Method for microwave activation of lithium slag for valuable metal separation and resource recycling

Abstract

This invention discloses a method for the separation and resource reuse of valuable metals from lithium slag through microwave activation, relating to the fields of solid waste resource utilization and material preparation. The method includes: microwave irradiation of lithium slag to dehydrate, crush, and dissociate it; followed by an ultrasonic-assisted sulfuric acid leaching process to enrich lithium, rubidium, and iron; adjusting the pH of the enriched acid leaching solution to convert iron into sodium ferric sulfate crystals for separation and purification; mixing the acid leaching residue with sodium hydroxide, activating it through microwave alkaline fusion, and then extracting silicon and aluminum through ultrasonic water leaching; finally, mixing the silicon and aluminum-containing leaching solution with a silicon source, template agent, and sodium ferric sulfate crystals, and then performing microwave hydrothermal synthesis, oxidative roasting, and ion exchange to obtain iron-modified ZSM-5 molecular sieve. This invention achieves the synergistic recovery and high-value utilization of lithium, rubidium, silicon, aluminum, and iron elements in lithium slag, shortening the reaction time, reducing energy consumption and raw material costs, and obtaining a high-value-added ZSM-5 molecular sieve.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and material preparation, specifically to a method for separating valuable metals from lithium slag using microwave activation and for resource reuse. Background Technology

[0002] With the rapid development of new energy and energy storage, the demand for lithium resources is constantly increasing. This leads to the generation of large amounts of waste tailings and leaching residues during lithium mining and lithium salt production. Lithium slag is mainly composed of aluminosilicate minerals, and also contains calcium sulfate, iron oxides, and rare and dispersed metal elements such as lithium and rubidium.

[0003] Currently, only a small amount of lithium slag is used in the preparation of building materials such as cement, concrete, and ceramics. A large amount of lithium slag is still disposed of through stockpiling and landfilling. However, this method not only wastes a significant amount of resources, but long-term stockpiling also causes the leaching of heavy metals and soluble salts, resulting in environmental pollution. Therefore, developing a technological solution that can effectively convert these components is crucial for promoting the high-value utilization of lithium slag and achieving efficient treatment of lithium slag.

[0004] ZSM-5 molecular sieves, as a typical aluminosilicate catalyst, are widely used in petrochemical processes such as catalytic cracking, alkylation, and isomerization due to their regular pore structure, tunable acidity, and excellent thermal / hydrothermal stability. However, traditional methods for preparing ZSM-5 molecular sieves typically rely on high-purity silicon, aluminum, and rare metal salts, resulting in high raw material costs. Therefore, exploring the application of lithium slag in the preparation of ZSM-5 molecular sieves is a worthwhile area of ​​research. Summary of the Invention

[0005] This invention aims to provide a method for separating valuable metals from lithium slag through microwave activation and for resource reuse, thereby realizing the resource-based treatment of lithium slag, converting it into high-value ZSM-5 molecular sieves, reducing the cost of molecular sieve preparation, and improving the efficiency of molecular sieve synthesis.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for microwave-activated separation and resource recycling of valuable metals from lithium slag, comprising the following steps: Step S1. Microwave irradiation is applied to the lithium slag to dehydrate, crush, and dissociate it, resulting in dry lithium slag with a high degree of dissociation. Step S2. The dried lithium slag is subjected to ultrasonic acid leaching treatment to enrich lithium, rubidium, and iron; Step S3. After enrichment, the pH of the acid leaching solution is adjusted to convert the iron element into sodium ferric sulfate crystals, and the acid leaching solution is separated and purified. Step S4. Mix the acid leaching residue with alkali and perform microwave alkali fusion activation; Step S5. Extract silicon and aluminum elements by ultrasonic water leaching. Mix the silicon and aluminum-containing leachate with silicon source, template agent and sodium ferrous sulfate crystals from step S3 to obtain the precursor. Step S6. The precursor is subjected to microwave hydrothermal synthesis, oxidative calcination and ion exchange to obtain iron-modified ZSM-5 molecular sieve.

