Method for extracting cerium, fluorine and phosphorus in rare earth mixed ore through co-extraction method

Abstract

The invention relates to the field of resource recovery, in particular to a method for extracting cerium, fluorine and phosphorus in rare earth mixed ore through a co-extraction method. According to the method disclosed by the invention, the separation and effective recovery of light rare earth cerium, fluorine and phosphorus can be realized by synergistically co-extracting the mixed ore leachate through two extractants Cyanex923 and N1923 and matching with a specific step-by-step reverse extraction step; the extraction system used in the method is good in phase separation, stable in process, free of sediment residues, high in rare earth and resource recovery rate and good in commercial value of recovered products, the separated thorium and trivalent rare earth raffinate can be directly connected with an existing follow-up treatment process flow, and extra technology and process changes are not needed.

Description

Technical Field

[0001] The present invention relates to the field of resource recovery, and particularly to a method for co-extracting cerium fluorophosphate from rare earth mixed ores by co-extraction method. Background Art

[0002] The bastnasite-monazite mixed rare earth ore occurring in Baotou area of Inner Mongolia is a strategic resource base for China's light rare earth industry, and the cerium element accounts for 45%-55% of the total rare earth. However, in recent years, the development of global cerium products has shown an over-concentrated trend. In 2022, the proportion of cerium-based products in the global rare earth oxide production reached 30%-40%, but the market price has been continuously low. According to the statistics of the China Rare Earth Industry Association, the price of cerium oxide has dropped from the peak of 320,000 yuan / ton in 2011 to less than 15,000 yuan / ton in 2023, resulting in an average annual growth of 18% in the domestic cerium product inventory in the past five years, seriously restricting the sustainable development of the industry. More severely, this type of ore contains 6%-8% fluorine and 6%-7% phosphorus associated resources. In the current "concentrated sulfuric acid roasting and leaching" process, every 1 ton of rare earth oxide produced will generate 12-15 tons of fluorine-containing phosphoric acid wastewater, causing environmental risks such as excessive fluoride in water bodies and soil hardening. At the same time, the comprehensive utilization rate of fluorine and phosphorus resources in the ore is less than 20%. This double dilemma of "high environmental governance cost and serious resource waste" urgently requires the development of new clean metallurgy technologies to achieve the co-extraction and high-value utilization of cerium, fluorine, and phosphorus, and to build an environment-friendly comprehensive utilization system for rare earth resources.

[0003] Most of the existing technologies leach the mixed ore with sulfuric acid, and mainly recover cerium after extraction by an extractant. The associated resources are rarely recovered in the early technologies, or are back-extracted and recovered in the form of cerium fluoride or cerium phosphate, and the value of the products is limited. For example, in Patent CN1439730A (a process for extracting and separating cerium from rare earth solution containing fluorosulfuric acid), the main steps include: leaching the mixed ore with sulfuric acid leaching solution, and filtering to obtain a fluorosulfuric acid leaching solution; using this leaching solution as the feed liquid, and using an organic phase composed of P507-alkane or xylene to extract tetravalent cerium, thorium, iron and trivalent rare earths; washing the organic phase with a back-extracting agent to obtain a back-extracting solution containing cerium hydroxide and preparing a cerium dioxide product. In Patent CN105132682B (a method for extracting and separating cerium, fluorine and phosphorus from sulfuric acid leaching solution of Baotou rare earth ore), the main steps include: oxidizing and roasting - sulfuric acid leaching of the Baotou rare earth mixed ore to obtain a rare earth sulfate solution containing fluorine, tetravalent cerium and phosphorus; adjusting the acidity and then extracting the feed liquid with an extractant at room temperature to obtain a raffinate and a loaded organic phase; at room temperature, the loaded organic phase containing cerium (IV), fluorine and phosphorus is back-extracted with a back-extracting solution to obtain a back-extracting mixture containing Ce 3+ 、CeF3 and CePO4, filtering to obtain a CeF3 and CePO4 mixed fine powder, and a Ce 3+ solution; the obtained Ce 3+After adjusting the pH of the solution to 1-2 with ammonia water, oxalic acid is added to precipitate cerium(III). After washing the precipitate, it is calcined at 800 °C to obtain the product CeO2. Patent CN115259204A (a clean metallurgical process for synchronous recovery of cerium and fluorine from bastnasite) mainly includes the following steps: roasting Sichuan bastnasite by oxidative roasting and leaching with boric acid-containing sulfuric acid to obtain a leaching solution containing cerium, boron, and fluorine, and using the extractant Cyanex923 to extract the feed solution; 3+ back-extracting the obtained cerium, boron, and fluorine-loaded organic phase with hydrogen peroxide and sulfuric acid to obtain a back-extracted solution containing Ce 4- ; back-extracting the organic phase treated in the previous step with ammonia water to obtain a back-extracted solution containing BF

[0004] ; adding alkali or oxalic acid to the cerium-containing back-extracted solution to obtain cerium hydroxide or cerium oxalate respectively, and roasting to obtain cerium oxide products. Adding potassium solution to the back-extracted solution containing borate radicals to obtain a precipitate to obtain potassium tetrafluoroborate products. Summary of the Invention

[0005] In view of this, the present invention provides a method for co-extracting cerium, fluorine, and phosphorus from rare earth mixed ores by co-extraction. The method of the present invention can realize the separation and effective recovery of light rare earth cerium, fluorine, and phosphorus, and obtain high-value products.

[0006] The present invention provides a method for co-extracting cerium, fluorine, and phosphorus from rare earth mixed ores by co-extraction, including the following steps:

[0007] (A) Preparation of extraction solvent:

[0008] Mix the extractant N1923, the extractant Cyanex923, and the diluent to obtain an extraction solvent;

[0009] (B) Preparation of feed solution:

[0010] Oxidatively roast the mixed rare earth ore, and then leach it with an acid solution to obtain a leaching solution;

[0011] (C) Co-extraction:

[0012] Use the extraction solvent obtained in step (A) to extract the leaching solution obtained in step (B) to obtain a loaded organic phase and a raffinate respectively;

[0013] (D) Stripping of phosphorus:

[0014] Use stripping agent 1 to strip the loaded organic phase to obtain stripping organic phase 1 and stripping solution 1 respectively;

[0015] Among them, the stripping agent 1 is a sulfuric acid solution;

[0016] (E) Stripping of cerium:

[0017] Use stripping agent 2 to strip the stripping organic phase 1 to obtain stripping organic phase 2 and stripping solution 2 respectively;

[0018] Among them, the stripping agent 2 is a mixed solution of sulfuric acid and hydrogen peroxide;

[0019] (F) Stripping of boron and fluorine:

[0020] Use stripping agent 3 to strip the stripping organic phase 2 to obtain blank organic phase 3 and stripping solution 3 respectively;

[0021] Among them, the stripping agent 3 is ammonia water;

[0022] (G) Preparation of products:

[0023] Remove impurities from the stripping solution 1 to obtain phosphoric acid;

[0024] Mix the stripping solution 2 with a precipitant to precipitate cerium hydroxide or cerium oxalate, and then calcine to obtain cerium oxide;

[0025] Mix the stripping solution 3 with a potassium salt, adjust the pH value, perform solid-liquid separation and drying to obtain potassium tetrafluoroborate;

[0026] In the above steps, for the steps without sequential correlation, their order has no special limitation.

