BACKGROUND OF THE INVENTION

THIS invention relates to the treatment of a solution using an ion exchange resin.

The most common application in which ion exchange resins are used is the treatment of water (also referred to as the solution to be treated) for a variety of reasons such as demineralisation, purification and desalination to name a few. A conventional process for water treatment is a batch process, typically using fixed or fluidized bed reactors, whereby the water to be treated is first brought into contact with the resin by passing it through a bed of regenerated ion exchange resin in a reactor and the metal or the. mineral ions (hereinafter called the "target species") present in the water are collected (adsorbed) out of the water, and onto the resin, and exchanged for Hydrogen or similar ions that are present on the regenerated resin beads. The rate at which the water passes through the resin bed is calculated and controlled so as to allow the water to be in contact with the resin for sufficient time, for the Ion Exchange reaction to reach completion. The water that then exits on the other side of the resin bed is free of the target species Ions. This process continues until the resin is saturated (meaning it has reached a state where it can no longer adsorb any more target species Ions) then the water feed to the reactor is stopped. This is the end of the first stage in the typical batch process for water treatment. A typical second stage in the batch process, would be to backwash the resin bed with clean water. During this stage the resin bed is fluidized and any fine particles trapped between the resin beads are freed and washed out with the water. The next stage in a typical batch process would be to regenerate the resin beads. This is achieved by passing a "regeneration solution" through the resin bed. The make-up of the regeneration solution would be as per the resin manufacturer's specification. For example it may be a mild acid solution. The Ion Exchange reaction that occurs during the regeneration stage is opposite to the reaction during the first stage. During the regeneration stage, the target species ions that are present on the resin beads, will be absorbed into the regeneration solution and exchanged for Hydrogen or similar Ions present in the regeneration solution. The rate at which the regeneration solution passes through the resin bed is calculated and controlled so as to allow the resin beads to come into contact with sufficient regeneration solution for sufficient time for the Ion Exchange reaction to reach completion. Typically this time period would be as per resin manufacturer's specification, and at the end of this period the resin would be completely regenerated with Hydrogen or similar Ions, and ready to commence with the first stage of a new batch. An additional stage may be required in the process. This would be a rinsing stage. During this stage, clean water is again passed through the resin bed to rinse off any excess residual regeneration solution. This represents one complete cycle of a batch process to treat water using ion exchange resin.

The use of ion exchange resins for applications such as the recovery of dissolved metals such as base or precious metals from a liquid (referred to as the solution to be treated) is well known, and is commonly known as Liquid from Liquid Separation (hereinafter called "LLS"). In a typical LLS application the process would consist of several stages. The first stage is always the stage when the target species ions in the solution are adsorbed from the solution onto resin beads in exchange for Hydrogen or similar ions on the resin beads, accomplished by the ion exchange reaction which occurs when the resin is brought into contact with the solution to be treated. This is usually achieved by passing the solution through a fixed or fluidized bed of suitable Ion Exchange resin. The time that the two substances need to be in contact with each other for the Ion exchange reaction to reach completion, is as per the resin manufacturers specifications and is accomplished by controlling the rate at which the solution flows through the resin bed. The solution exiting the resin bed is free of target species ions. This process will continue until the resin is saturated and no longer capable of adsorbing target species ions. In the second stage of a typical LLS process, clean water will be passed through the resin bed (usually in a backwash direction), and the resin will be washed to remove any residual solution and to free any particles that may trapped between the resin beads. In the third stage of the process, a "strip solution" will be passed through the resin bed. The purpose of this stage is to strip off all the target species ions from the resin beads and absorb them into the strip solution. In the fourth stage of the process a regeneration solution will be passed through the resin bed. The purpose of this stage is to regenerate the resin beads with Hydrogen or similar ions. In many applications, stages three and four will be combined, as the strip -A-

solution used functions also as the regeneration solution. The last step in the LLS process is to pass clean water through the resin bed again, this time to rinse off any residual strip/regeneration solution.

