Removal Of Polybrominated Diphenyl Ethers Research Articles

Toward integrated detection and graphene-based removal of contaminants in a lab-on-a-chip platform

A novel, miniaturized microfluidic platform was developed for the simultaneous detection and removal of polybrominated diphenyl ethers (PBDEs). The platform consists of a polydimethylsiloxane (PDMS) microfluidic chip for an immunoreaction step, a PDMS chip with an integrated screen-printed electrode (SPCE) for detection, and a PDMS-reduced graphene oxide (rGO) chip for physical adsorption and subsequent removal of PBDE residues. The detection was based on competitive immunoassay-linked binding between PBDE and PBDE modified with horseradish peroxidase (HRP-PBDE) followed by the monitoring of enzymatic oxidation of o-aminophenol (o-AP) using square wave anodic stripping voltammetry (SW-ASV). PBDE was detected with good sensitivity and a limit of detection similar to that obtained with a commercial colorimetric test (0.018 ppb), but with the advantage of using lower reagent volumes and a reduced analysis time. The use of microfluidic chips also provides improved linearity and a better reproducibility in comparison to those obtained with batch-based measurements using screen-printed electrodes. In order to design a detection system suitable for toxic compounds such as PBDEs, a reduced graphene oxide–PDMS composite was developed and optimized to obtain increased adsorption (based on both the hydrophobicity and π–π stacking between rGO and PBDE molecules) compared to those of non-modified PDMS. To the best of our knowledge, this is the first demonstration of electrochemical detection of flame retardants and a novel application of the rGO-PDMS composite in a biosensing system. This system can be easily applied to detect any analyte using the appropriate immunoassay and it supports operation in complex matrices such as seawater.

Insight into the long-term effect of mangrove species on removal of polybrominated diphenyl ethers (PBDEs) from BDE-47 contaminated sediments

Polybrominated diphenyl ethers (PBDEs) have become ubiquitous environmental contaminants, particularly in mangrove wetlands. However, little is known about the long-term effect of mangrove plants on PBDE removal from contaminated sediments. A 12-month microcosm experiment was conducted to understand the effect of two mangrove species, namely Avicennia marina (Am) and Aegiceras corniculatum (Ac), on PBDE removal from the sediments spiked with 2000ngg−1 dry weight of BDE-47, and to explore the microbial mechanism responsible for the planting-induced effects on BDE-47 removal. Results showed that planting of mangrove species, either Am or Ac, could accelerate BDE-47 removal from contaminated sediments during the 12months experiment, mainly through enhancing microbial degradation process. In particular, Am sediment had significantly higher BDE-47 degradation efficiency compared with Ac sediment, which may be mainly attributed to higher activities of urease and dehydrogenase, as well as higher 16S rRNA gene copies of total bacteria and organohalide-respiring bacteria (OHRB) in Am sediment. Moreover, planting could shift sediment bacterial community composition and selectively enrich some bacterial genera responsible for PBDE degradation. Such selective enrichment effect of Am on the potential PBDE-degrading bacteria differed distinctly from that of Ac. These results indicated that long-term planting of mangrove species, especially Am, could significantly promote BDE-47 removal from the contaminated sediments by enhancing microbial activity, increasing total bacterial and OHRB abundances and altering bacterial community composition.

Removal of polybrominated diphenyl ethers by biomass carbon-supported nanoscale zerovalent iron particles: influencing factors, kinetics, and mechanism.

In this study, nanoscale zerovalent iron (NZVI) immobilized on biomass carbon was used for the high efficient removal of BDE 209. NZVI supported on biomass carbon minimized the aggregation of NZVI particles resulting in the increased reaction performance. The proposed removal mechanism included the adsorption of BDE 209 on the surface or interior of the biomass carbon NZVI (BC-NZVI) particles and the subsequent debromination of BDE 209 by NZVI while biomass carbon served as an electron shuttle. BC-NZVI particles and the interaction between BC-NZVI particles and BDE 209 were characterized by TEM, XRD, and XPS. The removal reaction followed a pseudo-first-order rate expression under different reaction conditions, and the k obs was higher than that of other NZVI-supported materials. The debromination of BDE 209 by BC-NZVI was a stepwise process from nona-BDE to DE. A proposed pathway suggested that supporting NZVI on biomass carbon has potential as a promising technique for in situ organic-contaminated groundwater remediation.

