Soluble peroxide complexes

Sodium hydroxide quantitatively precipitates traces of Mn as Mn02aq., with Fe(lII), La, or Mg as carrier. Manganese can also be separated as Mn02aq. by treatment with excess of ammonia in the presence of H2O2. This method enables one to separate manganese from Ti, V, and other metals which form soluble peroxide complexes. 

Nitrilotriacetic acid (NTA) is a constituent of various domestic and hospital detergents and is a common water contaminant. NTA forms water-soluble chelate complexes with various metal ions, including iron, at neutral pH. Its iron complex, Fe-NTA, is a known potent nephrotoxic agent. The renal toxicity is assumed to be caused by the elevation of serum free-iron concentration following the reduction of Fe-NTA at the luminal side of the proximal tubule, which generates reactive oxygen species and leads to enhancement of lipid peroxidation. 

However, the relatively high enzyme costs form an obstacle to commercialization. Inefficient laccase use is a result of its instability towards the oxidizing reaction conditions. We have recently shown that the stability of the laccase under reaction conditions can be improved by immobilization as a cross-linked enzyme aggregate (see Chapter 9). It has also been shown that a water-soluble iron complex of a sulfonated phthalocyanine ligand is an extremely effective catalyst for starch oxidation with hydrogen peroxide in an aqueous medium [11]. 

In this section, the method of synthesizing water-soluble titanium complexes using hydroxycarboxylic acid and the nature of the complexes are described. Metallic titanium powder reacts with hydrogen peroxide in the presence of ammonia as described in Equation 5.1, yielding a yellowish solution with dissolution of titanium powder in hydrogen peroxide ... 

Niobium (Nb, at. mass 92.91) hydrolyses (in the absence of complexing anions) over the pH range 0-14. Polymerized forms of Nb(V) give pseudo-solutions or they separate as a white precipitate. When fused with NaOH, Nb20s forms the niobate, which is soluble in NaOH solutions. Niobium(V) forms stable fluoride, tartrate, oxalate, and peroxide complexes. The niobium complexes are more stable than the corresponding Ta complexes. A niobium chloride complex is formed in >5 M HCl solutions. Niobium(V) can be reduced to coloured species of Nb(III) and Nb(IV). In an acid medium, zinc metal reduces Nb(V), but not Ta(V). 

Vx-MFI and Vx-p Differently from the above catalysts, in V-MFI (ZSM-5 structure) and V-P (Beta structure) the zeolite was prepared first and then the vanadium component was added by incipient wet impregnation at r.t. using a peroxide complex of vanadium obtained by reaction at r.t. of V2O5 with H2O2. The use of the V-peroxide complex increases the solubility of the vanadium complex, avoiding the possible precipitation at contact with the zeolite crystals and thus avoiding deposition on the outer surface. 

Thus, it is clear why water cannot be used as a solvent Most titanium esters or halides are too reactive and would react with the water solvent rather than the silica surface. One procedure that permits titanation from an aqueous solution is to use a water-soluble titanium complex that resists hydrolysis until after silica dehydration temperatures are reached, when only silanol groups remain. Titanate complexes of triethanolamine [569], acetylacetonate [570], lactate [569], or even peroxide [571] can be used in this way to perform aqueous titanation. 

Ruthenium tetroxide was shown to oxidize PCBs in water [20], Water-soluble ruthenium complexes, such as [Ru(H20)2(DMS0)4]2+, are effective catalysts for the KHSO5 deep oxidation of a number of chloroaliphatics, of a-chlorinated al-kenes, polychlorobenzenes, and polychlorophenols. When the reactions are carried out in water in the presence of surfactant agents, degradation of the substrates is definitely faster. Aromatic substrates are mainly converted into HC1 and C02, polychlorophenols being more sensitive to oxidation than substituted benzenes [21]. Replacement of the DMSO- solvated ruthenium by RuPcS results in a definite improvement of the reaction course with hydrogen peroxide, since dismutation of... 

The process suffers from several drawbacks. For instance, the solvent must be able to dissolve both the apolar anthraquinone and the more polar hydroquinone and, at the same time, to provide immiscibility with water in order to allow the recovery of hydrogen peroxide. Complex mixtures of solvents are used, usually formed by an aromatic compound to dissolve the anthraquinone (toluene, methylnaphthalene) and a polar solvent to dissolve the hydroquinone (organic esters of phosphoric acid, diisobutylcarbinol, etc.). Even so, some derivatives of the quinone formed under the reaction conditions, particularly tetra- and octa-hydro derivatives are poorly soluble in the working solution. 

It is well known that peroxide ions form stable and water soluble titanium complexes under acidic conditions (Cotton et al., 1999). The conplexes are colored in orange to red. 

Wet-Chemical Determinations. Both water-soluble and prepared insoluble samples must be treated to ensure that all the chromium is present as Cr(VI). For water-soluble Cr(III) compounds, the oxidation is easily accompHshed using dilute sodium hydroxide, dilute hydrogen peroxide, and heat. Any excess peroxide can be destroyed by adding a catalyst and boiling the alkaline solution for a short time (101). Appropriate ahquot portions of the samples are acidified and chromium is found by titration either using a standard ferrous solution or a standard thiosulfate solution after addition of potassium iodide to generate an iodine equivalent. The ferrous endpoint is found either potentiometricaHy or by visual indicators, such as ferroin, a complex of iron(II) and o-phenanthroline, and the thiosulfate endpoint is ascertained using starch as an indicator. 

Nickel plating solutions may contain excess iron and unknown organic contaminants. Iron is removed by peroxide oxidation, precipitation at a pH of about 5, then filtered out. The more complex, less water-soluble organic contaminants along with some trace metals are removed with activated carbon treatments in separate treatment tanks. About 5 g/L of plating-grade activated carbon is mixed in the plating solution for at least 1—2 hours, usually at warmer temperatures. 

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