Iron and Aluminum

There are numerous variations of the wet process, but all involve an initial step in which the ore is solubilized in sulfuric acid, or, in a few special instances, in some other acid. Because of this requirement for sulfuric acid, it is obvious that sulfur is a raw material of considerable importance to the fertilizer industry. The acid—rock reaction results in formation of phosphoric acid and the precipitation of calcium sulfate. The second principal step in the wet processes is filtration to separate the phosphoric acid from the precipitated calcium sulfate. Wet-process phosphoric acid (WPA) is much less pure than electric furnace acid, but for most fertilizer production the impurities, such as iron, aluminum, and magnesium, are not objectionable and actually contribute to improved physical condition of the finished fertilizer (35). Impurities also furnish some micronutrient fertilizer elements. 

Molten anhydrous magnesium chloride is tapped from the bottom of the reactor. Iron, aluminum, and siUcon-based impurities are also converted to their chlorides, which volatili2e out of the reactor. Carbon monoxide is generated from coke, carbon dioxide, and oxygen. The magnesium chloride is sent to electrolytic cells. Russian diaphragmless cells purchased from the defunct American Magnesium Co. are used. 

Soft magnetic materials are characterized by high permeabiUty and low coercivity. There are sis principal groups of commercially important soft magnetic materials iron and low carbon steels, iron—siUcon alloys, iron—aluminum and iron—aluminum—silicon alloys, nickel—iron alloys, iron-cobalt alloys, and ferrites. In addition, iron-boron-based amorphous soft magnetic alloys are commercially available. Some have properties similar to the best grades of the permalloys whereas others exhibit core losses substantially below those of the oriented siUcon steels. Table 1 summarizes the properties of some of these materials. 

Iron—Aluminum and Iron—Aluminum—Silicon Alloys. The influence of aluminum on the physical and magnetic properties of iron is similar to that of silicon, ie, stabilization of the bcc phase, increased resistivity, decreased ductility, and decreased saturation magnetization, magnetocrystalline anisotropy, and magnetostriction. Whereas Si—Ee alloys are well estabHshed for electrical appHcations, the aluminum—iron alloys have not been studied commercially. However, small (up to ca 0.3%) amounts of A1 have been added to the nonoriented grades of siHcon steel, because the decrease in ductiHty is less with A1 than with Si. 

The red cake can be further purified by dissolving it in an aqueous solution of Na2C02- The iron, aluminum, and silicon impurities precipitate from the solution upon pH adjustment. Ammonium metavanadate then precipitates upon the addition of NH Cl and is calcined to give vanadium pentoxide of greater than 99.8% purity. 

Electroplating. Typical wastes produced include spent process solutions containing copper, nickel, chromium, brass, bronze, zinc, tin, lead, cadmium, iron, aluminum, and compounds formed from these metals. 

Zinc is the fourth most widely used metal after iron, aluminum, and copper (lead is fifth). In abundant supply world-wide, zinc is mined and produced mainly in Canada, the former Soviet Union, Australia, Peru, Mexico, and the U.S. Historically, in the U.S. recoverable zinc has been mined in... 

The porcelain enameling industry consists of at least 116 plants enameling approximately 150 million square meters (150 km2) of steel, iron, aluminum, and copper each year (each coat of multiple coats is considered in this total). Porcelain enameling is the application of glass-like coatings to the metals mentioned above. The purpose of the coating is to improve resistance to chemicals, abrasion, and water, and to improve thermal stability, electrical resistance, and appearance. The coating... 

Furthermore, appliances also contain valuable constituents such as gold (from connectors), nickel, copper, iron, aluminum, and permanent magnets, which are worth recovering. 

The mobility of arsenic compounds in soils is affected by sorp-tion/desorption on/from soil components or co-precipitation with metal ions. The importance of oxides (mainly Fe-oxides) in controlling the mobility and concentration of arsenic in natural environments has been studied for a long time (Livesey and Huang 1981 Frankenberger 2002 and references there in Smedley and Kinniburgh 2002). Because the elements which correlate best with arsenic in soils and sediments are iron, aluminum and manganese, the use of Fe salts (as well as Al and Mn salts) is a common practice in water treatment for the removal of arsenic. The coprecipitation of arsenic with ferric or aluminum hydroxide has been a practical and effective technique to remove this toxic element from polluted waters... 

Leaching and desorption of As from its associated mineral surfaces such as iron, aluminum and manganese oxides under the influence of the aquifer complex geochemistry, largely take part in its transport from sediment to aquifer pore-water. Adsorption has widely been considered as the retardation of As transport (Smedley 2003). 

The ash contents of the total trace elements and nitrogen are similar in Tundra ecosystem biomass. The highest concentrations, >0.1% by dry ash weight, are typical for Ca, K, Mg, P, and Si. We can note the increase of iron, aluminum and silicon contents in the underground parts of any plants. 

The characteristic property of soils from Mangrove ecosystems is related to the accumulation of mobile water-soluble forms of iron, aluminum and silicon. The downward increase in soil profile was shown for iron and aluminum and an opposite trend for silicon (Table 14). 

