AU2021377197A1 - Process for separating hafnium and zirconium - Google Patents

Abstract

A process for separating hafnium and zirconium, in particular from a sulfate based solution is provided. The process includes the steps of: concentrating an acidic sulfate based solution containing zirconium and hafnium, the solution having a hafnium:zirconium weight ratio as given by Hf/(Hf+Zr) greater than the typical weight ratio of naturally occurring zirconium ores and/or concentrates; heating the solution; contacting the solution with an amine based solvent to create a hafnium rich, high purity rafinate and a zirconium loaded solvent; and stripping the zirconium loaded solvent to produce a stripped solvent and a zirconium loaded strip.

Description

PROCESS FOR SEPARATING HAFNIUM AND ZIRCONIUM

Technical Field

[0001] The present disclosure relates to a process for separating hafnium and zirconium, in particular from a sulfate based solution.

Background of the Disclosure

[0002] Zirconium is used in a variety of applications, for example in the formation of advanced ceramics, precision casting, electronic sensors, water treatment, corrosion resistant alloys, catalysts, and in nuclear applications. Hafnium is always present in zirconium minerals and is often not separated from zirconium due to their very similar chemistries, which makes separation challenging. For nuclear applications such as nuclear fuel rod cladding, however, zirconium with very low concentrations of hafnium is required due to the latter's high neutron absorbing ability. High purity zirconium containing low concentrations of hafnium is commonly referred to as nuclear grade zirconium. Hafnium is also used in other nuclear applications where its high neutron absorbing ability is desirable, such as control rods for reactors, as well as in other niche applications, e.g. as an alloying element in cutting tools. Presently, most hafnium is produced as a byproduct of the production of nuclear grade zirconium.

[0003] Present known methods of producing nuclear grade zirconium include the MIBK (methyl isobutyl ketone) process, the TBP (tributyl phosphate) process, the Toyo process, and the CEZUS process. With the exception of the CEZUS process, these methods rely on solvent extraction to separate zirconium from hafnium.

[0004] The MIBK process involves treating zircon through a carbochlorination high temperature (1200°C) process to produce tetrachloride complexes of zirconium and hafnium. These products are dissolved in thiocyanate media and hydrochloric acid, from which hafnium is selectively extracted by MIBK, leaving behind a zirconium rich raffinate. While this results in a zirconium product with little hafnium content, there are some disadvantages to this process. The MIBK solvent is toxic, hightly volatile, and flammable with a low flashpoint. Further, MIBK has been reported to suffer from poor phase disengagement and therefore the process is not operated in a fully continuous manner. Additionally, because MIBK has a relatively high solubility in water, and hydrochloric acid causes decomposition of the thiocyanate, the process has a high chemical consumption. The wastes produced by this process include ammonium, thiocyanides and cyanides which poses further difficulties when aiming to avoid negative environmental impacts associated with waste disposal.

[0005] The TPB process involves treating zircon by caustic fusion and then solubilizing zirconium and hafnium in nitric media. Zirconium is then preferentially extracted to the TPB solvent where it can then be recovered. The use of nitric acid in the concentrations required, however, requires special consideration to the materials of construction for any systems. Further, this process is also reported to suffer from the formation of stable emulsions resulting in problems with continuous processing. The process also does not result in a high purity hafnium stream.

[0006] The Toyo process involves treatment of zircon by caustic fusion and dissolution in sulfuric acid. A tertiary amine solvent is then used to selectively extract zirconium from hafnium. Similar to the TPB process, this process does not result in a high purity hafnium stream.

[0007] The CEZUS process is a totally pyrometallurgical route which exploits the small difference in vapour pressure between zirconium and hafnium tetrachloride and extractive distillation to separate zirconium and hafnium. This is an energy intensive process which requires multistage distillation columns operated at high temperature.

[0008] There thus exists a need to provide a process capable of separating hafnium from zirconium in a way that avoids toxic and/or volatile solvents and which is capable of producing high purity hafnium.

