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Recovery of metal cyanides using a fluidized bed of resin
Author(s)
Nesbitt, Allan Bernard
Date Issued
1996
Type
Thesis
Publisher
Cape Technikon
Abstract
Metal cyanide complexes are a toxic pollutant in waslewater originating from various industrial and mining activities.
The removal/retrieval ofcyanide and metal cyanide complexes has been studiedby researches for many years, leading
to the establishment of a variety of patents. The mechanisms used by these patents vary from purely chemical
techniques to those using ion exchange Iesins.
In this thesis, ,the feasIbility ofthe recovery ofmetal cyanide complexes by using a strong base macroreticular resin, in
a fluidized bed configuration, has been investigated. The resin in question is presently used in the sugar indnstry
where its main application is the recovery oflarge organic molecules similar in nature to metal cyanides.
The selected resin was contacted with synthetic solntions of various metal cyanide complexes. for the purposes of
evaluating performance in the adsorption th..."feOf. It was found that polyvalent metal cyanide molecules were adsOlbed
efficiently, while divalent metal cyanide molecules were adsorbed satisfactorily.
The loaded resin was also evalnated for the ease with which the metal cyanides conId be removed. It was discovered
that a brine solntion ofpH 7, conId effectively remove all metal cyanide complexes. This test-work was of particular
importance as it is well !moon that the removal ofmetal cyanides from strong base metals is not easily achieved.
To distingnish the fluidization characteristics of the selected resin (or any resin for that matter), a method of
modelling the expansion of a flnidized resin bed was proposed, that takes into account the diflicnIties associated with
the byclrod:)nantic charncteristics of a macroporous resin of this nature. The technique is based on the Serial Afadel
which is a discretised application of the Z3ki and Richardson equation. From the interpretation of the resnIts of a
matrix of fluidization tests, it was fonnd that the algorithm proposed conId effectively model the expansion of a
fluidized bed of ion exchange resin, independently of the dimensions ofthe accomodatiog receptical.
Finally. it was shown that the change in the fluidization characteristics of the selected resin, between its chloride and
metal cyanide states, could clearly be modelled by the technique referred to above.
The removal/retrieval ofcyanide and metal cyanide complexes has been studiedby researches for many years, leading
to the establishment of a variety of patents. The mechanisms used by these patents vary from purely chemical
techniques to those using ion exchange Iesins.
In this thesis, ,the feasIbility ofthe recovery ofmetal cyanide complexes by using a strong base macroreticular resin, in
a fluidized bed configuration, has been investigated. The resin in question is presently used in the sugar indnstry
where its main application is the recovery oflarge organic molecules similar in nature to metal cyanides.
The selected resin was contacted with synthetic solntions of various metal cyanide complexes. for the purposes of
evaluating performance in the adsorption th..."feOf. It was found that polyvalent metal cyanide molecules were adsOlbed
efficiently, while divalent metal cyanide molecules were adsorbed satisfactorily.
The loaded resin was also evalnated for the ease with which the metal cyanides conId be removed. It was discovered
that a brine solntion ofpH 7, conId effectively remove all metal cyanide complexes. This test-work was of particular
importance as it is well !moon that the removal ofmetal cyanides from strong base metals is not easily achieved.
To distingnish the fluidization characteristics of the selected resin (or any resin for that matter), a method of
modelling the expansion of a flnidized resin bed was proposed, that takes into account the diflicnIties associated with
the byclrod:)nantic charncteristics of a macroporous resin of this nature. The technique is based on the Serial Afadel
which is a discretised application of the Z3ki and Richardson equation. From the interpretation of the resnIts of a
matrix of fluidization tests, it was fonnd that the algorithm proposed conId effectively model the expansion of a
fluidized bed of ion exchange resin, independently of the dimensions ofthe accomodatiog receptical.
Finally. it was shown that the change in the fluidization characteristics of the selected resin, between its chloride and
metal cyanide states, could clearly be modelled by the technique referred to above.
Additional information
Thesis (MTech(Chemical engineering))--Cape Technikon, Cape Town,1996
Subjects
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