PBDF and PBDD from the combustion of bromine containing flame retarded polymers: A survey

The formation of polybrominated dibenzofurans (PBDF) and dibenzodioxins (PBDD) during the pyrolysis of different polymers containing brominated organic flame retardants was investigated. The pyrolyses were conducted at two different temperatures (600°C and 800°C) using three different oven configurations. Both the pyrolysis gases and the solid residues were analysed for PBDF and PBDD.

PBDF were found in almost all samples, but both the concentration and the degree of bromination varied greatly. The largest yields of PBDF in the percent range were measured in the pyrolysis products of polymers containing brominated diphenyl ethers. The other flame retardants generally yielded only a few ppm of PBDF. PBDD are formed only in a few samples and related to the PBDF in very low concentrations.     

PVC-induced chlorine-bromine exchange in the pyrolysis of polybrominated diphenyl ethers, -biphenyls, -dibenzodioxins and dibenzofurans

Extensive chlorine-for-bromine exchange occurs when 1,2,3,4-tetrabromodibenzodioxin (TBrDD), polybromodibenzodioxin/furan mixtures (PBrDD/F), and technical brominated diphenyl ethers and -biphenyls are pyrolyzed at 800°C in the presence of PVC. Tetra-ClDD, BrCl₃DD, Br₂Cl₂DD, and Br₃ClDD could be detected from the pyrolysis of 1,2,3,4-TBrDD. A number of chloro/bromodibenzodioxins and furans as well as chlorinated dibenzodioxins and furans are formed in the residues of the PBrDD/F mixtures. Only chlorinated and chlorinated/brominated diphenyl ethers and no dioxins and furans occured during the pyrolysis of brominated diphenyl ethers in the presence of PVC. Through the exchange of bromine with chlorine, chlorinated and chlorinated/brominated biphenyls could be detected from the pyrolysates of hexabromobiphenyl.     

Thermal formation of polybrominated dibenzofurans and dioxins from decabromodiphenyl ether flame retardant: Influence of antimony(III) oxide and the polymer matrix

While pure decabromodiphenyl ether forms highly brominated PBDF in combustion at 700°C in yields of ca. 7000 ppm the yield is significantly increased up to 16 percent in the polymeric matrix and the presence of antimony(III) oxide. Combustion of the ternary mixture results in a decrease of the temperature maximum to 500°C; the ratio of isomers is changed to lower brominated PBDF with the tetrabromo compounds as most abundant products.     

Distribution and levels of brominated flame retardants in sewage sludge

One hundred and sixteen sewage sludge samples from 22 municipal wastewater treatment plants in Sweden were analysed for brominated flame retardants. Polybrominated diphenyl ethers (PBDEs) were in the range n.d.-450 ng/g wet weight, tetrabromobisphenol A (TBBPA) varied between n.d. and 220 ng/g wet weight, 2,4,6-tribromophenol was in the range n.d.-0.9 ng/g wet weight and polybrominated biphenyls were not detected (except for a possible analytical interference). There was a significant variation in the samples among plants. Influence from industries and other local sources can therefore be assumed. The correlation pattern indicated contribution from three different types of technical products; composed of either low-brominated PBDEs, decaBDE or TBBPA.     

Application of 1D and 2D MFR reactor technology for the isolation of insecticidal and anti-microbial properties from pyrolysis bio-oils

