Iron hydroxide colloid

Van der Woude, J.H.A. De Bruyn, P.L. (1983) Formation of colloidal dispersions from supersaturated iron(III) nitrate solutions. I. Precipitation of amorphous iron hydroxide. Colloids Surfaces 8 55-78... 

Kovatchva, V.K. and Parlapanski, M.D. (1999). Sono-electrocoagulation of iron hydroxides. Colloids Surf. A 149, 603-608. 

Clays and particles of soil organic matter have negative charges and high CECs, as confirmed by the following values 150-500 meq/100 g for organic matter and 3-150 meq/100 g for clay minerals (as kaolinite and smectite). On the other hand, aluminum and iron hydroxide colloids tend to be hydrophobic, with surface positive charges, and, consequently, they are predominantly anion adsorbers. 

Structure of colloids of iron hydroxide. Colloidal solutions of iron hydroxide usually are obtained experimentally by hydrolysis of a ferric chloride solution. The particles that are formed consist of molecules of Fe(OH)3, which constitute the insoluble nucleus—the main mass of the micelle. The number of molecules in the nucleus is not constant and may range from tens to 500. 

Carbon dioxide has no essential effect on the stability of iron hydroxide colloids toward the action of electrolytes. The coagulation thresholds (concentrations of MgS04) prove to be the same for colloidal solutions of iron saturated with carbon dioxide (- co, bar) as for solutions in the air. 

We know that manganese nodules near the continent have a lower manganese and higher iron content than deep-sea manganese nodules. Iron hydroxide colloids coagulate, as already described, earlier than those of man nese hydroxides. Therefore the first precipitation from the river impact near the continental border should Iw enriched in iron, and the precipitates more distant from the continental border should have lower iron and higher manganese contents. 

Late transition metal or 3d-transition metal irons, such as cobalt, nickel, and copper, are important for catalysis, magnetism, and optics. Reduction of 3d-transition metal ions to zero-valent metals is quite difficult because of their lower redox potentials than those of noble metal ions. A production of bimetallic nanoparticles between 3d-transi-tion metal and noble metal, however, is not so difficult. In 1993, we successfully established a new preparation method of PVP-protected CuPd bimetallic nanoparticles [71-73]. In this method, bimetallic hydroxide colloid forms in the first step by adjusting the pH value with a sodium hydroxide solution before the reduction process, which is designed to overcome the problems caused by the difference in redox potentials. Then, the bimetallic species... 

Under relevant conditions (neutral pH, presence of carbonate) the concentrations of dissolved trace metals are limited by the solubility of their solid hydroxides or carbonates. A prominent example is the solubility of Fe(III), which is very low (around 10 10 mol dm 3) under relevant conditions of fresh water or seawater at neutral pH [96]. Iron(III) occurs primarily as solid or colloidal iron hydroxide at neutral pH. 

Pour 2 ml of the prepared colloidal iron hydroxide solution into each of several test tubes and add 2 ml of one of the following solutions of the same normality (0.1 N) to each of them sodium chloride, barium chloride, aluminium chloride, sodium sulphate, aluminium sulphate, or monosubstituted sodium orthophosphate. What do you observe How does the coagulating effect of an electrolyte depend on the sign and magnitude of the charge of its ions ... 

EDR is typically used for demineralization of brackish water, which often contains poorly soluble minerals such as calcium bicarbonate and calcium sulfate, as well as colloids such as humic and fulvic acids and iron hydroxides The periodic reversal of the direction of the electric current avoids scaling and fouling of the membranes by such substances. 

Hlavay, J. and Polyak, K. (2005) Determination of surface properties of iron hydroxide-coated alumina adsorbent prepared for removal of arsenic from drinking water. Journal of Colloid and Interface Science, 284(1), 71-77. 

Silt is formed by suspended particulates of all types that accumulate on the membrane surface. Typical sources of silt are organic colloids, iron corrosion products, precipitated iron hydroxide, algae, and fine particulate matter. A good predictor of the likelihood of a particular feed water to produce fouling by silt is the silt density index (SDI) of the feed water. The SDI, an empirical measurement (ASTM Standard D-4189-82,1987), is the time required to filter a fixed volume of... 

The mixture is loaded out of the reactor into tank 16 to distil tetraethyllead. The tank should already be filled with ground sulfure and ferric iron chloride. Iron chloride reduces the alkalinity of the dross and improves its consistency due to the formation of the colloid solution of iron hydroxide ground sulfure is uniformly distributed through the dross, also improving its consistency and preventing clotting of lead particles. 

Silicon, aluminum, and iron(III) that form oxide, hydroxide, colloids. The proportion of their aqua complexes is extremely low, and they transform to crystalline aluminosilicates. 

Obtaining colloids of iron hydroxide. Stable colloidal solutions of iron are obtained only under certain conditions, a slight change in which leads to coagulation. Thus, when a ferric chloride solution is neutralized by an alkali according to the reaction ... 

In laboratory conditions hydrolysis usually is carried out as follows a solution of FeClj is added drop by drop to distilled water heated to boiling, stirring constantly. The whole liquid quickly takes on the red-brown color characteristic of hydrous ferric oxide, but remains transparent. If the solution is allowed to cool, the color fades somewhat, as some of the Fe(OH)3 changes back into FeCl3. To prevent the reverse reaction, the solution is boiled for a few minutes to remove HCl with water vapor, or it is removed by dialysis. In this way one obtains stable colloidal solutions of iron hydroxide containing from 5 to 5000 mg/1 of iron. 

At room temperature colloidal solutions of iron hydroxide can be obtained only by way of prolonged dialysis (Glazman et al., 1958). And finally, experiments are known in which sols were obtained by peptization, by treating freshly precipitated, washed Fe(OH)3 sediment with ferric chloride while heating. A dilute solution with a certain amount of HCl acts on freshly precipitated Fe(OH)3 as ferric chloride does. The sols of Fe(OH)3 obtained by peptization are no different in structure from the sols obtained by hydrolysis. 

Stability of colloids of iron hydroxide. The main cause of coagulation of sols is the action of electrolytes on them, as a result of which two equilibria in the... 

Fig. 48. Stability of colloidal solutions of iron hydroxide of various concentrations (mg/1) as a function of pH.

Sols of iron hydroxide are extremely unstable in the case of reaction with electrolytes, among which the main coagulant is sulfate ion (Fig. 49). With an overall MgS04 content of 10-30 mg/1 (log C = 1.0-1.5), colloidal iron is completely precipitated, both from concentrated solutions (C,... 

The mutual influence of colloids of iron hydroxide and silica occurring together in solutions is of dual character and in some cases leads to mutual coagulation of the sols, but in others to shielding of the iron hydroxide sol. 

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