Ferric iron hydroxides

Foulants enter a cooling system with makeup water, airborne contamination, process leaks, and corrosion. Most potential foulants enter with makeup water as particulate matter, such as clay, sdt, and iron oxides. Insoluble aluminum and iron hydroxides enter a system from makeup water pretreatment operations. Some well waters contain high levels of soluble ferrous iron that is later oxidized to ferric iron by dissolved oxygen in the recirculating cooling water. Because it is insoluble, the ferric iron precipitates. The steel corrosion process is also a source of ferrous iron and, consequendy, contributes to fouling. 

Metal depositors. Metal-depositing bacteria oxidize ferrous iron (Fe ) to ferric iron (Fe ). Ferric hydroxide is the result. Some bacteria oxidize manganese and other metals. Gallionella bacteria, in particular, have been associated with the accumulation of iron oxides in tubercles. In fact, up to 90% of the dry weight of the cell mass can be iron hydroxide. These bacteria appear filamentous. The oxide accumulates along very fine tails or excretion stalks generated by these organisms. 

High levels of chelant or oxygen affect the redox tendencies of iron-oxygen reactions and permit the liberation of Fe2+ ions (corrosion) from a metal surface and their subsequent chelation, thus preventing the formation or repair of blanketing ferric oxides, hydroxides, or a passivated magnetite film. 

As the first step in the coprecipitation process, ferric hydroxide precipitates either from the effect of the changing pH on the solubility of ferric iron,... 

When the post-coagulation sludge is added to hydrolyzate production, then the iron hydroxide is converted into ferric sulfate, which is well soluble in water. Too high content of soluble iron compounds, which are easily absorbable, should be avoided, as the excessive amount of the iron in the diet is harmful [13]. It leads to some disease like hemochromatosis or siderosis. Thus, the aim of our research was to find a method of decreasing the absorbable iron content of fish silage. 

Braterman and coworkers (1984) have demonstrated that this reaction occurs also at higher pH (up to neutral pH) where ferric iron is then precipitated as iron(III) hydroxide according to the following overall reaction ... 

Pharmacology Iron dextran, a hematinic agent, is a complex of ferric hydroxide and dextran for IM or IV use. The iron dextran complex is dissociated by the reticuloendothelial system, and the ferric iron is transported by transferrin and... 

In this case the ferric iron site seems to activate the substrate. Our generalization of this model is shown in Fig. 7. The iron binds the substrate and could serve, as a Lewis acid, to facilitate ketolization of either the bidentate or monodentate substrate. The hydroxide (water) ligand may be more significant than simply a placeholder ligand to be displaced by substrate. Since both substrate hydroxyls must lose their... 

It has long been recognized that ferric iron is a moderately strong acid. As early as 1896, Goodwin (5) concluded from conductometric measurements that simple dilution of ferric chloride solutions led to the formation of FeOH2+. The insolubility of ferric hydroxide has of course been appreciated even longer. The best current estimate of the solubility product constant for Fe OH)s at 25° (in 3 M NaC104) is (d). 

Bacteria which oxidize ferrous iron (Fe2+) to ferric iron (Fe3+) such as Gallionella and Leptothrix species are termed metal-depositing bacteria. The result of this metabolic process is the formation of ferric hydroxide. 

Colloidal saccharated iron is sometimes used in place of ferric hydroxide as an antidote in arsenical poisoning, but its adsorptive capacity depends on the alkalinity of the medium.4 Thus a commercial preparation containing 0-75 per cent, of sodium hydroxide was found to adsorb 12-57 per cent, of arsenious oxide (reckoned on the amount of iron present) addition of alkali increased the adsorption until, with 1-28 per cent, of sodium hydroxide present, there was a maximum adsorption of 27 per cent. The addition of acid correspondingly diminished the adsorption. A gel of ferric magnesium hydroxide, if prepared without boiling, also adsorbs arsenic from sodium arsenite solutions.5... 

The dissolution rate of goethite by sulfide was found to increase with surface area and proton concentration. Pyzik and Sommer (21) suggested that HS" is the reactive species that reduces surface ferric iron after exchanging versus OH . A subsequent protonation of surface ferrous hydroxide would lead to dissolution of a surface layer. Elemental sulfur was the prominent oxidation product polysulfides and thiosulfate were found to a lower extent. The dissolution rate R (in moles per square meter per second) of hematite by sulfide was demonstrated to be proportional to the surface concentration of the surface complexes >FeHS and >FeS (22). 

Typically limit to 0.5 ppm total Fe maximum in the cooling water. Above this level, phosphonate can be used to control problems initiated by iron. However, if the total Fe rises to 3.0 ppm, adsorption of the phosphonate onto the iron takes place and a loss of inhibitor function can occur. Iron salts present a serious fouling risk in cooling systems. Dissolved iron quickly oxidizes (especially where chlorine, bromine, or other oxidizing biocides are used) and forms ferric oxide/hydroxide, which acts as a flocculant,... 

Formation of Pyrite. Iron is carried to the peat swamp, before seawater transgression, as ferric oxide and hydroxides adsorbed on fluvial clays (123). During early diagenesis in a reducing environment, ferric iron is reduced to ferrous, which reacts with hydrogen sulfide to form iron monosulfide. If the basic mechanism of pyrite formation is similar to that in marine sediments... 

The mixture is loaded out of the reactor into tank 16 to distil tetraethyllead. The tank should already be filled with ground sulfure and ferric iron chloride. Iron chloride reduces the alkalinity of the dross and improves its consistency due to the formation of the colloid solution of iron hydroxide ground sulfure is uniformly distributed through the dross, also improving its consistency and preventing clotting of lead particles. 

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