Degradation Of Decabromodiphenyl Ether Research Articles

Degradation processes of brominated flame retardants dispersed in high impact polystyrene under UV-visible radiation.

In order to protect human health and the environment, several regulations have been introduced in recent years to reduce or even eliminate the use of some brominated flame retardants (BFRs) due to their toxicity, persistence and bioaccumulation. Dispersions of these BFRs in polymers are widely used for various applications. In this report, four different brominated molecules, decabromodiphenyl ether (DBDE), hexabromocyclododecane (HBCDD), decabromodiphenyl ethane (DBDPE) and tris(tribromophenoxy)triazine (TTBPT), were dispersed in the solid matrix of an industrial polymer, high impact polystyrene (HIPS). The possibility of degradation of these BFRs within HIPS under UV-visible irradiation in ambient air was investigated. The degradation kinetics of DBDE and HBCDD were followed by Fourier transform infrared spectroscopy (FTIR) and high-resolution two-step laser mass spectrometry (L2MS). The thermal properties of the pristine and irradiated polymer matrix were monitored by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), which showed that these properties were globally preserved. Volatile photoproducts from the degradation of DBDE, DBDPE and TTBPT were identified by headspace gas chromatography/mass spectrometry analysis. Under the chosen experimental conditions, BFRs underwent rapid degradation after a few seconds of irradiation, with conversions exceeding 50% for HIPS/DBDE and HIPS/HBCDD systems.

Comparison of decabromodiphenyl ether degradation in long-term operated anaerobic bioreactors under thermophilic and mesophilic conditions and the pathways involved

Anaerobic digestion of decabromodiphenyl ether was carried out and compared in two continuously stirred anaerobic bioreactors for 210 days under thermophilic and mesophilic conditions. Results show that the degradation of decabromodiphenyl ether followed the first-order reaction kinetics, which exhibited a higher removal rate in the thermophilic reactor when compared to the mesophilic one, reaching its maximum of 1.1 μg·day−1. The anaerobic digestion of decabromodiphenyl ether was found to involve the replacement of bromines from polybrominated diphenyl ether by hydrogen atoms, gradually forming nona-, octa- and hepta-brominated diphenyl ether, respectively. Under the thermophilic condition, the reactors were dominated by Bacillus sp. and Methanosarcina sp. with high bioactivity and high concentrations of debromination microorganisms.

The degradation of decabromodiphenyl ether in the e-waste site by biochar supported nanoscale zero-valent iron /persulfate

Biochar supported nano zero-valent iron (BC-nZVI) synthesized through liquid phase reduction method was used to activate persulfate (PS) for the removal of decabromodiphenyl ether (BDE209) in the soil. The morphology, structure and composition of BC-nZVI were determined by SEM, XRD, XPS and FTIR. Batch experiments were carried out to investigate the effect of different factors, such as the molar ratio of PS to BC-nZVI, pH value of PS solution and reaction temperature, on the degradation efficiency of BDE209. Results showed that when the molar ratio of PS/BC-nZVI was 3:1, pH value was 3, reaction temperature was 40 °C, 82.06% of BDE209 could be removed within 240 min. The process fitted pseudo-first-order kinetics model well and the apparent activation energy (Ea) was 48.92 kJ mol−1, indicating that the process was controlled by surface reaction. The quenching experiments showed that ·SO4− was predominate radical species in the degradation process in acid and neutral condition. However, ·OH played more important role in alkaline condition. GC-MS was used to determine the reaction products for inferring the degradation pathway of BDE209 in soil by BC-nZVI/PS system.

Degradation of decabromodiphenyl ether (BDE-209) in microcosms mimicking sediment environment subjected to comparative bioremediation strategies

The aim of this study was to examine bioremediation strategies for BDE-209 contaminated sediments. Sediment microcosms were established to observe anaerobic debromination of BDE-209 under conditions representing three bioremediation strategies: biostimulation, bioaugmentation and natural attenuation. To simulate biostimulation, a defined mineral medium containing both a carbon source (sodium formate) and electron donor (ethanol) was added into sediments. Bioaugmentation was established by enrichment of the sediments using a culture of Dehalobium chlorocoercia strain DF-1, previously shown to dechlorinate polychlorinated biphenyls, to sediments. No amendments were made to the third set in order to represent natural attenuation. The biostimulation, bioaugmentation and natural attenuation strategies resulted in 55.3%, 40.2% and 30.9% reductions in BDE-209, respectively, after 180 days. Nona- through tri-BDEs were observed as products, with 17 PBDE congeners detected in 25 different proposed debromination pathways. At the end of the 180 day incubation period, the products for bioaugmentation, biostimulation and natural attenuation were tri-BDEs, tetra-BDEs and penta-BDEs, respectively. The proposed pathways revealed that meta- and ortho-Br removal were favored in sediments, and that debromination regiospecificity varied with each bioremediation strategy applied. Lastly, pseudo-first-order rate constants for BDE-209 reduction were calculated as 0.0049 d−1, 0.0028 d−1, 0.0025 d−1 for biostimulation, bioaugmentation and natural attenuation, respectively.

