Electrolytic refining cells

The beginning of modeling of polymer-electrolyte fuel cells can actually be traced back to phosphoric-acid fuel cells. These systems are very similar in terms of their porous-electrode nature, with only the electrolyte being different, namely, a liquid. Giner and Hunter and Cutlip and co-workers proposed the first such models. These models account for diffusion and reaction in the gas-diffusion electrodes. These processes were also examined later with porous-electrode theory. While the phosphoric-acid fuel-cell models became more refined, polymer-electrolyte-membrane fuel cells began getting much more attention, especially experimentally. 

Metallic copper obtained above is purified by electrolytic refining. The electrolytic cell consists of a cathode made of thin sheets of very pure copper connected to the negative terminal of a direct-current generator, and a lump of extracted impure copper from the ore serving as an anode. A solution of cop-per(II) sulfate in sulfuric acid is used as electrolyte. Electrolysis causes trans-... 

Bipolar electrodes are suspended or inserted into an oblong vessel of rectangular cross section or arranged to form the so called filter press cell. The first method is used mainly for the electrolytical refining of metals where the crude... 

The technical process of copper refining is an important example of an electrolytic concentration cell. Two copper electrodes operate in the same Cu++-containing electrolyte, one as anode, the other as cathode. Clearly, at equilibrium, E - 0. The current flow at the anode will dissolve Cu as Cu++, raising the concentration there. On the other hand, at the cathode, Cu++ deposits as Cu. Consequently, near the cathode, the Cu++ concentration decreases. Thus, a cell voltage will establish that opposes the applied voltage and leads to a loss of energy. Note that the aim of the process is the... 

Figure 6.42. Picture of the anode configuration for the fourth-generation segmented cell designed by LANL [43], (Reprinted from Journal of Power Sources, 123(2), Bender G, Wilson MS, Zawodzinski TA. Further refinements in the segmented cell approach to diagnosing performance in polymer electrolyte fuel cells, 163-71, 2003, with permission from Elsevier and the authors.)...

Bender G, Wilson MS, Zawodzinski TA (2003) Further refinements in the segmented cell approach to diagnosing performance in polymer electrolyte fuel cells. J Power Sources 123(2) 163-71... 

Electroplating, Etc.—The energy required for electroplating, galvanoplasty, detinning and electrolytic refining of metals varies with the metals involved and solutions used. From 1 to 100 amp. may be needed per square inch of cathode surface, at 0.1 to 4 volts per cell. Direct current is supplied from small generators at 5 or 6 volts, and a separate rheostat is required for each cell or tank. 

Selenium is quite rare (9 X 10 % of the earth s crust). It occurs mainly as an impurity in sulfur, sulfide, and sulfate deposits. It is obtained from the flue dusts that result from roasting sulfide ores and from the anode mud formed in the electrolytic refining of copper. It is used as a red coloring in glass. The gray crystalline allotropic form of selenium has an electrical conductivity that is very light-sensitive, so it is used in photocopy machines and in solar cells. 

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. 

When an electrolytic product is required of very high purity, a refining cell may be employed instead of a winning cell, i.e. a soluble anode is fabricated of the required metal, in a less pure condition, which may have been produced by a method other than electrolysis, or which may be scrap from later metallurgical processing, In this case chlorine is not liberated in the cell, and gaseous corrosion may be eased. It is of course necessary to reject some or all of the inert salts after each electrolysis batch, in order to obtain the full benefit of the electrolytic purification, since the impurities are of such a nature that they remain undeposited on the cathode. 

Plutonium metal is often purified by electrolytic refining the plutonium sample is immersed in a molten chloride salt under an inert atmosphere, comprising the anode in an electrolytic cell. Liquid Pu metal is collected on the surface of a tungsten cathode and drips off into a collector. Transition-metal contaminants remain in the residue of the anode, and rare earths and other actinides concentrate in the molten salt. The yield of purified Pu metal can be as high as 97%. Zone melting is also used to purify metallic plutonium the plutonium is fabricated into a bar along which a high-temperature zone is passed. As the melt zone is moved... 

In the Redox Chemistry of Iron and Copper movie (eChapter 23.8), copper from a copper sulfate solution is reduced and forms a coating of copper metal on an iron nail. Based on this observation, predict what would happen to an iron impurity in crude copper during the electrolytic refinement of copper. Would the iron be oxidized and become part of the electrolyte solution in the cell, or would it become part of the anode sludge Explain. 

The most common approach for the production of high purity silver is electrolytic refining. Anodes of silver dor6 are electrolysed using a silver nitrate electrolyte and pure silver is deposited on stainless steel cathodes. Silver deposits on the cathode in a dendritic crystalline form, which readily separates from the cathode by scraping and collects in the bottom of the cell. The anode is separated by a cloth membrane and retains the anode slimes. The slimes contain gold, platinum and palladium and are further processed to recover these metals. 

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