A method for removing fluorine by rare earth solution extraction

Abstract

The present application relates to a kind of methods for removing fluorine from rare earth solution by extraction, comprising: introducing metal ions selected from zirconium, hafnium ions into the rare earth solution;The rare earth solution is extracted to extract fluorine, and a low-fluorine rare earth solution is obtained.The present application adds a mixture of zirconium, hafnium or any proportion of the mixture as a fluorine complexing agent to the rare earth solution by selecting the mixture with strong fluorine complexing ability, the fluorine complexing agent preferentially complexes with fluorine in a low-acid solution, and then through extraction and back extraction, efficient removal of fluorine is achieved.The method is simple in process and easy to operate, and has good application value.

Description

Technical Field

[0001] This invention belongs to the field of rare earth solution defluorination technology, specifically relating to a method for defluorination by rare earth solution extraction. Background Technology

[0002] In primary ores such as ion-adsorption rare earth minerals and bastnaes, fluorine exists as fluorides (e.g., CaF₂) or rare earth fluorides (e.g., REF₃), and enters the rare earth solution during leaching. Fluorine can exist in solution in different forms, such as [AlF₂]. x ] 3-x [CeF2] 2+ [MgF] + Fluorine complexes readily adsorb at the extractant interface, forming a stable third phase. This makes emulsification and stratification of the extractant difficult, reduces its cycle life, and necessitates frequent regeneration. Fluoride ions (F...) - ) and rare earth ions (RE) 3+ Combined generation These complexes are difficult for the extractant to capture, leading to a decrease in rare earth extraction rate. Fluorine-containing complexes migrate and accumulate in the tank, affecting the quality of the final product. Furthermore, fluoride ions in acidic extraction systems form hydrofluoric acid (HF), causing pitting and crevice corrosion on stainless steel and carbon steel equipment, increasing equipment maintenance costs and safety risks. Therefore, deep defluorination of the rare earth solution is essential for rare earth extraction and separation.

[0003] CN120536759A discloses a defluorinating agent and defluorinating process for rare earth solutions, which uses polycrystalline composite calcium and a defluorinating agent composed of polycrystalline composite calcium and inorganic flocculant to efficiently remove fluoride from rare earth solutions.

[0004] CN119433249A discloses a method for removing fluorine and aluminum from rare earth feed solutions. During the overflow reaction, the pH of the system is adjusted by an alkaline material, and after solid-liquid separation treatment, the fluorine in the rare earth feed solution is removed in the form of aluminum-fluorine slag.

[0005] CN115927884A discloses a method for removing fluoride from rare earth ore leaching solution, comprising the following steps: adding alkaline solution A to fluoride-containing rare earth ore leaching solution, stirring and adjusting the pH value of fluoride-containing ion-type rare earth ore leaching solution, obtaining solution B after clarification and solid-liquid separation, adding precipitant solution C to solution B, obtaining precipitate after clarification and solid-liquid separation, adding ammonium salt solution D to precipitate, stirring and leaching, and then performing pressure filtration and solid-liquid separation to obtain rare earth ore with low fluoride content. Summary of the Invention

[0006] The inventors studied existing rare earth solution defluorination technologies and found that common problems still exist, such as incomplete defluorination, high rare earth loss rate, and cumbersome operation.

[0007] To address the aforementioned problems, the inventors conducted in-depth research and experimentally verified a method for efficient fluoride removal via rare earth solution extraction. This method involves adding a substance with strong fluoride-complexing ability to the rare earth solution before extraction to efficiently remove fluoride, while simultaneously achieving the recycling of both the extractant and the fluoride complexing agent. Specifically, this invention selects zirconium, hafnium, or a mixture of both in any proportion as fluoride complexing agents and adds them to the rare earth solution. These fluoride complexing agents preferentially complex with fluoride in low-acid solutions, and then achieve efficient fluoride removal through extraction and back-extraction. Furthermore, the blank organic phase and the fluoride complexing agent can be recycled. The method is simple, highly operable, and has good application and promotion value.

[0008] In one aspect, the present invention provides a method for defluorination by rare earth solution extraction, comprising:

[0009] S1: Introduce metal ions selected from zirconium and hafnium ions into the rare earth solution;

[0010] S2: Extract the rare earth solution to extract fluorine and obtain a low-fluorine rare earth solution.

[0011] The method of the present invention is described in detail below.

[0012] Step S1

[0013] In step S1, metal ions selected from zirconium and hafnium ions are introduced into the rare earth solution.

[0014] The rare earth solution is an acidic solution containing one or more rare earth ions and fluoride ions, such as hydrochloric acid solution, sulfuric acid solution, or nitric acid solution. The rare earth solution may also contain aluminum ions, iron ions, calcium ions, etc. For example, the rare earth solution can be a rare earth ore leaching solution, such as the leaching solution of ionic rare earth ores, bastnaesite, etc., or it can be a solution obtained by acid decomposition of rare earth compounds, such as the decomposition solution of carbonates or hydroxides obtained after impurity removal and precipitation of ionic rare earth ore leaching solution.

[0015] In rare earth solutions, the concentration of rare earth elements (calculated as rare earth oxides) can be 1~250 g / L, such as 1 g / L, 10 g / L, 20 g / L, 120 g / L, 150 g / L, 180 g / L, 210 g / L, 240 g / L, etc., but is not limited to these.

[0016] In rare earth solutions, the concentration of fluoride ions can range from 50 to 5000 mg / L, such as 500 mg / L, 1000 mg / L, 1500 mg / L, 2000 mg / L, 2500 mg / L, 3000 mg / L, etc., but is not limited to these.

[0017] The acidity of rare earth solutions, expressed as hydrogen ion concentration, is 0.01~2 mol / L, for example 0.10 mol / L, 0.49 mol / L, 0.55 mol / L, 0.90 mol / L, 2.00 mol / L, etc., but is not limited to these.

[0018] In some embodiments, the molar ratio of the introduced metal ions to the fluoride ions in the rare earth solution is 5:1 to 1:5, preferably 4:1 to 1:4, such as 4:1, 3:1, 2:1, 1:1, 1:1.5, 1:2, 1:3, 1:4, etc.

