reductant. Differences in the solid-state structures of used Cu-based heterogeneous catalysts after the mentioned HDB process have been studied using the powder XRD and SEM techniques. It was found that some of the used copper-based catalysts are reusable and reasonably effective even at room temperature. Efficiency of the most promising copper-based reduction systems (Dev. alloy/NaOH and Cu-based catalysts/NaBH4) have been successfully tested within the HDB of industrially important brominated flame retardant tetrabromobisphenol A (TBBPA). Dev. alloy/NaOH and Cu-based catalyst generated in-situ within the CuSO4/NaBH4 produced were recognized as the most active HDB agents for complete debromination of both BRX and TBBPA.

Biodegradation and metabolism of tetrabromobisphenol A in microbial fuel cell: Behaviors, dynamic pathway and the molecular ecological mechanism

Tetrabromobisphenol A (TBBPA) has aroused widespread pollution in industrial wastewater. Microbial fuel cell (MFC) was proved powerful in organics degradation and simultaneous resource recovery during wastewater treatment. However, the TBBPA biotransformation potential, pathway and the related molecular mechanism remain poorly understood. In this study, the enhanced degradation and detoxification performance of TBBPA in MFC anode was confirmed, evidenced by the shorter degradation period (2.3 times shorter) and less generation of bisphenol A. UPLC-QTOF-MS analysis verified TBBPA metabolism went through reductive debromination, hydrolytic debromination, oxidative ring cleavage and o-methylation. Accompanied with those biochemical processes, the metabolites underwent dynamic changes. The distinctly decreased abundance and fewer interactions with other functional genera for the potential reductive dehalogenators (Pseudomonas, etc.) possibly led to the suppressed reductive debromination (5.1%) in the closed bioanode. Otherwise, the more abundant potential function bacteria with more collaborated interrelations, including hydrolytic dehalogenators (Acinetobacter, etc.), aromatics degrading bacteria (Geobacter, Holophaga, etc.) and electroactive bacteria (Geobacter, Desulfovibrio, etc.) made great sense to the enhanced hydrolytic debromination and detoxification of TBBPA. This study revealed that MFC anode was beneficial to TBBPA degradation and provided theoretical support for the decomposition and transformation of micro-pollutants in the municipal sewage treatment coupled with MFC process.

Efficient peroxydisulfate activation with nZVI/CuO@BC nanocomposite derived from wastes for degradation of tetrabromobisphenol A in alkaline environment

Peroxydisulfate (PDS) is a promising oxidant for sulfate radical based advanced oxidation processes (SAOPs), however its efficient activation is still a challenge. In this study, biochar-supported nano-zerovalent iron (nZVI) and copper oxide (CuO) nanocomposite (nZVI/CuO@BC), derived from low-cost wastes including scrap iron filings, copper leaching solution and corn stalks, was successfully fabricated for PDS activation to enhance tetrabromobisphenol A (TBBPA) degradation in alkaline environment. Under the conditions of 100 mg/L nZVI/CuO@BC, 0.2 mM PDS, pH 8.0 and 25 °C, 86.32% of PDS was activated and 98.46% of TBBPA was degraded within 45 min in nZVI/CuO@BC-activated PDS system. When the PDS concentration was 2 mM, the nZVI/CuO@BC-activated PDS system realized efficient debromination and mineralization of TBBPA at the ratio of 79.12% and 79.36%, respectively. The results of EPR studies and radical scavenger experiments revealed that both hydroxyl radical (·OH) and sulfate radical (SO4·-) were responsible for TBBPA degradation. The nZVI could active PDS indirectly through electron transfer mechanism and exhibited synergistic effects with CuO on PDS activation. Furthermore, the nZVI/CuO@BC-activated PDS system showed good potential to degrade TBBPA in real water environment. Therefore, nZVI/CuO@BC could be a novel strategy for efficient PDS activation and TBBPA degradation in alkaline environment.