There are various existing technologies designed to service these applications, such as the "Higgins Loop" and "Carousel" arrangements. Essentially these are still batch type processes and hence suffer the characteristic problems associated with batch type processes. The most obvious problem associated with batch type processes is that time is wasted in between the various stages of each batch. A further problem with batch type applications is that the entire volume of resin spends an excessive amount of time not being utilized for the actual ion exchange process, but is instead being subjected to washing, rinsing or strip/regeneration.

It is an object of this invention to provide an apparatus and process which addresses the abovementioned problems.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided an ion exchange resin reactor, advantageously to facilitate the continuous treatment of a solution containing target species ions by removing or recovering those ions from the solution onto ion exchange resin beads and then removing or recovering those target species ions from the resin beads and into another solution considered to be an eluate stream or a waste stream depending on the application, the ion exchange reactor comprising:

a loading section arranged to receive an ion exchange resin and a solution to be treated containing targeted ions, wherein the solution to be treated and resin flow in counter currents relative to one another or alternatively wherein the solution to be treated and the resin flow concurrently relative to one another so that the resin and the solution are brought into contact with each other and the targeted ions in the solution are adsorbed onto the resin,

a regeneration section which is in fluid communication with the loading section and which is arranged to receive loaded (saturated) ion exchange resin from the loading section, and

means for recirculating resin from the regeneration section to the loading section, such as a pump, air lift or eductor, preferably an air lift or eductor;

wherein the regeneration section has a smaller cross-sectional area or diameter than the loading section.

The loading section and regeneration sections are typically cylindrical in shape, preferably with a circular cross-section.

Conveniently, the ion exchange reactor is oriented vertically, with the loading section located above the regeneration section so that the resin flows from the loading section to the regeneration section under the force of gravity.

Typically, on an industrial scale, the regeneration section has a diameter 3 times to 15 times, typically 5 times to 10 times, smaller than the diameter of the loading section. The actual diameters and heights of the loading and regeneration sections is calculated after taking into account factors such as the rate of flow of the solution to be treated into the column, versus the required "residence time" that the resin must be in contact with the solution as prescribed by the selected resin manufacturer.

On an industrial scale, the loading section may have a length of from 6-15m, typically 8-13 m and a diameter of 0.5-3m, typically 1-2.5m; and the regeneration section may have a length of 2-8m, typically 4- 6m and a diameter of 0.05-0.5m, typically 0.1 -0.25m.

The regeneration section typically includes a strip/regeneration solution inlet for introducing a strip/regeneration solution into the regeneration section, and an eluate outlet for removing pregnant strip/regeneration solution from the column, after the strip/regeneration solution has been in contact with (by flowing in a counter current direction to), and stripped and regenerated, the resin.

Optionally, the regeneration section includes a primary wash water inlet located above the eluate outlet.

The lower regeneration section may also include a secondary wash water inlet located below the strip/regeneration solution inlet.

Preferably, the ion exchange reactor includes a valve such as a full bore valve between the loading section and the regeneration section, for controlling the rate of flow of loaded resin from the loading section to the regeneration section. This valve will also serve the purpose of isolating the loading section from the regeneration section if necessary.

Optionally, the column includes a valve such as a full bore valve between the secondary wash water section and the resin pick up point, for controlling the rate of flow of regenerated resin from the regeneration section to the top of the column. The loading section is preferably joined to the regeneration section by an inverted conical section. In the case where the resin and solution to be treated flow in counter currents relative to each other, the solution to be treated is introduced into the loading section via an inlet nozzle located at the conical section. In the case where the resin and the solution to be treated flow in a concurrent direction relative to each other, treated solution is removed from the loading section via a nozzle located at the conical section after passing through an internal screen with an aperture size which is large enough to allow the solution and it's solid particles to pass through but too small to allow the resin beads to flow through.

