Elution gold cyanide

An example of chemical destruction of an anionic species is the elution of aurocyanide from an anion-exchange resin with thiourea, a neutral ligand that reacts with gold cyanide in the presence of acid to form a cationic complex. The elution reaction can be described by the following equation ... 

The data in Table 7 suggest that thiosulphate was unable to elute gold bromide from A-500, strong-ion exchange resin but was successful to solubilise about 80% of gold bromide off the carbon. This option should be further explored in search for non-cyanide eluant for gold bromide loaded carbon. 

Thiocyanate can be recovered and recycled from this solution by the precipitation of iron as iron(III) hydroxide.366 Aurocyanide can also be eluted from a strong-base resin by chemical conversion of the gold to a cationic complex with the thiourea ligand, as shown above (equation 98). This method of gold elution is favoured in the Soviet Union, but suffers from the drawback that elution of the other metal cyanide complexes is generally poor, and multi-elution procedures are necessary. 

Caustic cyanide elution of gold bromide from weak base resin and activated carbon was conducted in a water jacketed glass column. The elution conditions and results are presented in Table 5 and profiles are shown in Figure 1. 

In a similar manner as for cyanide, the acidic thiourea was passed through the elution column to collect the aqueous gold. This eluant was tested on strong-base resin (A-500) and activated carbon. The data are presented in Table 6 and profiles are shown in Figure 2. 

Selective separation of gold from many ions by liquid chromatography on columns of Amberlite XAD4 impregnated with (5,4-dimethylaminoben-zylidene-rhodamine) (DMABR) was achieved by Chien et al. [144]. Trace Au(III) (<0.1 ppb) was sorbed at pH 0-1 and was eluted by 0.02 M cyanide solutions at pH 7. Au can be determined in the eluate by atomic absorption or neutron activation. Mercury ions and various anions (thiosulfate, sulfur, iodide, etc.) interfere. 

Gold(I) was quantitated as its c ano complex by HPLC using a C g column (A = 214 nm) and a 32/68 acetonitrile/water (5mM TBA). Note that cyanide ion is extremely toxic and its use poses a great health hazard. Make sure that the solution pH is always extremely basic and that the effluent is disposed of as a segr ted hazardous waste. The complex eluted in 8 min. Pd(ll) and Pt(ll) were resolved from Au(l) when the acetonitrile level was decreased to 23%. In this case elution was complete in 35 min. The detection limit for Au(l) was reported as 0.4 ppb [927]. 

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