Debromination of tetrabromobisphenol A in aqueous amine solutions under hydrothermal conditions

Tetrabromobisphenol A (TBBPA) powder was subjected to an aqueous amine solution in a small bomb-type batch reactor at temperatures from 447 to 553 K and pressures from 0.79 to 6.4 MPa. The effectiveness of aqueous amine solutions under hydrothermal conditions was examined for debromination of TBBPA, which is a brominated flame retardant commonly contained in printed circuit boards. The amines tested were methylamine, dimethylamine and trimethylamine. Compared to aqueous ammonia and aqueous sodium hydroxide solutions, all the amine solutions tested were more effective. For instance, the 89% debromination of the initial bromine contained in TBBPA was recovered by a 0.6 mol/kg aqueous methylamine solution at 533 K in 20 min. The debromination of TBBPA was accelerated with increasing reaction temperature and amine concentration. The four major products, 2,6-dibromophenol, 2-bromophenol, phenol and 2,6-dibromo-4-(1-methylethenyl)phenol, were detected by GCMS and the three former products were quantified by HPLC. According to the product distributions over time, a primary pathway of TBBPA debromination was proposed, in which the cleavage of a carbon-carbon bond initially took place, followed by debromination. The debromination reaction in an aqueous methylamine solution under hydrothermal conditions was described by pseudo first order reaction kinetics, and the activation energies changed at 473 K, and that above 473 K was much smaller than that in pyrolysis reported in the literature. The debromination rate constants at 473 and 533 K were proportional to methylamine concentration up to 0.3 mol kg−1, and those increased gradually above the temperature. The authors proposed debromination of TBBPA in an aqueous amine solution under hydrothermal conditions as a new debromination method due to relatively fast reaction rates and recovery of bromine as bromide ion.

One-step green preparation of magnetic seaweed biochar/sulfidated Fe0 composite with strengthen adsorptive removal of tetrabromobisphenol A through in situ reduction

Rare information is available on the facile preparation of biochar/sulfidated Fe0 composite. A facile one-step green method was established for the synthesis of magnetic seaweed (Ulva prolifera) biochar/sulfidated Fe0 composite (S-Fe0/BC) to use excessive seaweed biomass. Removal efficiency of tetrabromobisphenol A (TBBPA) reached up to 88% in iron-sulfur treatment. Two major products were identified as bisphenol A and monobromobisphenol A, confirming the in-situ reductive debromination of TBBPA. Batch experiments showed that the removal of TBBPA was facilitated with S/Fe molar ratio of 0.2 and acidic conditions (pH = 3–7). The S-Fe0/BC composite had good stability and reusability based on the cycle experiments. The removal process of TBBPA by S-Fe0/BC composite might include chemical adsorption by S-Fe0/BC composite, reduction debromination by S-Fe0 and enhanced electron transfer. The environmentally-friendly S-Fe0/BC composite synthesized by one-step facile procedure showed novel potential applications in terms of pollution control of halogenated xenobiotic compounds such as TBBPA.

Occurrence of bisphenol-A and its brominated derivatives in tributary and estuary of Xiaoqing River adjacent to Bohai Sea, China.

The chemical industrial zone located along the Xiaoqing River wetlands adjacent to Bohai Sea is one of the largest production bases for brominated flame retardants in China. Herein, high levels of bisphenol-A, tetrabromobisphenol-A (TBBPA), tribromobisphenol-A, dibromobisphenol-A, and monobromobisphenol-A were detected in sediment, soil, and water samples of this zone in the range of below method detection limit (<MDL)-5.45 × 106 ng/kg dw, <MDL-8.37 × 104 ng/kg dw, and <MDL-5.59 × 102 ng/L, respectively. They were mainly buried in sediments as their highest levels in sediment samples. The small concentration fluctuation between water samples retrieved in the upstream and downstream zones is likely attributed to seawater backflow. The nearby chemical factories were point pollution sources and the less brominated analogs are largely from debromination of TBBPA. High pollution levels and the ecological risks of these pollutants along the Xiaoqing estuary to Bohai Sea need to be further assessed in future studies.

Acetate promotes microbial reductive debromination of tetrabromobisphenol A during the startup phase of anaerobic wastewater sludge bioreactors

The detection of increasing concentrations of tetrabromobisphenol A (TBBPA) in wastewater treatment plants is raising concerns as TBBPA has been identified as a potentially toxic flame retardant. The objectives of this study were to evaluate the effect of acetate biostimulation on TBBPA microbial reductive debromination, and the response of anaerobic sludge associated microbial communities repeatedly exposed to TBBPA. Results indicate that the bulk of the microbial community did not experience significant shifts as a result of TBBPA exposure, and that only a small fraction of the community responded to the presence of TBBPA. Taxa most likely responsible for TBBPA transformation affiliated to Clostridiales and the wastewater sludge group Blvii28. The biostimulating effect of acetate was only observed during reactor startup, when acetogenesis was likely not yet occurring. However, when acetate likely started to be microbially generated in the reactor, acetate addition resulted in a slight but significant inhibiting effect on TBBPA transformation. A significant increase of hydrogenotrophic methanogens in the TBBPA-spiked reactor overtime implies that TBBPA degraders were not in direct competition with methanogens for H2. These results strongly suggest that TBBPA degrading taxa might have been primarily using acetate as an electron donor for the reductive debromination of TBBPA.

