Filtern
Dokumenttyp
- Zeitschriftenartikel (6)
- Vortrag (3)
Sprache
- Englisch (9)
Schlagworte
- Thermogravimetry (9) (entfernen)
Organisationseinheit der BAM
Eingeladener Vortrag
- nein (3)
The presence of large quantities of plastic waste and its fragmentation in various environmental compartments are an important subject of current research. In the environment, (photo ) oxidation processes and mechanical abrasion lead to the formation of microplastics. However, until now, there are no established quality assurance concepts for the analysis of microplastic (<5 mm) in environmental compartments, including sampling, processing and analysis.
The aim of the present work is the development of suitable examination methods and protocols (sampling, sample preparation and detection) to qualify and quantify microplastic in urbane water management systems. At first a fractional filtration system for sampling and the analytical tool, the so-called TED-GC-MS (thermal desorption gas chromatography mass spectrometry) were developed. The TED-GC-MS method is a two-step analytical procedure which consists of a thermal extraction where the sample is annealed and characteristic decomposition products of the polymers are collected on a solid phase. Afterwards these products are analysed using GC-MS. The developed fractional filtration for sampling and the TED-GC-MS for detection were used for quantitative analysis to screen the waste water influent and effluent of a Berlin waste water treatment plant for the most relevant polymers, polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET) and polyamide (PA).
The results of the study revealed that the polymeres PE, PS and PP were detected in the effluent, and PE and PS were find in the raw waste water of the sewage treatment plant in Ruhleben, Berlin. Differences in polymer types and amounts were detected at different sampling dates and within different sieve fractions. Much higher amounts of polymers were observed in the raw waste water. The peak areas of the decomposition products, used for quantification of the polymers, were adjusted using so-called response factors since the TED-GC-MS method is more sensitive for PP and PS than for PE. It has been shown that PE is the most dominant polymer in the samples. Comparing the masses of polymers in the effluent and in the raw sewage, a removal of 99 % of the polymers in the water treatment plant can be assumed. These results are consistent with the literature where removal rates between 98-99 % were described.
Boehmite nanoparticles has been successfully functionalized with APTES. After APTES functionalization further modification with tailored molecules e.g. via carboxylic acids is possible. The tailored surface functionalization is strongly enhanced by improved coupling protocols. Arbitrary variation of the functionalization degree is possible. Thereby the temperature stable APTES functionalization enables a wide range of functional groups.
By TGA-MS analysis strong evidence for the bonding situation of the APTES on the boehmite surface has been found. Additionally first experiments has been performed to predict the polymer-particle compatibility enhancement via reverse wetting angle measurements with AFM.
Twelve different samples were analyzed for their water content by the classical oven-drying method and a commercial moisture analyzer. Nominal values have been set by Karl Fischer titration and gravimetry. The decomposition during the drying process of samples containing organic compounds was checked by thermogravimetry coupled with Fourier transform infrared spectrometric and mass spectrometric detection. Summarizing all measurement results, the commercial moisture analyzer demonstrated an average bias for the determination of water contents, which is much smaller than the stated uncertainty and thus is negligible. Compared to the classical oven-drying method, the commercial moisture analyzer shows a smaller bias, more ease in handling and less time consumption per analysis. When validated by a reference procedure like Karl Fischer titration the commercial moisture analyzer is the method of choice for routine analysis.
On the thermal behaviour and thermo-oxidative stability of liquid crystalline triphenylene compounds
(1999)
Columnar discotic materials are considered for applications in the area of photoconductivity and light-emitting diodes. A major requirement is their stability at elevated temperatures and in the presence of oxygen. The thermal and thermo-oxidative behaviour of discotic triphenylene derivatives was investigated by us using various methods, in particular by chemiluminescence (CL), UV-vis absorption spectroscopy and in situ thermogravimetry-mass spectroscopy (TG-MS). Various degradation processes are described for increasing temperature, and their influences on functional properties are discussed.
Advanced wastewater treatment with powdered activated carbon (PAC) leads to a spread of PAC into different purification stages of wastewater treatment plants (WWTP) due to recirculation and filter back-wash. Currently, no methods for quantification of PAC in activated sludge are available. In this study, PAC containing activated sludge from four WWTP were examined by two-step thermogravimetric analysis (TGA) with heating up to 600°C in N2 and subsequently in synthetic air. Direct quantification of PAC according to temperature specific weight losses was possible for one WWTP. Quantification by combining specific mass losses was found to be an alternative direct method, with a detection limit of 1.2% PAC in dry sample mass.
