Iron -oxide.hydroxide FeOOH

A trivalent iron solution is placed into a bowl flask and heated up to 80 °C under refluxing conditions for a period of time of 2 hours. A precipitate is formed and separated from supernatant. Trivalent iron cation is hydrolyzed due to an increment of temperature promoting the hydrolysis and forming a trivalent iron oxide-hydroxide (FeOOH). After the 2 hours of hydrolysis reaction, a yellowish precipitate is obtained. 

The high pressure form of FeOOH is more compact than any other iron oxide hydroxide, hence it has a higher than usual Neel temperature of 470 K. At room temperature, high pressure FeOOH is antiferromagnetic with a collinear spin arrangement parallel to the c-axis (Fernet et al., 1973). High-pressure FeOOH is completely miscible with CrOOH. Substitution with Cr reduces T to the extent that with 80%... 

A common feature of the dehydroxylation of all iron oxide hydroxides is the initial development of microporosity due to the expulsion of water. This is followed, at higher temperatures, by the coalescence of these micropores to mesopores (see Chap. 5). Pore formation is accompanied by a rise in sample surface area. At temperatures higher than ca. 600 °C, the product sinters and the surface area drops considerably. During dehydroxylation, hydroxo-bonds are replaced by oxo-bonds and face sharing between octahedra (absent in the FeOOH structures see Chap. 2) develops and leads to a denser structure. As only one half of the interstices are filled with cations, some movement of Fe atoms during the transformation is required to achieve the two thirds occupancy found in hematite. 

The only peak at 254.5 °C observed in the as-received nanoparticles, as shown in Figure 12.5(b), is due to the decomposition of the iron oxide-hydroxide (goethite, FeOOH as proved by theFT-IR spectra) [31,76]. Similar to the TGA observation, a higher decomposition temperature (308.0 °C) was observed in PPy formed with the aid of nanoparticles than that of pure PPy formed without them (298.4 °C). Whereas only one peak was observed in the pure PPy samples, two exothermic peaks were observed in the DTA curves of the nanocomposites. These were due to the decomposition of PPy at 307 °C and the possible phase transition of iron oxide at 480 °C, as reported for the Fc203/PPy nanocomposites fabricated by the simultaneous gelation and polymerization (sol-gel) method [77,78] respectively. As compared with no obvious phase transition in the pure iron oxide nanoparticles, the observed phase transition was due to the intermediate product of PPy [77,78]. 

TABLE 2.1 Conversion Degree (%) in the Water-Gas Shift Reaction, RuCla-Impregnated Iron Oxide-Hydroxide Catalysts (a- and 8-FeOOH) 03 g of the Catalyst, Reaction Temperature 350 °C... 

Under the reaction conditions, divalent iron hydroxide and trivalent iron oxide-hydroxide species were likely to be formed. This being established, it is suggested that the following chemical reaction mechanism occurred trivalent iron cation hydrolyzes forming (FeOOH) as pH increases under alkaline conditions divalent iron cation forms Fe(OH)2. Both chemical species reacted to each other at pH values of around 10 to 11, forming magnetite according to equation 4 ... 

The purpose of the present work was, therefore, to elucidate which one of the numerous FeOOH or Fe2D3 phases could be used as the most appropriate material for the production of such a title catalyst which could exhibit high selectivity and/or satisfactory activity in the EB dehydrogenation to styrene. It seemed also interesting to check to what extent a possible contamination of the initial iron oxide hydroxides could affect activity or selectivity of the catalyst prepared from the contaminated initial iron compound. Sulphates or chlorides were... 

As pH rises, the metal content of drainage water tends to decrease. Some metals precipitate directly from solution to form oxide, hydroxide, and oxy-hydroxide phases. Iron and aluminum are notable is this regard. They initially form colloidal and suspended phases known as hydrous ferric oxide (hfo, FeOOH n O) and hydrous aluminum oxide (HAO, AlOOH nH.2O), both of which are highly soluble under acidic conditions but nearly insoluble at near-neutral pH. 

Diakonov, I. Khodakovsky I. Schott, J. Sergeeva, E. (1994) Thermodynamic properties of iron oxides and hydroxides. I. Surface and bulk thermodynamic properties of goethite (a-FeOOH) up to 500 K. Fur. J. Min. 6 967-983... 

Simple cations such as [Fe(H20)6]3"" undergo a certain amount of primary hydrolysis, depending upon the pH of the solution. The ion is in the hexaaqua form only at pH values lower than 2.0. Above that value the hydroxopentaaquairon(III) ion, [Fe(H20)50H]2 +, is predominant. Further increase in the pH of the solution causes more hydrolysis, until a complex solid material sometimes described erroneously as iron(lll) hydroxide is precipitated. The solid does not have the formula Fe(OH)3, but contains iron(III) oxohydroxide (FeOOH) and iron(III) oxide in various states of hydration, Fe203.xH20. 

Orange iron oxide with the lepidocrocite structure (y-FeOOH) is obtained if dilute solutions of the iron(II) salt are precipitated with sodium hydroxide solution or other alkalis until almost neutral. The suspension is then heated for a short period, rapidly cooled, and oxidized [3.22], [3.23],... 

Transparent yellow iron oxide is manufactured by precipitation of iron(ll) hydroxide or carbonate from a very dilute iron(ll) salt solution and subsequent oxidation, e.g. with air, to FeOOH. The quality is determined by parameters such as the concentration of the iron(ll) salt during precipitation, precipitation temperature, oxidation time. 

PZCs/IEPs of iron hydroxide oxide (nominally FeOOH) are presented in Tables 3.470 through 3.528. 

C3 Amphibole Oxidation and hydrolysis of iron Fe(II-III) + H2O + Oj FeOOH + H (Primary Fe-silicate) 4- H 4- H2O—> (Fe-oxide/hydroxide) 4- H" 4- H4Si04 Extremely slow incongruent dissolution... 

Oxidized root channels have been observed for few species, including rice (0. saliva), cattails, reeds, Spartina sp., Carex sp., and Potomogeton sp. (see review by Mendelssohn et al., 1995). The iron-em-iched plaques essentially consist of FeOOH minerals (Bacha and Hossner, 1977). Iron plaque may be amorphous or crystalline, in the forms of iron such as ferric hydroxides, goethite, lepidocrocite, and siderite. Iron oxides or hydroxides in rhizosphere have high affinity for metals and metalloids. 

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