Method for separating zirconium and hafnium from zirconium and hafnium mixed salt and application of method in ore purification

Abstract

The invention relates to a method for separating zirconium and hafnium from zirconium and hafnium mixed salt and application of the method in ore purification, and the method comprises the following steps: (1) mixing the zirconium and hafnium mixed salt, ammonium thiocyanate, concentrated hydrochloric acid, organic acid and water to obtain a water phase; (2) sequentially carrying out mixing, oscillation and liquid-liquid separation on the thiocyanic acid aqueous solution and a ketone extraction agent to obtain an organic phase; (3) mixing and extracting the organic phase and the water phase, and performing phase splitting to obtain a hafnium-containing organic phase; the step (1) and the step (2) have no sequence. The organic acid in the water phase reacts with zirconium and hafnium to form a complex, and the affinity of the extraction reaction of zirconium and hafnium with the ketone extraction agent is respectively changed, so that the separation selectivity of the ketone extraction agent on hafnium is improved, and the separation coefficient of the system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of zirconium and hafnium separation, and particularly to a method for separating zirconium and hafnium from a zirconium and hafnium mixed salt and its application in ore purification. Background Art

[0002] Zirconium and hafnium are homologous elements, and their properties and appearances are extremely similar. Their valences are both +2, +3, and +4, and the +4 valence is the most stable in compounds. A dense oxide film is easily formed on the surfaces of zirconium and hafnium, and their chemical properties are stable at room temperature. They are insoluble in dilute sulfuric acid, dilute hydrochloric acid, and strong bases, and can only be dissolved in aqua regia and hydrofluoric acid. The content of zirconium in the earth's crust is much higher than that of some common non-ferrous metals such as copper, lead, nickel, and zinc, while hafnium is a trace element, accounting for only 1-3% of the total amount of zirconium and hafnium. Zirconium and hafnium generally coexist in minerals such as zircon (ZrSiO4) and baddeleyite (ZrO2). Therefore, zirconium compounds often contain a small amount of hafnium. Zirconium and hafnium have almost the same atomic and ionic radii and similar valence electron configurations, making their chemical properties very similar and separation extremely difficult.

[0003] The solvent extraction method is the main method for separating zirconium and hafnium used in industry at present. The solvent extraction method, also known as the liquid-liquid extraction method, is a separation technology that utilizes liquid-liquid distribution equilibrium, and has the advantages of high separation efficiency, strong selectivity, large production capacity, wide adaptability, simple process, environmental protection, etc. Currently, the extraction systems that are relatively mature and applied in industry include the MIBK-HSCN system, the TOA / N235-H2SO4 system, the TBP-HNO3-HCl system, etc.

[0004] The extraction systems currently used in industry all have many disadvantages. In the MIBK-HSCN system, MIBK is volatile, toxic, and has a low separation coefficient, and HSCN is easily decomposed; in the TOA / N235-H2SO4 system, TOA is easily emulsified, H2SO4 has strong corrosiveness and is easy to corrode equipment; the TBP-HNO3-HCl system has a small extraction capacity, and TBP is easily emulsified. Among these three systems, only the MIBK-HSCN system is an extraction system that preferentially extracts hafnium and is also the most widely used extraction system.

[0005] CN102706871A discloses a method for determining zirconium and hafnium components in zirconium compounds by extraction photometry. Specifically, the preparation methods of the aqueous phase and the organic phase in the system are as follows: Prepare a 2.0 - 4.0 mo1 / L HSCN solution by reacting ammonium thiocyanate with inorganic acid. Add MIBK and HSCN to a beaker in a volume ratio of 1:1. Under the condition that the interfacial stirring speed is 80 - 300 r / min, after saturation for 5 - 30 min, separate the liquid. The upper layer is the organic phase. Additionally, prepare a measured material solution with a zirconium concentration not greater than 2.0 mo1 / L and a thiocyanic acid concentration of 2.0 - 4.0 mol / L as the aqueous phase. The organic phase is directly obtained by reacting MIBK and HSCN. Among them, MIBK is volatile and toxic, and HSCN is easily decomposed, and the separation coefficient is relatively low.

[0006] In summary, it is necessary to develop a method for separating zirconium and hafnium, improve the disadvantages of the MIBK - HSCN system to increase the separation effect, which is of great significance for the purification of hafnium in industry and the development of the nuclear power industry. Summary of the Invention

[0007] To solve the above technical problems, the present invention provides a method for separating zirconium and hafnium from a zirconium - hafnium mixed salt. By adding an organic acid to the aqueous phase, the organic acid reacts with zirconium and hafnium to form complexes, respectively changing the affinity of the extraction reaction of zirconium and hafnium with a ketone extractant, thereby improving the separation selectivity of the ketone extractant for hafnium and increasing the separation coefficient of the system.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a method for separating zirconium and hafnium from a zirconium - hafnium mixed salt, and the method includes the following steps:

[0010] (1) Mix the zirconium - hafnium mixed salt, ammonium thiocyanate, concentrated hydrochloric acid, organic acid and water to obtain an aqueous phase;

[0011] (2) Mix, oscillate and perform liquid - liquid separation on the aqueous solution of thiocyanic acid and the ketone extractant in sequence to obtain an organic phase;

[0012] (3) Mix and extract the organic phase and the aqueous phase and separate the phases to obtain an organic phase containing hafnium;

[0013] There is no sequence requirement between step (1) and step (2).

