Method for purification of a cobalt containing solution by continuous ion exchange

Abstract

Methods are for purification of a cobalt containing solution from impurity metals by processing the feed solution through a continuous counter-current ion exchange process comprising of several beds containing cationic ion exchange material arranged in interconnectable zones 1, 2, 3-N in a simulated moving bed arrangement.

Claims

1. A method for purification of a cobalt containing feed solution from impurity metals by processing the feed solution through a continuous counter-current ion exchange process comprising of several beds containing weakly acidic cation exchange resin with chelating (aminomethyl)phosphonic acid functionality arranged in interconnectable zones 1, 2, 3-N in a simulated counter-current moving bed arrangement, wherein each bed is interconnectable with two adjacent beds, the method comprising: (a) introducing a desorbent solution, which has sufficiently low pH that impurity metals are desorbed, into one or more beds of the first, regeneration zone (zone I) and collecting an extract containing impurity metals from the same bed and/or from another bed downstream within the said regeneration zone, (b) introducing a wash solution of pH higher than the desorbent solution into one or more of said beds of the regeneration zone and collecting an extract containing impurity metals and desorbent from the said bed and/or from another beds downstream within the first, regeneration zone, (c) introducing an aqueous eluent of pH sufficiently low to desorb Co but sufficiently high not to desorb impurity metals into one or more beds of zone downstream (zone II) to said regeneration zone, (d) introducing the cobalt containing feed solution, which has pH sufficiently high to adsorb impurity metals but sufficiently low to avoid adsorbing Co, into one or more beds of the next zone downstream (zone III) from the zone of step (c) and collecting a cobalt product raffinate solution from the said bed and/or from another beds downstream, wherein the positions where the cobalt containing feed, eluent, desorbent, and wash solution are introduced and where the impurity metals containing extract, spent wash solution, and cobalt containing raffinate are collected are changed to adjacent beds downstream to simulate the counter-current flow of the solid and liquid phases after such periods of time that cobalt propagates downstream with fluid phase in zones II and III, impurity metals propagate upstream with the simulated flow of the solid phase in zones II and III, impurity metals are desorbed in zone I, and the desorbent is washed from the resin in zone I.

2. The method of claim 1, further comprising: (e) passing part of the cobalt raffinate product solution to a zone IV consisting of one or more said beds downstream of the cobalt raffinate outlet to recover eluent and reduce dilution of product.

3. The method of claim 1, further comprising recycling the recovered eluent to be used as eluent.

4. The method of claim 1, wherein the concentration of cobalt in the cobalt containing feed solution is from 10 g/L to a saturated solution.

5. The method of claim 1, wherein the cobalt exists as cobalt sulfate.

6. The method of claim 1, wherein the desorbent is a solution of a inorganic acid, such as HCl, H.sub.2SO.sub.4, H.sub.3PO.sub.4 and HNO.sub.3, with proton concentration below 6.0 M.

7. The method of claim 1, wherein the eluent is a solution of a inorganic acid with pH in the range 2.0 to 0.

8. The method of claim 1, wherein the wash solution contains an inorganic acid with pH same or below that of the feed solution.

9. The method of claim 1, wherein the steps (a) and (b) are carried out in beds disconnected from other beds.

10. The method of claim 1, wherein the ion exchange beds are in stationary columns and the liquid inlet and outlet streams are periodically advanced by one column increment in the direction of the liquid flow.

11. The method of claim 1, wherein the ion exchange beds are in moving columns and the columns are periodically moved by one bed increment relative to stationary liquid feed and outlet ports in the opposite direction of the liquid flow.

12. The method of claim 1, wherein the steps (a) and (b) are operated in the same beds in alternating time controlled substeps.

13. The method of claim 1, wherein the impurity metals extracted from cobalt containing solution comprise at least one or more of the following: Cd, Mn, Mg, Pb, Cu, Zn, U, Ca, Fe, Ni, Cr, Na, and/or Al.

14. The method of claim 1, wherein regeneration zone is disconnected from other zones.

15. The method of claim 1, wherein each zone includes 1-4 interconnected beds.

16. The method of claim 1, wherein each zone includes 2-3 interconnected beds.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates an exemplary embodiment of the SMB-process according to the invention.

(2) FIG. 2 illustrates an exemplary embodiment of the SMB-process according to the invention.

(3) FIG. 3 illustrates an exemplary embodiment of the SMB-process according to the invention.

(4) FIG. 4 illustrates ion exchange bed outlet profile of a feed solution in pH 0.1.

(5) FIGS. 5 A), B), and C) illustrate the amount of metals in each outlet stream for feed solution in pH 0.1.

(6) FIG. 6 illustrates ion exchange bed outlet profile of a feed solution in pH 1.0.

