Etelka Tombacz - Academia.edu (original) (raw)

Papers by Etelka Tombacz

$Research paper thumbnail of Applications of light and X-ray scattering to characterize the fractal properties of soil organic matter$

Geoderma, Mar 1, 1999

Soil organic matter (SOM) is a heterogeneous assemblage of organic molecules that interact in a v... more Soil organic matter (SOM) is a heterogeneous assemblage of organic molecules that interact in a variety of ways with each other, with soil mineral surfaces, and with soil mineral colloids. Because of SOM's heterogeneity it is very difficult to define its surface, or the surfaces of the composite materials produced by its interaction with soil minerals. Yet it is at these interfaces where chemical reactions that involve SOM take place. Results are presented which describe the fractal characterization of humic materials using static X-ray and light scattering, and dynamic light scattering (DLS) experiments. The applicability of static X-ray scattering to the direct determination of the fractal dimension of humic materials is established using DLS. Over the length scales studied, humic materials are surface fractals in the solid state, and mass fractals in solution. The longer characterization length scales possible in the static light scattering experiments suggest that at longer characterization length scales humic acid is not fractal, at least not under the solution conditions employed in these experiments. Application of fractal analysis to the characterization of the surface morphology of soil and peat humin samples, the calculation of the hydrodynamic radius of humic acid particles, and the study of humic acid aggregation are discussed.

Hungarian Journal of Industrial Chemistry, Sep 27, 2022

Humic substances are natural substances that are continuously formed from the decay of plant resi... more Humic substances are natural substances that are continuously formed from the decay of plant residues. These materials have a very diverse range of properties, making them versatile. According to many new studies, these humic substances also exhibit antioxidant propensities. The aim of this paper was to shed light on whether humic substances really have antioxidant properties.

Springer eBooks, Apr 1, 2009

ABSTRACT

Nanomaterials, Dec 4, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of Magnetism and Magnetic Materials, Apr 1, 2017

The development of protein corona around nanoparticles upon administration to the human body is r... more The development of protein corona around nanoparticles upon administration to the human body is responsible in a large part for their biodistribution, cell-internalization and toxicity or biocompatibility. We studied the influence of the chemical composition of polyelectrolyte shells (citric acid (CA) and poly(acrylic-co-maleic acid) (PAM)) of core-shell magnetite nanoparticles (MNPs) on the evolution of protein corona in human plasma (HP). The aggregation state and zeta potential of the particles were measured in the range of HP concentration between 1 and 80 (v/v)% 3 min and 20 h after dispersing the particles in HP diluted with Tris buffered saline. Naked MNPs aggregated in HP solution, but the carboxylated MNPs became stabilized colloidally at higher plasma concentrations. Significant differences were observed at low plasma concentration. CA@MNPs aggregated instantly while the hydrodynamic diameter of PAM@MNP increased only slightly at 1-3 v/v % HP concentrations. The observed differences in protein corona formation can be explained by the differences in the steric effects of the polycarboxylate shells. It is interesting that relatively small but systematic changes in zeta potential alter the aggregation state significantly.

Journal of Molecular Structure, Jul 1, 2017

The delamination-restacking properties of MgAl-layered double hydroxide (MgAl-LDH) were studied i... more The delamination-restacking properties of MgAl-layered double hydroxide (MgAl-LDH) were studied in various solvents. The LDH samples were successfully delaminated in polar amides (formamide, Nmethylformamide, N-methylacetamide). Usually, delamination was finalized by ultrasonic treatment. As rehydrating solutions, numerous Na-salts with single-, double-and triple-charged anions were used. Reconstruction was accomplished with anions of one or two negative charges, but triple-charged ones generally disrupted the rebuilding process, likely, because their salts with the metals of the LDH are very stable, and the thin layers can more readily transform to salts than the ordered materials. Samples and delamination-restacking processes were characterized by X-ray diffractometry (XRD), infrared spectroscopy (IR), dynamic light scattering (DLS), scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX).

Else Kröner-Fresenius Symposia, 2011

... Basel, Karger, 2011, vol 2, pp 35–52 Synthesis of Magnetic Nanoparticles and Magnetic Fluids ... more ... Basel, Karger, 2011, vol 2, pp 35–52 Synthesis of Magnetic Nanoparticles and Magnetic Fluids for Biomedical Applications L. Vékása, b Etelka Tombácze Rodica Turcud I. Morjanc MV Avdeevf-Theodora Krasia-Christoforoug V. Socoliuca aLaboratory ofMagnetic Fluids ...