[0019] Metal ions can be added to the rare earth solution in any form of a metal ion precursor that is soluble in the rare earth solution. For example, the metal ion precursor can be in the form of oxides, chlorides, chlorides, hydroxides, carbonates, sulfates, phosphates, nitrates, etc., preferably in the form of chlorides (or hydrochlorides), sulfates, and nitrates. In some embodiments, the metal ion precursor can be converted into a soluble form by acid dissolution, water dissolution, alkali dissolution, or alkali melt calcination before being added to the rare earth solution.

[0020] In some embodiments, metal ions selected from zirconium and hafnium ions are introduced into a rare earth solution and stirred for 10 to 60 minutes, preferably 20 to 40 minutes, to form a metal ion-fluorine complex.

[0021] Step S2

[0022] In step S2, the rare earth solution (aqueous phase) is extracted using an extraction system (organic phase) to extract fluorine (in the form of a complex of metal ions and fluorine), resulting in an extraction system (organic phase) loaded with fluorine and a raffinate (low-fluorine rare earth solution).

[0023] The extraction system includes an extractant and a diluent.

[0024] The extractant may be selected from the following extractants:

[0025] (1) Acidic phosphorus or phosphine extractant of formula I:

[0026]

[0027] in,

[0028] R 11 and R 12 Each is independently selected from C 1-12 Alkyl, C 1-12 Alkoxy, C 5-10 Alicyclic alkyl groups, C 5-10 Alicyclic alkoxy groups, C 6-10 Aryl and C 6-10 The aryl groups are preferably each independently selected from C.4-12 Alkyl, C 4-12 Alkoxy, C 5-10 Alicyclic alkyl groups, C 5-10 Alicyclic alkoxy groups, C 6-10 Aryl and C 6-10 aryloxy,

[0029] In particular, R 11 and R 12 The total number of carbon atoms is 8 to 24, preferably 10 to 18;

[0030] More specifically, the acidic phosphorus or phosphonic acid extractant shown in Formula I is selected from di(2-ethylhexyl)phosphoric acid (P204), 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507), di(2,4,4-trimethylpentyl)phosphonic acid (C272), and di(2-ethylhexyl)phosphonic acid (P227).

[0031] (2) Amino acid-containing phosphine extractant of formula II:

[0032]

[0033] in,

[0034] R 21 Selected from C 1-12 Alkyl, C 1-12 Alkyl groups, preferably selected from C 4-12 Alkyl, C 4-12 Alkoxy;

[0035] R 22 and R 23 Each is independently selected from hydrogen and C. 1-8 Alkyl, C 5-10 Alicyclic alkyl groups and C 6-10 Aryl groups; preferably each independently selected from hydrogen, C 1-4 Alkyl, C 5-8 Alicyclic alkyl groups and phenyl groups;

[0036] R 24 and R 25 Each was independently selected from C 1-16 Alkyl and hydrogen, preferably C 1-10 Alkyl and hydrogen, and R 24 and R 25 At most one is hydrogen;

[0037] In particular, R 21 R 22 R 23 R 24 and R 25 The total number of carbon atoms is 8 to 30, preferably 10-24;

[0038] More specifically, the amino acid-containing phosphine extractant shown in Formula II is selected from 2-ethylhexylaminomethylphosphonic acid mono-2-ethylhexyl ester (HEHAMP) and heptamethylaminomethylphosphonic acid mono-2-ethylhexyl ester (HEHHAP);

[0039] (3) Neutral phosphorus or phosphine extractants of Formula III:

[0040]

[0041] in,

[0042] R 31 R 32 and R 33 Each was independently selected from C 1-10 Alkyl and C 1-10 Alkoxy groups, preferably each independently selected from C10, are also present. 1-8 Alkyl and C 1-8 Alkoxy groups, and R 31 R 32 and R 33 The total number of carbon atoms is 8 to 30, preferably 10-24;

[0043] Specifically, the neutral phosphorus or phosphine extractant shown in Formula III is selected from dimethylheptyl methylphosphonate (P350), trialkylphosphine oxide (P113), linear trialkylphosphine oxide (C923), branched trialkylphosphine oxide (C925), etc.

[0044] (4) Formula IV containing amino-containing neutral phosphorus or phosphine extractants:

[0045]

[0046] in,

[0047] R 41 and R 42 Each was independently selected from C 1-12 Alkyl, C 1-12 Alkyl groups, preferably selected from C 4-12 Alkyl, C 4-12 Alkoxy;

[0048] R 43 and R 44 Each is independently selected from hydrogen and C. 1-8 Alkyl, C 5-10 Alicyclic alkyl groups and C 6-10 Aryl groups; preferably each independently selected from hydrogen, C 1-4 Alkyl, C 5-8 Alicyclic alkyl groups and phenyl groups;

[0049] R 45 and R 46Each was independently selected from C 1-16 Alkyl and hydrogen, preferably C 1-10 Alkyl and hydrogen, and R 45 and R 46 At most one is hydrogen;

[0050] In particular, R 41 R 42 R 43 R 44 R 45 and R 46 The total number of carbon atoms is 8 to 32, preferably 10-28;

[0051] More specifically, the amino-containing neutral phosphorus or phosphine extractant shown in Formula IV is selected from 1-(2-ethylhexylamino)methylphosphonate di(2-ethylhexyl) ester (C230); 1-(2-ethylhexylamino)-1-phenylmethylphosphonate di(2-ethylhexyl) ester; 1-(2-ethylhexylamino)-1-methylethylphosphonate di(2-ethylhexyl) ester; 1-(2-ethylhexylamino)-1-methylpropylphosphonate di(2-ethylhexyl) ester; 1-(2-ethylhexylamino)-1-ethylpropylphosphonate di(2-ethylhexyl) ester; 1-(N-dodecylamino)-1-methylethylphosphonate diethyl ester; 1-(2-ethylhexylamino)-n-propylphosphonate di(2-ethylhexyl) ester; 1-(N-butylamino)ethylphosphonate di(2-ethylhexyl) ester;

[0052] (5) Amine extractant of formula V:

[0053]

[0054] in,

[0055] R 51 R 52 and R 53 Each is independently selected from H and C. 7-23 Alkyl, and R 51 R 52 and R 53 At least one of them is not hydrogen; in particular, R 51 R 52 and R 53 The total number of carbon atoms is 8 to 32, preferably 10 to 30;

[0056] Specifically, the amine extractant for Formula V is selected from trioctyldecyl tertiary amine (N235) and secondary carbon primary amine extractant (N1923).

