Impurities oxidation

Effect of Thermal History. Many of the impurities present in commercial copper are in concentrations above the soHd solubihty at low (eg, 300°C) temperatures. Other impurities oxidize in oxygen-bearing copper to form stable oxides at lower temperatures. Hence, because the recrystallization kinetics are influenced primarily by solute atoms in the crystal lattice, the recrystallization temperature is extremely dependent on the thermal treatment prior to cold deformation. 

The Kroll process for tire reduction of tire halides of refractory metals by magnesium is exemplified by the reduction of zirconium tetrachloride to produce an impure metal which is subsequently refined with the van Arkel process to produce metal of nuclear reactor grade. After the chlorination of the impure oxide in the presence of carbon... 

Zaffer, m. zaffer, zaffre (impure oxide of cobalt). Zaffetika, /. asafetida. 

Los Alamos is processing a wide variety of residues, including Pu-Be neutron sources, polystyrene-Pu02-U02 blocks, incinerator ash, Pu-U alloys and oxides, Pu-Zr alloys and oxides, Pu-Np alloys and oxides, Pu-Th alloys and oxides, etc. Processes have been developed for these scrap items (see Figure 2), but we need to know more about Pu-Np separations Pu-Th separations oxalate precipitations for both plus 3 and plus 4 valences valence stabilization dissolution methods for high-fired impure oxides in-line alpha monitors to measure extremely low concentrations of Pu and Am in HNO3 solutions and solubility of various mixtures of Pu02 and UO2 under a variety of conditions. 

Aluminum is the most abundant metallic element in the Earth s crust and, after oxygen and silicon, the third most abundant element (see Fig. 14.1). However, the aluminum content in most minerals is low, and the commercial source of aluminum, bauxite, is a hydrated, impure oxide, Al203-xH20, where x can range from 1 to 3. Bauxite ore, which is red from the iron oxides that it contains (Fig. 14.23), is processed to obtain alumina, A1203, in the Bayer process. In this process, the ore is first treated with aqueous sodium hydroxide, which dissolves the amphoteric alumina as the aluminate ion, Al(OH)4 (aq). Carbon dioxide is then bubbled through the solution to remove OH ions as HCO and to convert some of the aluminate ions into aluminum hydroxide, which precipitates. The aluminum hydroxide is removed and dehydrated to the oxide by heating to 1200°C. 

This process is particularly useful for the preparation of pure plutonium metal from impure oxide starting material (111). It should also be applicable to the preparation of Cm metal. Common impurities such as Fe, Ni, Co, and Si have vapor pressures similar to those of Pu and Cm metals and are difficult to eliminate during the metallothermic reduction of the oxides and vaporization of the metals. They are eliminated, however, as volatile metals during preparation of the actinide carbides. 

Electrorefining can be used to purify a metal by using alternate electrodes of a pure and impure metal. Impurities oxidized at the anode, which is made of the impure metal, travel into solution. By arranging the cell appropriately, the ion of the metal to be purified is reduced on the pure metal cathode. For example, copper metal that contains lead and iron may be used as one electrode and pure copper as the other electrode in a cell. When the proper voltage is applied, copper, lead, and zinc will be oxidized and move into the electrolyte. Because copper is more easily reduced compared to zinc and lead, it will be plated out at the pure copper cathode. Therefore, this process effectively removes the zinc and lead impurities from the copper. 

Our results clearly show that modification of the electronic state of titanium oxide by metal ion implantation is closely associated with the strong and longdistance interaction which arises between the titanium oxide and the metal ions implanted, as shown in Fig. 13, and not by the formation of impurity energy levels within the band gap of the titanium oxides resulting from the formation of impurity oxide clusters which are often observed in the chemical doping of metal ions, as shown in Figs. 6 and 13. 

A1B1Z 11, B70 50, B4H3 12, A1203 25, Fe203 0.5 Si02 1.5%. It is apparent that this material was not amor boron but a very impure oxide... 

Aluminum is the most abundant metallic element in the Earth s crust and, following oxygen and silicon, the third most abundant element. However, the aluminum content in most minerals is low, and the commercial source of aluminum, bauxite, is a hydrated, impure oxide, Al203-xH20, where x can range up to 3. The bauxite ore, which is red from the iron oxides it contains, is processed to obtain alumina, Al2Q3. 

Nitric Acid.—-The commercial cone, acid generally contains about 70% HN03. Fuming nitric acid (see p. 512) containing about 95% HN03 (D. 1-5) is available commercially. Usual impurities oxides of nitrogen, sulphuric acid, hydrochloric acid, chlorine and iodine. 

Titanous chloride comes on the market in the form of a 20% solution (see p. 485). Usual impurities oxidation products. For the many reducing reactions in which titanous chloride is used it may be replaced by titanous sulphate (obtainable as 20% solution), which should be used when there is possibility of chlorination. 

Iron Filings and Iron Powder.—These are recommended for many operations in place of zinc and tin, on account of cheapness. Usual impurities oxides. 

