Pretreatment method for defluorination of fluorine-containing mixed rare earth chloride feed liquid

Abstract

The invention provides a method for removing fluorine in the extraction and separation process of a rare earth chloride system through pre-oxidation reduction of cerium. According to the method, a fluorine removal pretreatment method is provided before the extraction and separation process, tetravalent cerium is obtained through pre-oxidation, meanwhile, fluorine and cerium coordination substances are extracted in advance in an extraction system by controlling the temperature and time and utilizing the coordination characteristic of tetravalent cerium and fluorine ions to achieve fluorine removal, and it is guaranteed that follow-up rare earth extraction and separation are conducted smoothly. According to the method, the industrial common problem that in the extraction and separation process of the fluorine-containing rare earth chloride feed liquid, fluorine ions are accumulated in an extraction system, so that three-phase substances are continuously gathered in the rare earth extraction and separation process, and the extraction operation is disordered is solved.

Description

Technical Field

[0001] The invention relates to the technical field of impurity removal from fluorine-containing mixed rare earth chloride material liquid, and in particular to a method for pre-defluorinating a rare earth chloride material liquid containing trace fluorine obtained by dissolving ionic rare earth concentrate with hydrochloric acid. Background Art

[0002] Rare earth elements are a general term for 17 elements including lanthanide elements, yttrium, and scandium. Rare earth elements have a wide range of uses. When combined with other elements, they can form new materials with a wide variety of functions. They are widely used in many fields such as metallurgy, machinery, petroleum, chemical industry, electronics, optical instruments, agriculture, communications, and military industry.

[0003] At present, the world's rare earths mainly come from Baotou mixed rare earth concentrate, fluorocarbon cerium ore, monazite ore and ion adsorption rare earth ore. Among them: Ion adsorption type rare earth ore adopts in-situ leaching technology, that is, in the process of in-situ leaching using ammonium sulfate as raw material, the collected leachate is rare earth sulfate solution, which contains aluminum ions, fluoride ions, etc. that are harmful to the subsequent production process. The ammonium sulfate leachate is partially removed by adjusting the pH value and precipitated with ammonium carbonate to obtain an ionic mixed rare earth carbonate concentrate or calcined at 800℃~1000℃ to obtain an oxide type ionic mixed concentrate. The rare earth concentrate is dissolved by hydrochloric acid and enters the rare earth extraction and separation system after impurities are removed to obtain a single rare earth or rare earth enrichment. Common impurity removal methods include preferential dissolution, pH adjustment, etc., but the overall fluorine removal effect is limited, and a fluorine-containing rare earth chloride solution of 0.2%~0.7% (F / ΣREO) is obtained, which enters the subsequent process of extraction and separation.

[0004] The oxidative roasting-hydrochloric acid leaching process currently commonly used for fluorocarbon cerium ore is used to obtain a rare earth chloride liquid containing less cerium. In production, due to insufficient clarification time and inadequate pH adjustment, a fluorine-containing rare earth chloride solution containing less cerium is obtained, in which the F / ΣREO is 0.3-0.8%, which enters the subsequent extraction and separation process.

[0005] The practice of rare earth extraction and separation has found that when there is an excess of fluoride ions in the rare earth chloride liquid (fluoride content greater than 0.2%), a three-phase product will be produced, which will seriously affect the subsequent extraction and separation production after gradual accumulation. The specific situation is as follows: before entering the tank, fluoride ions and trivalent rare earths will stably exist within a certain concentration range and time range. After entering the extraction and separation system, as the residence time increases, the local pH value increases. In the presence of trivalent rare earths and other impurities, fluoride insolubles are generated, which emulsifies the organic extractant to produce flocculent three-phase products, making it difficult to separate the organic and aqueous phases, reducing the extraction and separation efficiency, and the product quality is unqualified. In severe cases, it causes the extraction material to be entrained, inverted, or even blocked and stopped. At the same time, fluoride ions enter the wastewater, causing problems for the original wastewater treatment system. Therefore, it is particularly urgent to find a method to remove fluorine-containing impurities in mixed rare earth chlorides.