Additionally, evolved gas analysis (EGA) by infrared-spectroscopy (FTIR) during TGA revealed interaction mechanisms between PAC and activated sludge. Aliphatic compounds from activated sludge were identified as major substances influenced by PAC. In derivative thermogravimetry (DTG), a typical double peak at approximately 300°C was found to be related to carbonylic species with increased evolution of acetic acid in aged activated sludge. TGA and EGA are promising tools to understand, control and optimise the application of PAC in advanced wastewater treatment.
Advanced wastewater treatment by the application of activated carbon is used to eliminate organic micropollutants in large scale wastewater treatment plants. However, underlying adsorption processes are unclear. On the one hand, compositions of wastewater differ and are very complex. On the other hand, activated carbons have physicochemical properties which impair investigations on adsorption mechanisms, since they are non-graphitic, non-graphitizable and have a highly disordered microstructure. This leads to their large surface areas and internal pore structure but also implies heteroatoms and functional groups. These are not easily accessible for research but affect the adsorption of organic micropollutants. Thermogravimetric analysis and evolved gas analysis can provide valuable insights into these kinds of systems. First, pyrolysis makes functional surface groups accessible, e.g. through decarboxylation, which facilitates characterisation of activated carbons. Second, adsorbates can be investigated by thermal desorption or decomposition, depending on the sorption conditions of the organic micropollutants. Single component systems as well as multi component systems with competing organic background matter are compared for various activated carbons. Surprising distinctions in the adsorption mechanisms will be presented.
Maya Blue, a pigment composed of very low concentrations of natural indigo and the clay mineral palygorskite, is one of the most brilliant blue dyes, intensively used for more than 2000 years in Mesoamerica. It is extremely stable against environmental attacks and was applied by the Indians for inside and outside mural paintings, ceramics, textiles and for colouring their famous codices. In the present paper it was studied as a powder (compared with modern synthetic indigo) and as colour on tissues, a Maya clay head, and fragment IV of the famous Codex Huamantla. Investigations using Raman spectroscopy in the visible and near-infrared range showed a high degree of correspondence among all Maya Blue-carrying samples and a good agreement with synthetic indigo. Additional spectral lines may be explained by a transformation of the planar indigo molecule when binding to the palygorskite lattice. Thermal investigations of the original amatl paper of the codex and of recent paper from fig-trees showed a high similarity and thus proved that this tree was chosen for paper making by Mayas, Aztecs and other Indian tribes. This was also true for the codex.
Using thermogravimetric analysis (TGA) with a solid-phase adsorber for thermal extraction, followed by subsequently analysing the adsorber with thermo-desorption gas chromatography mass spectrometry (TDS-GCMS) enables measurement of polymer degradation under oxidizing atmosphere, and the identification of certain complex hydrocarbon degradation products by chromatographic separation and defined mass patterns. This technique, thermal-extraction desorption gas chromatography mass spectrometry (TED-GCMS) was used to investigate the thermo-oxidative degradation of PA 66 and PA 66 doped with 2 wt% of metal oxide particles. In TGA pure PA 66 formed more residue under an oxidizing atmosphere than an inert one. In contrast to the measurements under inert atmosphere, several condensed aromatic species containing nitrogen could be identified in thermo-oxidative measurements. These degradation products were formed through condensation reactions of primary amides originating from imide hydrolysis. The formation of such highly condensed species also causes higher char formation. Four metal oxides have shown an impact on the thermo-oxidative degradation of PA 66: Fe2O3 on η-Al2O3 < pure Fe2O3 = Fe2O3 on γ-Al2O3 < pure ZnO. For ZnO even a char-stabilizing effect could be observed. A catalytic effect of these metal oxides causes more condensed cyclopentanone and pyridine derivates. Thus, more water is formed and released, resulting in increased hydrolysis of the imides and degradation at lower temperatures.
Permineralized samples of the tree fern Psaronius sp. belong to the spectacular discoveries of the Lower Permian Rotliegend Petrified forest of Chemnitz, one of the most famous palaeontological sites in the world. The cellular tissues of the 280 million years old fossil fern show a delicate three-dimensional preservation by permineralization. Moreover, anatomical detail can be distinguished very well because of the black coloured former cell walls. By means of Raman spectroscopy this fossilised tissue of the adventitious roots is revealed to be carbon which structure seems to correspond to anthracite. The aim of this work is the experimental confirmation of the carbon structure by means of thermogravimetry and Raman spectroscopy on coal samples of different rank, especially anthracite samples from different times and localities.
Coal maturation involves the sequence peatlignitecoalanthracite-microcrystalline graphite by incresasing the density and specific energy. The loss of in situ moisture (typically up to 200 °C) and volatile organic matter (up to 600 °C) has been acquired by thermogravimetry. The increasing carbon content, density resp. structure results in Raman spectra with typical band shape of the D- and G-peaks. We used these methods to characterise and compare the separated coal samples to the dispersed carbon inclusions in permineralized Psaronius.