Selectivity adsorption of metal ions

Selective and reversible adsorption of gaseous molecules such as dioxygen, carbon monoxide, ethylene, acetylene, and dinitrogen have been performed by the use of suitable macromolecule-metal complexes. Selective adsorption of metal ions such as UO has also been studied using polymeric ligands. 

In spite of the importance of bleaches in oxidation dyeing, very few technical improvements apart from formulation aspects have occurred recently in this field. The selective adsorption of metal ions [21], especially of iron(n) salts [22], on melanin has been proposed for gentler bleaching of human hair. This process has achieved no more acceptance than the use of peroxocarboxylic acids or their precursors, which are important as bleaching intensifiers in textile bleaching. 

Tsuchia, E., Nishide, H. Selective adsorption of metal ions to polymeric amines immobilized by template reaction, in Polymeric amines and ammonium salts (ed.) Goethals, E. J., p. 271, New York. Pergamon Press 1980... 

Y. Koide, H. Senba, H. Shosenji, M. Maeda and M. Takagi, Selective adsorption of metal ions to surface template resins prepared by emulsion polymerization using 10-(p-vinylphenyl)decanoic acid, Bull. Chem. Soc. Jpn., 1996, 69, 125 M. Yoshida,... 

Nishide, H. Tsuchida, E. Selective adsorption of metal ions on poly(4-vinylpyridine) resins in which the hgand chain is immobilized by crosslinking. Makromol. Chem. 1976, 177, 2295 2301. 

Generally speaking, homogeneous nucleation needs the supersaturation level higher than heterogeneous one. In the system consisting of support solid and metal salt solution, the nucleation occurs on the surfaces of the solid. The selective reductive deposition is performed by the adsorption of metal ion or complexes on the surfaces and hereby the reduction. Namely, the initial adsorption of metal ions or complexes is the key point of this technique. Hence, key points of this method are... 

Aside from contact electrization, local accumulation of charges takes place as a result of mechanical separation and formation of a double electrical layer (DEL). Mechanical separation of charges is brought about by exfoliation of adhesive films from the metal or semiconducting samples. DEL may arise in response to chemical interactions of two phases or as a result of selective adsorption of similar ions, e.g. in the presence of oriented dipoles on the contact surface of one of the phases. Electrization can also be induced by the donor-acceptor (DA) interaction, since in agreement with the electrostatic theory of adhesion DEL are formed at the interface of two substances at the expense of DA links and govern the efficiency of adhesive interactions [41]. 

Yang and Cheng (2003) have also reported the metal uptake abiUties of macro cyclic diamine derivative of chitosan. The polymer has high metal uptake abilities, and the selectivity property for the metal ions was improved by the incorporation of azacrown ether groups in the chitosan. The selectivity for adsorption of metal ions on polymer was found to be Ag+> Co >Ci. These results reveal that the new type chitosan-crown ethers will have wide ranging applications for the separation and concentration of heavy metal ions in environmental analysis. 

Inoue, K., Baba, Y, Yoshizuka, K., Noguchi, H., Yoshizaki, M Selectivity Series in the Adsorption of Metal Ions on a Resin. Crosshnking Copper (fl) Complexed Chi-... 

Kanai, H., Navarrete, R.C., Macisko, C.W. Scriven, L.E. (1992) Rheol. Acta 31 333 Kandori, K. Ishikawa,T. (1991) Selective adsorption of water on amorphous ferric oxide hydroxide. Langmuir 7 2213-2218 Kandori, K. Aoki,Y. Yasukawa, A. Ishikawa, T. (1998) Effects of metal ions on the morphology and structure of hematite particles produced from forced hydrolysis reaction. 

The kinetics of the ammoxidation of xylenes over a vanadium catalyst and mixed vanadium catalysts were studied. The reaction rate data obtained were correlated with the parallel consecutive reaction scheme by the rate equations based upon the Langmuir-Hinshelwood mechanism where the adsorption of xylenes was strong. The reaction rates of each path are remarkably affected by the kind of xylene and catalyst. The results of the physical measurement of catalysts indicated that the activity and the selectivity of reaction were affected by the nature and the distribution of metal ions and oxygen ion on catalyst surface. 