[0057] In some embodiments, the extractant is an acidic phosphorus or phosphine extractant of Formula I, more preferably P507.

[0058] Extractant P204 has the chemical name di(2-ethylhexyl)phosphate, di(2-ethylhexyl)phosphate ester, or diisooctyl phosphate, CAS number 298-07-7, and structure [not specified]. .

[0059] Extractant P507 has the chemical name of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester, 2-ethylhexylphosphonic acid mono(2-ethylhexyl) ester, or 2-ethylhexylhydro(2-ethylhexyl)phosphonate, CAS number 14802-03-0, and its structure is as follows: .

[0060] Extractant C272, also known as ZD272, Cyanex 272, or Lonquest 290, has the chemical name bis(2,4,4-trimethylpentyl)phosphonic acid and the structure is as follows: .

[0061] Extractant P227 has the chemical name bis(2-ethylhexyl)phosphonic acid or di(2-ethylhexyl)phosphonic acid, CAS number 13525-99-0, and its structure is as follows. .

[0062] The HEHAMP structure is as follows: .

[0063] The HEHHAP structure is as follows: .

[0064] Extractant P350 has the chemical name dimethylheptyl methylphosphonate and the structure is as follows: .

[0065] The extractant P113 has the chemical name of trialkylphosphine oxide or dihexyl(octyl)phosphine oxide. It is an organophosphorus compound composed of different alkyl substituents and has the CAS number 31160-64-2.

[0066] Extractant C923, also known as Cyanex 923, was developed by Cytec Corporation of the United States. Its Chinese name is generally straight-chain trialkylphosphine oxide, and its CAS number is 100786-00-3.

[0067] Extractant C925, also known as Cyanex 925, was developed by Cytec Corporation of the United States and is generally referred to as branched trialkylphosphine oxide in Chinese.

[0068] Extractant C230, also known as Cextrant 230, has the chemical name 1-(2-ethylhexylamino)methylphosphonic acid di(2-ethylhexyl) ester and the structural formula is: .

[0069] Extractant N235, also known as extractant 7301, trioctyldecyl tertiary amine, trioctyldecyl dimethyl tertiary amine, etc.

[0070] Extractant N1923, also known as N-1923 extractant, is chemically named secondary carbon primary amine extractant.

[0071] The diluent may be selected from aviation kerosene, sulfonated kerosene, liquid paraffin, C 5-16 Alkanes (e.g., pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, etc.), C 5-16 Alicyclic alkanes (e.g., cyclopentane, C) 1-4 Alkyl-substituted cyclopentanes, cyclohexanes, C 1-4 Alkyl-substituted cyclohexane, decahydronaphthalene, etc.), C 6-10 One or more of aromatic hydrocarbons (e.g., benzene, toluene, xylene (including ortho-, meta-, para-xylene and mixed xylenes)), preferably one or more of aviation kerosene, sulfonated kerosene, and heptane, more preferably sulfonated kerosene.

[0072] In some embodiments, the extraction system further includes a phase modifier.

[0073] The phase modifier may be one or more selected from n-octanol, isooctanol, sec-octanol, tributyl phosphate, and trioctyl phosphate, preferably sec-octanol.

[0074] In some embodiments, the volume ratio of extractant:phase modifier:diluent in the extraction system can be (1-30):(0-30):(50-90), preferably (10-30):(0-20):(50-70), such as 15:20:65, 30:20:50, 30:0:70, etc.

[0075] In some embodiments, the extractant in the extraction system is P507, the phase modifier is 2-octanol, and the diluent is sulfonated kerosene. The volume ratio of P507:2-octanol:sulfonated kerosene is (10-30):(10-20):(50-80).

[0076] In some embodiments, in step S2, the number of extraction stages is 1-8, more preferably 1-4, such as stages 1, 2, 3, and 4.

[0077] In some embodiments, in step S2, the volume V of the extraction system (organic phase) is... o Volume V of rare earth solution (aqueous phase) a The ratio can be from 1:10 to 10:1, preferably from 1:5 to 4:1, such as 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, etc.

[0078] Other steps

[0079] The method according to the invention may further include a step of treating the fluorine-loaded extraction system to recover the metal ions as a complexing agent and the extraction system.

[0080] In some embodiments, the step of treating the fluorine-loaded extraction system includes:

[0081] S3: Use a back-extraction agent to back-extract the fluorine-loaded extraction system to back-extract the fluorine and metal elements in the extraction system, and obtain the back-extracted extraction system and the back-extraction solution containing fluorine and metal elements.

[0082] In step S3, the stripping agent can be an alkaline aqueous solution. The alkali can be selected from hydroxides, carbonates, and phosphates of alkali metals, alkaline earth metals, and ammonia, such as sodium hydroxide, sodium carbonate, ammonium carbonate, ammonium bicarbonate, ammonia, potassium hydroxide, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, ammonium phosphate, etc. In some embodiments, the stripping agent is 0.5~5 mol / L, for example, an aqueous solution of sodium hydroxide with a concentration of 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, or 4.0 mol / L.

[0083] In step S3, the volume V of the fluorine-loaded extraction system (organic phase) is... o Volume V of the stripping agent st The ratio of V o / V st The ratio can be from 1:10 to 10:1, preferably from 1:5 to 4:1, such as 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, etc.

[0084] A washing step, which is optional, can be performed before the back-extraction in step S3. This washing step is optional; that is, the acid washing step may or may not be performed. Washing removes organic entrainment, resulting in a purer product. Washing can be performed using water or an alkaline aqueous solution. The type of alkali can be the same as that in the back-extraction agent. The alkalinity of the washing agent can be lower than that of the back-extraction agent.

[0085] The extraction system after back-extraction is essentially a blank extraction system and can be reused to extract fluorine, thereby achieving the recycling of the extraction system. Therefore, the method according to the invention may further include returning the back-extracted extraction system to step S2 for extraction of the rare earth solution.