Summary of the Invention

[0009] In a first broad aspect, there is provided a process for separating hafnium and zirconium, including the steps of: concentrating an acidic sulfate based solution containing zirconium and hafnium, the solution having a hafniurmzirconium weight ratio as given by Hf/(Hf+Zr) greater than the typical weight ratio of naturally occurring zirconium ores and/or concentrates; heating the solution; contacting the solution with an amine based solvent to create a hafnium rich rafinate and a zirconium loaded solvent; and stripping the zirconium loaded solvent to produce a stripped solvent and a zirconium loaded strip. [0010] In certain embodiments, the hafniurmzirconium weight ratio of the solution is greater than 3%.

[0011] In certain embodiments, concentrating the acidic sulfate based solution includes subjecting the solution to a nanofiltration process.

[0012] In certain embodiments, a sulfuric acid permeate produced by the nanofiltration process is recovered for reuse in the process.

[0013] In certain embodiments, concentrating the acidic sulfate based solution includes precipitating zirconium and hafnium solids from the solution and re-dissolving said solids in a smaller volume of solution.

[0014] In certain embodiments, the process further includes: contacting the stripped solvent with an alkali solution to produce a regenerated solvent which can then be reused in the process.

[0015] In certain embodiments, the alkali solution is sodium carbonate or a mixture of sodium carbonate and sodium hydroxide.

[0016] In certain embodiments, the process further includes: reprotonating the regenerated solvent prior to reuse in the process.

[0017] In certain embodiments, the reprotonation is carried out using sulfuric acid.

[0018] In certain embodiments, stripping the zirconium loaded solvent comprises contacting said solvent with sodium chloride.

[0019] In certain embodiments, the acidic sulfate based solution is a raffinate produced by a zirconium solvent extraction process.

[0020] In certain embodiments, the zirconium solvent extraction process which produces the raffinate includes contacting a zirconium containing feed with the amine based solvent, and solvent from the zirconium solvent extraction process is regenerated in a common regeneration circuit with the stripped solvent to form a common regenerated solvent for use in the process for separating hafnium and zirconium and the zirconium solvent extraction process. [0021] In certain embodiments, the process further includes reprotonating the common regenerated solvent.

[0022] In certain embodiments, the reprotonation is carried out using sulfuric acid.

[0023] In certain embodiments, the solution is heated to a temperature above about 50°C and below about 100°C.

[0024] In certain embodiments, the process further includes recovering hafnium products from the hafnium rich raffinate.

[0025] In certain embodiments, the process further includes recovering zirconium products from the zirconium loaded solvent.

[0026] According to a second broad aspect, there is provided a pre-treatment process for an acidic sulfate based solution containing zirconium and hafnium prior to separating hafnium and zirconium, including: concentrating the acidic sulfate based solution; heating the acidic sulfate based solution.

[0027] In certain embodiments, concentrating the acidic sulfate based solution comprises subjecting the solution to a nanofiltration process.

[0028] In certain embodiments, the acidic sulfate based solution is heated to a temperature above about 50°C and below about 100°C.

[0029] According to a third broad aspect, there is provided a system for separating zirconium and hafnium, including: a pre-treatment stage including: a concentration step which receives a feed containing zirconium and hafnium and increases the relative concentration of zirconium and hafnium in the feed; a heating step; an extraction circuit which receives the feed following the pre-treatment stage and contacts the feed with a solvent to form a zirconium loaded solvent and a hafnium rich raffinate; a stripping circuit which transfers zirconium from the zirconium loaded solvent to form a stripped solvent and a loaded strip; a regeneration circuit which at least partially removes chloride from the stripped solvent to form a regenerated solvent which can then be reused in the extraction circuit.

[0030] In certain embodiments, the system further includes a hafnium precipitation circuit for recovering hafnium from the hafnium rich raffinate. [0031] In certain embodiments, the system further includes a zirconium precipitation circuit for recovering zirconium from the zirconium loaded solvent.

[0032] In certain embodiments, the system further includes a reprotonation circuit which receives regenerated solvent and reprotonates it prior to reuse in the system.

[0033] In certain embodiments, the feed containing zirconium and hafnium is a raffinate produced by a zirconium solvent extraction system.

[0034] In certain embodiments, the zirconium solvent extraction system includes: a first extraction circuit, which receives a pregnant leach solution containing zirconium and hafnium and contacts the pregnant leach solution to form a raffinate which proceeds to the pre-treatment stage and a first zirconium loaded solvent; an acid scrub circuit which receives the first zirconium loaded solvent and removes co-extracted hafnium from the circuit to form a dehafniated zirconium loaded solvent; a first stripping circuit which transfers zirconium from the dehafniated zirconium loaded solvent to form a first stripped solvent and a dehafniated zirconium loaded strip.