[0006] The invention patent with application number CN202211729095.1 discloses a method for removing fluorine from rare earth concentrates, wherein solution A is added to the fluorine-containing rare earth concentrate, mixed evenly, and then heated and burned. Solution B is used to treat the gas generated during the burning process, and after the burning process, a rare earth concentrate with a low fluorine content is obtained. However, this method uses roasting to remove fluorine, and fluorine-containing waste gas is generated during the roasting process. It is difficult to control the overflow of fluorine-containing waste gas during the process, which will cause environmental pollution, and the fluorine element cannot be well utilized.

[0007] In addition, in the field of rare earth extraction and separation, it is generally believed that a large amount of tetravalent cerium can only exist stably in a non-reducing sulfuric acid system or nitric acid system, but it is difficult for a large amount of tetravalent cerium to exist stably for a long time in a slightly acidic chloride system. How to ensure the existence of stable tetravalent cerium in the chloride system, so as to ensure that the tetravalent cerium can preferentially coordinate with fluorine and load the organic phase, so as to achieve the purpose of fluorine removal, is also an urgent problem to be solved. Summary of the invention

[0008] The present invention provides a pretreatment method before rare earth extraction and separation of fluorine-containing rare earth chloride material liquid, that is, before the extraction and separation process of the rare earth chloride material liquid, the cerium element in the rare earth chloride solution is partially oxidized, and the property of fluorine and tetravalent cerium forming a complex that is easy to extract is utilized to achieve extraction and separation with trivalent rare earth, and then a reducing agent is used in the stripping section to reduce the tetravalent cerium to trivalent cerium, and the property that trivalent cerium is easy to be stripped under high acid and trivalent cerium and a small amount of fluorine are not precipitated is utilized to achieve the co-stripping of trivalent cerium and fluorine, and the trivalent cerium and fluorine enter the stripping solution in a dissolved form.

[0009] The present invention provides a pretreatment method for removing fluorine from a fluorine-containing mixed rare earth chloride material liquid, comprising an extraction section, a washing section and a reduction stripping section, and the steps of each section are as follows: Extraction section: In the extraction section, the trivalent cerium in the fluorine-containing mixed rare earth chloride material liquid is oxidized to tetravalent cerium, and mixed with a blank organic phase to react to obtain a defluorinated rare earth chloride material liquid and a loaded organic phase, wherein the loaded organic phase contains a fluorine-cerium coordination compound and a small amount of trivalent rare earth; Washing section: In the washing section, the loaded organic phase obtained in the extraction section is washed with acid, so that the trivalent rare earth in the organic phase returns to the extraction section, and the organic phase loaded with fluorine cerium coordination is obtained in the washing section; Stripping section: Reducing agent and stripping acid are added in the stripping section, and the organic phase loaded with fluorine cerium coordination compound is stripped by reduction and acid addition to obtain stripping solution containing trivalent cerium and fluorine and blank organic solution, which is returned to the extraction section for recycling.

[0010] In certain implementations of the present invention, the extraction section comprises the following process steps: subjecting the fluorine-containing mixed rare earth chloride material liquid to cerium oxidation at 30-60°C, rapidly contacting with a blank organic phase for extraction and separation during the oxidation process, and the contact time and separation time of the aqueous phase and the organic phase during the extraction process are both no more than 20 seconds.

[0011] In certain implementations of the present invention, the oxidation in the extraction stage includes at least one of electrolytic oxidation and oxidation with a water-soluble oxidizing agent. Further, the oxidation with a water-soluble oxidizing agent is potassium permanganate.

[0012] In certain implementations of the present invention, the fluorine-containing rare earth chloride material liquid described in the pretreatment method for defluorination of the fluorine-containing mixed rare earth chloride material liquid provided by the present invention has a rare earth content of 50-300 gREO / L, F / ΣREO of 0.1-1.0%wt, and an acidity of 0.01-0.2 mol / L.