[0007] Secondly, the present invention provides a method for microwave-activated separation and resource recycling of valuable metals from lithium slag, comprising the following steps: Step S1. Weigh a certain mass of lithium slag and microwave it for 10-40 minutes at a microwave power of 30-80 g / kW to obtain dry lithium slag with high degree of dissociation. Step S2. Add a certain concentration of acid solution to the high dissociation degree dry lithium slag obtained in step S1, and perform ultrasonic acid leaching treatment. After leaching, the liquid and solid are separated to obtain acid leaching solution and acid leaching slag. Step S3. Add an alkaline solution to the acid leaching solution enriched with lithium, rubidium, and iron obtained in step S2 to adjust the pH, so that the iron element is converted into yellow sodium iron alum crystal precipitate. After centrifugation, yellow sodium iron alum crystal and lithium and rubidium mother liquor are obtained. Step S4. After washing and drying the acid leaching residue obtained in step S3, add alkali and mix evenly by ball milling. Then, perform alkali melting treatment in a microwave atmosphere furnace under a protective atmosphere to rapidly activate and heat the residue, so that the silicon and aluminum elements in the lithium residue are converted into soluble salts. Step S5. Take out the material after the reaction in step S4, add deionized water, and perform ultrasonic water immersion treatment. Separate the liquid and solid to obtain leachate and water immersion residue. Take a certain amount of leachate, add silicon source, template agent and sodium ferrous sulfate crystals from step S3, and stir at room temperature to obtain the precursor. Step S6. The precursor obtained in step S5 is subjected to hydrothermal synthesis in a microwave digester. After the hydrothermal product is filtered, washed and dried, it is oxidized and calcined to remove the template agent, and then ion exchange is performed to obtain iron-modified ZSM-5 molecular sieve.

[0008] As a preferred option, in step S2, during ultrasonic acid leaching, the sulfuric acid concentration is 10~30wt.%, the liquid-solid ratio is 4~6:1, the leaching time is 30~90min, the leaching temperature is 50~80℃, the ultrasonic frequency is 40KHz, and the ultrasonic power is 175-185W.

[0009] As a preferred embodiment, in step S2, an appropriate amount of acid solution is added to the acid leaching solution and returned for subsequent batches of lithium slag leaching. The acid leaching is repeated multiple times. The concentration of the sulfuric acid solution added during the repeated acid leaching is 20~30wt.%, and the amount of sulfuric acid solution added is used to maintain the overall liquid-solid ratio of the repeated acid leaching system at (4~6):1. The number of cycles is 8~15 times.

[0010] As a preferred embodiment, in step S3, sodium hydroxide solution with a concentration of 5-15 wt.% is used to adjust the pH, and it is slowly added dropwise under strong stirring until the pH is 1.5-3.

[0011] As a preferred embodiment, in step S4, the added alkali is sodium hydroxide, the mass ratio of dried acid leaching residue to sodium hydroxide is (3~7):1, the ball milling time is 60~180min, the rotation speed is 200~350rpm, the temperature during the microwave alkali melting process is 300~500℃, the heating rate is 40-60℃ / min, the holding time is 30~90min, the microwave heating power is 800~4000W, the microwave frequency is 2450±50 or 915±50MHz, and the protective atmosphere is argon or nitrogen.

[0012] As a preferred embodiment, in step S5, the liquid-to-solid ratio of ultrasonic water immersion is (8~12):1, the immersion temperature is 40~80℃, the immersion time is 40~80min, the ultrasonic frequency is 40KHz, the ultrasonic power is 175-185W, the molar ratio of silicon source to template agent is 1~2:1, and the amount of sodium ferrous sulfate crystals is 0.05~0.2g / ml.

[0013] As a preferred option, in step S5, the silicon source is one of tetraethyl orthosilicate, silica gel, sodium silicate, or fumed silica, and the template agent is one of tetrapropylammonium hydroxide or tetrapropylammonium bromide.

[0014] As a preferred embodiment, in step S6, the microwave hydrothermal synthesis temperature is 150-180℃, the holding time is 1-4 hours, the microwave power is 500-2000W, the oxidation calcination temperature is 400-600℃, and the holding time is 2-6 hours; the ion exchange uses a 1-1.5 mol / L NH4NO3 or NH4Cl solution as the exchanger, the liquid-to-solid ratio during the ion exchange process is (15-25):1, the exchange temperature is 70-80℃, and the exchange time is 3-5 hours. (This has been added in subsequent embodiments.) Thirdly, the present invention provides a ZSM-5 molecular sieve, which is obtained by the above-described method. Attached Figure Description

[0015] Figure 1 This is a process flow diagram of one specific embodiment of the present invention; Figure 2 The X-ray powder diffraction spectrum of the lithium slag used in Example 1 of this invention is shown below. Figure 3 The X-ray powder diffraction spectra of lithium slag after microwave irradiation in Examples 1 and 2 of this invention are shown below. Figure 4 This is a particle size distribution diagram of lithium slag before and after microwave irradiation in Example 1 of the present invention; Figure 5 The leaching rates of lithium, rubidium, and iron during the ultrasonic acid leaching process of lithium slag in Examples 1 and 2 of this invention; Figure 6 This is the X-ray powder diffraction spectrum of the Fe@ZSM-5 molecular sieve in Example 1 of this invention; Figure 7 This is a scanning electron microscope image of the Fe@ZSM-5 molecular sieve in Example 1 of the invention; Figure 8 This is an EDS elemental distribution diagram of the Fe@ZSM-5 molecular sieve in Example 1 of the invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased.

