WO2014170863A1

WO2014170863A1 - Ion exchange

Info

Publication number: WO2014170863A1
Application number: PCT/IB2014/060809
Authority: WO
Inventors: Gordon John Rossiter
Original assignee: Ionex Separations Inc.; COCHRANE, David Hylton
Priority date: 2013-04-18
Filing date: 2014-04-17
Publication date: 2014-10-23

Abstract

This invention relates to a process for treating a resin that has been in contact with pregnant leach solution (PLS) containing ionic metal species such as uranium, copper, cobalt, nickel, gold, chrome, PGM's and Rare Earth Metals, and which is loaded with the ionic metal species in an ion exchange loading system (10). Loaded resin (12) from the ion exchange loading system (10) is subjected to a multi-vessel continuous counter- current ion exchange (CCIX) system (34) to remove the metal species from the resin and obtain a regenerated resin essentially free of the metai species, which may be recycled to an ion exchange loading system where it is placed again in contact with the PLS.

Description

ION EXCHANGE

BACKGROUND TO THE INVENTION

Ion exchange has had limited success in hydrometallurgy for a number of reasons, one of which is the inability of the ion exchange (IX) systems to cope with solids in the process liquors. On a hydrometallurgy plant, a typical process stream requiring an extraction or purification process will most likely contain suspended solids (SS). The problem experienced by IX systems is that the IX resin acts as a very efficient filtration media, and if the feed stream passing through an ion exchange system contains a significant amount of suspended solids (typically greater than 20ppm) then the top of the bed gets plugged with solids, causing high pressure drops and a decrease in throughput. This would be typical of a PLS (pregnant leach solution) found on a hydrometallurgical plant - be it uranium, copper, cobalt or others.

This has in the past prevented the use of IX, and solvent extraction has been the technology of choice as systems have been developed to deal with the crud formed.as a result of solids entrainment.

DEVELOPMENT OF COUNTER-CURRENT ION EXCHANGE

A conventional ion exchange system consists of a number of pressure vessels filled with ion exchange resin. Feed is passed through the ion exchange vessel in order to load one or more ionic species onto the resin, in order to purify the stream (if the resin adsorbs the waste product) or to extract the species from the stream. A typical ion exchange plant would consist of two or three fixed bed vessels, with one or two vessels in adsorption (loading of ionic species onto the resin), and one vessel would be in elution (stripping of the ionic species of the resin with a high concentration acid or base). Conventionai ion exchange systems are relatively inefficient in terms of resin usage, especially if the ionic loading in the feed stream is quite high. Due to the high loading rates, the amount of resin required to ensure that the vessel loading time is not too short, is high. In addition to this, the elution efficiencies of conventional fixed bed vessels is also low, typically 3- 5 bed volumes (BV's) of eluent is required to elute 1 BV of resin.

For this reason the concept of continuous counter-current (CCIX) ion exchange systems was born. The CCIX systems typically use a net volume between 0.6 to 0.9 BV of eluent to elute 1 BV of resin. In CC!X systems, the ion exchange system consists of a much larger number of small vessels (typically 12-30), connected to the process fluids via a single multiport distribution valve. In some equipment systems, the vessels are mounted on a rotating carousel. In other systems the vessels are stationary.

These CC!X systems are markedly more efficient than conventional fixed bed systems, resulting in-significant reductions (in specific duties) in resin inventory, wash water and elution chemical usages. This translates to higher concentrations of the recovered species, and lower neutralization costs if further downstream process requires neutralisation of excess eluent in the e!uate.

However, CCiX systems are still prone to resin bed fouling from feed streams containing suspended solids. This phenomenon affects both conventional and CCIX systems.

SOLIDS HANDLING ION EXCHANGE CONTACTORS

A number of alternative ion exchange contactors have been developed to overcome the problem of suspended solids. These include agitated resin- in-pulp (RIP) systems together with atmospheric agitated loading and elution tank systems such as that installed at the Kayelekera Uranium Mine in Malawi and the NIMCIX ton exchange system developed by Mintek in South Africa. The NIMCIX system consists of vertical vessels, one for loading and one for elution.

