Refining electrolytic

Electrolytic refining. Lead of very high purity can be produced from the electrolytic process. Most electrolytic refineries utilize the Betts process [17]. In this process, lead bullion is cast into anodes and placed in an electrolytic cell which contains an electrolyte of fluorosilicic acid and lead fluorosilicate. The cathode is a thin sheet of high-purity lead referred to as the starter sheet . Lead is deposited on the cathode while the impurities form an adherent, but porous, slime layer on the anode. The slimes are collected for recovery and refining as they contain valuable impurities such as silver, gold, copper, and bismuth. 

The resultant cathodes must undergo a further refining step as small levels of tin and antimony can often be deposited along with the lead. These elements are removed by oxygen softening and/or caustic dressing from the remelted cathodes. To limit the level of cathode contamination, some lead refineries apply partial softening to the lead bullion before the anodes are cast. 

To close the recycling loop, the majority of the production from secondary lead producers returns to the battery manufacturer as alloys and soft lead. At present, secondary producers experience no problems in achieving the purity requirements for most automotive battery alloys, particularly those that are antimony-based. The increased purity requirement in VRLA batteries will, however, make the refining stages more critical. 

Secondary producers often employ the same kettles for alloy formation as are used in the refining process. This is because the equipment needed to alloy certain elements is common to both processes. High-speed stirring and correct fume 

Alloying elements such as copper, silver, and antimony have a much higher melting point than lead and thus require continuous agitation, or stirring, in the kettle to promote dissolution. Tin, on the other hand, has a lower melting point and is the easiest element to alloy with lead. 

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Silver is also recovered during electrolytic refining of copper. Commercial fine silver contains at least 99.9% silver. Purities of 99.999+% are available commercially. 

Tellurium is occasionally found native, but is more often found as the telluride of gold (calaverite), and combined with other metals. It is recovered commercially from the anode muds that are produced during the electrolytic refining of blister copper. The U.S., Canada, Peru, and Japan are the largest Free World producers of the element. 

Another use for cryoHte is in the production of pure metal by electrolytic refining. A high density electrolyte capable of floating Hquid aluminum is needed, and compositions are used containing cryoHte with barium fluoride to raise the density, and aluminum fluoride to raise the current efficiency. 

Electrolytic Eefming. Electrolytic refining (26,27), used by Cominco Ltd. (Trad, B.C., Canada) and Cerro de Pasco Corp. (La Oroya, Pern), as weU as by several refineries in Europe and Japan, removes impurities in one step as slimes. The impurities must then be separated and purified. Before the development of the Betterton-KroU process, electrolytic refining was the only practical method of reducing bismuth to the required concentrations. 

Fig. 16. Electrolytic refining slimes treatment flow diagram. See text.

Electrorefining. Electrolytic refining is a purification process in which an impure metal anode is dissolved electrochemicaHy in a solution of a salt of the metal to be refined, and then recovered as a pure cathodic deposit. Electrorefining is a more efficient purification process than other chemical methods because of its selectivity. In particular, for metals such as copper, silver, gold, and lead, which exhibit Htfle irreversibHity, the operating electrode potential is close to the reversible potential, and a sharp separation can be accompHshed, both at the anode where more noble metals do not dissolve and at the cathode where more active metals do not deposit. 

The matte can be treated in different ways, depending on the copper content and on the desired product. In some cases, the copper content of the Bessemer matte is low enough to allow the material to be cast directly into sulfide anodes for electrolytic refining. Usually it is necessary first to separate the nickel and copper sulfides. The copper—nickel matte is cooled slowly for ca 4 d to faciUtate grain growth of mineral crystals of copper sulfide, nickel—sulfide, and a nickel—copper alloy. This matte is pulverized, the nickel and copper sulfides isolated by flotation, and the alloy extracted magnetically and refined electrolyticaHy. The nickel sulfide is cast into anodes for electrolysis or, more commonly, is roasted to nickel oxide and further reduced to metal for refining by electrolysis or by the carbonyl method. Alternatively, the nickel sulfide may be roasted to provide a nickel oxide sinter that is suitable for direct use by the steel industry. 

