A process for the synergistic solvent extraction separation of niobium and tantalum and an extractant composition

Abstract

The application relates to the field of chemical metallurgy and extraction separation, and discloses a method for cooperatively extracting and separating niobium and tantalum and an extractant composition, which comprises a main extractant octyl amine, a cooperative extractant cyclohexanone, a polar inducer and a diluent. The method comprises the following steps: dissolving niobium and tantalum-containing raw materials in a sulfuric acid-oxalic acid mixed solution, performing heating depolymerization, forced quenching and closed aging treatment to obtain a water phase to be extracted; mixing the composition as an organic phase with the water phase to be extracted to perform extraction, and applying an alternating temperature pulse flow field during the extraction process; after static separation, washing and precipitation back extraction are performed on a niobium-rich loaded organic phase, and solid-liquid separation is performed to obtain pure niobium hydroxide. The application promotes the formation of polynuclear complexes by the thermodynamic and kinetic difference aging process of the water phase, and realizes the high-selectivity extraction of mononuclear niobium complex ions in a fluorine-free system by combining the coordination space constructed by the composition at the liquid-liquid interface and the steric repulsion, the emulsification phenomenon is eliminated, and the separation coefficient of niobium and tantalum is improved.

Description

Technical Field

[0001] This invention relates to the fields of chemical metallurgy and extraction separation technology, specifically to a method and extractant composition for the synergistic extraction and separation of niobium and tantalum. Background Technology

[0002] Niobium and tantalum are refractory rare metals that exhibit high similarity in physical and chemical properties. Because niobium and tantalum belong to the same group in the periodic table and are subject to the lanthanide contraction effect, their atomic and ionic radii are almost identical, making their coexistence and separation difficult. Niobium-tantalum separation is a core process in metallurgical and chemical processes for obtaining high-purity niobium and tantalum products.

[0003] Currently, the mainstream technology for separating niobium and tantalum in the metallurgical industry heavily relies on hydrofluoric acid extraction systems. The common procedure involves dissolving niobium-tantalum minerals in a mixed solution of hydrofluoric acid and sulfuric acid, followed by the use of methyl isobutyl ketone or tributyl phosphate as the extractant. Tantalum is extracted into the organic phase by preferentially forming fluorotantalate complex anions. The industry has also explored the development of fluorine-free extraction processes, typically using sulfuric acid or oxalic acid aqueous solutions as the dissolving medium, and in conjunction with amine compounds for metal extraction.

[0004] Existing separation processes rely excessively on hydrofluoric acid, which is highly toxic and corrosive. This not only imposes stringent requirements on the corrosion resistance of production equipment but also results in costly and environmentally polluting treatment of the generated fluorine-containing wastewater. To address the pollution problem of fluorine-containing systems, attempts have been made to apply non-fluorinated amine extraction systems. However, these systems suffer from low interfacial polarity matching and excessively high viscosity of the organic phase during liquid-liquid mixing. Emulsification easily occurs at the extraction interface, generating a third-phase flocculent, preventing the organic and aqueous phases from achieving clear stratification and extending phase separation time. Consequently, continuous liquid-liquid extraction separation operations cannot be stably performed. Summary of the Invention

[0005] The technical problem solved by this invention is that existing niobium-tantalum separation mainly relies on hydrofluoric acid system, which has the problems of high toxicity, strong corrosion and environmental pollution caused by fluoride-containing wastewater; while existing fluoride-free separation system has liquid-liquid emulsification phenomenon during extraction, and the niobium-tantalum separation coefficient is low, which makes it impossible to effectively separate niobium and tantalum.

[0006] To address the above problems, the present invention provides the following technical solution: In a first aspect, the present invention provides an extractant composition, which adopts the following technical solution: An extractant composition comprising the following components by volume percentage, wherein the sum of the volume percentages of each component is 100%: 15% to 30% of a primary extractant, wherein the primary extractant is 2-octylamine; 10% to 20% of a co-extractant, wherein the co-extractant is cyclohexanone; 0.8% to 2.0% of a polarity inducer; and the balance being a diluent.