The agitated RIP systems consist of a number of atmospheric tanks, linked together in a cascade type arrangement. Each tank is equipped with a screen to prevent the resin moving from one tank to another. Two different configurations exist - one where the resin remains in a specific tank and the slurry is rotated in a counter current carousel type operation, and the other where the resin is pumped/educted to the "upstream" tank to effect the counter current flow of resin and slurry.

The NIMCIX system consists of an atmospheric vessel, with a number (10- 20) of perforated trays. The feed solution (in the case of the loading vessel) and eluent (in the case of the elution vessel) flows upwards in the vessel, and the resin cascades downwards from tray to tray in a manipulated (controlled) fashion, and in this way brings about the counter- current contact between fluid and resin.

While these systems adequately address the problem of handling suspended solids in the feed streams, the eiution systems are inefficient and inflexible.

SUMMARY OF THE INVENTION

This invention relates to a process for treating a resin that has been in contact with pregnant leach solution (PLS) containing ionic metal species such as uranium, copper, cobalt, nickel, gold, chrome, PGM's (platinum group metals - ruthenium, rhodium, palladium, osmium, iridium, and platinum. ) and Rare Earth Metals, and which is loaded with the ionic metal species in an ion exchange loading system; the process including the steps of: receiving the loaded resin from the ion exchange loading system; and subjecting the loaded resin to a multi-vessel continuous counter-current ion exchange (CCiX) system comprising a plurality of separate packed bed ion exchange vessels arranged for elution, purification and regeneration of the resin to remove the metal species from the resin and obtain a regenerated resin essentially free of the metal species, which may be recycled to an ion exchange loading system where it is placed again in contact with the PLS.

Preferably, loaded resin from the ion exchange loading system is washed to remove suspended solids from the loaded resin.

The suspended solids typically comprise gangue and tailings waste, mainly silica, less than 500 μιη, typically from 2 - 500 pm, usually 50 - 200 μηη in size.

The resin is of suitable functionality to selectively adsorb the metal species of interest; e.g., strong and weak base resins for uranium; chelating resins for copper. The resin may be a strongly basic anion exchange resin in the form of beads with a particle size of 500 - 1500 μηι.

The ion exchange loading system is preferably a solids tolerant ion exchange loading system such as: a RIP (Resin in Pulp) system using an agitated system consisting of a number of atmospheric tanks, linked together in a cascade type arrangement with each tank equipped with a screen to prevent the resin moving from one tank to another; or a "NI CIX" or "Himmsley" system consisting of an atmospheric vessel, with a number (10-20) of perforated trays, the feed solution (in the case of the loading vessel) and eluent (in the case of the elution vessel) flows upwards in the vessel, and the resin cascades downwards from tray to tray in a manipulated (controlled) fashion, and in this way brings about the counter-current contact between fluid and resin.

The loading and washing steps may take place sequentially with the continuous counter-current ion exchange (CCIX) elution and regeneration system; or load and wash at a remote leach field and then transport loaded resin to a site where the continuous counter-current ion exchange (CCIX) elution and regeneration system is situated.

The vessels in the continuous counter-current ton exchange (CCIX) elution and regeneration system are identical in that they are adapted to hold and treat the same amount of resin. Volume of resin per vessel will depend upon the plant size, for example, the vessels may have a volume of 0.15 to 4 m³, typically from 1 to 3 m³

Preferably, loaded resin is passed through a measuring apparatus, and a measured quantity of loaded resin, corresponding to the volume of the vessels in the continuous counter-current ion exchange (CCIX) elution and regeneration system, is loaded in to a first vessel in the system.

The multi-vessel continuous counter-current ion exchange (CCIX) elution and regeneration system may comprise 6-30, typically 12-20 vessels. The optimum number of vessels for each process depend upon the specific needs of each process; e.g., some processes require a resin conditioning step after the elution and rinse; other steps that required in some processes employ extended pre-elution stages to remove impurities and/or pre-load the resin; in some cases the resin is treated for removal of species that can foul the performance.

