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Advanced oxidation processes have become an important part of research due to their capacity to degrade many environmental pollutants during water treatment. Especially the heterogeneous photocatalysis is a promising method because it often results in a full mineralization of many hazardous compounds. Incomplete degradation reactions can result in transformation products due to oxidative conditions. The transformation products may have a higher toxicity than the precursor substances and are often only partly removed during water treatment. Since a lot of these compounds are still unknown, transformation products are not detected by target analysis used in sewage treatment plants and are often released into the aquatic ecosystems. Therefore, extensive and effective non-target analytical methods are necessary for the monitoring and identification of the transformation products which can be generated during waste water treatment.
Titanium dioxide (TiO2) is the most frequently used photocatalyst because of its inexpensiveness, non-toxicity, chemical stability and its high photocatalytic activity. If TiO2 is irradiated electron-hole pairs are generated on the surface of the TiO2, resulting in the formation of active oxidized species such as hydroxyl radicals which can react with environmental pollutants.
A model system has been developed to simulate photocatalytic reactions in a laboratory scale. The commonly used pharmaceuticals metformin and gabapentin were selected as model substances because of their high input in waste water and the little information about their fate during water treatment. Metformin is the drug of choice for treating type 2 diabetes. More than half of the total amount of pharmaceuticals in the environment are the antidiabetic agent metformin and its major transformation product guanylurea. Gabapentin is used as antiepileptic drug and for the treatment of neuropathic pain. It is found in waste water influent in the high ng/L range.
First results of the optimization of the photocatalyst and its application are shown.
In recent years advanced oxidation processes have become an important part of research due to their capacity to degrade many environmental pollutants during water treatment. Especially the heterogeneous photocatalysis is a promising method because it often results in a full mineralization of many hazardous organic compounds. However incomplete degradation reactions during this process can result in transformation products due to the oxidative conditions. The transformation products may have a higher toxicity than the precursor substances and are often only partly removed during the waste water treatment. Since a lot of these compounds are still unknown, the transformation products are not detected by target analysis used in sewage treatment plants and are often released into the aquatic ecosystems. Therefore, extensive and effective non-target analytical methods are necessary for the monitoring and identification of the transformation products which can be generated during waste water treatment. Among various semiconductors, titanium dioxide (TiO2) is the most frequently used photocatalyst because of its inexpensiveness, non-toxicity, chemical stability and its high photocatalytic activity. If TiO2 is irradiated with light of an energy higher than the band gap of the semiconductor, electron-hole pairs are generated on the surface of the TiO2, resulting in the formation of active oxidized species such as hydroxyl radicals which can react with environmental pollutants. To study photocatalytic reactions, a model system has been developed to simulate environmental relevant conditions for photocatalytic reactions of organic substances on a laboratory scale. The commonly used pharmaceuticals metformin and gabapentin were selected as model substances because of their high input in waste water and the little information about their occurrence, behavior and fate in the environment. Metformin is the drug of choice for treating type 2 diabetes. The drug therapy for diabetes mellitus has increased significantly in recent years. More than half of the total amount of pharmaceuticals in the environment are the antidiabetic agent metformin and its major transformation product guanylurea. Gabapentin is an analogon of the neurotransmitter γ-aminobutyric acid (GABA) which is used as antiepileptic drug and for the treatment of neuropathic pain. Gabapentin is found in waste water influent in the high ng/L range.
First results of the optimization of the photocatalyst and its application are shown.
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.
Untersuchung der Transformation von umweltrelevanten Schadstoffen am Beispiel von 4-n-Octylphenol
(2015)
A first pilot study on the sorption of environmental pollutants on various microplastic materials
(2017)
With the drastic increase in plastic production, the input of plastic particles into the environment has become a recognised problem.
Xenobiotics are able to sorb to polymer materials, and this process is further enhanced where they Encounter microplastics (plastic fragments <5 mm). In this work we studied the sorption of metformin, a type-2 diabetes drug, and difenoconazole, a fungicide, onto the virgin polymer materials polyamide (PA), polypropylene (PP), and polystyrene (PS). Additionally, PP was cryo-milled and PA was treated with acid to investigate the influence of an increase in surface area and chemical modification. The material properties were also studied by dynamic scanning calorimetry (DSC), gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR). Sorption experiments were performed on the basis of a full factorial design examining the effect of agitation, pH value, and salinity. Experimental results showed that difenoconazole sorbs readily to all microplastics, whereas the more polar analyte metformin did not show any affinity to the materials used. For difenoconazole the governing factor in all cases is agitation, while both pH and salinity exhibited only a slight influence. The modification of polymers leads to enhanced sorption, indicating that an increase in surface area (cryo-milled PP) or inner volume (acid-treated PA) strongly favours adsorption. Moreover, long-term experiments demonstrated that the time until equilibrium is reached depends strongly on the particle size.
