Method for preparing fluorine-containing metal organic framework material and recovering associated rare earth

Abstract

The invention provides a method for preparing a fluorine-containing metal organic framework material and recovering associated rare earth, and the preparation of the material comprises the following steps: mixing zirconium oxychloride octahydrate, 1, 3, 5-benzene tricarboxylic acid, 2, 3, 5, 6-tetrafluoroterephthalic acid and a solvent, and reacting. Through the prepared fluorine-containing metal organic framework material, total rare earth is efficiently enriched from an acidic complex solution, low-concentration rare earth in an acidic complex system can be selectively and efficiently recovered in the presence of high-concentration main metal ions, associated rare earth resources are recycled, loss of the rare earth resources is avoided, and the method is suitable for industrial production. And the economic benefit of the whole process flow is improved.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, specifically relating to a method for preparing fluorine-containing metal-organic framework materials and recovering associated rare earth elements. Background Technology

[0002] Rare earth elements are widely used in military, metallurgy, petroleum, chemical, materials, agriculture, and pharmaceutical fields. They are core resources for developing emerging industries such as new energy, new materials, aerospace, and electronic information, and their development and utilization are of great significance, with demand increasing year by year. my country has the largest rare earth reserves, but these reserves are declining annually. At the current production rate, imports will be necessary to meet demand in a few years. Therefore, the development and utilization of associated rare earth resources has begun to receive attention and importance. my country has many associated rare earth deposits with high comprehensive utilization value, but due to their low grade, fine ore particle size, complex material composition, and difficulty in element separation, their comprehensive recovery and utilization rate is still low. In the research on the extraction of associated rare earths from discovered rare earth phosphate mines, deep-sea rare earth-rich sediments, rare earth-containing cobalt-manganese polymetallic mines, and uranium-niobium rare earth mines, the problems of high energy consumption, long process, high acid consumption, severe equipment corrosion, high main metal concentration, low rare earth concentration, difficulty in enrichment, and serious environmental pollution are often difficult to solve. Currently, the development of efficient and green recovery processes for associated rare earth mines still faces many challenges.

[0003] Currently, there are relatively few reports on associated rare earth enrichment and recovery technologies, and most related research focuses on extracting rare earth elements from deep-sea rare earth-rich sediments. Patent application CN111876586A proposes a method for the comprehensive recovery of all elements from cobalt-rich oceanic crusts through biomass roasting and reduction. This method utilizes liquid-phase extraction technology for the enrichment and recovery of total rare earth elements, using N1932, 2-octanol, and kerosene as extractants, achieving rare earth recovery rates of 83.26% and 84.76%, respectively. Patent application CN107557576A describes a method for extracting rare earth elements from deep-sea sediments, using extractants such as P204, TBP, and kerosene for 2-15 stages of extraction, followed by 5-15 stages of back-extraction with acidic solutions such as hydrochloric acid and sulfuric acid to obtain a rare earth solution with a total rare earth recovery rate of approximately 77%-94%. These methods all require the use of one or more organic solvents as extractants, which can easily cause equipment corrosion. Some extractants have serious toxic side effects and pose safety hazards. Furthermore, their extraction efficiency for low-concentration rare earth elements is not ideal, requiring prior concentration, resulting in long process flows and high energy consumption. Invention patent application CN115554981A discloses a method for adsorbing and enriching low-concentration rare earth ions using carbonized products of residual sludge. This method utilizes residual sludge to prepare carbonized products and uses adsorption to adsorb low-concentration rare earth ions, achieving an average adsorption efficiency of 84.51% for each rare earth element. However, because this invention does not mention solution acidity, and most adsorbents suffer from adsorption deactivation, low adsorption rate, and poor selectivity under acidic conditions, it is impossible to effectively evaluate the adsorption selectivity and efficiency of this carbonized product in complex acidic systems.