[0014] The aqueous phase used in the extraction reaction of the present invention comprises a zirconium-hafnium mixed salt, ammonium thiocyanate, concentrated hydrochloric acid and an organic acid. The organic acid can react with zirconium and hafnium to form complexes, respectively changing the affinity of the extraction reaction of zirconium and hafnium with the ketone extractant, thereby improving the separation selectivity of the ketone extractant for hafnium and increasing the separation coefficient of the system. At the same time, the addition of concentrated hydrochloric acid can not only adjust the acidity of the solution but also promote the complexation of zirconium and hafnium with thiocyanate ions and promote the reaction of the organic acid with zirconium and hafnium to form complexes. That is, ammonium thiocyanate and the organic acid in the aqueous phase can act synergistically under acidic conditions to jointly promote the separation of zirconium and hafnium. Further, the extraction system of the present invention can preferentially extract hafnium with a lower content, and an organic phase containing hafnium is obtained after the extraction reaction to better realize the separation of zirconium and hafnium.

[0015] As a preferred technical solution of the present invention, in the zirconium-hafnium mixed salt in step (1), the zirconium comprises ZrOCl2·8H2O and / or ZrCl4.

[0016] Preferably, the hafnium in the zirconium-hafnium mixed salt comprises HfOCl2·8H2O and / or HfCl4.

[0017] Preferably, the total concentration of zirconium and hafnium ions in the aqueous phase is 0.005 - 2 mol / dm 3 , for example, it can be 0.005 mol / dm 3 , 0.01 mol / dm 3 , 0.1 mol / dm 3 , 0.5 mol / dm 3 , 1 mol / dm 3 or 2 mol / dm 3 , but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0018] Preferably, the mass ratio of hafnium to zirconium in the aqueous phase is (0.005 - 0.25):1. For example, it can be 0.005:1, 0.01:1, 0.05:1, 0.1:1, 0.15:1, 0.2:1 or 0.25:1, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0019] By limiting the mass ratio of hafnium to zirconium in the aqueous phase, the present invention can enable the extractant to effectively combine with hafnium ions, reduce the interference of zirconium ions, increase the separation effect, and improve the purity of the zirconium-containing and hafnium-containing products after separation. If the content of hafnium in the aqueous phase is too high, it will increase the difficulty of separation, reduce the separation efficiency, and at the same time, due to the excessive content of hafnium, if hafnium is not completely removed, it will affect the purity and performance of the final product.

[0020] As a preferred technical solution of the present invention, the concentration of ammonium thiocyanate in the aqueous phase in step (1) is 0.05 - 5 mol / dm 3 , for example, it can be 0.05 mol / dm 3 , 0.1 mol / dm 3 , 1 mol / dm 3 , 2 mol / dm 3 , 3 mol / dm 3 , 4 mol / dm 3 or 5 mol / dm 3 , but it is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0021] By limiting the concentration of ammonium thiocyanate in the aqueous phase in step (1) to 0.05 - 5 mol / dm 3 , ammonium thiocyanate can form a stable complex with zirconium and hafnium, ensuring that its reaction with zirconium and hafnium proceeds at an appropriate stoichiometric ratio, reducing the separation cost, and improving the extraction efficiency; if the concentration of ammonium thiocyanate is too small, the number of complexes formed with zirconium and hafnium will decrease, resulting in a reduction in extraction efficiency, which means that more hafnium will remain in the aqueous phase rather than being extracted into the organic phase. If the desired extraction efficiency is to be achieved, the amount of extractant used will be increased to compensate for the insufficient concentration of ammonium thiocyanate; if the concentration of ammonium thiocyanate is too large, the decomposition rate of ammonium thiocyanate will increase, generating a solid third phase, affecting the normal progress of the extraction process.

