Thesis (MTech (Chemical Engineering))--Cape Technikon, Cape Town, 2000 / In a typical gold-recovery plant, it is estimated that a substantial amount of the gold in
residues may be in the form that is recoverable by cyanidation. The gold in residues can
be ascribed broadly to (l) the presence of cyanicides, which consume the cyanide radical
and thus inhibit dissolution of gold, (2) refractory gold resulting from coatings on some
gold particles, (3) large gold particles incompletely dissolved due to inadequate contact
time, (4) unliberated gold as a result of too coarse a milled product, and (5) gold
dissolved during leaching, then adsorbed by other minerals or by carbonaceous matter in
the pulp. This study focuses on the latter, where dissolved gold is pregrobbed during
leaching by adsorbent materials in the ore. The term pregrobbing refers to the active
adsorption ofgold from cyanide pregnant solutions by components ofthe ore.
It has been suggested that gold already dissolved by cyanide may be adsorbed by other
minerals and by carbonaceous matter in the pulp. The presence ofcarbonaceous matter in
gold ores presents a two-fold problem namely, the poor release of gold from the
carbonaceous matrix and the uptake of dissolved gold by the carbonaceous leach
residues. Studies by several other investigators using ores from various parts of the world
have similarly shown that the natural carbonaceous matter associated with refractory gold
ores often behaves like activated carbon when in contact with aurocyanide solutions.
Some debate also exists over the extent to which gold may be adsorbed onto the surfaces
of minerals. Different authors have identified that minerals such as' pyrite, copper
sulphides, quartz and layered silicates, such as kaolin, phlogopite and ilIite exhibit gold
adsorbing properties.
Activated carbon was first used as a model pregrobber in batch kinetic adsorption
experiments in the presence of a gold selective strong base anion-exchange resin.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:cput/oai:localhost:20.500.11838/907 |
| Date | January 2000 |
| Creators | Van den Berg, Rudolf |
| Publisher | Cape Technikon |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | http://creativecommons.org/licenses/by-nc-sa/3.0/za/ |
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