[0007] By employing the above technical solution, a liquid-liquid extraction interface microenvironment, involving both the main extractant and synergistic extractants, is constructed during the extraction process in a fluorine-free aqueous system through a specific combination of 2-octylamine, cyclohexanone, and a polar inducer. In the system, 2-octylamine undergoes protonation under acidic conditions, serving as an ion association site for extracting niobium oxalate complex anions. Cyclohexanone, as a synergistic component, reduces the viscosity of the organic phase and interacts with the protonated 2-octylamine via intermolecular forces, forming a coordination space of a specific size in the organic phase. The polar inducer regulates the polar environment at the two-phase interface, guiding the directional arrangement of cyclohexanone molecules. This extractant composition can selectively accommodate mononuclear niobium oxalate complex anions while simultaneously creating steric hindrance for larger impurity complexes. Therefore, the niobium-tantalum separation coefficient is improved, and the third-phase emulsification phenomenon generated in single-amine extraction systems is eliminated, thereby increasing the phase separation rate.

[0008] Preferably, the volume ratio of the synergistic extractant to the polar inducer is 10:1 to 15:1.

[0009] By adopting the above technical solution, the relative concentration range of the polarity inducer is limited, and while adjusting the interfacial polarity, excessive inducer is avoided from interfering with the protonation process of the main extractant, thus maintaining the thermodynamic stability of the extraction system.

[0010] Preferably, the polarity inducer is 2,6-dimethyl-4-heptanone or trioctylmethylammonium chloride.

[0011] By adopting the above technical solution, suitable ketones and quaternary ammonium salts were selected as polar inducers, which reduced the interfacial tension between the two phases and promoted phase separation.

[0012] Preferably, the diluent is sulfonated kerosene or n-hexane.

[0013] By adopting the above technical solution, a stable carrier medium is provided, ensuring the dissolution of the main extractant and extractant in the organic phase.

[0014] Secondly, the present invention provides a method for the synergistic extraction and separation of niobium and tantalum using the aforementioned extractant composition, employing the following technical solution: A method for synergistic extraction and separation of niobium and tantalum using an extractant composition includes the following steps: (1) Preparation of aqueous precursor: Niobium-tantalum raw material is dissolved in sulfuric acid-oxalic acid mixture to obtain initial aqueous solution. The initial aqueous solution is heated and kept at a constant temperature for depolymerization treatment, then forcibly quenched and aged in a sealed environment to obtain the aqueous phase to be extracted. (2) Mixed extraction: The extractant composition is used as the organic phase and mixed with the aqueous phase to be extracted. During the mixed extraction process, an alternating temperature pulse flow field is implemented. After standing and phase separation, the niobium-rich supported organic phase and the tantalum-rich raffinate are separated. (3) Washing and back-extraction: The niobium-rich loaded organic phase was washed, and then a back-extraction agent was added for precipitation and back-extraction. After solid-liquid separation, niobium hydroxide product and blank organic phase were obtained.

[0015] By adopting the above technical solution, this invention utilizes the separation mechanism of aqueous precursor morphology regulation and organic phase spatial acceptor recognition. The specific reaction process and innovative principle are explained below: The first stage involves the thermodynamic and kinetic regulation of the aqueous precursor. In the sulfuric acid-oxalic acid system, niobium and tantalum readily form complexes with similar chemical properties. The heating and holding process utilizes thermodynamic heating conditions to depolymerize the niobium-tantalum polynuclear polymer in the feed solution into mononuclear oxalic acid complexes. The subsequent forced quenching and closed static aging process leverages the rate difference between tantalum and niobium at the polymerization kinetics level. Tantalum exhibits a higher polymerization rate than niobium. During low-temperature aging, tantalum ions in the aqueous phase preferentially polymerize to form larger polynuclear complexes, while niobium ions are kinetically restricted to maintain a mononuclear anionic state. This aging pretreatment step establishes the morphological differences of the niobium-tantalum complexes in terms of physical size.

[0016] The second stage is steric hindrance recognition extraction. When the organic phase contacts the aqueous phase to be extracted, the coordination space constructed by 2-octylamine and cyclohexanone matches the size dimension of the mononuclear niobium oxalate complex anion, forming a ternary synergy that enters the organic phase. The polynuclear tantalum complex formed in the aqueous phase due to steric hindrance is difficult to stably bind with the coordination network in the organic phase, and is thus repelled and retained in the aqueous phase. The alternating temperature pulse flow field applied during the extraction stage can interfere with the mass exchange process at the extraction interface. Because hydrogen bonding and weak coordination are sensitive to temperature, the temperature pulses induce dynamic dissociation at the interface, causing trace impurity ions physically entrained into the organic phase to detach from the coordination network and return to the aqueous phase, further improving the separation coefficient of the niobium-tantalum system.