[0027] Preferably, in step (A), the concentration of extractant N1923 in the extraction solvent is 5 vol% to 15 vol%, and the concentration of extractant Cyanex923 is 10 vol% to 30 vol%.

[0028] Preferably, in step (A), the diluent is at least one of sulfonated kerosene, n-hexane, and n-heptane.

[0029] Preferably, in step (B):

[0030] The temperature of the oxidative roasting is 300 to 700 °C, and the time is 1 to 4 h;

[0031] The acid solution is a mixed acid solution of sulfuric acid and boric acid;

[0032] The concentration of the sulfuric acid is 2 to 3 M;

[0033] The dosage of the boric acid is controlled as follows: the molar ratio of B in the boric acid to F in the mixed rare earth ore is 0.2 to 0.5;

[0034] The liquid-solid ratio of the leaching is 3 to 5.

[0035] Preferably, in step (B), the temperature of the leaching is 60 to 95 °C, and the time is 10 to 90 min.

[0036] 6. The method according to claim 1, wherein in step (C), the ratio of the extraction solvent obtained in step (A) to the leaching solution obtained in step (B) is (0.5 to 2):1.

[0037] Preferably, in step (D):

[0038] The concentration of the sulfuric acid solution is 0.5 to 2 mol / L;

[0039] The ratio of the loaded organic phase to the stripping agent 1 is (0.5 to 2):1.

[0040] Preferably, in step (E):

[0041] The volume concentration of hydrogen peroxide in the mixed solution is 0.5 vol% to 2 vol%, and the concentration of H2SO4 is 0.5 to 2 mol / L;

[0042] The ratio of the stripped organic phase 1 to the stripping agent 2 is (0.5 to 2):1.

[0043] Preferably, in step (F):

[0044] The concentration of the ammonia water is 0.5 to 1 mol / L;

[0045] The ratio of the stripped organic phase 2 to the stripping agent 3 is (0.5 to 2):1.

[0046] Preferably, in step (G):

[0047] The process of impurity removal includes: mixing the stripped solution 1 with an impurity removal agent, then performing solid-liquid separation to obtain a phosphorus-containing solution and gypsum respectively; then, recovering phosphorus in the phosphorus-containing solution to obtain phosphoric acid;

[0048] The impurity removal agent is at least one of calcium carbonate, calcium hydrogen phosphate, calcium dihydrogen phosphate, and calcium hydroxide;

[0049] The precipitant is at least one of sodium hydroxide, sodium oxalate, and oxalic acid;

[0050] The potassium salt is at least one of potassium chloride, potassium nitrate, and potassium sulfate;

[0051] Adjusting the pH value is to adjust it to 1 - 3.

[0052] Aiming at the problems of low recovery rate of fluorophosphorus associated resources in light rare earth mixed ores and limited industrial value of the recovered product forms in the prior art, the present invention provides a method for co - extracting cerium, fluorine, and phosphorus from rare earth mixed ores by a co - extraction method, which is a clean metallurgical process for synergistically extracting the leaching solution of mixed rare earth ores and step - by - step recovering cerium, fluorine, and phosphorus. By synergistically co - extracting the leaching solution of mixed ores with two extractants, Cyanex923 + N1923, and matching specific step - by - step stripping steps, the separation and effective recovery of light rare earth cerium, fluorine, and phosphorus can be achieved; the extraction system used in the method of the present invention has good phase separation, stable process, no precipitation residue generation, high recovery rate of rare earth and resources, good commercial value of the recovered product, and the separated thorium and trivalent rare earth raffinate can be directly connected to the existing subsequent treatment process without additional technical and process changes.

[0053] The key points in the present invention include:

[0054] (1) The present invention uses a neutral phosphine extractant Cyanex923 and a primary amine extractant N1923 to synergistically extract cerium, fluorine, and phosphorus from the leaching solution of light rare earth mixed ores in Inner Mongolia Baotou. Among them, the introduction of N1923 raises the separation coefficients of cerium from thorium and cerium from other trivalent rare earths, enabling the effective separation of cerium, fluorine, and phosphorus from trivalent rare earths and thorium and other elements through co - extraction operations. Based on the different coordination mechanisms of N1923 with cerium and phosphorus and the difference in the stability of the formed complexes, phosphorus is easily stripped while cerium can be retained in the organic phase and is not recovered together in the form of cerium phosphate. Based on this principle and using different stripping steps, cerium, fluorine, and phosphorus are separated, stripped, and recovered step - by - step with excellent separation effect.

[0055] (2) The present invention uses a neutral phosphine extractant Cyanex923 and a primary amine extractant N1923 for synergistic extraction, which has good selectivity for cerium, fluorine, and phosphorus. Through co - extraction - step - by - step stripping recovery, more than 99% of cerium, fluorine, and phosphorus can be recovered, and the products are exported in the forms of cerium oxide, potassium fluoroborate, and phosphoric acid respectively. It hardly affects the remaining trivalent rare earths and thorium and other elements that enter the subsequent process in the form of raffinate. This shows that the method has a high extraction recovery rate for target elements and less loss of rare earths. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on the provided drawings.

[0057] Figure 1 It is a flow chart of the method for co-extracting cerium fluorophosphate from rare earth mixed ore by the co-extraction method of the present invention;

[0058] Figure 2 It is an SEM image of the cerium oxide product obtained in Example 1 of the present invention, wherein, Figure 2 (A) and Figure 2 (B) are SEM images at different magnification ratios;

[0059] Figure 3 It is an SEM image of the potassium tetrafluoroborate product obtained in Example 1 of the present invention, wherein, Figure 3 (A) and Figure 3 (B) are SEM images at different magnification ratios. Detailed implementation manners

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0061] In this article, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, and also includes an open technical solution containing the listed features.

[0062] The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0063] In this article, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to an integer, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0064] In this article, for units related to data ranges, if the unit is only attached to the right endpoint, it means that the units of the left and right endpoints are the same. For example, 1.5 to 2.0 mol / L indicates that the units of both the left endpoint "1.5" and the right endpoint "2.0" are mol / L.