Identification Influence Mechanism of Humic Acid in the Degradation of Decabromodiphenyl Ether by the BC@Ni/Fe Nanoparticles

Identification Influence Mechanism of Humic Acid in the Degradation of Decabromodiphenyl Ether by the BC@Ni/Fe Nanoparticles

Effect of solvent on debromination of decabromodiphenyl ether by Ni/Fe nanoparticles and nano zero-valent iron particles.

Nano zero-valent iron (nZVI) and its modified nanomaterials are widely used in the degradation of some halogenated organic pollutants. In this study, we explored the effects of different proportions of tetrahydrofuran (THF) (50, 60, 70, 80, 90, and 100%) on the degradation of decabromodiphenyl ether (BDE209) by Ni/Fe and nZVI nanoparticles with reference to the degradation kinetics, products, and pathway. The results illustrated that the effects of solvent on the degradation of BDE209 were similar when the two kinds of nanomaterials were used, although the Ni/Fe bimetallic nanoparticles exhibited a better catalytic activity compared with the pure nZVI during the degradation of BDE209. The apparent reaction rate constant (k obs) increased with the proportion of the water in the system, enhancing the degradation of BDE209. In terms of degradation products, a high proportion of THF led to an accumulation of higher-brominated BDEs, inhibiting the further debromination of BDE209. The inhibitory effect of the solvent (THF) can be explained that water played a role of hydrogen donor during the reductive degradation of BDE209 in the THF/water system. However, the proportion of THF in the degradation system posed no effect on the BDE209 debromination pathway and debromination location. The difficulty of para-debromination was observed in all of the solvent systems.

Biosorption and degradation of decabromodiphenyl ether by Brevibacillus brevis and the influence of decabromodiphenyl ether on cellular metabolic responses.

There is global concern about the effects of decabromodiphenyl ether (BDE209) on environmental and public health. The molecular properties, biosorption, degradation, accumulation, and cellular metabolic effects of BDE209 were investigated in this study to identify the mechanisms involved in the aerobic biodegradation of BDE209. BDE209 is initially absorbed by wall teichoic acid and N-acetylglucosamine side chains in peptidoglycan, and then, BDE209 is transported and debrominated through three pathways, giving tri-, hepta-, octa-, and nona-bromodiphenyl ethers. The C-C bond energies decrease as the number of bromine atoms on the diphenyl decreases. Polybrominated diphenyl ethers (PBDEs) inhibit protein expression or accelerate protein degradation and increase membrane permeability and the release of Cl(-), Na(+), NH4 (+), arabinose, proteins, acetic acid, and oxalic acid. However, PBDEs increase the amounts of K(+), Mg(2+), PO4 (3-), SO4 (2-), and NO3 (-) assimilated. The biosorption, degradation, accumulation, and removal efficiencies when Brevibacillus brevis (1 g L(-1)) was exposed to BDE209 (0.5 mg L(-1)) for 7 days were 7.4, 69.5, 16.3, and 94.6 %, respectively.

Transport of nano zero-valent iron supported by mesoporous silica microspheres in porous media.

Effective in situ remediation of groundwater requires the successful delivery of reactive iron particles through sand. However, the agglomeration of nano zero-valent iron (NZVI) particles limits the migration distance, which inhibits their usefulness. In the study described herein, NZVI supported by mesoporous silica microspheres covered with FeOOH (SiO2@FeOOH@Fe) was synthesized, and its mobility was demonstrated on the basis of transport in porous media. Degradation of decabromodiphenyl ether (BDE209) was more efficient by SiO2@FeOOH@Fe than by 'bare' NZVI. Breakthrough curves and mass recovery showed the mobility of SiO2@FeOOH@Fe in granular media was better than that of bare NZVI. It increased greatly in the presence of natural organic matter (NOM) and decreased when high Ca2+ and Mg2+ concentrations were encountered. Analysis of the transport data on the basis of filtration theory showed diffusion to be the main mechanism for particle removal in silicon sand. Increasing the NOM may decrease agglomeration of the grains of sand, which has a positive effect on the mobility of SiO2@FeOOH@Fe. Presumably, increasing the concentrations of Ca2+ and Mg2+ compresses the diffuse double layer of SiO2@FeOOH@Fe, resulting in a reduction of mobility.