[0017] Unless otherwise stated, all percentages in this invention represent mass fractions. Ratios are mass percentages, and concentrations are mass concentrations.

[0018] Unless otherwise specified, all materials, instruments, and equipment used below are conventional materials, instruments, and equipment or obtained through commercial channels; all testing methods used are existing methods unless otherwise specified.

[0019] In existing technologies, the raw material cost for ZSM-5 molecular sieve preparation is relatively high. Furthermore, the traditional hydrothermal synthesis process requires 1-3 days, resulting in low synthesis efficiency and uneven distribution of temperature, concentration, and mass field. If high-value lithium and rubidium elements can be preferentially extracted from lithium slag, while simultaneously converting its abundant silicon and aluminum into a ZSM-5 molecular sieve framework, and concurrently loading iron into the ZSM-5 molecular sieve, not only can the production cost of ZSM-5 molecular sieves be reduced, but also the full-scale, high-value utilization and environmentally friendly treatment of lithium slag can be achieved, aligning with the concepts of green chemistry and sustainable development.

[0020] Furthermore, in a first aspect, embodiments of the present invention provide a method for the separation and resource reuse of valuable metals from lithium slag via microwave activation, comprising the following steps: Step S1. Microwave irradiation is applied to the lithium slag to dehydrate, crush, and dissociate it, resulting in dry lithium slag with a high degree of dissociation. Step S2. The dried lithium slag is subjected to ultrasonic acid leaching treatment to enrich lithium, rubidium, and iron; Step S3. After enrichment, the pH of the acid leaching solution is adjusted to convert the iron element into sodium ferric sulfate crystals, and the acid leaching solution is separated and purified. Step S4. Mix the acid leaching residue with alkali and perform microwave alkali fusion activation; Step S5. Extract silicon and aluminum elements by ultrasonic water leaching. Mix the silicon and aluminum-containing leachate with silicon source, template agent, and sodium ferrous sulfate crystals from step S3 to obtain the precursor. Step S6. The precursor is subjected to microwave hydrothermal synthesis, oxidative calcination, and ion exchange to obtain iron-modified ZSM-5 molecular sieve. This invention uses a large amount of waste tailings and leaching residue from lithium salt production as raw materials, and transforms the silicon, aluminum and iron elements therein into high-value-added ZSM-5 molecular sieves and functional modified components, providing an innovative approach to solving the resource utilization problem of similar silicon-aluminum waste residues.

[0021] This invention achieves the enrichment of lithium, rubidium, and iron through ultrasonic acid leaching. The pH is adjusted to precipitate iron in the form of sodium ferric sulfate crystals, thus purifying the acid leaching solution. It can also be used as a modified metal precursor for the synthesis of ZSM-5 molecular sieves.

[0022] This invention utilizes silicon, aluminum, and iron elements in lithium slag to reduce the amount of silicon source, aluminum source, and rare metal salt used in the molecular sieve synthesis process, and realizes in-situ modification of ZSM-5 molecular sieve with iron elements in lithium slag, which significantly reduces the raw material cost of molecular sieve from the source.

[0023] This invention introduces microwaves and ultrasound into the reaction process, enhancing heat and mass transfer efficiency during irradiation, leaching, alkali fusion, and hydrothermal synthesis. This shortens reaction time, improves production efficiency, and facilitates the production of molecular sieves with uniform crystallinity and stable performance. It also reduces energy consumption and raw material costs, achieving the synergistic recovery and high-value utilization of lithium, rubidium, silicon, aluminum, and iron elements in lithium slag, providing an innovative solution for the resource utilization of lithium slag.

[0024] In step S1, the lithium slag can be industrial silicon-aluminum waste residue such as waste tailings and leaching residue generated during the production of lithium salts from lithium ore.