[0022] Preferably, the concentration of concentrated hydrochloric acid in the aqueous phase in step (1) is 0.2 - 5 mol / dm 3 , for example, it can be 0.2 mol / dm 3 , 0.5 mol / dm 3 , 1 mol / dm 3 , 3 mol / dm 3 or 5 mol / dm 3 , but it is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0023] Preferably, the organic acid includes any one or a combination of at least two of glycine, ascorbic acid, citric acid, sodium ethylenediaminetetraacetate, or oxalic acid. Typical but non-limiting combinations include: a combination of glycine and ascorbic acid, a combination of glycine and citric acid, a combination of glycine and sodium ethylenediaminetetraacetate, a combination of glycine and oxalic acid, a combination of ascorbic acid and citric acid, a combination of ascorbic acid and sodium ethylenediaminetetraacetate, a combination of ascorbic acid and oxalic acid, a combination of citric acid and sodium ethylenediaminetetraacetate, a combination of citric acid and oxalic acid, a combination of sodium ethylenediaminetetraacetate and oxalic acid, a combination of glycine, ascorbic acid and citric acid, a combination of glycine, ascorbic acid and sodium ethylenediaminetetraacetate, a combination of glycine, ascorbic acid and oxalic acid, a combination of glycine, citric acid and sodium ethylenediaminetetraacetate, a combination of glycine, citric acid and oxalic acid, a combination of glycine, sodium ethylenediaminetetraacetate and oxalic acid, a combination of ascorbic acid, citric acid and sodium ethylenediaminetetraacetate, a combination of ascorbic acid, citric acid and oxalic acid, a combination of ascorbic acid, sodium ethylenediaminetetraacetate and oxalic acid, a combination of citric acid, sodium ethylenediaminetetraacetate and oxalic acid, a combination of glycine, ascorbic acid, citric acid and sodium ethylenediaminetetraacetate, a combination of glycine, ascorbic acid, citric acid and oxalic acid, a combination of glycine, ascorbic acid, sodium ethylenediaminetetraacetate and oxalic acid, a combination of glycine, citric acid, sodium ethylenediaminetetraacetate and oxalic acid, a combination of ascorbic acid, citric acid, sodium ethylenediaminetetraacetate and oxalic acid, a combination of glycine, ascorbic acid, citric acid, sodium ethylenediaminetetraacetate and oxalic acid.

[0024] Preferably, the concentration of the organic acid in the aqueous phase is 0.001 - 1 mol / dm 3 , for example, it can be 0.001 mol / dm 3 , 0.01 mol / dm 3 , 0.1 mol / dm 3 , 0.5 mol / dm 3 or 1 mol / dm 3 , but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0025] In the present invention, an organic acid is added to the aqueous phase. The organic acid can react with zirconium and hafnium to form complexes. The stability and solubility of these complexes during the extraction process will affect the extraction efficiency. By limiting the type and concentration of the organic acid, the properties of the complexes can be optimized, thereby improving the extraction efficiency and the separation coefficient of the system. At the same time, limiting the type of organic acid can preferentially extract hafnium with a lower content, and better separate zirconium and hafnium.

[0026] As a preferred technical solution of the present invention, the ketone extractant includes methyl isobutyl ketone and / or diisobutyl ketone, preferably methyl isobutyl ketone.

[0027] The present invention uses kerosene to dilute a ketone extractant, and the volume fraction of the ketone extractant in kerosene is 1-100%, for example, it can be 1%, 10%, 30%, 50%, 75% or 100%, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0028] Preferably, the preparation of the aqueous thiocyanate solution in step (2) includes: mixing an ammonium thiocyanate solution and concentrated hydrochloric acid to obtain an aqueous thiocyanate solution.

[0029] Preferably, the concentration of thiocyanate ions in the aqueous thiocyanate solution in step (2) is 0.001-5 mol / dm 3 , for example, it can be 0.001 mol / dm 3 , 0.01 mol / dm 3 , 0.1 mol / dm 3 , 1 mol / dm 3 , 3 mol / dm 3 or 5 mol / dm 3 , but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0030] Preferably, the concentration of chloride ions in the aqueous thiocyanate solution in step (2) is 0.01-3 mol / dm 3 , for example, it can be 0.01 mol / dm 3 , 0.1 mol / dm 3 , 1 mol / dm 3 , 2 mol / dm 3 or 3 mol / dm 3 , but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0031] As a preferred technical solution of the present invention, the volume ratio of the aqueous thiocyanate solution to the ketone extractant in step (2) is (0.2-5):1, for example, it can be 0.2:1, 0.5:1, 1:1, 2:1, 3:1, 4:1 or 5:1, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0032] Preferably, the oscillation time in step (2) is 1-3 min, for example, it can be 1 min, 1.5 min, 2 min, 2.5 min or 3 min, but is not limited to the listed values, and other unlisted values within the above value range are equally applicable.

[0033] Preferably, the oscillation speed in step (2) is 100 - 300 r / min. For example, it can be 100 r / min, 150 r / min, 200 r / min, 250 r / min, or 300 r / min. However, it is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0034] As a preferred technical solution of the present invention, the volume ratio of the organic phase to the aqueous phase in step (3) is (0.25 - 4):1. For example, it can be 0.25:1, 0.5:1, 1:1, 2:1, 3:1, or 4:1. However, it is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0035] Preferably, the mixing extraction in step (3) is carried out during oscillation.

[0036] Preferably, the oscillation time in the mixing extraction is 15 - 20 min. For example, it can be 15 min, 16 min, 17 min, 18 min, 19 min, or 20 min. However, it is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0037] Preferably, the oscillation speed in the mixing extraction is 100 - 300 r / min. For example, it can be 100 r / min, 150 r / min, 200 r / min, 250 r / min, or 300 r / min. However, it is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0038] Preferably, the temperature of the mixing extraction is 0 - 40 °C. For example, it can be 0 °C, 5 °C, 10 °C, 20 °C, or 40 °C. However, it is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0039] As a preferred technical solution of the present invention, the method further includes: mixing and back-extracting the hafnium-containing organic phase with the back-extraction liquid and separating the phases to obtain an aqueous solution containing hafnium ions.

