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In recent years, thermoextraction/desorption-gas chromatography/mass spectrometry (TED-GC/MS) has been developed as a rapid detection method for the determination of microplastics (MP) mass contents in numerous environmentally relevant matrices and, in particular, for the measurement of polymers in water samples without time-consuming sample preparation. The TED-GC/MS method was applied to investigate a typical European municipal wastewater system for possible MP masses. Such investigations are important in view of the recent revision of the Urban Wastewater Treatment Directive. Four different representative sampling sites were selected: greywater (domestic wastewater without toilet), combined sewer, and influent and effluent of a wastewater treatment plant (WWTP). All samples were collected by fractional filtration. Filtration was carried out over mesh sizes of 500, 100, 50, and in some cases, 5 µm. Polyethylene (PE), polypropylene (PP), and polystyrene (PS) were detected in all samples, with the PE fraction dominating in all cases. Styrene-butadiene rubber which serves as an indication of tire abrasion, was only found in the influent of the WWTP. The highest MP mass contents were found in the combined sewer, so MP can become a source of pollution during heavy rain events when the capacity limits of the effluent are reached, and the polluted effluent is released uncontrolled into the environment. Based on the studies, MP retention from the WWTP could be estimated to be approximately 96%. Few trends in polymer type or mass contents were detected within the different fractions of the samples or when comparing samples to each other.
The adsorption of organic micropollutants onto activated carbon is a favourable solution for the treatment of drinking water and wastewater. However, these adsorption processes are not sufficiently understood to allow for the appropriate prediction of removal processes. In this study, thermogravimetric analysis, alongside evolved gas analysis, is proposed for the characterisation of micropollutants adsorbed on activated carbon. Varying amounts of carbamazepine were adsorbed onto three different activated carbons, which were subsequently dried, and their thermal decomposition mechanisms examined. The discovery of 55 different pyrolysis products allowed differentiations to be made between specific adsorption sites and conditions. However, the same adsorption mechanisms were found for all samples, which were enhanced by inorganic constituents and oxygen containing surface groups. Furthermore, increasing the loadings led to the evolution of more hydrated decomposition products, whilst parts of the carbamazepine molecules were also integrated into the carbon structure. It was also found that the chemical composition, especially the degree of dehydration of the activated carbon, plays an important role in the adsorption of carbamazepine. Hence, it is thought that the adsorption sites may have a higher adsorption energy for specific adsorbates, when the activated carbon can then potentially increase its degree of graphitisation.
Microplastic particles are currently detected in almost all environmental compartments. The results of detection vary widely, as a multitude of very different methods are used with very different requirements for analytical validity.
In this work four thermoanalytical methods are compared and their advantages and limitations are discussed. One of them is thermal extraction-desorption gas chromatography mass spectrometry (TED-GC/MS), an analysis method for microplastic detection that has become established in recent years. In addition, thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy (TGA-FTIR) and mass spectrometry (TGA-MS) were applied, two methods that are less common in this field but are still used in other research areas. Finally, microscale combustion calorimeter (MCC) was applied, a method not yet used for microplastic detection.
The presented results are taken from a recently published interlaboratory comparison test by Becker et al. (2020). Here a reference material consisting of suspended matter and specified added polymer masses was examined, and only the results of the recoveries were presented. In the present paper, however, the results for the individual polymers are discussed in detail and individual perspectives for all instruments are shown.
It was found that TED-GC/MS is the most suitable method for samples with unknown matrix and unknown, variable kinds and contents of microplastic. TGA-FTIR is a robust method for samples with known matrix and with defined kinds of microplastic. TGA-MS may offer a solution for the detection of PVC particles in the future. MCC can be used as a very fast and simple screening method for the identification of a potential microplastic load of standard polymers in unknown samples.
Due to the favorable properties of polymers, their production and thus their input into the environment has increased significantly in recent decades. Currently, FTIR or Raman spectroscopy are mainly applied for the analysis of microplastic particles (MP) in environmental samples. However, these methods have great difficulties in determining metrologically traceable MP values, especially with regard to the limiting values, as preferred in regulation. Therefore, we developed a systematic and fast thermoanalytical method called TED-GC-MS (thermal extraction desorption gas chromatography mass spectrometry), which determines mass contents. Now the current goal is the determination of its process parameters.
This poster illustrates the theoretical requirements for MP analysis (left side) and contrast them with the current state of research (right side).Unexpected practical problems are presented and the relatively new method is discussed concerning the quality requirements of well-established methods such as LC-or GC-MS.
Aufgrund der demographischen Entwicklung und dem damit verbundenen gesteigertem Bedarf an Medikamenten besteht in Deutschland das Problem des Eintrags von Rückständen und Transformationsprodukten über das Abwasser in die Umwelt. In herkömmlichen Reinigungsverfahren werden Medikamentenrückstände häufig unvollständig entfernt oder in andere teilweise toxischere Verbindungen umgewandelt (z. B. durch Ozonierung). Eine perspektivisch aussichtsreiche Möglichkeit zur Beseitigung dieser Schadstoffe ist die Oxidation zu Wasser und Kohlendioxid durch Bestrahlung des vorgeklärten Abwassers mit UV-Licht in Gegenwart von Photokatalysatoren wie z. B. TiO2.
Für vergleichende Untersuchungen der photokalalytischen Aktivität von TiO2-Submikro- und Nanopulvern im Labormaßstab wurde Methylenblau als Modellsubstanz gewählt. Kommerziell erhältliche TiO2-Pulver wurden Testlösungen zugesetzt und der zeitlich fortschreitende Abbau von Methylenblau unter Bestrahlung mit UV-Licht in beobachtet. Für die technische Nutzung der photokatalytischen Abwaserreinigung ist die Immobilisierung der eingesetzten Pulver mit der Möglichkeit der Rückgewinnung erforderlich, sowohl aus Umweltschutzgründen als auch für die Wirtschaftlichkeit des Verfahrens.
Aufbaugranulation wurde als ein prinzipiell auch großtechnisch realisierbares Verfahren der Immobilisierung gewählt. In einem Intensivmischer wurden Granulate auf der Basis von Submikrometer-SiO2 unter Verwendung eines anorganischen Binders hergestellt. Das photokatalytisch aktive TiO2 wurde in Anteilen von 10-25 Ma.-% entweder dem Ausgangspulver zugemischt oder am Ende des Granulierprozesses als Granulat-Coating aufgebracht. Eine Temperung der Granalien bei Temperaturen von maximal 300°C – 500°C erwies sich als ausreichend, um deren Stabilität beim Einsatz in Methylenblau-Lösung im Batch-Verfahren zu gewährleisten.
Tests zum Einsatz der SiO2-TiO2-Granulate als Photokatalysatoren zum Abbau von Methylenblau-Lösungen unter UV-Bestrahlung verliefen erfolgreich. Es konnte gezeigt werden, dass sich die Granalien nach erfolgtem Farbstoffstoff-Abbau aus den Lösungen rückgewinnen und erneut verwenden ließen. Die recycelten Granulate wiesen eine ähnliche photokatalytische Aktivität wie frisch hergestellte auf.