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The role of cyanide in the multi-component
elution of cyanide complexes from activated carbon At
high temperature and with cyanide pretreatment the elution of metal cyanides from
activated carbon in a column is independent of flow rate. Therefore, an equilibrium model
based on the multi-component Freundlich isotherm could be used to simulate the competitive
desorption of gold and copper cyanides from activated carbon. The elution profiles of free
cyanide and the spectator cation had to be modelled as a precursor to the modelling of
elution profiles for the metal cyanides. The dependence of the desorption equilibrium
parameters on cyanide pre-treatment also had to be considered. In the model for the
removal of free cyanide the rate of the cyanide destruction in the bulk solution was
included by combining the hydrolysis and oxidation reactions that revealed first order
kinetics. The rate of cyanide decomposition in the carbon pores was assumed to change with
the amount of cyanide already decomposed at a specific temperature. It was also important
to consider the dependence of equilibrium parameters on the concentration of spectator
cations. The introduction of a competition coefficient adequately described the
competitive effect of copper on gold elution profiles. |
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