Removal of Iron

Precipita.tlon, In the simplest case, the solubihty of an impurity in the Hquid metal changes with temperature. Thus the impurity may precipitate as a sohd phase upon cooling. For instance, the removal of iron from tin and of copper from lead are achieved by precipitation. When the soHd is lighter than the Hquid, it floats as a dross on the surface of the melt where it is easily removed by scraping. The process is called dressing. 

In the treatment of poisoning by lead or other metal ions, higher concentrations of chelant can be safely obtained in humans by administering Na2CaEDTA rather than Na EDTA. The metal ion is bound by displacing small amounts of Ca " that the body can tolerate. Use of Na EDTA would result in calcium chelation and thus serious depletion of calcium in the body fluids (44). Removal of iron in Cooley s anemia is accompHshed by using chelants that are relatively specific for iron (45). 

Action of chlorine on uranium oxide to recover volatile uranium chloride Removal of iron oxide impurity from titanium oxide by volatilization hy action of chlorine... 

Removal of iron and inorganic scales is achieved by the use of formulations containing 5 to 10% of acids such as phosphoric or citric acid. 

Although various alkaline citrates and inorganic oxidizing cleaners are sometimes used, the standard procedure, where HC1 is employed, is to add thiourea. This method circumvents the copper corrosion cycle and permits the simultaneous removal of iron and copper deposits. 

Dissolution of the ore, ilmenite, in sulfuric acid and removal of iron impurities. 

In the rhizosphere, microorganisms utilize either organic acids or phytosiderophores to transport iron or produce their own low-molecular-weight metal chelators, called siderophores. There are a wide variety of siderophores in nature and some of them have now been identified and chemically purified (54). Pre.sently, three general mechanisms are recognized for utilization of these compounds by microorganisms. These include a shuttle mechanism in which chelators deliver iron to a reductase on the cell surface, direct uptake of metallated siderophores with destructive hydrolysis of the chelator inside the cell, and direct uptake followed by reductive removal of iron and resecretion of the chelator (for reviews, see Refs. 29 and 54). 

Simple magnetic separators are often used for the removal of iron from the feed to a crusher. 

Largest source removal of iron and slag from furnace (casting)... 

Pattanayak, J., Mandich, N.V., Mondal, K., Wiltowski, T., and Lalvani, S.B., Removal of iron and nickel from solutions by applications of electric field, Environ. Technol., 20, 317, 1999. 

The physical effects induced by ultrasound are also equally interesting. The removal of iron coating by ultrasonic irradiation, from the surface of silica sand used in glass making was found to be an improvement in the electrostatic separation... 

The developed process aimed for the removal of iron and sulfur from coal. While several patents for microbial removal of pyrite from coal exist, this one is unique because of the microbial mixture developed by the group for this purpose, which is partially... 

Matsumoto et al. demonstrated that the removal of iron from diferric transferrin by the tris-hydroxamate siderophore mimic TAGE occurs in two discreet steps (90). The slower step corresponds to iron removal from the more stable C-lobe site on transferrin and the faster step to removal from the N-lobe. The rates of removal are similar to the rates of removal of iron from diferric transferrin by desferrioxamine B (4), signifying similar mechanisms of removal between the two systems (90). 

The pharmacological properties of 108 are not ideal. It removes iron only slowly and it is not well absorbed by oral administration so it has to be administered by injection. Therefore there is need for new chelators. The orally active chelator l,2-dimethyl-3-hydroxypyridin-4-one (LI) 109 is on clinical trial for the treatment of thalassemia (543). Several other chelators which contain 3-hydroxy-4(H)-pyridinone such as 110-112 also possess oral availability, and have comparable activity to 109 for the removal of iron from the liver (544, 545). These... 

There is some qualitative information on iron mobilization. Thus it has been found that the rates of removal of iron decrease in the order... 

Note that plots, such as Figure 5.1, provide information only on the net outcome of chemical reactions. In the case of iron, a small addition does take place in estuaries as a result of desorption of Fe from the surfaces of riverine particles. As these solids move through the estuarine salinity gradient, the major cation concentrations increase and effectively displace the iron ions from the particle surfeces. Since this release of iron is much smaller than the removal processes, the net effect is a chemical removal of iron. Sedimentation of these iron-enriched particles serves to trap within estuaries most of the riverine transport of reactive iron, thereby preventing its entry into the oceans. 

The removal of iron from such species as transferrin or ferritin by hydroxypyridinones, side-rophores, and other chelators is of considerable relevance to the control of iron levels in the body, and indeed to iron metabolism in a range of life forms. Methods and mechanisms for such removal are referenced in Sections 5.4.5.2,5.4.5.5.2, 5.4.5.6.1, and 5.4.5.6.2 below. Interestingly cyanide, one of the most powerful ligands for iron, appears to prefer to bind to iron-transferrin, at the C-terminal Fe, rather than to remove the iron. This adduct is believed to contain the iron in an octahedral environment of three cyanide ligands mer) and nitrogens from two tyrosine residues and a histidine. ... 

Iron(III)-pyrophosphate looks promising as an alternative to iron(III)-carbohydrate preparations for parenteral administration for treatment of anemia.Kinetics of removal of iron from transferrin (tf) by pyrophosphate (pp) were found to be biphasic under certain conditions, with the rapid first phase attributed to the formation of a pp—Fe—tf—CO intermediate.A later study of the kinetics of removal of iron from transferrin employed pyrophosphate and tripodal phosphonates such as nitrilotris(methylenephosphonic acid), N(CH2P03H2)3. For the tripodal ligands there are parallel first-order and saturation pathways, with the latter dominant (contrast the exclusively first-order reaction of ferritin with nitrilotriacetate) for pyrophosphate the paths are roughly equal in importance. The saturation kinetics suggest that tfiFe-phosphonate intermediates play an important role in the kinetics. 

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