Valuable chemicals can be separated from agricultural residues by chemical or thermochemical processes. The application of pyrolysis has already been demonstrated as an efficient means to produce a liquid with a high concentration of desired product. The objective of this study was to apply an insect and microorganism bioassay-guided approach to separate and isolate pesticidal compounds from bio-oil produced through biomass pyrolysis. Tobacco leaf (Nicotianata bacum), tomato plant (Solanum lycopersicum), and spent coffee (Coffea arabica) grounds were pyrolyzed at 10°C/min from ambient to 565°C using the mechanically fluidized reactor (MFR). With one-dimensional (1D) MFR pyrolysis, the composition of the product vapors varied as the reactor temperature was raised allowing for the selection of the temperature range that corresponds to vapors with a high concentration of pesticidal properties. Further product separation was performed in a fractional condensation train, or 2D MFR pyrolysis, thus allowing for the separation of vapor components according to their condensation temperature. The 300–400°C tobacco and tomato bio-oil cuts from the 1D MFR showed the highest insecticidal and anti-microbial activity compared to the other bio-oil cuts. The 300–350 and 350–400°C bio-oil cuts produced by 2D MFR had the highest insecticidal activity when the bio-oil was collected from the 210°C condenser. The tobacco and tomato bio-oil had similar insecticidal activity (LC₅₀ of 2.1 and 2.2 mg/mL) when the bio-oil was collected in the 210°C condenser from the 300–350°C reactor temperature gases. The 2D MFR does concentrate the pesticidal products compared to the 1D MFR and thus can reduce the need for further separation steps such as solvent extraction.     

Plasma PBDE and thyroxine levels in rats exposed to Bromkal or BDE-47

In experimental models, polybrominated diphenyl ethers (PBDEs), a group of brominated flame retardants, have caused effects in a number of biological end-points, including neurobehavioural effects, disturbances in thyroid and steroid hormone homeostasis, and other steroid-related effects. Almost exclusively, only external dose metrics (dose per body weight basis) have been studied in connection to the observed effects. In this study we report on new analyses of plasma PBDE levels in surplus samples from earlier studies on thyroid hormones (TH) in exposed rodents. Female, 7-week old Sprague-Dawley rats were given either Bromkal 70-5 DE (Study I; 18 or 36 mg/kg bw/day) or BDE-47 (Study II; 1, 6 or 18 mg/kg bw/day) daily by gavage for two weeks. At an external dose of 18 mg/kg bw/day significant TH effects (decreased plasma free thyroxin levels) were observed in both studies, corresponding to an internal (plasma) dose of 463 microg sumPBDE/g lipid (Study I) or 421 microg BDE-47/g lipid (Study II). If we compare the contribution of different BDE congeners to the total BDE level in rat plasma after Bromkal exposure (Study II), and in the Bromkal mixture itself, the most important congener in the Bromkal mixture were also found in plasma. However, the relative concentration of BDE-99 was lower, and that of BDE-153 was higher, than that of the mixture, indicating selectivity in uptake, metabolism and/or excretion of the individual BDE congeners. Explicitly, the possible in vivo conversion of BDE-99 to BDE-47, and of BDE-154 to BDE-153 could not be excluded. The internal dose in the present rat study could be compared to reported human serum doses of PBDE. Human serum/blood levels have a wide range, from 3 to 6 ng sumPBDE/g lipid in background samples from Europe, about 10 times higher in US sample, and up to 100 times higher (300-600 ng/g lipid) in upper-end levels in collected samples from USA. As a consequence, the margin between effects levels in the rat and exposure levels in man varies widely, with a quotient roughly from 1000 to 100,000. Generally, it could be expected that this margin is lower than if external dose metrics would be used. An even lower margin could be expected as recent studies have shown effects in offspring at lower doses than those giving effects in our studies. Lastly, it should be noted that humans are already exposed to a mixture of chemicals in daily life, a fact that complicates this kind of comparison.     

Modeling adsorption kinetics of trichloroethylene onto biochars derived from soybean stover and peanut shell wastes

Trichloroethylene (TCE) is one of the most hazardous organic pollutants in groundwater. Biochar produced from agricultural waste materials could serve as a novel carbonaceous adsorbent for removing organic contaminants from aqueous media. Biochars derived from pyrolysis of soybean stover at 300 °C and 700 °C (S-300 and S-700, respectively), and peanut shells at 300 °C and 700 °C (P-300 and P-700, respectively) were utilized as carbonaceous adsorbents to study batch aqueous TCE remediation kinetics. Different rate-based and diffusion-based kinetic models were adopted to understand the TCE adsorption mechanism on biochars. With an equilibrium time of 8–10 h, up to 69 % TCE was removed from water. Biochars produced at 700 °C were more effective than those produced at 300 °C. The P-700 and S-700 had lower molar H/C and O/C versus P-300 and S-300 resulting in high aromaticity and low polarity accompanying with high surface area and high adsorption capacity. The pseudo-second order and intraparticle diffusion models were well fitted to the kinetic data, thereby, indicating that chemisorption and pore diffusion were the dominating mechanisms of TCE adsorption onto biochars.     