A resin vessel starts its cycle at the position in which it is charged with loaded resin; its cycle finishes at the position in which the regenerated resin is removed - either hydraulically or as a complete vessel. The cycle comprises stepping through ail the zones and the stages within the zones. The time a vessel rests in one position is called the step time and in a 20- vessel system there are 20 steps of equal time length. If a resin vessel starts in position 20 and finishes in position 1 then fluids flow direction will be opposite to achieve the counter-current effect. The word position refers to the multiport valve position; a valve that services 20 vessels will have exactly 20 positions.

The vessels may be mounted on a rotating carousel; or the vessels may be stationary.

In the case where the vessels are stationary, the continuous counter- current ion exchange (CCiX) elution and regeneration system comprises a multiport fluid distribution valve for introducing process fluids in to the vessels. The loaded resin may be introduced via the multiport fluid distribution valve, a separate manifold system, or as a physical vessel full of resin.

The continuous counter-current ion exchange (CCIX) elution and regeneration system may have an elution section that has 2-8, preferably 3- 5 vessels. Consider the elution zone occupying positions 1 to 5 on the muitiport valve then, fresh resin (inside a vessel) for elution is introduced at position 5, and fresh eluent introduced into the resin vessel at position 1 - the counter-current arrangement. After a step time has elapsed, a fresh resin vessel for elution is introduced at position 1 , and the previous vessel in position 1 moves to position 2.

The vessels in the mu!ti-vessel continuous counter-current (CC!X) ion exchange elution system are preferably subjected to a series of process steps as they go through the complete elution and regeneration process which can include some or all of the following stages:

A1 Resin charging. Typically 1 vessel.

A1 Resin vessel fill and resin bed backwash. Typically 1-2 vessels.

A2 Resin scrub. Typically 2-4 vessels. A typical scrub liquor comprises 2-5% dissolved S0₂ or dilute sulphuric acid.

A3 Resin pre-elution. Typically 3-5 vessels.

A4 Resin elution - in stages. Typically 4-8 vessels. A typical eluent comprises sulphuric acid at strengths from 80 to 250 /L

A5 Resin rinse. Typically 3-4 vessels.

A5a Resin Cleaning. Typically 2-3 vessels.

A6 Resin conditioning. Typically 1-2 vessels.

A7 Resin unloading. Typically 1-2 vessels.

The above steps are preferably carried out simultaneously.

Preferably, rinse effluents for example from stage A5 are initially sent to the elution zone (A4) to recover strong eluent and subsequently sent to the eluent makeup to be used for eluent dilution in step. This is an example of how optimization can be applied to recover fluids that cross the boundaries between stages. Displacements of fluids back to their zone of origin a major contributor to minimizing new water and new chemical usage as well as minimizing product dilutions.

BRIEF DESCRIPTION OF THE DRAWING

Figure 1 is a flow diagram of a process according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The basis of the invention is that the new process will utilise solids tolerant ion exchange loading system such as one of the agitated or fluidized bed solids handling systems for loading (RIP, N!MCIX or similar), but will utilise the multi-vessel CCIX system for elution and regeneration of the resin.

In the prior-art multi-vessel CCIX process the resin has remained in the vessels during treatment and only removed from the vessels if the functionality of the resin has decreased to such an extent that it has to be replaced.

To use the CCIX for elution, purification and regeneration only, the requirement of the invention is that resin will have to be transported from a resin loading system to the CCIX elution and regeneration system. By utilising a system that can accommodate solids for loading, and a highly efficient CC1X system for eiution, the total ion exchange package creates a system that is significantly more efficient than any of the existing systems on the market for dirty feed PLS (Pregnant Liquor Solution) streams.

