Search results for "Metal Ion"

Komplexierung von Übergangsmetall-Ionen mit substituierten Azamakrocyclen: Induktion columnarer Mesophasen durch molekulare Erkennung

1991

Preparation and characterization of organofunctionalized bentonite clay bearing aminophosphonic groups in heavy metal uptake

2019

Abstract Bentonite (Bnt) with covalently immobilized N-propylaminodi(methylenephosphonic) groups (Bnt-ADPA) was obtained through a two-step synthesis including aminosilanization and phosphorylation of resulting aminobentonite through Moedritzer-Irani reaction. The grafting of an aminosilane layer in the interplanar space of the bentonite was investigated by XRD, and the presence of N and P-containing groups was confirmed by FTIR, 31P and 29Si MAS NMR. The immobilization of the organic functional groups increased the interplanar distance in bentonite matrix at 52% that essentially improved filtration properties compared to raw bentonite. The number of surface acid groups was evaluated to 0.8…

Surface characterisation of metal ions loaded TiO2 photocatalysts: structure–activity relationship

2004

Abstract Transition metal loaded TiO 2 powders were characterised and tested for the photodegradation of some organic acids. Both Lewis and Bronsted surface acid sites were present in the samples containing large amounts of Mo, V and W. The Bronsted sites are associated to the presence of the transition metals as they do not exist in the unloaded support, and in particular to the presence of these metals in high oxidation states. The trend of the pzc values of the various powders matches rather well both with the surface acidity of the samples experimentally determined by NH 3 adsorption and with a scale of acidity/basicity for bulk binary oxides. XPS investigation indicates that only the p…

Cr(VI) sorption by intact and dehydrated Candida utilis cells in the presence of other metals

2002

This study examined the Cr(VI), Cu(II), Zn(II), Cd(II), Pb(II) sorption by intact and dehydrated Candida utilis cells. The anion [Cr2O7]2− and cation Me2+ sorption kinetics was investigated in both single- and dual-metal situations. Uptake of chromate anions occurred much more slowly singularly than with metal cations. A combination of Pb or Cu and chromate anions gave a synergistic effect for Cr(VI) sorption, but not Cd and Zn, which inhibited Cr(VI) sorption by dehydrated cells. The use of alcian blue to occupy maximum vacant adsorption sites on the cell surface unexpectedly did not influence further adsorption of Me2+. Metal uptake by C. utilis was 7 mg (135 μM) Cr, 23 mg (362 μM) Cu, 39…

Distribution of Cr and Pb in artificial sea water and their sorption in marine sediments: an example from experimental mesocosms

2016

The uptake of two heavy metals (chromium and lead) in sediments in experimental mesocosms under exposure to different metal concentrations was evaluated by monitoring their concentrations over time both in seawater and in sediment. Two separate experiments under laboratory-controlled conditions were carried out for the two metals. Sediments were collected from a protected natural area characterized by low anthropic influence and were placed in mesocosms that were housed in aquaria each with seawater at a different metal concentration. At pre-established time intervals, seawater and sediment samples were collected from each mesocosm for chemical analyses. Quantification of chromium and lead …

Copper(ii) and zinc(ii) dependent effects on Aβ42 aggregation: a CD, Th-T and SFM study

2013

A? aggregation is a central event in Alzheimer's disease (AD). In vitro evidence indicates that A? aggregation and fibrillogenesis are significantly influenced by the employed experimental conditions. Indeed, although it is widely established that metal ions, such as copper and zinc, have significant effects on the A? aggregation process, their actual role in A? fibrillogenesis is still debated. In this work the effects of a molar excess of zinc(ii) and/or copper(ii) ions on the A?42 aggregation process and the morphology of the resultant aggregates have been compared in samples exhibiting different initial conformations. CD spectroscopy, Th-T-induced fluorescence and Scanning Force Microsc…

Thermal aggregation and ion-induced cold-gelation of bovine serum albumin

2009

Protein cold-gelation has recently received particular attention for its relevance in bio and food technology. In this work, we report a study on bovine serum albumin cold-gelation induced by copper or zinc ions. Metal-induced cold-gelation of proteins requires two steps: during the first one, the heat treatment causes protein partial unfolding and aggregation; then, after cooling the solution to room temperature, gels are formed upon the addition of metal ions. The thermally induced behaviour has been mainly investigated through different techniques: Fourier transform infrared (FTIR) spectroscopy, circular dichroism, dynamic light scattering (DLS) and rheology. Data have shown that the agg…

Chemical-state analyses of Ni, Zn, and W ions in NiWO$_4$-ZnWO$_4$ solid solutions by X-ray photoelectron spectroscopy

2022

The chemical states of Ni, Zn, and W in microcrystalline NiWO$_4$-ZnWO$_4$ solid solutions were studied by X-ray photoelectron spectroscopy. The recorded spectra of the Ni 2p, Zn 2p, and W 4f photoelectron lines and Ni L$_2$M$_{23}$M$_{45}$, Zn L$_3$M$_{45}$M$_{45}$, and W N$_4$N$_{67}$N$_{7}$ Auger-transition lines show pronounced changes with increasing Zn concentration. The positions of the resolved photoelectron and Auger-transition lines were combined to construct so-called chemical-state plots (Wagner or Auger-parameter plots) for metal ions in solid solutions. With increasing Zn concentration, the Auger parameter increases for Ni and decreases for W, thus evidencing a lowering and an…

Magnetic Exchange between Orbitally Degenerate Metal Ions: The Problem of Magnetic Anisotropy

2001

Abstract In this paper we show that a strong magnetic anisotropy appears in exchange mixed–valence clusters containing orbitally degenerate metal ions. Combining an effective Hamiltonian approach with the technique of the irreducible tensor operators (ITO) and pseudoangular momentum representation we have solved the problem of magnetic exchange in localized and delocalized (mixed–valence) systems with different overall symmetries ( D 2 h , D 3 h , D 4 h ). The energy pattern as well as the character of the magnetic anisotropy is closely related to the ground term of the ions, electron transfer pathways, and overall symmetry of the system being affected also by the local crystal fields, spin…

Rational design of aminoanthraquinones for colorimetric detection of heavy metal ions in aqueous solution

2011

A family of water-soluble colorimetric chemosensors incorporating an anthraquinone signalling subunit functionalized with a polyamine chain that bears hydrophilic diethoxyphosphoryl moieties was prepared with the aim of assaying metal cations. The outstanding UV-Vis absorption properties of the 1-aminoanthraquinone chromophore allowed the efficient visual detection and quantification of copper(II) ions by chelators L(1)-L(3) in buffered aqueous solution. Moreover, the visible response of L(2) is not interfered by addition of large excesses of 13 common metal ions, whereas chemosensor L(3) produces also a color change in the presence of equimolar amounts of lead(II). Considering the 134 nm g…