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The ion exchange phenomenon of acetylene black

Thesis (MTech (Chemical Engineering)--Cape Technikon, Cape Town,1996 / Acetylene Black IACB) IS a pure form of carbon which is used in the battery,
plastics, printing and rubber industries. It is extensively used in the battery
industry to absorb electrolyte and to lower the electrical resistance of dry cell
batteries. It is the attempt of this thesis, to investigate the surface characteristics '---------._-- -,- ...• -...•--- .. ------.. _.. --- "'-
and structure of ACB by using it as an adsorbent for cyanide complexes, in
particular gold cyanide.
The thesis is predominantly aimed at identifying the mechanism of metal cyanide
adsorption onto ACB, viz. ion exchange and/or physical adsorption. In order to
quantify the mechanism of adsorption, comparative studies with other adsorbents
currently used in the mining industry, such as activated carbon, were conducted.
These studies revealed various similarities in the metal adsorption process between
ACB and activated carbon, thus indicating physical adsorption rather than ion
exchange to be the dominant mechanism for metal adsorption from solution.
The rate of metal adsorption onto acetylene black was relatively fast compared to
activated carbon. Furthermore, adsorption profiles revealed that intraparticle
diffusion was negligible when a metal was adsorbed onto ACB from solution. This
indicates that acetylene black has a predominantly amorphous structure, although
X-ray diffractrometry indicates a certain degree of graphitisation associated with
ACB.
The small surface area of ACB, together with the lack of intraparticle diffusion,
resulted in the rapid attainment of the equilibrium metal loading on ACB. Moreover,
this equilibrium metal loading was far less than that of activated carbon and ionexchange
resin. While pH, temperature and strong oxidizing agents had a marked
effect on the adsorption profile of metal cyanides onto ACB, the effect of oxygen
enrichment and organic solvents was negligible. Furthermore, the adsorption of
gold onto ACB is best explained by a Freundlich-type isotherm. As is the case with
activated carbon and ion exchange resin, gold is eluted from ACB by a NaOH
solution. It was also found that the elution efficiency is influenced by a change in
temperature.
Changes in operating variables in the production of ACB had an effect on the
absorption stiffness of the product. Both an increase in acetylene feed rate and
operating temperature reduced the absorption stiffness of the product.

Identiferoai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:cput/oai:localhost:20.500.11838/909
Date January 1996
CreatorsCoetzee, Johannes Wilhelm
PublisherCape Technikon
Source SetsSouth African National ETD Portal
LanguageEnglish
Detected LanguageEnglish
TypeThesis
Rightshttp://creativecommons.org/licenses/by-nc-sa/3.0/za/

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