Effect of cadmium ion on biodegradation of decabromodiphenyl ether (BDE-209) by Pseudomonas aeruginosa

The influence of Cd(II) ions on the degradation of decabromodiphenyl ether (BDE-209) by an aerobic degrading strain, Pseudomonas aeruginosa, was investigated. The results demonstrated that the strain P. aeruginosa exhibited a high level of resistance against cadmium toxicity, and Cd(II) ions of different concentrations possessed mixed reactions on BDE-209 bioremoval. The degradation efficiency was stimulated at low concentrations of Cd(II) ions (≤1mgL−1) but inhibited at higher levels (≥5mgL−1). Subsequent analyses revealed that the increase of cell hydrophobicity and membrane permeability were two main factors for Cd(II) ions of low concentrations to accelerate BDE-209 degradation. However, inhibition effect by high concentrations of Cd(II) ions was mainly attributed to the negative impact of metals on growth and metabolism of the strain. It was also showed through cellular distribution of BDE-209 that different concentration of Cd(II) ions affected the amount of BDE-209 inside or outside the cell at different incubation time.

The Degradation of Decabromodiphenyl Ether in the Supercritical Fluid

Currently, environmental contamination by polybrominated diphenyl ethers (PBDEs) in the world is of important concern and requires the effective remediation technologies. The degradation of decabromodiphenyl ether (BDE-209) in the supercritical n-hexane by zerovalent iron was studied in this work. The results showed that BDE-209 can be rapidly reduced into nona-, octa-, hepta-and lower brominated polybrominated diphenyl ethers (PBDEs) under the supercritical reaction conditions. Among n-hexane, methanol, tetrahydrofuran and mixed n-hexane+ tetrahydrofuran solvents, the conversion of BDE-209 in tetrahydrofuran was the highest. BDE-209 conversion increased with increased reaction temperature and pressure. Under the reaction condition: temperature: 523K; pressure: 3.2Mpa; reaction time: 10min; reaction system: 200ml 50mg BDE-209/L n-hexane; atmosphere: N2and catalyst load: 2g/L, the conversion of BDE-209 was as high as 88.9%.

Efficient total analyses for bromine type flame retardants by simple NICI-GC/MS

We studied an efficient analytical method for detecting brominated aromatic compounds using negative ion chemical ionization (NICI), with well-known quadruple gas-chromatography mass-spectrometry (GC/MS). We utilized 79 and 35 m/z as monitoring ions of brominated compounds and syringe-spiked PCB#209, thus highly selective and sensitive detection was achieved. With 7.0 m long HP-5 GC column, decabromo-diphenyl ether (DBDE), hexabromobenzene, α-hexabromo cyclododecane (α-HBCD), and tetrabromo bisphenol A were utilized as bromine type flame retardants that are generally consumed in industrial commodities. A shorter column provided more efficient results without degradation of DBDE on GC which are usually observed with longer column (30 m). Also, pseudo environmental water samples can be analyzed without authentic pretreatment procedures. Furthermore, we demonstrated analyses for members regulated by the Restriction of Hazardous Substances. Consequently, the newly developed simple NICI-GC/MS method was effectively worked for screening of flame retardants in a short period of time.

Synergistic effect of microscale zerovalent iron particles combined with anaerobic sludges on the degradation of decabromodiphenyl ether

Polybrominated diphenyl ethers (PBDEs) are widely used flame retardants. Owing to their toxicity and increasing accumulation in the environment, the fate of PBDEs in nature is of serious concern. The combined effects of microscale zerovalent iron (MZVI) and anaerobic sludge in decabromodiphenyl ether (BDE-209) degradation were investigated. The co-incubation resulted in 63% and 29% enhancement of removal ability when compared to the single component conditions. By-products generated during the entire process followed a stepwise sequence with non-uniform accumulation rates. Microbes hindered the accessibility of MZVI to BDE-209 and reduced the removal ability in the initial stage (<12h). According to the analysis of the microbial community change, co-incubation with MZVI leads to the enrichment of heterotrophic microbial populations bearing nitrate- or iron-reducing activities. The interaction between MZVI and microbes contributed to the synergistic effect. Our findings provide evidence for this synergistic effect and offer an alternative for developing better remediation strategies.

TG–MS investigation of brominated products from the degradation of brominated flame retardants in high-impact polystyrene

The thermal degradation of flame retardant containing high-impact polystyrene (HIPS–Br), one of the most commonly employed plastics in electric and electronic appliances, was examined by thermogravimetry coupled with mass spectroscopy (TG–MS) in order to understand the threat that is posed by the release of hazardous brominated compounds. The HIPS samples contained decabromodiphenylether (DPE) and decabromodibenzyl (DDB) as the flame retardants as well as Sb2O3 as the synergist. The largest number of brominated compounds was obtained in the presence of DPE and Sb2O3 and DDB without Sb2O3. From the degradation of DPE, brominated benzenes, phenols, diphenylethers, and dibenzofurans were identified, and from the degradation of DDB, brominated benzenes, dibenzyls, and phenanthrenes were formed. The interaction between the flame retardant and the polymer matrix resulted in α-bromoethylbenzene. The formation of brominated dibenzodioxins was not observed, probably, due to the low phenol concentration in the polymer melt. No other report has, to our knowledge, ever reported on the formation of brominated phenanthrenes from flame retardants. Because they share similar steric features, it may well be that brominated phenanthrenes are similar in their carcinogen and mutagen potential to dibenzofurans and dibenzodioxins. A plausible mechanism for the formation of the observed compounds is presented, and the role of the synergist is considered.