In a preferred embodiment, the system of the present invention uses the CCIX process that utilises a plurality of separate vessels (typically 12-30), where the process fluids are introduced through a multiport fluid distribution valve. Multiport fluid distribution va!ves that are suitable for use in the process of the present invention are described in US 3,192,954, US 4625763 and US 5478475, the entire contents of which are incorporated herein by reference. Preferred multiport fluid distribution valves are described in WO2004/029490 and US2006/0124177, the entire contents of which are incorporated herein by reference. These documents disclose distribution valves that are arranged to receive fluid/s and distribute these fiuid/s via a plurality of discharge ports.

US 3,192,954 describes a rotary distribution valve comprising a cylindrical valve casing with a plurality of ports extending through the casing. A cylindrical rod-shaped plug is rotatable within the casing. Circular grooves are located in the casing or in the plug. A conduit communicates with each of the circular grooves and extends through the wall of the casing to the exterior of the casing. Recesses, corresponding in number with the circular grooves, are circumferentiaily spaced around the plug. The ports are spaced around the periphery of the casing so that each of the ports is in communication with each of the recesses at some point in the rotation of the plug. Passageways, corresponding in number with the circular grooves, extend through the plug. Each passageway continuously connects one of the recesses in the plug with one of the circular grooves. US 4625763 describes a disc-axial multiport valve which comprises a fixed stator assembly to which process fluid conduits are connected. A rotor is rotatably mounted within the fixed stator. A fixed distributor is connected to the fixed stator. Process chambers are connected to the fixed distributor. The process chambers are sequentially supplied with process fluid as the rotor is rotated within the fixed stator. US 5478475 describes a fluid distribution apparatus consisting of an upper fluid distributor and a lower fluid distributor with a plurality of processing chambers held and fixed between the upper and lower fluid distributors. WO2004/029490 describes a rotary distribution apparatus including a fixed inner distribution member with an inner conduit zone; a rotatable outer distribution member rotatable about the fixed inner distribution member; a plurality of fluid distribution chambers located between the fixed inner distribution member and the rotatable outer distribution member; each fluid distribution chamber having a fixed port in the fixed inner distribution member to which a fixed supply or return conduit for a fluid can in use be connected, and at least one distribution port in the rotatable outer distribution member; at least one indexing arrangement including a rotatable indexing member and a fixed indexing member; a plurality of passageways extending through each of the rotatable and fixed indexing members, the plurality of passageways each having indexing ports and connection ports with the indexing ports being provided in an indexing surface; and the connection ports of the rotatable indexing member in use being connected to the distribution ports of the distribution chambers by connecting conduits, and the connection ports of the fixed indexing member in use being connected to process chambers by fixed conduits; so that, in use, when the rotatable outer distribution member, the rotatable indexing member and the connecting conduits are rotated, fluid fed to a fluid distribution chamber is sequentially fed to the process chambers and returned from the process chambers to other fluid distribution chambers as the indexing ports of the rotatable indexing member index relative to the indexing ports of the fixed indexing member.

The advantages of running a muiti-vesse! counter-current elution CCIX elution scheme for NIMCIX / RIP type solids tolerant loading systems include the following: ) The use of packed beds is inherently more efficient compared to the present practice of fluidized or agitated beds.

) No resin movement - Once resin is installed into the CCIX system it does not undergo any movement as with prior systems. This significantly reduces resin breakage and resin loss through attrition.) More concentrated eiuate - up to three/four times conventional eluate concentration than that produced by the present art/systems. Actual eluate flow to product can be in the range 0.6 - 0.9 BV. This will allow either elimination of the SX circuit (used to concentrate and purify eluate) or a reduction in the size of the SX circuit. More concentrated eluate comes from the fact that the equivalent of 1 BV of eluent is used compared to 5BV in the prior art (NIMCIX/RIP) hence giving higher concentration eiuate (product).

) A CCIX elution and regeneration section as proposed wilt typically utilize less than 1 BV of eluent, the agitated and NIMCIX systems require 3-5 BV's of eluent. This results in significantly lower (sometimes an order of magnitude lower) concentration of the recovered metal in the eluate, and also results in massive amounts of excess eluent chemicals (typically sulphuric acid) in a number of hydromet processes. In certain cases it is claimed that the reduction of wasted acid will be in the region of 90%.