[0035] In certain embodiments, the first stripped solvent and the stripped solvent are fed to a common regeneration circuit which at least partially removes chloride from the stripped solvent to form a regenerated solvent which can be used in the first extraction circuit and the extraction circuit.

[0036] In certain embodiments, the system further includes a dehafniated zirconium precipitation circuit for recovering high purity zirconium from the dehafniated zirconium loaded strip.

[0037] In certain embodiments, the system used to carry out a process according to the first aspect.

[0038] Other aspects, features, and advantages will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of the inventions disclosed. Brief Description of the Figures

[0039] The present disclosure will become better understood from the following detailed description of various non-limiting embodiments thereof, described in connection with the accompanying figures, wherein:

[0040] FIGURE 1 shows a schematic process diagram for an embodiment of the present invention.

[0041] FIGURE 2 shows a schematic process diagram for an alternative embodiment of the present invention.

[0042] FIGURE 3 shows the equilibrium curve for increasing zirconium loading onto the solvent.

[0043] FIGURE 4 shows the comparison of equilibrium curves for heat treated and nonheat treated feeds.

Detailed Description

[0044] The inventors have developed a process which enables the separation of hafnium from zirconium. This process includes pretreating a feed which comprises an acidic sulfate based solution containing hafnium and zirconium by heating the feed above 50°C and below 100°C, preferably to about 98°C, and concentrating the solution. Otherwise stated, the feed is subjected to a pretreatment process which includes a concentration step and a heat treatment step. The heating and concentration steps can be carried out in any order. Preferably, the feed has a higher weight ratio of hafniurmzirconium relative to the ratio found in ores and concentrates of zirconium, where weight ratio is given by the formula Hf/(Hf+Zr). While the exact ratio varies, the majority of naturally occurring ores and concentrates have a weight ratio of 0.5-3%. In preferred embodiments of the invention, the process avoids toxic and/or volatile solvents and results in a high purity hafnium stream.

[0045] The heat treatment step improves the separation of zirconium from hafnium when the former is present in lower concentrations in the feed. This provides for better zirconium extraction in following steps, and a higher purity hafnium stream as a result. The heating step may be carried out by any known methods capable of heating the feed to a temperature between above about 50°C to a temperature below 100°C so that the solution is heated below its boiling point. In preferred embodiments, the heat-treatment step involves heating the feed to 98°C for around 4 hours.

[0046] The concentrating step increases the relative amount of zirconium and hafnium in the solution, and in a preferred form is carried out by nanofiltration, where a membrane is sized to only allow smaller ions such as the bisulfate ion and its counter ion to pass through it. The larger zirconium and hafnium ions are thus rejected, resulting in a retentate with a higher concentration than the initial feed. A further advantageous feature of using nanofiltration is that the permeate can be recovered and recycled into this or other processes. In another preferred embodiment, the concentration step may involve precipitating out zirconium and hafnium and then redissolving the precipitated solid to form a more concentrated solution. An advantageous feature of using this concentration method is that impurities may be removed during the precipitation and re-dissolution. The precipitation and re-dissolution of zirconium solids may be used instead of or in conjunction with nanofiltration to concentrate the solution. In some embodiments, both nanofiltration and precipitation/re-dis solution may be used, with nanofiltration concentrating the feed and allowing acid to be recovered from the feed, and precipitation/re-dis solution used to further concentrate the feed and to remove impurities from the feed.

[0047] It will also be understood that in other embodiments, other known methods of concentrating the amount of zirconium and hafnium in a solution may be used in place of or in conjunction with nanofiltration/precipitation and redissolution of the zirconium solids.

[0048] Following this pretreatment, the pretreated feed is contacted with a solvent in order to transfer zirconium to the solvent while rejecting hafnium. The solvent is an amine based reagent, preferably a tertiary amine based reagent. Any amine based reagent which is suitable for extracting zirconium known in the art may be used in this process. The extraction of zirconium to the solvent leaves behind a raffinate with high hafnium content and very little to no zirconium content. The raffinate can then be used as a high purity hafnium stream, from which hafnium products can be precipitated for use or further processing. A further advantage of this process is that it can be used independently of the production of nuclear grade zirconium, that is to say that this process may provide an alternative route for hafnium production.

