Metal-cyano complexes separation

Table 3-11. Percentage of free cyanide in aqueous solution of various metal cyano complexes during the separation on an anion exchanger.

Figure 9.5. Ion-interaction separation of metal-cyano complexes. A Waters Nova Pak Cix column was used with 23 77 acetonitrile-water containing 5 mM Waters Low UV PIC A as eluent Detection was by direct spectrophotometry at 214 nm (from Ref. [18] with permission).

The selectivity of the present LIX79 impregnated resins against the extraction of different metal-cyano complexes was studied with a 35% LIX 79 content resin and aqueous solutions with aqueous 10 mg/L metal concentration. Results are plotted in Figure 9.13, which represents the percentage of metal extraction by TVEX/LIX 79 resins against equilibrium pH, showed that the aurocyanide complex is extracted at the most alkaline pH value and, consequently, can be separated selectively from other metal-cyano complexes present in the aqueous phase in this pH range. 

The separation and quantification of cyano complexes of various metals have been successfully carried out by Hilton and Haddad [45]. Cyano complexes of Cu(I), Ag(I), Fe(II), Fe(III), Co(II), Au(I), Au(IlI), Pd(II), and Pt(II) were analyzed by ion-pairing chromatography. The methods can be extended to many speciation problems. 

Au(lll) can be extracted from bromide-containing media with triphenylphospine sulfide dissolved in toluene. This permits separation from Cu(ll), Pb(II), Pd(ll) and Pt(lV). End analysis was by UW spectrophotometry . Separation of [Au(CN)2] from cyano complexes of other metal ions was performed by anion chromatography of the cyano complexes. The elution order of the various species depended on the concentration of sodium perchlorate in the eluting solution. Higher selectivity for gold was achieved when the eluant contained ammonia. Measurement was at 215 nm LOD 5 pg AuL using direct injection . 

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