Effect of the Transition Metal Ions

4 Effect of the Transition Metal Ions - Hexaaluminate materials, 1 19, including transition metal ions in the structure (M = Mn, Fe, Cr, Co, Ni) were prepared both via the alkoxide15 and the coprecipitation route.23,24,25 For all the compositions investigated, monophasic samples with layered-alumina structure and surface area in the range 10-15 m2/g were obtained upon calcination at 1300 °C. 

Groppi and co-workers23,24 investigated the thermal evolution of Mn- and Fe-substituted hexaaluminates with different amounts of transition metal ions prepared via the co-precipation route. The dried precursors of BaMnxAl 2.xOJ9 

Also in Fe-containing materials, promoting effect on the formation of the final layered-alumina phase was observed.24 In the completely substituted material BaFe120i9 a monophasic sample with magnetoplumbite structure was obtained at 700 °C. This low formation temperature was related to the greater mobility of oxygen and Ba ions in the lattice of Fe oxides than in A1 oxides. Indeed, the transition from y-+a alumina occurs in Fe oxides at temperatures hundreds of degrees lower than those required for phase transitions in A1 oxides. 

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The kinetic analysis indicates (35) that polymerization of transition metal acrylates proceeds by the same elementary prxx esses as that of their metal-free" analogs. HOft/ever, in many cases the polymerization may be complicated by an individual effect of the. transition metal ion. In particular, the kinetic scheme for the Ti (4+)-containing MCM (36) can be described by the follov/ing system of equations (see Fig. 4) ... 

The oxidation rates of XOH were measured for the PVP complexes of the transition metal ions of the 4th series, i.e., Cr, Mn, Fe, Co, Ni, Cu and Zn ion. As can be seen in Fig. 2 (a), the Cu complexes exhibit the highest activity and the activity of the PVP-Cu catalyst is higher than that of the monomeric pyridine-Cu catalyst. To this Cu complex, equivalent amount of the second metal component was added i.e., the PVP-Cu, secondary metal ion mixed complexes were prepared. The activities of these mixed complexes are summarized in Fig. 2 (b). One notices that Mn ion increases the catalytic activity of the Cu ion although Cr and Fe ion inhibit the catalytic activity. Another important result in Fig. 2 (b) is that the effect of secondary metal ion is more clearly observed in the PVP system, comparing to the monomeric pyridine catalysts. 

This preparation method was successfully extended to the production of other hexaaluminates containing alkaline (K), alkaline-earth (Ca, Sr), and rare earth (La, Pr, Sm, Nd) metals in the mirror plane.15,16 This route was also effectively used to prepare hexaaluminates incorporating transition metal ions in the structure (with M = Cr, Mn, Fe, Co, Ni, and Cu). In this case, nitrates of the transition metal ions were dissolved in the amount of water required for the hydrolysis.5... 

The effects of other transition metal ions are qualitatively similar, although their extent is decidedly smaller. Complexes of copper, chromium, and manganese with central atoms in their higher oxidation states are fairly good candidates to play the role of an environmental photocatalyst [20],... 

In the present chapter we focus on the optical spectra of the transitional metal ion impurities, as the point defects in insulating crystals. The reasons are because the JT effect is most often encountered in the transitional metal complexes, and very common in the octahedral complexes. We shall make use of the configuration coordinate approach [12], which enables one to apply much of the theory developed for molecules to the case of an isolated impurity in a crystal. 

As we have demonstrated in the present work, a combination of the DV-LFT calculations and the DV-ME calculations is a quite effective tool for quantitative analysis of various effects such as charge transfer, covalency and electron correlation on the multiplet structure of the transition metal ions in crystals. 

Compodtion of Waste Stream. The filtrate from the Mn precipitation is the waste stream resulting from this process. It has a pH of 9 and solid content of 17 g/1 of Na2S04. Its impurity content is given in Table XI, which lists the 10 highest contaminants. The concentrations are given in ppm no other impurity was detected at a level greater than 50 ppb. The impurity content of this waste stream is quite low and, if not directly disposable, compatible with standard waste water treatment procedures. The low concentration of the transition metal ions, particularly Fe and Mn, which were major constituents of the feed stream attests to the effectiveness of the separation and recovery processes. 

In order to evaluate the effects of other transition metal ions on the removal of Cu, solutions containing both Cu and Ni were treated with the Dowex XFS 4195.02 resin. Data from these experiments are shown graphically in Figure 6. The removal of Cu" from aqueous solutions is slightly retarded by the presence of Ni". ... 

Thus it seems that more than a passing reference is appropriate as to the relation of L-quantum number and the tetrad effect, and indeed Sin ha (58) has recently shown that the L-values exhibit the same periodicity as the tetrad effect in the lanthanide (actinide) series (Fig. 6), as well as that the properties of the/-transition metal ions vary linearly within each tetrad (58). It is a great pity that Klemm did not divide the lanthanide series based on the repeatation of the total angular momentum (L-values) values (see the above table), rather he showed and supported the classification of Endres (48). 

Kinetic Stability. Due to the stabilizing effect of the macrocycle, the SOD mimics have high kinetic stability (discussed below) and, for example, are stable in the presence of the transition metal ion chelators, such as EDTA. However, the apoenzyme form of the Cu,Zn SOD enzyme can readily be prepared by dialyzing the enzyme with EDTA. ... 

Describe the periodic trends in radii and oxidation states of the transition-metal ions, including the origin and effect of the lanthanide contraction. (Section 23.1)... 

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