Surface-mediated formation of PBDD/Fs from the high-temperature oxidation of 2-bromophenol on a CuO/silica surface

As a model brominated hydrocarbon that may form brominated dioxins, we studied the surface-mediated, oxidative thermal degradation of 2-bromophenol on a supported copper oxide catalyst in a 1 mm i.d., fused silica flow reactor at a constant concentration of 90 ppm over a temperature range from 250 to 550 degrees C. Observed products included: dibenzo-p-dioxin (DD), 1-monobromodibenzo-p-dioxin (1-MBDD), dibromodibenzo-p-dioxin (DBDD), tribromodibenzo-p-dioxin (TrBDD), 4-monobromodibenzofuran (4-MBDF), 2,4,6-tribromophenol, 2,4- and 2,6-dibromophenol, and polybrominated benzenes. The results are compared and contrasted with previous work on surface catalyzed oxidative thermal degradation of 2-chlorophenol as well as our own work with the surface-catalyzed pyrolytic thermal degradation of 2-bromophenol. Typically 20 to 200x higher yields of PBDDs are observed for 2-bromophenol than for the analogous PCDDs for 2-chlorophenol. However the anticipated PBDF, 4,6-DBDF, was not observed and 4-MBDF was observed at very low yields. Surprisingly, the maximum yields of PBDDs were observed at higher temperatures than under pyrolytic conditions. This is attributed to regeneration of the catalytic surface due to the presence of oxygen. Higher yields of polybrominated phenols and polybrominated benzenes were also observed than for the analogous chlorinated phenols and benzenes from the oxidation of 2-chlorophenol. This can be attributed to the ease of bromination over chlorination based on the higher abundance of bromine atoms present for 2-bromophenol than chlorine atoms present for 2-chlorophenol.     

Kinetics and the mass transfer mechanism of hydrogen sulfide removal by biochar derived from rice hull

The biochar derived from rice hull was evaluated for its abilities to remove hydrogen sulfide (H₂S) from gas phase. The surface area and pH of the biochar were compared. The biochar derived from rice hull was evaluated for its abilities to remove hydrogen sulfide (H₂S) from gas phase. The surface area and pH of the biochar were compared. The different pyrolysis temperature has great influence on the adsorption of H₂S. At the different pyrolysis temperature, the H₂S removal efficiency of rice hull-derived biochar was different. The adsorption capacities of biochar were 2.09 mg·g^–1, 2.65 mg·g^–1, 16.30 mg·g^–1, 20.80 mg·g^–1, and 382.70 mg·g^–1, which their pyrolysis temperatures were 100 °C, 200 °C, 300 °C, 400 °C and 500 °C respectively. Based on the Yoon-Nelson model, it analyzed the mass transfer mechanism of hydrogen sulfide adsorption by biochar.

Implications: The paper focuses on the biochar derived from rice hull–removed hydrogen sulfide (H₂S) from gas phase. The surface area and pH of the biochar were compared. The different pyrolysis temperatures have great influence on the adsorption of H₂S. At the different pyrolysis temperatures, the H₂S removal efficiency of rice hull–derived biohar was different. The adsorption capacities of biochar were 2.09, 2.65, 16.30, 20.80, and 382.70 mg·g^?1, and their pyrolysis temperatures were 100, 200, 300, 400, and 500 °C, respectively. Based on the Yoon-Nelson model, the mass transfer mechanism of hydrogen sulfide adsorption by biochar was analyzed.     