[0025] Secondly, embodiments of the present invention provide a method for microwave-activated separation and resource reuse of valuable metals from lithium slag, comprising the following steps: Step S1. Weigh a certain mass of lithium slag and microwave it for 10-40 minutes at a microwave power of 30-80 g / kW to obtain dry lithium slag with high degree of dissociation. Step S2. Add a certain concentration of acid solution to the high dissociation degree dry lithium slag obtained in step S1, and perform ultrasonic acid leaching treatment. After leaching, the liquid and solid are separated to obtain acid leaching solution and acid leaching slag. Step S3. Add an alkaline solution to the acid leaching solution enriched with lithium, rubidium, and iron obtained in step S2 to adjust the pH, so that the iron element is converted into yellow sodium iron alum crystal precipitate. After centrifugation, yellow sodium iron alum crystal and lithium and rubidium mother liquor are obtained. The acid leaching solution can be purified and the iron element can be enriched and recovered by adjusting the pH. Step S4. After washing and drying the acid leaching residue obtained in step S3, add alkali and mix evenly by ball milling. Then, perform alkali fusion treatment in a microwave atmosphere furnace under a protective atmosphere. Use microwave to quickly activate and heat the residue, so that the silicon and aluminum elements in the lithium residue are converted into soluble salts. Step S5. Take out the material after the reaction in step S4, add deionized water, and perform ultrasonic water immersion treatment. Separate the liquid and solid to obtain leachate and water immersion residue. Take a certain amount of leachate, add silicon source, template agent and sodium ferrous sulfate crystals from step S3, and stir at room temperature to obtain the precursor. Step S6. The precursor obtained in step S5 is subjected to hydrothermal synthesis in a microwave digester. After the hydrothermal product is filtered, washed and dried, it is oxidized and calcined to remove the template agent, and then ion exchange is performed to obtain iron-modified ZSM-5 molecular sieve.

[0026] In step S6, the precursor can be placed in a polytetrafluoroethylene container and hydrothermally synthesized in a microwave digester. The hydrothermal product is then filtered, washed, dried, and placed in a muffle furnace for oxidative calcination.

[0027] The reaction mechanism of this invention is as follows: Microwave irradiation H₂O(l) = H₂O(g) CaSO4·2H2O = CaSO4 + 2H2O Microwave alkaline melting SiO2 + 2OH - = SiO3 2- + H2O Al₂O₃ + 2OH⁻ - +3H₂O =2Al(OH)₄ 2- First, a certain mass of lithium slag is weighed out. The free water and crystal water in the lithium slag are removed by microwave irradiation. The process of water vapor escape increases the cracks and pores on the surface of the lithium slag mineral phase, which in turn causes it to dissociate and break, exposing more lithium, rubidium and iron minerals.

[0028] Then, the lithium, rubidium, and iron minerals in the lithium slag are converted into sulfates by ultrasonic acid leaching. The cavitation effect of ultrasound can strongly scour the surface of mineral phase particles, further enlarging the cracks generated during microwave irradiation and producing more fine particles, which is conducive to the leaching of lithium, rubidium, and iron elements.

[0029] Slowly adding an alkaline solution (such as sodium hydroxide solution) to the acid leaching solution causes the iron ions in the solution to react with sodium ions and sulfate ions to form yellow sodium alum crystal precipitate, thus purifying the acid leaching solution and collecting iron elements.

[0030] A certain amount of alkali (such as sodium hydroxide) is added to the acid leaching residue. Microwave alkali melting is performed at a low temperature to allow the SiO2 and Al2O3 in the lithium residue to react with the added NaOH, converting silicon and aluminum elements into soluble salts. Ultrasonic water leaching treatment can dissolve the soluble salts formed during the microwave alkali melting process, resulting in a leachate containing silicon and aluminum ions.

[0031] Adding a silicon source to the leachate to increase the silicon-aluminum ratio ensures good crystallinity of the molecular sieve. Adding a template agent induces the formation of the unique structure of ZSM-5 molecular sieve. Adding sodium ferric sulfate crystals achieves in-situ modification of ZSM-5 molecular sieve.

[0032] The microwave electromagnetic field during hydrothermal synthesis accelerates heat and mass transfer, shortens the synthesis time of molecular sieves, and improves synthesis efficiency. Oxidative calcination removes the template agent and converts iron into oxides.

[0033] In one implementation method, during ultrasonic acid leaching in step S2, the sulfuric acid concentration is 10-30 wt.%, the liquid-to-solid ratio is 4-6:1, the leaching time is 30-90 min, the leaching temperature is 50-80℃, the ultrasonic frequency is 40 kHz, and the ultrasonic power is 175-185 W. By utilizing the cavitation effect and physical scouring force of ultrasound, the cracks generated during microwave irradiation are further enlarged, producing more fine particles and enhancing the leaching efficiency of sulfuric acid on the microwave-pretreated lithium slag.