[0004] In addition, the development of adsorbents related to rare earth ion adsorption and enrichment is progressing steadily. Patent application CN119075948A discloses a porous metal-organic framework-derived material for adsorbing rare earth metal ions, its preparation method, and its application. By preparing MOF-808-PBTCA material and using a self-made mixed solution of transition metal salts and rare earth metal salts in ultrapure water, the adsorption performance of rare earth ions in water was tested. The results showed that the material has a high adsorption efficiency for rare earth ions. However, this method only performs rare earth adsorption in water, and the ion concentrations of the target metal and impurity metals are essentially the same. Invention patent application CN119505269A discloses a method for preparing ionic metal-organic frameworks and their application in rare earth separation. By preparing three-dimensional ionic metal-organic framework materials, light rare earth ions are selectively adsorbed under conditions where interfering ions and heavy rare earth ions coexist. This method utilizes the exchange between counter cations in the framework and lanthanide hydrated ions, thereby enhancing the separation effect of rare earths. Enrichment studies of light rare earth ions in tailings wastewater have been conducted, and the concentrations of impurity metals and light rare earth ions are basically on the same order of magnitude, and the method is only effective for light rare earth ions.

[0005] Associated rare earth minerals are usually leached with sulfuric acid, resulting in a complex acidic solution characterized by high acidity, complex composition, high concentration of main metals, and low content of rare earth elements. Typically, the concentration of main metal elements differs from that of total rare earth elements by tens to hundreds of orders of magnitude. Directly selectively enriching and recovering total rare earth elements from the solution is not easy. Therefore, there is an urgent need to develop adsorbent materials with good selectivity for total rare earth elements, strong anti-interference ability, and strong resistance to acidic solutions. These materials can selectively enrich and extract low-concentration rare earth elements from complex acidic solutions while eliminating interference from high-concentration main metal elements, thereby achieving comprehensive recovery of rare earth elements. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for preparing fluorine-containing metal-organic framework materials and recovering associated rare earth elements from acidic complex solutions. This invention utilizes the prepared fluorine-containing metal-organic framework materials to efficiently recover low concentrations of associated rare earth elements from acidic complex systems. The method of this invention has advantages such as simple operation, low energy consumption, short process, high single-cycle recovery rate, and safety and environmental friendliness.

[0007] In a first aspect, this invention provides a method for preparing a fluorine-containing metal-organic framework material, comprising mixing and reacting zirconium oxychloride octahydrate, 1,3,5-benzenetricarboxylic acid, 2,3,5,6-tetrafluoroterephthalic acid, and a solvent. The method of this invention utilizes the synthesized fluorine-containing metal-organic framework material for the recovery of associated rare earth elements from acidic and complex solutions. It can effectively and selectively enrich and extract low concentrations of total rare earth elements from acidic and complex solutions, achieving comprehensive recovery and utilization of associated rare earth resources.

[0008] Preferably, the solvent is a mixture of N,N-dimethylformamide and water.

[0009] Preferably, the volume ratio of N,N-dimethylformamide to water is (1~10):1, for example, 1:1, 2:1, 3:1, 4:1, 6.5:1, etc. In this invention, by optimizing the solvent to a mixed solvent of N,N-dimethylformamide (DMF) and water in a certain proportion, the formation of fluorine-containing metal-organic framework materials can be better promoted, the morphology and crystal form of the materials can be improved, and the prepared fluorine-containing metal-organic framework materials can have better performance.

[0010] Preferably, the mixture also includes an organic acid auxiliary agent selected from one or more of formic acid, acetic acid, and propionic acid.

[0011] Preferably, the volume ratio of the organic acid additive to the solvent is (0~1):(0~10), more preferably 1:(1~10), for example, 1:1, 1:2, 1:3, 1:4, etc. The organic acid additive used in this invention optimizes the material structure and morphology. Its combined action with the mixed solvent helps improve the performance of the prepared fluorine-containing metal-organic framework material, aids in increasing the recovery rate of rare earth elements, and avoids excessive interference from main metal ions, thereby improving the recovery effect of rare earth elements.

