Simultaneous in situ characterisation of bubble dynamics and a spatially resolved concentration profile : A combined Mach-Zehnder holography and confocal Raman-spectroscopy sensor system

For a reaction between a gaseous phase and a liquid phase, the interaction between the hydrodynamic conditions, mass transport and reaction kinetics plays a crucial role with respect to the conversion and selectivity of the process. Within this work, a sensor system was developed to simultaneously characterise the bubble dynamics and the localised concentration measurement around the bubbles. The sensor system is a combination of a digital Mach-Zehnder holography subsystem to measure bubble dynamics and a confocal Raman-spectroscopy subsystem to measure localised concentration. The combined system was used to investigate the chemical absorption of CO₂ bubbles in caustic soda in microchannels. The proposed set-up is explained and characterised in detail and the experimental results are presented, illustrating the capability of the sensor system to simultaneously measure the localised concentration of the carbonate ion with a good limit of detection and the 3-D position of the bubble with respect to the spot where the concentration was measured

Investigation of the reaction kinetics of photocatalytic pollutant degradation under defined conditions with inkjet-printed TiO2_{2} films – from batch to a novel continuous-flow microreactor

Pollutants accumulating in natural and drinking water systems can cause severe effects to the environment and living organisms. Photocatalysis is a promising option to degrade such pollutants. When immobilizing the photocatalyst, additional catalyst separation steps can be avoided. Among various reactor types, the use of microreactors in photocatalysis has proven advantageous regarding process intensification. However, so far the local conditions are not well understood and described in literature and there is little quantitative understanding of the relevant phenomena. In this work, inkjet-printing was used to immobilize TiO$_{2}$ as a thin film with a precisely tuneable thickness and catalyst loading. In a batch reactor, the degradation of rhodamine B (RhB) as a model pollutant was performed for different initial concentrations and catalyst layer thicknesses. By employing the Langmuir–Hinshelwood model and a light irradiation model, the kinetic parameters were determined. The influence of the light intensity at different positions inside the immobilized photocatalyst on the reaction kinetics is quantified. RhB degradation was tested under defined operational conditions using an in-house developed continuous-flow microreactor with advanced fiber optics for precise light introduction. The models derived from batch experiments were used to simulate the degradation in the continuous-flow microreactor. Results show that the simulation allows prediction of the performance with less than 20% deviation to the experimental data. An analysis of mass transport effects on the reaction rate indicates that external mass transfer is a limiting factor in the microreactor experiment. This study further demonstrates the potential of the new reactor system (microreactor, fiber optics and printed catalyst) for detailed investigations on photocatalytic reaction kinetics

Investigation of the reaction kinetics of photocatalytic pollutant degradation under defined conditions with inkjet-printed TiO2_{2} films – from batch to a novel continuous-flow microreactor

Pollutants accumulating in natural and drinking water systems can cause severe effects to the environment and living organisms. Photocatalysis is a promising option to degrade such pollutants. When immobilizing the photocatalyst, additional catalyst separation steps can be avoided. Among various reactor types, the use of microreactors in photocatalysis has proven advantageous regarding process intensification. However, so far the local conditions are not well understood and described in literature and there is little quantitative understanding of the relevant phenomena. In this work, inkjet-printing was used to immobilize TiO$_{2}$ as a thin film with a precisely tuneable thickness and catalyst loading. In a batch reactor, the degradation of rhodamine B (RhB) as a model pollutant was performed for different initial concentrations and catalyst layer thicknesses. By employing the Langmuir–Hinshelwood model and a light irradiation model, the kinetic parameters were determined. The influence of the light intensity at different positions inside the immobilized photocatalyst on the reaction kinetics is quantified. RhB degradation was tested under defined operational conditions using an in-house developed continuous-flow microreactor with advanced fiber optics for precise light introduction. The models derived from batch experiments were used to simulate the degradation in the continuous-flow microreactor. Results show that the simulation allows prediction of the performance with less than 20% deviation to the experimental data. An analysis of mass transport effects on the reaction rate indicates that external mass transfer is a limiting factor in the microreactor experiment. This study further demonstrates the potential of the new reactor system (microreactor, fiber optics and printed catalyst) for detailed investigations on photocatalytic reaction kinetics

Environmental considerations and current status of grouping and regulation of engineered nanomaterials

This article reviews the current status of nanotechnology with emphasis on application and related environmental considerations as well as legislation. Application and analysis of nanomaterials in infrastructure (construction, building coatings, and water treatment) is discussed, and in particular nanomaterial release during the lifecycle of these applications. Moreover, possible grouping approaches with regard to ecotoxicological and toxicological properties, and the fate of nanomaterials in the environment are evaluated. In terms of potential exposure, the opportunities that arise from leveraging advances in several key areas, such as water treatment and construction are addressed. Additionally, this review describes challenges with regard to the European Commission’s definition of ‘nanomaterial’. The revised REACH information requirements, intended to enable a comprehensive risk assessment of nanomaterials, are outlined

Analytical and toxicological aspects of nanomaterials in different product groups: Challenges and opportunities

The widespread integration of engineered nanomaterials into consumer and industrial products creates new challenges and requires innovative approaches in terms of design, testing, reliability, and safety of nanotechnology. The aim of this review article is to give an overview of different product groups in which nanomaterials are present and outline their safety aspects for consumers. Here, release of nanomaterials and related analytical challenges and solutions as well as toxicological considerations, such as dose-metrics, are discussed. Additionally, the utilization of engineered nanomaterials as pharmaceuticals or nutraceuticals to deliver and release cargo molecules is covered. Furthermore, critical pathways for human exposure to nanomaterials, namely inhalation and ingestion, are discussed in the context of risk assessment. Analysis of NMs in food, innovative medicine or food contact materials is discussed. Specific focus is on the presence and release of nanomaterials, including whether nanomaterials can migrate from polymer nanocomposites used in food contact materials. With regard to the toxicology and toxicokinetics of nanomaterials, aspects of dose metrics of inhalation toxicity as well as ingestion toxicology and comparison between in vitro and in vivo conclusions are considered. The definition of dose descriptors to be applied in toxicological testing is emphasized. In relation to potential exposure from different products, opportunities arising from the use of advanced analytical techniques in more unique scenarios such as release of nanomaterials from medical devices such as orthopedic implants are addressed. Alongside higher product performance and complexity, further challenges regarding material characterization and safety, as well as acceptance by the general public are expected

Multiple Persönlichkeiten. Mareike Krügels Novelle "Die Witwe, der Lehrer, das Meer" als Kontrafaktur einer literarischen Gattungszuschreibung

Volkmann C. Multiple Persönlichkeiten. Mareike Krügels Novelle "Die Witwe, der Lehrer, das Meer" als Kontrafaktur einer literarischen Gattungszuschreibung. In: Helmes G, Rinke G, eds. Gescheit, gescheiter, gescheitert. Das zeitgenössische Bild von Schule und Lehrer in Literatur und Medien. SchriftBilder. Studien zur Medien- und Kulturwissenschaft. Vol 8. Hamburg: Igel; 2016: 27-42