[0065] The present invention provides a method for co-extracting cerium fluorophosphate from a rare earth mixed ore, comprising the following steps:

[0066] (A) Preparation of an extraction solvent:

[0067] Mix an extractant N1923, an extractant Cyanex923, and a diluent to obtain an extraction solvent;

[0068] (B) Preparation of a feed solution:

[0069] Oxidatively roast the mixed rare earth ore, and then leach it with an acid solution to obtain a leachate;

[0070] (C) Co-extraction:

[0071] Use the extraction solvent obtained in step (A) to extract the leachate obtained in step (B) to obtain a loaded organic phase and a raffinate respectively;

[0072] (D) Stripping of phosphorus:

[0073] Use a stripping agent 1 to strip the loaded organic phase to obtain a stripped organic phase 1 and a stripping solution 1 respectively;

[0074] Among them, the stripping agent 1 is a sulfuric acid solution;

[0075] (E) Stripping of cerium:

[0076] Use a stripping agent 2 to strip the stripped organic phase 1 to obtain a stripped organic phase 2 and a stripping solution 2 respectively;

[0077] Among them, the stripping agent 2 is a mixed solution of sulfuric acid and hydrogen peroxide;

[0078] (F) Stripping of boron fluoride:

[0079] Use a stripping agent 3 to strip the stripped organic phase 2 to obtain a blank organic phase 3 and a stripping solution 3 respectively;

[0080] Among them, the stripping agent 3 is ammonia water;

[0081] (G) Preparation of products:

[0082] Remove impurities from the stripping solution 1 to obtain phosphoric acid;

[0083] Mix the stripping solution 2 with a precipitating agent to precipitate cerium hydroxide or cerium oxalate, and then roast to obtain cerium oxide;

[0084] Mix the stripping solution 3 with a potassium salt, adjust the pH value, perform solid-liquid separation and drying to obtain potassium tetrafluoroborate;

[0085] In the above steps, for steps without a sequential relationship, there is no special limitation on their order.

[0086] In the present invention, in the above steps, steps with a sequential relationship are carried out in the sequential order, and for steps without a sequential relationship, there is no special limitation on their order. The "steps without a sequential relationship" refer to steps without an inevitable sequential relationship. For example, for step (A) and step (C), step (C) uses the extraction solvent obtained in step (A), so it is necessary to perform step (A) first and then step (C), that is, there is a sequential relationship between them, and in this case, they need to be carried out in the sequential order. Another example is step (A) and step (B), etc., which have no sequential relationship, so there is no special limitation on their order; the same applies to other steps and will not be exemplified one by one.

[0087] In the present invention, the numbers in each step (such as the numbers 1, 2, 3, etc. after the organic phase, the numbers 1, 2, 3, etc. after the stripping agent, the numbers 1, 2, 3, etc. after the stripping solution) do not have any special limitation on the substances themselves and are only used as labels for the convenience of corresponding to each step intuitively.

[0088] See Figure 1 , Figure 1 which is a flow chart of the method for co-extracting cerium fluorophosphate from rare earth mixed ores by the co-extraction method of the present invention.

[0089] Regarding step (A) :

[0090] (A) Prepare an extraction solvent: Mix an extractant N1923, an extractant Cyanex923 and a diluent to obtain an extraction solvent.

[0091] In the present invention, there is no special limitation on the sources of the extractant N1923 (secondary carbon primary amine) and the extractant Cyanex923, and they can be commercially available products or prepared according to known preparation methods in the art.

[0092] In the present invention, the diluent is preferably at least one of sulfonated kerosene, n-hexane, and n-heptane.

[0093] In the present invention, the concentration of the extractant N1923 in the extraction solvent is preferably 5 vol% to 15 vol%, specifically it can be 5 vol%, 6 vol%, 7 vol%, 8 vol%, 9 vol%, 10 vol%, 11 vol%, 12 vol%, 13 vol%, 14 vol%, 15 vol%. In the present invention, the concentration of the extractant Cyanex923 in the extraction solvent is preferably 10 vol% to 30 vol%, specifically it can be 10 vol%, 11 vol%, 12 vol%, 13 vol%, 14 vol%, 15 vol%, 16 vol%, 17 vol%, 18 vol%, 19 vol%, 20 vol%, 21 vol%, 22 vol%, 23 vol%, 24 vol%, 25 vol%, 26 vol%, 27 vol%, 28 vol%, 29 vol%, 30 vol%.

[0094] Regarding step (B) :

[0095] (B) Preparation of the raw material solution: The mixed rare earth ore is subjected to oxidative roasting, and then leached with an acid solution to obtain a leachate.

[0096] In the present invention, the mixed rare earth ore is preferably bastnasite; bastnasite is a cerium fluorocarbonate mineral and is often associated with some rare earth element-containing minerals. The process of the present invention is not only suitable for ordinary bastnasite, but also suitable for bastnasite mixed rare earth ore. A typical bastnasite is a monazite mixed rare earth ore unique to the Baotou area in Inner Mongolia. The phosphorus content of the bastnasite in Sichuan is extremely low, while the bastnasite mixed rare earth ore in Baotou, Inner Mongolia has a higher phosphorus content and a more complex composition, making extraction and recovery more difficult; while the present invention can be used to treat the above ores to effectively separate and recover cerium, fluorine, and phosphorus and obtain high-value products.

[0097] In the present invention, the temperature of the oxidative roasting is preferably 300 to 700 °C, specifically it can be 300 °C, 350 °C, 400 °C, 450 °C, 500 °C, 550 °C, 600 °C, 650 °C, 700 °C, and more preferably 500 °C. The time of the oxidative roasting is preferably 1 to 4 h, specifically it can be 1 h, 2 h, 3 h, 4 h, and more preferably 2 h.

[0098] In the present invention, after the above-mentioned oxidative roasting, acid leaching is carried out. In the present invention, the acid solution is preferably a mixed acid solution of sulfuric acid and boric acid. In the present invention, the concentration of the sulfuric acid used is controlled according to the content of the mixed rare earth ore, and the residual acid after leaching (i.e., the unconsumed H2SO4 remaining in the system after leaching) should be 1.5 - 2.0 mol / L. Preferably, the concentration of the sulfuric acid used is 2 - 3 M, specifically 2 M, 2.5 M, 3 M. In the present invention, the dosage of the boric acid is controlled according to the F content in the mixed rare earth ore, and the molar ratio of B to F in the mixed rare earth ore is preferably 0.2 - 0.5, specifically 0.2, 0.3, 0.4, 0.5. In the present invention, the liquid-solid ratio L / S of the leaching is preferably 3 - 5 (unit: L / kg or mL / g), specifically 3, 4, 5. In the present invention, the process of determining the material dosage is as follows: First, weigh a certain amount of ore sample, and then the dosage of the sulfuric acid to be weighed can be determined according to the value of the leaching liquid-solid ratio L / S (for example, if L / S = 3 and the mass of the ore sample taken is 10 kg, then the dosage of the sulfuric acid required can be calculated as 30 L), and weigh out the sulfuric acid. Then, determine the amount of boric acid required according to the B / F molar ratio, and weigh out the boric acid. Mix the weighed sulfuric acid and boric acid to prepare a mixed acid solution, and then add the weighed ore sample for acid leaching.