Optionally, the loading section may include a pair, or several pairs of angled screens, to divide a resin bed with a potentially excessive depth, into two or more resin beds with smaller bed depths. These screen's aperture sizes will be large enough to allow the solution and it's solid particles to pass through but too small to allow the resin beads to pass through.

Further, optionally, angled screens or pairs of angled screens may be included in any section of the column if it is envisaged that the flow of resin in a downward direction, and the various solutions in a generally upward direction, would have a flow pattern that is too laminar. The screens would serve the purpose of introducing a degree of turbulence and agitation into the flow patterns and thereby ensuring the resin and solutions are well mixed.

Further, optionally, in the case where the resin and solution to be treated flow in a concurrent direction in the loading section, angled screens or pairs of angled screens may be included in the column if it is envisaged that the flow of resin in a downward direction, and the solution in a downward direction, would have a flow pattern that is too laminar. The screens would serve the purpose of introducing a degree of turbulence and agitation into the flow patterns and thereby ensuring the resin and solutions are well mixed. These screen's aperture sizes are large enough to allow the solution and it's solid particles to pass through but too small to allow the resin beads to pass through.

According to a second aspect of the invention there is provided a process for removing values from a solution to be treated, advantageously to facilitate the continuous treatment of a solution containing target species ions by removing or recovering those ions from the solution onto ion exchange resin beads and then removing or recovering those target species ions from the resin beads and into another solution considered to be an eluate stream or a waste stream depending on the application, the process including the steps of:

causing the solution to be treated to flow in a counter current relative to an ion exchange resin flow in a loading stage; or alternatively, causing the solution to be treated to flow in a concurrent direction relative to an ion exchange resin flow in a loading stage and

causing resin loaded with value from the loading stage to flow in a counter current relative to a strip/regeneration solution flow in a regeneration stage;

wherein the resin is partially fluidized in the loading stage and regeneration stage. Typically, a strip/regeneration solution is introduced into the regeneration section via a strip/regeneration solution inlet located below an eluate outlet from which a pregnant strip/regeneration solution is removed from the regeneration section, after the strip/regeneration solution has been in contact with (by flowing in a counter current direction to), and stripped and regenerated, the resin.

Preferably, primary wash water is introduced to the regeneration section via a primary wash water inlet located above the eluate outlet.

Secondary wash water may be introduced to the regeneration section via a secondary wash water inlet located below the strip/regeneration solution inlet.

Advantageously, resin from the regeneration stage is recycled to the loading stage.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic diagram of an ion exchange resin reactor for a first embodiment of the invention; and

Figure 2 is a schematic diagram of an ion exchange resin reactor for a second embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

This invention relates to an ion exchange resin reactor in the form of a column which is designed to facilitate a continuous flow of partially fluidized ion exchange resin in one direction, and a continuous flow of a solution to be treated (a solution containing values to be adsorbed onto the resin) in the opposite or counter current direction. The column can also facilitate a continuous flow of ion exchange resin in one direction, and a continuous flow of a solution to be treated (a solution containing values to be adsorbed onto the resin) in the same or concurrent direction. The column is also equipped to provide a continuous washing and stripping/regenerating facility for the resin. A solution containing values exits the column either as a treated product, or as waste.

For the sake of convenience, the solution to be treated will be referred to as a "slurry".