[0034] In one implementation method, in step S2, an appropriate amount of acid solution is added to the acid leaching solution and returned for subsequent batches of lithium slag leaching. Through multiple cycles of acid leaching, the amount of acid used is reduced and lithium, rubidium, and iron are enriched. The concentration of sulfuric acid solution added during the cycle of acid leaching is 20~30 wt.%, and the amount of sulfuric acid solution added is used to maintain the overall liquid-solid ratio of the cycle of acid leaching system at (4~6):1. The number of cycles is 8~15 times.

[0035] This invention achieves the enrichment of lithium, rubidium, and iron by reducing the amount of acid used through multiple cyclic acid leaching. The pH is adjusted to precipitate iron in the form of sodium ferric sulfate crystals, thus purifying the acid leaching solution. It can also be used as a modified metal precursor for the synthesis of ZSM-5 molecular sieves.

[0036] In one embodiment, in step S3, a sodium hydroxide solution with a concentration of 5-15 wt.% is used to adjust the pH, and it is slowly added dropwise under strong stirring until the pH reaches 1.5-3. The above-mentioned concentration and pH range further allow the iron ions in the solution to react with sodium ions and sulfate ions to form a precipitate of jaundice iron alum crystals.

[0037] In one embodiment, in step S4, the added alkali is sodium hydroxide, the mass ratio of dried acid leaching residue to sodium hydroxide is (3~7):1, the ball milling time is 60~180min, the rotation speed is 200~350rpm, the temperature during the microwave alkali melting process is 300~500℃, the heating rate is 40-60℃ / min, the holding time is 30~90min, the microwave heating power is 800~4000W, the microwave frequency is 2450±50 or 915±50MHz, and the protective atmosphere is argon or nitrogen.

[0038] Acid cycling reduces reagent consumption and enriches lithium, rubidium, and iron in the leachate; fine pH adjustment purifies the leachate and separates iron; microwave alkali fusion lowers the reaction temperature and shortens the reaction time, which helps reduce energy consumption in the process.

[0039] In one implementation method, in step S5, the liquid-to-solid ratio of ultrasonic water leaching is (8~12):1, the leaching temperature is 40~80℃, the leaching time is 40~80min, the ultrasonic frequency is 40KHz, the ultrasonic power is 175-185W, the molar ratio of silicon source to template agent is 1~2:1, and the amount of sodium ferric sulfate crystals is 0.05~0.2g / ml. Through ultrasonic water leaching, the solid aluminosilicates generated by microwave alkaline melting are efficiently transferred to the liquid phase; by precisely controlling the ratio of silicon source to template agent, the aluminosilicates from lithium slag are formulated into the precursor ratio required for ZSM-5; and the sodium ferric sulfate crystals generated during iron removal are quantitatively added as a molecular sieve loading element, which not only achieves high-value utilization of iron but also helps improve the performance of the molecular sieve.

[0040] In one embodiment, in step S5, the silicon source is one of tetraethyl orthosilicate, silica gel, sodium silicate, or fumed silica, and the template agent is one of tetrapropylammonium hydroxide or tetrapropylammonium bromide.

[0041] The leachate obtained after ultrasonic water immersion contains dissolved silicon, aluminum, and some residual sodium. One of tetraethyl orthosilicate, silica gel, sodium silicate, and fumed silica is selected to adapt to this complex system and mix uniformly with the original silicon and aluminum components in the leachate to meet the nucleation and growth requirements of ZSM-5 molecular sieve. Tetrapropylammonium hydroxide and tetrapropylammonium bromide are the most classic and effective template agents for the synthesis of ZSM-5. Their molecular size and spatial configuration are perfectly matched with the cross-channel system of ZSM-5, and they can self-assemble to guide the silicon-aluminum-oxygen tetrahedra to arrange around them to form crystals with MFI topology.

[0042] In one implementation method, in step S6, the microwave hydrothermal synthesis temperature is 150-180℃, the holding time is 1-4 hours, the microwave power is 500-2000W, the oxidation calcination temperature is 400-600℃, and the holding time is 2-6 hours. Ion exchange uses a 1-1.5 mol / L NH4NO3 or NH4Cl solution as the exchanger, the liquid-to-solid ratio is (15-25):1, the exchange temperature is 70-80℃, and the exchange time is 3-5 hours. Microwave hydrothermal synthesis shortens the traditional crystallization time from several days to several hours; oxidation calcination removes the template agent from the molecular sieve and converts iron into oxides, yielding iron-modified ZSM-5 molecular sieve. Through ion exchange, Na-ZSM-5 is converted into highly active, acid-site-exposed H-ZSM-5, and in this process, the iron active centers are purified and stabilized, which is beneficial to improving the catalytic activity of the molecular sieve.

