Crude zirconium

Zirconium, too, is produced commercially by the Kroll process, but the van Arkel-de Boer process is also useful when it is especially important to remove all oxygen and nitrogen. In this latter method the crude zirconium is heated in an evacuated vessel with a little iodine, to a temperature of about 200° C when Zrl4 volatilizes. A tungsten or zirconium filament is simultaneously electrically heated to about 1300°C. This decomposes the Zrl4 and pure zirconium is deposited on the filament. As the deposit grows the current is steadily increased so as to maintain the temperatures. The method is applicable to many metals by judicious adjustment of the temperatures. Zirconium has a high corrosion resistance and in certain chemical plants is preferred to alternatives such as stainless... 

An extension of the reduction-chlorination technique described so far, wherein reduction and chlorination occur simultaneously, is a process in which the oxide is first reduced and then chlorinated. This technique is particularly useful for chlorinating minerals which contain silica. The chlorination of silica (Si02) by chlorine, in the presence of carbon, occurs above about 1200 °C. However, the silica present in the silicate minerals readily undergoes chlorination at 800 °C. This reaction is undesirable because large amounts of chlorine are wasted to remove silica as silicon tetrachloride. Silica is, therefore, removed by other methods, as described below, before chlorination. Zircon, a typical silicate mineral, is heated with carbon in an electric furnace to form crude zirconium carbide or carbonitride. During this treatment, the silicon in the mineral escapes as the volatile oxide, silicon monoxide. This vapor, on contact with air, oxidizes to silica, which collects as a fine powder in the furnace off-gas handling system ... 

Additional Exercise Potassium fluozirconate from crude zirconium oxide. 

After completion of a run, the cooled unit is opened to a helium atmosphere and drenched with water as a fire precaution, before the bar of zirconium is removed. The considerable amount of surplus crude zirconium is washed and recycled, the overall yield then being about 95 per cent. 

Improvements to the process include the insertion of additional crude zirconium in the interior of the hairpin filament to increase the surface area available. Extra salt cooling must also be provided to the central zone by means of a re-entrant tube let into the base of the reactor. 

Zirconium-95 is the most important of the artificial radioactive isotopes of zirconium. It is placed in pipelines to trace the flow of oil and other fluids as they flow through the pipes. It is also used as a catalyst in petroleum-cracking plants that produce petroleum products from crude oil. 

The crude tetrachloride mixture of zirconium and hafnium is dissolved in ammonium thiocyanate solution. The solution is extracted with methyl isobutyl ketone (MIBK). MIBK is passed countercurrent to aqueous mixture of tetrachloride in the extraction column. Halhium is preferentially extracted into MIBK leaving zirconium in the aqueous phase. Simultaneously, zirconium tetrachloride oxidizes to zirconyl chloride, ZrOCb. When sulfuric acid is added to aqueous solution of zirconyl chloride, the chloride precipitates as a basic zirconium sulfate. On treatment with ammonia solution the basic sulfate is converted into zirconium hydroxide, Zr(OH)4. Zirconium hydroxide is washed, dried, and calcined to form zirconium oxide, Zr02. 

Fuel oils -coking of [FUELS, SYNTHETIC - GASEOUS FUELS] (Vol 12) -from crude oil [PETROLEUM - NOMENCLATURE IN THE PETROLEUM INDUSTRY] (Vol 18) -fuel for incinerators [INCINERATORS] (Vol 14) -zirconium salts of sulfonic acids for [SULFONIC ACIDS] (Vol 23)... 

Zirconium propionate is a polymeric zirconium carboxylate its structure is illustrated in Fig. 10. Use of zirconium propionate markedly increases the adhesion of an ink applied to treated polypropylene film. Figure 11 compares zirconium propionate with titanium acetylacetonate, which is commonly regarded as the industry standard. The standard test method used in the ink industry is the so-called tape test . Sticky tape is placed on the printed film and pressure is applied by the operator s thumb. The tape is then pulled off, by hand, and the amount of ink removed is visually assessed. Although extremely crude, it can be, and is, used for control in the ink industry. 