[0040] Preferably, the back-extraction liquid includes an aqueous hydrochloric acid solution.

[0041] Preferably, the concentration of hydrochloric acid in the back-extraction liquid is 0.5 - 5 mol / dm 3 , for example, it can be 0.5 mol / dm 3 , 1 mol / dm 3 , 2 mol / dm 3 , 3 mol / dm 3 , 4 mol / dm 3 or 5 mol / dm 3, but not limited to the listed values, other unlisted values within the above value range are equally applicable.

[0042] As a preferred technical solution of the present invention, the volume ratio of the hafnium-containing organic phase to the stripping solution is (0.25 - 4):1. For example, it can be 0.25:1, 0.5:1, 1:1, 2:1, or 4:1, but not limited to the listed values. Other unlisted values within the above value range are equally applicable.

[0043] Preferably, the temperature of the mixed stripping is 0 - 40°C. For example, it can be 0°C, 5°C, 10°C, 20°C, or 40°C, but not limited to the listed values. Other unlisted values within the above value range are equally applicable.

[0044] Preferably, the oscillation time in the mixed stripping is 15 - 20 min. For example, it can be 15 min, 16 min, 17 min, 18 min, 19 min, or 20 min, but not limited to the listed values. Other unlisted values within the above value range are equally applicable.

[0045] Preferably, the oscillation speed in the mixed stripping is 100 - 300 r / min. For example, it can be 100 r / min, 150 r / min, 200 r / min, 250 r / min, or 300 r / min, but not limited to the listed values. Other unlisted values within the above value range are equally applicable.

[0046] As a preferred technical solution of the present invention, the method includes the following steps:

[0047] (1) Mix a zirconium-hafnium mixed salt with a mass ratio of hafnium to zirconium of (0.005 - 0.25):1, ammonium thiocyanate, concentrated hydrochloric acid, organic acid, and water to obtain an aqueous phase, and the total concentration of zirconium and hafnium ions in the aqueous phase is 0.005 - 2 mol / dm 3 ;

[0048] (2) Mix an aqueous solution of ammonium thiocyanate and a ketone extractant in a volume ratio of (0.2 - 5):1, then oscillate and perform liquid-liquid separation to obtain an organic phase;

[0049] (3) Mix the organic phase and the aqueous phase at 0 - 40°C in a volume ratio of (0.25 - 4):1 for mixed extraction, and perform phase separation to obtain a hafnium-containing organic phase, and the separation factor of the mixed extraction is 5.00 - 7.00;

[0050] (4) Mix the hafnium-containing organic phase with a stripping solution at 0 - 40°C in a volume ratio of (0.25 - 4):1 for mixed stripping, and then perform phase separation to obtain an aqueous solution containing hafnium ions.

[0051] In a second aspect, the present invention provides an application of the method for separating zirconium and hafnium from the zirconium-hafnium mixed salt according to the first aspect in ore purification.

[0052] Zirconium and hafnium generally coexist in minerals such as zircon (ZrSiO4) and baddeleyite (ZrO2). Zirconium compounds often contain a small amount of hafnium. Zirconium and hafnium belong to the same group of elements, having almost the same atomic and ionic radii and similar valence electron configurations, making their chemical properties very similar and separation extremely difficult. The method for separating zirconium and hafnium from the zirconium-hafnium mixed salt according to the first aspect of the present invention can separate zirconium and hafnium in the ore to purify zirconium and hafnium in the ore, so that the purified zirconium and hafnium materials can be applied in fields such as aerospace, nuclear industry, and electronic industry.

[0053] Compared with the prior art, the present invention has at least the following beneficial effects:

[0054] In the aqueous phase of extraction of the present invention, ammonium thiocyanate, concentrated hydrochloric acid, and organic acid are added. The organic acid can react with zirconium and hafnium to form complexes, respectively changing the affinity of the extraction reaction of zirconium and hafnium with the ketone extractant, thereby improving the separation selectivity of the ketone extractant for hafnium and increasing the separation coefficient of the system. The addition of concentrated hydrochloric acid can not only adjust the acidity of the solution but also promote the complexation of zirconium and hafnium with thiocyanate ions and promote the reaction of the organic acid with zirconium and hafnium to form complexes. That is, ammonium thiocyanate and organic acid in the aqueous phase can act synergistically under acidic conditions to jointly promote the separation of zirconium and hafnium. Preferably, the separation coefficient in the extraction of the present invention can reach more than 5.00. Detailed implementation manners

[0055] To facilitate the understanding of the present invention, the following examples are listed. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0056] Example 1

[0057] This example provides a method for separating zirconium and hafnium from a zirconium-hafnium mixed salt. The method includes the following steps:

[0058] (1) The zirconium-hafnium mixed salt is composed of ZrOCl2·8H2O and HfOCl2·8H2O. The mass ratio of hafnium to zirconium in the zirconium-hafnium mixed salt is 0.02:1. The zirconium-hafnium mixed salt, ammonium thiocyanate, 38% concentrated hydrochloric acid, glycine, and water are mixed to obtain an aqueous phase. The total concentration of zirconium and hafnium ions in the aqueous phase is 0.5 mol / dm 3 The concentration of ammonium thiocyanate is 3 mol / dm 3 The concentration of concentrated hydrochloric acid is 1 mol / dm 3 The concentration of glycine is 0.25 mol / dm 3 ;