[0086] An optional acid washing step can be performed before returning the back-extracted extraction system to step S2. This acid washing step is optional; it may or may not be performed.

[0087] In the acid washing step, the washing acid is preferably the same as the acid in the rare earth solution. For example, if the rare earth solution is a hydrochloric acid system, then the washing solution is preferably a hydrochloric acid solution. The acidity of the washing solution, expressed as hydrogen ion concentration, is 1~6 mol / L, but is not limited to this. The volume V of the extraction system (organic phase) o Volume V of washing acid (aqueous phase) a The ratio of V o / V a The ratio can range from 1:1 to 15:1, but is not limited to this.

[0088] The back-extraction solution contains fluorine and metal elements that act as fluorine complexing agents. The metal elements mainly exist in the form of precipitates such as hydroxides, carbonates, and phosphates. After filtering the back-extraction solution, the precipitates can be collected to recover the metal elements, which can be used directly as metal ion precursors or, after processing, transformed into metal ion precursors soluble in rare earth solutions and returned to step S1.

[0089] Therefore, the method according to the invention may further include the step of treating the back-extraction solution to recover the metal element as a fluorine complexing agent.

[0090] Furthermore, the method according to the invention may also include a fluoride-containing wastewater treatment step to remove fluoride from the wastewater. This fluoride-containing wastewater treatment step may, for example, be carried out using a calcium salt precipitation method, in which a calcium precursor is added to the fluoride-containing wastewater to form calcium fluoride precipitate.

[0091] Furthermore, the method according to the present invention may also include the step of treating a low-fluorine rare earth solution to obtain a rare earth product.

[0092] In this invention, rare earth elements refer to lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium, and scandium.

[0093] In the rare earth solution of this invention, all rare earth elements are trivalent ions.

[0094] In this invention, zirconium and hafnium ions refer to tetravalent ions.

[0095] In this invention, unless otherwise stated, all solutions are aqueous solutions.

[0096] In this document, all features or conditions defined in the form of numerical ranges or percentage ranges are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible secondary ranges and individual values ​​within those ranges, particularly integer values. For example, a range description of "1 to 8" should be considered as specifically disclosing all secondary ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., particularly secondary ranges defined by all integer values, and should be considered as specifically disclosing individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, 8, etc. Unless otherwise specified, the foregoing interpretation applies to all content throughout this invention, regardless of its scope.

[0097] The present invention has been described in detail above, but the present invention is not limited to the above content.

[0098] Beneficial effects

[0099] This invention achieves preferential extraction and removal of fluorine complexes by selecting zirconium, hafnium, or a mixture of the two in any proportion with strong complexing ability with fluorine in a low-acid solution, and the fluorine complexing agent can be recycled.

[0100] This invention uses conventional extraction methods to remove fluoride. The extraction process is continuous and highly controllable, solving the problems of large slag volume and difficult filtration faced by precipitation and impurity removal.

[0101] The method described in this invention is applicable to both high-fluoride and low-fluoride solutions, and is particularly suitable for the efficient removal of fluoride from high-fluoride solutions. Detailed Implementation

[0102] The present invention will be further illustrated by the following embodiments, but the embodiments provided are merely to help understand the present invention and are not intended to limit the present invention.

[0103] Reagents and sources

[0104] P507 (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) and P204 (diisooctyl phosphate) were purchased from Sanmenxia Zhongda Chemical Co., Ltd.

[0105] C272 (bis(2,4,4-trimethylpentyl)phosphonic acid) was purchased from Guangzhou Yuanda New Materials Co., Ltd.

[0106] C923 (linear trialkylphosphine oxide) was purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.

[0107] P113 (trialkylphosphine oxide) was purchased from Shanghai Laya Chemical Co., Ltd.

[0108] N235 (trioctyldecyl tertiary amine) and N1923 (secondary carbon primary amine extractant) were purchased from Jiangxi Jiexin Technology Co., Ltd.

[0109] 2-Octanol was purchased from adamas-beta.

[0110] Isooctyl alcohol was purchased from Sigma-Aldrich.

[0111] The sulfonated kerosene was purchased from Jiangxi Jiexin Technology Co., Ltd.

[0112] Sodium fluoride was purchased from General-Reagent.

[0113] Analytical grade sodium hydroxide, analytical grade hydrochloric acid, and analytical grade concentrated sulfuric acid were purchased from Xilong Scientific Co., Ltd.

[0114] C230 (1-(2-ethylhexylamino)methylphosphonic acid di(2-ethylhexyl) ester) was synthesized according to the method in CN201410765062.1.

[0115] HEHAMP (2-ethylhexylaminomethylphosphonic acid mono-2-ethylhexyl ester): Obtained by hydrolysis of C230. The specific procedure is as follows: 40 g of C230, 100 mL of 75% ethanol, 5.6 g of potassium hydroxide, and 0.2 wt% of potassium iodide (KI, mass percentage relative to C230) were placed in a 250 mL round-bottom flask and refluxed at 90 °C for 8 h. After the reaction was completed and cooled to room temperature, the ethanol was removed by rotary evaporation, yielding a viscous, turbid yellow liquid. This liquid was dissolved in 200 mL of ethyl acetate and transferred to a 500 mL separatory funnel. The liquid was washed several times with 0.5 mol / L dilute hydrochloric acid and saturated brine until the aqueous phase was weakly acidic (pH ≈ 5.5~6). The organic matter was dried over anhydrous sodium sulfate, rotary evaporated, and then distilled under reduced pressure to obtain the target product.

[0116] The rare earth solution used in this invention is obtained from a company, and its main components are shown in the table below.

[0117]

[0118] Note: Total rare earth ion concentration is expressed as rare earth oxides.

[0119] Fluoride ion concentration was measured using a Leici PXSJ-216F ion meter.

[0120] The fluoride removal rate η is calculated as follows:

[0121]

[0122] η: Fluorine removal rate (%); c t : Fluoride ion concentration in the raffinate (g / L); c i: Initial F ion concentration (g / L) in the prepared rare earth solution.