) Downstream of elution is the metal recovery circuit and the purer and more concentrated the eluate the higher the recovery yield, the smaller the recovery plant size and the bleed and recycle streams are minimized.

) More efficient elution - The inherent counter current multi-stage operation allows for 99% removal of the metal species from the resin thus returning the resin to the loading system with more loading capacity.

) The multi vessels elution allows eiuate to be recycled for further concentration of eluate (product) ) Purer eiuate - based on running an impurity scrub prior to eiution - system can run reducing and mild scrubbing schemes; removes Fe, P, V etc from U loaded resins. This may allow elimination of an SX or precipitation circuit to remove impurities.

) Eiuate contains minimum excess eluent; the multiple stage eiution in counter current produces an eiuate product which corresponds to the maximum specie concentration achieved in a fixed bed eiution operation; this maximum concentration point is the point at which the CiX system harvests the e!uate; this maximum concentration of the value metal also corresponds to a minimum excess eluent condition; consequently, less neutralization is required in the downstream product recovery sections. Reduced operating cost is achieved by eliminating or reducing the amount of neutralization chemicals that otherwise are required to deal with excess eluant.0) More efficient consumption of e!uent (reduced chemical consumption) - direct benefit of continuous counter-current contacting using multiple stages. Reduced operating cost as less eiution chemicals used.

1) Less water consumption overall - in the C!X rinse circuits a normal consumption of water is between 0.9-1.1 BV where Bv = resin flow rate; extra water used for concentrated eluent dilution can also be passed through the multi-stage rinse zone and provide even higher rinse efficiency and process security; the rinse effluent then is diverted first to send recovered eluent into the eiution zone and secondly as, double use of rinse water, is diverted externally to be used to dilute strong eluent (acid or base). This saves water and reduces waste effluent flows

2) Efficient resin cleaning zone; can use controlled additions with fast recycle flows under pH control. Resin cleaning is used in the uranium recovery from acid leachates in which a slow accumulation of silica can occur on the resin surfaces which eventually impedes the access to the resin porous structure and prematurely degrades the resin performance. Regular cleaning and in a CIX manner is more efficient in the use of chemical (NaOH) and water.

13) Efficient resin re-conditioning zone; as above and often we use barren as a conditioning fluid. This reduces the movement of resin and allows more efficient use of reconditioning chemicals.. In some processes the resin has been put in contact with alkali and it must then be acidified with before returning to contact with pregnant ieach solution where a "shock" contact could cause metals to precipitate undesirably.

14) All process steps are completed simuitaneousiy compared to the prior art where the process steps are completed sequentially. If practised with the present art this would require significant solution management with the consequence of significant cost implications.

This invention has a number of advantages over the U-TUBE type of CCIX:

1) Eluent and other process fluid streams can be removed and manipulated between individual vessels. This manipulation can be in terms of flow, chemical composition, temperature, redox potential, pH. This manipulation allows increased process efficiency. By preconditioning the pre-elution feed flow the resin can be further loaded to a higher level of metal content and thereby "crowd out" less selectively adsorbed impurity components.

2) The elution process is continuous and does not have to be interrupted.

3) Entrained water can be rejected by means of entrainment rejection or fluid displacement techniques via the configuration of a number (typically three) of vessels for this purpose.

4) in certain elution sequences BOTH strong acids and strong bases are employed; e.g., acid elution of uranium anion resin followed by caustic cleaning for silica removal. Because the CIX elution system proposed here utilizes discrete vessels these chemicals as can be safely kept apart by using rinse steps between their application points. This would not be easily done in NIMCiX and UTUBE type systems.

With reference to Figure 1 , the typical steps in a conceptual URANIUM (U) elution and regeneration resin scheme consist of the following:

1) A pregnant leach solution containing suspended solids (with an average size of 50 to 200 prn), from for example a heap, in-situ or agitated leach, is supplied to a solids tolerant ion exchange loading system 10 (in this case the RIP system).