Removal of decabromodiphenyl ether (BDE-209) using a combined system involving TiO2 photocatalysis and wetland plants

There is a rising concern about the capability of sewage treatment works in treating emerging chemicals, such as polybrominated diphenyl ethers (PBDEs). A combined photocatalysis (TiO2 and visible light) and constructed wetland system (planted with Oryza sativa (rice cultivar: Hefengzhan) and Phragmites australis (common reed)) was designed to study PBDEs removal efficiencies. After the pre-treatment in TiO2 suspension, the artificially BDE-209 spiked sewage (78.2 and 782nmol/L) was discharged into the sub-surface flow constructed wetland tanks planted with rice and common reed, respectively. The treated sewage, soil, plant roots, shoots, rice grains and hulls were collected and analyzed for PBDEs by GC–MS. The removals of BDE-209 in the combined systems (93.6±2.19% (78.2nmol/L) and 92.1±1.11% (782nmol/L)) were significantly higher than those in the photocatalytic systems (56.3±5.78% (78.2nmol/L) and 54.7±9.47% (782nmol/L)), which could be explained by the enhanced biodegradability of PBDEs in photocatalysis, led to its better dissipation by rice plants. Therefore, this combined system might help to degrade BDE-209 in the wastewater effluent, reducing its potential entry into aquatic food chains.

Anaerobic biodegradation of decabromodiphenyl ether (BDE-209)-contaminated sediment by organic compost

Polybrominated diphenyl ethers (PBDEs), commonly used as a flame retardants for industrial and commercial products, have a strong tendency to accumulate in the interface of water/soil/sediments and are difficult to biodegrade. An effective biological treatment for PBDE removal is needed. In this study, we investigated the use of 3 organic compost materials (BM-2, BM-6, and BP-2) to remove 20 mg kg−1 decabromodiphenyl ether (BDE-209) from contaminated sediment in anaerobic microcosms for 120 days and detected the bacterial community in samples. Organic substance of compost had sorption and biodegradation ability. BM-6 showed the highest sorption of BDE-209, at 38.95%, and BM-3 the highest biological activity, at 34.90%. Methylophilus spp., Pseudomonas spp., Clostridium spp., and Dehalococcoides sp. were identified in anaerobic microcosms with PBDE biodegradation. The pathway of anaerobic DBDE biodegradation from higher to lower brominated PBDE was identified by the appearance of PBDE biometabolites and functional genes related to reductive debromination. We have identified an effective approach for bioremediating PBDE-contaminated sediment by using organic compost; this approach is highly recommended for practical engineering for off-site remediation.

A novel technology for remediation of PBDEs contaminated soils using tourmaline-catalyzed Fenton-like oxidation combined with P. chrysosporium

We carried out the 70-day remediation process for soil contaminated polybrominated diphenyl ethers (PBDEs) using a novel technology, a tourmaline catalyzed Fenton-like reaction (TCFR) combined with Phanerochaete chrysosporium (TCFR+P) in field soil microcosms. The results showed that the TCFR is more efficient in removing PBDE compounds with lower numbers of bromine (Br) atoms such as BDE-28, BDE-47, BDE-99, BDE-100, while the TCFR+P is a good method to remove the PBDEs with greater number of Br atoms. For the total PBDE removal from soil, the TCFR was more efficient than that in the soil added TCFR+P. SEM analysis showed that lower PBDE removal using TCFR+P may be due to the mycelium produced by P. chrysosporium covering the humin (HM) surface, thereby decreasing the effective contact between hydroxyl radicals (OH) and PBDEs. Moreover, a systemic series of experiments on the effects of the TCFR and TCFR+P on soil pH, soil organic matter (SOM) content, humic acid (HA) and HM compositions and structure, soil fungi, and degradation pathways were designed to discuss the removal mechanisms of the TCFR and the TCFR+P. Both of the TCFR and the TCFR+P caused a decrease in the SOM contents, a decline in aromaticity, an increase in surface hydrophilicity, an improvement in the polarity index of HA and HM, and an unexpected increased ergosterol content, compared to that of the soil added H2O2, tourmaline or P. chrysosporium alone, which in turn, enhanced the removal of PBDEs. Additionally, the five and nine oxidation degradation products of BDE-47, -153, respectively, were analyzed by LC–MS/MS. To the best of our knowledge, this study is the first report demonstrating that PBDEs in soil can be removed through TCFR oxidization.