[0013] In certain implementations of the present invention, the washing acid in the washing section is at least one of hydrochloric acid, nitric acid and sulfuric acid, preferably hydrochloric acid, with an acidity of 0.2-0.7 mol / L.

[0014] In certain implementations of the present invention, the stripping acid in the stripping section is at least one of hydrochloric acid, nitric acid and sulfuric acid, preferably hydrochloric acid, and the acidity of the stripping acid is 1.5-3 mol / L.

[0015] In certain implementations of the present invention, in the extraction stage, the molar ratio of F / tetravalent Ce is 1-2.

[0016] In certain implementations of the present invention, the reducing agent in the stripping section is at least one of hydrogen peroxide, oxalic acid, thiourea, and ascorbic acid.

[0017] In certain implementations of the present invention, the organic phase described in the pretreatment method for defluorination of a fluorine-containing mixed rare earth chloride material liquid provided by the present invention is composed of at least one of the acidic extractants of P204, P507, and C272 and a diluent, and the diluent includes but is not limited to at least one of hydrogenated kerosene and white oil, and its bromine value is less than 10 mg.

[0018] Compared with the prior art, the present invention has the following advantages: The invention provides a method for pre-treating and removing fluorine before the extraction and separation process of rare earth chlorides, and relates to the technical field of rare earth separation. The method is completed in an extraction and separation operation unit, has simple operation, and is easy to connect with subsequent extraction and separation processes.

[0019] The extraction and separation system provided by the present invention is a pretreatment of the chloride material liquid for rare earth extraction and separation, which can not only solve the problem of high fluorine content, but also realize the pre-contact between the material liquid and the extraction and separation system to a certain extent, thereby improving the extraction performance of the fluorine-removing rare earth chloride material liquid.

[0020] The method provided by the present invention can directly remove part of the low-value cerium element, which not only solves the interference of fluorine, but also realizes the pre-extraction separation of part of the cerium, which can improve the subsequent extraction and separation capacity of the rare earth chloride liquid for fluorine removal. In the field of rare earth extraction and separation, the presence of tetravalent cerium will cause the dislocation of the rare earth extraction and separation order, so the conventional extraction and separation process will take measures to inhibit the conversion of rare earth trivalent cerium to tetravalent cerium. The present invention adopts effective technical measures to ensure the stable presence of an appropriate amount of tetravalent cerium in the chloride system, and utilizes the extremely easy extraction characteristics of the complex ligand of tetravalent cerium and fluoride ions, thereby ensuring that tetravalent cerium and fluorine can be preferentially coordinated and loaded into the organic phase, not only achieving the purpose of fluorine removal, but also realizing the separation of tetravalent cerium and other trivalent rare earths in the extraction section. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 This is an extraction separation flow chart provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The implementation principle of this application is: The present invention provides a pretreatment method for extracting and separating rare earths from a fluorine-containing rare earth chloride material liquid, that is, before the extraction and separation process of the rare earth chloride material liquid, the cerium element in the rare earth chloride solution is partially oxidized, and the property of fluorine and tetravalent cerium forming a complex that is easy to extract is utilized to achieve extraction and separation with trivalent rare earths, and then a reducing agent is used in the stripping section to reduce the tetravalent cerium to trivalent cerium, and the property that trivalent cerium is easy to be stripped under high acid and trivalent cerium and a small amount of fluorine are not precipitated is utilized to achieve co-stripping of trivalent cerium and fluorine, and the trivalent cerium and fluorine enter the stripping solution in a dissolved form.

[0024] In view of the fact that the rare earth chloride system has certain reducing properties, in order to ensure that the trivalent cerium is not reduced during the conversion process to tetravalent cerium during the extraction process, the present invention adopts the method of adding an oxidant to construct a continuous oxidizing environment, and at the same time ensures that the oxidized tetravalent cerium is co-extracted with fluorine into the organic phase through rapid mixing and clarification separation.

[0025] At the same time, in order to inhibit the reduction of tetravalent cerium after it enters the organic phase in the extraction section and the washing section, a diluent with a low bromine value is used to prepare the extractant.

