Cadmium exchange

D. Tinet, A. M. Faugere, and R. Prost, Cd NMR chemical shift tensor analysis of cadmium-exchanged clays and clay gels, J. Phys. Chem. 95 8804 (1991). 

The best evidence for metal fluxionality in Cd7-MT was provided by " Cd NMR saturation transfer experiments, which established the presence of inter- and/or intramolecular metal exchange within the 3-metal cluster of the /3-domain with a half-hfe of the order of 0.5 s. The confirmation of similar processes taking place within the 4-metal cluster, but with a half-hfe of about 16 min, was afforded by metal exchange studies using the radioactive Cd isotope. In this context, it should be noted that the intersite cadmium exchange measured in the 3-metal cluster of MT-1 was found to be much faster than that in MT-2. This finding was in line with the enhanced backbone flexibility recognized in the NMR studies of the former isoform. ... 

The 2 NMR-active nuclei of cadmium are both spin I = /2, and have similar natural abundances (12.75% for " Cd and 12.26% for Cd). However, the relative receptivity of Cd is slightly better (see Chapter 1, Table 1.1), making it the nucleus of choice for many Cd NMR studies. Cadmium NMR has proved useful in studies of semiconducting oxide compounds and alloys, and of cadmium exchange in clay minerals and zeolites. The chemical shifts of Cd compounds are normally reported with respect to aqueous Cd(C104)2 solution. 

The effect of exchanging Cd " into zeolite LTA has been studied by Cd NMR, enabling the identification of 2 different cadmium coordination states in the hydrated form of the zeolite. The effect of cadmium exchange on the silicon and aluminium environments of this zeolite was also investigated using Si and Al NMR spectroscopy (Eldewick et al. 1999). 

Krishnan V V, Suib S L, Corbin D R, Schwarz S, Jones G E (1996), Encapsulation studies of hydrogen on cadmium exchanged zeolite rho at atmospheric pressure . Catalysis Today, 31, 199. 

The quantum effect of reduction of particle size in reducing the band gap of semiconductors and so giving rise to novel optoelectronic properties has stimulated interest in quantum dot inclusion compounds of nanoparticles of semiconductors within zeolite pores.In a pioneering study, Herron and coworkers succeeded in introducing cadmium sulfide clusters within the pores of zeolite Y via the reaction of a cadmium-exchanged zeolite Y with hydrogen sulfide gas (Scheme 6.8). °... 

R. Van Bladel, H. Halen, and P. Cloos, Calcium-zinc and calcium-cadmium exchange in suspensions of various types of clays. Clay Minerals, 28 (1993), 33-8. 

Lover T efa/1997 Electrospray mass spectrometry of thiophenolate-capped clusters of CdS, CdSe and ZnS and cadmium and zinc thiophenolate complexes observation of fragmentation and metal, chalcogenide and ligand exchange processes Inorg. Chem. 36 3711... 

The equivalent amount of cadmium ion exchanged for the silver ion can readily be determined by EDTA titration procedures. 

Stabilization Mechanism. Zinc and cadmium salts react with defect sites on PVC to displace the labHe chloride atoms (32). This reaction ultimately leads to the formation of the respective chloride salts which can be very damaging to the polymer. The role of the calcium and/or barium carboxylate is to react with the newly formed zinc—chlorine or cadmium—chlorine bonds by exchanging ligands (33). In effect, this regenerates the active zinc or cadmium stabilizer and delays the formation of significant concentrations of strong Lewis acids. 

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. 

EFFECT OF QUATERNARY AMMONIUM SAET EXCHANGE CENTER STERIC ACCESSIBILITY ON EXTRACTION OF CADMIUM BROMIDE COMPLEXES... 

Thus, the QASes of the asymmetrical stmcture with improved steric accessibility of the exchange centre show the high selectivity to double-charged cadmium bromide complex ions relative to single-charged ions. 

Table 7. Preparation of Fluorinated Vinylcopper Reagents via Exchange of Cu(I) Halides with Fluorine-Containing Vinybinc or Cadmium Compounds [145]...

Tfifluorovinyl- and ( 0-pentafluaropropenylsilver compounds can be prepared via the exchange reaction of the corresponding cadmium compound with silver trifluoroacetate [144] (equation 189) The 2-pentafluoropropenyl silver compound can be synthesized via a similar exchange reaction of silver tnfluo-roacetate with 2-pentafluoropropenyllithium [279]... 

These considerations show the essentially thermodynamic nature of and it follows that only those metals that form reversible -i-ze = A/systems, and that are immersed in solutions containing their cations, take up potentials that conform to the thermodynamic Nernst equation. It is evident, therefore, that the e.m.f. series of metals has little relevance in relation to the actual potential of a metal in a practical environment, and although metals such as silver, mercury, copper, tin, cadmium, zinc, etc. when immersed in solutions of their cations do form reversible systems, they are unlikely to be in contact with environments containing unit activities of their cations. Furthermore, although silver when immersed in a solution of Ag ions will take up the reversible potential of the Ag /Ag equilibrium, similar considerations do not apply to the NaVNa equilibrium since in this case the sodium will react with the water with the evolution of hydrogen gas, i.e. two exchange processes will occur, resulting in an extreme case of a corrosion reaction. 

Theory. Cadmium and zinc form negatively charged chloro-complexes which are absorbed by a strongly basic anion exchange resin, such as Duolite A113. The maximum absorption of cadmium and zinc is obtained in 0.12 M hydrochloric acid containing 100 g of sodium chloride per litre. The zinc is eluted quantitatively by a 2M sodium hydroxide solution containing 20 g of sodium chloride per litre, while the cadmium is retained on the resin. Finally, the cadmium is eluted... 

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