(7) FIGS. 7 A), B), and C) illustrate the amount of metals in each outlet stream for feed solution in pH 1.0.

(8) FIG. 8 illustrates a reference curve for metals recovery from hydrometallurgical process solution using prior-art process solution.

DETAILED DESCRIPTION

(9) In the exemplary embodiment of the invention a method is provided wherein a feed solution containing higher than 10 g/L of Co is provided into a simulated moving bed system, comprising of one or more beds containing ion exchange media, together with an aqueous eluent solution of pH below the feed solution and a desorbent of strong acid and producing at least a first product stream and a second product stream. Beds containing ion exchange media are provided by a series of columns containing ion exchange resin. It will be known to one skilled in the art that the process of simulated moving bed by a system of feed tanks, pumps, piping, valves, instrumentation and process control can be realized in different ways and should not be limited to the embodiment of this invention.

(10) In an embodiment of the invention provided here as an example the process operating steps in a system of 8 columns are as shown in FIG. 1. These columns are arranged in three successive zones I, II and III. First zone or regeneration zone (denoted by zone I in FIG. 1), includes two interconnected columns (columns 1 and 2). Zone II, subsequent to said regeneration zone downstream, includes three interconnected columns (columns 3, 4 and 5). Zone III in which raffinate is collected, includes three interconnected columns (columns 6, 7 and 8) downstream from zone II.

(11) The SMB process is achieved by a series of valves managed preferably by a microprocessor to create a simulated counter current flow of solid and liquid phases by periodically switching the inlet and outlet ports by one column increment in the direction of the liquid flow. The same counter current operation is achieved if the columns are moved periodically by one increment in the direction opposite to the liquid flow. The switching interval and internal flow parameters can be optimized by one skilled in the art for particular needs of the feed solution and target purities.

(12) In zone III in FIG. 1 the impurity metals will be adsorbed in the ion exchange resin while cobalt is rejected and carried downstream to raffinate by the eluent fluid flow. A zone II of one or more columns, in the exemplary embodiment three columns, is provided upstream of the feed position between zones I (regeneration zone) and III to reject Co from entering the impurity metals desorption zone I and thus keeping cobalt yield close to 100% with optimized pH of the eluent lower than pH of the feed solution and typically from pH 2.0 to 0 adjusted preferably with H.sub.2SO.sub.4 but in principle any inorganic acid (such as HCl, H.sub.2SO.sub.4, H.sub.3PO.sub.4 and HNO.sub.3). Preferably eluent pH is below 1.5 for optimal results.

(13) The impurities including, but not limited to, any of the following: Cd, Mn, Mg, Pb, Cu, Zn, U, Ca, Fe, Ni, Cr, Na, and/or Al, are separated from Co in zones II and III and removed from the ion exchange resin in a separate regeneration zone or Zone I using a desorbent solution of inorganic acid with proton concentration below 6.0 M, preferably below 4.5 M. Preferably inorganic acid is H.sub.2SO.sub.4. The resin is also washed with water adjusted with inorganic acid in the same pH, or below as the feed solution. In the example provided the impurities are desorbed and the resin washed in the same zone I (FIG. 1) in different substeps 1) and 2) to avoid the need for an additional fifth zone.

(14) In an alternative embodiment of the present invention the zone II can be omitted and instead part of the extract from impurities desorption in zone I that contains Co can be recycled by the use of a timed valve to the feed solution or even to process stages prior to the SMB CIX purification depicted in this invention.

(15) While the feed is being eluted in zone III the cobalt concentration is diluted. The dilution of the product collected as raffinate can be reduced by addition of a zone of one or more columns downstream of the raffinate collection port or collecting the dilute portion of the raffinate separately by use of a timed valve (M. KaspereitAdvanced operating concepts for SMB processes. In: E. Grushka, N. Grinberg (Eds.): Advances in Chromatography, CRC Press, 2009 (p. 165-192)).

(16) In an embodiment of the invention depicted in FIG. 2 a zone IV of two columns is added. Only part of the flow from zone III is directed into the raffinate while the rest is let to pass to zone IV. The flow rate into zone IV is adjusted such low that the cobalt solution does not exit zone IV.

(17) In an embodiment of the invention depicted in FIG. 3, the outlet stream of zone IV is circulated to the inlet of zone II and used as the eluent, preferably after adjusting its pH.

(18) Naturally it is to be understood that zones can comprise one or more beds and differing number of beds in zones that is presented in figures and examples. Also it should be understood that numbering of zones (zone I, zone II, zone III . . . ) in figures is for simplifying the explanation/description of the embodiments of the invention, and that zone into which a desorbent solution is passed is referred as first zone because of the simplifying the explanation, and that numbering of the zones is not intended for limiting the scope of the claims or the embodiments of the invention. Also it should be understood that the two substeps in regeneration zone (zone I) to regenerate and wash the resin can be conducted sequentially as described here or in parallel in different zones.