Isolation of microalgae tolerant to polybrominated diphenyl ethers (PBDEs) from wastewater treatment plants and their removal ability

The present study isolated microalgae with tolerance to polybrominated diphenyl ethers (PBDEs) from wastewater aiming to discover isolates with high removal abilities. Nine isolates, Chlorella (STCh and SICh), Parachlorella (STPa1 and STPa2), Scenedesmus (STSc, TPSc1 and TPSc2), Nitzschia palea (YLBa) and Mychonastes (TPMy), were obtained. Four isolates, SICh, STCh, STPa1 and TPSc1, were very tolerant, and their growth was not affected by DE-71 and BDE-209 mixtures (5:1) at low (6μgL−1), medium (60μgL−1) or even high (600μgL−1) levels for 7days. The removal of PBDEs by one of the tolerant isolates, SICh, was the highest, with 82–90% removal at the end of 7-days exposure. SICh also accumulated more PBDEs than the other isolates. Bioaccumulation and biotransformation were important for PBDE removal. This is the first study isolated PBDE-tolerant microalgae from wastewater and obtained a Chlorella isolate, SICh, with high tolerance and removal ability.

Temporal and spatial contamination of polybrominated diphenyl ethers (PBDEs) in wastewater treatment plants in Hong Kong

Polybrominated diphenyl ethers (PBDEs) are widely used as flame retardants which cause adverse effects to human health and environments. Wastewater treatment plants (WWTPs) receive PBDEs from various discharges but also release them back to the environment via treated effluent and sludge, depending on the removal efficiency of WWTPs. This study investigated the contamination of PBDEs in primary influent, final effluent and dewatered sludge in four WWTPs in Hong Kong from October 2011 to January 2013. Results showed that the concentrations and composition profiles of eight PBDE congeners (BDE-28, －47, －99, －100, －153, －154,－183 and －209) differed among WWTPs and fluctuated during the study period. Higher concentrations of PBDEs were detected in the influent and dewatered sludge from the two WWTPs receiving both domestic and industrial wastewaters than the two serve mainly residential and commercial districts. However, the PBDE concentrations in the effluent were comparable among WWTPs. The concentrations of Σ8PBDEs (total of eight congeners) in the influent of all WWTPs ranged from 1 to 254ngL−1 but decreased to 12–27ngL−1 in effluent, with removal efficiency ranged from 20 to 53%. High concentrations of PBDEs, ranging from 9 to 307ngg−1 dry weights, were detected in dewatered sludge. The predominated congeners in influent were BDE-47 and −209 but shifted to BDE-47 and －99 in effluent and BDE-209 in dewatered sludge. Every day, it is estimated 0.66–73g PBDEs entered the four WWTPs, while 0.38–38g and 0.17–17g PBDEs were discharged to the surrounding waters via effluent and disposed to landfill sites in sludge form, respectively. These results indicated that the four WWTPs in Hong Kong were not designed for effectively removal of PBDEs, 52–80% of the incoming PBDEs were still remained in effluent and 21–45% was precipitated in sludge, both outputs became significant contamination sources.

Seasonal deposition fluxes and removal efficiency of atmospheric polybrominated diphenyl ethers in a large urban center: importance of natural and anthropogenic factors.