[0026] The pretreatment method provided by the present invention for rare earth extraction and separation of fluorine-containing rare earth chloride material liquid comprises an extraction section, a washing section and a reduction stripping section, and the steps of each section are as follows: (1) Extraction section In the extraction section, the trivalent cerium in the fluorine-containing mixed rare earth chloride material liquid is oxidized to tetravalent cerium, and mixed with a blank organic phase to react to obtain a fluorine-free rare earth chloride material liquid and a loaded organic phase, wherein the loaded organic phase contains a fluorine-cerium coordination compound and a small amount of trivalent rare earth.

[0027] Since the rare earth chloride system is different from the rare earth sulfate system and has a certain degree of reducing property, the oxidation and extraction processes need to be carried out in one system during the oxidation process to ensure that the formed tetravalent cerium is complexed with fluorine in the aqueous phase and quickly extracted into the organic phase to avoid being reduced due to prolonged contact with the aqueous phase. The centrifugal extraction facility can achieve rapid contact and separation between the organic and aqueous phases, thereby ensuring that the tetravalent cerium can be stably coordinated with the fluoride ion and extracted into the organic phase.

[0028] Therefore, in certain implementations of the present invention, the process adopted in the extraction stage to oxidize trivalent cerium in the fluorine-containing mixed rare earth chloride liquid to tetravalent cerium is as follows: the fluorine-containing mixed rare earth chloride liquid is subjected to cerium oxidation at 30-60°C, and is rapidly contacted with a blank organic phase for extraction and separation during the oxidation process, and the contact time and separation time of the aqueous phase and the organic phase during the extraction process are both no more than 20 seconds, and the oxidation method includes at least one of electrolytic oxidation and oxidation with a water-soluble oxidizing agent, and the oxidizing agent with a water-soluble oxidizing agent is preferably potassium permanganate.

[0029] During the electrolytic oxidation process, trivalent cerium is oxidized to tetravalent cerium at the anode and reduced to trivalent cerium at the cathode. Therefore, diaphragm or ion membrane electrolysis can be used to ensure that the fluorine-containing rare earth chloride liquid is oxidized in the anode cell to obtain tetravalent cerium. The tetravalent cerium is coordinated with fluorine and directly extracted into the organic phase.

[0030] After the water-soluble oxidizing agent is added, the trivalent cerium in the fluorine-containing rare earth chloride liquid is oxidized to tetravalent cerium at the anode. The tetravalent cerium is coordinated with fluorine and directly extracted into the organic phase.

[0031] (2) Washing section The loaded organic phase obtained in the extraction section is washed with acid in the washing section, so that the trivalent rare earth in the organic phase returns to the extraction section, and the organic phase loaded with fluorine cerium coordination is obtained in the washing section. In certain implementations of the present invention, the washing acid in the washing section is at least one of hydrochloric acid, nitric acid and sulfuric acid, preferably hydrochloric acid, with an acidity of 0.2-0.7 mol / L.

[0032] (3) Stripping section The extraction and separation process is as follows: obtaining a defluorinated rare earth mixed solution at the front end of the extraction section; obtaining an organic phase containing a fluorinated cerium complex at the end of the washing section; and obtaining a fluorinated cerium aqueous phase and a blank organic phase in the stripping section. In certain implementations of the present invention, in the extraction and separation process, tetravalent cerium is oxidized in the extraction section.

[0033] The process steps adopted in the stripping section are as follows: adding a reducing agent and stripping acid in the stripping section, stripping the organic phase loaded with fluorine cerium coordination agent by reduction and acid addition, obtaining a stripping solution containing trivalent cerium and fluorine and a blank organic solution, and returning the blank organic solution to the extraction section for recycling. In certain implementations of the present invention, the stripping section F / tetravalent Ce molar ratio is 1-2; the stripping acid is at least one of hydrochloric acid, nitric acid and sulfuric acid, preferably hydrochloric acid, and the stripping acid acidity is 1.5-3 mol / L; the reducing agent is at least one of hydrogen peroxide, oxalic acid, thiourea and ascorbic acid.