New insight into the cosolvent effect on the degradation of tetrabromobisphenol A (TBBPA) over millimeter-scale palladised sponge iron (Pd-s-Fe0) particles

The exploration of an effective treatment is necessary to eliminate the emerging environmental pollutant tetrabromobisphenol A (TBBPA). In this study, a direct reduction reaction was adopted to synthesize millimetre-scale palladised sponge iron (Pd0-s-Fe0), the main influencing factors were further explored, the degradation intermediates were identified in detail, and the cosolvent effect on the degradation mechanism was determined. The results show that (1) within a 30 min reaction, Pd(II) ions in aqueous solution were successfully decorated onto the s-Fe0 surface as supported by XPS, SEM, EDS, and ICP-OES analyses, (2) after 120 min of reaction, the normalized removal of TBBPA was ∼92.2% over 0.06 wt%-Pd0-s-Fe0, compared with 98.2% over 0.06 wt%-Pd-nZVI and 44.4% over bare nZVI. Moreover, the extend of debromination of TBBPA surprisingly increased as the ratio of the CH3OH:H2O cosolvent decreased, compared with the debromination rates that were greatly restricted in CH3OH (100%, v/v), CH2Cl2 (100%, v/v) and isopropanol (100%, v/v), respectively. Furthermore, the O-methylation reactions over Pd0-s-Fe0 produced unique intermediates, including 2,6-dibromo-4-(2-(3,5-dibromo-4-methoxyphenyl)propan-2-yl)phenol (MeO-TBBPA) and 5,5′-(propane-2,2-diyl)bis(1,3-dibromo-2-methoxy-benzene) (diMeO-TBBPA) with lower toxicity. This study greatly enriches knowledge regarding the degradation mechanism of TBBPA over millimetre-scale sponge iron.

Efficient debromination of Tetrabromobisphenol A (TBBPA) by Au/Fe@biocarbon derived from bioreduction precious metals

The utilization of nano zero valent iron is recognized as a potential approach for debromination of Tetrabromobisphenol A (TBBPA). In this study, Pycnoporus sanguineus cells were employed for biosupported Au nano particles (bio-AuNPs) preparation, then calcinated for obtaining porous carbon doped with Au nano particles (Au@biocarbon) and generated Au@biocarbon supported zero-valent iron nanoparticles (Au/Fe@biocarbon). The role of Au/Fe@biocarbon during debromination was evaluated by comparing with Au@biocarbon, biocarbon and Fe@biocarbon. Results showed that Fe0 and Au0 are successfully loaded on the surface of porous biocarbon with well-dispersion and higher specific surface area. The removal and debromination efficiency of TBBPA driven by Au/Fe@biocarbon was up to about 99.85% and 97.18% within 100min, respectively. Higher dosage and acidic condition were more beneficial to removal of TBBPA with the most appropriated Au/Fe molar ratio of 2%, where the complete removal of TBBPA only took 20min. The mechanism of TBBPA debromination by Au/Fe@biocarbon was the joint function of adsorption of biocarbon and galvanic cell of biosupported Au/Fe bimetals. Therefore, Au/Fe@biocarbon could be an alternative to effectively boost rapid and complete debromination of TBBPA.

Biochar and activated carbon act as promising amendments for promoting the microbial debromination of tetrabromobisphenol A

The increasing occurrence of tetrabromobisphenol A (TBBPA) in the environment is raising questions about its potential environmental health impacts as it has been shown to cause various deleterious effects in humans. The fact that the highest concentrations of TBBPA have been reported in wastewater sludge is concerning as effluent discharge and biosolids land application are likely a route by which TBBPA can be further disbursed to the environment. Our objectives in this study were to evaluate the effect of biochar (BC) and activated carbon (AC) in promoting the biodegradation of TBBPA, and characterize the response of anaerobic sludge microbial communities following amendments. Both carbonaceous amendments were found to promote the reductive debromination of TBBPA. Nearly complete transformation of TBBPA to BPA was observed in the amended reactors ∼20 days earlier than in the control reactors. In particular, the transformation of diBBPA to monoBBPA, which appears to be the rate-limiting step, was accelerated in the presence of either amendment. Overall, microbial taxa responding to the amendments, i.e., ‘sensitive responders’, represented a small proportion of the community (i.e., 7.2%), and responded positively. However, although both amendments had a similar effect on TBBPA degradation, the taxonomic profile of the sensitive responders differed greatly from one amendment to the other. BC had a taxonomically broader and slightly more pronounced effect than AC. This work suggests that BC and AC show great potential to promote the biodegradation of TBBPA in anaerobic sludge, and their integration into wastewater treatment processes may be helpful for removing TBBPA and possibly other emerging hydrophobic contaminants.