[0059] (2) React ammonium thiocyanate solution with 38% concentrated hydrochloric acid to obtain an aqueous solution of thiocyanic acid, wherein the concentration of thiocyanate ions in the aqueous solution of thiocyanic acid is 2 mol / dm 3 , and the concentration of chloride ions is 2 mol / dm 3 . Dilute methyl isobutyl ketone with kerosene to make the volume fraction of methyl isobutyl ketone 50%. Mix the aqueous solution of thiocyanic acid with methyl isobutyl ketone with a volume fraction of 50% according to a volume ratio of 4:1, then oscillate at 250 r / min for 2 min, and perform liquid-liquid separation to obtain an organic phase;

[0060] (3) Mix the organic phase and the aqueous phase for extraction at 25 °C according to a volume ratio of 1:1. The mixing extraction is oscillated at 250 r / min for 18 min, and phase separation is performed to obtain an organic phase containing hafnium;

[0061] (4) Mix the organic phase containing hafnium with a hydrochloric acid aqueous solution of 2 mol / dm 3 for back extraction at 25 °C according to a volume ratio of 0.5:1. The mixing back extraction is oscillated at 250 r / min for 17 min, and phase separation is performed to obtain an aqueous solution containing hafnium ions;

[0062] There is no order of precedence between step (1) and step (2);

[0063] In this example, the Hf / Zr separation coefficient is 7.00.

[0064] Example 2

[0065] This example provides a method for separating zirconium and hafnium from a zirconium-hafnium mixed salt, and the method includes the following steps:

[0066] (1) The zirconium-hafnium mixed salt is composed of ZrCl4 and HfCl4, and the mass ratio of hafnium to zirconium in the zirconium-hafnium mixed salt is 0.005:1. Mix the zirconium-hafnium mixed salt, ammonium thiocyanate, 38% concentrated hydrochloric acid, ascorbic acid and water to obtain an aqueous phase, and the total concentration of zirconium and hafnium ions in the aqueous phase is 0.005 mol / dm 3 , the concentration of ammonium thiocyanate is 0.05 mol / dm 3 , the concentration of concentrated hydrochloric acid is 0.2 mol / dm 3 , and the concentration of ascorbic acid is 0.001 mol / dm 3 ;

[0067] (2) React ammonium thiocyanate solution with 38% concentrated hydrochloric acid to obtain an aqueous solution of thiocyanic acid, wherein the concentration of thiocyanate ions in the aqueous solution of thiocyanic acid is 0.001 mol / dm 3 , and the concentration of chloride ions is 0.01 mol / dm 3, dilute diisobutyl ketone with kerosene to make the volume fraction of diisobutyl ketone 1%, mix the aqueous solution of thiocyanic acid and diisobutyl ketone with a volume fraction of 1% according to a volume ratio of 0.2:1, then oscillate at 100 r / min for 3 min, and perform liquid-liquid separation to obtain the organic phase;

[0068] (3) Mix and extract the organic phase and the aqueous phase at 0 °C according to a volume ratio of 4:1. The mixing extraction is oscillated at 100 r / min for 20 min, and phase separation is performed to obtain the hafnium-containing organic phase;

[0069] (4) Mix and back-extract the hafnium-containing organic phase with a 0.5 mol / dm 3 hydrochloric acid aqueous solution at 40 °C according to a volume ratio of 4:1. The mixing back-extraction is oscillated at 300 r / min for 15 min, and phase separation is performed to obtain an aqueous solution containing hafnium ions;

[0070] There is no order difference between step (1) and step (2);

[0071] In this example, the Hf / Zr separation coefficient is 5.46.

[0072] Example 3

[0073] This example provides a method for separating zirconium and hafnium from a zirconium-hafnium mixed salt. The method includes the following steps:

[0074] (1) The zirconium-hafnium mixed salt is composed of ZrOCl2·8H2O and HfCl4. The mass ratio of hafnium to zirconium in the zirconium-hafnium mixed salt is 0.25:1. Mix the zirconium-hafnium mixed salt, ammonium thiocyanate, 38% concentrated hydrochloric acid, sodium ethylenediaminetetraacetate and water to obtain an aqueous phase. The total concentration of zirconium and hafnium ions in the aqueous phase is 2 mol / dm 3 , the concentration of ammonium thiocyanate is 5 mol / dm 3 , the concentration of concentrated hydrochloric acid is 5 mol / dm 3 , and the concentration of sodium ethylenediaminetetraacetate is 1 mol / dm 3 ;

[0075] (2) React ammonium thiocyanate solution with 38% concentrated hydrochloric acid to obtain an aqueous solution of thiocyanic acid, in which the concentration of thiocyanate ions in the aqueous solution of thiocyanic acid is 5 mol / dm 3 , the concentration of chloride ions is 3 mol / dm 3 , mix the aqueous solution of thiocyanic acid and pure methyl isobutyl ketone according to a volume ratio of 5:1, then oscillate at 300 r / min for 1 min, and perform liquid-liquid separation to obtain the organic phase;