[0034] Furthermore, the organic phase in the pretreatment method of the fluorine-containing rare earth chloride material liquid before rare earth extraction and separation is composed of at least one of the acidic extractants of P204, P507, and C272 and a diluent, and the diluent includes but is not limited to at least one of hydrogenated kerosene and white oil, and its bromine value is less than 10 mg.

[0035] The diluent has certain reducing properties. In order to avoid the tetravalent cerium entering the organic phase being reduced to trivalent in the extraction and washing sections, thereby destroying the coordination with fluoride ions and causing negative effects, it is preferred to use hydrogenated kerosene or white oil with low reducing properties.

[0036] The determination of the unsaturation degree of the diluent (bromine value) is the mass (expressed in milligrams) of the reaction between 100g of organic solvent and bromine under the test conditions, which can effectively reflect the content of reducing unsaturated hydrocarbon substances in kerosene.

[0037] The present application is further described in detail below in conjunction with the accompanying drawings and specific examples. The following examples are provided for a better understanding of the present invention, are not limited to the best implementation mode, and do not limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts falls within the protection scope of the present invention.

[0038] Specific experimental steps or conditions are not specified in the embodiments, and the operations or conditions of the conventional experimental steps described in the prior art in the art can be carried out. The reagents used and other instruments that do not specify the manufacturer are all conventional reagent products that can be obtained commercially. In addition, the accompanying drawings are only schematic diagrams of the embodiments of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted. Some block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities. Example 1

[0039] After acid dissolution and impurity removal, the southern ionic rare earth ore is subjected to fluorine-containing rare earth chloride liquid, in which the rare earth content is 250gREO / L, F / ΣREO is 0.5%wt, and the acidity is 0.1mol / L.

[0040] Rare earth distribution of southern ionic rare earth ores

[0041] The mixed rare earth chloride material liquid is pretreated for defluorination at a temperature of 35-40°C, including 3 extraction stages, 3 washing stages, and 5 stripping stages.

[0042] The extractant is: 1.5MP507, and white oil (bromine value is 6.8) is used as the diluent.

[0043] Extraction section:

[0044] A mixing tank is set at the front end of the extraction section feed stage to add 20% excess potassium permanganate to oxidize the rare earth chloride. After the trivalent cerium is converted to tetravalent cerium, it is directly pumped into the extraction section in a quantitative manner and extracted by centrifugal extraction. The mixing time of the organic phase and the feed liquid is 5S, and the separation time is 1S, so as to achieve the joint extraction of tetravalent cerium and fluorine.

[0045] The ratio of extraction section: organic: feed liquid = 1:1.2.

[0046] Washing section:

[0047] The centrifugal extraction method was adopted, the mixing time of the organic phase and the feed liquid was 5S, and the separation time was 1S.

[0048] Compared with: organic: washing acid = 10:1, Washing acid: 0.5mol / L nitric acid.

[0049] Stripping section

[0050] The operation was carried out in a mixing and settling tank, with a mixing time of 3 minutes and a settling time of 15 minutes; Compared with: organic: stripping acid: hydrogen peroxide = 10:2:0.1; Stripping acid: 2.5 mol / L hydrochloric acid; Reducing agent: 30% hydrogen peroxide.

[0051] The rare earth chloride solution obtained in the extraction section has a rare earth concentration of 215g / L after defluorination. The distribution changes as shown in the following table. The distribution of cerium is reduced to 0.004%, and the fluorine content is reduced to 0.032%. In the process of extracting and separating the rare earth chloride solution after defluorination using P507 to prepare single lanthanum, cerium and praseodymium-neodymium chloride and samarium-europium-gadolinium enrichment, the generation of three-phase products is reduced, and the frequency of tank cleaning is reduced by more than 90%.

[0052] Distribution of rare earth chloride after defluorination

[0053] The back extraction section obtains cerium fluoride-containing precipitation slurry and blank organic matter, and the blank organic matter is filtered and clarified and then returned to the extraction section for recycling. Example 2

[0054] Fluorine bastnaesite is oxidized and roasted-dissolved in hydrochloric acid, and then tempered, concentrated, and impurity-removed to obtain a fluorine-containing rare earth chloride liquid, in which the rare earth content is 150gREO / L, F / ΣREO is 0.7%wt, and the acidity is 0.05mol / L.