Suitable resins in the RIP system include:

• AMBERSEP™ 920UHC S04 (available from Dow) which is a strongly basic, macroreticular anion exchange resin. AMBERSEP 920U HCS04 has been specially developed for the extraction of uranium from ore, both for insitu leaching and RIP processes. The resin is in the form of opaque beads and has a harmonic mean size of 0.750 - 0.950 mm.

• AMBERSEP 400 S04 (available from Rohm and Haas) which is a gel type, strongly basic, type 1 , Polystyrene divinyibenzene copolymer, anion exchange resin with superior performance for uranium recovery, its excellent selectivity for the uranyl sulphate ion over other anions, its high operating capacity, excellent mechanical and physical stability and its resistance to fouling make it the resin of choice. AMBERSEP 400 S04 is well suited for recovery of uranium from sulphuric acid leach systems using fixed beds, in situ leaching, fluidized beds or Resin In Pulp (RIP) applications. The resin is in the form of transluscent beads and has a harmonic mean size of 0.600 - 0.750 mm.

• Purolite A500/2788 which is a macroporous-type strong base, polystyrene crosslinked with divinylbenzene, anion exchange resin efficient for extraction of uranium complexes in in-situ (ISL), batch or heap leaching and Resin-in-Pulp (RIP) processes. The resin is in the form of beads and has a particle size range of 800 - 1300 pm.

• Purolite PFA 460/4783

) A barren solution is recycled to the leach.

) RIP loaded resin containing solids is sent to a washer and washed with water. Dirt water containing suspended solids is removed from the washer and a washed loaded resin 12 is obtained.

) The washed loaded resin 12 from a leach/resin tolerant ion exchange loading system 10 is delivered to a measuring vessel 14.) A measured quantity of resin 16 is taken from the measuring vessel 14, the resin 16 is sent to a multi-vessel counter-current elution CCiX system 34, which in this case is an lonex Separations IXSEP System which has stationary vessels, !n a typical example, the measured quantity of resin is 1 to 3 m³ with the vessels being adapted to receive this amount of resin.

A1 Resin charging into the CCIX system - 1-2 distribution ports a. Transfer of measured resin volume into a vessel via the multiport distributor or a separate independent manifold system.

A2 Resin scrub zone- scrub liquor (20) if required for Fe, P, V etc. removal - 2-4 distribution ports/2-4 vessels

i. Vessels connected in series

ii. This may be a reductive scrub iii. This may be an acid scrub

iv. Effluent 22 from scrub is returned to the ieach loading circuit 10.

A typical scrub liquor comprises 2-5% dissolved SC½ for removing typical uranium ore impurities. Or, for Cu recovery one could use a cuprous reducing ion (1-2 g/L Cu^*1) in dilute (5% H₂S0₄) acid. b. A3 Pre-elution to remove impurities and pre-concentrate efuate 2 to 6 distribution ports/2-6 vessels

c. Vessels are connected in series

d. Feed Pre-elution can be Eluate 28 as feed.

e. This may be a modified Eluate 28; typically a pH adjustment f. Pre-elution effluent 26 is sent to the scrub section A2 or returned to leach/loading circuit 10. 4 Elution - 4-8 distribution ports/4-8 vessels

A typical eluent comprises sulphuric acid at strengths from 80 to 250 g/L. a. Can be split into multiple elution sections - often a total of 5-8 series connected vessels are employed in Elution. b. At each elution position feed into the vessel can be "sweetened" with extra eluent; staged addition of eluent to maintain driving force. The diagram shows and example of

c. Final section is where the elution peak value is harvested d. Some of the final eluate flow 28 is diverted to pre-elution A3; with optional adjustments to solution properties. e. In certain cases (e.g., Ni/Co separations) the eluent strength has to be controlled not to exceed a certain strength. So, some of the Eluate (28), which has been depleted in strength, can be recycled to a Mixing Device or Tank (23) and "sweetened" with fresh high concentration eluent (30) to its desired strength. The mixed eluent is then fed to a position in middle of the Elution stage, in this manner the selectively eluted component is recovered in a minimum amount of fresh water diluent.

f. Fresh high concentration eluent (30) is diluted to desired strength with Rinse effluent (32).

g. Fresh eluent (free of U) (34) is applied at the head of the Elution section (A4).

h. A typical e!uate comprises, in the case of uranium acid leaching, uranyl sulphate eluate containing > 20 g_U₃O_e/L in a solution of pH < 1.