With reference to Figure 1 , an ion exchange resin reactor according to a first embodiment of the invention comprises a vertically oriented column 10, which comprises an upper cylindrical loading section 12 and a lower cylindrical regeneration section 14 which are coupled by a conical section 16. The cylindrical sections 14 and 12 both have a circular cross-section. The upper section 12 has a larger diameter and thus cross-sectional surface area than the lower section 14. Typically, on an industrial scale, the upper section 12 has a diameter 5 times to 10 times larger than the lower section 14. A valve 19 (such as a full bore gate valve, or full bore butterfly valve) is provided where the conical section 16 joins the lower cylindrical section 14. As will be described in more detail below, the diameters and lengths of the sections 12 and 14 may be varied according to the requirements of the ion exchange reactor. On an industrial scale, the loading section may have a length of 0.1-15m, typically 1-13 m and a diameter of 0.1 -3m, typically 0.5-2.5m; and the regeneration section may have a length of 0.5-8m, typically 2-6m and a diameter of 0.05- 0.5m, typically 0.1 -0.25m The column 10 includes a resin inlet 17 at the upper end of the upper section 12 and a resin outlet 18 at a lower end of the lower section 14. The column 10 further comprises a slurry inlet 20 between the sections 12 and 14, at the conical section 16 of the column 10. A treated solution outlet 22 is provided at the upper end of the section 12, above the resin inlet 17. The lower section 14 of the column 10 is provided with a strip/regeneration solution inlet 24, a primary wash water inlet 28 above the strip/regeneration solution inlet 24, an eluate outlet 26 just below the primary wash water inlet 28, and a secondary wash water inlet 30 below the strip/regeneration solution inlet 24.

A line 32 and a pump 34 is provided for pumping resin from the resin outlet 18 to the resin inlet 17. The pump 34 is illustrative only. The preferred methods of transporting resin from outlet 18 to the resin inlet 17 are by way of air lift or eductor.

The column 10 is divided into the following main stages by the various inlets and outlets:

- a loading stage A between the resin inlet 17 and the slurry inlet 20; a primary washing stage B between the primary wash water inlet 28 and slurry inlet 20; a stripping and regeneration stage C between the strip/regeneration solution inlet 24 and the eluate outlet 26; and - a secondary washing stage D between the secondary wash water inlet 30 and strip/regeneration solution inlet 24.

In use, an ion-exchange resin is introduced to the column 10 at the resin inlet 17 and, as indicated generally by the arrow 36, the resin flows under the force of gravity towards the bottom of the column 10. At the bottom of the column 10, the resin is collected at the resin outlet 18 and pumped by the pump 34 or airlifted or educted through the line 32 to the resin inlet 17 at the top of the column 10, thus achieving a continuous closed circuit of flowing resin through column 10.

Simultaneously to the continuous flow of resin in the column 10 described above, in a counter current direction, a slurry is pumped into the column 10 via the slurry inlet 20. The flow of the slurry from the slurry inlet 20 and upwardly toward the treated solution outlet 22 is indicated generally by the arrow 38. The counter flow of the slurry to that of the resin causes a partial fluidization of the resin in the loading stage A. Typically, the slurry is pumped into the column 10 through a diffuser (not shown) located within the section 16. The time that the slurry takes to travel up through the loading stage A, all the time being in contact with the resin, is called the "residence time". The time that the slurry takes to flow from the slurry inlet 20 through the resin and out of the treated solution outlet 22 is controlled by controlling the rate at which the slurry is pumped into the column 10 via the inlet 20.

The outlets 22 and 26 are guarded by screens or sieves on the inside of the column to prevent resin from flowing out of these outlets with the liquids being taken off.

With reference to Figure 2, in a second embodiment of the invention and for the purposes of facilitating the treatment of slurries that have a higher relative density than the resin being used, the slurry may be introduced simultaneously to the continuous flow of resin in the column 10 described above, but in a concurrent direction, the slurry is pumped into the column 10 via the nozzle 22. The resin may also be introduced via the nozzle 22, but is preferably introduced vial the inlet 17. The flow of the slurry from the inlets 17 and/or 22 and downwardly toward a treated solution outlet 56 (slurry inlet nozzle 20 in the first embodiment) is indicated generally by the arrows 58. In this embodiment of the invention, the loading stage A is between the inlets 17 and/or 22 and the treated solution outlet 56. The time that the slurry takes to travel down through the loading stage A, all the time being, in contact with the resin, is called the "residence time". The time that the slurry takes to flow from the inlets 17 and/or 22 through the resin and out of the treated solution outlet 56 is controlled by controlling the rate at which the slurry is pumped into the column 10 via the inlets 17 and/or 22 or by the rate that the slurry is allowed to exit from treated solution outlet 56. For this option, treated solution outlet 56 is guarded by an internal screen or sieve, with an aperture size large enough to allow the slurry and it's solid particles to pass through but too small for the resin beads to flow through.

