Element electrolytic production

Electrolysis, the splitting (lysing) of a substance by the input of electrical energy, is often used to decompose a compound into its elements. Electrolytic cells are involved in key industrial production steps for some of the most commercially important elements, including chlorine, copper, and aluminum. The first laboratory electrolysis of H2O to H2 and O2 was performed in 1800, and the process is still used to produce these gases in ultrahigh purity. The electrolyte in an electrolytic cell can be the pure compound (such as H2O or a molten salt), a mixture of molten salts, or an aqueous solution of a salt. The products obtained depend on several factors, so let s examine some actual cases. 

Arsenic is sometimes used in the manufacture of its compounds, but more often in alloys. Small quantities, o-i to o 2 per cent, are added to lead for the production of shot (p. 196). Arsenical lead anodes are used in the electrolytic production of zinc. Alloys with antimonial lead containing 1 to 2 per cent of arsenic and sometimes other elements are used for sheaths for electric cables, etc. Arsenical coppers and bronzes are used for high temperature work such as locomotive fireboxes, etc. 

The desalination of brackish water by electrodialysis and the electrolytic production of chlorine and caustic soda are the two most popular processes using ion-exchange membranes. There are, however, many other processes such as diffusion dialysis, Donnan dialysis, electrodialytic water dissociation, etc. which are rapidly gaining commercial and technical relevance. Furthermore ion-exchange membranes are vital elements in many energy storage and conversion systems such as batteries and fuel cells. 

Tasaka A, Kobayashi H, Negami M, Hori M, OsadaT, Nagasaki K, Ozaki T, Nakayama H, Katamura K (1997) Effect of trace elements on the electrolytic production of NF3. J Electrochem Soc 144 192... 

Hevesy started as an electrochemist, since the topic of his dissertation was the production of alkali metals by melt electrolysis [12], He published several electrochemical papers on the electrolytic production of metals [13] but also on several other electrochemical topics, e.g., on the electrocapillarity [14], Nevertheless, we do not consider him as an electrochemist since he became famous as a discoverer of a new element, hafnium, and especially as a leading person in the area of radioactivity. He studied the electrochemistry of radioactive elements (Figs. 12.8,12.9, and 12.10) and used the electrochemical techniques successfully also in radiochemistry, ionic diffusion in electrolytes, and metals [15-19]. In 1913, he carried out the first radioactive tracer experiment with Friedrich Adolf Paneth in Vienna [20]. The use of tracer technique opened up new vistas also in electrochemistry. It provided a reliable method to investigate kinetics and equilibrium of electrode processes, e.g., adsorption dissolution, deposition, and underpotential deposition of metals. 

Salt was first electrochemicaHy decomposed by Cmickshank ia 1800, and ia 1808 Davy confirmed chlorine to be an element. In the 1830s Michael Faraday, Davy s laboratory assistant, produced definitive work on both the electrolytic generation of chlorine and its ease of Hquefaction. And ia 1851 Watt obtained the first Fnglish patent for an electrolytic chlorine production cell (11). 

It is easy to reduce anhydrous rare-earth hatides to the metal by reaction of mote electropositive metals such as calcium, lithium, sodium, potassium, and aluminum. Electrolytic reduction is an alternative in the production of the light lanthanide metals, including didymium, a Nd—Pt mixture. The rare-earth metals have a great affinity for oxygen, sulfur, nitrogen, carbon, silicon, boron, phosphoms, and hydrogen at elevated temperature and remove these elements from most other metals. 

Selective Reduction. In aqueous solution, europium(III) [22541 -18-0] reduction to europium(II) [16910-54-6] is carried out by treatment with amalgams or zinc, or by continuous electrolytic reduction. Photochemical reduction has also been proposed. When reduced to the divalent state, europium exhibits chemical properties similar to the alkaline-earth elements and can be selectively precipitated as a sulfate, for example. This process is highly selective and allows production of high purity europium fromlow europium content solutions (see Calcium compounds Strontiumand strontium compounds). 

Another approach for the production of phosphine is an aqueous electrolytic process, whereby nascent hydrogen reacts with elemental phosphoms (70). Phosphine is produced at the cathode. 

By-Product Recovery. The anode slime contains gold, silver, platinum, palladium, selenium, and teUurium. The sulfur, selenium, and teUurium in the slimes combine with copper and sUver to give precipitates (30). Some arsenic, antimony, and bismuth can also enter the slime, depending on the concentrations in the electrolyte. Other elements that may precipitate in the electrolytic ceUs are lead and tin, which form lead sulfate and Sn(0H)2S04. 

A Perkin-Elmer 5000 AAS was used, with an electrically heated quartz tube atomizer. The electrolyte is continuously conveyed by peristaltic pump. The sample solution is introduced into the loop and transported to the electrochemical cell. A constant current is applied to the electrolytic cell. The gaseous reaction products, hydrides and hydrogen, fonued at the cathode, are flowed out of the cell with the carrier stream of argon and separated from the solution in a gas-liquid separator. The hydrides are transported to an electrically heated quartz tube with argon and determined under operating conditions for hydride fonuing elements by AAS. 

The physicochemical properties of carbon are highly dependent on its surface structure and chemical composition [66—68], The type and content of surface species, particle shape and size, pore-size distribution, BET surface area and pore-opening are of critical importance in the use of carbons as anode material. These properties have a major influence on (9IR, reversible capacity <2R, and the rate capability and safety of the battery. The surface chemical composition depends on the raw materials (carbon precursors), the production process, and the history of the carbon. Surface groups containing H, O, S, N, P, halogens, and other elements have been identified on carbon blacks [66, 67]. There is also ash on the surface of carbon and this typically contains Ca, Si, Fe, Al, and V. Ash and acidic oxides enhance the adsorption of the more polar compounds and electrolytes [66]. 

The most widely used element-selective electrochemical detector is the Hall electrolytic conductivity detector (HECD) [98,116,206]. This is an improved version of an earlier design by Coulson [207,208]. In both detectors the reaction products are swept from the furnace into a gas-liquid contactor trtiere they are mixed with an appropriate solvent. The liquid phase is separated from insoluble gases in a gas-liquid separator and then passed through a conductivity cell. The Coulson detector employed a... 

---