On the other hand, a catalyst in which the CrV04 was one of major constituents had little catalytic activity for the ammoxidation of xylene. These observations indicate that the nature and the distribution of metal ions and oxygen ion on the catalyst surface affect the catalytic activity and selectivity. It is difficult to predict the relationship between the adsorptivity of reactants and the physical properties of catalyst, but it may be assumed that adding more electronegative metal ions affects the electronic properties of the vanadium ion, which functions as an adsorption center. Further details on the physical properties of catalysts for the ammoxidation of xylenes will be reported later. 

The oxide, a-quartz, was selected as the substrate for the present and continuing studies of metal ion adsorption. It is of considerable importance in several practical situations—e.g., water purification and ore flotation—and has the important property that it is negatively charged over a wide pH range since its zero-point-of-charge (z.p.c.) is circa pH 2. 

A. M. Liu, K. Hidajat, S. Kawi, and D. Y. Zhao, A new class of hybrid mesoporous materials with functionalized organic monolayers for selective adsorption of heavy metal ions, Chem. Commun. 1145-1146 (2000). 

As elucidated from the adsorption experiment on BSA, adsorption of gallium ion by simple ion-exchange effect is negligible. The characteristics of metal ions such as ionic radius and hardness/softness, and the conformation of the metallothionein probably affect the selectivity of metal adsorption. The understanding of the mutual interactions among those factors would be a key dictor in designing the protein-based ligand suitable for a specific metal ion. 

In order to enhance or modify the chemical selectivity of an SERS substrate, it is possible to chemically derivatize the metal surface. For example, covalent bonding of a hydrocarbon to a silver island film should selectively adsorb nonpolar analytes from an aqueous solution. The general approach is shown schematically in Figure 13.24 for the case of metal ions detected by a surface-bound complexing agent (47). Field enhancement is provided by the substrate, while adsorption selectivity results from the chemistry of the derivatized... 

The values of PZC referred to as cip and pH" in Table 3.1 are obtained by acid-base titration. The experimental procedure is basically the same (although many variants have been described), and the substantial difference is in the method of selection of the zero point. Titration gives very accurate changes in uo from one pH value to another (or at least the part of due to proton adsorption/dissociation) without assumptions, but some assumptions are necessary to obtain the zero point. Existence of CIP does not prove the absence of specifically adsorbed ions. Lyklema [44] showed that in case of specific adsorption of metal cations the shift in the CIP to pH below the pristine PZC is more pronounced for metals having stronger affinity toward the surface (e.g. Pb > Ca) and the do at CIP is also more positive for more strongly bound cations. 

The goal in applying any SCM is to develop a self-consistent methodology for parameter estimation such that a set of standard parameters to describe surface acidity, site density, and the charge/potential relationships for different minerals can be developed and can be used in conjunction with spectroscopic data to guide the selection of appropriate adsorption reactions for the formation of metal ion surface complexes (i.e., inner vs. outer sphere, mono vs. hidentate, mononuclear vs. 

Metal hydroxides in general are anion-selective in acid solution and turn to be cation-selective beyond a certain pH, called the point of the iso-selectivity, pHpjS it is pHpjS = 10.3 for ferric oxide and pHpis = 5.8 for ferric-ferrous oxide [72]. Adsorption of multivalent ions may also control the ion selectivity of hydrous metal oxides because of its effect on the fixed charge in the oxides. For instance, hydrous ferric oxide, which is anion-selective in neutral sodium chloride solution, turns to be cation-selective by the adsorption of such ions as divalent sulfate ions, divalent molybdate ions, and trivalent phosphate ions [70,73]. It is worth emphasizing that such an ion-selectivity change due to the adsorption of multivalent ions frequently plays a decisive role in the corrosion of metals. 

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