It is envisaged that the flow rates of all liquids into and out of the column will be measured and controlled with devices such as flow meters and control valves, or variable speed drives on the pump motors, or metering pumps.

With reference to Figures 1 and 2, the slurry which is pumped into the upper section 12 of the column 10 comes into contact with the resin in the loading stage A and values (in the form of target species ions) which may be present in the slurry, for example metal ions where the slurry is a dissolved metal bearing solution, are adsorbed onto the resin.

After passing through the loading stage A, the resin flows downwardly through the conical section 16, and into the lower section 14 of the column 10 where the resin is washed and regenerated.

In the case where the slurry contains a dissolved metal as in a typical "resin-in-puip" application, it is necessary to wash off the small amount of solid particles stuck between the resin beads before subjecting the resin to a strip/regeneration solution stage. The resin enters an optional primary washing stage B as it flows through valve 19 into the lower section 14 of the column 10. In the primary washing stage B, a stream of wash water indicated generally by the split arrow 40 enters an upper portion of the lower section 14 of the column 10 via the primary wash water inlet 28. The position of the inlet 28 on the lower section 14 is selected to allow sufficient residence time of the primary wash water with resin, taking into account the rate at which the primary wash water flows upwardly into the column 10. Approximately 90% of the primary wash water flows upwardly through the column in a counter-current direction to the resin, thereby fluidizing the resin and freeing any trapped solid particles and transporting them in an upward direction, and inter¬ mixes with the slurry introduced though the inlet 20 in Figure 1 (inlet 22 in Figure 2) and flows out of the column 10 with the treated solution at the outlet 22 in Figure 1 (outlet 56 in Figure 2). The flow regime of the remaining 10% of the primary wash water is described below.

After passing through the primary wash stage B, the resin flows downwardly through the lower section 14 into the stripping and regeneration stage C of column 10. In the stripping and regeneration stage C, the resin is brought into contact with a strip/regeneration solution which is typically an acid solution that is introduced into the lower section 14 of the column 10 via the strip/regeneration solution inlet 24. The contact of the resin with the acid serves two purposes: firstly the acid removes and concentrates target species ions from the metals or minerals that have been adsorbed onto the resin from the slurry (this is known as stripping), and secondly the acid replenishes the resin beads with hydrogen ions (or other elements depending on the category of resin being used), that were exchanged during the ion exchange chemical reaction (this is known as regeneration). The position of the strip/regeneration solution inlet 24 on the lower section 14 is calculated so as to allow the required residence time that the resin needs to be stripped and regenerated by the acid, taking into account the flow rate of the strip/regeneration solution pumped into the section 14. The counter current flow direction of the strip /regeneration solution to the resin flow, ensures that the resin is properly fluidized and all the resin is stripped and regenerated.