[0017] The third stage is precipitation back-extraction. A strongly alkaline back-extraction agent is directly mixed with the niobium-rich supported organic phase. The back-extraction agent neutralizes the amine salt system in the supported organic phase and destroys the oxalic acid complex structure of niobium, causing the target product niobium to be directly converted into insoluble niobium hydroxide solid and precipitated. This achieves simultaneous separation of the organic liquid phase, waste liquid phase and solid product, simplifying subsequent preparation steps.

[0018] Preferably, in the initial aqueous phase feed solution, the free concentration of sulfuric acid is 1.5 to 3.0 mol / L, the free concentration of oxalic acid is 0.5 to 1.2 mol / L, and the molar concentration of total niobium-tantalum metal ions is 0.1 to 0.3 mol / L.

[0019] By adopting the above technical solution, the molar ratio of the coordinating reagent to the metal ions is controlled to ensure that there is a sufficient amount of free oxalate in the system to inhibit the hydrolysis and precipitation of metal ions during the aging stage and maintain the homogeneity of the aqueous phase solution.

[0020] Preferably, the heating and holding temperature is 65 to 80°C for 1.0 to 2.0 hours; the forced quenching time is 15 to 20 minutes, cooling down to 15 to 25°C; and the sealed static aging temperature is 15 to 25°C for 2.0 to 4.0 hours.

[0021] By adopting the above technical solution, the physical operation window required to induce differences in polymerization kinetics is defined, so that tantalum can form polymers while maintaining the mononuclear depolymerization state of niobium.

[0022] Preferably, the volume ratio of the organic phase to the aqueous phase to be extracted is 1:1 to 2:1; the alternating temperature pulse flow field causes the temperature of the mixing system to alternate between 15 to 20°C and 35 to 40°C, with an alternation frequency of 1 to 3 times per minute, and the total mixing and extraction time is 10 to 15 minutes.

[0023] By adopting the above technical solutions and setting appropriate interfacial mass transfer area and thermal energy fluctuation conditions, the mass transfer flux of single-stage extraction can be improved and the entrainment rate of impurity ions can be reduced.

[0024] Preferably, a mixed solution of sulfuric acid and oxalic acid is used as the washing solution, wherein the concentration of sulfuric acid in the washing solution is 0.5 to 1.0 mol / L and the concentration of oxalic acid is 0.1 to 0.2 mol / L; the volume ratio of washing is 2:1 to 5:1, and the mixing and washing time is 5 to 10 min.

[0025] By adopting the above technical solution, the acidity and free ligand balance during the washing process are maintained, physically entrained impurities are washed away, and the back-extraction loss of target metals in the loaded organic phase is avoided.

[0026] Preferably, the back-extraction agent is an aqueous solution of sodium hydroxide or ammonia with a concentration of 1.0 to 3.0 mol / L; the volume ratio of back-extraction is 1:1, and the mixing contact time is 10 to 20 min.

[0027] By adopting the above technical solution, sufficient alkalinity is provided to drive the neutralization reaction, so that niobium hydroxide is completely precipitated and precipitated, ensuring the structural regeneration and recycling of the blank organic phase.

[0028] This invention provides a method and extractant composition for the synergistic extraction and separation of niobium and tantalum. It offers the following advantages: 1. This invention constructs a fluorine-free extraction and separation system, avoiding the safety hazards and equipment corrosion problems associated with traditional hydrofluoric acid processes, and reducing the treatment cost of fluorine-containing wastewater. By employing an extractant composition consisting of 2-octylamine, cyclohexanone, and a polar inducer, the polar microenvironment of the liquid-liquid interface and the viscosity of the organic phase are adjusted using cyclohexanone and the polar inducer, eliminating the third-phase emulsification phenomenon that easily occurs in fluorine-free amine extraction processes, shortening the time for two-phase clarification and separation, and ensuring the continuous stability of the extraction process.

[0029] 2. This invention improves the separation coefficient between niobium and tantalum. By subjecting the aqueous solution to heating depolymerization, forced quenching, and low-temperature aging pretreatment, the difference in kinetic rates between tantalum and niobium during the polymerization reaction is utilized to convert tantalum ions into polynuclear complexes in the aqueous phase, while niobium ions remain in a mononuclear complex anionic state. At the liquid-liquid extraction interface, the coordination space constructed by sec-octylamine and cyclohexanone in the organic phase repels the larger polynuclear tantalum complexes through steric hindrance, achieving selective extraction of mononuclear niobium complex ions and overcoming the poor selectivity of single amine extractants for niobium and tantalum in fluorine-free systems.

