Continuous Countercurrent Ion Exchange ( CCIX) used in Hydrometallurgy - The influence of Iron
Filip Rochette
General Manager
Herentals, Belgium
(author: filip.rochette@puritech.be )
Yvan De Busscher
Technical Director
Herentals, Belgium
Yvan.de.busscher@puritech.be
KEYWORDS
Hydrometallurgy; Ion Exchange; Resin; Metal recovery
INTRODUCTION
Extraction of minerals can be achieved by a variety of technologies, one of them is Ion Exchange.
There are several Ion Exchange configurations and mechanical set-ups available, only one technology will
provide a better process performance and flexibility compared to the other.
The multiple column CCIX = Continuous Countercurrent Ion Exchange technology provides the highest
form of process flexibility with also the highest mineral recovery feasible with ion exchange.
In comparison with a fixed bed system, the PuriTech CCIX system offers the benefits of the continuous
counter-current contact mode. This way the resin capacity is largely exploited leading to reduction in resin
inventory and, at the same time, in chemicals and water consumption, and product dilution.
ION EXCHANGE
Ion Exchange has been used for many decades for the purification of water, chemical processes,
food ingredients and for the recovery of valuable elements such as metals.
Before explaining the CCIX ( Continuous Countercurrent Ion Exchange) process behind metal
recovery, a quick introduction to some keywords used in this paper and the technology behind it:
Continuous: All process zones which are used in an ion exchange process: adsorption +
displacement + rinse + elution all work at the same time, CCIX systems can produce continuous 24h per
day, 7 days a week.
Countercurrent: The process flows are moving in one direction while the ion exchange resin is
virtually moving in another direction. So, the process flow and the resin flow are opposite from each other.
Ion Exchange: is an exchange of ions between two electrolytes or between an
electrolyte solution and a complex. In most cases the term is used to denote the processes of purification,
separation, and decontamination of aqueous and other ion-containing solutions with
solid polymeric or mineralic 'ion exchangers'.
Typical ion exchangers are ion exchange resins (functionalized porous
or gel polymer), zeolites, montmorillonite, clay, and soil humus. Ion exchangers are either cation
exchangers that exchange positively charged ions (cations) or anion exchangers that exchange negatively
charged ions (anions).
Photo 1: Ion Exchange resin
In the ion exchange column during the adsorption or regeneration phase, one ion is exchange with another
ion, the area / zone where this exchanges happens is called the Mass Transfer Zone.
For any set of operating conditions the Mass Transfer Zone has a characteristic length = Mass Transfer
Zone Length ( MTZL ). The MTZL can be expressed in duration, column length, or volume, but is the
measure of the quantity of resin in the system that is doing "work" at any given moment in the process.
The MTZL is influenced by the average resin bead size, the feed flow rate, resin bed depth and operating
temperature.
Photo 2: MTZL visualisation in a resin bed
The objective of continuous ion exchange processing is to eliminate all resin volume from the process
equipment that is not within a Mass Transfer Zone. The more resin is in an active state, the better the
overall performance of the ion exchanger.
In most commercial ion exchange processes for the recovery of metals, CCIX can eliminate as much as 20
to 80 % of the ion exchange resin inventory.
Consumptions of water and chemicals are also typically brought down around 40% or more.
CCIX also allows to utilize different process conditions or configurations in the same ion exchanger and
allows the development of more complex process configurations.
METAL SEPARATION OR RECOVERY BY ION EXCHANGE
For each type of resin, the selectivity or affinity towards a particular metal depends on the resin bead
structure; ionic charge; the basic process conditions such as pH, concentrations of other competing metals
in solution.
Ions with a higher charge have a higher affinity for the functional group of a given ion exchange resin.
By changing the pH in the ion exchange process phase, the selectivity of the resin can be changed. By
doing this, a split elution , extraction of separate metals can become achieved and / or the effect of other
competing metals can become reduced.
There are different types of resins available in the market which have a specific affinity for several metals.