In carrier flotation, small-sized (several pm diameter) particles become attached to the surfaces of larger particles (perhaps 50 pm diameter, the carrier particles) [630]. The carrier particles attach to the air bubbles and the combined aggregates of small desired particles, carrier particles, and air bubbles float to form the froth. An example is the use of limestone particles as carriers in the flotation removal of fine iron and titanium oxide mineral impurities from kaolinite clays [630]. The use of a fatty acid collector makes the impurity oxide particles hydrophobic these then aggregate on the carrier particles. In a sense, the opposite of carrier flotation is slime coating, in which the flotation of coarse particles is decreased or prevented by coating their surfaces with fine hydrophilic particles (slimes). An example is the slime coating of fine fluorite particles onto galena particles [630],... 

The flowsheet for the FFTF Pu02 production is shown in Figure 2. Briefly, the plutonium metal is converted to an impure oxide by burning the metal in air. This is followed by dissolution of the impure oxide in a 15.6 M HN03 - 0.5 M HF solution. The americium is separated from the plutonium by precipitation of the plutonium as the peroxide. Americium does not form an insoluble peroxide and stays in the filtrate with other cationic impurities. The active peroxide filtrate is slowly dripped into 9 M NaOH. The combination of strong alkali and heat destroys the peroxides and precipitates the americium as the hydroxide. Any residual plutonium in the filtrate, along with other cations, is precipitated also as the hydroxide. The flowsheet for the americium oxide production is shown in Figure 3. 

In contrast to the aggressive, unselective attack of the first, and principal carbon removal mechanism, reaction 7 is quite selective. Factors affecting this selectivity are anode gas permeability, temperature, and the presence of impurity oxidation catalysts. 

Pure C3S contains 73.7% of CaO and 26.3% of SiO. Alites in clinkers typically contain 3-4% of impurity oxides, i.e. oxide components other than those present in the pure compound. Boikova (B4) found a positive correlation between the total percentage of impurity oxides in the alite (/ ) and the percentage of MgO in the clinker (M ). Her re.sults are approximately lilted by the equation = 0.1 -1-2.1. 

Correlations have also been found between the percentages of individual impurity oxides in the alite and in the clinker. In the following discussion, we shall use symbols of the type and to denote these quantities, where O is the cement chemical symbol for the oxide and the suffixes a and c indicate alite and clinker, respectively. For MgO, Kristmann s (Kl) data indicate the approximate relations = 0.67 x for < 3.0 and 2.0 for > 3.0. Yamaguchi and Takagi (Yl) and Terrier (T2) found similar correlations, but with slopes of 0.74 and 0.45, respectively. For AI2O3, Kristmann (Kl) did not find any significant correlation, but for FejO, his data indicate the approximate relation = 0.33 x for F <4%. Boikova (B4) reported ratios of 0.34 to 0.82 for MJM., 0.09 to 0.23 for AJA and 0.17 to 0.36 for F3/F,. 

Clinker belites typically contain 4-6% of impurity oxides, of which the chief ones are usually AI2O3 and Fe203. Correlations have been reported to exist between the MgO contents of belite and clinker (Kl), the Fe20, contents of belite and clinker (Kl), and the total impurity content of the belite and the MgO content of the clinker (B4). Early reports mention a compound KC23S,2, but the K2O content of 3.5% corresponding to this formula is well above those found in clinker belites, and recent electron optical work indicates that the limit of K2O substitution is about 1.2% (C1). 

Pure C,A contains 62.3 /o CaO and 37.7"/o AIjO,. Substantial proportions of both calcium and aluminium are thus replaced, the total content of impurity oxides being typically around 13% for the cubic and up to about 20% for the orthorhombic modification. The content of equivalent Na,0 (Na,0 -I- O.66K2O) appears to be around 1% for the cubic form and 2-4% for the orthorhombic form. None of the analyses indicates alkali contents as high as that required by the formula NC A, even though considerable amounts of silicon arc present. 

The typical composition differs markedly from that of C4AF (46.1% CaO, 21.0% AljOj, 32.9% Fc20,). It contains about 10% of impurity oxides and is much lower in Fc20,. It approximates to CajAl-Fco Mgo 2Sio,i.sTio.o.s05 which is derived from C AF by replacing some of the Fe " by Mg and an equal amount by Si and Ti". Harrisson el oL (H3) observed that, for data from several laboratories, the number of magnesium atoms per formula unit agreed with that of (Si + Ti) this supports the above interpretation. 

When exposed to air and light, phenol turns a red or brown color, the color being influenced by the presence of metallic impurities. Oxidizing agents also hasten the color change. Aqueous solutions of phenol are stable. Oily solutions for... 

Brines contain between 30 and several hundred ppm of iodine (as iodide). The deposits in the USA are mainly in Michigan and Oklahoma. Extraction is similar to that of bromine. Brines are mixed with hydrochloric or sulfuric acid and oxidized with excess chlorine. The elemental iodine formed is blown out with air and absorbed in a sulfuric acid-hydroiodic acid-water mixture in an absorber. Reduction with sulfur dioxide converts the iodine into hydroiodic acid. Part of this is taken off and the hydroiodic acid oxidized with chlorine to iodine. The iodine is filtered off and dried and any organic impurities oxidized by melting under sulfuric acid. 

Electrocorundum is obtained by reduction melting of the purest possible bauxite or alumina at ca. 2000°C with coke and anthracite in an arc reduction furnace, the impurity oxides in the raw material (iron, titanium, silicon) being thereby reduced and to a large extent removed. 

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