(19) In a more detailed description of the SMB process as executed in the first example given below and as depicted in FIG. 1 the first step is as follows: In the first substep 1) of 5 minutes in duration a stream of 2.0 M H.sub.2SO.sub.4 is introduced into column 1 and impurity metals selected from: Cd, Mn and Pb, are collected as extract from column 2.

(20) Eluent stream of H.sub.2SO.sub.4 adjusted to pH 0.1 is introduced into column 3 and is eluting the adsorbed metals, in particular Co, downstream through interconnected columns 3, 4 and 5. Feed solution of concentrated cobalt sulphate adjusted to pH 0.1 with H.sub.2SO.sub.4 is introduced into the inlet of column 6. The feed solution is eluted downstream and passes through the interconnected columns 6, 7 and 8. A diluted Co and Mg containing product is collected from column 8 while other metals are stronger adsorbed into the resin.

(21) In the second substep 2) of 5 minutes in duration a wash solution of H.sub.2SO.sub.4 adjusted to pH 0.1 is introduced into the column 1. The H.sub.2SO.sub.4 desorbent solution with proton concentration of 4.0 M, previously contained in column 1 and the spent wash solution containing very little impurity metals is collected from column 1. Column 2 containing impurity metals is disconnected from the circuit in this substep. During substep 2) the feed solutions is passed to column 6 and eluent solution to column 3 and eluted through the columns as in substep 1).

(22) After the full step of 10 minutes comprising of the two 5 minute substeps the input and output ports are switched by one increment downstream. Thus, in the first substep 1) of the subsequent full step 2 H.sub.2SO.sub.4 with proton concentration of 4.0 M (=2.0M H.sub.2SO.sub.4 solution) is introduced into column 2 and impurity metals collected from column 3. Eluent is introduced into column 4 eluting cobalt downstream. After reconnecting columns 8 and 1, Co rich feed solution is introduced into column 7 and then diluted Co and Mg product is collected from column 1 previously regenerated and washed during the full step 1. Each step is timed so that the stronger adsorbing impurity metals are left in the columns in zones II and III and do not travel forward with the liquid flow and thus eventually enter the regeneration zone (zone I).

Example 1

(23) In FIG. 4 is shown the ion exchange bed outlet profile of a short pulse of feed solution in pH 0.1 into a single column in batch mode. The composition of the feed is provided in table 1. The ion exchange material is a weakly acidic cation exchange resin with chelating (aminomethyl)phosphonic acid functionality, specifically Lewatit TP-260. In FIG. 4 on the left side of the dashed line is the outlet concentration history of the adsorption, on the right side of the dashed line is the concentration history of desorption with H.sub.2SO.sub.4 with proton concentration of 4.0 M (=2.0M H.sub.2SO.sub.4 solution). As seen from the graph in FIG. 4 in this pH all metals will elute before introducing the desorption acid.

(24) As seen from FIG. 4 the ion exchange resin used has higher affinity for the impurity metals, whereas Co and Mg are not as strongly adsorbed. Of particular interest for the present invention is the formation of a pronounced Co containing front in the outlet of the column. Optimizing the feed and eluent pH and the internal flow rates in an SMB CIX unit, it is possible to further emphasize this effect to reach nearly 100% purity for cobalt in relation to Cd, Mn and Pb in the product stream.

(25) TABLE-US-00001 TABLE 1 Component Concentration, mg/L Cd 45 Co 82 000 Mg 390 Mn 110 Pb 7

(26) In the following exemplary embodiment of the invention provided here the feed containing 78 g/L of Co together with Cd (80 mg/L), Mg (350 mg/L), Mn (100 mg/L) and Pb (5 mg/L) is purified using feed and eluent pH of 0.1. The experiment was done in SMB configuration as depicted in FIG. 1, with columns packed with TP-260 ion exchange resin. The impurities are separated from Co and Mg and removed by regeneration from the ion exchange resin in a separate regeneration zone (Zone I) using a desorbent solution of H.sub.2SO.sub.4 with proton concentration of 4.0 M (=2.0M H.sub.2SO.sub.4), followed by wash solution of H.sub.2SO.sub.4 in pH 0.1. In the example provided the impurities are desorbed and the resin washed in the same zone I (see FIG. 1) in subsequent timed substeps 1) and 2) during a full step.

(27) In FIG. 5 is provided the amount of metals in each outlet stream. The amounts are given in mass of metal relative to mass in feed against the number of the SMB switch. As seen from the charts all Co and Mg are collected in the raffinate (FIG. 5 A), whereas the majority of impurity metals are in regeneration and wash streams (FIG. 5 B-C).