[0076] (3) Mix and extract the organic phase and the aqueous phase at 40 °C in a volume ratio of 0.25:1. The mixing extraction is oscillated at 300 r / min for 15 min, and then phase separation is carried out to obtain the hafnium-containing organic phase;

[0077] (4) Mix and strip the hafnium-containing organic phase and the hydrochloric acid aqueous solution with a concentration of 5 mol / dm 3 at 0 °C in a volume ratio of 0.25:1. The mixing stripping is oscillated at 100 r / min for 20 min, and then phase separation is carried out to obtain an aqueous solution containing hafnium ions;

[0078] There is no order of precedence between step (1) and step (2);

[0079] In this example, the Hf / Zr separation coefficient is 5.00.

[0080] Example 4

[0081] This example provides a method for separating zirconium and hafnium from a zirconium-hafnium mixed salt. The difference from Example 1 is only that, except that the total concentration of zirconium and hafnium ions in the aqueous phase in step (1) is 3 mol / dm 3 the rest are the same as in Example 1. In this example, the Hf / Zr separation coefficient is 3.66.

[0082] Example 5

[0083] This example provides a method for separating zirconium and hafnium from a zirconium-hafnium mixed salt. The difference from Example 1 is only that, except that the concentration of ammonium thiocyanate in the aqueous phase in step (1) is 0.01 mol / dm 3 the rest are the same as in Example 1. In this example, the Hf / Zr separation coefficient is 3.14.

[0084] Example 6

[0085] This example provides a method for separating zirconium and hafnium from a zirconium-hafnium mixed salt. The difference from Example 1 is only that, except that the concentration of ammonium thiocyanate in the aqueous phase in step (1) is 6 mol / dm 3 the rest are the same as in Example 1. In this example, the Hf / Zr separation coefficient is 4.33.

[0086] Example 7

[0087] This example provides a method for separating zirconium and hafnium from a zirconium-hafnium mixed salt. The difference from Example 1 is only that, except that glycine is replaced by salicylic acid, the rest are the same as in Example 1. In this example, the Hf / Zr separation coefficient is 4.75.

[0088] Example 8

[0089] This example provides a method for separating zirconium and hafnium from a zirconium-hafnium mixed salt. The difference from Example 1 is only that, except that the concentration of glycine in the aqueous phase is adjusted to 3 mol / dm 3 other than that, the rest are the same as in Example 1. The Hf / Zr separation coefficient in this example is 3.08.

[0090] Example 9

[0091] This example provides a method for separating zirconium and hafnium from a zirconium-hafnium mixed salt. The difference from Example 1 is only that, except that the methyl isobutyl ketone in step (2) is replaced by diisobutyl ketone, the rest are the same as in Example 1. The Hf / Zr separation coefficient in this example is 3.62.

[0092] Comparative Example 1

[0093] This comparative example provides a method for separating zirconium and hafnium from a zirconium-hafnium mixed salt. The difference from Example 1 is only that, except that glycine is not added to the aqueous phase, the rest are the same as in Example 1. The Hf / Zr separation coefficient in this comparative example is 3.78.

[0094] Comparative Example 2

[0095] This comparative example provides a method for separating zirconium and hafnium from a zirconium-hafnium mixed salt. The difference from Example 1 is only that, except that the extractant in the organic phase is replaced by bis(2-ethylhexyl) phosphate, and the aqueous solution of thiocyanic acid in the organic phase is adaptively replaced by an aqueous sulfuric acid solution with the same molar concentration, the rest are the same as in Example 1. The Hf / Zr separation coefficient in this comparative example is 4.33.

[0096] Use an inductively coupled plasma emission spectrometer to detect the concentrations of zirconium and hafnium in the hafnium-containing organic phase and the raffinate obtained after the extraction reaction, and calculate the separation coefficient of the extraction according to the formula β = (C A萃余有机相 / C A萃余水相 ) / (C B萃余有机相 / C B萃余水相 ), where C A萃取有机相 is the concentration of hafnium in the organic phase after extraction, with the unit of mol / dm 3 , C A萃余水相 is the concentration of hafnium in the aqueous phase after extraction, with the unit of mol / dm 3 , C B萃余有机相 is the concentration of zirconium in the raffinate organic phase, with the unit of mol / dm 3 , C B萃余水相 is the concentration of zirconium in the raffinate aqueous phase, with the unit of mol / dm 3 , and the test results are shown in the following table.

[0097] Table 1

[0098]

[0099] It can be seen from the test results that:

[0100] (1) It can be seen from Examples 1 to 3 that by adding an organic acid to the aqueous phase in the present invention, the organic acid reacts with zirconium and hafnium to form a complex, which respectively changes the affinity of the extraction reaction of zirconium and hafnium with the ketone extractant, thereby improving the separation selectivity of the ketone extractant for hafnium, increasing the separation coefficient of the system, and making the separation coefficient of extraction reach more than 5.00.