[0012] Preferably, the molar ratio of zirconium oxychloride octahydrate, 1,3,5-benzenetricarboxylic acid, and 2,3,5,6-tetrafluoroterephthalic acid is (0~10):(0~1):(0~1), preferably 1:(0~1):(0~1), for example, 1:(0.01~1):(0.01~1), 1:1:1, 1:0.2:0.2, 1:0.3:0.3, 1:0.4:0.2, etc. In this invention, by using zirconium oxychloride octahydrate, 1,3,5-benzenetricarboxylic acid, and 2,3,5,6-tetrafluoroterephthalic acid in a certain proportion, under the action of organic acid additives and solvents, the pore structure, surface characteristics, and adsorption performance of fluorine-containing metal-organic framework materials can be more effectively adjusted, enabling them to more efficiently adsorb and enrich rare earth elements. The preferred molar ratio helps to further adjust the physicochemical properties of the material, significantly improving the efficiency and selectivity of rare earth recovery.

[0013] Further preferred, the reaction time is 6~72h; for example, all times within the time range of 12~72h, 12h, 24h, 36h, 72h, etc.; the reaction temperature is 60~150℃; for example, all temperatures within the temperature range of 65~150℃, 65℃, 80℃, 100℃, 125℃, 150℃, etc.

[0014] Preferably, the reaction further includes post-treatment of filtration, washing and drying, wherein the washing reagent is selected from one or more of methanol, ethanol, acetone, dichloromethane, water and N,N-dimethylformamide.

[0015] This invention involves dissolving zirconium oxychloride octahydrate, 1,3,5-benzenetricarboxylic acid, and 2,3,5,6-tetrafluoroterephthalic acid in a solvent in a specific ratio, and reacting them under certain additives, reaction temperature, and reaction time to prepare a fluorine-containing metal-organic framework (MOF). The resulting fluorine-containing MOF, after solid-liquid separation, collection, washing, activation, and drying, can be effectively used to recover rare earth elements from acidic complex solutions. This invention, through the preparation of the fluorine-containing MOF and its method for recovering associated rare earth elements, can efficiently enrich total rare earth elements from acidic complex solutions, achieving a total rare earth recovery rate of over 80.0%, with some single rare earth element recovery rates reaching up to 99.8%, light rare earth recovery rates of approximately 80%–85%, and medium and heavy rare earth recovery rates of approximately 80%–90%. In the presence of high-concentration main metal ions, low-concentration rare earth elements in acidic complex systems can be selectively and efficiently recovered, realizing the recycling of associated rare earth resources, avoiding the loss of rare earth resources, and improving the overall economic efficiency of the process.

[0016] Secondly, the present invention provides a fluorine-containing metal-organic framework material, which is obtained by the above-mentioned preparation method of the fluorine-containing metal-organic framework material.

[0017] Thirdly, the present invention provides a method for recovering associated rare earth elements from an acidic complex solution, wherein a fluorine-containing metal-organic framework material obtained by the above preparation method or the above-mentioned fluorine-containing metal-organic framework material is added to the solution to be treated for treatment; the solution to be treated is an acidic complex solution.

[0018] Preferably, the acidic complex solution is a mixed solution containing low concentrations of rare earth elements produced during the extraction of the main metal element in a metallurgical process. The solution has a complex composition with significant differences in the content of each element, and the concentration of the main metal element differs from that of the total rare earth element by tens to hundreds of orders of magnitude. Preferably, it includes (sulfuric acid) leaching solutions of rare earth cobalt-manganese polymetallic ores, associated rare earth phosphate ores, deep-sea rare earth-rich sediments, uranium-niobium rare earth ores, or vanadium-uranium ores. The leaching solutions of rare earth cobalt-manganese polymetallic ores include deep-sea polymetallic nodule leaching solutions and cobalt-rich crust leaching solutions. Preferably, the pH of the acidic complex solution is 1 to 7, and more preferably 2 to 5.

[0019] Preferably, the ratio of the fluorinated metal-organic framework material to the solution to be treated is 1 mg:1 mL to 10 mg:1 mL, for example, any ratio within the range of 1:1, 2:1, 2.5:1, 5:1, 10:1 (mg:mL). In this invention, using the fluorinated metal-organic framework material and the solution to be treated at a certain ratio can better ensure the treatment effect and enhance the adsorption capacity of rare earth elements.

