Iron, cation exchange

Sea water Co-precipitation with iron hydroxide, purified by anion exchange, coprecipitation with BiP04, cation exchange, electrodeposition a -Spectroscopy No data 64-79% Lovette et al. 1990... 

Atomic absorption spectrometry has been used to determine caesium in seawater. The method uses preliminary chromatographic separation on a strong cation exchange resin, ammonium hexcyanocobalt ferrate, followed by electrothermal atomic absorption spectrometry. The procedure is convenient, versatile, and reliable, although decomposition products from the exchanger, namely iron and cobalt, can cause interference. 

The total deionisation of mineral water can be achieved by a combination of a cation exchanger resin and an anion exchanger resin. This has found application in the deionisation of boiler waters to avoid the formation of scales of the dissolved salts on the walls of boilers and pipes. This is also used in the deionisation of water to be used in domestic steam irons. 

Montmorillonite An iron-rich clay mineral that has a very high cation exchange capacity. Unlike the other clay minerals, a significant amount of sedimentary montmorillonite is hydrothermal in origin. 

Favre F, Tessier D, Abdehnoula M, Genin JM, Gates WP, Boivin P. 2002. Iron reduction and changes in cation exchange capacity in intermittently waterlogged soil. European... 

Treatment of lithium enolate species, such as 7, with a variety of metal halide species produces enolates with different reactivities in particular, diethylaluminum(IH) and copper(I) species have been found to profoundly alter stereodifferentiation in reactions of iron acyl enolates (see Section D.1.3.4.2.5.1.). It has not been established whether complex formation or discrete ti ansmetalation occurs usually, a temperature increase from — 78 °C to — 42 °C is required for maximum effect, suggesting that cation exchange is responsible. In some cases, such additives exert an influence at —78 °C13, and this has been attributed to simple Lewis acid-type interactions with the substrate instead of transmetalation of the enolate species. For simplicity, when such additives are allowed to react with enolate species at temperatures of — 42 =C and above prior to the addition of other reagents, the process shall be referred to as transmetalation. 

If the iron is present as humic acid complexes,11 these can be coagulated with alum (Section 14.2). Instead of trying to precipitate the iron, it may be better to keep it in solution, in which case it can be complexed with a chelating agent such as NTA3- or EDTA4. As a last resort, Fe2+ or Fe3+ can be removed by cation exchange, but the absorption on the zeolite or resin is usually irreversible. 

To extract the iron(III) ions, pass 20 ml of a hot 2 M hydrochloric acid solution through the cation exchanger. Gather the solution flowing out from the column in a 250-ml flask. Use the reaction with potassium hexacyanoferrate(II) to check for the completeness of iron extraction. 

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