Effect of Fractionation and Pyrolysis on Fuel Properties of Poultry Litter

Abstract

Raw poultry litter has certain drawbacks for energy production such as high ash and moisture content, a corrosive nature, and low heating values. A combined solution to utilization of raw poultry litter may involve fractionation and pyrolysis. Fractionation divides poultry litter into a fine, nutrient-rich fraction and a coarse, carbon-dense fraction. Pyrolysis of the coarse fraction would remove the corrosive volatiles as bio-oil, leaving clean char. This paper presents the effect of fractionation and pyrolysis process parameters on the calorific value of char and on the characterization of bio-oil. Poultry litter samples collected from three commercial poultry farms were divided into 10 treatments that included 2 controls (raw poultry litter and its coarse fraction having particle size greater than 0.85 mm) and 8 other treatments that were combinations of three factors: type (raw poultry litter or its coarse fraction), heating rate (30 or 10 °C/min), and pyrolysis temperature (300 or 500 °C). After the screening process, the poultry litter samples were dried and pyrolyzed in a batch reactor under nitrogen atmosphere and char and condensate yields were recorded. The condensate was separated into three fractions on the basis of their density: heavy, medium, and light phase. Calorific value and proximate and nutrient analysis were performed for char, condensate, and feedstock. Results show that the char with the highest calorific value (17.39 ± 1.37 MJ/kg) was made from the coarse fraction at 300 °C, which captured 68.71 ± 9.37% of the feedstock energy. The char produced at 300 °C had 42 ± 11 mg/kg arsenic content but no mercury. Almost all of the Al, Ca, Fe, K, Mg, Na, and P remained in the char. The pyrolysis process reduced ammoniacal-nitrogen (NH₄-N) in char by 99.14 ± 0.47% and nitrate-nitrogen (NO₃-N) by 95.79 ± 5.45% at 500 °C.     

Pyrolysis temperature influences ameliorating effects of biochars on acidic soil

The biochars were prepared from straws of canola, corn, soybean, and peanut at different temperatures of 300, 500, and 700 °C by means of oxygen-limited pyrolysis. Amelioration effects of these biochars on an acidic Ultisol were investigated with incubation experiments, and application rate of biochars was 10 g/kg. The incorporation of these biochars induced the increase in soil pH, soil exchangeable base cations, base saturation, and cation exchange capacity and the decrease in soil exchangeable acidity and exchangeable Al. The ameliorating effects of biochars on acidic soil increased with increase in their pyrolysis temperature. The contribution of oxygen-containing functional groups on the biochars to their ameliorating effects on the acidic soil decreased with the rise in pyrolysis temperature, while the contribution from carbonates in the biochars changed oppositely. The incorporation of the biochars led to the decrease in soil reactive Al extracted by 0.5 mol/L CuCl₂, and the content of reactive Al was decreased with the increase in pyrolysis temperature of incorporated biochars. The biochars generated at 300 °C increased soil organically complexed Al due to ample quantity of oxygen-containing functional groups such as carboxylic and phenolic groups on the biochars, while the biochars generated at 500 and 700 °C accelerated the transformation of soil exchangeable Al to hydroxyl-Al polymers due to hydrolysis of Al at higher pH. Therefore, the crop straw-derived biochars can be used as amendments for acidic soils and the biochars generated at relatively high temperature have great ameliorating effects on the soils.     

Properties of biochars from conventional and alternative feedstocks and their suitability for metal immobilization in industrial soil

In contaminated soils, excessive concentrations of metals and their high mobility pose a serious environmental risk. A suitable soil amendment can minimize the negative effect of metals in soil. This study investigated the effect of different biochars on metal (Cu, Pb, Zn) immobilization in industrial soil. Biochars produced at 300 and 600 °C from conventional (MS, maize silage; WP, wooden pellets) and alternative (SC, sewage sludge compost; DR, digestate residue) feedstocks were used as soil amendments at a dosage of 10 % (w/w). The type of feedstock and pyrolysis temperature affected the properties of the biochars and their ability to immobilize metal in soil. Compared to production at 300 °C, all biochars produced at 600 °C had higher pH (6.2–10.7), content of ash (7.2–69.0 %) and fixed carbon (21.1–56.7 %), but lower content of volatile matter (9.7–37.2 %). All biochars except DR biochar had lower dissolved organic carbon (DOC) content (1.4–2.3 g C/L) when made at 600 °C. Only MS and SC biochars had higher cation exchange capacity (25.2 and 44.7 cmol/kg, respectively) after charring at 600 °C. All biochars contained low concentrations of Cd, Cu, Ni, Pb and Zn; Cd was volatilized to the greatest extent during pyrolysis. Based on FTIR analysis and molar ratios of H/C and O/C, biochars had a greater degree of carbonization and aromaticity after charring at 600 °C. The efficiency of the biochars in metal immobilization depended mainly on their pH, ash content, and concentration of DOC. SC and DR biochars were more effective for Cu and Zn immobilization than MS and WP biochars, which makes them attractive options for large-scale soil amendment.     