AS Rinse -Rinse fluid (36) which may be process water or barren liquor from the loading system - 2-3 distribution ports/2-3 vessels a. Multi stage counter-current rinse which allows better wash efficiencies at reduced rinse fluid requirements, typically 1 BV.

b. Initial Rinse effluent (31) is basically displaced acid eluent carried over with the vessel moving from position 1 Elution into Rinse. This first Rinse effluent (31) is sent forward into the (to position 2) of the Elution (A4); this basically recycles strong eluent

c. Then Rinse effluent is diverted (32) to provide diluent for the fresh eluent; Fresh eluent is made up using strong acid (30) and diluent from Rinse (32)

d. In cases where the downstream recovery system returns a recycle stream to elution; e.g., a mother liquor from precipitation or crystallization or electro-winning, then the Rinse effluent or a portion thereof can be used as a bleed from the recovery circuit. In these cases barren adsorption liquor or raffinate is a suitable Rinse feed fluid - further economizing on fresh water usage.

A6 Resin Conditioning -Conditioning may be required to complete a siiica wash with a silica wash fluid (38) and/or a resin conditioning fluid (40) to convert the resin back to its original form for the loading system. - 3 distribution ports (includes water recovery) + 1 distribution port for acid conditioning

e. If silica washing is required then a 1-2 vessels connected in series or, a recirculation system is used with NaOH added at a controlled rate based on pH. A post conditioning rinse/displacement is used to return entrained caustic to the recirculation tank. f. If resin requires re-acidifying then similar arrangement for conditioning the resin into acid form is used. A water buffer between the acid and caustic zones is necessary. g. At times conditioning can be done with adsorption barren liquor.

A7 Resin Unloading from the CCIX system. 1-2 ports/1-2 vessels Transfer of conditioned resin 42 out of CCIX system (1-2 distribution ports) to ion exchange loading system clean resin storage (44). - this is done via the mu!tiport distributor valve or via a separate manifold and va!ve system. Clean resin 42 is returned to the ieach/load system 10 from the clean resin storage 44.

The eiution section (A4) usually has 3-5 vessels. Fresh resin arrives from A3 and moves into position 5 of the A4 Eiution stage. Fresh eluent is fed into a vessel in position 1 of the Eiution stage. Exhausted resin from position 1 moves out of the Eiution zone into the Rinse zone (A5) but carries with it a full vessel of fresh (strong) eluent. The first effluent from rinse (A5) is essentially entrained strong eluent and this flow (31) is sent directly forward to vessel in position 2 or 3 in the Elution zone. After a period of time the Rinse effluent (32) is diverted (basically slightly acidic water) to the eiuent make up tank (21) where a strong acid (e.g. 98% H2S04) is added to the water to make the eluent (e.g. 10% H2S04). This is a standard CCIX technique of using rinse effluent as the eluent diluent.

The total number of vessels (compartments) in the CCIX system will depend on the leachate that is being processed and the number of distribution ports allocated to each process operation.

The combination of a solids tolerant ion exchange resin loading system with an efficient CCIX resin regeneration and recovery system is important since:

The use of the CCIX system compared with other elution systems results in higher concentration products, purer products (less impurities), less contained eluent (Acid or Caustic),

The use of CCIX will reduce resin loss compared with other systems as resin is only loaded/unloaded once during the elution and regeneration process reducing resin breakage and abrasion

The use of the CCIX system reduces operating costs by reducing chemical usage, water usage, resin losses, downstream chemical usage and labour.

Use of the CCIX allows simultaneous processing of the resin though the different process steps of scrub, pre-elution, elution, rinse and conditioning without the need to move resin between each step.

