Metal ions in aqueous solution

About: Metal ions in aqueous solution is a research topic. Over the lifetime, 28611 publications have been published within this topic receiving 715033 citations.

Oxidative mechanisms in the toxicity of metal ions

Abstract: The role of reactive oxygen species, with the subsequent oxidative deterioration of biological macromolecules in the toxicities associated with transition metal ions, is reviewed. Recent studies have shown that metals, including iron, copper, chromium, and vanadium undergo redox cycling, while cadmium, mercury, and nickel, as well as lead, deplete glutathione and protein-bound sulfhydryl groups, resulting in the production of reactive oxygen species as superoxide ion, hydrogen peroxide, and hydroxyl radical. As a consequence, enhanced lipid peroxidation. DNA damage, and altered calcium and sulfhydryl homeostasis occur. Fenton-like reactions may be commonly associated with most membranous fractions including mitochondria, microsomes, and peroxisomes. Phagocytic cells may be another important source of reactive oxygen species in response to metal ions. Furthermore, various studies have suggested that the ability to generate reactive oxygen species by redox cycling quinones and related compounds may require metal ions. Recent studies have suggested that metal ions may enhance the production of tumor necrosis factor alpha (TNF alpha) and activate protein kinase C, as well as induce the production of stress proteins. Thus, some mechanisms associated with the toxicities of metal ions are very similar to the effects produced by many organic xenobiotics. Specific differences in the toxicities of metal ions may be related to differences in solubilities, absorbability, transport, chemical reactivity, and the complexes that are formed within the body. This review summarizes current studies that have been conducted with transition metal ions as well as lead, regarding the production of reactive oxygen species and oxidative tissue damage.

Low-cost adsorbents for heavy metals uptake from contaminated water: a review.

Abstract: In this article, the technical feasibility of various low-cost adsorbents for heavy metal removal from contaminated water has been reviewed. Instead of using commercial activated carbon, researchers have worked on inexpensive materials, such as chitosan, zeolites, and other adsorbents, which have high adsorption capacity and are locally available. The results of their removal performance are compared to that of activated carbon and are presented in this study. It is evident from our literature survey of about 100 papers that low-cost adsorbents have demonstrated outstanding removal capabilities for certain metal ions as compared to activated carbon. Adsorbents that stand out for high adsorption capacities are chitosan (815, 273, 250 mg/g of Hg(2+), Cr(6+), and Cd(2+), respectively), zeolites (175 and 137 mg/g of Pb(2+) and Cd(2+), respectively), waste slurry (1030, 560, 540 mg/g of Pb(2+), Hg(2+), and Cr(6+), respectively), and lignin (1865 mg/g of Pb(2+)). These adsorbents are suitable for inorganic effluent treatment containing the metal ions mentioned previously. It is important to note that the adsorption capacities of the adsorbents presented in this paper vary, depending on the characteristics of the individual adsorbent, the extent of chemical modifications, and the concentration of adsorbate.

The kinetics of sorption of divalent metal ions onto sphagnum moss peat

Abstract: A pseudo-second order rate equation describing the kinetics of sorption of divalent metal ions onto sphagnum moss peat at different initial metal ion concentrations and peat doses has been developed. The kinetics of sorption were followed based on the amounts of metal sorbed at various time intervals. Results show that sorption (chemical bonding) might be rate-limiting in the sorption of divalent metal ions onto peat during agitated batch contact time experiments. The rate constant, the equilibrium sorption capacity and the initial sorption rate were calculated. From these parameters, an empirical model for predicting the sorption capacity of metal ions sorbed was derived.

Dendrimer-Encapsulated Metal Nanoparticles: Synthesis, Characterization, and Applications to Catalysis

Abstract: This Account reports the synthesis and characterization of dendrimer-encapsulated metal nanoparticles and their applications to catalysis. These materials are prepared by sequestering metal ions within dendrimers followed by chemical reduction to yield the corresponding zerovalent metal nanoparticle. The size of such particles depends on the number of metal ions initially loaded into the dendrimer. Intradendrimer hydrogenation and carbon−carbon coupling reactions in water, organic solvents, biphasic fluorous/organic solvents, and supercritical CO2 are also described.

Interactions of metal ions with chitosan-based sorbents: a review

Abstract: Metal cations can be adsorbed by chelation on amine groups of chitosan in near neutral solutions. In the case of metal anions, the sorption proceeds by electrostatic attraction on protonated amine groups in acidic solutions. However, the presence of ligands and the pH strongly control sorption performance (sorption isotherm) and the uptake mechanism (changing the speciation of the metal may result in turning the chelation mechanism into the electrostatic attraction mechanism). Several examples are discussed with precious metals (Pd, Pt), oxo-anions (Mo, V) and heavy metals (Cu, Ag). Sorption performance (equilibrium uptake but also kinetics) is also strictly controlled by other structural parameters of the polymer (degree of deacetylation, crystallinity for example) that control swelling and diffusion properties of chitosan. The identification of the limiting steps of the sorption process helps in designing new derivatives of chitosan. Diffusion properties may be improved by physical modification of chitosan (manufacturing gel beads, decreasing crystallinity). Selectivity can be enhanced by chemical modification (grafting, for example, sulfur compounds). Several examples are discussed to demonstrate the versatility of the material. This versatility allows the polymer to be used under different forms (from water soluble form, to solid form, gels, fibers, hollow fibers …) for polymer-enhanced ultrafiltration and sorption processes. These interactions of metal ions with chitosan can be used for the decontamination of effluents, for the recovery of valuable metals but also for the development of new materials or new processes involving metal-loaded chitosan. Several examples are cited in the design of new sorbing materials, the development of chitosan-supported catalysts, the manufacturing of new materials for opto-electronic applications or agriculture (plant disease treatment …).