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Click here to return to Gold Metallurgy pageClick here to return to Carbon or Resin Adsorption of Gold, Silver and Other Metals [CIP, CIL, RIP, RIL] and other Cations, Anions or Organics : Testwork, Interpretion and Optimisation.
THE ADSORPTION AND DESORPTION OF AUROCYANIDE FROM ACTIVATED CARBON
David Martin Menne . The adsorption and desorption of aurocyanide from activated carbon. The 5th Aus IMM Extractive MetallurgyConference, Perth, Western Australia, 2 to 4 October, pages 165 to 174
THE ADSORPTION AND DESORPTION OF AUROCYANIDE
FROM ACTIVATED CARBON
DAVID MARTIN MENNE
This monograph presents a unified theory of adsorption and
desorption of aurocyanide on activated carbon. This theory has
proved usefulfor CIP/CIL carbon adsorption and Zadra and AARL
elution process and equipment design; in accounting for the
effects of various water qualities and process temperatures; and
in the development of reagents to improve these processes.
The theory presented is based on rigorous fundamentals :
Classical Eyring theory links initial first order kinetics with
Langmuir isotherm equilibria, and thisisotherm is demonstrated
for the first time to be a consequence of the activated complex
postulate of Eyring theory. Supporting entropy data determined
by the author includes practically all the pioneering CIP plants
built in South Africa and Australia in the early 1980's.
Such data demonstrates the importance of entropy, a measure of
ordering of adsorbed aurocyanide through cationpairing, on
aurocyanide adsorption and desorption. This entropy model has
directed the development of reagent blends for improving the
elution of gold off carbon through sequestering of aurocyanide-
paired alkali and alkali earth cations.
Such reagent-accelerated elution produce more concentrated
eluates. These eluates are more rapidly electrowon, with greater
power efficiency, lessbreakdown/loss of cyanide and caustic,
and less gold sludge formation and loss. The reagent developed
for improving elution also sequesters calcium scale eg out of
carbon pores. This produces cleaner carbon. Such sequestering
also maintains cleaner heat exchange surfaces. These features
reduce od avoid the costs and problems of acid washing.
The cleaner carbon is less prone to degrade itself or thekiln
by slag formation. The cleaner carbon is furthermore more
active, reducing dissolved gold losses, requiring a lower
inventory [with lower attrition and spillage losses], and
loading higher, further reducing demand on the goldroom.
The sequestering action of the reagent on heat exchange surface
scale reduces the demands for heat exchanger cleaning and
maintenance, and their degradationby acid chloride pinholing.
Other elution reagents aimed to produce metals moeities not held
by anionic adsorption and cation pairing avoid low and highly
temperature dependant elution efficiencies. These reagents
provide significant scope for separate metal pre-elution eg of
silver, in a very concentrated eluate, for separate recovery.
This monograph presents a unified...