Lead chloride aqueous electrolysis

Although silver is not treated by solvent extraction in any of the flow sheets, silver is recovered from aqueous solution in several other situations. For these processes, Cytec developed reagents with donor sulfur atoms to extract this soft element. For example, tri-isobutylphosphine sulfide (CYANEX 47IX) extracts silver from chloride, nitrate, or sulfate media selectively from copper, lead, and zinc [32]. The silver is recovered from the loaded organic phase by stripping with sodium thiosulfate, and the metal recovered by cementation or electrolysis. Silver can also be extracted from chloride solution by a dithiophosphinic acid (CYANEX 301) [33]. 

Immediately upon connecting the cell to a source of direct current, a deposit of gray metallic zinc appears on the surface of the cathode and bubbles of chlorine gas appear at the surface of the anode. A simple chemical test for chlorine may be made by leading this gas into an aqueous sodium iodide solution, whereupon the solution assumes a yellow color caused by displacement of iodine by chlorine. Accordingly, it is concluded that the products of the electrolysis of a zinc chloride solution are elemental zinc and elemental chlorine, and the next problem is that of explaining the mechanism by which these products may be produced. 

Potassium nitrite, KN02.—The nitrite is made by the reduction of potassium nitrate by heating it alone, or with metals such as lead and iron, or with substances containing sulphur or carbon. It is also formed from potassium nitrate by electrolysis with a silver cathode and a copper anode, the yield being almost quantitative.8 The pure salt can be obtained by precipitating the aqueous solution with methyl alcohol.9 Another method for the production of the nitrite depends on the double decomposition of silver nitrite and lithium chloride.10... 

In this chapter, roughly one dozen quite different production processes will be summarized. For instance, the most important electrochemical process, the electrolysis of aqueous sodium chloride leading to chlorine, alkali, hydrogen, and chlorine oxygen compounds are incorporated (Sect. 5.2). Other processes are carried out in a small scale only, but have an unchallenged place in the technical chemistry, for instance, the generation of molecular fluorine (Sect. 5.3). Others are of limited importance nowadays, but may gain importance in the future, for example, the electrolysis of water (Sect. 5.4). 

Fig 9.4 - Aqueous chloride electrolysis tor lead (PLACID process). 

The use of aqueous chloride electrolysis in comparison with molten salt systems has the disadvantage of producing a powdered lead cathode deposit in comparison with molten lead. The production of chlorine can be common to both systems but can be avoided in the aqueous system if iron leach solutions are used as the electrolyte, or proton permeable membranes are used to allow for a separate anolyte solution composition. No clear preference has emerged to date from the many process options examined. 

The electrolysis of halogen-containing organic compounds at a sacrificial cathode commonly produces homoleptic organometallic compounds. For example, the electrolysis of aqueous solutions of iodopropionitrile at a tin, lead, or mercury cathode yields respectively [Sn(CH2CH2CN)4], [Pb(CH2CH2CN)4l, or [Hg(CH2CH2CN)2]. The electrolysis of ethyl chloride or ethyl bromide at a lead cathode has been proposed as a mefiiod for ttie preparation of tetraethyllead. ... 

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