[0020] Preferably, the processing time is 1 to 1440 min, for example, all times within the time range of 60 min, 120 min, 200 min, 240 min, 360 min, 720 min, 1440 min, etc.; the processing temperature is 10 to 70℃, for example, all temperatures within the temperature range of 10℃, 25℃, 40℃, 65℃, 70℃, etc.

[0021] This invention adds a certain dose of fluorine-containing metal-organic framework material to an acidic complex solution to enrich and recover total rare earth elements under certain treatment time and temperature. In the presence of high concentration of main metal ions, it selectively and efficiently recovers low concentrations of rare earth elements in the acidic complex system, thereby better realizing the recycling of associated rare earth resources, avoiding the loss of rare earth resources, and improving the economic efficiency of the overall process.

[0022] The beneficial effects of this invention are at least as follows: the method for preparing fluorine-containing metal-organic framework materials provided by this invention is simple and the conditions are mild; the prepared fluorine-containing metal-organic framework materials can selectively adsorb low concentrations of rare earth ions in acidic complex solutions. The rare earth recovery method provided by this invention is simple and feasible; it can selectively adsorb rare earths even when there are many types of main and auxiliary elements with large concentration differences, which helps to simplify the recovery operation steps and achieve rare earth recovery with a more streamlined and efficient process, making it highly valuable for promotion. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0025] Unless otherwise specified, the reagents, materials and instruments used in the embodiments and comparative examples of this invention are all conventional reagents, materials and instruments that can be purchased. The reagents involved can also be obtained by purchasing or by synthesizing them using conventional synthesis methods.

[0026] In this embodiment of the invention, the total rare earth recovery rate (in terms of REE) is the percentage of the total amount of rare earth elements (REE) recovered relative to the total amount of rare earth elements in the original raw material.

[0027] Example 1 This embodiment provides a fluorine-containing metal-organic framework material and its preparation method, the steps of which are as follows: 350 mg of zirconium oxychloride octahydrate, 1,3,5-benzenetricarboxylic acid, and 2,3,5,6-tetrafluoroterephthalic acid are dissolved in 10 mL of a mixed solution of N,N-dimethylformamide / water (volume ratio 1:1) at a molar ratio of 1:0.22:0.35. Then, 2 mL of formic acid is added, and the mixture is stirred evenly. The mixture is reacted at 65 °C for 36 h. After the reaction is completed, the white solid is collected by filtration, washed with methanol, and dried to obtain a white solid, which is the fluorine-containing metal-organic framework material.

[0028] Example 2 Example 2 is an application example of Example 1, namely, a method for recovering associated rare earth elements from an acidic complex solution using fluorinated metal-organic framework materials. The acidic complex solution used is a leaching solution of a rare earth-containing nickel-cobalt-manganese polymetallic ore with a pH of 4. The components are detailed in Table 1. The specific operation is as follows: 50 mg of the fluorinated metal-organic framework material is added to 10 mL of the leaching solution, stirred at room temperature for 4 h, and then filtered to obtain the rare earth enriched material and the adsorbed solution (Table 2). The results show that the total rare earth recovery rate (based on REE) is 85.02%, of which the light rare earth recovery rate is 85.00%, the medium and heavy rare earth recovery rate is 85.09%, and the recovery rate of some single elements (scandium, thulium, and ytterbium) is over 90%. The fluorinated metal-organic framework material hardly adsorbs nickel, cobalt, and manganese, indicating that it has a good enrichment and extraction effect on low-concentration rare earth elements in the leaching solution.