[0101] (2) It can be seen from Example 1 and Example 4 that the total concentration of zirconium and hafnium ions in the aqueous phase in step (1) of Example 1 is 0.5 mol / dm 3 , and the Hf / Zr separation coefficient of its system is 7.00; while the total concentration of zirconium and hafnium ions in the aqueous phase in step (1) of Example 4 is 3 mol / dm 3 , and the Hf / Zr separation coefficient of its system is 3.66. This shows that when the total concentration of hafnium ions in the aqueous phase is too high, it will change the complexation equilibrium in the extraction process, resulting in a decrease in the separation coefficient. That is, when separating zirconium and hafnium by the method for separating zirconium and hafnium in the zirconium-hafnium mixed salt provided by the present invention, it is necessary to control the total concentration of zirconium and hafnium ions in the aqueous phase within a specific range to achieve a better separation effect.

[0102] (3) It can be seen from Example 1 and Examples 5 - 6 that the concentration of ammonium thiocyanate in the aqueous phase in step (1) of Example 1 is 3 mol / dm 3 , and the Hf / Zr separation coefficient of its system is 7.00; while the concentration of ammonium thiocyanate in the aqueous phase in step (1) of Example 5 is 0.01 mol / dm 3 , and the Hf / Zr separation coefficient of its system is 3.14. The concentration of ammonium thiocyanate in the aqueous phase in step (1) of Example 6 is 6 mol / dm 3 , and the Hf / Zr separation coefficient of its system is 4.33. This shows that by limiting the concentration of ammonium thiocyanate in the aqueous phase described in step (1) to 0.05 - 5 mol / dm 3 in the present invention, ammonium thiocyanate can form a stable complex with zirconium and hafnium, ensuring that its reaction with zirconium and hafnium proceeds at an appropriate stoichiometric ratio, reducing the separation cost, and improving the extraction efficiency.

[0103] (4) It can be seen from Example 1 and Example 7 that the organic acid added to the aqueous phase in Example 1 is glycine, and the Hf / Zr separation factor of its system is 7.00; while the organic acid added to the aqueous phase in Example 7 is salicylic acid, and the Hf / Zr separation factor of its system is 4.75. This shows that when an organic acid is added to the aqueous phase in the present invention, the organic acid can react with zirconium and hafnium to form complexes, and the stability and solubility of these complexes during the extraction process will affect the extraction efficiency. By limiting the type of organic acid, the properties of the complexes can be optimized, thereby improving the extraction efficiency and the separation factor of the system. At the same time, limiting the type of organic acid can preferentially extract hafnium with a lower content, and can better achieve the separation of zirconium and hafnium.

[0104] (5) It can be seen from Example 1 and Example 8 that the concentration of glycine added to the aqueous phase in Example 1 is 0.25 mol / dm 3 , and the Hf / Zr separation factor of its system is 7.00; while the concentration of glycine added to the aqueous phase in Example 8 is 3 mol / dm 3 , and the Hf / Zr separation factor of its system is 3.08. This shows that when an organic acid is added to the aqueous phase in the present invention and the type and concentration of the organic acid are limited, the properties of the complexes can be optimized, thereby improving the extraction efficiency and the separation factor of the system.

[0105] (6) It can be seen from Example 1 and Example 9 that the ketone extractant used in step (2) of Example 1 is methyl isobutyl ketone, and the Hf / Zr separation factor of its system is 7.00; while the ketone extractant used in Example 9 is diisobutyl ketone, and the Hf / Zr separation factor of its system is 3.62. This shows that when the ketone extractant is diisobutyl ketone, the steric hindrance on the carbon adjacent to the carbonyl group will increase, which will hinder the combination of zirconium and hafnium with the ketone extractant, thereby reducing the separation factor of the system. That is, when separating zirconium and hafnium by the method for separating zirconium and hafnium from a zirconium-hafnium mixed salt provided by the present invention, a specific ketone extractant needs to be selected to have a better separation effect.

[0106] (7) It can be seen from Example 1 and Comparative Example 1 that in the present invention, by adding an organic acid to the aqueous phase, the organic acid can react with zirconium and hafnium to form complexes, respectively changing the affinity of the extraction reactions of zirconium and hafnium with the ketone extractant, thereby improving the separation selectivity of the ketone extractant for hafnium and increasing the separation factor of the system.

[0107] (8) It can be seen from Example 1 and Comparative Example 2 that in the present invention, by using a methyl isobutyl ketone - ammonium thiocyanate aqueous solution system to separate zirconium and hafnium, the difference between zirconium and hafnium is amplified, and the separation factor of the system is increased.

[0108] In summary, in the present invention, by optimizing the aqueous phase of the extraction reaction, a mixed salt of zirconium and hafnium, ammonium thiocyanate, concentrated hydrochloric acid, organic acid and water are mixed. The organic acid can react with zirconium and hafnium to form complexes, respectively changing the affinity of zirconium and hafnium for the extraction reaction with the ketone extractant, thereby improving the separation selectivity of the ketone extractant for hafnium and increasing the separation coefficient of the system. At the same time, the addition of concentrated hydrochloric acid can not only adjust the acidity of the solution but also promote the complexation of zirconium and hafnium with thiocyanate ions, and promote the reaction of the organic acid with zirconium and hafnium to form complexes. That is, ammonium thiocyanate and organic acid in the aqueous phase can act synergistically under acidic conditions to jointly promote the separation of zirconium and hafnium.