The flow of the strip/regeneration solution into the section 14 via the inlet 24 is shown generally by the arrow 42. The strip/regeneration solution flows upwardly through the section 14 and exits from the column 10 together with approximately 10% of the primary wash water, through the eluate outlet 26. At the eluate outlet 26, the exiting strip/regeneration solution is joined by approximately 10% of the wash water from the primary washing stage B. The reason for allowing this small amount of the primary wash water to flow downwardly through the section 14 and to exit through the eluate outlet 26, is to ensure that none of the strip/regeneration solution flows into the primary washing stage B and on into the loading stage A. The primary wash water stage thus serves the additional purpose of being a liquid seal between the loading stage A and the stripping and regeneration stage C. The eluate exiting the eluate outlet 26 will either be a pregnant solution (product eluate), or it will, be a spent strip/regeneration solution to go on to be recycled depending on the application that the column 10 is used for. After passing through the stripping and regeneration stage C, the resin flows directly into the secondary washing stage D. This is an optional stage which is used to wash off any residual strip/regeneration solution from the resin, before the resin is recycled to the top of the upper section 12 of the column 10. Water is pumped into the lower section 14 of the column 10 at the secondary wash water inlet 30 and 80% of the secondary wash water is caused to flow upwardly in counter-current direction to the resin to wash off residual strip/regeneration solution from the resin. The flow of the 80% of the secondary water is indicated generally by the arrow 46. The water indicated by the arrow 46 flows upwardly and eventually exits with the strip/regeneration solution at the eluate outlet 26. The remaining 20% of the secondary water flows downwardly with the resin (optionally through a valve) to a collection point at the bottom of the column 10 and acts as a carrier medium when the resin is pumped or airlifted or educted to the top of the column 10.

The diameter and length of the upper and lower cylindrical sections 12 and 14 of the column 10 are determined by several factors.

The length of the upper section 12 is determined so as to provide sufficient "bed depth" of resin, taking into consideration the rate at which slurry is pumped into the column 10 at the slurry inlet 20 of Figure 1 (resin and slurry inlet 22 of Figure 2) and out of the outlet 22 of Figure 1 (outlet 56 of Figure 2), and therefore its velocity through the upper section 12, versus the required "residence time" as prescribed by the manufacturer of the resin used in the column 10. If the required bed depth is greater than the maximum bed depth recommended by the resin manufacturer, the bed can be split into two or more individual beds with the introduction of pairs of angled screens 47. As illustrated in the Figure, the pair of angled screens 47 in the loading section 12 of column 10, has produced two individual resin beds E and F. The screens will have an aperture size which is large enough to allow the solid particles in the slurry to pass through, but too small to allow the resin beads to fall through. The angled screens 47 also function as mixers or agitators by disrupting laminar ■ flow patterns of the resin and the slurry. This ensures a good mixing of slurry and resin and therefore good ion exchange reaction. The angled screens 47 then, can perform either or both of the functions of splitting resin beds and/or agitating the flow.

The diameter of the lower section 14 is calculated to primarily ensure that there is sufficient cross-sectional area to permit the maximum required volumetric flow of partially fluidized resin through the section 14 under the force of gravity. The length of the lower section 14 is determined by the number different stripping, regeneration and washing stages that the resin needs to go through and the residence time required in each of these stages, to wash, strip and regenerate the resin.

The ion exchange resin reactor according to the invention described above has advantages over conventional batch processes in that it is a continuous process, and therefore far less time consuming than operating a batch process. Furthermore, it will use less resin than a batch process would use for treating similiar amounts of slurry because at any time during the process at least 85% of the resin is in the loading stage and therefore being subjected to ion exchange chemistry. Ion exchange resin is expensive and this translates into a high cost saving. The apparatus of the invention therefore offers both a time and money saving when compared to conventional batch process technology. The apparatus of the invention described above is may be used for

the treatment of a metal or mineral bearing solution, or for other ion

exchange applications of which there are many and it is not the

object of this document to attempt to list them all. However purely for

example purposes some applications for which the column could be

utilised are listed below:

SOLUTION TO BE TREATED APPLICATION Water Demineralisation Water Desalination Water Purification Water Softening Water Polishing Nuclear reactor cooling water Removal of nuclear contaminants Waste stream containing Cadmium Removal from waste Cobalt Recovery Copper Recovery and concentration Electroplating Rinse water recycling Lysine Hydrolysis Waste stream containing Mercury Recovery or removal from waste Nickel Iron and cobalt removal Waste stream containing Nickel Recovery from waste Platinum Recovery Gold Recovery Silver Recovery Uranium Recovery from leach liquors Sugar Numerous applications Waste stream containing Cyanides Removal from waste Zinc Recovery

An ion exchange resin is an insoluble matrix (or support structure)

normally in the form of small (0.25-2mm diameter) beads, fabricated

from an organic polymer substrate on the surface of which are sites

with easily trapped and released ions. There are a great variety of ion

exchange resins which are fabricated to selectively prefer one or

several types of ions. Types of ion exchange resins include strong

acid cation or anion, strong base cation or anion, weak acid cation or

anion, weak base cation or anion and chelating resins. The invention will now be described in more detail with reference to the following non-limiting examples.