[0030] 3. This invention simplifies the separation and preparation process and controls impurity entrainment. During the mixing and extraction stage, an alternating temperature pulsed flow field is applied. Utilizing the sensitivity of weak coordination to temperature fluctuations, impurities carried from the physical phase into the organic phase undergo dynamic dissociation and return to the aqueous phase, improving the extraction purity of the target metal. In the back-extraction stage, a strongly alkaline solution is used for precipitation back-extraction, directly destroying the complex structure in the supported organic phase, causing niobium to be converted into niobium hydroxide precipitate in one step, achieving simultaneous acquisition of the solid-phase product and regeneration of the blank organic phase. Attached Figure Description

[0031] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Common solvents and inorganic acid-base reagents (including n-hexane, anhydrous oxalic acid, 98% concentrated sulfuric acid, sodium hydroxide, and 25% to 28% ammonia) are all commercially available analytical grade products and will not be described further. In the core organic components of the extraction process, the main extractant, di(1-methylheptyl)amine (commonly known as sec-octylamine, CAS No. 2430-27-5), is an extraction-grade product with a purity greater than or equal to 98%; the synergistic extractant, cyclohexanone (CAS No. 108-94-1), is an analytical grade product with a purity greater than or equal to 99.5%; and the polar inducing agents, 2,6-dimethyl-4-heptanone (commonly known as diisobutyl ketone, CAS No. 108-83-8) and trioctylmethylammonium chloride (CAS No. 5137-55-3, purity greater than or equal to 97%), are both commercially available analytical grade products. The diluent, sulfonated kerosene, is a commercially available extraction-grade mixed hydrocarbon solvent with a closed-cup flash point greater than 65℃ and an aromatic hydrocarbon mass fraction of less than 0.5%. The metal raw materials, niobium hydroxide (CAS No. 12050-18-9) and tantalum hydroxide (CAS No. 12050-19-0), are both commercially available high-purity products with a purity greater than or equal to 99.9%. All other reagents not specifically mentioned are commercially available analytical grade or higher products.

[0034] Preparation Example 1: This preparation example provides an extractant composition preferred as a central parameter, comprising the following steps: In a mixing tank equipped with mechanical stirring, the ambient temperature was controlled at 20°C. By volume percentage, 20% octylamine, 15% cyclohexanone, 1.2% 2,6-dimethyl-4-heptanone (cyclohexanone to polar inducer volume ratio 12.5:1), and 63.8% sulfonated kerosene were added sequentially. The mechanical stirring was turned on, and the stirring speed was set to 300 rpm. The mixture was continuously stirred for 45 minutes, then allowed to stand for 20 minutes to obtain a homogeneous and transparent organic phase extractant composition.

[0035] Preparation Example 2: This preparation example provides an extractant composition corresponding to the lower limit of the parameter, comprising the following steps: In a mixing tank equipped with mechanical stirring, the ambient temperature was controlled at 15°C. By volume percentage, 15% 2-octylamine, 10% cyclohexanone, 0.8% 2,6-dimethyl-4-heptanone (cyclohexanone to polar inducer volume ratio 12.5:1), and 74.2% sulfonated kerosene were added sequentially. The mechanical stirring was turned on, and the stirring speed was set to 200 rpm. The mixture was continuously stirred for 30 minutes, then allowed to stand for 15 minutes to obtain a homogeneous and transparent organic phase extractant composition.

[0036] Preparation Example 3: This preparation example provides an extractant composition corresponding to the upper limit of parameters, including the following steps: In a mixing tank equipped with mechanical stirring, the ambient temperature was controlled at 25°C. 30% octylamine, 20% cyclohexanone, 2.0% 2,6-dimethyl-4-heptanone (cyclohexanone to polar inducer volume ratio 10:1), and 48% sulfonated kerosene were added sequentially by volume percentage. The mechanical stirring was turned on, and the stirring speed was set to 400 rpm. The mixture was continuously stirred for 60 minutes, then allowed to stand for 30 minutes to obtain a homogeneous and transparent organic phase extractant composition.