Degradation and debromination of bromophenols using a free-base porphyrin and metalloporphyrins as photosensitizers under conditions of visible light irradiation in the absence and presence of humic substances

The photodegradation and debromination of 2,4,6-tribromophenol (TrBP) and tetrabromobisphenol A (TBBPA) were investigated in the presence of a free-base porphyrin and metalloporphyrins as photosensitizers under conditions of visible light irradiation. Among the photosensitizers, 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin (H2TMPyP) and Zn(II)-tetrakis(N-methylpyridinium-4-yl)porphyrin (ZnTMPyP) were effective in the photodegradation of bromophenols. In particular, 96% of the debromination was achieved in the case of the ZnTMPyP photosensitization system for TBBPA after 24h of irradiation. ESR spectra with a spin-trapping reagent indicated that singlet oxygen (1O2) was the major photo-induced reactive oxygen species. The presence of humic substances and natural organic matter, which are common components in landfill leachates, inhibited the photodegradation of TrBP via competitive oxidation by 1O2 when ZnTMPyP was used as a photosensitizer. The presence of humic acids, which contained higher levels of electron-rich moieties like aromatic carbons, strongly inhibited the photodegradation of TrBP. TrBP and TBBPA were ultimately decomposed to organic acids, such as maleic and fumaric acids, as evidenced by LC/TOF-MS analysis. Thus, the photoirradiation of H2TMPyP and ZnTMPyP can induce 1O2 generation, which is effective in the photodegradation and debromination of TrBP and TBBPA.

Sodium persulfate-assisted mechanochemical degradation of tetrabromobisphenol A: Efficacy, products and pathway

In recent years, activated persulfate (PS) oxidation has been developed as a new advanced oxidation process for the degradation of organic pollutants. On the other hand, the mechanochemical method has exhibited a unique advantage in dealing with chemical wastes. The degradation of tetrabromobisphenol A (TBBPA), a widely used brominated flame retardant (BFR), in wastes has attracted considerable attention. In this study, the efficacy of a CaO-mechanochemical (CaO-MC) treatment system assisted by the addition of PS for the degradation of TBBPA was investigated. Under the optimum reaction conditions with a mole ratio of PS:CaO = 1:4 and less than 12.5% of TBBPA by mass, the degradation and debromination of TBBPA were completed within 2 h, while the mineralization was completed within 4 h. Characterization of the milled sample by XRD revealed that CaSO4 crystallization occurred. The TG results illustrate that there was little organic matter left after 4 h of milling. Raman and FT-IR spectra exhibited the TBBPA destruction process and disappearance of the organic groups. Through analysis by LC/MS/MS, seventeen intermediates were identified. The mechanism of TBBPA degradation by the PS-assisted CaO-MC treatment system was explained from two aspects, the course of crystallization and the degradation of TBBPA by activated PS, and two parallel initiation pathways were proposed.

A Novel Debromination of Tetrabromobisphenol A (TBBPA) by Hydrothermal Treatment with Reactive Minerals

Tetrabromobisphenol A (TBBPA) is widely used as a flame retardant and relatively persistent in the environment. There has been increasing interest in the developing alternative approach for its degradation and debromination. In this study, we explored the debromination of TBBPA by alkaline hydrothermal treatment with reactive minerals, namely iron powder, layered double hydroxide (LDH) and gibbsite. The effects of hydrothermal temperatures and time, the initial TBBPA concentrations, and additive amounts of reactive minerals on debromination were investigated. As a comparison, the conventional hydrothermal treatment with no additive as the control group was included. The UV-vis absorption spectra of TBBPA before and after debromination were studied as well. The results showed that increasing temperature was helpful for the improvement of debromination. It significantly increased by 223.5, 54.3 and 78.1% with increasing temperature from 140 to 160 °C for the control, iron power and LDH groups, respectively. When the hydrothermal time was shorter than a critical value, the debromination rate increased with time rising. A maximum rate of 79.9% was achieved for iron powder group after reaction for 8 h. The preferred initial TBBPA concentration was determined as 60 ppm for all groups. The optimum amounts of reactive minerals were not consistent and determined as 0.08 g for iron powder, 0.32 g for LDH and 0.16 g for gibbsite, respectively. The maximum absorption bands of TBBPA increased as the pH was raised. They were located at 209 and 308 nm for neutral TBBPA and increased to 211 and 311 nm for TBBPA-Na2CO3. New absorption bands in the wavelength region of 225-275 and 300-350 nm were observed, when TBBPA was subjected to hydrothermal treatment. Keywords: Brominated flame retardants (BFRs); tetrabromobisphenol A (TBBPA); debromination; hydrothermal treatment; UV-vis absorption spectra