Wet deposition is an effective and important mechanism for removal of atmospheric pollutants, particularly in urban regions. To examine the effectiveness of natural and anthropogenic factors in such removal mechanisms, we conducted a study in Guangzhou, a mega metropolitan center in South China. Rainwater and dry particle deposition samples were simultaneously collected from Guangzhou during the entire year of 2010, and analyzed for polybrominated diphenyl ethers (PBDEs), a group of pollutants mainly derived from industrial and household consumer products. Concentrations of ΣPBDE (sum of the 21 congeners of PBDEs) and BDE-209 in wet deposition samples ranged from 0.11 to 640 (average: 23 ± 36 ng L(-1)) and 0.071 to 420 (average: 20 ± 31 ng L(-1)), respectively. Assessed by conditional inference tree, particulate matter was recognized as the most important factor controlling concentration levels of PBDEs. The combined wet and dry deposition flux of ΣPBDE (1.4 (± 1.2) × 10(4) ng m(-2) quarter(-1)) in the first quarter of 2010 was not significantly different from that (1.3 (± 0.46) × 10(4) ng m(-2) quarter(-1)) in the fourth quarter, indicating that source control measures implemented by local governments for the 16th Asian Games and 10th Asian Para Games (held in November and December 2010, respectively) were ineffective in reducing the loadings of atmospheric PBDEs. In addition, the lower removal efficiency of ΣPBDE was found in the fourth quarter compared to other quarters. This result suggested that rain interventions conducted to maintain clear weather conditions for the Asian Games turned out to lower the efficacy for removal of PBDEs by wet deposition.

Remediation of polybrominated diphenyl ethers in soil using Ni/Fe bimetallic nanoparticles: Influencing factors, kinetics and mechanism

Polybrominated diphenyl ethers (PBDEs) are commonly used as additive flame retardants in all kinds of electronic products. PBDEs are now ubiquitous in the environment, with soil as a major sink, especially in e-waste recycling sites. This study investigated the degradation of decabromodiphenyl ether (BDE209) in a spiked soil using Ni/Fe bimetallic nanoparticles. The results indicated that Ni/Fe bimetallic nanoparticles are able to degrade BDE209 in soil at ambient temperature and the removal efficiency can reach 72% when an initial pH of 5.6 and at a Ni/Fe dosage of 0.03g/g. A declining trend in degradation was noticed with decreasing Ni loading and increasing of initial BDE209 concentration. The degradation products of BDE209 were analyzed by GC-MS, which showed that the degradation of BDE209 was a process of stepwise debromination from nBr to (n−1)Br. And a possible debromination pathway was proposed. At last, the degradation process was analyzed as two-step mechanism, mass transfer and reaction. This current study shows the potential ability of Ni/Fe nanoparticles to be used for removal of PBDEs in contaminated soil.

Microbial Electricity Generation Enhances Decabromodiphenyl Ether (BDE-209) Degradation

Due to environmental persistence and biotoxicity of polybrominated diphenyl ethers (PBDEs), it is urgent to develop potential technologies to remediate PBDEs. Introducing electrodes for microbial electricity generation to stimulate the anaerobic degradation of organic pollutants is highly promising for bioremediation. However, it is still not clear whether the degradation of PBDEs could be promoted by this strategy. In this study, we hypothesized that the degradation of PBDEs (e.g., BDE-209) would be enhanced under microbial electricity generation condition. The functional compositions and structures of microbial communities in closed-circuit microbial fuel cell (c-MFC) and open-circuit microbial fuel cell (o-MFC) systems for BDE-209 degradation were detected by a comprehensive functional gene array, GeoChip 4.0, and linked with PBDE degradations. The results indicated that distinctly different microbial community structures were formed between c-MFCs and o-MFCs, and that lower concentrations of BDE-209 and the resulting lower brominated PBDE products were detected in c-MFCs after 70-day performance. The diversity and abundance of a variety of functional genes in c-MFCs were significantly higher than those in o-MFCs. Most genes involved in chlorinated solvent reductive dechlorination, hydroxylation, methoxylation and aromatic hydrocarbon degradation were highly enriched in c-MFCs and significantly positively correlated with the removal of PBDEs. Various other microbial functional genes for carbon, nitrogen, phosphorus and sulfur cycling, as well as energy transformation process, were also significantly increased in c-MFCs. Together, these results suggest that PBDE degradation could be enhanced by introducing the electrodes for microbial electricity generation and by specifically stimulating microbial functional genes.