[0099] In the present invention, the temperature of the leaching is preferably 60 - 95 °C, specifically 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, and more preferably 85 °C. The time of the leaching is preferably 10 - 90 min, specifically 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, 90 min. In the present invention, after leaching, the obtained leaching solution is used as the raw material solution for the subsequent extraction process.

[0100] Regarding step (C) :

[0101] (C) Co-extraction: Using the extraction solvent obtained in step (A) to extract the leaching solution obtained in step (B), a loaded organic phase and a raffinate are obtained respectively.

[0102] In the present invention, the extraction process preferably includes: mixing the extraction solvent obtained in step (A) with the leaching solution obtained in step (B), shaking and then standing for phase separation to obtain a loaded organic phase and a raffinate respectively. Among them, the ratio of the extraction solvent obtained in step (A) to the leaching solution obtained in step (B) (O / A ratio) is preferably (0.5 - 2):1, specifically 0.5:1, 1:1, 1.5:1, 2:1. The shaking rate is preferably 200 - 300 rpm, specifically 200 rpm, 250 rpm, 260 rpm, 300 rpm; the shaking time is preferably 10 - 30 min, specifically 10 min, 15 min, 20 min, 25 min, 30 min. The standing time is preferably 1 - 10 min, specifically 1 min, 5 min, 10 min. After standing, phase separation is carried out to obtain a loaded organic phase 1 and a raffinate respectively.

[0103] Through the above co-extraction, the present invention extracts cerium, phosphorus, boron, and fluorine into the organic phase, while trivalent rare earths (such as La, Pr, Nd) and thorium are retained in the raffinate, obtaining an organic phase loaded with Ce(IV)+P+B+F and a raffinate retaining trivalent rare earths and thorium respectively, thereby separating cerium, phosphorus, boron - fluorine from trivalent rare earths and thorium.

[0104] Regarding step (D) :

[0105] (D) Stripping phosphorus: Using stripping agent 1 to strip the loaded organic phase to obtain a stripped organic phase 1 and a stripping solution 1 respectively.

[0106] In the present invention, the stripping agent 1 is a sulfuric acid solution. In the present invention, the concentration of the sulfuric acid solution is preferably 0.5 - 2 mol / L, specifically 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L.

[0107] In the present invention, the stripping process preferably includes: mixing the stripping agent 1 with the loaded organic phase, shaking and then standing for phase separation to obtain a stripped organic phase 1 and a stripping solution 1 respectively. Among them, the ratio of the loaded organic phase to the stripping agent 1 (O / A ratio) is preferably (0.5 - 2):1, specifically 0.5:1, 1:1, 1.5:1, 2:1. The shaking rate is preferably 200 - 300 rpm, specifically 200 rpm, 250 rpm, 260 rpm, 300 rpm; the shaking time is preferably 10 - 30 min, specifically 10 min, 15 min, 20 min, 25 min, 30 min. The standing time is preferably 1 - 10 min, specifically 1 min, 5 min, 10 min. After standing, phase separation is carried out to obtain a stripped organic phase 1 and a stripping solution 1 respectively.

[0108] Through the above stripping, phosphorus in the loaded organic phase is stripped off, and the loaded organic phase 1 containing Ce(IV)+B+F and the stripping solution 1 containing sulfuric and phosphoric mixed acid are obtained respectively.

[0109] Regarding step (E) :

[0110] (E) Stripping cerium: Using strippant 2 to strip the stripped organic phase 1, and the stripped organic phase 2 and the stripping solution 2 are obtained respectively.

[0111] In the present invention, the strippant 2 is a mixed solution of hydrogen peroxide and sulfuric acid. In the present invention, the volume concentration of hydrogen peroxide in the mixed solution is preferably 0.5 vol% - 2 vol%, specifically 0.5 vol%, 1 vol%, 1.5 vol%, 2 vol%. The concentration of H2SO4 in the mixed solution is preferably 0.5 - 2 mol / L, specifically 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L.

[0112] In the present invention, the stripping process preferably includes: mixing the strippant 2 with the stripped organic phase 1, oscillating and then standing for phase separation to obtain the stripped organic phase 2 and the stripping solution 2 respectively. Among them, the phase ratio (O / A ratio) of the stripped organic phase 1 to the strippant 2 is preferably (0.5 - 2):1, specifically 0.5:1, 1:1, 1.5:1, 2:1. The oscillation rate is preferably 200 - 300 rpm, specifically 200 rpm, 250 rpm, 260 rpm, 300 rpm; the oscillation time is preferably 10 - 30 min, specifically 10 min, 15 min, 20 min, 25 min, 30 min. The standing time is preferably 1 - 10 min, specifically 1 min, 5 min, 10 min. After standing, phase separation is carried out to obtain the stripped organic phase 2 and the stripping solution 2 respectively.

[0113] Through the above stripping, cerium in the stripped organic phase 1 is extracted, and the loaded organic phase 2 containing B+F and the stripping solution 2 containing Ce(IV) are obtained respectively.

[0114] Regarding step (F) :

[0115] (F) Stripping boron and fluorine: Using strippant 3 to strip the stripped organic phase 2, and the blank organic phase 3 and the stripping solution 3 are obtained respectively.

[0116] In the present invention, the strippant 3 is preferably ammonia water. The concentration of the ammonia water is preferably 0.5 - 1 mol / L, specifically 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L.

[0117] In the present invention, the stripping process preferably includes: mixing the stripping agent 3 with the stripping organic phase 2, shaking and then standing for phase separation to obtain a blank organic phase 3 and a stripping solution 3 respectively. Among them, the ratio of the stripping organic phase 2 to the stripping agent 3 (O / A ratio) is preferably (0.5 - 2):1, specifically 0.5:1, 1:1, 1.5:1, 2:1. The shaking rate is preferably 200 - 300 rpm, specifically 200 rpm, 250 rpm, 260 rpm, 300 rpm; the shaking time is preferably 10 - 30 min, specifically 10 min, 15 min, 20 min, 25 min, 30 min. The standing time is preferably 1 - 10 min, specifically 1 min, 5 min, 10 min. After standing, phase separation is carried out to obtain a blank organic phase 3 and a stripping solution 3 respectively.

