Ferric hydroxide forms

Then 20 ml of 30 % hydrogen peroxide and 20 ml of 0.01 M ferric chloride are added into one litre of the neutralized solution. Hydrogen peroxide keeps plutonium in the tetravalent state in alkaline medium and ferric hydroxide formed carries actinides down. This coprecipitation gives decontamination factors of VLO both for Pu (IV) and Am (III). Figure 4 shows the flow-sheet for the procedure mentioned above. 

Figure 17.22 Crystal structure of the ferric hydroxide form of Hangman porphyrin 29 showing the water channel within the Hangman cleft. Figure adapted from Ref. [201].

Very finely divided minerals may be difficult to purify by flotation since the particles may a ere to larger, undesired minerals—or vice versa, the fines may be an impurity to be removed. The latter is the case with Ii02 (anatase) impurity in kaolin clay [87]. In carrier flotation, a coarser, separable mineral is added that will selectively pick up the fines [88,89]. The added mineral may be in the form of a floe (ferric hydroxide), and the process is called adsorbing colloid flotation [90]. The fines may be aggregated to reduce their loss, as in the addition of oil to agglomerate coal fines [91]. 

Prepare the neutral ferric chloride solution (i.e., free from hydrochloric acid) by adding dilute sodium hydroxide solution dropwise to the bench reagent until a slight precipitate of ferric hydroxide is formed. Filter off the precipitate and use the clear filtrate for the test. 

Iron compounds (qv) in limestone are seldom injurious to a lime product unless a very pure lime is required. Normally, the iron compounds are in the form of limonite [1317-63-1] (ferric hydroxide) and pyrite [1309-36-0] EeS2. Occasionally, hematite, magnetite, marcasite, and other forms of iron are found in limestone. 

The ferrous hydroxide may react to form ferric hydroxide ... 

Ferric ammonium citrate [1185-57-5]—A mixture of complex chelates prepared by the iateraction of ferric hydroxide with citric acid ia the presence of ammonia. The chelates occur ia brown and green forms, are dehquescent ia air, and are reducible by light. 

Outer crust. A friable outer crust forms atop the tubercle. The crust is composed of ferric hydroxide (hematite), carbonates, silicates, other precipitates, settled particulate, and detritus. Ferrous ion and ferrous hydroxide generated within the tubercle diffuse outward through fis-... 

Multiple magnetite shells may form by successive fracture. Ferrous species spew out of the fractured shell and are quickly oxidized to form a new ferric hydroxide crust. Beneath the new crust, another mag-... 

Ferric and ferrous hydroxide usually contain water of hydration. A layer of hydrated magnetite sometimes forms between the ferric and ferrous hydroxides (see Fig. 3.2). The threefold layer of corrosion products is usually called rust. The bulk of rust is the ferric hydroxide layer. (In tubercles, however, ferrous hydroxide often is the major component see Chap. 3.)... 

This is oxidised to ferric hydroxide Fe(OH)3, which is a simple form of rust. The final product is the familiar reddish brown rust Fe203 -H20, of which there are a number of varieties, the most common being the a form (goethite) and the 7 form (lepidocrocite). In situations where the supply of oxygen is restricted, Fe3 04 (magnetite) or 7 FejOj may be formed. 

However, in a steam-CR system where oxygen infiltrates, the corrosion reaction continues unabated and ferric hydroxide is formed. 

Copperas [green vitriol or ferrous sulfate (FeS04 7H20)] was also employed as an external coagulant (at pH values of approximately 7.7). It forms a turbid precipitate, and when oxygen is present (as is usual), a slimy precipitate of ferrous hydroxide also may form in addition to ferric hydroxide ... 

NOTE It is also apparent that the ferric ion (Fe3+) should chelate most readily. In practice, however, under strongly alkaline conditions, the preferred reaction is to instantaneously form ferrous hydroxide and then to slowly revert to ferric hydroxide (competing anion effect). 

The abiotic rate of the first oxidation reaction is slow the rate of the second reaction increases with increasing pH. The second iron oxidation reaction produces Fe(OH)3(s), ferric hydroxide. "Yellow boy," a limonitic precipitate, is produced when the ferric hydroxide mixes with ferric sulfates when formed, "Yellow boy" gives receiving waters an unappealing yellow tint. 

Addition of sufficient base to give a > 3 to a ferric solution immediately leads to precipitation of a poorly ordered, amorphous, red-brown ferric hydroxide precipitate. This synthetic precipitate resembles the mineral ferrihydrite, and also shows some similarity to the iron oxyhydroxide core of ferritin (see Chapter 6). Ferrihydrite can be considered as the least stable but most reactive form of iron(III), the group name for amorphous phases with large specific surface areas (>340 m2 /g). We will discuss the transformation of ferrihydrite into other more-crystalline products such as goethite and haematite shortly, but we begin with some remarks concerning the biological distribution and structure of ferrihydrite (Jambor and Dutrizac, 1998). 

The precipitant most commonly used for the collection of organics has been what is loosely called ferric hydroxide . It is formed by the in situ formation... 

Fig. 31.5. Minerals formed during reaction at 25 °C of a hypothetical acid drainage water with calcite (top), and fractions of the amounts of arsenite, arsenate, copper, lead, and zinc present initially in solution that sorb onto ferric hydroxide over the course of the reaction path (bottom). Bottom figure is plotted against pH, which increases as the water reacts with calcite.

The average adult body contains approximately 4 g of iron, of which roughly two-thirds exists in the form of hemoglobin. Treatment of certain types of anemias usually consists of dietary supplementation or the administration of therapeutic iron preparations by oral and parenteral routes. Iron is often administered by i.m. as iron-dextran complex which is ferric hydroxide and dextran containing 50 mg of iron per milliliter. 

---