[0037] Preparation Example 4: This preparation example provides a differentially aged aqueous phase precursor preferred as a central parameter, comprising the following steps: Niobium hydroxide and tantalum hydroxide raw materials were dissolved in a sulfuric acid-oxalic acid mixture to prepare an initial aqueous solution, wherein the free concentration of sulfuric acid was 2.0 mol / L, the free concentration of oxalic acid was 0.8 mol / L, and the molar concentration of total niobium and tantalum metal ions was 0.2 mol / L. This initial solution was transferred to a jacketed, temperature-controlled reactor and heated to 70°C. Low-speed stirring at 120 rpm was initiated, and the solution was held at this temperature for 1.5 hours. After the holding period, a cooling liquid was introduced into the reactor jacket, forcibly lowering the overall temperature of the aqueous solution to 20°C within 18 minutes. Stirring was stopped, and the cooled solution was allowed to stand and age in a sealed container at 20°C for 3.0 hours to obtain the aqueous precursor to be extracted.

[0038] Preparation Example 5: This preparation example provides a differentially aged aqueous phase precursor corresponding to the lower limit of parameters, including the following steps: Niobium hydroxide and tantalum hydroxide raw materials were dissolved in a sulfuric acid-oxalic acid mixture to prepare an initial aqueous solution, wherein the free concentration of sulfuric acid was 1.5 mol / L, the free concentration of oxalic acid was 0.5 mol / L, and the molar concentration of total niobium and tantalum metal ions was 0.1 mol / L. This initial solution was transferred to a jacketed, temperature-controlled reactor and heated to 65°C. Low-speed stirring at 100 rpm was initiated, and the solution was held at this temperature for 1.0 hour. After the holding period, a cooling liquid was introduced into the reactor jacket to forcibly lower the overall temperature of the aqueous solution to 15°C within 15 minutes. Stirring was stopped, and the cooled solution was allowed to stand and age in a sealed container at 15°C for 2.0 hours to obtain the aqueous precursor to be extracted.

[0039] Preparation Example 6: This preparation example provides a differentially aged aqueous phase precursor corresponding to the upper limit of parameters, including the following steps: Niobium hydroxide and tantalum hydroxide raw materials were dissolved in a sulfuric acid-oxalic acid mixture to prepare an initial aqueous solution, wherein the free concentration of sulfuric acid was 3.0 mol / L, the free concentration of oxalic acid was 1.2 mol / L, and the molar concentration of total niobium and tantalum metal ions was 0.3 mol / L. This initial solution was transferred to a jacketed, temperature-controlled reactor and heated to 80°C. Low-speed stirring at 150 rpm was initiated, and the solution was held at this temperature for 2.0 hours. After the holding period, a cooling liquid was introduced into the reactor jacket to forcibly lower the overall temperature of the aqueous solution to 25°C within 20 minutes. Stirring was stopped, and the cooled solution was allowed to stand and age in a sealed container at 25°C for 4.0 hours to obtain the aqueous precursor to be extracted.

[0040] Example 1: This embodiment provides a method and extractant composition for the synergistic extraction and separation of niobium and tantalum, including the following steps: The extractant composition prepared in Preparation Example 1 was used as the organic phase, and the aqueous precursor to be extracted prepared in Preparation Example 4 was used as the aqueous phase.

[0041] The organic phase and aqueous phase were pumped into the mixing chamber of a countercurrent mixing and clarifying tank equipped with a temperature control system at a volume ratio (O / A) of 1.5:1. Stirring was started and the stirring speed was set to 400 rpm. During this mixing and extraction stage, an alternating temperature pulse flow field was implemented through the tank coils, causing the temperature of the mixing system to alternate between 18°C ​​and 38°C, with an alternation frequency set to twice per minute. The total residence time for mixing and extraction was controlled to be 12 minutes.

[0042] After mixing, the mixture overflows into the clarification chamber and undergoes static phase separation at 20°C for 20 minutes to separate the niobium-rich supported organic phase and the tantalum-rich raffinate.

[0043] The niobium-rich supported organic phase was washed with a mixed aqueous solution of 0.8 mol / L sulfuric acid and 0.15 mol / L oxalic acid. The washing ratio (O / A) was controlled at 3:1, and the washing was carried out at 20°C for 8 minutes. After standing and phase separation, the organic phase was retained.

[0044] The washed organic phase was subjected to precipitation back-extraction using a 1.5 mol / L sodium hydroxide aqueous solution. The back-extraction ratio (O / A) was controlled at 1:1, and the mixture was contacted at 20°C for 15 minutes to convert niobium in the organic phase into solid niobium hydroxide. The back-extraction mixture was then subjected to liquid-solid separation by pressure filtration, and the filter cake was collected to obtain pure niobium hydroxide product. After the filtrate was allowed to stand and separate into phases, a blank organic phase and back-extraction waste liquid were separated. The blank organic phase was regenerated by water washing and recycled.