[0118] Through the above stripping in the present invention, stripping solutions 3 and blank organic phases 3 containing tetrafluoroborate (BF4 - ) are obtained respectively.

[0119] Regarding step (G) :

[0120] In the present invention, step (G) is to process the stripping solutions obtained in the previous steps to prepare various products respectively.

[0121] Step (G) includes: removing impurities from the stripping solution 1 to obtain phosphoric acid.

[0122] In the present invention, the stripping solution 1 is a sulfuric-phosphoric mixed acid solution, and the process of removing impurities therefrom preferably includes: mixing the stripping solution 1 with an impurity removing agent, and then performing solid-liquid separation to obtain a phosphorus-containing solution and gypsum respectively; then, recovering phosphorus in the phosphorus-containing solution to obtain phosphoric acid. Among them, the impurity removing agent is a calcium-containing substance, preferably at least one of calcium carbonate, calcium hydroxide, calcium hydrogen phosphate, and calcium dihydrogen phosphate. The dosage of the impurity removing agent can be added according to the sulfuric acid content in the stripping solution 1. After adding the above impurity removing agent, it reacts with sulfuric acid in the stripping solution 1 to form gypsum precipitate, and then through solid-liquid separation, gypsum and a phosphorus-containing solution are obtained respectively. Among them, the way of solid-liquid separation is not particularly limited and can be a conventional separation method in the art. After obtaining the phosphorus-containing solution through the above solid-liquid separation, phosphorus in it is recovered. The recovery method preferably includes: methods such as heating evaporation and rectification, or extraction and stripping to improve the purity. After the above recovery treatment, phosphoric acid with the specified required concentration is obtained.

[0123] Step (G) further includes: mixing the stripping solution 2 with a precipitating agent to precipitate cerium hydroxide or cerium oxalate, and then roasting to obtain cerium oxide.

[0124] In the present invention, the precipitant is preferably at least one of sodium hydroxide, sodium oxalate, and oxalic acid. By adding the above-mentioned precipitant, cerium hydroxide or cerium oxalate precipitate is formed in the system, and then solid-liquid separation is carried out to obtain a crude cerium product. After obtaining the crude cerium product, roasting is carried out to obtain cerium oxide (CeO2). The temperature of the roasting is preferably 600-900 °C, specifically 600 °C, 650 °C, 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, and more preferably 800 °C; the time of the roasting is preferably 1-4 h, specifically 1 h, 2 h, 3 h, 4 h.

[0125] Step (G) further includes: mixing the stripping solution 3 with a potassium salt, adjusting the pH value, performing solid-liquid separation and drying to obtain potassium tetrafluoroborate.

[0126] In the present invention, the potassium salt is preferably at least one of potassium chloride, potassium nitrate, and potassium sulfate. The dosage of the potassium salt is preferably: the molar ratio of K in the potassium salt to B in the stripping solution 3 is 0.8-4, specifically 0.8, 1, 2, 3, 4. After mixing the stripping solution 3 with the potassium salt, the pH value is adjusted, preferably adjusted to 1-3, specifically 1, 2, 3. After the above treatment, potassium tetrafluoroborate precipitate is formed in the system, and solid-liquid separation is carried out to separate the precipitate to obtain a solid. Then, drying is carried out to obtain potassium tetrafluoroborate.

[0127] The method for co-extracting cerium fluorophosphate from rare earth mixed ores provided by the present invention is a clean metallurgical process for synergistically extracting and treating the leaching solution of mixed rare earth ores and stepwise recovering cerium fluorophosphate. It can realize the separation and effective recovery of light rare earth cerium, fluorine, and phosphorus through the synergistic co-extraction of two extractants for the leaching solution of mixed ores and the specific stepwise stripping steps; the extraction system used in the method of the present invention has good phase separation, stable process, no precipitation slag generation, high recovery rate of rare earth and resources, good commercial value of the recovered products, and the separated thorium and trivalent rare earth raffinate can be directly connected to the existing subsequent treatment process without additional technology and process changes.

[0128] Compared with the prior art, the present invention has the following beneficial effects:

[0129] 1. The present invention separates and recovers cerium fluorophosphate from the leaching solution of light rare earth by liquid-liquid extraction method, and uses the complexation mechanism of cerium, phosphorus with boron fluoride to reduce the generation of traditional rare earth fluoride slag or rare earth phosphate slag, and there will be no precipitation entrainment during the separation process.

[0130] 2. The present invention uses two extractants, N1923 extractant and Cyanex923, for synergistic extraction after mixing. Compared with the extraction effect of pure Cyanex923 on cerium and phosphorus, it is more stable, has obvious extraction capacity advantages, and N1923, as a traditional industrial extractant, has a lower cost, reducing the production cost of using pure Cyanex923 for extraction.

[0131] 3. The present invention realizes the comprehensive recovery of cerium, the main resource in the light rare earth mixed ore in Baotou, Inner Mongolia, and fluorine and phosphorus, the main associated resources, and the products are phosphoric acid, cerium oxide, and potassium fluoborate, all of which are products with wide industrial applications and clear commercial values. It replaces the recovery product forms mainly composed of cerium fluoride and cerium phosphate in the traditional process, and improves the economic benefits of resource recovery.

[0132] The test results show that the method of the present invention enables the total recovery rate of Ce to reach more than 94%, the total recovery rate of P to reach more than 93%, and the total recovery rate of F to reach more than 93%.

[0133] To further understand the present invention, the preferred implementation schemes of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0134] Example 1

[0135] (A) Preparation of extraction solvent:

[0136] Weigh the extractant N1923 and the extractant Cyanex923, dilute them in the diluent n-heptane, and mix them evenly to obtain the extraction solvent. In the obtained extraction solvent, the concentration of the extractant Cyanex923 is 10 vol%, and the concentration of the extractant N1923 is 5 vol%.

[0137] (B) Preparation of raw material liquid:

[0138] Roast the mixed rare earth ore of bastnaesite in Baotou at 500 °C for 2 h, and then leach it with an acid solution at a leaching temperature of 85 °C and a time of 20 min to obtain a leachate.

[0139] Among them, the acid solution used is a mixed acid solution of sulfuric acid and boric acid; the concentration of the sulfuric acid used is 2 M, the dosage of boric acid is determined according to the B / F molar ratio of 0.2, and the leachate-solid ratio L / S = 3.

[0140] (C) Co-extraction:

[0141] Single-stage extraction: Mix the extraction solvent obtained in step (A) with the leachate obtained in step (B) according to the phase ratio O / A = 1:1, oscillate at 260 rpm for 20 min, and then let it stand for 5 min to separate phases, respectively obtaining a loaded organic phase (loaded with Ce(IV)+P+B+F) and a raffinate.

