Zinc cation exchange

In the recovery of cadmium from fumes evolved in the Imperial Smelting process for the treatment of lead—zinc concentrates, cadmium is separated from arsenic using a cation-exchange resin such as Zeocarb 225 or Ambedite 120 (14,15). Cadmium is absorbed on the resin and eluted with a brine solution. The cadmium may then be recovered direcdy by galvanic precipitation. 

Catalysts. The choice of the proper catalyst for an esterification reaction is dependent on several factors (43—46). The most common catalysts used are strong mineral acids such as sulfuric and hydrochloric acids. Lewis acids such as boron trifluoride, tin and zinc salts, aluminum haHdes, and organo—titanates have been used. Cation-exchange resins and zeoHtes are often employed also. 

Ammonia NH3 Corrosion of copper and zinc alloys by formation of complex soluble ion Cation exchange with hydrogen zeolite, chlorination, deaeration, mixed-bed demineralization... 

Theory. Conventional anion and cation exchange resins appear to be of limited use for concentrating trace metals from saline solutions such as sea water. The introduction of chelating resins, particularly those based on iminodiacetic acid, makes it possible to concentrate trace metals from brine solutions and separate them from the major components of the solution. Thus the elements cadmium, copper, cobalt, nickel and zinc are selectively retained by the resin Chelex-100 and can be recovered subsequently for determination by atomic absorption spectrophotometry.45 To enhance the sensitivity of the AAS procedure the eluate is evaporated to dryness and the residue dissolved in 90 per cent aqueous acetone. The use of the chelating resin offers the advantage over concentration by solvent extraction that, in principle, there is no limit to the volume of sample which can be used. 

Zinc is electrodeposited from the sodium zincate electrolyte during charge. As in the zinc/bromine battery, two separate electrolytes loops ("posilyte" and "nega-lyte") are required. The only difference is the quality of the separator The zinc/ bromine system works with a microporous foil made from sintered polymer powder, but the zinc/ferricyanide battery needs a cation exchange membrane in order to obtain acceptable coulombic efficiencies. The occasional transfer of solid sodium ferrocya-nide from the negative to the positive tank, to correct for the slow transport of complex cyanide through the membrane, is proposed [54],... 

Zinc Complexation withp-tosyl-8-aminoquinoline and adsorption on cation exchange resin Spectrofluorimetry 0.1 nM absolute [609]... 

A theoretical model for the adsorption of metals on to clay particles (<0.5 pm) of sodium montmorillonite, has been proposed, and experimental data on the adsorption of nickel and zinc have been discussed in terms of fitting the model and comparison with the Gouy-Chapman theory [10]. In clays, two processes occur. The first is a pH-independent process involving cation exchange in the interlayers and electrostatic interactions. The second is a pH-dependent process involving the formation of surface complexes. The data generally fitted the clay model and were seen as an extension to the Gouy-Chapman model from the surface reactivity to the interior of the hydrated clay particle. 

Check for the complete extraction of the zinc cations from the cation exchanger. For this end, put a drop of the solution flowing out on a watch glass, add two drops of a 4 Af solution of hydrochloric acid and one drop of a potassium hexacyanoferrate(Il) solution. If zinc ions are present, a white precipitate of zinc hexacyanofer-rate(II) forms. After extraction of the zinc, wash the resin with 20 ml of water. Dispose of the washing water. 

The temperatures reported in the kinetic studies range from 260 to 350°C. In most of the investigations, the hydration rates were found to be of the first order with respect to acetylene [300,302—304]. With zinc phosphate [303], cadmium—calcium phosphate [300] and cation-exchanged zeolites [304], the rates were independent of the concentration of water. Thus the simple kinetic equation... 

Selectivities of potential hydrometallurgical interest that were demonstrated recently400 are the very good extractions of nickel and cobalt from acetonitrile, propylene carbonate, sulfolane or dimethylformamide by a cation exchanger copper, iron(II), iron(III) and zinc, present in the same solution, are either weakly extracted or are not extracted at all. It is also possible for copper to be extracted selectively from Fe3+ ions with an anion exchanger in dimethyl sulfoxide, dimethylformamide or dimethylacetamide.400... 

Mesityl oxide can also be produced by the direct condensation of acetone at higher temperatures. This reaction can be operated in the vapor phase over zinc oxide (182), or zinc oxide—zirconium oxide (183), or in the liquid phase over cation-exchange resin (184) or zirconium phosphate (185). Other catalysts are known (186). 

An alternative method of preparing highly active zinc hexacyano-cobaltate catalyst involved the use of hexacyanocobaltic acid prepared by passing the potassium salt through cationic exchange resin (Rohm and Haas A-15). 

The extraction of zinc with the cation exchanger di(2-ethylhexyl)phosphoric acid, RH, is recommended by the EFCE as a test system for RE. Physical properties, handling, equilibrium data, etc. are documented on the internet (http // www. dechema.de/Extraction, http //www.icheme.org/leaming). 

Sometimes these operationally defined procedures have a sound theoretical basis. For example, it is quite reasonable to suppose that leaching with magnesium nitrate solution will displace zinc from cation exchange sites in soils, or leaching with ammonium acetate will displace exchangeable calcium, magnesium, sodium, and potassium. Flame spectrometry, especially flame AAS, is widely used for the analysis of such extracts. 

Zinc(II) and chromium(IV) cations are smaller (0.88 and 0.69 A respectively) than oxygen(II) anions (1.24 A), so one way to view this reaction is through cation migration. The zinc cations need to extract themselves from their oxide octahedral hole and move to the chromium compound to find an available tetrahedral hole. Simultaneously, chromium cations are moving in the direction of the zinc compound. After a few exchanges of cations, the two crystallites look as shown in Figure 5.2. 

Abd-Alfattah, A. and K. Wada. 1981. Adsorption of lead, copper, zinc, cobalt, and cadmium by soils that differ in cation exchange materials. J. Soil Sci, 32 271. 

Figure 3 shows a typical spectrum of the unreduced nitro-prusside samples where iron is introduced only as the anionic Na2Fe(CN)5NO complex. Zinc has been cation exchanged into NH Y before addition of the anionic complex. Figure 4 shows an example of samples similar to the zinc nitroprusside Y zeolite, shown in Figure 3, that are completely reduced to metallic iron by hydrogen. 

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