[0045] Example 2: This embodiment provides a method and extractant composition for the synergistic extraction and separation of niobium and tantalum, including the following steps: The extractant composition prepared in Preparation Example 2 was used as the organic phase, and the aqueous precursor to be extracted prepared in Preparation Example 5 was used as the aqueous phase.

[0046] The organic phase and aqueous phase were pumped into the mixing chamber of a countercurrent mixing and clarifying tank equipped with a temperature control system at a volume ratio (O / A) of 1:1. Stirring was started and the stirring speed was set to 300 rpm. During this mixing and extraction stage, an alternating temperature pulse flow field was implemented through the tank coils, causing the temperature of the mixing system to alternate between 15°C and 35°C, with an alternation frequency set to once per minute. The total residence time for mixing and extraction was controlled to be 10 minutes.

[0047] After mixing, the mixture overflows into the clarification chamber and undergoes static phase separation at 15°C for 15 minutes to separate the niobium-rich supported organic phase and the tantalum-rich raffinate.

[0048] The niobium-rich supported organic phase was washed with a mixed aqueous solution of 0.5 mol / L sulfuric acid and 0.1 mol / L oxalic acid. The washing ratio (O / A) was controlled at 2:1, and the mixture was washed for 5 minutes at 15 °C. After standing and phase separation, the organic phase was retained.

[0049] The washed organic phase was subjected to precipitation back-extraction using a 1.0 mol / L sodium hydroxide aqueous solution. The back-extraction ratio (O / A) was controlled at 1:1, and the mixture was contacted at 15°C for 10 minutes to convert niobium in the organic phase into solid niobium hydroxide. The back-extraction mixture was then subjected to liquid-solid separation by pressure filtration, and the filter cake was collected to obtain pure niobium hydroxide product. After the filtrate was allowed to stand and separate into phases, a blank organic phase and back-extraction waste liquid were separated. The blank organic phase was regenerated by water washing and then recycled.

[0050] Example 3: This embodiment provides a method and extractant composition for the synergistic extraction and separation of niobium and tantalum, including the following steps: The extractant composition prepared in Preparation Example 3 was used as the organic phase, and the aqueous precursor to be extracted prepared in Preparation Example 6 was used as the aqueous phase.

[0051] The organic phase and aqueous phase were pumped into the mixing chamber of a countercurrent mixing and clarifying tank equipped with a temperature control system at a volume ratio (O / A) of 2:1. Stirring was started and the stirring speed was set to 500 rpm. During this mixing and extraction stage, an alternating temperature pulse flow field was implemented through the tank coils, causing the temperature of the mixing system to alternate between 20°C and 40°C, with an alternation frequency set to 3 times per minute. The total residence time for mixing and extraction was controlled to be 15 minutes.

[0052] After mixing, the mixture overflows into the clarification chamber and undergoes static phase separation at 25°C for 30 minutes to separate the niobium-rich supported organic phase and the tantalum-rich raffinate.

[0053] The niobium-rich supported organic phase was washed with a mixed aqueous solution of 1.0 mol / L sulfuric acid and 0.2 mol / L oxalic acid. The washing ratio (O / A) was controlled at 5:1, and the mixture was washed for 10 minutes at 25°C. After standing and phase separation, the organic phase was retained.

[0054] The washed organic phase was subjected to precipitation back-extraction using a 2.0 mol / L sodium hydroxide aqueous solution. The back-extraction ratio (O / A) was controlled at 1:1, and the mixture was contacted at 25°C for 20 minutes to convert niobium in the organic phase into solid niobium hydroxide. The back-extraction mixture was then subjected to liquid-solid separation by pressure filtration, and the filter cake was collected to obtain pure niobium hydroxide product. After the filtrate was allowed to stand and separate into phases, a blank organic phase and back-extraction waste liquid were separated. The blank organic phase was regenerated by washing with water and then recycled.

[0055] Example 4: This embodiment provides a method and extractant composition for the synergistic extraction and separation of niobium and tantalum, including the following steps: A new extractant composition was prepared, following the same preparation process as in Preparation Example 1, except that the polar inducer 2,6-dimethyl-4-heptanone was replaced by an equal volume of trioctylmethylammonium chloride, resulting in an organic phase with the polar inducer replaced. The aqueous precursor to be extracted obtained in Preparation Example 4 was used as the aqueous phase.