[0142] (D) Back-extraction of phosphorus:

[0143] The stripping agent 1 (H2SO4 solution with a concentration of 2 mol / L) is mixed with the loaded organic phase obtained in step (C) at a phase ratio of O / A = 1:1, shaken at 260 rpm for 20 min, and then left to stand for 5 min for phase separation to obtain the stripped organic phase 1 (loaded with Ce(IV)+B+F) and the stripping solution 1 respectively.

[0144] In this step, the stripping agent is sulfuric acid. In the presence of B, the stripping rate of F is very low, and the addition of N1923 makes it difficult for cerium to be stripped by sulfuric acid. Therefore, in this step, most of the P is stripped from the organic phase and enters the stripping solution 1, while Ce(IV)+B+F remains in the organic phase. Stripping results: the stripping rate of P is 98.89%, the stripping rate of Ce(IV) is less than 6.78%, the stripping rate of F is less than 4.77%, and the stripping rate of B is 4.03%.

[0145] (E) Stripping cerium:

[0146] The stripping agent 2 is mixed with the stripped organic phase 1 obtained in step (D) at a phase ratio of O / A = 1:1, shaken at 260 rpm for 20 min, and then left to stand for 5 min for phase separation to obtain the stripped organic phase 2 (loaded with B-F) and the stripping solution 2 (containing Ce(IV)) respectively.

[0147] Among them, the used stripping agent 2 is a mixed solution of hydrogen peroxide and sulfuric acid, and the volume concentration of hydrogen peroxide in the mixed solution is 2 vol%, and the concentration of H2SO4 is 2 mol / L.

[0148] Stripping results: the stripping rate of Ce(IV) is 99.56%, the stripping rate of F is less than 5.09%, and the stripping rate of B is 4.62%.

[0149] (F) Stripping boron and fluorine:

[0150] The stripping agent 3 (ammonia water with a concentration of 0.5 mol / L) is mixed with the stripped organic phase 2 obtained in step (E) at a phase ratio of O / A = 1:1, shaken at 260 rpm for 20 min, and then left to stand for 5 min for phase separation to obtain the blank organic phase 3 and the stripping solution 3 (containing BF4 - )

[0151] (G) Preparing products:

[0152] Corresponding metered calcium carbonate is added to the stripping solution 1 obtained in step (D) to precipitate gypsum, and a phosphorus-containing solution and gypsum are obtained respectively. Then, the phosphorus-containing solution is subjected to evaporation, concentration and rectification to obtain phosphoric acid.

[0153] Sodium hydroxide is added to the stripping solution 2 obtained in step (E) to form a cerium hydroxide precipitate, and the precipitate is filtered out and calcined at 800 °C for 3 h to obtain cerium oxide (CeO2). Figure 2 is the SEM image of the obtained cerium oxide product, whereFigure 2 (A) and Figure 2 (B) are SEM images at different magnifications.

[0154] Potassium chloride (K / B molar ratio = 4) was added to the stripping solution 3 obtained in step (F), the pH value was adjusted to 2, and the temperature was 25 °C. Potassium tetrafluoroborate precipitate was formed in the system. The precipitate was filtered out and dried to obtain potassium tetrafluoroborate (KBF4). Figure 3 is the SEM image of the obtained potassium tetrafluoroborate product, where Figure 3 (A) and Figure 3 (B) are SEM images at different magnifications.

[0155] The contents of relevant elements in each step are shown in Table 1:

[0156] Table 1: Contents of relevant elements in each step

[0157]

[0158] As can be seen from the above table, after the extraction operation, most of Ce, F, P, and B are loaded in the organic phase. The contents of Ce, F, P, and B in the raffinate are low, and the separation effect is obvious. After multiple stages, they can be completely extracted into the organic phase. Since a large amount of F and P enter the organic phase, it avoids "the formation of rare earth fluoride and phosphate precipitates due to the combination of free F and P with trivalent rare earths (La, Pr, etc.) in the raffinate because F and P need to complex with Ce to be stable in the leaching solution in the traditional process"; Ce, F, and P are concentrated in each stripping solution, indicating less loss of other elements during the impurity removal process, and the obtained product has high economic benefits.

[0159] Overall results: The total recovery rate of Ce is 98.70%, the total recovery rate of P is 96.29%, and the total recovery rate of F is 95.24%.

[0160] Example 2

[0161] (A) Preparation of extraction solvent:

[0162] The extractant N1923 and the extractant Cyanex923 were weighed and diluted in the diluent n-hexane and mixed evenly to obtain the extraction solvent. In the obtained extraction solvent, the concentration of the extractant Cyanex923 is 4 vol%, and the concentration of the extractant N1923 is 2 vol%.

[0163] (B) Preparation of feed solution:

[0164] The mixed rare earth ore of bastnasite from Baotou was oxidized and roasted at 500 °C for 2 h, and then leached with an acid solution at a leaching temperature of 85 °C and a time of 30 min to obtain a leaching solution.

[0165] Among them, the acid solution used is a mixed acid solution of sulfuric acid and boric acid; the concentration of the sulfuric acid used is 3M, the dosage of boric acid is determined according to the B / F molar ratio of 0.5, and the leaching liquid-solid ratio L / S = 4.

[0166] (C) Co-extraction:

[0167] Single-stage extraction: The extraction solvent obtained in step (A) and the leaching solution obtained in step (B) are mixed according to the phase ratio O / A = 1:1, oscillated at 200 rpm for 25 min, then left to stand for 10 min for phase separation to obtain a loaded organic phase (loaded with Ce(IV)+P+B+F) and a raffinate respectively.

[0168] (D) Stripping of phosphorus:

[0169] The stripping agent 1 (H2SO4 solution with a concentration of 1 mol / L) and the loaded organic phase obtained in step (C) are mixed according to the phase ratio O / A = 0.5:1, oscillated at 200 rpm for 25 min, then left to stand for 10 min for phase separation to obtain a stripped organic phase 1 (loaded with Ce(IV)+B+F) and a stripping solution 1 respectively.

[0170] In this step, the stripping agent is sulfuric acid. In the presence of B, the stripping rate of F is very low, and the addition of N1923 makes it difficult for cerium to be stripped by sulfuric acid. Therefore, in this step, most of the P is stripped from the organic phase and enters the stripping solution 1, while Ce(IV)+B+F remains in the organic phase. Stripping result: The stripping rate of P is 95.73%, the stripping rate of Ce(IV) is lower than 3.21%, the stripping rate of F is lower than 2.36%, and the stripping rate of B is 2.91%.