For years there have been more and more reports on the presence of drugs in the aquatic environment. Due to the demographic change, the consumption of pharmaceuticals has risen sharply. After taking the drugs, they are partly metabolized in the human body. However, the metabolism is not complete so that both the metabolites and non-metabolized amounts of the parent compounds are excreted. These compounds reach the waste water and afterwards the sewage treatment plants. In sewage treatment plants transformation products can be formed by the oxidative conditions during wastewater treatment processes. The transformation products may have a higher toxicity than the actual environmental pollutants and are often only partly removed during the waste water treatment. Since a lot of these compounds are still unknown, the transformation products are not detected by target analysis used in sewage treatment plants and are often released undetected in the aquatic ecosystems. The released substances may be subject to additional transformation processes in the environment. Pharmaceuticals produced in high amounts can be already detected in the μg/L range in water bodies worldwide.
Metformin and its major transformation product guanylurea are one of the main representatives. Metformin is the drug of choice for treating type 2 diabetes. The drug therapy for diabetes mellitus has increased significantly in recent years. In the year 2015 1500 tons of metformin were prescribed in Germany (for statutory insured persons). Metformin is not metabolized in the human body and is excreted unchanged therefore concentrations between 57 μg/L and 129 μg/L are found in German waste water treatment plants influents.
In this work the transformation of the antidiabetic drug metformin is investigated. The degradation of metformin is initialize by commercial water treatment techniques like UV-radiation or noncommercial techniques like heterogenous photocatalysis based on titanium dioxide. The degradation of metformin and resulting transformation products are analyzed by LC-MS/MS and LC-HRMS.
Plastics are used in many applications, such as packaging, building and construction, mobility and transport and more. Due to their favourable properties like light weight, flexible processing and low costs their production and consequently their input into natural systems has increased significantly over the last decades. In the environment (photo )oxidation processes and mechanical abrasion lead to the decomposition of the plastics. During this process microplastics (<5 mm) can be formed. It has been shown that environmental pollutants can sorb to these microplastics.[1,2] Nevertheless, knowledge on this topic is still limited.
Our work aims at the investigation of the sorption behaviour of the triazole fungicide difenoconazole to simulated microplastics made of virgin polyamide (PA), polypropylene (PP), and polystyrene (PS). Sorption experiments were planned based on a full factorial design with agitation, salinity, and pH value as parameters. The results of our study revealed that difenoconazole indeed, has sorbed to all microplastics tested here. Data analysis showed that agitation is the main influencing factor, whereas salinity and the pH value held little to no significance on the amount of sorbed difenoconazole.
To simulate the behaviour of naturally aged microplastics, sorption to cryo-milled PP and acid-treated PA was also studied. The thus treated samples were characterised by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and dynamic scanning calorimetry (DSC). FTIR spectroscopy did not show any changes in the chemical structure but GPC and DSC measurements indicated a systematic chain scission of the treated PA. Scanning electron microscope (SEM) images illustrate that milling of the microplastics leads to non-spherical, star-shaped particles. This fact has a huge influence on the surface properties and consequently on the absorption.
The results of our study are important in terms of i) creating realistic sorption scenarios with relevant parameters for the sorption process, as well as for ii) the choice of proper materials to simulate naturally occurring microplastics. We could show that not only the characteristics of the material like particle size distribution or surface properties are important, but also the applied analytical technique which is used for the characterization of the material . Since there is no standard methodology for microplastic identification and quantification, we suggest to combine several methods to obtain a reliable overall characterization.
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.
Der Vortrag stellt spektroskopische und neue thermoanalytische Verfahren zum Nachweis von Mikroplastik in Umweltproben vor. Ein spezieller Fokus liegt auf dem neu entwickelten Verfahren der TED-GC-MS. Zusätzlich wird gezeigt, wie die TED-GC-MS eingesetzt werden kann, um Reifen in der Umwelt zu bestimmen.
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.
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.
Das Ziel dieses Projektes ist die Entwicklung neuer Materialien, um den Rückhalt von Mikroplastik-Partikeln (MP) aus verschiedenen urbanen Eintragspfaden (Kläranlagenablauf, Mischwasserüberlauf und Straßenabfluss)zu optimieren.