The following resins are commonly used in Hydrometallurgy applications:
Carboxylic resins:
Cu2+ > Pb2+ > Zn2+ > Cd2+ > Ni2+ > Ca2+
Phosphonic resins:
Cu2+ > Zn2+ > Cd2+ > Mn2+ > Co2+ > Ni2+ > Ca2+
Aminophosphonic resins H+ > Fe3+ > Pb2+ > Cu2+ > Zn2+, Al3+ > Mg2+ ≥ Ca2+ ≥ Cd2+ > Ni2+
(at acidic pH):
≥ Co2+ > Na+
Iminodiacetic resins:
Cr3+ > In3+ > Fe3+ > Al3+ > Hg2+ > UO2+ > Cu2+ > Pb2+ > Ni2+ > Cd2+ > Zn2+ >
Co2+ > Fe2+ > Mn2+ > Ca2+ > Mg2+
Strong acid resins:
Fe3+ > Ca2+ > Fe2+ > Cu2+ > Mg2+ > K+ > NH4+ > H+
Strong base resins:
SO42- > CO32- > NO3-> Cl- > HCO3- > F- > OH-
Bis-picolylamine resins: Cu2+ > Ni2+ > Fe3+ > Zn2+ > Co2+ > Cd2+ > Fe2+ > Mn2+
For example, the DOW resin XUS43578 is commonly used for the recovery of Copper or is also widely
used for the separation of Nickel from a Cobalt solution. The selectivity chart for this DOW resin
XUS43578 is given below:
Photo 3: XUS43578 ions selectivity ( DOW )
The diagram above indicates that at a pH of < 1, this bis-picolylamine resin will preferably load the Copper,
secondly Nickel and eventually the Cobalt. The higher the pH, the more tendency towards Ferric
precipitation and resin loading, and also an increased potential of resin fouling.
Ferrous iron ( Fe2+ ) doesn’t load well on the resin below a pH of 2. We can take advantage of this by
reducing the iron that has been loaded on the resin. If we apply 1% sodium sulfite that has been pH
adjusted to 2, we could scrub the iron from the resin and leaving the Nickel or Cobalt behind on the resin.
In a second step, the Nickel or Cobalt can become extracted from the resin.
By changing the pH at the elution zone, the affinity is effected and the release of the metal could be
“controlled” by the CCIX technology.
CCIX SEPARATION TECHNOLOGY
As indicated above, each specific resin has its specific preference & affinity for a specific element.
By using multiple ion exchange beds / columns, the Continuous Countercurrent Ion Exchange technology
allows to play around with different process configurations and conditions. This is shown in the figure 1
where the use of a split elution is applied. The pH is changed in between two elution fazes and by doing
this, the release of each specific metal is dictated to the resin.
A process configuration with a split elution is shown below:
Figure 1: CCIX process schematic with Split Elution
Dependable on the value of the metal which is preferred, a multi pass adsorption could be applied to allow
the removal / recovery of this metal as maximum as possible. A triple adsorption pass will achieve this
goal. The process flow will pass first the resin which has been loaded already 2 time. After this first
adsorption, the process flow will pass resin which is more active in a second pass. Eventually the process
flow will pass the fresh almost virgin resin to remove all remaining elements which have not been removed
by the 2 earlier passes.
A possible process configuration with triple pass adsorption possible with PuriTech’s CCIX technology is
shown below:
Figure 2: CCIX process schematic with Triple pass Adsorption zone.
ION-IXTM IN A COBALT PURIFICATION PROCESS
By means of a continuous counter-current ion exchange pilot ( = test installation), tests on the client's
process liquor can be done. This gives the opportunity to develop the CCIX process specifically for the
process of the customer and to come to the highest possible performance of the ion exchanger.
Photo 4: A pilot installation for Cobalt purification
The obtained pilot data will be used to do the basic design of the industrial plant. The mass balance and
flow diagram - PFD will be developed during the pilot trials. Up-scaling of this pilot data allows the
customer to estimate the CAPEX and OPEX for the future industrial installation and provides a handy tool
to verify the financial feasibility of the project.
Afterwards, in collaboration with the client, the P&ID with initial plant lay-out are developed. When
equipment lay-out & sizing is finalised, the construction drawings for vessels; steel structure; piping and
electrical drawings are engineered for the local suppliers & contractors.
Photo 5: 3-Dimensional design of a Cobalt purification plant
A detailed engineering package is then used to build the plant with local contractors.
Photo 6: Operational ION-IXTM Cobalt purification plant
The pilot installation for Cobalt purification was treating a solution with a capacity of 20 – 30 L/h. The
industrial installation has a capacity of 200 m³/h.
Analysis of plant operating data shows that the facility was able to meet its performance guarantees
developed during pilot trials.
CONCLUSIONS
Continuous countercurrent ion exchange is a versatile ion exchange technology that is able to
effectively remove specific metals from a liquor.
PuriTech’s ION-IXTM is an ingenious mechanical device that allows too not only improve liquid–resin
contact efficiency, but also leads to a reduction in plant operating costs and capital expenditure. It provides
a wide range of process flexibility to develop high performance ion exchange applications.
We have shown above that the ION-IXTM system can easily be tailored to a number of applications in
several industries by using different types of resins and flow configurations, and chemicals in the elution
Zone including salt, acid and alkali.
ION-IXTM is a patented and innovative continuous ion-exchange process that can be applied to these
applications as well as a number of other separation requirements in various industries.
REFERENCES
- technical datasheet from DOW resin XUS43578