| 11. |
- Hörsing, Maritha, 1970-, et al.
(författare)
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Investigation of the transformation potential of some ether derivatives of tetrabromobisphenol A and dimethyl ether of bisphenol A under methanogenic conditions
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This study focused on transformation of the flame retardant tetrabromobisphenol A (TBBPA) and ether derivatives thereof during incubation under methanogenic conditions using landfill waste as inoculum. Bisphenol A dimethyl ether was also investigated in that context. Glass wool was placed in the incubation flasks to increase the surface area for adsorption of target compounds and thereby maximize exposure to the microbial population. A uniform analytical protocol for extraction of the silica surface and the aqueous phase was developed to suit all the targets. Overall recoveries were lowest for the dimethylated ethers and highest for TBBPA-dihydroxyethylether. TBBPA decreased to below detection limit within 35 days, but neither BPA nor the methyl ether of TBBPA was confirmed as a transformation product. The dimethylated ethers of BPA and TBBPA disappeared within 14 and 51 days, respectively, and BPA, but not TBBPA, proved to be a transformation product. No losses were observed for the most hydrophobic target TBBPA-dibromopropyl ether during the time frame of the transformation study (i.e., 51 days).
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| 12. |
- Hörsing, Maritha, 1970-
(författare)
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Leaching and Transformation of Flame Retardants and Plasticizers under Simulated Landfill Conditions
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Many products used in our everyday life contain chemicals added to give them specific properties. Flame retardants (FRs) are added to prevent or retard fires in textiles, plastics etc., while plasticizers are supplied to make plastics more flexible. Through their widespread applications chemicals from both groups are emitted and spread in the environment during usage and disposal. For a long time these products were mainly disposed of in landfills, and in many areas they still are. Thus, since some of these chemicals also pose potential environmental risks and health hazards, there is a need to elucidate their fates during exposure to the landfill environmentThe objectives of this thesis were to investigate the leaching and transformation of FRs and plasticizers from products in which they are used under simulated landfill conditions. To assess the importance of changes in these processes as landfills progress through recognised ageing phases (accompanied by large transitions in both physico-chemical and biological conditions) it was desirable to simulate the changes that typically occur in landfills within a short time period, of 1-2 years.. This was achieved using the newly developed intermediate-scale (3 litre) Modular Environmental Test System (METS).The METS were employed in two studies. The first was an investigation of the leaching and degradation of plasticizers from PVC carpet material incubated at different temperatures (20, 37, 55 and 70°C) prevailing in landfills. Plasticizers subjected to this investigation were the phthalates di-2-ethylhexyl phthalate (DEHP) and benzyl-butyl phthalate (BBP), both of which were found to leach from the carpet. The leaching of DEHP and BBP generally increased with increases in the incubation temperature. However, the most rapid leaching of BBP occurred at 37°C, probably due to high microbial activity at this temperature. Both DEHP and BBP were shown to be degraded within the landfill environment and the degradation potential was highest during the methanogenic landfill phase. In the second METS study the leaching of FRs used in both reactive and additive applications (i.e. chemically bonded to and merely blended with the material, respectively) was characterised. The epoxy oligomer tetrabromobishpenol A (TBBPA) and the phosphorus-based Pyrovatex FRs were selected as representatives for the reactive FRs, while the nitrogen-based melamine and phosphorus-based Proban FRs were selected to represent additive classes. During the incubations, which lasted more than two years, the leaching from melamine was shown to be affected by the landfill phase development. The leaching from the Pyrovatex-treated material and the TBBPA epoxy oligomer seemed to result almost entirely from the washout of unreacted manufacturing residuals. This was also probably true for the FR in the Proban-treated material, although it is durable (despite being additively applied) and thus seemed to leach more slowly (manifested as an increase in phosphate levels in the leachate towards the end of the monitoring period).Finally, due to the paucity of knowledge regarding the fate of ether derivatives of TBBPA (which are also used as FRs) an anaerobic degradation assay was performed. The method employed for this assay was a modified, small-scale ISO standard method. In order to evaluate the degradation assay a uniform analytical protocol was developed. The degradation survey showed that losses of TBBPA, TBBPA-dimethyl ether and bisphenol A dimethyl ether occurred, but no losses of the most hydrophobic compound, TBBPA-dibromopropyl ether, were observed.
