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Die Feintrocknung spielt eine Schlüsselrolle für den Einsatz und insbesondere die Einspeisung von Wasserstoff in die Erdgasinfrastruktur. Zur thermischen Regenerierung des Trockenmittels können Radiowellen für eine direkte dielektrische Erwärmung des Schüttbettes eingesetzt werden. In Abhängigkeit von den verwendeten Zeolithen, NaX oder NaY, sind dabei sowohl eine homogene Erwärmung als auch eine selektive Erwärmung der wasserbeladenen Trockenmittelschüttungen möglich. Nach entsprechenden Tests steht nunmehr ein einsatzfähiger druckfester Prototyp für die Wasserstofftrocknung zur Verfügung.

Selective measurement of hydrogen in the natural gas grid as large transport and storage infrastructure is a crucial requirement for establishing a hydrogen economy. Cost-effective sensors must face mainly two critical conditions: (i) absence of oxygen contents capable for ensuring the sensor function and (ii) presence of a large surplus of another reducing gas, methane. The developed Pt/TiO2 sensor is based on the combination of the catalytic spillover effect and an impedance measurement. It allows hydrogen detection in a wide concentration range and it is specific for hydrogen while other gases such as methane or carbon dioxide behave like inert gases. The sensor curve with decreasing relative sensitivity for higher hydrogen concentrations and the temperature dependence of the sensor effect are in agreement with the spillover-based sensor principle, where hydrogen is activated on Pt and then spills over onto the TiO2 where it acts as electron donor.

The histamine-1 receptor antagonist azelastine was recently found to impact SARS-CoV-2 viral kinetics in a Phase 2 clinical trial (CARVIN). Thus, we investigated the relationship between intranasal azelastine administrations and viral load, as well as symptom severity in COVID-19 patients and analyzed the impact of covariates using non-linear mixed-effects modeling. For this, we developed a pharmacokinetic (PK) model for the oral and intranasal administration of azelastine. A one-compartment model with parallel absorption after intranasal administration described the PK best, covering both the intranasal and the gastro-intestinal absorption pathways. For virus kinetic and symptoms modeling, viral load and symptom records were gathered from the CARVIN study that included data of 82 COVID-19 patients receiving placebo or intranasal azelastine. The effect of azelastine on viral load was described by a dose-effect model targeting the virus elimination rate. An extension of the model revealed a relationship between COVID-19 symptoms severity and the number of infected cells. The analysis revealed that the intranasal administration of azelastine led to a faster decline in viral load and symptoms severity compared to placebo. Moreover, older patients showed a slower decline in viral load compared to younger patients and male patients experienced higher peak viral loads than females.

Reductive catalytic conversion of DDT (p,p′-dichlorodiphenyltrichloroethane) was studied under ambient conditions in a hydrogen atmosphere using platinum and palladium deposited on several supports, in particular on porous alumina and silica. Almost complete hydrodechlorination and hydrogenation of DDT and its dehydrochlorination byproduct DDE (p,p′-dichlorodiphenyldichloroethene), leading to the formation of diphenylethane (with Pd) and dicyclohexylethane (with Pt), were observed at ambient temperature within minutes or hours. Rapid hydrodechlorination also takes place after depositing DDT and the metal component on separate particles and mixing them mechanically. This long-range reactivity can be explained either by a fast surface diffusion of DDT or DDE, or by hydrogen spillover. Irrespective of the mechanism, the reactivity thus bridges the barrier across solid particle interfaces. Most findings indicate the fast diffusion of target compounds as dominant mechanism for the observed long-range reactivity.

[EN] For drying building structures, dielectric heating using RF energy (13.56 MHz) is an efficient and fast alternative to conventional heating methods relying solely on heat transfer from the surface to the interior of the masonry. Another innovative application of volumetric RF heating is chemical-free pest control in wood-based materials. For such applications where the RF systems often cannot be completely shielded, the propagation or coupling of the electromagnetic waves into wires that are placed inside the field cannot be neglected which represents a certain risk. Depending on the different electromagnetic coupling mechanisms, several interference signals can be generated. In order to protect electrical equipment in the surrounding, these interferences have to be significantly reduced by electrical filters. For this purpose, a cost-effective and robust measuring concept was developed. With the help of this system, the common mode (iCM) interference could be identified as the dominant part and the differential mode (iDM) interference as a minor disturbance. Based on the experimental evaluation, a cost-effective filter for the respective disturbance was constructed and successfully tested.