The use of the CCIX system reduces capital costs by reducing the size of downstream recovery operations, improving the yield of the metal recovery steps and/or eliminating downstream concentration processes.

Claims

1. A process for treating a resin that has been in contact with pregnant leach solution (PLS) containing ionic metai species, and suspended solids, and which is loaded with the ionic metal species in an ion exchange loading system; the process including the steps of: receiving the loaded resin from the ion exchange loading system; and subjecting the loaded resin to a multi-vessel continuous counter-current ion exchange (CCIX) system comprising a plurality of separate packed bed ion exchange vessels arranged for elution, purification and regeneration of the resin to remove the metal species from the resin and obtain a regenerated resin essentially free of the metal species.

2. The process claimed in claim 1 , wherein the metal ionic species are one or more of uranium, copper, cobalt, nickel, gold, chrome, PGM's (platinum group metals) and Rare Earth Metals.

3. The process claimed in claim 1 , wherein loaded resin from the ion exchange loading system is washed to remove suspended solids from the loaded resin.

4. The process claimed in claim 1 , wherein the ion exchange loading system is adapted to tolerate solids.

5. The process as claimed in claim 4, wherein the solids tolerant ion exchange loading system is: a RiP (Resin in Pulp) system using an agitated system consisting of a number of atmospheric tanks, linked together in a cascade type arrangement with each tank equipped with a screen to prevent the resin moving from one tank to another; or a "NI CiX" or "Himms!ey" system consisting of an atmospheric vessel, with a number of perforated trays, wherein feed solution and eiuent flows upwards in the vessel, and the resin cascades downwards from tray to tray.

6. The process as claimed in claim 2, wherein the loading and washing steps take place sequentially with the continuous counter-current ion exchange (CCIX) elution and regeneration system.

7. The process as claimed in claims 2, wherein the loading and washing steps take place at a remote leach field and the loaded resin is transported to a site where the continuous counter-current ion exchange (CCIX) elution and regeneration system is situated.

8. The process as claimed in claim 1 , wherein the vessels in the continuous counter-current ion exchange (CCIX) elution and regeneration system are adapted to hold and treat the same amount of resin.

9. The process as claimed in claim 8, wherein the vessels have a volume of 0.15 to 4 m³.

10. The process as claimed in claim 9, wherein the vessels have a volume of 1 to 3 m³.

1 . The process as claimed in claim 1 , wherein the loaded resin is passed through a measuring apparatus, and a measured quantity of loaded resin, corresponding to the volume of the vessels in the continuous counter-current ion exchange (CC!X) elution and regeneration system, is loaded in to a first vessel in the system.

12. The process as claimed in claim 1 , wherein the multi-vessel continuous counter-current ion exchange (CCIX) elution and regeneration system comprises 6-30 vessels.

13. The process as claimed in claim 12, wherein the multi-vessel continuous counter-current ion exchange (CCIX) elution and regeneration system comprises 12-20 vessels.

14. The process as claimed in claim 1 , wherein the vessels are stationary, and the continuous counter-current ion exchange (CCIX) elution and regeneration system comprises a multiport fluid distribution valve for introducing process fluids in to the vessels.

15. The process as claimed in claim 1 wherein, the continuous counter- current ion exchange (CCIX) elution and regeneration system has an elution section that has 2-8 vessels.

16. The process as claimed in claim 15 wherein, the continuous counter-current ion exchange (CCiX) elution and regeneration system has an elution section that has 3-5 vessels.

17. The process as claimed in claim 1 , wherein the vessels in the multi- vessel continuous counter-current (CCIX) ion exchange elution system are subjected to a series of process steps as they go through the complete elution and regeneration process which can include some or all of the following stages which are carried out simultaneously:

A1 Resin Charging. A1 Resin Bed Backwash. A2 Resin Scrub.

A3 Resin Pre-elution.

A4 Resin Eiution - in stages. A5 Resin Rinse.

A5a Resin Cleaning.

A6 Resin Conditioning. A7 Resin Unloading.