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| 13. |
- Hörsing, Maritha, 1970-, et al.
(författare)
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Leaching of Flame Retardants from products deposited in Landfills
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Materials in many products in daily use are amended with chemicals to give them desired properties, e.g. flame retardants (FRs) used to reduce the risks of products catching fire. However, potential risks posed by some of these chemicals, including FRs, to the environment and human health have raised concerns. Hence, there is a need for more knowledge regarding the fate of FRs, notably in landfills, where many FR-containing products are deposited. This article presents analyses of FRs and derivatives in leachates sampled during laboratory-scale simulations of landfills containing various FR-containing products progressing through typical landfill ageing phases. The FRs represented substances used both reactively, i.e. bound to the flame-protected material and additively, i.e. without any covalent bonding to the product.The phosphorus-based Pyrovatex-FR and the brominated tetrabromobisphenol A (TBBPA) were used to represent the reactive FRs, and the nitrogen-based melamine and phosphorus-based FR of Proban the additive FRs. Residual FRs from the treatment of the materials were probably the main contributors to the leachates from all products. Their durability, i.e. ability to withstand laundry washes, was reflected in their leaching abilities, while the different landfill conditions were of minor importance, except for melamine (of which approximately 10% of the amount present in the test product leached and mineralised to carbon dioxide and ammonia, mainly during the period when the landfill models passed from acidogenic to methanogenic conditions). The other additively applied FR in Proban leached first during the later part of the incubation (between 80 and 112 weeks), in accordance with its laundry resistance. Substantial proportions of the residual chemicals in Pyrovatex-treated materials are generally lost during the first washing. Accordingly, early losses of the chemicals used in this treatment were detected during the landfill simulation. Elevated phosphate concentrations were also detected in simulations with the Pyrovatex- and Proban-treated products, suggesting that the FRs generated in these treatments were degraded during or after release to the leachate. Small amounts of TBBPA were observed at the end of the incubation, and no TBBPA degradation products were observed, but debromination (which is likely to occur during anoxic stages) would lead to the formation of bisphenol A.
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| 14. |
- Jonsson, Susanne, 1965-, et al.
(författare)
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Investigation of sorption phenomena by solid-phase extraction and liquid chromatography for determination of some ether derivatives of tetrabromobisphenol A
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Observed sorption and chromatographic behaviour served as a starting point for examination of four ether derivatives of the flame retardant tetrabromobisphenol (TBBPA). To date, there is little or no information about these compounds in the scientific literature. The targets in the present study had calculated log Kow values of 6.0–10, indicating a rather hydrophobic nature. A broad range of different types of solvents were used in order to elucidate the mechanisms of sorption on one hydrophilic surface (silica) and two hydrophobic surfaces (polystyrene divinylbenzene polymers). Also, three chromatographic columns (C18, C8, and dual C18-based) were evaluated. In general, the most hydrophilic and the most hydrophobic derivatives (dihydroxyethyl- and di(2,3-bromopropyl), respectively) were more easily desorbed from the studied surfaces by the selected solvents.Regardless of the experimental test conditions applied, the lowest recovery was seen for dimethoxy-TBBPA, followed by TBBPA itself. Also, this study claims that the polar character of the dual-phase column was not as pronounced as asserted by the manufacturer.