[0056] The organic phase and aqueous phase were pumped into the mixing chamber of a countercurrent mixing and clarifying tank equipped with a temperature control system at a volume ratio (O / A) of 1.5:1. Stirring was started and the stirring speed was set to 400 rpm. During this mixing and extraction stage, an alternating temperature pulse flow field was implemented through the tank coils, causing the temperature of the mixing system to alternate between 18°C ​​and 38°C, with an alternation frequency set to twice per minute. The total residence time for mixing and extraction was controlled to be 12 minutes.

[0057] After mixing, the mixture overflows into the clarification chamber and undergoes static phase separation at 20°C for 20 minutes to separate the niobium-rich supported organic phase and the tantalum-rich raffinate.

[0058] The niobium-rich supported organic phase was washed with a mixed aqueous solution of 0.8 mol / L sulfuric acid and 0.15 mol / L oxalic acid. The washing ratio (O / A) was controlled at 3:1, and the washing was carried out at 20°C for 8 minutes. After standing and phase separation, the organic phase was retained.

[0059] Ammonia solution with a concentration of 3.0 mol / L was used as the back-extraction agent to perform precipitation back-extraction on the washed organic phase. The back-extraction ratio (O / A) was controlled at 1:1, and the mixture was mixed and contacted at 20°C for 15 minutes to convert niobium in the organic phase into solid niobium hydroxide. The back-extraction mixture was then subjected to liquid-solid separation by pressure filtration, and the filter cake was collected to obtain pure niobium hydroxide product. After the filtrate was allowed to stand and separate into phases, a blank organic phase and back-extraction waste liquid were separated. The blank organic phase was regenerated by water washing and then recycled.

[0060] Comparative Example 1: Compared with Example 1, the difference is that: no synergistic extractant cyclohexanone was added, and the missing volume of cyclohexanone in the preparation of the extractant composition was made up by the diluent sulfonated kerosene; all other aspects are the same.

[0061] Comparative Example 2: Compared with Example 1, the difference is that: the aqueous phase was not subjected to thermodynamic-kinetic differential aging pretreatment. After the raw materials were dissolved and prepared into an initial aqueous phase solution, it was directly sent to the extraction process at room temperature as the aqueous phase. All other aspects are the same.

[0062] Comparative Example 3: Compared with Example 1, the difference is that when preparing the extractant composition, the synergistic extractant cyclohexanone is replaced by an equal volume of the phase modifier 2-octanol commonly used in the art, while the rest are the same.

[0063] Comparative Example 4: Compared with Example 1, the difference is that the main extractant octylamine and polar inducer were not added to the organic phase of the extraction. It was only made by mixing 35% methyl isobutyl ketone (MIBK) and 65% sulfonated kerosene by volume. All other aspects are the same.

[0064] Comparative Example 5: Compared with Example 1, the difference is that: in the mixing and extraction stage, the alternating temperature pulse flow field was not implemented, but the temperature of the mixing system was kept constant at 20°C throughout the mixing and extraction process, while the rest were the same.

[0065] Comparative Example 6: Compared with Example 1, the difference is that the polar inducer 2,6-dimethyl-4-heptanone was not added to the extractant composition, and the missing volume was made up by the diluent sulfonated kerosene; all other aspects are the same.

[0066] Test Example 1: Take the mixtures from Examples 1 to 4 after the mixing and extraction stages and pour them into stoppered graduated cylinders. Use a stopwatch to record the time required for the two-phase interface to become clear and constant from the moment stirring stops; this time is taken as the phase separation time. Observe the state of the two-phase interface and record whether flocculent matter or an emulsion layer is formed. After complete phase separation, extract the lower raffinate and use inductively coupled plasma optical emission spectrometry (ICP-OES) to determine the remaining mass concentrations of niobium and tantalum in the water.

[0067] The distribution ratio D of metal ions and the separation coefficient β are calculated using the following formula: Distribution ratio Separation coefficient Single-stage niobium extraction rate In the formula, This represents the mass concentration of metal ions in the initial aqueous feed solution. This represents the mass concentration of metal ions in the raffinate. For the volume of the water phase, The volume is the organic phase.

[0068] Table 1. Single-stage extraction and separation test data from Examples 1 to 4

[0069] According to the test data in Table 1, the phase separation time for Examples 1 to 4 was less than 40 seconds, and no third-phase emulsification was observed at the two-phase interface. Cyclohexanone, together with the polarity inducer, reduced the viscosity and interfacial tension of the organic phase, forming a spatial arrangement with 2-octylamine at the extraction interface, thus improving the phase separation state.