브롬화 난연제인 Polybrominated Diphenyl Ethers (PBDEs)의 화학적처리 기술 개발

폴리에틸렌글리콜(PEGs)과 수산화칼륨(KOH)을 이용하여 서로 다른 온도와 시간의 반응조건에 따라 PBDEs의 화학반응을 수행하였다. PBDEs의 제거효율은 화학반응 전과 후의 농도의 차이로 측정하였다. PBDEs는 25와 <TEX>$50^{\circ}C$</TEX>의 낮은 온도에서는 제거되지 않았다. 하지만 온도를 증가시킴에 따라, 바이페닐기에 붙어있는 5-6개의 브롬이 치환되어 있는 PBDEs의 완전제거를 보이면서 <TEX>${\sigma}$</TEX>-xylene에 있는 PBDEs의 제거효율은 점차적으로 증가하였다. 반응조건을 4시간과 <TEX>$150^{\circ}C$</TEX>까지 증가시켰을 때 PBDEs의 제거효율은 거의 100%에 도달하였다. 이와 같이 PEGs와 PBDEs의 화학반응 연구를 통해, PBDEs가 PEGs에 의해 브롬이 순차적으로 제거되는 진행에 의해서 탈브롬화 된다는 것을 확인할 수 있었다. A chemical reaction of PBDEs was implemented using the polyethylene glycols (PEGs) and KOH, along with different reaction conditions such as temperatures and times. Removal efficiencies of PBDEs before and after chemical reaction were examined by difference of concentration. PBDEs was not removed at lower temperatures of 25 and <TEX>$50^{\circ}C$</TEX>. However, under the increased temperature, removal efficiency of PBDEs in <TEX>${\sigma}$</TEX>-xylene was gradually increased, showing completely removal of PBDEs containing 5-6 bromines on biphenyl frame. When increasing the reaction conditions to 4 hours and <TEX>$150^{\circ}C$</TEX>, removal efficiency of PBDEs reached almost 100%. In studying the reaction of PEGs with PBDEs, it confirmed that the PBDEs led to less brominated by PEGs through a stepwise process with the successive elimination of bromines.

Polybrominated diphenyl ethers (PBDEs) in a conventional wastewater treatment plant (WWTP) from Shanghai, the Yangtze River Delta: Implication for input source and mass loading

The concentrations of 19 polybrominated diphenyl ethers (PBDEs) congeners in a conventional wastewater treatment plant (WWTP) were determined to investigate the occurrence and fate of PBDEs during wastewater treatment processes. The level of total PBDEs ranged from 1.68 to 4.64ng/L in wastewater, with BDE209 accounting for the largest proportion, followed by penta- and octa-BDE congeners. PBDEs were found to mainly exist in the particulate phase of wastewater, which rendered sedimentation efficient for the removal of PBDEs, while the removal efficiencies might be varied for congeners with different Br atom numbers. Because of similar congener profiles, in-house dust was considered to be an important source for PBDEs in the WWTP. According to the mass loading estimation, over 60% of total PBDEs entering the WWTP accumulated in the dewatered sludge, resulting in the total PBDE release of 43.8kg/year via sewage sludge in Shanghai. And the annual release via effluent was estimated to be 5.5kg, less but shouldn't be neglected.

Parameters affecting the occurrence and removal of polybrominated diphenyl ethers in twenty Canadian wastewater treatment plants

This study determined PBDE levels in influent, primary effluent, and final effluent collected from diverse treatment processes including four aerated lagoons, two facultative lagoons, four primary treatments, eight secondary biological treatments and two advanced treatments. Parameters examined for correlation included seasonal temperature, community sizes, industrial inputs, and operational conditions. PBDE levels in influent were 21–1000 ng/L (median 190 ng/L). Higher concentrations in influent samples were found during summer, and in WWTPs which treated leachate and higher proportions of industrial wastewater vs. residential wastewater. Final effluent levels ranged between 3 and 270 ng/L (median 12 ng/L). Among all congeners, the sum of BDE-209, -47 and -99 accounted for 79 and 71% of total PBDEs in influent and final effluent, respectively, with BDE-209 having the highest proportion. Median removal efficiencies for all process types exceeded 90% except primary treatment at 70%. PBDE levels and removals were correlated to the levels and removals of conventional parameters that represent wastewater strength, such as chemical oxygen demand and total suspended solids. The role of the primary clarifier was significant (∼82% removal) and removal was associated with hydraulic retention time (HRT) and surface loading rate. Best removal of PBDEs was achieved at greater than 2000 mg/L mixed liquor suspended solids (MLSS), longer than 10 h of HRT, and 9 days of solids retention time.