[0123] Example 1

[0124] Organic phase: The organic phase is obtained by mixing 30% P507, 20% octanol and 50% sulfonated kerosene by volume.

[0125] Zirconium sulfate solution: = 81.37 g / L, = 2.81 mol / L.

[0126] Sodium fluoride solution: 15.13 g / L (calculated as fluoride ions).

[0127] Rare earth solution: Add appropriate amounts of zirconium sulfate solution and sodium fluoride solution to rare earth mother liquor A-1 at a final zirconium-fluoride molar ratio of 3.42:1 and stir for 30 minutes. Then adjust the acidity with concentrated sulfuric acid. The final rare earth solution... c (H + ) =2.00 mol / L, fluoride ion concentration is 2190 mg / L.

[0128] Four-stage countercurrent extraction was performed with an organic phase (Vo) to rare earth solution (Va) flow ratio of 4:1 (Vo / Va) to obtain a fluorine-loaded organic phase and raffinate. The fluoride ion concentration in the raffinate was 129 mg / L, and the fluoride removal rate was 94.11%. Key data are summarized in Table 1.

[0129] Example 2

[0130] Organic phase: The organic phase is obtained by mixing 30% P507, 10% isooctyl alcohol, and 60% sulfonated kerosene by volume.

[0131] Hafnium sulfate solution: = 65.87 g / L, = 2.77 mol / L.

[0132] Sodium fluoride solution: 15.13 g / L (calculated as fluoride ions).

[0133] Rare earth solution: Add appropriate amounts of hafnium sulfate solution and sodium fluoride solution to rare earth mother liquor A-1 according to a final hafnium-fluorine molar ratio of 3.10:1 and stir for 30 minutes. Then adjust the acidity with concentrated sulfuric acid. The final rare earth solution... c (H + ) =2.00 mol / L, fluoride ion concentration is 285 mg / L.

[0134] Four-stage countercurrent extraction was performed with an organic phase (Vo) to rare earth solution (Va) flow ratio of 1:1 (Vo / Va) to obtain a fluorine-loaded organic phase and raffinate. The fluoride ion concentration in the raffinate was measured to be 82 mg / L, with a fluoride removal rate of 71.23%. Key data are summarized in Table 1.

[0135] Example 3

[0136] Organic phase: The organic phase is obtained by mixing 30% P2O4, 10% isooctyl alcohol, and 60% sulfonated kerosene by volume.

[0137] Zirconium sulfate solution: = 81.37 g / L, = 2.81 mol / L.

[0138] Sodium fluoride solution: 15.13 g / L (calculated as fluoride ions).

[0139] Rare earth solution: A suitable amount of zirconium sulfate solution and sodium fluoride solution were added to rare earth mother liquor A-1 and stirred for 30 minutes, according to a final total zirconium-fluorine molar ratio of 1.05:1. The final rare earth solution... c (H + ) =0.10 mol / L, fluoride ion concentration is 275 mg / L.

[0140] Two-stage countercurrent extraction was performed with an organic phase (Vo) to rare earth solution (Va) flow ratio of 1:1 (Vo / Va) to obtain a fluorine-loaded organic phase and raffinate. The fluoride ion concentration in the raffinate was 231 mg / L, and the fluoride removal rate was 16.00%. Key data are summarized in Table 1.

[0141] Example 4

[0142] Organic phase: The organic phase is obtained by mixing 30% P507, 20% octanol and 50% sulfonated kerosene by volume.

[0143] Zirconium chloride solution: = 77.52 g / L, = 2.37 mol / L.

[0144] Sodium fluoride solution: 15.13 g / L (calculated as fluoride ions).

[0145] Rare earth solution: A suitable amount of zirconium chloride solution and sodium fluoride solution were added to rare earth mother liquor B-1 and stirred for 40 minutes at a final zirconium-fluoride molar ratio of 2.25:1. The final rare earth solution... c (H + )=0.49 mol / L, fluoride ion concentration is 822 mg / L.

[0146] Back-extraction agent: 2 mol / L NaOH aqueous solution.

[0147] (1) Four-stage countercurrent extraction was performed with a flow ratio of organic phase (Vo) to rare earth solution (Va) of 1:1 to obtain fluorine-loaded organic phase and raffinate. The concentration of fluoride ions in the raffinate was 41 mg / L, and the fluoride removal rate was 95.01%. The main data are summarized in Table 1.

[0148] (2) According to the fluorine-loaded organic phase (Vo) and the stripping agent (V st The volume ratio V o / V st The mixture was back-extracted at a ratio of 1:1 to obtain a recycled organic phase and an aqueous phase. The aqueous phase was then centrifuged to obtain solid zirconium hydroxide.

[0149] (3) According to the circulating organic phase (V o ) and 3 mol / L hydrochloric acid aqueous solution (V w The volume ratio V o / V w The solution was acid-washed at a ratio of 1:1 to separate the circulating organic phase. Then, the above step (1) was repeated using the circulating organic phase for extraction. The fluoride ion concentration in the resulting raffinate was 46 mg / L, and the fluoride removal rate was 94.40%.

[0150] (4) Dissolve the obtained zirconium hydroxide solid in 6 mol / L hydrochloric acid aqueous solution, and add it together with an appropriate amount of sodium fluoride solution to rare earth mother liquor B-1 and stir for 30 min. After the solution is prepared, c (H + ) The concentration was 1.22 mol / L, the total molar ratio of zirconium to fluorine was 1.92:1, and the fluoride ion concentration was 753 mg / L. The above step (1) was repeated using this rare earth solution for extraction. The fluoride ion concentration in the resulting raffinate was 44 mg / L, and the fluoride removal rate was 94.16%.

[0151] The experimental results of steps (2) to (4) show that both the organic phase and the fluorinated complexing agent can maintain good cycling performance.

[0152] Example 5

[0153] Organic phase: The organic phase is obtained by mixing 30% P507, 20% octanol and 50% sulfonated kerosene by volume.

[0154] zirconium hafnium chloride solution: = 77.84 g / L, = 1.55 g / L, = 2.52 mol / L.

[0155] Sodium fluoride solution: 15.13 g / L (calculated as fluoride ions).