The non‐thermal plasma (NTP) technique was shown to be a method to improve indoor air quality. In particular in kitchens, odorous emissions can be removed by NTP. A combined concept of adsorption of volatile organic compounds (VOC) and plasma regeneration of the adsorber was tested in adsorption‐regeneration‐adsorption cycles. As reference VOC, 2‐methylthiophene, 2‐methylpyrazine, 2‐acetylthiazole, nonanal and trans‐2‐nonenal were used in humid air streams. These odorous compounds are emitted during cooking and frying processes. The adsorption‐regeneration concept was also tested during a simulated frying process with garlic in rape oil. A hydrophobic zeolite was chosen as adsorber material and placed directly into the discharge zone of a plasma reactor.

Decontamination of air or other gas streams loaded with low VOC concentrations is a prevalent task for adsorption using zeolites. Emphasizing the importance of adsorber selection, several zeolites varying in type, Si/Al ratio and provider were tested for toluene as representative organic target compound and water as adsorbate both in single and competing adsorption studies. In some cases, the toluene breakthrough is mainly caused by water-driven desorption. It was shown that for adsorption capacity, kinetics and competition behavior not only type and Si/Al ratio of the zeolite are important but also producer-specific parameters such as crystallinity, binder type and content which are usually not explicitly documented. This study offers a basis for the selection of adsorber materials for treatment of gas streams with significant water contents.

Non-thermal plasma technique can be a method to improve indoor air quality. In particular in cuisines, odorous emissions can be removed by non-thermal plasmas. In this study 2-methylthiophene, 2-methylpyrazine, 2-acetylthiazole, nonanal and trans-2-nonenal were used as target compounds in concentrations in the low ppmv range. These odorous compounds are emitted during cooking and frying processes. The oxidation of these target compounds as multi-component mixture in a non-thermal gas-phase plasma was studied in dry mixtures of argon and oxygen and in humid air. Complete oxidation of the odorous compounds to COX was achieved in both atmospheres. The energy efficiency was higher in the dry mixture of argon and oxygen, whereas the selectivity of the oxidation towards carbon dioxide was significantly higher in humid air. The main products of plasma treatment were identified as CO, CO2 and polymeric deposits. Some minor organic intermediates in the pptv range were also identified. Although odor carriers could be completely degraded and the concentrations of potentially harmful organic byproducts were several orders of magnitude below critical values, high ozone and CO emissions during plasma operation are critical for indoor application of non-thermal plasma as stand-alone technique. The combination with a catalytic step, either as in-plasma or post-plasma catalysis, might be a promising approach to tackle this problem.

Thermal pest control with hot air is widely accepted as an alternative to chemical methods. However, it requires relatively long treatment times due to the low thermal conductivity of wood. Direct dielectric heating applying radio waves or microwaves has the advantage of a more homogeneous heating. However, sound experimental data on this technique are rare at present. Therefore, thermal treatment of wood-destroying insects with radio waves and microwaves was studied with two model pests, Anobium punctatum and Hylotrupes bajulus, and with Tenebrio molitor as reference. It was shown that a secure elimination of pests can be achieved by temperatures above 55°C; the corresponding treatment time was in the range of a few minutes. Temperature profiles were more homogeneous when applying radio waves.

Dielectric heating with radio waves (RW) and microwaves (MW) are alternatives to treatments with hazardous chemicals or hot air for pest control. In particular, RW can be used to heat up bulky materials with larger size (in the meter range) homogeneously and smoothly in order to eliminate embedded pest organisms. Dielectric heating, in principle, enables selective overheating of certain materials in a heterogeneous mixture. This unique feature of electromagnetic heating methods, in contrast to techniques being based on thermal conduction, is caused by significant differences in the dielectric properties of pest organisms and matrix materials. The present study proves unambiguously that selective heating of cylindrical pest organisms in wood matrices occurs under defined conditions. The selective heating effect strongly depends on the orientation of the pest organisms in the electric field. For a parallel alignment, maximum overheating factors (ratio of adiabatic local heating rates) of 2 to 3 were determined experimentally. In case of a perpendicular alignment, no overheating was detected. A simulation of electric field and power loss density distributions in pest organisms and in their vicinity in the wood matrix, using a finite element method, can qualitatively explain the experimental results. According to the simulation, the overheating occurs not directly within the pest organism but in the wood matrix in the vicinity on both ends of the cylinder-shaped pest organism