A similar strategy is employed to purify zirconium, which is used as cladding for fuel rods in nuclear reactors (Section 22.6). The crude metal is heated at about 200°C with a small amount of iodine in an evacuated container to form the volatile Zrl4. The Zrl4 is then decomposed to pure zirconium by letting the vapor come in contact with an electrically heated tungsten or zirconium filament at about 1300°C ... 

Zirconium dioxide is then carbochlorinated a second time (pure chlorination) and converted once again to ZrCl4. This operation is very similar to crude chlorination, but takes place at lower temperature due to more favorable thermodynamics. The purified ZrCl4 product is then reduced to zirconium metal by direct reaction with molten magnesium metal, according to... 

Aluminum is the third most abundant element in the earth s crust (after oxygen and silicon), accounting for 8.2% of the total mass. It occurs most commonly in association with silicon in the aluminosilicates of feldspars and micas and in clays, the products of weathering of these rocks. The most important ore for aluminum production is bauxite, a hydrated aluminum oxide that contains 50% to 60% AI2O3 1% to 20% FeiOs 1% to 10% silica minor concentrations of titanium, zirconium, vanadium, and other transition-metal oxides and the balance (20% to 30%) water. Bauxite is purified via the Bayer process, which takes advantage of the fact that the amphoteric oxide alumina is soluble in strong bases but iron(III) oxide is not. Crude bauxite is dissolved in sodium hydroxide... 

If either thorium or zirconium is present in any amount, it is usually removed at this point by boiling the crude oxalates with (NH4)2C204, which dissolves all the zirconium and most of the thorium.2 Some rare earth oxalates are dissolved slightly,... 

The last member of the platinum metals to be discovered was ruthe> nium. This element was announced by Osann in 1828, who claimed to have found three new metals in some crude platinum ore from the Ural Mountains. To one he gave the name ruthenium, from Ruthenia, a name for Russia. He soon became convinced that one of the metals did not exist and for some time the others were considered to be mixtures of the oxidrs of titanium, iron, zirconium, and silicon. In 1845 Claus examined similar ores and found that they contained a new metal for which he retained the name of ruthenium. 

It is used in the mining industry to recover metals such as copper and nickel. Parasite plants, based on solvent extraction, are used in the phosphate industry to recover by-product uranium from crude phosphoric acid. The uranium concentration in phosphoric acid is very low but, because of the high volume of phosphoric acid that is produced to meet agricultural needs, considerable uranium can be recovered using solvent extraction. In the nuclear industry [5], solvent extraction is used to purify uranium and plutonium [using the plutonium and uranium recovery by extraction (PUREX) process], zirconium from hafnium, and for many other applications. It is also used in environmental applications to clean soil, say, to remove polychlorinated biphenyls (PCBs), dioxins, pesticides, and other hazardous pollutants. 

After cooling to room temperature, the crude reaction mixture was filtered through a glass frit containing Fullers Earth to remove the Ni/C and zirconium salts, and the filter cake was further washed with ether and hexanes. 

The principal steps in this direct chlorination process for converting zircon to ZrCU are shown in Fig. 7.4. Gases from the chlorinating furnace are cooled to around 100°C to condense crude solid ZrCU and FeCU, then cooled further to condense SiCU, TiCU, and AICI3. The crude ZrCU is purified by sublimation with hydrogen in a stainless steel retort. Hydrogen reduces volatile FeCU to nonvolatile FeCU, which remains in the retort with ZrOj and other nonvolatile impurities. This process removes most of the metals associated with zirconium in zircon except hafnium. 

The crude chlorination products of those zirconium-containing minerals that are difficult to break down must be rechlorinated with Cl 3 at 1000°C, yielding crude chlorides, which can then be purified via method IV. 

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