[0156] Rare earth solution: Add appropriate amounts of zirconium chloride-hafnium chloride and sodium fluoride solution to rare earth mother liquor B-1, according to a final (zirconium + hafnium) to fluorine molar ratio of 2.25:1. Stir for 40 minutes, then adjust the acidity with concentrated hydrochloric acid. The final rare earth solution... c (H + ) =0.90 mol / L, fluoride ion concentration is 822 mg / L.

[0157] Four-stage countercurrent extraction was performed with an organic phase (Vo) to rare earth solution (Va) flow ratio of 1:1 (Vo / Va) to obtain a fluorine-loaded organic phase and raffinate. The fluoride ion concentration in the raffinate was 33 mg / L, and the fluoride removal rate was 95.99%. Key data are summarized in Table 1.

[0158] Example 6

[0159] Organic phase: The organic phase was obtained by mixing 15% P507, 20% octanol, and 65% sulfonated kerosene by volume.

[0160] Zirconium chloride solution: = 77.52 g / L, = 2.37 mol / L.

[0161] Rare earth solution: A suitable amount of zirconium chloride solution was added to rare earth mother liquor B-1 and stirred for 40 minutes to obtain the final rare earth solution, with a final zirconium-fluorine molar ratio of 2.82:1. c (H + ) =0.55 mol / L, fluoride ion concentration is 645 mg / L.

[0162] Four-stage countercurrent extraction was performed with an organic phase (Vo) to rare earth solution (Va) flow ratio of 1:1 (Vo / Va) to obtain a fluorine-loaded organic phase and raffinate. The fluoride ion concentration in the raffinate was 48 mg / L, and the fluoride removal rate was 92.56%. Key data are summarized in Table 1.

[0163] Example 7

[0164] Organic phase: The organic phase was obtained by mixing 18% P507, 20% octanol, and 62% sulfonated kerosene by volume.

[0165] Except for the different organic phase, the other operations were the same as in Example 6. The concentration of fluoride ions in the raffinate was measured to be 22 mg / L, with a fluoride removal rate of 96.59%. The main data are summarized in Table 1.

[0166] Example 8

[0167] Organic phase: The organic phase was obtained by mixing 30% HEHAMP, 20% octanol, and 50% sulfonated kerosene by volume.

[0168] Zirconium chloride solution: = 77.52 g / L, = 2.37 mol / L.

[0169] Sodium fluoride solution: 15.13 g / L (calculated as fluoride ions).

[0170] Rare earth solution: A suitable amount of zirconium chloride solution and sodium fluoride solution were added to rare earth mother liquor B-1 and stirred for 20 minutes at a final total zirconium-fluorine molar ratio of 1.75:1. The final rare earth solution... c (H + ) =0.55mol / L, fluoride ion concentration is 1170 mg / L.

[0171] Four-stage countercurrent extraction was performed with an organic phase (Vo) to rare earth solution (Va) flow ratio of 1:1 (Vo / Va) to obtain a fluorine-loaded organic phase and raffinate. The fluoride ion concentration in the raffinate was 157 mg / L, and the fluoride removal rate was 86.58%. Key data are summarized in Table 1.

[0172] Example 9

[0173] Organic phase: The organic phase is obtained by mixing 30% C272, 20% octanol and 50% sulfonated kerosene by volume.

[0174] Except for the organic phase, the other operations were the same as in Example 8. The fluoride ion concentration in the raffinate was measured to be 184 mg / L, with a fluoride removal rate of 84.27%. Key data are summarized in Table 1. During the extraction process, it was found that the aqueous phase was not clear, and severe oil-water mixing was observed.

[0175] Example 10

[0176] Organic phase: The organic phase is obtained by mixing 30% C230 and 70% sulfonated kerosene by volume.

[0177] Zirconium sulfate solution: = 81.37 g / L, = 2.81 mol / L.

[0178] Rare earth solution: A suitable amount of zirconium sulfate solution was added to rare earth mother liquor A-1 and stirred for 20 minutes to obtain the final rare earth solution, with a final zirconium-fluorine molar ratio of 3.72:1. c (H + ) =0.60 mol / L, fluoride ion concentration is 241 mg / L.

[0179] Then, a first-stage extraction was performed with a volume ratio of organic phase (Vo) to rare earth solution (Va) of 1:1 (Vo / Va) to obtain a fluorine-loaded organic phase and raffinate. The fluoride ion concentration in the raffinate was measured to be 121 mg / L, and the fluoride removal rate was 49.79%. The main data are summarized in Table 1.

[0180] Example 11

[0181] Organic phase: The organic phase is obtained by mixing 15% C230 + 15% P507 + 70% sulfonated kerosene by volume.

[0182] Except for the different organic phase, the other operations were the same as in Example 10. The concentration of fluoride ions in the raffinate was measured to be 124 mg / L, and the fluoride removal rate was 48.55%. The main data are summarized in Table 1.

[0183] Example 12

[0184] Organic phase: The organic phase is obtained by mixing 30% C923 and 70% sulfonated kerosene by volume.

[0185] Zirconium sulfate solution: = 81.37 g / L, = 2.81 mol / L.

[0186] Sodium fluoride solution: 15.13 g / L (calculated as fluoride ions).

[0187] Rare earth solution: A suitable amount of zirconium sulfate solution and sodium fluoride solution were added to rare earth mother liquor A-1 and stirred for 30 minutes at a final total zirconium-fluorine molar ratio of 1.48:1. The final rare earth solution... c (H + ) =0.60 mol / L, fluoride ion concentration is 298 mg / L.

[0188] Two-stage cross-flow extraction was performed with an organic phase (Vo) to rare earth solution (Va) flow ratio of 1:5 (Vo / Va) to obtain a fluorine-loaded organic phase and raffinate. The fluoride ion concentration in the raffinate was 36 mg / L, and the fluoride removal rate was 87.92%. The main data are summarized in Table 1.

[0189] Example 13

[0190] Organic phase: The organic phase is obtained by mixing 30% P113, 20% octanol, and 50% sulfonated kerosene by volume percentage.

[0191] Zirconium chloride solution: = 77.52 g / L, = 2.37 mol / L.

