Ferrous 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. 

The ferrous ions that dissolve from the anode combine with the hydroxide ions produced at the cathode to give an iron hydroxide precipitate. The active surface of ferrous hydroxide can absorb a number of organic compounds as well as heavy metals from the wastewater passing through the cell. The iron hydroxide and adsorbed substances are then removed by flocculation and filtration. The separation process was enhanced by the addition of a small quantity of an anionic polymer. 

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. 

Oxydul, n. (lower or-ous) oxide, (formerly) protoxide. -eisen, n. ferrous iron, -hydrat, n. hydrated -ous oxide (-ous hydroxide), oxydullsch, a. of lower valence, -ous, Oxydul-oxyd, n. an oxide in which the metal has a lower and a higher valence, oso-ic oxide, mixed oxide. -salz, n. lower or -ous salt. 

Tamura H, Goto K, Nagayama Y. 1976. The effect of ferric hydroxide on the oxygenation of ferrous iron in neutral solution. Corrosion Science 16 197-207. 

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. 

The older Bechamp method for iron oxide pigment production gives aniline as a co-product and is operated by Bayer in West Virginia. Nitrobenzene is reduced by reaction with iron filings in the presence of a hydrochloric acid catalyst. The iron is oxidized to the ferrous or ferric state, and the aniline-water mixture is separated from the iron-hydroxide sludge. The heavier aniline layer is removed and vacuum distilled to yield pure aniline. The yield is 90% to 95% of theoretical. The reactions are represented as follows138,255 ... 

Wet Tests.—The presence of iron in solution may readily be detected by a considerable number of sensitive reactions. Thus ferrous iron gives a green precipitate of ferrous hydroxide upon addition of excess of ammonium hydroxide. With potassium ferricyanide and a trace of acid, a deep blue precipitate—Turnbull s blue—is obtained. With potassium ferrocyanide a white precipitate is obtained in the entire absence of any ferric salt. Ferric iron, on the other hand, is usually characterised by its deep yellow or brown colour. Addition of concentrated hydrochloric acid deepens the colour. With excess of ammonium hydroxide, brown flocculent ferric hydroxide is precipitated. With potassium ferrocyanide solution, a deep blue colour is obtained in acid solution, whilst with potassium ferricyanide there is no action. Potassium thiocyanate gives in acid solution a deep red colour, which is not d troyed by heat. Salicylic acid gives a violet colour, provided no free mineral acid is present. 

A suite of both oxidized and reduced iron minerals has been found as efflorescences and precipitates in or near the acid mine water of Iron Mountain. The dominant minerals tend to be melan-terite (or one of its dehydration products), copiapite, jarosite and iron hydroxide. These minerals and their chemical formulae are listed in Table III from the most ferrous-rich at the top to the most ferric-rich at the bottom. These minerals were collected in air-tight containers and identified by X-ray diffractometry. It was also possible to check the mineral saturation indices (log Q(AP/K), where AP = activity product and K = solubility product constant)of the mine waters with the field occurrences of the same minerals. By continual checking of the saturation index (S.I.) with actual mineralogic occurrences, inaccuracies in chemical models such as WATEQ2 can be discovered, evaluated and corrected (19), provided that these occurrences can be assumed to be an approach towards equilibrium. 

Plaksenko suggested, in accordance with the theoretical ideas of Strakhov, that the primary sediments consisted of iron hydroxide which then was reduced to a ferrous form, producing the whole gamut of observed mineral associations in diagenesis under the influence of organic matter. 

Acid volcanic waters occur everywhere in recent volcanic areas, and surely they were just as common in the Precambrian. However, these waters contain mainly ferrous iron, not ferric. Mixing with oxygen-bearing surface waters leads to dilution, neutralization, oxidation of Fe ", and subsequent deposition of Fe in the form of hydroxide. 

Percent of Total Iron Contained in Wt. % of Ferrous Iron Oxy- Pyrltic Pyrite Jarosite Sulfate hydroxide Sulfur... 

In general, minerals in sedimentary and meta-morphic rocks contain ferrous iron (Velde, 1985) which is destined to become iron oxide under conditions of weathering. Oxidation under surface conditions has a tendency to produce iron in the ferric state. Most often the process takes iron out of the silicates and puts it into an oxide phase. In the uppermost layers of mature soils, iron oxide and various silicates, usually non-iron-bearing, are produced. In silicates containing iron, the majority is in the ferric state. The extent of the transformation of iron oxidation state is a rough measure of the maturity of the soil. In the extremely weathered soils one finds only ferric iron and aluminum oxides and hydroxides. These soils are typically red. 

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