Table 14. The content of water-soluble species of iron, aluminum and silicon in soils of West African Mangrove ecosystems, ppm (after Kovda, 1973).

Phosphate reacts and forms insoluble compounds with many metals, particularly iron, aluminum, and calcium. Under acid soil conditions, both iron and aluminum become more soluble, and thus as soil pH decreases, its phosphate fixing power increases. This means that iron and aluminum react with phosphate to form insoluble species that are not available to plants. Under basic conditions, high concentrations of calcium exist and insoluble calcium phosphates form. Insoluble phosphate species are also formed with other metals that happen to be present however, the three mentioned are generally present in the highest concentration, and so they represent the major reactants with phosphate. Iron, aluminum, and calcium phosphates can also occur as coatings on soil particles. 

In discussing nickel exposure, it is important to consider what form of nickel a person is exposed to and its bioavailability. Such information is not often available. Although high concentrations of nickel may be found in contaminated soil and sediment, it may be embedded in a crystalline matrix or bound to hydrated iron, aluminum, and manganese oxides and, therefore, not bioavailable. 

Various forms of carbon, semigraphite, and graphite materials have found wide application in the metals industry, particulady in connection with the production of iron, aluminum, and ferroalloys. Carbon has been used as a refractory material since 1850, though full commercial acceptance and subsequent rapid increase in use has occurred only since 1945. 

Background Reduction. Two sources of radiation are the major cause of trouble in gamma-ray spectroscopy. The first is the gamma-rays emitted by radioactive contaminants contained in the shielding lead or in iron, aluminum, and stainless steel used in the detector housing and cryogenics system. The second source is the Compton radiation mentioned above. 

Although some of this is used for the production of ultra-pure silicon for semiconductors and for alloys with iron, aluminum, and magnesium, 98% goes for the production of methyl silicon chlorides ... 

Manganese is a little-known element oihcr than lo a small circle of technical specialise who are predominantly metallurgists and chemists. Yet it is [lie Tourth must used metal in terms of tonnage, heing ranked behind iron, aluminum and copper, with in the order of 20 million ions of ore being mined annually (20IX)). 

Extraction of soils for analysis of die readily available nutrients include replacement of exchangeable cations by salt solutions, dilute acids, and dilute alkalies such as NaHCCh. Fluoride solutions ate employed to repress iron, aluminum, and calcium activity during the extraction of phosphorus. Extraction of the soil solution is effected by displacement in a soil column, often through the application of pressure across a pressure membrane. The soil solution is analyzed by conductance and elemental analysis methods. Also, the total elemental analysis of soils is made by Na2CC>3 fusion of the soil followed by classical geochemical analysis methods. 

Metals such as iron, aluminum, and copper can have weak oxide or oxide/metal structures. In such a case, a coupling agent would be of little value until the weakness in the oxide layer had been remedied failure will occur in the weakest region. 

Metal complexes of phenols are important in nature and useful in the laboratory. The metals involved usually include iron, aluminum and magnesium. In nature the flavonoids account for most red, blue, and violet -and to some extent yellow - colors. The majority of yellow colors are the result of the presence of carotenoids and aurones. 

Additional information on adsorption mechanisms and models is in Stollenwerk (2003), 93-99 and Prasad (1994). Foster (2003) also discusses in considerable detail how As(III) and As(V) may adsorb and coordinate on the surfaces of various iron, aluminum, and manganese (oxy)(hydr)oxides. In adsorption studies, relevant laboratory parameters include arsenic and adsorbent concentrations, adsorbent chemistry and surface area, surface site densities, and the equilibrium constants of the relevant reactions (Stollenwerk, 2003), 95. Once laboratory data are available, MINTEQA2 (Allison, Brown and Novo-Gradac, 1991), PHREEQC (Parkhurst and Appelo, 1999), and other geochemical computer programs may be used to derive the adsorption models. 

Adsorption of arsenic Iron, aluminum, and manganese (oxy)(hydr)oxides widely occur as sorbents and coatings on other solid materials in nature. They are often important in adsorbing arsenic from water ((Stollenwerk, 2003), 73 Chapter 3). Below the ZPCs of the (oxy)(hydr)oxides, the presence of... 

The average number of ions in octahedral coordination (E) is 2.07 with values ranging from 1.85 to 2.24. Much of the variation from the theoretical value of 2.00 is due to the presence of iron, aluminum, and magnesium external to the layer. Some of this material is present in chloritic interlayers. 

When the solvent content of the wastewater is high, incineration may be the lowest cost option for disposal. However, VOCs are often stripped for reuse or separate incineration. Soluble salts such as of widely used metals (iron, aluminum, and chromium) and of commonly used anions (cyanide and fluoride) can pose waste disposal problems. Excessive levels of such algal bloom promoters as ammonia and phosphate introduce effluent problems on a large scale. 

Eckert, J.M., and Sholkovitz, E.R. (1976) The flocculation of iron, aluminum and humates from river water by electrolytes. Geochim. Cosmochim. Acta 40, 847-848. 

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