[0192] Sodium fluoride solution: 15.13 g / L (calculated as fluoride ions).

[0193] Rare earth solution: A suitable amount of zirconium chloride solution and sodium fluoride solution were added to rare earth mother liquor B-1 and stirred for 30 minutes at a final total zirconium-fluorine molar ratio of 1:1.51. The final rare earth solution... c (H + ) =0.50 mol / L, fluoride ion concentration is 837 mg / L.

[0194] A first-stage extraction was performed with an organic phase (Vo) to rare earth solution (Va) volume ratio of 1:1 (Vo / Va) to obtain a fluorine-loaded organic phase and raffinate. The fluoride ion concentration in the raffinate was 553 mg / L, and the fluoride removal rate was 33.93%. The main data are summarized in Table 1.

[0195] Example 14

[0196] Organic phase: The organic phase is obtained by mixing 30% N235 and 70% sulfonated kerosene by volume.

[0197] Zirconium sulfate solution: = 81.37 g / L, = 2.81 mol / L.

[0198] Sodium fluoride solution: 15.13 g / L (calculated as fluoride ions).

[0199] Rare earth solution: Add appropriate amounts of zirconium sulfate solution and sodium fluoride solution to rare earth mother liquor A-1 at a final total zirconium-fluorine molar ratio of 2.03:1 and stir for 30 minutes. Then adjust the acidity with concentrated sulfuric acid. The final rare earth solution... c (H + ) =1.50 mol / L, fluoride ion concentration is 3000 mg / L.

[0200] Three-stage cross-flow extraction was performed with an organic phase (Vo) to rare earth solution (Va) flow ratio of 1:1 (Vo / Va) to obtain a fluorine-loaded organic phase and raffinate. The fluoride ion concentration in the raffinate was 950 mg / L, and the fluoride removal rate was 68.33%. Key data are summarized in Table 1.

[0201] Example 15

[0202] Organic phase: The organic phase is obtained by mixing 30% N1923 and 70% sulfonated kerosene by volume.

[0203] Except for the different organic phase, the other operations were the same as in Example 12. The concentration of fluoride ions in the raffinate was measured to be 156 mg / L, and the fluoride removal rate was 47.65%. The main data are summarized in Table 1.

[0204] Table 1. Statistical table of fluoride ion concentration and fluoride extraction rate before and after fluoride removal extraction.

[0205]

[0206] As shown in Table 1, the preferred P507 extractant can effectively extract and remove fluoride from rare earth solutions even at high fluoride concentrations, achieving an extraction rate exceeding 92.56% under optimal conditions. Comparing Examples 1 and 2, 2-octanol is preferred as a phase modifier; comparing Examples 4-7, the extractant concentration can be determined through conventional experiments based on actual conditions such as the fluoride content in the solution, the molar ratio of fluoride to the complexing agent, and the solution acidity.

[0207] The above embodiments are merely exemplary embodiments of the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications or substitutions can be made without departing from the spirit and essence of the present invention, and these modifications or substitutions are also within the protection scope of the present invention.

Claims

1. A method for defluorination by rare earth solution extraction, characterized in that, The method includes: S1: Metal ions selected from zirconium and hafnium ions are introduced into a rare earth solution; wherein, the rare earth solution is an acidic solution containing one or more rare earth ions and fluoride ions. S2: Extract the rare earth solution to remove fluorine, resulting in a low-fluorine rare earth solution. Step S2 is performed as follows: the rare earth solution is extracted using an extraction system to extract fluorine, resulting in a fluorine-loaded extraction system and a raffinate. The extraction system includes an extractant and a diluent, as well as a phase modifier (not essential). The extractant is selected from the following extractants: (1) Acidic phosphorus or phosphine extractant of formula I: Among them, R 11 and R 12 Each was independently selected from C 1-12 Alkyl, C 1-12 Alkoxy, C 5-10 Alicyclic alkyl groups, C 5-10 Alicyclic alkoxy groups, C 6-10 Aryl and C 6-10 aryloxy, R 11 and R 12 The total number of carbon atoms ranges from 8 to 24; (2) Amino acid-containing phosphine extractant of formula II: Among them, R 21 Selected from C 1-12 Alkyl, C 1-12 Alkoxy; R 22 and R 23 Each is independently selected from hydrogen and C. 1-8 Alkyl, C 5-10 Alicyclic alkyl groups and C 6-10 Aryl; R 24 and R 25 Each was independently selected from C 1-16 Alkyl and hydrogen, and R 24 and R 25 At most one is hydrogen; R 21 R 22 R 23 R 24 and R 25 The total number of carbon atoms is between 8 and 30; (3) Neutral phosphorus or phosphine extractants of Formula III: Among them, R 31 R 32 and R 33 Each was independently selected from C 1-10 Alkyl and C 1-10 Alkoxy groups, and R 31 R 32 and R 33 The total number of carbon atoms is between 8 and 30; (4) Formula IV containing amino-containing neutral phosphorus or phosphine extractants: Among them, R 41 and R 42 Each was independently selected from C 1-12 Alkyl, C 1-12 Alkoxy; R 43 and R 44 Each is independently selected from hydrogen and C. 1-8 Alkyl, C 5-10 Alicyclic alkyl groups and C 6-10 Aryl; R 45 and R 46 Each was independently selected from C 1-16 Alkyl and hydrogen, and R 45 and R 46 At most one is hydrogen; R 41 R 42 R 43 R 44 R 45 and R 46 The total number of carbon atoms ranges from 8 to 32; (5) Amine extractant of formula V: Among them, R 51 R 52 and R 53 Each is independently selected from H and C. 7-23 Alkyl, and R 51 R 52 and R 53 At least one of them is not hydrogen; R 51 R 52 and R 53 The total number of carbon atoms ranges from 8 to 32; The diluent is selected from aviation kerosene, sulfonated kerosene, liquid paraffin, and C. 5-16 Alkanes, C 5-16 Alicyclic alkanes, C 6-10 One or more of the aromatic hydrocarbons; The phase modifier is selected from one or more of n-octanol, isooctanol, sec-octanol, tributyl phosphate, and trioctyl phosphate.