[0171] (E) Stripping of cerium:

[0172] The stripping agent 2 and the stripped organic phase 1 obtained in step (D) are mixed according to the phase ratio O / A = 0.5:1, oscillated at 200 rpm for 25 min, then left to stand for 10 min for phase separation to obtain a stripped organic phase 2 (loaded with B-F) and a stripping solution 2 (containing Ce(IV)) respectively.

[0173] Among them, the stripping agent 2 used is a mixed solution of hydrogen peroxide and sulfuric acid, and the volume concentration of hydrogen peroxide in the mixed solution is 1 vol%, and the concentration of H2SO4 is 0.5 mol / L.

[0174] Stripping result: The stripping rate of Ce(IV) is 97.33%, the stripping rate of F is lower than 4.61%, and the stripping rate of B is 3.88%.

[0175] (F) Stripping of boron and fluorine:

[0176] The stripping agent 3 (ammonia water with a concentration of 0.8 mol / L) is mixed with the stripped organic phase 2 obtained in step (E) at a phase ratio of O / A = 0.5:1, shaken at 200 rpm for 25 min, and then left to stand for 10 min for phase separation to obtain a blank organic phase 3 and a stripping solution 3 (containing BF4 - ).

[0177] (G) Preparation of products:

[0178] Corresponding metered calcium hydrogen phosphate is added to the stripping solution 1 obtained in step (D) to precipitate gypsum, and a phosphorus-containing solution and gypsum are obtained respectively. Then, the phosphorus-containing solution is subjected to evaporation, concentration and rectification to obtain phosphoric acid.

[0179] Sodium oxalate is added to the stripping solution 2 obtained in step (E) to form cerium oxalate precipitate. The precipitate is filtered out and calcined at 800 °C for 3 h to obtain cerium oxide.

[0180] Potassium chloride (K / B molar ratio = 0.8) is added to the stripping solution 3 obtained in step (F), the pH value is adjusted to 1, and the temperature is 25 °C. Potassium tetrafluoroborate precipitate is formed in the system. The precipitate is filtered out and dried to obtain potassium tetrafluoroborate (KBF4).

[0181] Overall result: The total recovery rate of Ce is 94.27%, the total recovery rate of P is 93.71%, and the total recovery rate of F is 93.82%.

[0182] Example 3

[0183] (A) Preparation of extraction solvent:

[0184] The extractant N1923 and the extractant Cyanex923 are weighed and diluted in the diluent sulfonated kerosene and mixed evenly to obtain an extraction solvent. In the obtained extraction solvent, the concentration of the extractant Cyanex923 is 20 vol%, and the concentration of the extractant N1923 is 10 vol%.

[0185] (B) Preparation of feed liquid:

[0186] The mixed rare earth ore of Bayan Obo bastnasite is oxidized and roasted at 500 °C for 2 h, and then leached with an acid solution at a leaching temperature of 85 °C and a time of 30 min to obtain a leaching solution.

[0187] Among them, the acid solution used is a mixed acid solution of sulfuric acid and boric acid; the concentration of the sulfuric acid used is 3 M, the dosage of boric acid is determined according to the B / F molar ratio of 0.5, and the leaching solution-solid ratio L / S = 5.

[0188] (C) Co-extraction:

[0189] Single-stage extraction: The extraction solvent obtained in step (A) and the leaching solution obtained in step (B) were mixed at a phase ratio of O / A = 1:1, shaken at 300 rpm for 10 min, and then allowed to stand for 5 min for phase separation to obtain a loaded organic phase (loaded with Ce(IV)+P+B+F) and a raffinate respectively.

[0190] (D) Stripping of phosphorus:

[0191] The stripping agent 1 (H2SO4 solution with a concentration of 3 mol / L) was mixed with the loaded organic phase obtained in step (C) at a phase ratio of O / A = 2:1, shaken at 300 rpm for 10 min, and then allowed to stand for 5 min for phase separation to obtain a stripped organic phase 1 (loaded with Ce(IV)+B+F) and a stripping solution 1 respectively.

[0192] In this step, the stripping agent is sulfuric acid. In the presence of B, the stripping rate of F is very low, and the addition of N1923 makes it difficult for cerium to be stripped by sulfuric acid. Therefore, in this step, most of the P is stripped from the organic phase and enters the stripping solution 1, while Ce(IV)+B+F remains in the organic phase. Stripping results: The stripping rate of P is 97.73%, the stripping rate of Ce(IV) is less than 6.31%, the stripping rate of F is less than 5.39%, and the stripping rate of B is 4.18%.

[0193] (E) Stripping of cerium:

[0194] The stripping agent 2 was mixed with the stripped organic phase 1 obtained in step (D) at a phase ratio of O / A = 2:1, shaken at 300 rpm for 10 min, and then allowed to stand for 5 min for phase separation to obtain a stripped organic phase 2 (loaded with B-F) and a stripping solution 2 (containing Ce(IV)) respectively.

[0195] Among them, the stripping agent 2 used is a mixed solution of hydrogen peroxide and sulfuric acid, and the volume concentration of hydrogen peroxide in the mixed solution is 2 vol%, and the concentration of H2SO4 is 3 mol / L.

[0196] Stripping results: The stripping rate of Ce(IV) is 98.99%, the stripping rate of F is less than 3.17%, and the stripping rate of B is 2.82%.

[0197] (F) Stripping of boron and fluorine:

[0198] The stripping agent 3 (ammonia water with a concentration of 0.8 mol / L) was mixed with the stripped organic phase 2 obtained in step (E) at a phase ratio of O / A = 2:1, shaken at 300 rpm for 10 min, and then allowed to stand for 5 min for phase separation to obtain a blank organic phase 3 and a stripping solution 3 (containing BF4 - )

[0199] (G) Preparation of products:

[0200] Calcium dihydrogen phosphate in corresponding dosage is added to the stripping solution 1 obtained in step (D) to precipitate gypsum, and a phosphorus-containing solution and gypsum are obtained respectively. Then, the phosphorus-containing solution is subjected to evaporation, concentration and rectification to obtain phosphoric acid.

[0201] Oxalic acid is added to the stripping solution 2 obtained in step (E) to form cerium oxalate precipitate. The precipitate is filtered out and calcined at 800 °C for 3 h to obtain cerium oxide.

[0202] Potassium chloride (K / B molar ratio = 0.8) is added to the stripping solution 3 obtained in step (F), the pH value is adjusted to 1, and the temperature is 25 °C. Potassium tetrafluoroborate precipitate is formed in the system. The precipitate is filtered out and dried to obtain potassium tetrafluoroborate (KBF4).

[0203] Overall result: The total recovery rate of Ce is 97.87%, the total recovery rate of P is 95.44%, and the total recovery rate of F is 93.89%.

