Ferric colloids

These ferric colloids are less soluble at low temperatures, which tends to facilitate casse, especially in winter. For example, a wine may be aerated at 20°C without developing turbidity, while slight turbidity occurs at 15°C and serious ferric casse at 10°C. 

Stopping precipitation of the ferric colloid by adding gum arabic, which acts as a protective colloid. 

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]. 

At a pH of 8.5 or more, all the iron is in the ferric form, usually as a colloidal precipitate. If the iron level is very low, it tends to be ignored for most general purposes, but if the concentration rises to perhaps 0.3 ppm Fe or more, it causes discoloration upon precipitation and fouling and must be removed. 

Iron Dextran 5000- 7500 (complex with ferric chloride) Colloidal solution In 0.9% w/v sodium chloride injection Autoclave Deep IM non-deficiency anaemia (oral therapy ineffective or impractical) IV (slow infusion) non-deficiency anaemia (oral therapy ineffective or impractical)... 

Hsi C, Langmuir D (1985) Adsorphon of uranyl onto ferric oxyhydroxides applications of the surface complexation site-binding model. Geochim Cosmochim Acta 49 1931-1941 Ingri J, Widerlund A, Land M, Gustafsson O, Anderson P, Ohlander B (2000) Temporal variation in the fractionation of the rare earth elements in a boreal river the role of colloidal particles. Chem Geol 166 23-45... 

The fact that Prussian blue is indeed ferric ferrocyanide (Fe4in[Fen(CN)6]3) with iron(III) atom coordinated to nitrogen and iron(II) atom coordinated to carbon has been established by spectroscopic investigations [4], Prussian blue can be synthesized chemically by the mixing of ferric (ferrous) and hexacyanoferrate ions with different oxidation state of iron atoms either Fe3+ + [Fen(CN)6]4 or Fe2+ + [Fem(CN)6]3. After mixing, an immediate formation of the dark blue colloid is observed. However, the mixed solutions of ferric (ferrous) and hexacyanoferrate ions with the same oxidation state of iron atoms are apparently stable. 

Haywood and Riley [14] have described a spectrophotometric method for the determination of arsenic in seawater. Adsorption colloid flotation has been employed to separate phosphate and arsenate from seawater [15]. These two anions, in 500 ml filtered seawater, are brought to the surface in less than 5 min, by use of ferric hydroxide (added as 0.1 M FeC 2 ml) as collector, at pH 4, in the presence of sodium dodecyl sulfate [added as 0.05% ethanolic solution (4 ml)] and a stream of nitrogen (15 ml/minutes). The foam is then removed and phosphate and arsenate are determined spectrophotometrically [16]. Recoveries of arsenate and arsenite exceeding 90% were obtained by this procedure. 

Ferric hydroxide coprecipitation techniques are lengthy, two days being needed for a complete precipitation. To speed up this analysis, Tzeng and Zeitlin [595] studied the applicability of an intrinsically rapid technique, namely adsorption colloid flotation. This separation procedure uses a surfactant-collector-inert gas system, in which a charged surface-inactive species is adsorbed on a hydrophobic colloid collector of opposite charge. The colloid with the adsorbed species is floated to the surface with a suitable surfactant and inert gas, and the foam layer is removed manually for analysis by a methylene blue spectrometric procedure. The advantages of the method include a rapid separation, simple equipment, and excellent recoveries. Tzeng and Zeitlin [595] used the floation unit that was devised by Kim and Zeitlin [517]. 

Uranium coprecipitated with aluminium phosphate, precipitate dissolved in nitric acid Adsorption onto colloidal ferric hydroxide... 

To the filtered seawater (500 ml about 1.5 xg U) is added 0.05 M ferric chloride (3 ml), the pH is adjusted to 6.7 0.1 and the uranium present as (U02(C03)3)4- is adsorbed on the colloidal ferric hydroxide which is floated to the surface as a stable froth by the addition of 0.05% ethanolic sodium dodecyl sulfate (2 ml) with an air-flow (about 10 ml min-1) through the mixture for 5 min. The froth is removed and dissolved in 12 M hydrochloric acid-16 M nitric acid (4 1) and the uranium is salted out with a solution of calcium nitrate containing EDTA, and determined spectrophotometrically at 555 nm by a modification of a Rhodamine B method. The average recovery of uranium is 82% co-adsorbed WO4- and M0O4- do not interfere. 

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. 

On the other hand, the uptake of colloidal iron has been studied in greater detail. For example, some bacteria have been demonstrated to reduce ferric oxide particles to increase iron bioavailability [341,342], As was observed in Section 5.2.4, Fe reaction kinetics with metal carriers are thought to be rate-limiting. In the presence of colloidal iron, the thermodynamic stability or... 

Kuma, K. and Matsunaga, K. (1995). Availability of colloidal ferric oxides to coastal marine phytoplankton, Mar. Biol., 122, 1-11. 

Towe, K. M., and W. F. Bradley (1967), "Mineralogical Constitution of Colloidal Hydrous Ferric Oxides", J. Colloid Interface Sci. 24, 384-392. 

Yates, D. E., and T. W. Healy (1975), "Mechanism of Anion Adsorption at the Ferric and Chromic Oxide/ Water Interfaces", J. Colloid Interface Sci. 52, 222-228. 

Coagulants are used to bind together particulate and colloidal matter so they may be filtered from the feed before the membrane process. Coagulants can be either inorganic (such as ferric salts) or organic polyelectrolytes. The correct dosage and... 

C. (1997) The behavior of ferric oxide hydro-sols in the presence of urea. Progr. Colloid Polym. Sci. 105 38-40... 

Amhamdi, FI. Dumont, F. Buez-FIerman, C. (1997) Effect of urea on the stability of ferric oxide hydrosols. Colloids Surfaces 125 1-3 Amin, N. Arajs, S. (1987) Morin temperature of annealed submicronic a-Fe20j particles. Phys. Rev. B35 4810-4811 Amonette, J.E. Workman, D.J. Kennedy, D.W Fruchter, J.S. Gorby Y.A. (2000) Dechlorination of carbon tetrachloride by Fe(II) associated with goethite. Environ. Sci. Techn. 34 4606-4613... 

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