Die im Rahmen des Projekts entwickelten Materialien sollten auf ihre Rückhaltefähigkeit von MP aus dem Kläranlagenklarlauf getestet werden. Für die Probenahme sowie für die Analytik wurden die entwickelten und optimierten Probenahme- sowie Analysetechniken angewendet.
Das Ziel des OEMP-Projektes ist die Entwicklung neuer Materialien, um den Rückhalt von Mikroplastik-Partikeln (MP) aus verschiedenen urbanen Eintragspfaden (Kläranlagenablauf, Mischwasserüberlauf und Straßenabfluss) zu optimieren. Grundlage für die Bewertung ist die Entwicklung von geeigneten Untersuchungsverfahren (Probennahme, Probenaufbereitung, Detektion) zur Qualifizierung und Quantifizierung von MP in den relevanten Umweltmatrices. Diese Verfahren müssen zeiteffizient und zuverlässig sein.
Plastics and rubber are used in many applications, such as packaging, building, construction and mobility. Due to their favourable properties like light weight, flexible processing and low costs their production and consequently their input into the environment has increased significantly over the last decades. In the environment, oxidation processes and mechanical abrasion lead to the decomposition of these plastics into small fragments, called microplastic (< 5 mm). By definition, microplastics only involve thermoplastics and duroplastics but elastomers made out of synthetic polymers (e. g. styrene butadiene rubber), modified natural polymers (e. g. natural rubber) and products of synthetic polymers (e. g. tires) are also part of the current microplastic discussion. The main entry pathway of rubber into the environment is the wear of used tire treads in road traffic. Lassen et al. showed that 60 % of the microplastic emissions in Denmark into the environment come from secondary microplastics generated by tires. Rain events can cause microplastic and rubber to get from the street into the street inlets. Depending on the sewage system, these waters are sometimes not cleaned in the sewage treatment plants and reach the surface waters untreated.
To analyse microplastic particles in samples, mainly FTIR or Raman spectroscopic methods are applied at present. Rubber or tire particles in environmental samples cannot be analysed by these methods, because the added carbon black leads to annoying absorption and fluorescent effects.
We developed a thermoanalytical method, the so-called TED-GC-MS (thermal extraction desorption gas chromatography mass spectrometry), which allows the simultaneous detection of microplastic and tire wear with almost no sample preparation in about 2.5 h. The TED-GC-MS is a two-step analytical method which consists of a thermobalance and a GC-MS system. Up to 50 mg of an environmental sample is heated up to 600 °C in a nitrogen atmosphere. During pyrolysis, between 300 and 600 °C polymer-specific decomposition products are produced and collected on a solid phase. Afterwards the substances are desorbed, separated and analysed using the GC-MS.
The aim of the present work is to present the TED-GC-MS as a time efficient screening method to quantify the industrial most relevant polymers in street run-off samples. Analytical challenges in the determination of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET) and polyamide (PA), polymethyl methacrylate (PMMA) and styrene-butadiene-rubber (SBR) as a component of tire wear are honestly discussed.
The study area is a 200 m long section of the Clayallee in Berlin, a representative typical urban catchment area. The road run-off in this section flows through the gullies directly into a sample chamber, which directs the runoff in an open channel to the rainwater sewer of this area. The sample chamber allows a sample to be taken directly from the road run-off without mixing with the run-off from other areas. The sample chamber is equipped with an automatic sampler. The automatic sampler is controlled by a conductivity sensor to detect the storm event at an early stage. The sensor gives the sampler a signal to start the sampling program when it gets in contact with water and reaches a certain conductivity threshold. The capacity of the sample container is 100 l and the maximum delivery of the automatic sampler is 2.8 l/min.
Afterwards, the water was pumped through various stainless-steel sieves with a diameter of approximately 20 cm and mesh widths of 500, 100, 50 μm. The obtained solids were steam sterilized, freeze-dried and measured with the TED-GC-MS.
The results of the TED-GC-MS-measurements are summarized in Figure 1. It shows the polymers which were detected in 1 mg of the dry masses of various street run off samples obtained during a period of 1.5 years. We detected PMMA, PS, PP, PE and SBR, as a component of tire wear in the samples. The quantification of the polymers leads to amounts of PS, PP, PE and SBR between 0 µg and 10 µg. PMMA was only detected in traces.