[0049] The zirconium loaded solvent can then be stripped to provide a zirconium loaded strip from which zirconium products can be precipitated for use (for example by the Kroll process) and/or further processing. The stripped solvent can then be regenerated and in some embodiments, reprotonated before being reused for further pretreated feed. In embodiments where nanofiltration is part of the pretreatment step, the permeate from nanofiltration, which is sulfuric acid, may be used to reprotonate the solvent.

[0050] Embodiments of the process according to the present invention may also be used to produce a high purity zirconium stream as well as the high purity hafnium stream. Broadly speaking, in these embodiments, the process may be thought of as including a process for creating dehafniated (high purity) zirconium, as well as the process for producing high purity hafnium described above. Advantageously, these two processes use the same solvent, enabling the possibility of providing a common regeneration and/or reprotonation circuit.

[0051] The dehafniated zirconium process may include contacting a feed, which is preferably an acidic sulfate based solution including zirconium and hafnium with a hafniurmzirconium weight ratio similar to that which naturally occurs in zirconium ores and concentrates, such as in the range between 0.5 to 3%. The feed is contacted with a solvent, which is preferably the same solvent used in the high purity hafnium process, to extract zirconium from the feed into the solvent, and to leave a raffinate which has a greater ratio of hafniurmzirconium than the initial feed. This raffinate can then be used as the feed for the high purity hafnium process described above. The zirconium loaded solvent can then be subjected to an acid scrub to remove coextracted hafnium and to produce a zirconium loaded solvent with very little to no hafnium content. This dehafniated zirconium solvent can then be stripped to produce a high purity (dehafniated) zirconium strip, from which high purity zirconium products can be extracted through precipitation or other known methods. The stripped solvent may be regenerated and reprotonated in a similar manner as in the high purity hafnium process. Because the same solvent is used in both processes, the stripped solvents may be combined and regenerated and optionally reprotonated at the same time and using the same equipment, reducing the overall cost of the process and the size of the system required to carry it out.

[0052] The present disclosure will become better understood from the following example of a non-limiting embodiment.

[0053] FIGURE 1 shows a schematic process diagram for an embodiment of the present invention. The large dashed box represents the dehafniated zirconium process, and the large dotted area represents the high purity hafnium process. As will be explained in greater detail below, the two processes in this embodiment share common elements, and as a result the boxes representing the two processes overlap.

[0054] Initially, a feed comprising an acidic sulfate based solution including zirconium and hafnium 1 is fed into an extraction circuit 2. The feed 1 may be created by applying conventional unit processes known in the industry to zirconium ores and concentrates. For example, zircon concentrate can undergo caustic fusion to remove silica followed by sulfuric acid dissolution to produce the acidic sulfate based solution. Alternatively, an intermediate zirconium based chemical such as zirconium basic carbonate can be dissolved in sulfuric acid, or zirconium oxychloride may be dissolved in water and the zirconium reprecipitated as zirconium basic sulfate before being dissolved in sulfuric acid, or any other known method of producing such a feed. The feed preferably has a hafnium: zirconium weight ratio in line with the amounts typically found in naturally occurring zirconium ores and concentrates. When expressed as Hf/(Zr+Hf), these amounts are typically between 0.5-3%.

[0055] In the extraction circuit 2, the feed 1 is counter-currently contacted with a solvent 3. The solvent is an amine based reagent which is capable of extracting zirconium from the feed and rejecting hafnium. Many such amine based reagents are known and would be suitable for use in this process. This circuit produces a zirconium loaded solvent 4 as well as a relatively hafnium rich raffinate 5 compared to the initial feed 1.

[0056] The zirconium loaded solvent 4 then proceeds to an acid scrub circuit 6 where the solvent is scrubbed with H2SO4, the main purpose of which is to remove any co-extracted hafnium from the solvent 4. The scrub circuit raffinate 7 in this embodiment is recycled into the extraction circuit where the previously co-extracted hafnium can report to the raffinate 5. The now dehafniated solvent 8 proceeds to a strip circuit 9 where it is contacted with a NaCl strip 10 to transfer the dehafniated zirconium from the solvent 8 to a loaded strip 11. The loaded strip 11 can then be subjected to further zirconium recovery processes such as but not limited to precipitating intermediate zirconium metal complexes to form zirconium products. In this embodiment, the strip circuit 9 also includes a strip recycle 12 which allows part of the loaded strip to be used as part of the scrub circuit feed.