[0070] In each embodiment, the single-stage extraction rate of niobium is greater than 91%, and the niobium-tantalum separation coefficient is greater than 60, achieving niobium-tantalum separation in a fluorine-free system. The aqueous aging pretreatment process promotes the polymerization of tantalum ions, increasing the kinetic radius of the tantalum complex ions. When the organic phase contacts the aqueous phase, 2-octylamine and cyclohexanone construct a coordination space through intermolecular forces, accommodating the mononuclear niobium oxalate complex anion. Due to its large steric hindrance, the polynuclear tantalum complex is difficult to stably associate with protonated amines and is ultimately retained in the aqueous phase.

[0071] Example 3 showed the highest separation coefficient, indicating that the alternating temperature pulsed flow field interferes with physically entrained and weakly interacting impurity ions, promoting the dissociation of tantalum with low steric hindrance matching from the dynamic coordination network. In Example 4, after replacing a trace amount of polar inducer, the separation coefficient remained above 100, confirming that polar compounds with different structures can induce changes in the interfacial polar microenvironment, promoting directional arrangement and preferential extraction of niobium.

[0072] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An extractant composition, characterized in that, The composition comprises the following components by volume percentage, and the sum of the volume percentages of each component is 100%: Main extractant: 15%~30%, wherein the main extractant is 2-octylamine; Synergistic extractant: 10%~20%, wherein the synergistic extractant is cyclohexanone; Polarity inducer: 0.8%~2.0%; Diluent: The remainder, wherein the diluent is sulfonated kerosene.

2. The extractant composition according to claim 1, characterized in that, The volume ratio of the synergistic extractant to the polar inducer is from 10:1 to 12.5:

1.

3. The extractant composition according to claim 1, characterized in that, The polarity inducer is 2,6-dimethyl-4-heptanone or trioctylmethylammonium chloride.

4. A method for synergistic extraction and separation of niobium and tantalum using the extractant composition according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Preparation of aqueous precursor: Niobium-tantalum raw material is dissolved in sulfuric acid-oxalic acid mixture to obtain initial aqueous solution. The initial aqueous solution is heated and kept at a constant temperature for depolymerization treatment, then forcibly quenched and aged in a sealed environment to obtain the aqueous phase to be extracted. S2. Mixed extraction: The extractant composition is used as the organic phase and mixed with the aqueous phase to be extracted obtained in step S1. During the mixed extraction process, an alternating temperature pulse flow field is implemented. After standing and phase separation, the niobium-rich supported organic phase and the tantalum-rich raffinate are separated. S3. Washing and back-extraction: The niobium-rich supported organic phase is washed, and then a back-extraction agent is added for precipitation and back-extraction. After solid-liquid separation, niobium hydroxide product and blank organic phase are obtained.

5. The method according to claim 4, characterized in that, In step S1, the initial aqueous solution contains sulfuric acid with a free concentration of 1.5-3.0 mol / L, oxalic acid with a free concentration of 0.5-1.2 mol / L, and total niobium-tantalum metal ions with a molar concentration of 0.1-0.3 mol / L.

6. The method according to claim 4, characterized in that, In step S1, the heating and holding temperature is 65~80℃ for 1.0~2.0h; the forced quenching time is 15~20min, cooling down to 15~25℃; the sealed static aging temperature is 15~25℃ for 2.0~4.0h.

7. The method according to claim 4, characterized in that, In step S2, the volume ratio of the organic phase to the aqueous phase to be extracted is 1:1 to 2:1; the alternating temperature pulse flow field causes the temperature of the mixing system to alternate between 15~20℃ and 35~40℃, with an alternation frequency of 1~3 times per minute, and the total mixing and extraction time is 10~15 min.

8. The method according to claim 4, characterized in that, In step S3, a mixed solution of sulfuric acid and oxalic acid is used as the washing solution. The concentration of sulfuric acid in the washing solution is 0.5~1.0 mol / L and the concentration of oxalic acid is 0.1~0.2 mol / L. The volume ratio of washing is 2:1 to 5:1, and the mixing and washing time is 5~10 min.

9. The method according to claim 4, characterized in that, In step S3, the back-extraction agent is an aqueous solution of sodium hydroxide or ammonia, and the volume ratio of back-extraction is 1:

1.

10. The method according to claim 9, characterized in that, In step S3, the concentration of the back-extraction agent is 1.0~3.0 mol / L, and the mixing contact time is 10~20 min.

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