Molecules, Sep 26, 2022

Journal of Aerosol Science, Sep 1, 2001

Nanomaterials, Apr 26, 2022

Advances in Materials Science and Engineering, 2018

Nanostructured composite dispersions containing magnetic nanoparticles (MNPs) and graphene oxide ... more Nanostructured composite dispersions containing magnetic nanoparticles (MNPs) and graphene oxide (GO) lamellae have been prepared by a simple and easily scalable room temperature procedure. We show that, owing to the enormous surface area and negative surface charge developed in aqueous GO suspensions, large amounts of positively charged MNPs can be electrostatically attached to the layered host. is procedure is superior to many previous synthesis pathways because it exploits the chargeregulated adhesion of naked MNPs to GO resulting in the formation of stable and uniform nanocomposite materials in a wide composition range without any preliminary functionalization steps or harsh conditions that may lead to chemical degradation of the graphene-based nanosheets.

International Journal of Environmental Science and Technology, Jul 29, 2020

Since adsorption is one of the best ammonium removal methods, great efforts have been made to ide... more Since adsorption is one of the best ammonium removal methods, great efforts have been made to identify new low-cost and efficient adsorbents from agricultural waste and by-products due to their abundant availability, low-cost and eco-friendly advantages, in addition to the possibility of recycling ammonium back into agricultural processes. In this study, a series of batch experiments were performed to detect new bio-adsorbents for ammonium ions removal. Among the materials tested, pomegranate peel powder showed a high affinity to adsorb ammonium ions and, furthermore, available information on ammonium adsorption by this biomaterial is still missing from the literature. First, pomegranate peel powder was characterized by the determination of different parameters such as zeta potential, iodine number, Fourier-transform infrared spectroscopy analysis, scanning electron microscopy, particle size distribution and porosity. Then, the impact of various parameters, such as pH, contact time, stirring speed, adsorbent dose and adsorbate concentration in the adsorption process, was investigated. The highest ammonium removal capacity was obtained at pH = 4 using 400 mg of pomegranate peel powder and a stirring speed of 150 rpm for an initial concentration of ammonium of 30 mg/L. The system (adsorbent, adsorbate and solution) reached equilibrium after 2 h and the data fit well with the Langmuir model with a maximum monolayer adsorption capacity of 6.18 mg/g, while kinetics were well described by the pseudo-second-order model. These results introduce pomegranate peel powder as a promising bio-adsorbent to remove and recover ammonium from aqueous solutions.

Applied Catalysis B-environmental, Jun 7, 2010

$Research paper thumbnail of Characterization of humic acid fractions by potentiometric acid-base titration, UV-VIS and NMR spectroscopy$

Plasma Processes and Polymers, Oct 20, 2021

The work aims to determine the long‐term stability of reactive oxygen and nitrogen species (RONS)... more The work aims to determine the long‐term stability of reactive oxygen and nitrogen species (RONS)‐enriched gelatin solutions and of plasma‐activated physiological solutions produced with an atmospheric pressure surface‐wave microwave discharge. It is demonstrated that the , and concentrations are quasi‐stable during 1 month of storage in the 0.5%–2% gelatin solutions prepared with plasma‐activated water, Ringer's (PAR), and phosphate‐buffered saline (PAPBS) solutions, respectively, even at acidic pH 4.5–5.5 conditions. The trapping of RONS is attributed to the protein network developed with gelation. The salt content of the physiological solutions influences the RONS creation and deposition, while stabilizes the 6.5 and 7.2 pH, which ensures the stability of the PAR and PAPBS, respectively, for months.

Atmospheric Environment, Mar 1, 2017

h i g h l i g h t s Complete monolayer coating of humic acid (HA) was created on clay particles. ... more h i g h l i g h t s Complete monolayer coating of humic acid (HA) was created on clay particles. Freshly emitted soil derived dust can be modelled by this method. Absorption EF, k of complex refractive index, SSA, coating thickness were determined. Coating promotes the dispersion of particles and cause EF~6e7 in the UVeVIS range. Base soluble HA fraction of MD may have important role in global radiative transfer.