[0055] Distribution of rare earth elements in rare earth chloride solution with low cerium content

[0056] The pretreatment of the fluorine removal of the cerium-poor rare earth chloride material liquid is carried out in the range of 40-50°C, including 3 extraction stages, 3 washing stages and 4 stripping stages.

[0057] The extractant is: 1.5MP507, and hydrogenated kerosene (bromine value is 4) is the diluent.

[0058] Extraction section:

[0059] In the extraction section, an electrolytic reduction tank is used at the front end of the feed stage to directly oxidize the rare earth chloride. After the trivalent cerium is converted to tetravalent cerium, it is directly pumped into the extraction section in a quantitative manner and extracted by centrifugal extraction. The mixing time of the organic phase and the feed liquid is 15S, and the separation time is 10S, so as to realize the co-extraction of tetravalent cerium and fluorine. The ratio is: organic: feed liquid = 1:1.3. Washing section:

[0060] The centrifugal extraction method was adopted, the mixing time of the organic phase and the feed liquid was 15S, and the separation time was 10S.

[0061] Compared with: organic: washing acid = 10:1, Washing acid: 0.5mol / L hydrochloric acid Stripping section

[0062] The mixing and clarifying tank is used for operation, with a mixing time of 3 minutes and a clarifying time of 15 minutes. Relative ratio: organic: stripping solution = 10:2 Stripping solution: 3.0mol / L hydrochloric acid + thiourea The rare earth chloride solution after defluorination is obtained in the extraction section, with a rare earth concentration of 135g / L. The distribution changes as shown in the following table, and the fluorine content is reduced to 0.05%. The rare earth chloride solution after defluorination is extracted and separated by P507 to prepare single lanthanum, cerium and praseodymium-neodymium chloride and samarium-europium-gadolinium enrichment process. The production of three-phase products is reduced, and the frequency of tank cleaning is reduced by more than 80%.

[0063] Distribution of rare earth elements in cerium-deficient rare earth chloride solution after defluorination

[0064] The back extraction section obtains cerium fluoride-containing precipitation slurry and blank organic matter, and the blank organic matter is filtered and clarified and then returned to the extraction section for recycling.

[0065] Comparative Example 1

[0066] After acid dissolution and impurity removal, the southern ionic rare earth ore is subjected to fluorine-containing rare earth chloride liquid, in which the rare earth content is 250gREO / L, F / ΣREO is 0.5%wt, and the acidity is 0.1mol / L.

[0067] Rare earth distribution of southern ionic rare earth ores

[0068] The mixed rare earth chloride material liquid is pretreated for defluorination at a temperature of 35-40°C, including 3 extraction stages, 3 washing stages, and 5 stripping stages.

[0069] The extractant is: 1.5MP507, and white oil (bromine value is 6.8) is used as the diluent. Extraction section:

[0070] A mixing tank is set at the front end of the extraction section feed stage to add 20% excess potassium permanganate to oxidize the rare earth chloride. After the trivalent cerium is converted to tetravalent cerium, it is directly pumped into the extraction section in a quantitative manner and extracted by centrifugal extraction. The mixing time of the organic phase and the feed liquid is 2 minutes, and the separation time is 4 minutes, so as to achieve the joint extraction of tetravalent cerium and fluorine.

[0071] The ratio of extraction section: organic: feed liquid = 1:1.2.

[0072] Washing section:

[0073] The extraction method was extracted by an extraction tank, with a mixing time of 2 minutes for the organic phase and the feed liquid and a separation time of 4 minutes.

[0074] Compared with: organic: washing acid = 10:1, Washing acid: 0.5mol / L hydrochloric acid

[0075] Stripping section

[0076] The operation was carried out in a mixing and settling tank, with a mixing time of 3 minutes and a settling time of 15 minutes; Compared with: organic: stripping acid: hydrogen peroxide = 10:2:0.1; Stripping acid: 2.5 mol / L hydrochloric acid; Reducing agent: 30% hydrogen peroxide.

