Coagulation of iron oxide particles in the

Liang, L. and Morgan, J.J. (1990b) Coagulation of iron oxide particles in the presence of organic materials. Application of surface chemical model. In Chemical Modeling of Aqueous Systems II (eds Melchior, D.C. and Bassett, R.L.). American Chemical Society, Washington, DC, pp. 293-308. 

Coagulation of Iron Oxide Particles in the Presence of Organic Materials... 

Liang, L. (1988) Effects of surface chemistry on the kinetics of coagulation of submicron iron oxide particles (a-Fe203) in water. Ph.D. Thesis Caltech. USA... 

Fig. 6.9. Log-log plot of W, for hematite (a-Fe203) colloids at pH 3.44, versus o-phosphate concentration. The arrow indicates the point of zero charge, defined operationally as the concentration of o-phosphate at which W p = 1.0 (data from L. Liang, Effects of surface chemistry on kinetics of coagulation of submicron iron oxide particles (ar-F Oj) in water, Ph.D. dissertation, California Institute of Technology, Pasadena, CA, 1988. Environmental Quality Laboratory Report No. AC-5-88).

Reactions of Colloidal Iron Oxide. — Colloidal iron oxides obtained from the acetate are turbid in reflected light and clear in transmitted. Sulfuric acid or its salts coagulate the hydrosol immediately, and the precipitate is not soluble in concentrated acid in contradistinction to the precipitate from Graham s solutions. When the hydrosol is poured into concentrated acid a precipitate is formed that is again dissolved by water. There exist several analogies between the hydrosol of meta-stannic acid and those of these ferric acetate hydrosols this accounts for the name, inetairon oxide. The hydrosol deserves more elaborate investigation the apparent isomerism of the two modifications is probably due to the difference in the size of the particles. 

If uniform mixing of the fission product vapors and volatilized materials results, the recondensed particles might be expected to have a constant specific activity of elements having similar boiling points. Note parenthetically that studies of fission-product incorporation into the metal and oxide products of vaporized iron wires (in which iron-metal spheres and iron-oxide irregulars are formed) indicate no simple relationship between specific activity and size. For example, a refractory element like zirconium is found most enriched in particles of intermediate size. This is probably in part caused by a concentration effect—i.e.y in these experiments the zirconium represented a mole fraction of about 10"9. As indicated earlier, the fission products are a minor constituent in the fireball, and a very complex pattern of incorporation can be anticipated, especially if coagulation with melted but unvaporized particles ensues. 

The peptization capabilities of polyphosphates depend on their sorption on aluminosilicates and colloidal particles of hydrated oxides of iron, aluminium and manganese. In practice, this causes problems in water treatment by coagulation when already rather low concentrations of polyphosphates can cause improper agglomeration of colloidal particles into sedimentable floccules. 

A. UltrafiUration. — By the use of filters that allow electrolytes to pass freely through, but retain the colloidal particles, colloidal stannic acid must have, after filtration, not only its ultramicrons, with their attendant anions, but also an equivalent amount of alkali ion molecules. The excess of the electrolytes, KOH, KaSnOa, etc., that were dissolved in the disperse medium, have passed through. The adsorbed portion of the alkali, regardless of whether it is dissociated or not, is an essential part of the hydrosol for if it is removed the colloid will coagulate. Duclaux, who has studied the behavior of colloidal iron oxide and cupric ferrocyanide in this connection, has proposed the name Micells for the ultramicrons together with their adsorbed molecules... 

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