[0057] The stripped solvent 13 proceeds to a regeneration circuit 14 where it is regenerated with an alkali solution, which in this embodiment is a mixture of Na2COs and NaOH. In this embodiment, the regenerated solvent 15 is also reprotonated with H2SO4 in a reprotonation circuit 16 before being reused in the extraction circuit 2.

[0058] The raffinate 5 from the extraction circuit 2, which is relatively high in hafnium compared with the initial feed, proceeds to a pretreatment step (small dashed box) which comprises a nanofiltration stage 17, a precipitation and re-dissolution stage 18 and a heat pretreatment step 21. In this embodiment, the heat pretreatment step is carried out following the concentration step, however it will be understood that these steps can be done in any order without departing from the spirit of the invention. It will also be understood that in other embodiments, a feed which is relatively high in hafnium compared with naturally occurring ores and concentrates which is not a raffinate from a dehafniated zirconium process may be used instead, and the following process used in isolation to produce a high purity hafnium stream.

[0059] In this embodiment, the concentration step is carried out through nanofiltration, which allows the smaller bisulfate ions to pass through a membrane to a permeate 19 while the larger zirconium and hafnium ions, are rejected by the membrane and remain in the retentate

20, which proceeds to the precipitation and re-dissolution step 18 and then heat treatment step

21. The heat pre-treatment step 21 involves heating the retentate to a temperature above about 50°C and below 100°C, preferably to about 98°C. The permeate 19 is H2SO4 and may be reused throughout the process where EfoSC s used.

[0060] The retentate then proceeds to an extraction circuit 22 which is similar to the first extraction circuit 2 in that the feed is counter currently contacted with the same amine based reagent as in the first extraction circuit 2. This produces a raffinate 23 which is high in hafnium and extremely low in zirconium, and which can be further processed by any known methods to produce hafnium products such as through the precipitation of intermediate hafnium metal complexes.

[0061] The loaded zirconium solvent 24 then proceeds to a strip circuit 25 where it is contacted with NaCl to produce a secondary zirconium loaded strip 26 which can be processed similarly to the first zirconium loaded strip 11. This zirconium loaded strip 26 is likely to include some hafnium which is co-extracted with the zirconium and thus will be a lower purity stream relative to the first zirconium loaded strip. The stripped solvent 27 can then be regenerated and reprotonated by the same circuits 14 and 16 as for the first strip circuit 9 owing to the same solvent being used in both processes.

[0062] FIGURE 2 shows an alternative process diagram, where the same reference numerals have been retained for identical components. This embodiment differs in that the dehafniated zirconium process and high purity hafnium process (indicated by the large dashed box and large dotted box respectively) have their own separate regeneration and reprotonation circuits. This embodiment may be beneficial, for example, when the two processes are carried out in separate locations from each other. Specifically, the stripped solvent 13 of the dehafniated zirconium process proceeds to regeneration circuit 28 and reprotonation circuit 29 while the stripped solvent 27 of the high purity hafnium process proceeds to regeneration circuit 30 and reprotonation circuit 31. FIGURE 2 also differs from the process diagram shown in FIGURE 1 in that only a nanofiltration step 17 is carried out on the raffinate 5. It will be understood that in other embodiments, the nanofiltration step 17 may be used in conjunction with a precipitation and re-dissolution concentration step as shown in FIGURE 1, or alternatively in further embodiments, the nanofiltration step may be replaced with a precipitation and re-dissolution step. In other embodiments, other known methods of concentrating a solution may be used in place of or in conjunction with these steps.

[0063] To characterize the ability of the present invention to separate hafnium and zirconium to produce high purity streams, the inventors continuously tested a dehafniated zirconium process in accordance with the embodiment shown in FIGURE 2 and measured the compositions of the feed, raffinate and produced product stream. The results are tabulated below:

[0064] These results show that a very pure (low amounts of hafnium) zirconium product is produced by the process, and that the raffinate which reports to the high purity hafnium stream has an increased weight ratio of hafniurmzirconium compared with the initial feed.