The application of radio waves with a frequency of 13.56 MHz on electrolyte solutions in a capillary reactor led to the formation of reactive hydrogen and oxygen species and finally to molecular oxygen and hydrogen. This process of water splitting can be principally used for the elimination of hazardous chemicals in water. Two compounds, namely perfluorooctanoic acid (PFOA) and tetrahydrofuran, were converted using this process. Their main decomposition products were highly volatile and therefore transferred to a gas phase, where they could be identified by GC-MS analyses. It is remarkable that the chemical reactions could benefit from both the oxidizing and reducing species formed in the plasma process, which takes place in gas bubbles saturated with water vapor. The breaking of C–C and C–F bonds was proven in the case of PFOA, probably initiated by electron impacts and radical reactions.

For mitigation of the impact on flood-damaged cultural heritage buildings and sites, solely conservation-compatible and noninvasive strategies can be applied. All procedures have to take into account not only the specific situation after flooding but also the material properties and the characteristics of the artwork related to the building. After a heavy flooding event damaging the monastery Marienthal in Germany demonstration studies were proceeded to evaluate heritage-adequate treatment strategies for the drying of a decorated chapel. To respect and preserve the original gypsum stucco interior drying in certain temperature limits had to be respected. Particularly, direct volumetric heating methods were employed working with electromagnetic waves in the frequency ranges of either microwaves or radio waves. The studies comprised heating tests on site and experiments on a heritage-representative masonry specimen. It could be shown that the removal of water could be significantly enhanced by both techniques. Radio wave heating was demonstrated to allow a more homogeneous and better controlled treatment in comparison to microwave application, which is especially relevant in case of sensitive materials such as gypsum. With respecting that limits the techniques can be applied in combination with efficient removal of moisture from the ambient air by ventilation in order to reduce the drying time thus limiting subsequent damage of the heritage building.

Die thermische Bekämpfung von Holzschädlingen erfordert wegen der geringen Wärmeleitfähigkeit von Holz lange Behandlungszeiten und kann zur Rissbildung führen. Hier wurde die thermische Behandlung mittels Radio- und Mikrowellen untersucht. Die direkte, dielektrische Erwärmung hat den Vorteil einer größeren Homogenität der Aufheizung. Die mit Radiowellen erzielten Temperaturprofile waren homogener als die mit Mikrowellen realisierten. Untersuchungen zeigten, dass die Abtötung nicht auf die direkte Einwirkung von elektromagnetischen Feldern, sondern auf die Temperaturerhöhung zurückzuführen ist.Thermal pest control requires long treatment times due to the low thermal conductivity of wood and may lead to the formation of cracks. Here, the thermal treatment with radio waves as well as microwaves has been studied. The direct dielectric heating has the advantage of a good homogeneity. The obtained temperature profiles for radio waves were more homogeneous compared to microwaves. Detailed studies showed that elimination of pests was not related to the application of the electromagnetic field itself, but due to the temperature increase.

A dynamic phenomenon of selective dielectric heating using radio-frequency energy is used to establish a continuous process for the elimination of organic pollutants from contaminated gas streams. The process consists of two phases characterized by adsorption and by regeneration utilizing in situ catalytic oxidation. The thermal regeneration of the packed bed is started by a so-called thermo-chromatographic pulse, i.e. a combined water/temperature pulse moving through the reactor with a packed bed containing both an adsorber and a catalytically active component (NaY zeolite and Pt, respectively). The pronounced temperature pulse is formed due to the strongly enhanced absorption of electromagnetic energy within a water pulse. This can be explained by the complex dependency of the energy absorption on both local moisture content and local temperature of the zeolite. As a result, the previously adsorbed organic contaminants are desorbed and, simultaneously, the catalyst is thermally activated leading to total oxidation of the released hydrocarbons. Thus, the gas stream can be permanently cleaned employing only one packed bed reactor. This has been demonstrated for various experimental conditions.

The influence of low-frequency (50 Hz) resistive and high-frequency (13.56 MHz, radio-frequency) dielectric heating in comparison to conventional heating on the microbial degradation of pollutants in soil was studied. The investigation of the biodegradation of model substances (benzoic acid, acetic acid, glucose, sodium acetate) added to a standard soil showed no significant influence of the electrical heating methods when compared withsamples heated to the same temperature in a water bath. Therefore, a hindrance of the microbial degradation could be excluded as it was done for soil respiration in a previous study. This finding is especially relevant for the application of these electrical heating methods for thermally enhanced soil bioremediation as an option for making in situ or ex situ clean-up processes more efficient.

