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Studies on role of oxygen in the adsorption of Au(CN) 2 − and Ag(CN) 2 − onto activated carbon
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Studies on role of oxygen in the adsorption of Au(CN) 2 − and Ag(CN) 2 − onto activated carbon

N. Tsuchida and D.M. Muir
Metallurgical Transactions B, Vol.17(3), pp.529-533
1986
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Abstract

Comparative studies of the adsorption of Au(CN) 2 − , Ag(CN) 2 − , and Hg(CN) 2 − onto activated carbon (Norit R2020) have suggested that oxygen and oxygen containing surface functional groups play a role in the adsorption process of Au(CN) 2 − and Ag(CN) 2 − but not in the adsorption of Hg(CN) 2 − . Adsorption of Au(CN) 2 − and Ag(CN) 2 − on carbon degassed at 950 °C under 10−5 torr (1.33 × 10−3 P) vacuum is decreased by 50 pct compared with the adsorption on normal activated carbon. However, in the presence of oxygen in solution, the degassed carbon adsorbs Au(CCN) 2 − to the same extent as normal carbon. The effect of organic solvents and the variation in the potential of the two types of carbon upon adsorption of Au(CN) 2 − were also investigated. These results indicate that activated carbon behaves like an ion-exchange resin but is capable of oxidizing cyanide and cyanide complexes by chemisorbed oxygen. A dual mechanism for the adsorption of Au(CN) 2 − and Ag(CN) 2 − onto activated carbon is therefore proposed, in which cyanide complexes adsorb on carbon by anion exchange with OH− followed by partial oxidative decomposition of Au(CN) 2 − or Ag(CN) 2 − to insoluble AuCN or AgCN.

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