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The removal of heavy metals from dilute aqueous streams by the use of ion exchange resins
Author(s)
Dietrich, Theo Henry
Date Issued
1998
Type
Thesis
Publisher
Cape Technikon
Abstract
Ion exchange resins are widely used to remove or concentrate heavy metals
from aqueous solutions or slurries.This thesis attempts to properly evaluate
the interaction between ion exchange resins and heavy metals at trace metal
concentrations.The durability of the resins and their effectiveness in real
slurries were also investigated.
In this study, a chelating resin, as well as a cation, and anion exchange resin
was contacted with aqueous solutions of heavy metals in both free and
complexed form. Zinc, nickel and copper cyanide complexes were adsorbed
onto the anion exchange resin, while the chelating and cation exchange resins
were contacted with zinc and nickel nitrates, and cupric sulphate. All the tests
were conducted in batch stirred tank reactors.
All the metal cyanide complexes behaved in a similar manner when contacted
with the anion exchange resins. These tests were p~rf0nned under variations
in temperature, stirring speed, pH., ionic strength and . initial metal
90E~entrations. Fitting of a dual resistance model to the profiles for thetlptllk:e"
of the complexes, show that both film diffusion and intraparticle diffusion
rates were improved with an increase in temperature, and that film diffusion
rates improved with an increase in stirring speed. A high ionic strength
negatively affected equilibrium loading as well as diffusional rates.It was
found that at these low concentrations, the diffusional rates improves with a
decrease in the external metal concentration.
A comparative study involving the chelating and cation·exchange resins were
performed, during which the resins were contacted with the metals in free
fonn. It was found that at high metal concentrations, the chelating resin
induced a rate limiting effect, but at trace concentrations, this effect is
virtually negated. Whereas the cation exchange resin exhibited little
selectivity in adsorbing the metals, it was found that the chelating resin
prefers the metals in the eu > Ni > Zn. The chelating resin proved to be no
less durable then the cation exchange resin, and both slightly lost their ability
to adsorb the metal cations as a result of the effects of an inert coarse sand
slurry.Tests performed with a real ore leachate, showed the cation exchange
resin to be efficient at a low pH , but also relatively non selective, since the
adsorption of copper from the leachate was greatly reduced due to the
presence of other heavy metals.
from aqueous solutions or slurries.This thesis attempts to properly evaluate
the interaction between ion exchange resins and heavy metals at trace metal
concentrations.The durability of the resins and their effectiveness in real
slurries were also investigated.
In this study, a chelating resin, as well as a cation, and anion exchange resin
was contacted with aqueous solutions of heavy metals in both free and
complexed form. Zinc, nickel and copper cyanide complexes were adsorbed
onto the anion exchange resin, while the chelating and cation exchange resins
were contacted with zinc and nickel nitrates, and cupric sulphate. All the tests
were conducted in batch stirred tank reactors.
All the metal cyanide complexes behaved in a similar manner when contacted
with the anion exchange resins. These tests were p~rf0nned under variations
in temperature, stirring speed, pH., ionic strength and . initial metal
90E~entrations. Fitting of a dual resistance model to the profiles for thetlptllk:e"
of the complexes, show that both film diffusion and intraparticle diffusion
rates were improved with an increase in temperature, and that film diffusion
rates improved with an increase in stirring speed. A high ionic strength
negatively affected equilibrium loading as well as diffusional rates.It was
found that at these low concentrations, the diffusional rates improves with a
decrease in the external metal concentration.
A comparative study involving the chelating and cation·exchange resins were
performed, during which the resins were contacted with the metals in free
fonn. It was found that at high metal concentrations, the chelating resin
induced a rate limiting effect, but at trace concentrations, this effect is
virtually negated. Whereas the cation exchange resin exhibited little
selectivity in adsorbing the metals, it was found that the chelating resin
prefers the metals in the eu > Ni > Zn. The chelating resin proved to be no
less durable then the cation exchange resin, and both slightly lost their ability
to adsorb the metal cations as a result of the effects of an inert coarse sand
slurry.Tests performed with a real ore leachate, showed the cation exchange
resin to be efficient at a low pH , but also relatively non selective, since the
adsorption of copper from the leachate was greatly reduced due to the
presence of other heavy metals.
Additional information
Thesis (MTech (Chemical Engineering)--Cape Technikon, Cape Town, 1998
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