[0065] The effect of the concentration step (in the form of nanofiltration) on the resultant zirconium extraction from the raffinate was also examined. The concentrations of zirconium, hafnium and sulfuric acid in the feed, permeate and retentate are tabulated below:

[0066] The effect of increasing the concentration of zirconium and hafnium in the feed for the high purity hafnium process is that the extraction circuit can operate at higher loading in the solvent compared to feeds which haven't undergone a concentration process. This relationship is illustrated in FIGURE 3, which shows the equilibrium curve for zirconium loading onto the solvent (organic phase).

[0067] The effect of the heat treatment step was examined by comparing the equilibrium curves of a heat treated feed and a non-heat treated feed. The heat treated feed was heated to a temperature of about 98°C for 4 hours. In both cases this feed was the raffinate from a zirconium extraction process according to the process diagram of FIGURE 2. The results are shown in FIGURE 4. The heat treated feed, 32 with open symbols, is closer to the y-axis than the non-heat treated feed 33 with closed symbols, indicating that zirconium can be more effectively extracted from the aqueous feed. The effective extraction of zirconium in the high purity hafnium process is essential in producing a hafnium stream which produces high purity hafnium and thus the heat treatment step allows for a higher purity hafnium product stream. [0068] Referring again to FIGURE 4, it can be seen that the zirconium concentration of the non-heat treated aqueous feed 32 cannot be reduced below concentrations of around 50 mg/L. In contrast, the heat treated feed 33 enables concentrations lower than 10 mg/L zirconium. This enables zirconium in the raffinate to be removed to produce a raffinate with relatively high amounts of hafnium and little to no zirconium.

[0069] The concentrations of zirconium in the raffinate for heat treated and non-heat treated feeds following solvent extraction were also investigated. The non-heat treated feed raffinate included ~65 mg/L zirconium while the heat-treated raffinate was reduced to ~5 mg/L zirconium. The zirconium extraction improved from <99.0% without heat treatment to about 99.8-99.9% with heat treatment of the feed. Accordingly, a high purity hafnium stream could be established from the raffinate.

[0070] In the foregoing description of certain embodiments, specific terminology has been resorted to for the sake of clarity. However, the disclosure is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes other technical equivalents which operate in a similar manner to accomplish a similar technical purpose.

[0071] In this specification, the word “comprising” is to be understood in its “open” sense, that is, in the sense of “including”, and thus not limited to its “closed” sense, that is the sense of “consisting only of’. A corresponding meaning is to be attributed to the corresponding words “comprise”, “comprised” and “comprises” where they appear.

[0072] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as, an acknowledgement or admission or any form of suggestion that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

[0073] In addition, the foregoing describes only some embodiments of the invention(s), and alterations, modifications, additions and/or changes can be made thereto without departing from the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not restrictive. [0074] Furthermore, invention(s) have described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention(s). Also, the various embodiments described above may be implemented in conjunction with other embodiments, e.g., aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. Further, each independent feature or component of any given assembly may constitute an additional embodiment.

Claims (29)

The claims defining the invention are as follows:

1. A process for separating hafnium and zirconium, including the steps of: concentrating an acidic sulfate based solution containing zirconium and hafnium, the solution having a hafniurmzirconium weight ratio as given by Hf/(Hf+Zr) greater than the typical weight ratio of naturally occurring zirconium ores and/or concentrates; heating the solution; contacting the solution with an amine based solvent to create a hafnium rich rafinate and a zirconium loaded solvent; and stripping the zirconium loaded solvent to produce a stripped solvent and a zirconium loaded strip.

2. The process of claim 1 wherein the hafnium: zirconium weight ratio of the solution is greater than 3%.

3. The process of any one of claims 1 or 2, wherein concentrating the acidic sulfate based solution includes subjecting the solution to a nanofiltration process.

4. The process according to claim 3, wherein a sulfuric acid permeate produced by the nanofiltration process is recovered for reuse in the process.

5. The process of any one of claims 1 to 4, wherein concentrating the acidic sulfate based solution includes precipitating zirconium and hafnium solids from the solution and redissolving said solids in a smaller volume of solution.