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| 15. |
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| 16. |
- Thuy Nguyen, Lan, 1975-
(författare)
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Mobilization of metals from mining wastes and the resuspension of contaminated sediments
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In some environmental situations, environmental effects caused by elevated metals resulting from past mining and smelting activities can be observed in nearby receiving water bodies several decades after mine and smelter closure. There is a growing need for managing the hazardous solid wastes such as mining wastes as well as for assessing water quality and for sustainable management of sediment quality. The work presented in this thesis examined the mobilization of metals from two metal sources: mining wastes from a mine site in Vietnam and sediments from a contaminated lake in Sweden in order to test the hypothesis that mobilization of metals will be increased, when the environmental conditions change by e.g. exposure of mining wastes to oxidative weathering, change of redox conditions at the water-sediment interface and resuspension of sediments. The results from this work under field and laboratory conditions have verified the hypothesis. The exposure of sulphidic mining wastes in oxidative weathering conditions may cause long-term production of ARD and the resultant long-term mobility of metals. The oxidation/resuspension of sediments is an important factor for the release of trace metals Zn, Cu and Cd into the solution and substantial amounts of particles and, hence, associated metals into overlying water. The concomitant changes in pH during oxidation/resuspension of sediment play a significant role in the metal release both to redox sensitive elements Fe and Mn and trace elements Zn, Cu and Cd. The concomitant change in DOC during oxidation/resuspension can also contribute to the increased mobility of study metals. The field study was coupled to intermittent operation of a hydropower plant. The mobility of the metals was higher under operation compared to non-operation and, thus, the potential impacts on dispersal of metal pollution to downstream aquatic environments. The sudden increase in water flow upon the hydropower plant upon shifts from inactive to active state could cause immediate release of particles and thus particulate metals in the overlying water. However, the magnitude and its integrated effects in fluxes of metals over the season call for further research. There is a need to further investigate the impacts of hydropower generation in a longer period of time and at a higher frequency of observations at the very start of the hydropower operation. The results from this multidisciplinary approach would give a basis for an optimal operation of the hydropower plant to minimize the metal pollution associated with the water flow.
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| 17. |
- Ajjan Godoy, Fátima Nadia
(författare)
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Biohybrid Polymer Electrodes for Renewable Energy Storage
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Daily and seasonally fluctuating energy supply and demand requires adequate energy storage solutions. In recent years electrochemical supercapacitors have attracted considerable attention due to their ability to both store and deliver electrical energy efficiently. Our efforts are focused on developing and optimizing sustainable organic electrode materials for supercapacitors based on renewable bioorganic materials, offering a cheap, environmentally friendly and scalable alternative to store energy. In particular, we are using the second most abundant biopolymer in nature, lignin (Lig), which is an insulating material. However, when used in combination with electroactive and conducting polymers such as polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT), the biohybrid electrodes PPy/Lig and PEDOT/Lig display significantly enhanced energy storage performance as compared to the pristine conducting polymers without the lignin. Redox cyclic voltammetry and galvanostatic charge/discharge measurements indicate that the enhanced performance is due to the additional pseudocapacitance generated by the quinone moieties in lignin. Moreover, a conjugated redoxpolymer poly(aminoanthraquinone) PAAQ, with intrinsic quinone functions and excellentstability, has been combined with lignin and PEDOT resulting in a trihybrid bioelectrode. PEDOT compensates the low conductivity of PAAQ and provides electrical pathways to the quinone groups. The electrochemically generated quinones undergo a two electron, two protonredox process within the biohybrid electrodes as revealed by FTIR spectroelectrochemistry.These remarkable features reveal the exciting potential of a full organic energy storage device with long cycle life. Therefore, supercapacitor devices were designed in symmetric or asymmetric two electrode configuration. The best electrochemical performance was achieved by the asymmetric supercapacitor based on PEDOT+Lignin/PAAQ as the positive electrode and PEDOT/PAAQ as the negative electrode. This device exhibits superior electrochemical performance and outstanding stability after 10000 charge/discharge cycles due to the synergistic effect of the two electrodes. Finally, we have characterized the response of this supercapacitor device when charged with the intermittent power supply from an organic photovoltaic module. We have designed charging/discharging conditions such that reserve power was available in the storage device at all times. This work has resulted in an inexpensive fully organic system witht he dual function of energy conversion and storage.
