Gold cyanides, adsorption

Adsorption of cyanide anions can be affected by adsorption of cations. In the solutions containing nonspecifically adsorbed anions, the nature of alkali metal cations was found to influence the measured value of the electrode capacitance at potentials more negative than —0.6 V (versus standard hydrogen electrode (SHE)). At < —l.OV adsorption of CN ions was enhanced in the presence of Li+ and Na+ cations, and inhibited in the presence of Cs+ ions [81]. A combined SERS and density-functional theory has been applied to study cyanide adsorption at Au electrode [82]. The authors have arrived at the conclusion that the polarity of Au—CN bonds falls between that of Au—Cl and Au—Br surface bonds. The binding strength for three different gold surfaces decreased in the order ... 

In a much more through study [68,262-264], Pitt and coworkers examined the kinetics and thermodynamics of both gold and silver cyanide adsorption. They confirmed the decrease in cyanide uptake at high pH (.see Fig. 13) and speculated that this must involve a change in the concentration of active adsorption sites, ... 

Fleming and Nicol [267] reported that adsorption of gold cyanide onto activated carbon is not an irreversible process, and thus confirmed similar findings for silver cyanide 1263]. They also confirmed that the process, like ad.sorption of silver cyanide [263] is exothermic, in contrast to the behavior of some other inorganic ions [125,144,268,172,269] (see also Section lll.B). 

McDougall, G.J., Hancock, R.D., Nicol, M.J., et al. (1980). The mechanism of adsorption of gold cyanide on activated carbon. J. South African Inst. Mining MetalL, 80, 344-56. 

Petersen, F.W. and Van Deventer, J.S.J. (1997). Competitive adsorption of gold cyanide and organic compounds onto porous adsorbents. Sep. Sci. Technol., 32(13), 2087-103. 

All animal fibrous proteins tested accumulated gold-cyanide ion from aqueous solution. Adsorption was highest at pH 2 accumulations were up to 9.8% of the DW for wool, 8.6% for eggshell membrane, 7.1% for chicken feathers, and <3.9% for other materials. In the case of eggshell membrane, adsorbed gold was desorbed with 0.1 M NaOH and the material can be used repeatedly. Eggshell membrane could remove gold-cyanide ion at concentrations near 1.0p,g/L. 

The Mechanism of tiie Adsorption oX Gold Cyanide on Activated Caibon, J. S. Afr. Inst. Min. MetaU., 80, 344-356 (1980). 

Bozzini, B., D Urzo, L., Mele, C. and Romanello, V. (2008) A SERS investigation of cyanide adsorption and reactivity during the electrodeposition of gold, silver, and copper from aqueous cyanocomplexes solutions. The Journal of Physical Chemistry C, 112, 6352-6358. 

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