Electrolysis reviews

What Do We Need to Know Already This chapter extends the thermodynamic discussion presented in Chapter 7. In particular, it builds on the concept of Gibbs free energy (Section 7.12), its relation to maximum nonexpansion work (Section 7.14), and the dependence of the reaction Gibbs free energy on the reaction quotient (Section 9.3). For a review of redox reactions, see Section K. To prepare for the quantitative treatment of electrolysis, review stoichiometry in Section L. 

A. Goni-Urtiaga, D. Presvytes, K. Scott, Sohd acids as electrolyte materials for proton exchange membrane (PEM) electrolysis review, Int. J. Hydrogen Energy 37 (2012) 3358-3372. 

Electrolysis. Electrowinning of zirconium has long been considered as an alternative to the KroU process, and at one time zirconium was produced electrolyticaHy in a prototype production cell (70). Electrolysis of an aH-chloride molten-salt system is inefficient because of the stabiUty of lower chlorides in these melts. The presence of fluoride salts in the melt increases the stabiUty of in solution, decreasing the concentration of lower valence zirconium ions, and results in much higher current efficiencies. The chloride—electrolyte systems and electrolysis approaches are reviewed in References 71 and 72. The recovery of zirconium metal by electrolysis of aqueous solutions in not thermodynamically feasible, although efforts in this direction persist. 

The uncertain effects of impurities are avoided by periodic or continuous electrolysis of the solution at low current densities to remove metallic contaminants and by filtration through active carbon to remove organic substances. A concise review of the effects of impurities and their removal is given by Greenall and Whittington". 

The expl nature of N trichloride has been known since the end of the 18th century when Sir H. Davy reported, The fulminating oil which you mentioned roused my curiosity and nearly deprived me of an eye. After some months confinement I am again well. (Ref 12). The early history of this compd is reviewed in this Ref. It is readily prepd by the action of Cl on ammonia or Amm salts (Refs 2,6 13) or by the electrolysis of an unstirred coned soln of Amm chloride at 35—40° (Ref 4). A procedure for the prepn of a soln of N trichloride in chlf is described In Ref 1, and prepn on an industrial scale in Ref 7... 

Preparation. The anhyd salt is prepd by dehydration at 300° of the trihydrate, which is prepd by evapn of solns prepd by the interaction of Li sulfate and Ba perchlorate (Ref 4), or by the action of aq perchloric ac on an excess of Li carbonate (Ref 2). Both the anhyd salt and the trihydrate are coml compds, and their manuf has been reviewed (Ref 5). Workers in the USSR have prepd it by the electrolysis of aq Li perchlorate using Pt electrodes (Ref 3)... 

The study of optical isomers has shown a similar development. First it was shown that the reduction potentials of several meso and racemic isomers were different (Elving et al., 1965 Feokstistov, 1968 Zavada et al., 1963) and later, studies have been made of the ratio of dljmeso compound isolated from electrolyses which form products capable of showing optical activity. Thus the conformation of the products from the pinacolization of ketones, the reduction of double bonds, the reduction of onium ions and the oxidation of carboxylic acids have been reported by several workers (reviewed by Feokstistov, 1968). Unfortunately, in many of these studies the electrolysis conditions were not controlled and it is therefore too early to draw definite conclusions about the stereochemistry of electrode processes and the possibilities for asymmetric syntheses. 

The third contribution deals with an rather old synthetic electroorganic reaction, Kolbe-Electrolysis. However, recently this reaction has found so many interesting and important new applications, for example in the synthesis of natmully products or the generation of versatile, even enatiomerically pure, synthetic building blocks, that it was nec sary to cover these new developments in a review. As these reactions are usually very easy to perform without expensive equipment, it is hoped that further applications in many laboratories will be initiated by this article. 

G. Pastztov, The Possibility of Producing Aluminum with Higher Purity on the Basis of the Electrochemical Model of Electrolysis, Mineral Processing and Extractive Metallurgy Review, Vol. 8, p. 119, 1992. 

The use of electrochemical methods for the destruction of aromatic organo-chlorine wastes has been reviewed [157]. Rusling, Zhang and associates [166, 167] have examined a stable, conductive, bicontinuous surfactant/soil/water microemulsion as a medium for the catalytic reduction of different pollutants. In soils contaminated with Arochlor 1260, 94% dechlorination was achieved by [Zn(pc)] (H2pc=phthalocyanine) as a mediator with a current efficiency of 50% during a 12-h electrolysis. Conductive microemulsions have also been employed for the destruction of aliphatic halides and DDT in the presence of [Co(bpy)3]2+ (bpy=2,2 -bipyridine) [168] or metal phthalocyanine tetrasulfonates [169]. 

P.A. Lessing, A review of sealing technologies applicable to solid oxide electrolysis cells, Journal of Materials Science, 42, pp. 3465-3476 (2007). 

Lantagne and Velin [267] have reviewed the application of dialysis, electrodialysis and membrane cell electrolysis for the recovery of waste acids. Because of the new trends governed by environmental pressures, conventional treatment methods based on neutralization and disposal are being questioned. Membrane and electromembrane technologies are considered to be potential energy-efficient substitutes for conventional approaches. Paper mills will focus on the application of ion-exchange membranes namely dialysis, electrodialysis and membrane cell electrolysis for recovery of waste acids. 

Modern data acquisition and evaluation help to optimise the plant under review within a short period of time, to eradicate faults in plant operation and to determine the best materials for the operation of the chlorine electrolysis plant being examined. In this way, inter-relationships are examined between the energy consumption and variables such as membrane types, anode and cathode coatings, temperature, pressure, and concentrations as well as plant shutdowns, brine impurities, materials of construction and manufacturers. It is conceivable that other inter-relationships will come to light that have so far not been considered. 

Our goal in this chapter is to help you understand how to balance redox equations, know the different types of electrochemical cells, and how to solve electrolysis problems. Have your textbook handy—you may need to find some information in electrochemical tables. We will be using the mole concept, so if you need some review refer to Chapter 3, especially the mass/mole relationships. You might also need to review the section concerning net-ionic equations in Chapter 4. And don t forget to Practice, Practice, Practice. 

The fused salt electrolysis technique was successfully applied to the preparation, also as single crystals, of several transition metal compounds. A review on this subject was published by Wold and Bellavance (1972). A systematic treatment of several reactions and processes, was presented possibly somewhat obsolete now and with a drawback due to the presence of several impurities in the synthesis products. The preparation of the following compounds was especially discussed. 

Heterocycles are of great interest in organic chemistry due to their specific properties. Many of these cycles are widely present in natural and pharmaceutical compounds. Electrochemistry appears as a powerful tool for the preparation and the functionalization of various heterocycles because anodic oxidations and cathodic reductions allow the selective preparation of highly reactive intermediates (radicals, radical ions, cations, anions, and electrophilic and nucleophilic groups). In this way, the electrochemical technique can be used as a key step for the synthesis of complex molecules containing heterocycles. A review of the electrolysis of heterocyclic compounds is summarized in Ref. [1]. 

For a recent review of the Kolbe electrolysis reaction see Schafer HJ (1990) Topics in Current Chemistry 152 91... 

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