Chlorine-bromine exchange during pyrolysis of 1,2,3,4-tetrabromo-dibenzodioxin with various chlorine donors

1,2,3,4-T₄BrDD was pyrolyzed with PVC, HCl and NaCl at 900°C. In all reactions bromine was exchanged with chlorine. During the pyrolysis with PVC at T = 900°C, 69 % of the starting material reacted to give BrCl-dioxins (34.3 %) and 1,2,3,4-T₄CDD (34.7 %). In the reaction with HCl (T = 900°C), 49.2 % BrCl-dioxins and 1,2,3,4-T₄CDD formed. The pyrolysis with NaCl (T = 900°C) yielded 10.5 % BrCl-dioxins and 1,2,3,4-T₄CDD.     

Effects of production conditions on yield and physicochemical properties of biochars produced from rice husk and oil palm empty fruit bunches

Biochar is the bio-solid material produced by pyrolysis. The biochar properties are controlled by feedstock and pyrolysis variables. In this study, the impacts of these production variables on biochar yield and physicochemical properties including pH, cation exchange capacity (CEC), total organic carbon (TOC) content, surface area, and pore volume and size were investigated. Rice husk (RH) and oil palm empty fruit bunches (EFB) were used as biomass. The biochars were produced at temperature range of 300 to 700 °C, heating rate of 3 to 10 °C/min and retention time of 1 to 3 h. The pyrolysis conditions were optimized using response surface methodology (RSM) technique to maximize the values of the responses. Analysis of variance (ANOVA) of the results demonstrated that the data fitted well to the linear and quadratic equations. Temperature was found to be the most effective parameter on the responses followed by retention time and heating rate, sequentially. CEC, TOC, surface area, and pore characteristics were evaluated as biochar properties determining their sorption potential. The optimum conditions for the maximum values of the properties were temperatures of 700 and 493.44 °C and time of 3 and 1 h for RH and EFB biochars, respectively. Heating rate at 3 °C/min was found to be the best rate for both biochars. The structure of EFB biomass was more sensitive to heating than rice husk. The biomass type and the production variables were demonstrated as the direct effective factors on biochar yield and physicochemical properties.     

Bildung von 2,3,7,8-TCDD bei der Thermolyse von ausgewählten chlorierten organischen Verbindungen

Upon heating of 2,4,5-T to 600°C, 2,3,7,8-TCDD is formed with a yield of 0,2 %. At 800°C, the formation of TCDD decreases by a factor at 200. Tormona 80^® an ester at 2,4,5-T yields 200 ppm TCDD at 600°C and 3 ppm at 800°C. The highest formation rate is observed for 2,4,5-Trichlorophenol (0,5 % at 600°C). During the thermolysis of 2,4-D, γ-Hexachlorocyclohexane, 2,4,6-Trichlorophenol, Pentachlorophenol and Clophen A 40. 2,3,7,8-TCDD could not be detected.     