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| 18. |
- Wijeratne, Kosala, 1983-
(författare)
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Conducting Polymer Electrodes for Thermogalvanic Cells
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fossil fuels are still the dominant (ca. 80%) energy source in our society. A significant fraction is used to generate electricity with a heat engine possessing an efficiency of approximately 35%. Therefore, about 65% of fossil fuel energy is wasted in heat. Other primary heat sources include solar and geothermal energies that can heat up solid and fluids up to 150°C. The growing demand and severe environmental impact of energy systems provide an impetus for effective management and harvesting solutions dealing with waste heat. A promising way to use waste heat is to directly convert thermal energy into electrical energy by thermoelectric generators (TEGs). Solid state TEGs are electronic devices that generate electrical power due to the thermo-diffusion of electronic charge carriers in the semiconductor upon application of the thermal field. However, there is another type of thermoelectric device that has been much less investigated; this is the thermogalvanic cell (TGCs). The TGC is an electrochemical device that consists of the electrolyte solution including a reversible redox couple sandwiched between two electrodes. In our study, we focus on iron-based organometallic molecules in aqueous electrolyte. A temperature difference (Δ?) between the electrodes promotes a difference in the electrode potentials [Δ?(?)]. Since the electrolyte contains a redox couple acting like electronic shuttle between the two electrodes, power can be generated when the two electrodes are submitted to a temperature difference. The focus of this thesis is (i) to investigate the possibility to use conducting polymer electrodes for thermogalvanic cells as an alternative to platinum and carbon-based electrodes, (ii) to investigate the role of viscosity of the electrolyte in order to consider polymer electrolytes, (iii) to understand the mechanisms limiting the electrical power output in TGCs; and (iv) to understand the fundamentals of the electron transfer taking place at the interface between the polymer electrode and the redox molecule in the electrolyte. These findings provide an essential toolbox for further improvement in conducting polymer thermogalvanic cells and various other emerging electrochemical technologies such as fuel cells, redox flow battery, dye-sensitized solar cells and industrial electrochemical synthesis.
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| 19. |
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| 20. |
- van Hees, Patrick
(författare)
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Low Molecular Weight Organic Acids and Their Aluminium Complexes in Forest Soils
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The significance of low molecular weight (LMW) organic acids and their aluminium (Al) complexes in soil solutions of podzolized soils was examined. Methods for the analysis of these compounds and complexes were developed, and the impact of these substances on the weathering and podzolization processes was studied. The factors influencing Al concentrations in podzolic soils were also evaluated.A high performance liquid chromatography (HPLC) method that includes an extensive sample pretreatment procedure was developed for the determination of LMW aliphatic acids. Futhermore, a size exclusion chromatography (SEC) method was developed and used in combination with ultrafiltration for the determination of LMW organic Al complexes. A chemical equilibrium model was employed to compare the experimental results.The highest concentrations of LMW organic acids were observed in the organic (0) horizon. Citric acid was the dominant acid in the O and E horizons (20-250µM) and oxalic acid in the B horizon (3-80 µM). A number of other acids, suchas shikimic, formic, acetic, fumaric, malic, malonic, t-aconitic and lactic acid, were occasionally identified. These compounds commonly constituted 0-5% of the dissolved organic carbon (DOC) and 0-15% of the acidity in soil solutions from podzolic soils. In addition, these acids commonly bound 25-45% of the Al and 15-20% of the Fe in the O horizon. This fraction declined in the deeper layers.Weathering experiments showed the enhancing effect of organic acids on the weathering rate of primary minerals. The emperical results also demonstrate a significant interaction between pH and ligand-promoted i.e. at lower pH values, less enhancement of weathering was observed, for K-feldspars but not for plagioclases. Ultrafiltration studies suggested that LMW organic acids are important weathering agents.The present findings concern the impact of LMW organic acids on the weathering of soils, the transport of aluminium and iron in the soil profile, and the immobilisation of Al and Fe in the illuvial horizon of podzols. The experimental results support the theory that Al is immobilised in the form of imogolite-type materials after microbial decomposition of the organic ligands.
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