Search results for "metals"
showing 10 items of 2013 documents
Efficiency of biochar for reducing mobility of inorganic contaminants
2013
Anthropogenic activities have produced numerous sites with extensive contamination close to residential areas. Several physicochemical and biological remediation methods exist for remediation of metal contaminated soils and lands, such as soil washing, soil flushing, phytoremediation, and electrokinetics. Biochar (biologically derived charcoal) is produced by pyrolysis of biomasses under low oxygen conditions, and it can be applied for recycling organic waste in soils. The main objectives of the present study were to determine the possible use of biochar from forest ersidues (Populus nigra) in order to achieve a stabilization of inorganic contaminants by adsorption processes. Adsorption of …
Use of the eggshells in removing heavy metals from waste water - the process kinetics and efficiency
2019
Studies of the efficiency of Ni, Cu and Cd cations removal from water solutions were carried out, with the use of clay limestone, hen eggshells from eggs for consumption and hen eggshells after hatching, which main element is calcium carbonate. Hen eggshells are a waste product, which can be used as a substitute of clay limestone in removing heavy metals from wet flue gas desulphurisation installation. Mixed solutions of Ni, Cu and Cd were used in the research, with the composition similar to the waste water from wet flue gas desulphurisation installation: Ni (0.009-0.053 mmol/dm3), Cu (0.008-0.057 mmol/dm3)and Cd (0.003-0.008 mmol/dm3). The metals were determined by flame atomic absorption…
Reduction and catalytic behaviour of heterobimetallic copper–lanthanide oxides
2008
Abstract The reduction of the heterobimetallic copper–lanthanide oxides 2CuO·CeO2 and 3CuO·Ln2CuO4 (Ln = La, Pr, Nd) was studied by H2-TG/DTA and H2-TPR. All systems exhibit two main reduction steps accompanied by mass losses in the temperature range 20–1000 °C. The first step was attributed to CuO reduction, whereas the second step is due either to copper reduction in the Ln2CuO4 phase with the concomitant formation of Ln2O3 or to the surface reduction of CeO2. The products were characterized by XRD, SEM, EDX, and BET techniques and are better described as supported copper type materials. They were active for the mesityl oxide (4-methyl-2-penten-2-one) gas phase hydrogenation.
Metallic nanoparticles exhibit paradoxical effects on oxidative stress and pro-inflammatory response in endothelial cells in vitro
2007
Particulate matter is associated with different human diseases affecting organs such as the respiratory and cardiovascular systems. Very small particles (nanoparticles) have been shown to be rapidly internalized into the body. Since the sites of internalization and the location of the detected particles are often far apart, a distribution via the blood stream must have occurred. Thus, endothelial cells, which line the inner surface of blood vessels, must have had direct contact with the particles. In this study we tested the effects of metallic nanoparticles (Co and Ni) on oxidative stress and proinflammatory response in human endothelial cells in vitro. Exposure to both nanoparticle types…
Aqueous-phase reactive species formed by fine particulate matter from remote forests and polluted urban air
2021
In the aqueous phase, fine particulate matter can form reactive species (RS) that influence the aging, properties, and health effects of atmospheric aerosols. In this study, we explore the RS yields of aerosol samples from a remote forest (Hyytiälä, Finland) and polluted urban locations (Mainz, Germany; Beijing, China), and we relate the RS yields to different chemical constituents and reaction mechanisms. Ultra-high-resolution mass spectrometry was used to characterize organic aerosol composition, electron paramagnetic resonance (EPR) spectroscopy with a spin-trapping technique was applied to determine the concentrations of ⚫OH, O2⚫-, and carbon- or oxygen-centered organic radicals, and a …
Catalytic effect of transition metals (copper, iron, and nickel) on the foaming and properties of sugar-based carbon foams
2019
Abstract Recently, bio-based carbon foams have gained much interest in many chemical industry fields because of their unique structure and properties. This study provides new information on the effects of catalytic metals (iron, nickel, and copper) on the foaming process. Specifically, the effects of these catalysts on the density, foam growth, and cell size and then further on the pore size distribution and specific surface areas after the physical activation are considered. Furthermore, some of the activated sugar foams were used in adsorption tests using methylene blue as adsorbent. Results showed that the highest effect on foam density was obtained using the iron catalyst in the foaming…
Role of elastic and electronic interactions in trapping of hydrogen by impurities in transition metals
1985
The interplay between the lattice distortion and the electronic contributions to the trapping of migrating hydrogen isotopes by substitutional impurities is investigated. We use a comprehensive calculational scheme incorporating (i) the effective-medium theory for the electronic interaction, (ii) the lattice Green’s function for elastic coupling, and (iii) the hydrogen quantum motion. The calculations for Ti and Cr impurities in V host show that lattice strain effects dominate. Cr, which otherwise provides an electronic trap site, does not induce trapping when elastic effects are incorporated. The situation in the case of Ti is just the reverse. We find no isotope dependence of the binding …
Pneumococcal histidine triads – involved not only in Zn2+, but also Ni2+ binding?
2018
Polyhistidine triad proteins, which participate in Zn2+ uptake in Streptococcus pneumoniae, contain multiple copies of the HxxHxH (histidine triad motif) sequence. We focus on three such motifs from one of the most common and well-conserved polyhistidine triad proteins, PhtA, in order to understand their bioinorganic chemistry; particular focus is given to (i) understanding which of the PhtA triads binds Zn2+ with the highest affinity (and why) and (ii) explaining whether Ni2+ (also crucial for bacterial survival and virulence) could potentially outcompete Zn2+ at its native binding site. There is no significant difference in the stability of zinc(II) complexes with the three studied protei…
Structural Origin of Metal Specificity in Isatin Hydrolase from Labrenzia aggregata Investigated by Computer Simulations.
2017
We performed quantum-chemical calculations, ab initio molecular dynamics, hybrid quantum mechanics/molecular mechanics (QM/MM) and enhanced sampling metadynamics simulations to investigate the origin of metal specificity in isatin hydrolase from Labrenzia aggregata. The peculiar octahedral binding geometry of the Mn2+ ion in the Michaelis complex includes both the isatin substrate and the catalytic water within the first coordination shell of the cation. Our calculations show that the same arrangement of the ligands cannot be efficiently achieved in the presence of other small divalent metal cations such as Zn2+ or Cu2+ . On the contrary, bulkier alkaline-earth cations such as Mg2+ , which …
Asymmetric [N–I–N]+halonium complexes in solution?
2020
Assessment of the solution equilibria of [bis(pyridine)iodine(I)]+ complexes by ESI-MS and NMR reveals the preference of iodine(I) to form complexes with a more basic pyridine. Mixtures of symmetric [bis(pyridine)iodine(I)]+ complexes undergo statistical ligand exchange, with a predominant entropic driving force favoring asymmetric systems. The influence of ligand basicity, concentration, temperature, and ligand composition is evaluated. Our findings are expected to facilitate the investigations, and the supramolecular and synthetic applications of halonium ions’ halogen bonds. peerReviewed