[0043] Thirdly, embodiments of the present invention also provide a ZSM-5 molecular sieve, obtained by the above-described method. Compared to existing ZSM-5 molecular sieve products, the ZSM-5 molecular sieve of the present invention exhibits improved performance.

[0044] To further illustrate the present invention, the following describes in detail, with reference to embodiments, a method for separating valuable metals from lithium slag using microwave activation and for resource reuse.

[0045] The devices / apparatus used in the embodiments are as follows: Microwave irradiation: Microwave high-temperature muffle furnace (HAMiLab-WG10, Changsha Longtai Microwave Thermal Engineering Co., Ltd.) Ultrasonic acid immersion / water immersion: Ultrasonic cleaning machine (LM030SD, Extreme Pulse Ultrasonic Technology Co., Ltd.) Ball mill: Planetary ball mill (SFM-1, Hefei Kejing Materials Technology Co., Ltd.) Microwave Alkali Melting: Microwave Reaction-Sintering Equipment (HY-QS6016, Hunan Huaye Microwave Technology Co., Ltd.) Microwave hydrothermal synthesis: Microwave digestion system (MWD 620, Shanghai Yuanxi Instrument Co., Ltd.) Example 1 like Figure 1 As shown in this embodiment, the method for separating valuable metals from lithium slag using microwave activation and for resource recycling includes the following steps: Step S1. Weigh 50g of lithium leaching residue and microwave it for 20min at a microwave power of 50g / kW to obtain dry lithium residue with high degree of dissociation.

[0046] Step S2. Weigh 10g of the high-dissociation-degree dried lithium slag from step S1, add 40g of 20wt.% sulfuric acid solution, and perform ultrasonic acid leaching treatment. The leaching temperature is 70℃, the leaching time is 60min, the ultrasonic frequency is 40KHz, and the ultrasonic power is 180W. After leaching, the liquid and solid are separated to obtain iron and rubidium leaching solution and acid leaching residue. The acid leaching solution is replenished with 25wt.% sulfuric acid solution until the liquid-solid ratio is 4:1. Continue to leach a new batch of lithium slag. Repeat this cycle 8 times to reduce the amount of acid used and achieve the enrichment of lithium, rubidium, and iron.

[0047] Step S3. Add 10 wt.% sodium hydroxide solution to the acid leaching solution enriched with lithium, rubidium, and iron obtained in step S2 to adjust the pH to 2, so that the iron element is converted into yellow sodium iron alum crystal precipitate. After centrifugation, yellow sodium iron alum crystal and lithium and rubidium mother liquor are obtained. The acid leaching solution can be purified by adjusting the pH and the iron element can be enriched and recovered.

[0048] The subsequent industrial processing of lithium and rubidium mother liquor can be: 1. Rubidium Extraction - Through cascade extraction, washing and back-extraction processes, a pure rubidium-rich solution can be obtained. The enriched solution is then evaporated and crystallized to produce high-value-added rubidium sulfate products. 2. Lithium Extraction - The "rubidium extract residue" after rubidium extraction is concentrated through multi-stage evaporation to achieve a lithium concentration of over 5 g / L. Then, a saturated sodium carbonate solution is added, causing lithium to precipitate as lithium carbonate.

[0049] Step S4. Take 12g of washed and dried acid leaching residue, add 4g of sodium hydroxide solid, and ball mill at 250rpm for 90min to mix evenly. Place the mixture in a silicon carbide crucible and perform alkaline fusion treatment in a microwave atmosphere furnace under an argon protective atmosphere. The reaction temperature is 400℃, the heating rate is 45℃ / min, and the holding time is 60min. The microwave heating power is 2000W, of which the heating section is 2000W, and the power of the holding section will be automatically adjusted according to the temperature. The microwave frequency is 2450MHz.

[0050] Step S5. Take out the material after the reaction in step S4, add 130g of deionized water, and perform ultrasonic water leaching treatment. The leaching temperature is 70℃, the leaching time is 60min, the ultrasonic frequency is 40KHz, and the ultrasonic power is 180W. After liquid-solid separation, take 20ml of the leaching solution, add tetraethyl orthosilicate, tetrapropylammonium hydroxide, and sodium ferrous sulfate crystals. The molar ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide is 1.5:1, and the amount of sodium ferrous sulfate crystals is 0.1 g / ml. Stir at room temperature for 2 hours to obtain the precursor.