Example 1 - Laboratory Scale

This laboratory scale example shows the effectiveness of the apparatus and the process of the invention. It is to be noted that an industrial scale reactor will have different sizes, and in particular, the ratio of diameter of loading section to diameter of regeneration of an industrial scale reactor will be different. This example in no way affects the scope of protection of the invention.

With reference to Figure 1 , a laboratory scale reactor column 10 was erected using a Perspex™ cylinder 12 having a length of 500mm and a diameter of 63 as a loading section and a a Perspex™ cylinder 14 having a length of 355mm and a diameter of 26mm. The cylinders 12 and 14 were joined by a conical section 16 having a length of 25 mm. A 25mm diameter wafer type butterfly valve 19 was provided at the base of the conical section 16.

The cylinder 12 had an inlet 17 for introducing recycled resin and an outlet 22 for removing treated solution. A slurry inlet 20 was provided in the conical section 16. The following were provided on the cylinder 14 at the following positions from the top of the cylinder 14: Strip/regeneration solution (40% sulphuric acid) inlet 24 - 220mm Primary wash water inlet 28 - 110mm Eluate outlet 26 - 120mm Secondary wash water inlet 30 - 330mm Resin outlet 18 - 355mm.

A slurry containing target ions Nickel and Cobalt (2g/L Nickel and 400 mg/L Cobalt) was used. The resin used was DOWEX™ M4195 chelating resin available from The Dow Chemical Company. The reactor column 10 was run in the manner described in the detailed description of the invention, at a slurry feed rate to the column of 2- 2.5 L/min. The eluate stream 26 contained 55g/L Nickel and 10-11 g/L Cobalt and treated solution in the outlet stream 22 contained <1 mg/L Nickel and <1 mg/L Cobalt. This laboratory scale example shows how effective the apparatus and process of the invention is at recovering very weak concentrations of metals/minerals. The treated solution (waste) contains less than 1 ppm target species.

Example 2 - Industrial Scale

With reference to Figure 1 , this example provides the dimensions for an example of an industrial scale reactor 10 of the invention:

Loading section 12: 750mm diameter 8000mm length

SLURRY FLOW RATE 3000 to 8000 litres per hour

Conical section 16: 750mm high, reducing from 750mm ID to 90mm ID

Valve 19: 75mm high (full bore wafer type butterfly valve)

Regeneration section 14: 90mm diameter 5750mm length

Water inlet 28: 1750mm below valve 19

WASH WATER FLOW RATE 300 to 500 liters per hour Eluate outlet 26: 200mm below water inlet 28

Strip/regeneration inlet 24: 2000mm below eluate outlet 26

STRIP REGEN SOLUTION FLOW RATE 220 to 400 litres per hour

Secondary wash water inlet 30: 1550mm below Strip/regeneration inlet 24

WASH/RINSE WATER FLOW RATE 200 to 500 litres per hour

Resin outlet 18: 250mm below secondary wash water inlet 30, includes a full bore wafer type Gate valve

A typical feedstock (solution to be treated) in this ion exchange reactor is a waste stream containing 1g/L or less of dissolved metal (target species) such as cadmium and/or mercury. The ion exchange resin is typically a weak acid cation resin such as Amberlite™ GT73 available from Rohm and Haas. A typical regeneration solution would be H2SO4 (at 40-45% cone.) or HCI (at 40-50% concn.).