Electrochemical Reduction of 2,2′,6,6′-Tetrabromobisphenol A at Silver Cathodes in Dimethylformamide

2,2′,6,6′-Tetrabromobisphenol A (TBBPA) is a brominated flame retardant that is bonded chemically to epoxy resins in circuit boards and that is added to high-impact polystyrenes. TBBPA is found ubiquitously throughout the environment in sewage runoffs and in water and soil samples, as well as in living organisms. There have been many documented methods for the degradation of TBBPA, including both chemical and physical methods. In this study we have focused on the electrochemical degradation of TBBPA at silver electrodes in dimethylformamide (DMF) containing 0.10 M tetramethylammonium tetrafluoroborate (TMABF4). Initially, cyclic voltammograms were recorded to characterize the electrochemical behavior of TBBPA at both glassy carbon and silver cathodes, as shown in the accompanying figure. At glassy carbon, only two irreversible cathodic peaks are observed. On the other hand, reduction of TBBPA at a silver cathode gives rise to three cathodic peaks, which appear at potentials significantly more positive than for glassy carbon. To investigate the possible debromination of TBBPA, controlled-potential (bulk) electrolyses have been performed with a silver gauze electrode in a DMF–0.10 M TMABF4. Using GC–MS for the separation, identification, and quantitation of products arising from bulk electrolyses, we have determined that mixtures of mono-, di-, and tribrominated species are produced. Figure 1

Characteristics, sources, and transport of tetrabromobisphenol A and bisphenol A in soils from a typical e-waste recycling area in South China

We studied the tetrabromobisphenol A (TBBPA) and bisphenol A (BPA) patterns and their sources and transport in different land-use soils from Longtang, South China, a typical electronic waste recycling center. We also studied the reductive debromination of TBBPA in paddy soils. TBBPA and BPA concentrations (on a dry weight basis) were undetected-220 and 0.50-325ng/g, respectively, and both increased, by similar factors, in the following order: pond sediments < paddy soils = vegetable soils < wasteland < dismantling sites < former open burning sites. BPA concentrations were higher than TBBPA concentrations in all six land-use soils, and they correlated significantly. TBBPA and BPA were transported through the soil profiles, being found at relatively high concentrations in soil 0-40cm deep, but only at low concentrations in soil 40-80cm deep. The surface soil concentrations appear to have been strongly affected by crude recycling activities, and former open burning and dismantling sites were the main point sources. The areas surrounding the open burning sites and dismantling sites have been contaminated not only by the dumping of waste residues but also by fly ash deposition, even though the agricultural soils are far from the point pollution sources. Some BPA in the soils is likely to be the reductive debromination product of TBBPA because the long rainy season promotes TBBPA transformation and because BPA can persist for a long time. Incubation experiments confirmed that TBBPA could be transformed into BPA and that BPA could accumulate in waterlogged paddy soils, and this may be why BPA concentrations were higher than TBBPA concentrations in the Longtang area.

Fate of lead oxide during thermal treatment with tetrabromobisphenol A

In this paper, the bromination reaction between lead oxide and hydrogen bromide originating from the thermal decomposition of tetrabromobisphenol A (TBBPA), under inert and oxidizing atmospheres, was investigated, using a laboratory-scale furnace. The results obtained under inert conditions indicated that bromination of PbO proceeded simultaneously with debromination of TBBPA, with an average effectiveness of 69% (max. 80%). Volatilization of the formed PbBr2 began at 315°C, intensified at 750°C, and reached 98% at 850°C. The formed organic char served as a source of carbon for reduction of the unreacted lead oxide to metallic lead in the range 315–750°C. Additional experiments conducted at selected temperatures under slightly oxidizing (5vol% O2) and quasi-atmospheric (20vol% O2) conditions showed no significant effects on bromination–evaporation of lead in the studied mixture. However, in isothermal treatment under quasi-atmospheric oxygen levels, complete vaporization of the formed lead bromide was obtained at a temperature of only 650°C.