Aluminium refining

Iron and compounds SPA Iron oxide Eerrous chloride Aluminium refining Steelworks... 

Hydrocarbons, general Iron and compounds SPA Calcium fluoride Iron oxide Aluminium Coal distillation Petrochemicals Refineries Aluminium refining... 

Titanium diboride is an advanced ceramic material with properties similar to those of metals such as high thermal and electrical conductivity. The other distinguishing features of this material are its excellent oxidation resistance and chemical corrosion resistance at elevated temperatures. It can be used as an abrasive and oxidation protection coating as well as the electrode material in aluminium refining. In addition, like other borides it can also be used as a neutron absorber. 

The Elements.—Downs and Adams have reviewed the chemistry of chlorine, bromine, iodine, and astatine/ The role of fluorine in our environment and the use of lichens as monitors for air pollution have been discussed by Dobbs/ Particulate rather than gaseous fluorides were shown to be the pollutants in the vicinity of one aluminium refining plant/ Bronchitis, pneumonia, nervous disorders, and skin diseases were said" to occur more frequently in workers at a Russian AIF, production plant than in a control group. 

Aluminium is obtained on a large scale by the electrolysis of the oxide, dissolved in fused cryolite The oxide, occurring naturally as bauxite, AI2O3.2H2O, usually contains silica and iron(III) oxide as impurities. These must be removed first, since aluminium, once prepared, cannot be freed of other metals (which will be deposited on electrolysis) by refining it. The crude oxide is dissolved under pressure in caustic soda solution the aluminium oxide and silica dissolve and the ironflll) oxide is left ... 

The tlrree impurities, iron, silicon and aluminium are present in the metal produced by the Kroll reduction of zirconium tetrachloride by magnesium to the extent of about 1100 ppm. After dre iodide refining process tire levels of these impurities are 350, 130 aird 700ppm respectively. The relative stabilities of the iodides of these metals compared to that of zirconium can be calculated from the exchange reactions... 

Many metals are extracted from their compounds, as found in ores, by electrolytic processes. By far the most important is the Hall-Heroult process, invented in 1886, for producing aluminium from alumina, itself refined from bauxite ore. Alumina is dissolved in molten cryolite, Na3Alp6, and electrolysed, using carbon anodes and the aluminium itself as cathode. While various details are being steadily improved, the basic process is still the same today. 

The usual extraction procedure is to roast the crushed ore, or vanadium residue, with NaCl or Na2C03 at 850°C. This produces sodium vanadate, NaV03, which is leached out with water. Acidification with sulfuric acid to pH 2-3 precipitates red cake , a polyvanadate which, on fusing at 700°C, gives a black, technical grade vanadium pentoxide. Reduction is then necessary to obtain the metal, but, since about 80% of vanadium produced is used as an additive to steel, it is usual to effect the reduction in an electric furnace in the presence of iron or iron ore to produce ferrovanadium, which can then be used without further refinement. Carbon was formerly used as the reductant, but it is difficult to avoid the formation of an intractable carbide, and so it has been superseded by aluminium or, more commonly, ferrosilicon (p. 330) in which case lime is also added to remove the silica as a slag of calcium silicate. If pure vanadium metal is required it can... 

Yellow phosphorus ignites in molten ammonium nitrate, and mixtures of phosphorus with ammonium nitrate, mercuiy(I) nitrate or silver nitrate explode on impact. Red phosphorus is oxidised vigorously when heated with potassium nitrate [1]. During development of new refining agents for aluminium manufacture, a mixture containing red phosphorus (16%) and sodium nitrate (35%) was being pressed into 400 g tablets. When the die pressure was increased to 70 bar, a violent explosion occurred [2],... 

A group of workers at the institute for Macromolecular Chemistry at Brno, under the leadership of Vesely, began to report in 1955 on investigations into the polymerisation of isobutene. Most of this work has been done with aluminium chloride as catalyst at -78°. The technique used in the earliest work was rather crude, but it was later refined so as to ensure a reasonable degree of dryness. A commendable feature of this work is the attention given to the purity of the reagents and the specification - for some of them, at least - of the nature and concentration of impurities. 

It consists in a deposition of ions from an electrolyte onto the cathode in an electrolytic cell, under the influence of an applied potential. Usually the process is accompanied by material dissolution from the anode. The electrowinning from aqueous solutions is an important commercial method for the production (and/or refinement) of many metals, including, for instance, chromium, nickel, copper, zinc. As for the electrodeposition from non-aqueous solutions, the primary production of aluminium, electrodeposited from a solution of A1203 in molten cryolite, is a typical example. Other metals which may be regularly reduced in a similar way are Li, Na, K, Mg, Ca, Nb, Ta, etc. 

The room-temperature structure of methylammonium aluminium sulphate alum has been re-examined and subjected to least-squares IBM 704 refinement [12]. The 0H3NH3+ ion is disordered. The H-bond system is described, and the crystallographj of the low-temperature ferroelectric phase [13] discussed. 

Indeed, refined experiments carried out using modem methods of investigation including various kinds of electron microscopy, X-ray diffraction, Rutherford backscattering of light ions, electron probe microanalysis, ion mass spectrometry, etc., showed the layers of chemical compounds, a few nanometers thick, to possess all the properties of bulk phases. For example, in the nickel-aluminium reaction couple R.J. Tarento... 

Analyses of electron density distributions have enabled the positions of major elements of high atomic weights such as iron and other transition elements to be located relative to lighter elements such as magnesium and aluminium in mineral crystal structures. The widespread availability of automated X-ray dif-fractometry and least squares refinement programs have increased the availability of site occupancy data for transition metal ions in most contemporary crystal structure refinements. 

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