[0029] Table 1. Composition of Leachate from Rare Earth Nickel-Cobalt-Manganese Polymetallic Ores

[0030] Table 2. Components of the liquid after adsorption of rare earth nickel-cobalt-manganese polymetallic ores

[0031] Example 3 Example 3 is an application example of Example 1, namely, a method for recovering rare earth elements from an acidic complex solution using fluorinated metal-organic framework materials. The acidic complex solution used is the uranium leaching residue from the uranium-niobium concentrate smelting process, with a pH of approximately 3. The components are detailed in Table 3. The specific operation is as follows: 40 mg of the fluorinated metal-organic framework material is added to 10 mL of the uranium leaching residue, stirred at room temperature for 2 hours, and then filtered to obtain the rare earth enriched material and the adsorbed uranium leaching residue (Table 4). The results show that the total rare earth recovery rate (based on REE) is 80.41%; among which, the light rare earth recovery rate is 80.47%, the medium and heavy rare earth recovery rate is 80.25%, and the recovery rate of some single elements (scandium and thulium) reaches over 93%. The fluorinated metal-organic framework material has a poor adsorption effect on iron, indicating that it has a good enrichment and extraction effect on low-concentration rare earth elements in the uranium leaching residue from the uranium-niobium concentrate smelting process.

[0032] Table 3. Composition of Uranium Extraction Liquid in Uranium-Niobium Concentrate Smelting Process

[0033] Table 4. Composition of liquid after adsorption in uranium extraction residue during uranium-niobium concentrate smelting process.

[0034] Example 4 Example 4 illustrates the application of Example 1, specifically a method for recovering rare earth elements from an acidic complex solution using a fluorinated metal-organic framework (MOF). The acidic complex solution used was a leaching solution of associated rare earth phosphate rock, the composition of which is detailed in Table 5. The specific procedure involved adding 20 mg of the fluorinated MOF to the leaching solution at pH 2.5, stirring at room temperature for 1 hour, followed by filtration to obtain the rare earth enriched material and the adsorbed solution (Table 6). The results showed that the total rare earth recovery rate (based on REE) was 83.65%, with a light rare earth recovery rate of 81.21%, a medium-heavy rare earth recovery rate of 89.89%, and some single elements (dysprosium, erbium, gadolinium, and samarium) recoveries exceeding 90%. The fluorinated MOF provided by this invention exhibits good enrichment and extraction effects on low-concentration rare earth elements in the leaching solution of associated rare earth phosphate rock.

[0035] Table 5. Composition of Leachate from Associated Rare Earth Phosphate Rock

[0036] Table 6. Composition of Leachate from Associated Rare Earth Phosphate Rock after Adsorption

[0037] Example 5 This embodiment provides a fluorine-containing metal-organic framework material and its preparation method. The only difference from the method in Example 1 is that 300 mg of zirconium oxychloride octahydrate, 1,3,5-benzenetricarboxylic acid, and 2,3,5,6-tetrafluoroterephthalic acid are dissolved in 15 mL of a mixed solution of N,N-dimethylformamide / water (volume ratio 1:1) at a molar ratio of 1:0.1:0.15, and the mixture is reacted at 65 °C for 24 h. After the reaction is complete, the mixture is washed with ethanol, aged, and dried to obtain a white gel-like solid.

[0038] Example 6 This embodiment provides a fluorine-containing metal-organic framework material and its preparation method, which differs from the method in Example 1 only in that 5 mL of formic acid is added. After the reaction is complete, the white solid is collected by filtration, then washed with methanol, and dried to obtain a white solid. As can be seen from Examples 1 and 5-6 above, the added organic acid auxiliaries have a certain influence on the morphology of the fluorine-containing metal-organic framework material.

[0039] Example 7 This embodiment provides a fluorine-containing metal-organic framework material and its preparation method, differing from Example 1 in that: 150 mg of zirconium oxychloride octahydrate, 1,3,5-benzenetricarboxylic acid, and 2,3,5,6-tetrafluoroterephthalic acid were dissolved in 10 mL of N,N-dimethylformamide solution at a molar ratio of 1:0.22:0.35, followed by the addition of 5 mL of formic acid. The mixture was then thoroughly mixed and reacted at 65°C for 72 h. After the reaction, the solution became clear, but the target fluorine-containing metal-organic framework material was not obtained.

[0040] Example 8 This embodiment provides a fluorine-containing metal-organic framework material and its preparation method, which differs from Example 1 in that: 300 mg of zirconium oxychloride octahydrate, 1,3,5-benzenetricarboxylic acid, and 2,3,5,6-tetrafluoroterephthalic acid are dissolved in 10 mL of N,N-dimethylformamide solution / water (volume ratio 1:1) at a molar ratio of 1:0.22:0.35, followed by the addition of 5 mL of formic acid. The mixture is then thoroughly mixed and reacted at 100 °C for 72 h. After the reaction is complete, a white floating flocculent substance is obtained.