Biphenyl and ethylbenzene dioxygenases of Rhodococcus jostii RHA1 transform PBDEs

Polybrominated diphenyl ethers (PBDEs) are a class of flame retardants that have been widely used in consumer products, but that are problematic because of their environmental persistence and endocrine-disrupting properties. To date, very little is known about PBDE degradation by aerobic microorganisms and the enzymes involved in PBDE transformation. Resting cells of the polychlorinated biphenyl-degrading actinomycete, Rhodococcus jostii RHA1, depleted nine mono- through penta-BDEs in separate assays. Extensive depletion of PBDEs occurred with cells grown on biphenyl, ethylbenzene, propane, or styrene, whereas very limited depletion occurred with cells grown on pyruvate or benzoate. In RHA1, expression of bphAa encoding biphenyl dioxygenase (BPDO) and etbAa1 and etbAc encoding ethylbenzene dioxygenase (EBDO) was induced 30- to 3,000-fold during growth on the substrates that supported PBDE depletion. The BPDO and EBDO enzymes had gene expression profiles that matched the PBDE-depletion profiles exhibited by RHA1 grown on different substrates. Using the non-PBDE-degrading bacterium Rhodococcus erythropolis as a host, two recombinant strains were developed by inserting the eth and bph genes of RHA1, respectively. The resultant EBDO extensively depleted mono- through penta-BDEs, while the BPDO depleted only mono-, di-, and one tetra-BDE. A dihydroxylated-BDE was detected as the primary metabolite of 4-bromodiphenyl ether in both recombinant strains. These results indicate that although both dioxygenases are capable of transforming PBDEs, EBDO more potently transforms the highly brominated congeners. The availability of substrates or inducing compounds can markedly affect total PBDE removal as well as patterns of removal of individual congeners.

Deposition versus Photochemical Removal of PBDEs from Lake Superior Air

Analysis of a sediment core collected from Siskiwit Lake, located on a remote island in Lake Superior, provides evidence that polybrominated diphenyl ethers (PBDEs) are removed effectively from the atmosphere via deposition processes during long-range transport. A mass balance model based on photochemical rate constants and data from atmospheric samples was created to understand the relative importance of various photochemical and deposition processes in removing PBDEs from the atmosphere. Photolysis rate constants were derived from UV absorption spectra of 25 PBDEs recorded in isooctane over the range of 280-350 nm at 298 K. Photolysis decays measured for BDE-3 and -7 in the gas phase were substantial compared to a well-defined chemical actinometer, indicating that their photolysis quantum yields are significant. Dibenzofuran production was observed when PBDE congeners containing ortho-bromines were photolyzed in helium. From estimates of removal rates of PBDEs from the lower troposphere, we find that wet and dry deposition accountfor >95% of the removal of BDE-209, while photolysis accounts for -90% of the removal of gas-phase congeners such as BDE-47. These results help explain the deposition patterns of PBDEs found in lake and river sediments and have important implications concerning the inclusion of photolysis as a fate process in multimedia models.

DSM BIOLOGICS TO BUILD NEW PLANT IN MONTREAL

Highly active and visible light-driven Ag-loaded CdS photocatalysts were prepared via a hydrothermal synthesis and photodeposition method. The removal and debromination of 2,2ʹ,4,4ʹ-tetrabromodiphenyl ether was achieved efficiently using this Ag-loaded CdS under visible light, with a removal efficiency of 100% and a debromination ratio of 44.3% being achieved within 30 min. Both the reaction solvent and the water content were found to have a strong influence on the removal efficiency and the debromination ratio. In addition, the stepwise debromination preference was ortho ≫ para, thereby indicating that the main debromination pathway was electron reduction. The stability and efficiency of these Ag-loaded CdS photocatalysts for the removal of BDE47 were satisfactory, and so our results confirmed the development of a promising visible light-driven catalyst for the removal of polybrominated diphenyl ethers.