[0051] Step S6. The precursor obtained in step S5 is placed in a polytetrafluoroethylene container and hydrothermally synthesized in a microwave digester at a temperature of 170°C for 2 hours. The microwave power is 1500W, with the heating section at 1500W and the holding section power automatically adjusted according to the temperature. After filtration, washing, and drying, the product is placed in a muffle furnace for oxidative calcination to remove the template agent. The oxidative calcination temperature is 500°C for 4 hours. Ion exchange is performed using a 1.3 mol / L NH4NO3 solution as the exchanger, with a liquid-to-solid ratio of 20:1, an exchange temperature of 70°C, and an exchange time of 4 hours. Iron-modified ZSM-5 molecular sieve is obtained and named Fe@ZSM-5.

[0052] The chemical composition of the lithium slag used in this embodiment is shown in Table 1: Table 1. Chemical composition (wt.%) of lithium leaching residue used in this embodiment. The lithium slag X-ray powder diffraction spectrum and chemical composition used in this embodiment are as follows: Figure 2 As shown in Table 1, the lithium slag mainly consists of complex mineral phases and contains a large amount of water, CaSO4·2H2O, Si, and Al elements, as well as small amounts of Li, Rb, and Fe elements.

[0053] Example 2 The method for separating valuable metals from lithium slag using microwave activation and for resource recycling in this embodiment includes the following steps: Step S1. Weigh 50g of lithium leaching residue and microwave it for 30min at a microwave power of 60g / kW to obtain dry lithium residue with high degree of dissociation.

[0054] Step S2. Weigh 10g of the high-dissociation-degree dried lithium slag from step S1, add 40g of 20wt.% sulfuric acid solution, and perform ultrasonic acid leaching treatment. The leaching temperature is 70℃, the leaching time is 60min, the ultrasonic frequency is 40KHz, and the ultrasonic power is 180W. After leaching, the liquid and solid are separated to obtain iron and rubidium leaching solution and acid leaching residue. The acid leaching solution is replenished with 25wt.% sulfuric acid solution until the liquid-solid ratio is 4:1. Continue to leach a new batch of lithium slag. Repeat this cycle 8 times to reduce the amount of acid used and achieve the enrichment of lithium, rubidium, and iron.

[0055] Step S3. Add 10 wt.% sodium hydroxide solution to the acid leaching solution enriched with lithium, rubidium, and iron obtained in step S2 to adjust the pH to 2, so that the iron element is converted into yellow sodium iron alum crystal precipitate. After centrifugation, yellow sodium iron alum crystal and lithium and rubidium mother liquor are obtained. The acid leaching solution can be purified by adjusting the pH and the iron element can be enriched and recovered.

[0056] Step S4. Take 12g of washed and dried acid leaching residue, add 4g of sodium hydroxide, and ball mill at 250rpm for 90min to mix evenly. Place the mixture in a silicon carbide crucible and perform alkaline fusion treatment in a microwave atmosphere furnace under an argon protective atmosphere. The reaction temperature is 400℃, the heating rate is 45℃ / min, and the holding time is 60min. The microwave heating power is 2000W, of which the heating section is 2000W, and the power of the holding section will be automatically adjusted according to the temperature. The microwave frequency is 2450MHz.

[0057] Step S5. Take out the material after the reaction in step S4, add 130g of deionized water, and perform ultrasonic water leaching treatment. The leaching temperature is 70℃, the leaching time is 60min, the ultrasonic frequency is 40KHz, and the ultrasonic power is 180W. After liquid-solid separation, take 20ml of the leaching solution, add tetraethyl orthosilicate, tetrapropylammonium hydroxide, and sodium ferrous sulfate crystals. The molar ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide is 1.5:1, and the amount of sodium ferrous sulfate crystals is 0.1 g / ml. Stir at room temperature for 2 hours to obtain the precursor.

[0058] Step S6. The precursor obtained in step S5 is placed in a polytetrafluoroethylene (PTFE) container and subjected to hydrothermal synthesis in a microwave digester at a temperature of 170°C for 2 hours. The microwave power is 1500W, with the heating stage at 1500W and the holding stage power automatically adjusted according to the temperature. After filtration, washing, and drying, the product is placed in a muffle furnace for oxidative calcination to remove the template agent. The oxidative calcination temperature is 500°C for 4 hours. Ion exchange is performed using a 1.3 mol / L NH4NO3 solution as the exchanger, with a liquid-to-solid ratio of 20:1, an exchange temperature of 70°C, and an exchange time of 4 hours, yielding an iron-modified ZSM-5 molecular sieve named Fe@ZSM-5. The lithium slag used in this example is the same as in Example 1.