(28) Average concentrations of each metal in the various outlet streams of the SMB CIX system in pH 0.1 when it has reached a steady state are listed in Table 2. As can be seen from FIG. 5 and table 2 cobalt and magnesium are significantly purified. In this present example the concentration of Co in the product is diluted to about 35% of the feed concentration. This is due to the mixing of the eluent of pH 0.1 and the cobalt sulfate feed at the border of zones II and III (see FIG. 1). If an additional zone IV is added downstream of the product collection port (raffinate) as depicted in FIG. 2 the dilution of the product can be decreased by an estimated 20%.

(29) TABLE-US-00002 TABLE 2 Average concentration in stream, mg/L Metal Feed Raffinate Regeneration Wash Cd 80 3 30 1 Co 78000 27400 458 0 Mg 350 119 3 0 Mn 100 2 32 2 Pb 5 0 2 0

Example 2

(30) In FIG. 6 is shown the ion exchange bed outlet profile of a short pulse of feed solution in pH 1.0 into a single column in batch mode. The composition of the feed is provided in Table 3. The ion exchange material is a weakly acidic cation exchange resin with chelating (aminomethyl)phosphonic acid functionality, specifically Lewatit TP-260. In FIG. 6 on the left side of the dashed line is the outlet concentration history of the column during feeding, on the right side of the dashed line is the concentration history during desorption with H.sub.2SO.sub.4 with proton concentration of 4.0 M (=2.0M H.sub.2SO.sub.4).

(31) TABLE-US-00003 TABLE 3 Component Concentration, mg/L Cd 65 Co 87 000 Mg 400 Mn 115 Pb 8

(32) In the following exemplary embodiment of the invention provided here the feed containing 78 g/L of Co together with Cd (80 mg/L), Mg (350 mg/L), Mn (100 mg/L) and Pb (5 mg/L) is purified using feed and eluent pH of 1.0. The experiment was done in SMB configuration as depicted in FIG. 1, with columns packed with TP-260. The impurities are separated from Co and Mg and removed from the ion exchange resin in a separate regeneration zone (Zone I) using a desorbent solution of H.sub.2SO.sub.4 with proton concentration of 4.0 M, followed by wash solution of H.sub.2SO.sub.4 in pH 1.0. In the example provided the impurities are desorbed and the resin washed in the same zone I (see FIG. 1) in subsequent timed substeps 1) and 2) during a full step.

(33) In FIG. 7 is provided the amount of metals in each outlet stream. The amounts are given in mass of metal relative to mass in feed against the number of the SMB switch. As seen from the charts in this pH the majority Co and Mg report to the raffinate (FIG. 7 A) with more impurity metals than seen in pH 0.1 (FIG. 5 A), whereas the majority of impurity metals are in regeneration and wash streams with some Co and Mg being carried to the regeneration zone (zone I, FIG. 7 B-C).

(34) Average concentrations of each metal in the various outlet streams of the SMB CIX system in pH 1.0 when it has reached a steady state are listed in table 4. As can be seen from FIG. 7 and table 4 cobalt and magnesium are purified, albeit to a lesser extent as seen in pH 0.1. In this present example the concentration of Co in the product is diluted to about 30% of the feed concentration.

(35) TABLE-US-00004 TABLE 4 Average concentration in stream, mg/L Metal Feed Raffinate Regeneration Wash Cd 80 0 28 2 Co 78000 24600 8300 0 Mg 350 105 45 0 Mn 100 11 28 4 Pb 5 0 2 1

Reference Example 3

(36) This example is provided here only as a reference in support of the background of the invention. In FIG. 8 is provided a breakthrough curve for metals recovery in a single column in batch mode from a synthetic hydrometallurgic process solution using a bis-2-(pyridylmethyl)amine functional resin. The feed solution composition is listed in table 5. The pH of the solution is 3.4 and the counter ion for metal cations is sulfate. As seen from the curve in FIG. 8 a bis-2-(pyridylmethyl)amine functional ion exchange resin, specifically Dowex M-4195, is incapable of purifying Co from impurity metals in the present solution. This confirms that the methods described in WO 2011/100442 and WO 2013/165735 using Dowex M-4195 are not applicable to purification of such concentrated cobalt sulfate solutions as considered in the present invention because no separation is achieved.

(37) TABLE-US-00005 TABLE 5 Component Concentration, mg/L Cd 100 Co 100 000 Cu 100 Mg 500 Mn 100 Pb 20

(38) The invention has been explained above with reference to the aforementioned embodiments, and several advantages of the invention have been demonstrated. It is clear that the invention is not only restricted to these embodiments, but comprises all possible embodiments within the spirit and scope of the inventive thought and the following patent claims.