6. The process of any one of the preceding claims, further including: contacting the stripped solvent with an alkali solution to produce a regenerated solvent which can then be reused in the process.

7. The process of claim 6, wherein the alkali solution is sodium carbonate or a mixture of sodium carbonate and sodium hydroxide.

8. The process of either claim 6 or 7, further including: reprotonating the regenerated solvent prior to reuse in the process.

9. The process of claim 8, wherein the reprotonation is carried out using sulfuric acid.

10. The process of any one of the preceding claims, wherein stripping the zirconium loaded solvent comprises contacting said solvent with sodium chloride.

11. The process of any one of the preceding claims, wherein the acidic sulfate based solution is a raffinate produced by a zirconium solvent extraction process.

12. The process of claim 11, wherein the zirconium solvent extraction process which produces the raffinate includes contacting a zirconium containing feed with the amine based solvent, and solvent from the zirconium solvent extraction process is regenerated in a common regeneration circuit with the stripped solvent to form a common regenerated solvent for use in the process for separating hafnium and zirconium and the zirconium solvent extraction process.

13. The process of claim 12, further including reprotonating the common regenerated solvent.

14. The process of claim 13, wherein the reprotonation is carried out using sulfuric acid.

15. The process of any one of the preceding claims, wherein the solution is heated to a temperature above about 50°C and below about 100°C.

16. The process of any one of the preceding claims, further including recovering hafnium products from the hafnium rich raffinate.

17. The process of any one of the preceding claims, further including recovering zirconium products from the zirconium loaded solvent.

18. A pre-treatment process for an acidic sulfate based solution containing zirconium and hafnium prior to separating hafnium and zirconium, including: concentrating the acidic sulfate based solution; heating the acidic sulfate based solution.

19. The process of claim 18, wherein concentrating the acidic sulfate based solution comprises subjecting the solution to a nanofiltration process.

20. The process of either claim 18 or 19, wherein the acidic sulfate based solution is heated to a temperature above about 50°C and below about 100°C.

21. A system for separating zirconium and hafnium, including: a pre-treatment stage including: a concentration step which receives a feed containing zirconium and hafnium and increases the relative concentration of zirconium and hafnium in the feed; a heating step; an extraction circuit which receives the feed following the pre-treatment stage and contacts the feed with a solvent to form a zirconium loaded solvent and a hafnium rich raffinate; a stripping circuit which transfers zirconium from the zirconium loaded solvent to form a stripped solvent and a loaded strip; a regeneration circuit which at least partially removes chloride from the stripped solvent to form a regenerated solvent which can then be reused in the extraction circuit.

22. The system of claim 21 , further including a hafnium precipitation circuit for recovering hafnium from the hafnium rich raffinate.

23. The system of either claim 21 or 22, further including a zirconium precipitation circuit for recovering zirconium from the zirconium loaded solvent.

24. The system of any one of claims 21 to 23, further including a reprotonation circuit which receives regenerated solvent and reprotonates it prior to reuse in the system.

25. The system of any one of claims 21 to 24, wherein the feed containing zirconium and hafnium is a raffinate produced by a zirconium solvent extraction system.

26. The system of claim 25, wherein the zirconium solvent extraction system includes: a first extraction circuit, which receives a pregnant leach solution containing zirconium and hafnium and contacts the pregnant leach solution to form a raffinate which proceeds to the pre-treatment stage and a first zirconium loaded solvent;

17 an acid scrub circuit which receives the first zirconium loaded solvent and removes coextracted hafnium from the circuit to form a dehafniated zirconium loaded solvent; a first stripping circuit which transfers zirconium from the dehafniated zirconium loaded solvent to form a first stripped solvent and a dehafniated zirconium loaded strip.

27. The system of claim 26, wherein the first stripped solvent and the stripped solvent are fed to a common regeneration circuit which at least partially removes chloride from the stripped solvent to form a regenerated solvent which can be used in the first extraction circuit and the extraction circuit.

28. The system of either claim 26 or 27, further including a dehafniated zirconium precipitation circuit for recovering high purity zirconium from the dehafniated zirconium loaded strip.

29. The system of any one of claims 21 to 28, used to carry out a process according to any one of claims 1 to 17.

18