[0077] The rare earth chloride solution obtained in the extraction section has a rare earth concentration of 213g / L after defluorination. The distribution changes as shown in the following table. The distribution of cerium is reduced to 1.2%, and the fluorine content is reduced to 0.12%. In the process of extracting and separating the rare earth chloride solution after defluorination using P507 to prepare single lanthanum, cerium and praseodymium-neodymium chloride and samarium-europium-gadolinium enrichment, the generation of three-phase products is reduced, and the frequency of tank cleaning is reduced by more than 60%.

[0078] Distribution of rare earth chloride after defluorination

[0079] The back extraction section obtains cerium fluoride-containing precipitation slurry and blank organic matter, and the blank organic matter is filtered and clarified and then returned to the extraction section for recycling.

Claims

1. A pretreatment method for defluorination of fluorine-containing mixed rare earth chloride liquid, characterized in that: It includes extraction section, washing section and reduction stripping section. The steps of each section are as follows: Extraction section: In the extraction section, the trivalent cerium in the fluorine-containing mixed rare earth chloride material liquid is oxidized to tetravalent cerium, and mixed with a blank organic phase to react to obtain a defluorinated rare earth chloride material liquid and a loaded organic phase, wherein the loaded organic phase contains a fluorine-cerium coordination compound and a small amount of trivalent rare earth; Washing section: In the washing section, the loaded organic phase obtained in the extraction section is washed with acid, so that the trivalent rare earth in the organic phase returns to the extraction section, and the organic phase loaded with fluorine cerium coordination is obtained in the washing section; Stripping section: Reducing agent and stripping acid are added in the stripping section, and the organic phase loaded with fluorine cerium coordination compound is stripped by reduction and acid addition to obtain stripping solution containing trivalent cerium and fluorine and blank organic solution, which is returned to the extraction section for recycling.

2. The method according to claim 1, characterized in that The extraction section comprises the following process steps: The fluorine-containing mixed rare earth chloride material liquid is subjected to cerium oxidation at 30-60°C, and is rapidly contacted with a blank organic phase for extraction and separation during the oxidation process. During the extraction process, the contact time and separation time of the aqueous phase and the organic phase are both no more than 20 seconds.

3. The method according to claim 1, characterized in that: In the extraction stage, oxidation includes at least one of electrolytic oxidation and oxidation with the addition of a water-soluble oxidizing agent.

4. The method according to claim 3, characterized in that The water-soluble oxidizing agent is added for oxidation, and the water-soluble oxidizing agent is potassium permanganate.

5. The method according to claim 1, characterized in that The rare earth content of the fluorine-containing rare earth chloride liquid is 50-300 gREO / L, F / ΣREO is 0.1-1.0%wt, and the acidity is 0.01-0.2 mol / L.

6. The method according to claim 1, characterized in that The washing acid in the washing section is at least one of hydrochloric acid, nitric acid and sulfuric acid.

7. The method according to claim 6, characterized in that The washing acid in the washing section is hydrochloric acid with an acidity of 0.2-0.7 mol / L.

8. The method according to claim 1, characterized in that The stripping acid in the stripping section is at least one of hydrochloric acid, nitric acid and sulfuric acid.

9. The method according to claim 8, characterized in that The stripping acid in the stripping section is hydrochloric acid with an acidity of 1.5-3 mol / L.

10. The method according to claim 1, characterized in that In the extraction section, the molar ratio of F / tetravalent Ce is 1-2.

11. The method according to claim 1, characterized in that: The reducing agent of the stripping section is at least one of hydrogen peroxide, oxalic acid, thiourea and ascorbic acid.

12. The method according to claim 1, characterized in that The organic phase is composed of at least one of the acidic extractants of P204, P507, and C272 and a diluent, and the diluent includes but is not limited to at least one of hydrogenated kerosene and white oil, and its bromine value is less than 10 mg.

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