2. The method according to claim 1, characterized in that, The acidic solution is selected from hydrochloric acid solution, sulfuric acid solution, and nitric acid solution; and / or In rare earth solutions, the concentration of rare earth elements, calculated as rare earth oxides, is 1–250 g / L; the concentration of fluoride ions is 50–5000 mg / L; the concentration of hydrogen ions is 0.01–2 mol / L; and / or The molar ratio of the introduced metal ions to fluoride ions in the rare earth solution is 5:1 to 1:

5.

3. The method according to claim 1, characterized in that, The molar ratio of the introduced metal ions to fluoride ions in the rare earth solution is 4:1 to 1:

4.

4. The method according to claim 1, characterized in that, In formula I, R 11 and R 12 Each was independently selected from C 4-12 Alkyl, C 4-12 Alkoxy, C 5-10 Alicyclic alkyl groups, C 5-10 Alicyclic alkoxy groups, C 6-10 Aryl and C 6-10 aryloxy groups, and / or R 11 and R 12 The total number of carbon atoms is 10-18; and / or In Equation II, R 21 Selected from C 4-12 Alkyl, C 4-12 Alkoxy; R 22 and R 23 Each is independently selected from hydrogen and C. 1-4 Alkyl, C 5-8 Alicyclic alkyl and phenyl groups; R 24 and R 25 Each was independently selected from C 1-10 Alkyl and hydrogen, and R 24 and R 25 At most one is hydrogen; and / or R 21 R 22 R 23 R 24 and R 25 The total number of carbon atoms is 10⁻²⁴; and / or In Equation III, R 31 R 32 and R 33 Each was independently selected from C 1-8 Alkyl and C 1-8 alkoxy, and / or R 31 R 32 and R 33 The total number of carbon atoms is 10⁻²⁴; and / or In equation IV, R 41 and R 42 Each is independently selected from C 4-12 Alkyl, C 4-12 Alkoxy; R 43 and R 44 Each is independently selected from hydrogen and C. 1-4 Alkyl, C 5-8 Alicyclic alkyl and phenyl groups; R 45 and R 46 Each is independently selected from C 1-10 Alkyl and hydrogen, and R 45 and R 46 At most one is hydrogen; and / or R 41 R 42 R 43 R 44 R 45 and R 46 The total number of carbon atoms is 10⁻²⁸; and / or In formula V, R 51 R 52 and R 53 The total number of carbon atoms is 10-30; and / or The diluent is one or more selected from aviation kerosene, sulfonated kerosene, and heptane; and / or The phase modifier is 2-octanol.

5. The method according to claim 1, characterized in that, The acidic phosphorus or phosphonic acid extractant shown in Formula I is selected from di(2-ethylhexyl)phosphoric acid, mono-2-ethylhexyl 2-ethylhexylphosphonate, di(2,4,4-trimethylpentyl)phosphonic acid, di(2-ethylhexyl)phosphonic acid; and / or The amino acid-containing phosphine extractant shown in Formula II is selected from 2-ethylhexylaminomethylphosphonic acid mono-2-ethylhexyl ester and heptamethylaminomethylphosphonic acid mono-2-ethylhexyl ester; and / or The neutral phosphorus or phosphine extractant shown in Formula III is selected from dimethylheptyl methylphosphonate, trialkylphosphine oxide P113, linear trialkylphosphine oxide C923, branched trialkylphosphine oxide C925; and / or The amino-containing neutral phosphorus or phosphine extractant shown in Formula IV is selected from 1-(2-ethylhexylamino)methylphosphonate di(2-ethylhexyl); 1-(2-ethylhexylamino)-1-phenylmethylphosphonate di(2-ethylhexyl); 1-(2-ethylhexylamino)-1-methylethylphosphonate di(2-ethylhexyl); 1-(2-ethylhexylamino)-1-methylpropylphosphonate di(2-ethylhexyl); 1-(2-ethylhexylamino)-1-ethylpropylphosphonate di(2-ethylhexyl); 1-(N-dodecylamino)-1-methylethylphosphonate diethyl ester; 1-(2-ethylhexylamino)-n-propylphosphonate di(2-ethylhexyl); 1-(N-butylamino)ethylphosphonate di(2-ethylhexyl); and / or The amine extractant of formula V is selected from trioctyldecyl tertiary amine N235, secondary carbon primary amine extractant N1923; and / or The diluent is sulfonated kerosene.

6. The method according to claim 1, characterized in that, In the extraction system, the volume ratio of extractant:phase modifier:diluent is (1-30):(0-30):(50-90).

7. The method according to claim 6, characterized in that, In the extraction system, the volume ratio of extractant:phase modifier:diluent is (10-30):(0-20):(50-70).

8. The method according to claim 1, characterized in that, In the extraction system, the extractant is P507, the phase modifier is 2-octanol, and the diluent is sulfonated kerosene. The volume ratio of P507:2-octanol:sulfonated kerosene is (10-30):(10-20):(50-80).

9. The method according to claim 1, characterized in that, In step S2, the number of extraction stages is 1-8; the volume V of the extraction system is... o With the volume V of the rare earth solution a The ratio is 1:10 to 10:

1.

10. The method according to claim 1, characterized in that, The method further includes a step of treating the fluorine-loaded extraction system to recover the metal ions used as complexing agents and the extraction system.

11. The method according to claim 10, characterized in that, The steps for processing the fluorine-loaded extraction system include: S3: Use a back-extraction agent to back-extract the fluorine-loaded extraction system to back-extract the fluorine and metal elements in the extraction system, and obtain the back-extracted extraction system and the back-extraction solution containing fluorine and metal elements. The stripping agent is an alkaline aqueous solution, wherein the alkali in the alkaline aqueous solution is selected from alkali metals, alkaline earth metals, and hydroxides, carbonates, and phosphates of ammonia. Volume V of the fluorine-loaded extraction system o Volume V of the stripping agent st The ratio of V o / V st The ratio is 1:10 to 10:

1.

12. The method according to claim 11, characterized in that, The method further includes: Return the back-extraction extraction system to step S2 for extraction of the rare earth solution; and / or The step of treating the back-extraction solution to recover the metal element used as a fluorine complexing agent.

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