Multivalent metal cations

Hydroperoxides are decomposed readily by multivalent metal ions, ie, Cu, Co, Fe, V, Mn, Sn, Pb, etc, by an oxidation-reduction or electron-transfer process. Depending on the metal and its valence state, metallic cations either donate or accept electrons when reacting with hydroperoxides (45). Either one... 

Silica Polymei Metal Ion Interactions in Solution. The reaction of metal ions with polymeric sihcate species in solution may be viewed as an ion-exchange process. Consequently, it might be expected that sihcate species acting as ligands would exhibit a range of reactivities toward cations in solution (59). Sihca gel forms complexes with multivalent metal ions in a manner that indicates a correlation between the ligand properties of the surface Si-OH groups and metal ion hydrolysis (60,61). For Cu +, Fe +, Cd +, and Pb +,... 

Self-assembly of aromatic dendron subunits has been tried by the design of coordination to multivalent metal cations (i.e., metal-cored dendrimer complexes). Several metal-cored dendrimer complexes have successfully exhibited luminescence by antenna effects. 

Metal-complex formation entails the interaction of one or more organic ligands with a multivalent metal cation. This brings about certain fundamental changes in the characteristics of the components of the complex. 

Furthermore, in the manufacture of zeolite catalysts, ion exchange plays an outstanding role. Bronsted acid sites can be readily generated by introducing ammonium ions followed by a heat treatment or by introducing multivalent metal cations, again followed by heat treatment (Weitkamp, 2000). However, not all these applications incorporate the ion exchange and catalysis phenomena at the same time, i.e. simultaneous action of these two mechanisms. 

This oxide has a layered structure consisting of [Nb60i7]4 macropolyanion sheets interleaved by K+ ions, as shown in Fig. 16.3. The K+ ions can be replaced by various mono- and multivalent metal cations,22,37,38 protons6,12,38,395 and organic cations.405 An important aspect of the structure is the presence of two. types of interlayer regions,5,95 referred to as interlayer I ana interlayei II, with differing interlayer reactivity.375 This makes the [Nb60i7]4 sheets nonsymmetric with respect to mirror reflection about the sheet planes. Besides the anhydrous compound of the above formula, it also forms two hydrates, one with about three... 

In terms of published practical applications, MEUF has been successfully employed to remove multivalent metal cations (such as Cu +) from wastewater (456), for removal of n-alcohols (457) as well as other organic substances (benzene, etc.) (454.455) from aqueous streams. The general procedure seems to offer an attractive means for purification of water streams containing organic substances or heavy metals. MEUF may prove to be useful in industrial applications as well (455). 

More recently, a spirobenzopyran dimer bridged by a diaza-18-crown-6 moiety through the 8-position (67) was developed by Kimura and co-workers.119 121 Crowned bis(spirobenzopyran) 67 shows a similar coloration selectivity to that of 63. Complexation of multivalent metals, especially Ca2+ and La3, by 67 enhanced the isomerization of the spirobenzopyran moiety to the corresponding merocyanine form due to an effective intramolecular interaction between a crown-complexed cation and the two phenolate anions in the cation complexes of the merocyanine form. 

The solubility and mobilization of multivalent cations of metals such as Fe, Mn and Ti is related to their valence states and, thus, to the Eh of aque-... 

Weak-acid ion exchange resins adsorb hydrogen ions most strongly. A slight excess of hydrogen ions in the solution can displace all other cations from the resin. Weak-acid resins are particularly selective for multivalent metal ions. 

Multivalent metals can be separated from the alkali metals by solvent extraction or precipitation methods. Cation exchangers and electrolysis with a mercury cathode are useful in separating the metals of other groups from the alkali metals. 

The reactions occurring for multivalent metal cations occur over many condensation steps and may not obey the kinetic rules outlined above. Silicate polymerization is known to depend on the presence of oligomeric ion species. - - Gibbsite (formally Al(OH)3) is known not to precipitate sufficiently rapidly from supersaturated solutions, but needs seeding for particle growth Moreover, depending on the temperature and the composition of the solution, different solid species may form. This is illustrated in Figure 8.21. ... 

Therefore, melts-solvents of the first kind are of interest in the following scientific aspects determination of the acid-base product of the ionic solvent and estimation of the upper limit of acidity of these solvents (such as nitrates, sulfates). The decrease of stability of the solvent acid can be used for the stepwise decomposition of acidic solutions of cations and synthesis of complex oxide compounds and composites by coprecipitation [53-56], It is possible to obtain complex oxides containing alkali metals by precipitation of multivalent metal oxides with the alkali metal oxide as a strong Lux base, as was reported by Hong et al., who used 0.59LiNO3-0.41LiOH mixed melt to obtain electrochemically active lithium cobaltate, LiCo02 [57]. 

That is, in the Sr2+-based chloride melt the slope of this dependence is close to that for the KCl-NaCl equimolar mixture (0.053), and this confirms again our assumption that the interactions of multivalent metal cation-chloride ion are subject to small changes upon change in the cation composition of the melt. 

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