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329 results on '"Kahlert H"'

1. Potential deterioration of chemical water quality due to trace metal adsorption onto tire and road wear particles -Environmentally representative experiments

Author

Rocha Vogel, Angus, Kolberg, Yannik, Schmidt, Matthias, Kahlert, H., von Tümpling, Wolf, Rocha Vogel, Angus, Kolberg, Yannik, Schmidt, Matthias, Kahlert, H., and von Tümpling, Wolf

Abstract

Tire wear particles are an increasing issue in particle emissions to the environment. Germany-wide approximately 100,000 t tire wear particles are emitted every year into the environment which are estimated to be one third of the microplastic emissions. Up to 20% are estimated to reach inland surface waters. Their behavior in the aquatic environment is understudied. Tire wear particles have an overly hydrophobic surface that is capable of adsorbing substances like trace elements. In this study we investigated the adsorption and desorption of trace metals onto and from the particle surface of tire-related samples in water samples of the Freiberger Mulde, a river with naturally elevated concentration of trace elements. The priority trace metals Cr, Ni, Zn, Cd and Pb show a significant adsorption onto the particle surface of tire-related samples. Tire wear particles themselves revealed adsorption of mainly Ni, Cd and Pb. Regarding the German classification for suspended matter in freshwaters, an endangering of the chemical water quality is expected due to the adsorption process and not due to the particles themselves. Upcoming electromobility is expected to increase the Zn (increased tire abrasion) and decrease the Cu amount (reduced brake abrasion) released to freshwaters.

Published
2024

4. Detailed insights in adsorption process of heavy metals on tire wear particles

Author

Glaubitz, F., Rocha Vogel, Angus, Kolberg, Yannik, von Tümpling, Wolf, Kahlert, H., Glaubitz, F., Rocha Vogel, Angus, Kolberg, Yannik, von Tümpling, Wolf, and Kahlert, H.

Abstract

Road traffic induced tire wear particles (TWP) attracted widespread attention due to their potential environmental impact. Here, the adsorption process of heavy metals like Pb2+ and Cd2+ on tire wear particles produced by filing (TWP-f) is studied to elucidate the underlying kinetics and thermodynamics. This work includes voltammetric experiments to investigate the concentration and temperature dependency of the adsorption. The adsorption kinetics in buffer solution spiked with heavy metals follows a pseudo-second-order rate equation involving rate-controlling boundary layer adsorption and a side-by-side intraparticle diffusion process. Meanwhile, the adsorption tendencies under the studied conditions for TWP-f were Pb2+ > Cd2+. The equilibrium adsorption data were modulated by the Langmuir, Freundlich, and Dubinin-Radushkevich (DR) isotherms. Both the Freundlich and DR isotherms were found to be feasible for describing the adsorption on TWP-f. The adsorption energy obtained from the DR isotherm is 1.6 kJ mol−1 for Pb2+ and 2 kJ mol−1 for Cd2+, indicating physisorption as the dominating force. According to the Freundlich isotherm, multilayer adsorption is proposed. The thermodynamic parameters show that the adsorption of Pb2+ and Cd2+ is endergonic. Due to small Gibbs enthalpy values near the thermodynamic equilibrium, the adsorption process is mainly dependent on the ambient conditions. So, close-to-nature experiments were conducted to verify the received results. Therefore, tire and road wear particles including road sediments (TRWP+RS) were added to prefiltered freshwater samples of the river Freiberger Mulde (having naturally elevated trace element concentrations). The adsorption kinetics were investigated by ICP-MS/MS emphasizing the pseudo-second-order rate equation. Moreover, it is suggested that the tire wear particles in the TRWP+RS sample are majorly responsible for the adsorption of at least Cd2+.

Published
2023

18. On the determination of the diffusion coefficients of electrons and of potassium ions in copper(II) hexacyanoferrate(II) composite electrodes

Author

Kahlert, H., Retter, U., Lohse, H., Siegler, K., and Scholz, F.

Subjects
Copper compounds -- Analysis, Electrodes, Ion selective -- Evaluation, Electronic structure -- Analysis, Oxidation-reduction reaction -- Analysis, Chemicals, plastics and rubber industries
Abstract

Cyclic voltammetry and electrochemical impedance spectroscopy were used in determining the diffusion coefficients of electrons and potassium ions in graphite, paraffin and copper(II) hexacyanoferrate(II) (Cu hcf). These compounds show good potential as materials for new ion-selective electrodes. The redox reaction of lattice metal ions are accompanied by a reversible exhange of cations between the electrolyte solution and interstitial holes of the solid compound. Results show the diffusion coefficient is due to the semiconductor properties of Cu hcf. Separating cation diffusion from electron hopping has not been achieved.

Published
1998

47. Acoustic phonons of polymeric sulfur nitride, (SN)x

Author

Pintschovius, L., Wendel, H., Kahlert, H., Ehlers, J., editor, Hepp, K., editor, Kippenhahn, R., editor, Weidenmüller, H. A., editor, Zittartz, J., editor, Beiglböck, W., editor, Pál, L., editor, Grüner, G., editor, Jánossy, A., editor, and Sólyom, J., editor

Published
1977
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49. 'Allergen engineering': variants of the timothy grass pollen allergen Phl p 5b with reduced IgE-binding capacity but conserved T cell reactivity

Author

Schramm G, Kahlert H, Suck R, Weber B, Ht, Stüwe, Wd, Müller, Albrecht Bufe, Wm, Becker, Mw, Schlaak, Jäger L, Cromwell O, and Fiebig H

Subjects
T-Lymphocytes, Immunology, Genetic Variation, Allergens, Immunoglobulin E, Poaceae, Protein Engineering, Histamine Release, Cell Line, Clone Cells, Immunology and Allergy, Humans, Pollen, Binding Sites, Antibody, Epitope Mapping, Plant Proteins, Skin Tests
Abstract

One problem of conventional allergen-specific immunotherapy is the risk of anaphylactic reactions. A new approach to make immunotherapy safer and more efficient might be the application of engineered allergens with reduced IgE-binding capacity but retained T cell reactivity. Using overlapping dodeca-peptides, the dominant T cell epitopes of the timothy grass pollen allergen Phl p 5b were identified. By site-directed mutagenesis outside these regions, point and deletion mutants were generated. Allergen variants were analyzed for IgE-binding capacity with sera of different grass pollen allergic patients by Western blotting, Dot blotting, and EAST inhibition test, and for histamine releasing capacity with peripheral blood basophils from different patients. The deletion mutants revealed significantly reduced IgE reactivity and histamine releasing capacity, compared with the wild-type Phl p 5b. Furthermore, in vivo skin prick tests showed that the deletion mutants had a significantly lower potency to induce cutaneous reactions than the wild-type Phl p 5b. On the other hand, T cell clones and T cell lines from different allergic patients showed comparable proliferation after stimulation with allergen variants and wild-type Phl p 5b. Considering their reduced anaphylactogenic potential together with their conserved T cell reactivity, the engineered allergens could be important tools for efficient and safe allergen-specific immunotherapy.

Published
1999

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