[0204] Comparative Example 1

[0205] It is carried out according to Example 1, except that the extractant N1923 in step (A) is replaced with extractant Cyanex923 (i.e., all extractants are Cyanex923).

[0206] Result: The total recovery rate of Ce is 93.31%, the total recovery rate of P is 82.32%, the total recovery rate of F is 90.61%, and a small amount of cerium phosphate is mixed in the stripping product.

[0207] Comparative Example 2

[0208] It is carried out according to Example 1, except that the extractant Cyanex923 in step (A) is replaced with extractant N1923 (i.e., all extractants are N1923).

[0209] Result: The total recovery rate of Ce is 94.18%, the total recovery rate of P is 34.77%, the total recovery rate of F is 67.64%. The stripping of fluorine and phosphorus is incomplete.

[0210] It can be seen from the effect comparison between Example 1 and Comparative Examples 1-2 that the recovery rates of each element in Comparative Examples 1-2 are all lower than those in Example 1, which proves that the effect of co-extraction with extractant N1923 + extractant Cyanex923 in the present invention is better than that of using any one of the single extractants, indicating that extractant N1923 + extractant Cyanex923 in the system of the present invention plays a synergistic extraction role and significantly improves the separation and recovery effect of cerium, fluorine and phosphorus in the rare earth mixed ore.

[0211] Comparative Example 3

[0212] It is carried out according to Example 1, except that the extractant Cyanex923 in step (A) is replaced with another neutral phosphine extractant TBP.

[0213] Results: The total recovery rate of Ce was 87.32%, the total recovery rate of P was 72.33%, and the total recovery rate of F was 84.73%.

[0214] Comparative Example 4

[0215] It was carried out according to Example 1, except that the extractant N1923 in step (A) was replaced with another extractant P507.

[0216] Results: The total recovery rate of Ce was 76.32%, the total recovery rate of P was 64.27%, and the total recovery rate of F was 76.88%.

[0217] It can be seen from the comparison of the effects of Example 1 and Comparative Examples 3-4 that the recovery rates of each element in Comparative Examples 3-4 are lower than those in Example 1, which proves that compared with other combinations, the combination of extractant N1923 + extractant Cyanex923 used in the present invention can effectively improve the separation and recovery effect of cerium, fluorine and phosphorus in rare earth mixed ores.

[0218] In this article, specific examples are used to elaborate on the principle and implementation mode of the present invention. The description of the above examples is only used to help understand the method and its core idea of the present invention, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of this invention patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for extracting cerium fluorophosphate from rare earth mixed ore by co-extraction method, which is characterized in that, It includes the following steps: (A) Prepare an extraction solvent: Mix the extractant N1923, the extractant Cyanex923 and a diluent to obtain an extraction solvent; (B) Prepare a feed solution: Perform oxidative roasting on the mixed rare earth ore, and then leach it with an acid solution to obtain a leachate; (C) Co-extraction: Use the extraction solvent obtained in step (A) to extract the leachate obtained in step (B) to obtain a loaded organic phase and a raffinate respectively; (D) Stripping of phosphorus: Use a stripping agent 1 to strip the loaded organic phase to obtain a stripped organic phase 1 and a stripping solution 1 respectively; Wherein, the stripping agent 1 is a sulfuric acid solution; (E) Stripping of cerium: Use a stripping agent 2 to strip the stripped organic phase 1 to obtain a stripped organic phase 2 and a stripping solution 2 respectively; Wherein, the stripping agent 2 is a mixed solution of sulfuric acid and hydrogen peroxide; (F) Stripping of boron and fluorine: Use a stripping agent 3 to strip the stripped organic phase 2 to obtain a blank organic phase 3 and a stripping solution 3 respectively; Wherein, the stripping agent 3 is ammonia water; (G) Prepare products: Remove impurities from the stripping solution 1 to obtain phosphoric acid; Mix the stripping solution 2 with a precipitant to precipitate cerium hydroxide or cerium oxalate, and then calcine to obtain cerium oxide; Mix the stripping solution 3 with a potassium salt, adjust the pH value, perform solid-liquid separation and drying to obtain potassium tetrafluoroborate; In the above steps, for steps without a sequential relationship, their order has no special limitation.

2. The method according to claim 1, characterized in that, In step (A), the concentration of the extractant N1923 in the extraction solvent is 5 vol% to 15 vol%, and the concentration of the extractant Cyanex923 is 10 vol% to 30 vol%.

3. The method according to claim 1 or 2, characterized in that, In step (A), the diluent is at least one of sulfonated kerosene, n-hexane, and n-heptane.

4. The method according to claim 1, wherein In step (B): The temperature of the oxidative roasting is 300 to 700 °C, and the time is 1 to 4 h; The acid solution is a mixed acid solution of sulfuric acid and boric acid; The concentration of the sulfuric acid is 2 to 3 M; The dosage of the boric acid is controlled as follows: the molar ratio of B in the boric acid to F in the mixed rare earth ore is 0.2 to 0.5; The liquid-solid ratio of the leaching is 3 to 5.

5. The method according to claim 1, characterized in that, In step (B), the temperature of the leaching is 60 to 95 °C, and the time is 10 to 90 min.

6. The method according to claim 1, characterized in that, In step (C), the ratio of the extraction solvent obtained in step (A) to the leachate obtained in step (B) is (0.5 to 2):

1.

7. The method according to claim 1, characterized in that, In step (D): The concentration of the sulfuric acid solution is 0.5 to 2 mol / L; The ratio of the loaded organic phase to the stripping agent 1 is (0.5 to 2):

1.

8. The method according to claim 1, wherein In step (E): The volume concentration of hydrogen peroxide in the mixed solution is 0.5 vol% to 2 vol%, and the concentration of H2SO4 is 0.5 to 2 mol / L; The ratio of the stripped organic phase 1 to the stripping agent 2 is (0.5 to 2):

1.

9. The method according to claim 1, characterized in that, In step (F): The concentration of the ammonia water is 0.5 to 1 mol / L; The ratio of the stripped organic phase 2 to the stripping agent 3 is (0.5 to 2):

1.

10. The method according to claim 1, characterized in that In step (G): The impurity removal process includes: mixing the stripping solution 1 with an impurity remover, and then performing solid-liquid separation to obtain a phosphorus-containing solution and gypsum respectively; then, recover phosphorus in the phosphorus-containing solution to obtain phosphoric acid; The impurity remover is at least one of calcium carbonate, calcium hydrogen phosphate, calcium dihydrogen phosphate, and calcium hydroxide; The precipitating agent is at least one of sodium hydroxide, sodium oxalate, and oxalic acid; The potassium salt is at least one of potassium chloride, potassium nitrate, and potassium sulfate; The pH value is adjusted to 1-3.

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