Degradation of decabromodiphenyl ether by nano zero-valent iron immobilized in mesoporous silica microspheres

The agglomeration of nanoparticles reduces the surface area and reactivity of nano zero-valent iron (NZVI). In this paper, highly dispersive and reactive NZVI immobilized in mesoporous silica microspheres covered with FeOOH was synthesized to form reactive mesoporous silica microspheres (SiO 2@FeOOH@Fe). The characteristics of SiO 2@FeOOH@Fe were analyzed by transmission electron microscopy, Fourier transform infrared spectroscopy simultaneous thermal analysis, X-ray photoelectron spectroscopy, and Brunnaer–Emmett–Teller surface area analysis. The mean particle size of the reactive mesoporous silica microspheres was 450 nm, and its specific surface area was 383.477 m 2 g −1. The degradation of dcabromodiphenyl ether (BDE209) was followed pseudo-first-order kinetics, and the observed reaction rate constant could be improved by increasing the SiO 2@FeOOH@Fe dosage and by decreasing the initial BDE209 concentration. The stability and longevity of the immobilized Fe nanoparticles were evaluated by repeatedly renewing the BDE209 solution in the reactor. The stable degradation of BDE209 by SiO 2@FeOOH@Fe was observed within 10 cycles. Agglomeration-resistance and magnetic separation of SiO 2@FeOOH@Fe were also performed. The improved dispersion of SiO 2@FeOOH@Fe in solution after one-month storage and its good performance in magnetic separation indicated that SiO 2@FeOOH@Fe has the potential to be efficiently applied to environmental remediation.

Characterization and the photocatalytic activity of TiO 2 immobilized hydrophobic montmorillonite photocatalysts : Degradation of decabromodiphenyl ether (BDE 209)

A novel TiO 2 immobilized hydrophobic montmorillonite photocatalysts were designed and prepared for the advanced oxidation of persistent organic pollutants in water, which combined the pre-adsorption and concentrated effects for aqueous micro-organic pollutants with the photocatalytic destruction of organic pollutants. The photocatalysts were synthesized by immobilizing TiO 2 onto surfactant-pillared montmorillonite via ion exchange reaction between sodium montmorillonite with cation surfactant, cetyl trimethyl ammonium bromide (CTMAB). The Degussa P25 catalyst loading amounts varied between 20 and 80%. The composition and texture of the prepared composites were characterized with X-ray powder diffraction, scanning electron microscope, and energy-dispersive spectrometry. The adsorption performance and photocatalytic activities of prepared composite photocatalysts were evaluated using decabromodiphenyl ether (BDE 209) as a model pollutant in aqueous solution. The results were found that these composite photocatalysts can effectively degrade BDE 209, and the complete removal can be achieved within 180 min of irradiation. The removal efficiency of BDE 209 increased with the percentage of immobilized TiO 2 on the hydrophobic clay. Highly hydrophobic substrates (BDE 209) can effectively adsorb (concentrate) in or near the hydrophobic surfactant regions of TiO 2 immobilized CTMAB-pillared montmorillonite photocatalysts. The degradation pathways involving photochemical debromination and hydroxyl radical addition are proposed based on the identification of specific by-products.

Effect of Tween 80 and β-cyclodextrin on degradation of decabromodiphenyl ether (BDE-209) by White Rot Fungi

The environmental safety of decabromodiphenyl ether (BDE-209), a widely used flame retardant, has been the topic of controversial discussions during the past several years. Degradation of BDE-209 into lower brominated diphenyl ether congeners, exhibiting a higher bioaccumulation potential, has been a critical issue. White rot fungi are known to degrade a wide variety of recalcitrant pollutants. In this work, white rot fungi were used to degrade BDE-209 in liquid culture medium, and the effects of Tween 80 and β-cyclodextrin on BDE-209 degradation by white rot fungi were evaluated. On the basis of these results, it appears that BDE-209 could be degraded by white rot fungi, and Tween 80 and β-cyclodextrin can both increase the biodegradation. The best result in Tween 80 experiments was obtained at a Tween 80 concentration of 500 mg l −1 within 10 d, which showed 96.5% (w/w) BDE-209 transformed. Tween 80 at a high concentration will restrain the fungal growth and the degradation of BDE-209. However, β-cyclodextrin had positive effects both on the BDE-209 degradation and the fungal growth.