[0109] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for separating zirconium and hafnium from a zirconium and hafnium mixed salt, characterized in that: The method comprises the following steps: (1) mixing zirconium-hafnium mixed salt, ammonium thiocyanate, concentrated hydrochloric acid, an organic acid and water to obtain an aqueous phase; (2) sequentially mixing, shaking, and liquid-liquid separating the thiocyanate aqueous solution and the ketone extractant to obtain an organic phase; (3) extracting the organic phase and the aqueous phase by mixing and separating the phases to obtain an organic phase containing hafnium; There is no particular order in which steps (1) and (2) are performed.

2. The method according to claim 1, characterized in that The zirconium in the zirconium-hafnium mixed salt of step (1) includes ZrOCl2·8H2O and / or ZrCl4; Preferably, the hafnium in the zirconium-hafnium mixed salt comprises HfOCl2·8H2O and / or HfCl4; Preferably, the total concentration of zirconium and hafnium ions in the aqueous phase is 0.005-2 mol / dm 3 ; Preferably, the mass ratio of hafnium to zirconium in the aqueous phase is (0.005-0.25):

1.

3. The method according to claim 1 or 2, characterized in that: The concentration of ammonium thiocyanate in the aqueous phase of step (1) is 0.05-5 mol / dm 3 ; Preferably, the concentration of concentrated hydrochloric acid in the aqueous phase in step (1) is 0.2-5 mol / dm 3 ; Preferably, the organic acid comprises any one or a combination of at least two of glycine, ascorbic acid, citric acid, sodium ethylenediaminetetraacetate or oxalic acid; Preferably, the concentration of the organic acid in the aqueous phase is 0.001-1 mol / dm 3 .

4. The method according to any one of claims 1 to 3, characterized in that: The ketone extractant includes methyl isobutyl ketone and / or diisobutyl ketone, preferably methyl isobutyl ketone; Preferably, the preparation of the thiocyanate aqueous solution in step (2) comprises: mixing ammonium sulfate cyanide solution and concentrated hydrochloric acid to obtain the thiocyanate aqueous solution; Preferably, the concentration of thiocyanate in the thiocyanate aqueous solution in step (2) is 0.001-5 mol / dm 3 ; Preferably, the concentration of chloride ions in the thiocyanate aqueous solution in step (2) is 0.01-3 mol / dm 3 .

5. The method according to any one of claims 1 to 4, characterized in that: The volume ratio of the thiocyanate aqueous solution and the ketone extractant in step (2) is (0.2-5):1; Preferably, the oscillation time in step (2) is 1-3 min; Preferably, the oscillation speed in step (2) is 100-300 r / min.

6. The method according to any one of claims 1 to 5, characterized in that: The volume ratio of the organic phase and the aqueous phase in step (3) is (0.25-4):1; Preferably, the mixed extraction in step (3) is carried out under oscillation; Preferably, the oscillation time in the mixed extraction is 15-20 min; Preferably, the oscillation speed in the mixed extraction is 100-300 r / min; Preferably, the temperature of the mixed extraction is 0-40°C.

7. The method according to any one of claims 1 to 6, characterized in that: The method further comprises: mixing the hafnium-containing organic phase with a stripping solution for stripping and phase separation to obtain an aqueous solution containing hafnium ions; Preferably, the stripping solution comprises aqueous hydrochloric acid; Preferably, the concentration of hydrochloric acid in the stripping solution is 0.5-5 mol / dm 3 .

8. The method according to claim 7, characterized in that The volume ratio of the hafnium-containing organic phase to the stripping solution is (0.25-4):1; Preferably, the temperature of the mixed stripping is 0-40°C; Preferably, the oscillation time in the mixed stripping is 15-20 min; Preferably, the oscillation speed in the mixed stripping is 100-300 r / min.

9. The method according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: (1) Mixing a zirconium-hafnium mixed salt having a mass ratio of hafnium to zirconium of (0.005-0.25):1, ammonium thiocyanate, concentrated hydrochloric acid, an organic acid and water to obtain an aqueous phase, wherein the total concentration of zirconium-hafnium ions in the aqueous phase is 0.005-2 mol / dm 3 ; (2) mixing an aqueous thiocyanate solution and a ketone extractant in a volume ratio of (0.2-5):1, then shaking and liquid-liquid separation to obtain an organic phase; (3) extracting the organic phase and the aqueous phase at a volume ratio of (0.25-4):1 at 0-40° C., and obtaining an organic phase containing hafnium by phase separation, wherein the separation coefficient of the mixed extraction is 5.00-7.00; (4) Mixing the hafnium-containing organic phase and the stripping solution at 0-40° C. in a volume ratio of (0.25-4):1 for stripping, and then performing phase separation to obtain an aqueous solution containing hafnium ions.

10. Use of the method for separating zirconium and hafnium from a zirconium and hafnium mixed salt according to any one of claims 1 to 9 in ore purification.

Images