Insights into aqueous carbofuran removal by modified and non-modified rice husk biochars

Biochar has been considered as a potential sorbent for removal of frequently detected pesticides in water. In the present study, modified and non-modified rice husk biochars were used for aqueous carbofuran removal. Rice husk biochars were produced at 300, 500, and 700 °C in slow pyrolysis and further exposed to steam activation. Biochars were physicochemically characterized using proximate, ultimate, FTIR methods and used to examine equilibrium and dynamic adsorption of carbofuran. Increasing pyrolysis temperature led to a decrease of biochar yield and increase of porosity, surface area, and adsorption capacities which were further enhanced by steam activation. Carbofuran adsorption was pH-dependant, and the maximum (161 mg g^?1) occurred in the vicinity of pH 5, on steam-activated biochar produced at 700 °C. Freundlich model best fitted the sorption equilibrium data. Both chemisorption and physisorption interactions on heterogeneous adsorbent surface may involve in carbofuran adsorption. Langmuir kinetics could be applied to describe carbofuran adsorption in a fixed bed. A higher carbofuran volume was treated in a column bed by a steam-activated biochar versus non-activated biochars. Overall, steam-activated rice husk biochar can be highlighted as a promising low-cost sustainable material for aqueous carbofuran removal.     

Thermolysis of 2,4,6-trichlorophenol chemisorbed on aluminium oxides as example of fly ash mediated surface catalysis reaction in PCDD/PCDF formation

The influence of aluminium cation as a strong electrophilic centre on the thermolysis of chlorophenols chemisorbed on Al(OH)₃ surface was investigated. If thermolysis is carried out at 300 °C the spontaneous rupture of the bond between aluminium and oxygen of phenol takes place in the temperature range of 260–280 °C. The thermolysis of chlorophenoxy aluminium compounds occurs through homolytic and heterolytic bond cleavage. In the case of heterolytic cleavage the leaving chlorophenoxy anion causes a simultaneous formation of the aluminium cation, which is the driving force for the rearrangement of the unstable intermediate. By homolytic cleavage of the Al–O bond the chlorophenoxy radical is formed. The isolation of reaction products of the thermolysis of the system Al(OH)₃/2,4,6-trichlorophenol gave five isomers of dimeric compounds of resonance stabilised 2,4,6-trichlorophenoxy radical. The compounds are stable in nonaqueous, aprotic solution, but they are very sensitive to acid catalysis. They quickly transform into aromatic hydroxydiphenyl ethers. The process of dechlorination and aromatisation of cyclohexadienone dimers gives PCDD/PCDF.     

Biodegradation kinetics of selected brominated flame retardants in aerobic and anaerobic soil

The purpose of the present study was to investigate the biodegradation kinetics in aerobic and anaerobic soil of the following brominated flame retardants: 2,4,4′-tribromodiphenyl ether (BDE 28), decabromodiphenyl ether (BDE 209), tetrabromobisphenol A (TBBPA), 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), 2,4,6-tribromophenol (246BrPh), and hexabromobenzene (HxBrBz). For comparison, the biodegradation of the chlorinated compounds 2,4,4′-trichlorodiphenyl ether (CDE 28), 2,4,6-trichlorophenol (246ClPh), hexachlorobenzene (HxClBz), and 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB 153) was also assessed. In aerobic soil, BDE 209 showed no significant degradation during the test period, but concentrations of the other BFRs declined, with half-lives decreasing in the following order: BDE 28 > TBBPA > TBECH > HxBrBz > 246BrPh. Declines in almost the same order were observed in anaerobic soil: BDE 28, BDE 209 > TBBPA > HxBrBz > TBECH >246BrPh.     

Method optimization to measure polybrominated diphenyl ether (PBDE) concentrations in soils of Bratislava, Slovakia

We modified an analytical method to determine polybrominated diphenyl ethers (PBDEs) in urban soils of Bratislava (Slovakia). Gel permeation chromatography (GPC) introduced as a clean-up step for soil extracts substantially reduced matrix enhancements when PBDEs were measured with gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS). The resulting method proved to be accurate, precise, and showed low detection limits. The sum of 15 PBDE concentrations in surface horizons of Bratislava soils ranged from 87 to 627 pg g⁻¹. PBDE concentrations were mostly higher in surface than deeper horizons probably because of atmospheric deposition and lack of substantial vertical transport. Lower brominated PBDEs undergo more soil-atmosphere exchanges or are more scavenged and transferred with litter fall to the soil organic matter than higher brominated ones as suggested by the correlation between lower brominated PBDEs and soil organic C (C_org) concentrations.