[0041] Example 9 This embodiment provides a fluorine-containing metal-organic framework material and its preparation method. The difference from Example 1 is that 155 mg of zirconium oxychloride octahydrate, 1,3,5-benzenetricarboxylic acid, and 2,3,5,6-tetrafluoroterephthalic acid were dissolved in 15 mL of N,N-dimethylformamide solution / water (volume ratio 4:1) at a molar ratio of 1:0.22:0.35, and the reaction was carried out at 65°C for 36 h. After the reaction, a white gel-like paste was obtained. As can be seen from Examples 1 and 7-9 above, the absence of water in the solvent directly affects the preparation of fluorine-containing metal-organic framework materials; temperature and the ratio of N,N-dimethylformamide solution to water in the solvent affect the morphology of the fluorine-containing metal-organic framework material and whether it can be successfully prepared.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a fluorine-containing metal-organic framework material, characterized in that, The reaction involves mixing zirconium oxychloride octahydrate, 1,3,5-benzenetricarboxylic acid, 2,3,5,6-tetrafluoroterephthalic acid and a solvent and then reacting them.

2. The method for preparing the fluorine-containing metal-organic framework material according to claim 1, characterized in that, The solvent is a mixture of N,N-dimethylformamide and water; Preferably, the volume ratio of N,N-dimethylformamide to water is (1~10):

1.

3. The method for preparing the fluorine-containing metal-organic framework material according to claim 2, characterized in that, It also includes organic acid additives, which are selected from one or more of formic acid, acetic acid and propionic acid.

4. The method for preparing the fluorine-containing metal-organic framework material according to claim 3, characterized in that, The mass ratio of zirconium oxychloride octahydrate, 1,3,5-benzenetricarboxylic acid, and 2,3,5,6-tetrafluoroterephthalic acid is (0~10):(0~1):(0~1). And / or, the volume ratio of the organic acid auxiliary agent to the solvent is (0~1):(0~10).

5. The method for preparing the fluorine-containing metal-organic framework material according to any one of claims 1-4, characterized in that, The reaction time is 6~72h; the reaction temperature is 60~150℃; And / or, the reaction may further include post-treatment of filtration, washing and drying, wherein the washing reagent is selected from one or more of methanol, ethanol, acetone, dichloromethane, water, and N,N-dimethylformamide.

6. A fluorine-containing metal-organic framework material, characterized in that, It is obtained by the preparation method of the fluorine-containing metal-organic framework material according to any one of claims 1-5.

7. A method for recovering associated rare earth elements from an acidic complex solution, characterized in that, The solution to be treated is treated by adding the fluorine-containing metal-organic framework material obtained by any one of claims 1-5 or the fluorine-containing metal-organic framework material of claim 6; the solution to be treated is an acidic complex solution.

8. The method for recovering associated rare earth elements from an acidic complex solution according to claim 7, characterized in that, The acidic complex solution is a mixed solution containing low concentrations of rare earth elements produced during the extraction of the main metal element in a metallurgical process; preferably, it includes leachates from rare earth cobalt-manganese polymetallic ores, associated rare earth phosphate ores, deep-sea rare earth-rich sediments, uranium-niobium rare earth ores, or vanadium-uranium ores; the leachate from rare earth cobalt-manganese polymetallic ores includes deep-sea polymetallic nodule leachates and cobalt-rich crust leachates.

9. The method for recovering associated rare earth elements from an acidic complex solution according to claim 7 or 8, characterized in that, The ratio of the fluorine-containing metal-organic framework material to the solution to be treated is 1 mg:1 mL to 10 mg:1 mL.

10. The method for recovering associated rare earth elements from an acidic complex solution according to any one of claims 7-9, characterized in that, The processing time is 1 to 1440 minutes; the processing temperature is 10 to 70 °C.

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