Hydroxyl complexing

Figure 2. Solubility of maninite as a function of pH at 25°C for different fluoride concentrations. Formation of uranous fluoride complexes greatly enhances maninite solubility below pH 3-4. The increase of maninite solubility at higher pH results from the formation of uranous hydroxyl complexes. [Used with permission of Elsevier Science, fromLangmuir (1978) Geochim Cosmochim Acta, Vol. 42, Fig. 4, p. 555].

Figure 9. Simplified model of the (111) surface of the corundum-type structure, (a) A view of the surface from a direction slightly shifted from <111>. Only metal ions of the zeroth, first, and second layers are shown, (b) A section of the surface along the arrows depicted in part a. Hexagonally close-packed oxide ion layers are shown with lines. Surface protons are not shown, (c) A divalent Co-57 or pentavalent Sb-119 ion on the zeroth metal ion layer, (d) Aquo or hydroxyl complex of divalent Co-57 or pentavalent Sb-119 hydrogen-bonded to the surface oxide ion layers of hematite.

Metallic Salts Complex in Solution Corresponding Hydroxyl Complex a(Pd) 5(H20) a (OH)... 

The influence of concentration of KOH and separator materials on the soluble cadmium compounds, for example, cadmium hydroxyl complexes formed near the Cd electrode during the anodic process was also studied [321, 322]. 

The [A1(OH)3(s)] is omitted, as usual, because it is a solid. Because the solids are part of the equilibrium, the instability constants of these hydroxyl complex ions can be applied only to solutions that are saturated with respect to the solid. 

Predicting IEP(s). To correlate and predict IEP(s) on the basis of solid composition, a useful simplification can be made by taking advantage of the close analogy between dissociation reactions of surface hydroxide groups and of mononuclear hydroxyl complexes. For example,... 

We have no direct evidence for this type of behavior. However, it appears reasonable to expect that hydroxyl oxygens would compete with ether oxygens for coordination. Thus, displacement of the hydroxyl complexes, Equation 6, might be rate controlling. 

Sorption/precipitation of plutonium is greatly affected by the presence of hydrazine. Since hydrazine increases sorption, it appears that at least some of the plutonium is present initially as plutonium(V) or plutonium(VI) and is reduced to plutonium(IV) by hydrazine. According to standard half-cell potentials, both plutonium(VI) and plutonium(V) should be reduced to plutonium(IV) or plutonium(HI) under the conditions of the experiments, assuming that the hydroxyl complexes are important at the pHs of the experiments. 

Hydration of HPP. All factors mentioned above affect the T i value, showing the change in the state of water to be the result of a change in the composition of the water and the surface properties of the disperse phase. Aluminium hydrolysis products are mostly particles of Al(OH)3 with aluminium hydroxyl complexes adsorbed on them, so the change in T can be associated with an altered nature and number of hydrophilic centres. It has been shown5,6 that in all cases the spin-spin relaxation time of water protons decreases with increasing OH/A1 ratio in the coagulant molecule. This is an evidence of increased hydration of particles surface in this direction. 

Olefin 6, aldehyde or ketone 8, acrylic acid 17 and ketene 18 can be found among the possible products generated unfinished states 15 and 19 did not seem to be promising. Complex 14 and 1,4-metalla diradical 4 formed from it by decarboxylation is an important intermediate. The ways terminating at olefin contain path 4-5-6 starting with decarboxylation and path 2-12-13-6, where the decarboxylation follows after the homolysis of the C —O bond of the original hydroxyl. Complex 14 can homolyse into 4 or 16, in both cases diradicals produce... 

Ru(bpy) 3 -zeolite Y used as the starting material for generation of Ru(III). Upon oxidation by CI2, spectrum a is obtained with bands at 420 and 660 nm, typical of Ru(bpy)3 +. With time, the band of Ru(bpy)3 at 450 nm recovers. The intensity around 850 nm initially increases and then decreases. Bands in this region are typical of the hydroxylated complexes formed by water attack on the bpy ligands of Ru(bpy)3 +. The overall mechanism for reaction of water with Ru(bpy)3 + was proposed to be as follows ... 

M(OH)J = sum of concentrations of all hydroxyl complexes including hydrolyzed species and anionic complexes of amphoteric metals ... 

Case 1. Lower chelates in aqueous phase (hydroxyl complexes, masking effects, and adducts negligible) Particularly with multivalent metals, an appreciable fraction of the metal ion in the aqueous phase may exist as lower complexes. Thus Rydberg, in studying the extraction of thorium acetylacetonate from water... 

When a relatively large excess of hydroxyl ion is present and the metal is amphoteric, relatively simple anionic species (hydroxyl complexes) usually are formed. If the solution is sufficiently alkaline (pH > + log Kj, ), the reagent... 

In this section we will study examples of several distribution plots that offer a convenient and powerful way to examine changes in the speciation of complex-forming metal cations with pH. Such plots are particularly useful when studying the complexation of multivalent hard cations, such as the actinides that tend to form important hydroxyl complexes. Other ligands must displace OH in order to complex the cation. They have difficulty in so doing except in acid waters where competition with OH is minimal. 

Given below are cumulative formation constants for the ferric-hydroxyl complexes at zero ionic strength and 25 C from Macalady et al. (1990). 

The tendency of cations to be adsorbed by oxide and hydroxide minerals with increasing pH, is usually proportional to their tendency to form hydroxyl complexes in solution. Explain this statement. How would this general rule help you to decide under what different pH conditions equal concentrations of Cr +, Ca % and Na would tend to be adsorbed by the same solid ... 

In our discussion of aqueous species of iron, it is appropriate to first consider the Fe(II) and Fe(III) hydroxyl complexes (Table 12.1). To judge their importance, we will construct plots to show the fractional distribution of these complexes as a function of pH. The computational approach is as presented in Chap. 3. Solute activity coefficients are ignored. 

Above about pH 5, U(VI) generally occurs as aquocomplexes in natural waters. The relative importances of the U(VI) hydroxyl complexes are shown in Fig. 13.3 for a typical groundwater U con-... 

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