The influence of electrical heating on microbiological processes in soil has been studied to evaluate the potential for enhancing biodegradation of pollutants by controlling the temperature. A frequency of 50 Hz (power line frequency) was applied for resistive heating. Dielectric heating was realized using a frequency of 13.56 MHz (radio frequency). Both techniques were compared with conventional heating in a water bath. For experimentsin laboratory and full scale, a model soil and a contaminated original soil were used. It was shown that under conditions capable for heating soil to 35 °C or even 60 °C, soil respiration as a measure for microbial activity was not hindered by electrical heating when temperature and moisture content were comparable with conventional heating. The variations of soil respiration were reversible upon temperature changes. Under certain conditions, periodical fluctuations of microbiological activity were observed. Several possible explanations including chronobiology are discussed without being able to provide an unambiguous interpretation for this effect.

Applying a new experimental design with a capillary glass reactor and plate electrodes outside of the reactor allowed the initiation of discharges in aqueous electrolytes under the influence of a radio-frequency (RF) electromagnetic field.This study focused on the mechanism leading to the initiation of such discharges in the restriction of a glass tube. The light emission correlated with discharges was analysed with optical emission spectroscopy. Electrons with energies between 20 and 45 eV were responsible for the dissociation of water molecules into (excited) OH, H and O radicals. Current–voltage characteristics were measured before and under discharge conditions. Modelling of the experimental setup and simulation of electrical field strength distribution support the hypothesis of the origin of discharges in general and experimental findings such as ring-shaped discharges and a minimum solution conductivity of about 1 S m−1 required for discharge initiation with RF voltages of 2 kV.

In situ radio-frequency heating (ISRFH) combined with soil vapor extraction was demonstrated at a contaminated field site of a former hydrotreatment plant in Zeitz near Leipzig. The project was carried out in several phases including cold soil vapor extraction for comparison. During the test, a soil volume of about 300 m3 was heated to an average temperature of 54 °C. As expected, the extraction rate for hydrocarbons (especially the main contaminant benzene) was markedly enhanced by soil heating. Furthermore, microbial degradation of organic compounds was supported. Although a total amount of approximately 1.4 t of hydrocarbons was removed from the soil, the demonstration project was not aimed at complete remediation of the site. Conditions limiting the extent of cleanup are discussed in detail and conclusions for an efficient application of ISRFH in soil remediation are derived whereas experiences from other sites are also implied.

A new type of water dissociation at ambient pressure initiated by the irradiation of aqueous electrolytes using an electromagnetic field with a frequency of 13.56 MHz is described in this study. A special reactor design allows the use of ex situ electrodes to form in situ electrical discharges in water vapour bubbles. The observed formation of molecular hydrogen (H2) and oxygen (O2) combined with the emission of light ('burning water' phenomenon) originates from a non-thermal plasma in water vapour bubbles. The influences of type of electrolyte, its concentration, pH value and external RF voltage on the gas formation rate as well as on the gas composition are presented.

In situ radio-frequency heating (ISRFH) was successfully applied during remediation of a former petrol station. Using a three-electrode array in combination with extraction wells for soil vapor extraction (SVE), pollution consisting mainly of benzene, toluene, ethylbenzene, xylenes, and mineral oil hydrocarbons (in total about 1100 kg) was eliminated from a chalk soil in the unsaturated zone. Specially designed rod electrodes allowed selective heating of a volume of approximately 480 m3, at a defined depth, to a mean temperature of about 50 °C. The heating drastically increased the extraction rates. After switching off ISRFH, SVE remained highly efficient for some weeks due to the heat-retaining properties of the soil. Comparison of an optimized regime of ISRFH/SVE with conventional “cold” SVE showed a reduction of remediation time by about 80 % while keeping the total energy consumption almost constant.

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Direct dielectric heating with radio-frequency (RF) electromagnetic fields is used to optimize a variety of processes in environmental technology, namely soil remediation by soil vapor extraction or biodegradation, adsorptive-catalytic off-gas treatment, thermal regeneration of drying agents in biogas or natural gas treatment and decontamination and/or drying of brickwork.