Ammonium chloride has a number of iadustrial uses, most importantiy ia the manufacture of dry-ceU batteries, where it serves as an electrolyte. It is also used to make quarryiag explosives, as a hardener for formaldehyde-based adhesives, as a flame suppressant, and ia etching solutions ia the manufacture of ptinted circuit boards. Other appHcations iaclude use as a component of fluxes ia ziac and tin plating, and for electrolytic refining of ziac. 

Refining of Vanadium. In addition to the purification methods described above, vanadium can be purified by any of three methods iodide refining (van Arkel-deBoer process), electrolytic refining in a fused salt, and electrotransport. 

Corrosion inhibitors Cosmetics, drugs Electrical insulation Electrolytic refining Fertilizers Fire retardants Glass and glass wool Herbicides Insecticides Leather tanning Photography Textile dyes Wax emulsifier Wool preservatives... 

Fig. 1. Recovery of copper from sulfide ore. The residue from electrolytic refining is processed to recover gold, silver, and selenium. Courtesy of Kennecott...

The end product is either cast as anodes for electrolytic refining or, rarely, as ingots for sale as fire-refined copper. A horizontal casting wheel with 12—32 horizontal molds is normally used for anode casing. Using continuous casting machines, the copper is cast as a continuous strip to be cut to the required anode shape (28). 

Developments. Electrolytic refining requires a large capital investment, and labor costs per kilogram of copper produced are high. Most refineries have traditionally operated at current densities of about 240 A/m. Thus, a tank house area of approximately 40 m is required per ton of copper produced daily. The use of higher current densities reduces capital requirements but may impair deposition efficiency and product quaUty. 

Potassium cyanide is primarily used for fine silver plating but is also used for dyes and specialty products (see Electroplating). Electrolytic refining of platinum is carried out in fused potassium cyanide baths, in which a separation from silver is effected. Potassium cyanide is also a component of the electrolyte for the analytical separation of gold, silver, and copper from platinum. It is used with sodium cyanide for nitriding steel and also in mixtures for metal coloring by chemical or electrolytic processes. 

In the most common hydrometallurgical process for zinc manufacturing, the ore is leached with sulfuric acid to extract the lead/zinc. These processes can operate at atmospheric pressure or as pressure leach circuits. Lead/zinc is recovered from solution by electrowinning, a process similar to electrolytic refining. The process most commonly used for low-grade deposits is heap leaching. Imperial smelting is also used for zinc ores. 

It is then precipitated by adding Zn dust. Electrolytic refining may then be used to provide gold of 99.99% purity. ... 

WEB Zinc is produced by electrolytic refining. The electrolytic process, which is similar to that for copper, can be represented by the two half-reactions... 

The metals are obtained from the metallic phase of the sulphide matte or the anode slime from electrolytic refining of nickel. In the traditional process for the platinum metals, their separation was facilitated by their solubility in aqua regia and convertibility into PdCl - or PtCl - salts. Nowadays, substantial amounts are obtained using solvent extraction. 

C21-0087. Aluminum refining requires large amounts of electricity. Calculate the masses of A1 and Na that are produced per mole of charge by electrolytic refining of AI2 O3 and NaCl. 

Marchandise H, Vandendriessche S (1985) The Certification of the Impurity Contents (Ag, As, Bi, Cd, Ni, Sb, Se, Sn, Te, T1 and Zn) in Three Grades of Lead, Electrolytically Refined Lead BCR No 286, Thermally Refined Lead BCR No 287, Lead with Added Impurities BCR No 288. European Commission Report EUR 9665 EN. Community Bmeau of Reference, Brussels. Merry f (1995) Reference materials for monitoring nutrients in sea water environment, approach, preparation, certification and their use in environmental laboratories. Fresenius J Anal Chem 352 148-151. 

Electrolytic refining does produce wastewaters that must be treated and discharged, reused, or disposed in some manner. Many facilities use a wastewater treatment operation to treat these wastes. 

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