[0059] Example 3 The method for separating valuable metals from lithium slag using microwave activation and for resource recycling in this embodiment includes the following steps: Step S1. Weigh 50g of lithium leaching residue and microwave it for 30min at a microwave power of 60g / kW to obtain dry lithium residue with high degree of dissociation.

[0060] Step S2. Weigh 10g of the high-dissociation-degree dried lithium slag from step S1, add 40g of 20wt.% sulfuric acid solution, and perform ultrasonic acid leaching treatment. The leaching temperature is 70℃, the leaching time is 60min, the ultrasonic frequency is 40KHz, and the ultrasonic power is 180W. After leaching, the liquid and solid are separated to obtain iron and rubidium leaching solution and acid leaching residue. The acid leaching solution is replenished with 25wt.% sulfuric acid solution until the liquid-solid ratio is 4:1. Continue to leach a new batch of lithium slag. Repeat this cycle 8 times to reduce the amount of acid used and achieve the enrichment of lithium, rubidium, and iron.

[0061] Step S3. Add 10 wt.% sodium hydroxide solution to the acid leaching solution enriched with lithium, rubidium, and iron obtained in step S2 to adjust the pH to 2, so that the iron element is converted into yellow sodium iron alum crystal precipitate. After centrifugation, yellow sodium iron alum crystal and lithium and rubidium mother liquor are obtained. The acid leaching solution can be purified by adjusting the pH and the iron element can be enriched and recovered.

[0062] Step S4. Take 12g of washed and dried acid leaching residue, add 3g of sodium hydroxide solid, and ball mill at 250rpm for 90 min to mix evenly. Place the mixture in a silicon carbide crucible and perform alkaline fusion treatment in a microwave atmosphere furnace under an argon protective atmosphere. The reaction temperature is 400℃, the heating rate is 45℃ / min, and the holding time is 60min. The microwave heating power is 2000W, of which the heating section is 2000W, and the power of the holding section will be automatically adjusted according to the temperature. The microwave frequency is 2450MHz.

[0063] Step S5. Take out the material after the reaction in step S4, add 130g of deionized water, and perform ultrasonic water leaching treatment. The leaching temperature is 70℃, the leaching time is 60min, the ultrasonic frequency is 40KHz, and the ultrasonic power is 180W. After liquid-solid separation, take 20ml of the leaching solution, add tetraethyl orthosilicate, tetrapropylammonium hydroxide, and sodium ferrous sulfate crystals. The molar ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide is 1.5:1, and the amount of sodium ferrous sulfate crystals is 0.1g / ml. Stir at room temperature for 2 hours to obtain the precursor.

[0064] Step S6. The precursor obtained in step S5 is placed in a polytetrafluoroethylene (PTFE) container and subjected to hydrothermal synthesis in a microwave digester at a temperature of 170°C for 2 hours. The microwave power is 1500W, with the heating stage at 1500W and the holding stage power automatically adjusted according to the temperature. After filtration, washing, and drying, the product is placed in a muffle furnace for oxidative calcination to remove the template agent. The oxidative calcination temperature is 500°C for 4 hours. Ion exchange is performed using a 1.3 mol / L NH4NO3 solution as the exchanger, with a liquid-to-solid ratio of 20:1, an exchange temperature of 70°C, and an exchange time of 4 hours, yielding an iron-modified ZSM-5 molecular sieve named Fe@ZSM-5. The lithium slag used in this example is the same as in Example 1.

[0065] Example 4 The method for separating valuable metals from lithium slag using microwave activation and for resource recycling in this embodiment includes the following steps: Step S1. Weigh 50g of lithium tailings slag and microwave irradiate it for 20min at a microwave power of 50g / kW to obtain dry lithium slag with high degree of dissociation.

[0066] Step S2. Weigh 10g of the high-dissociation-degree dried lithium slag from step S1, add 40g of 20wt.% sulfuric acid solution, and perform ultrasonic acid leaching treatment. The leaching temperature is 70℃, the leaching time is 60min, the ultrasonic frequency is 40KHz, and the ultrasonic power is 180W. After leaching, the liquid and solid are separated to obtain iron and rubidium leaching solution and acid leaching residue. The acid leaching solution is replenished with 25wt.% sulfuric acid solution until the liquid-solid ratio is 4:1. Continue to leach a new batch of lithium slag. Repeat this cycle 8 times to reduce the amount of acid used and achieve the enrichment of lithium, rubidium, and iron.

[0067] Step S3. Add 10 wt.% sodium hydroxide solution to the acid leaching solution enriched with lithium, rubidium, and iron obtained in step S2 to adjust the pH to 2, so that the iron element is converted into yellow sodium iron alum crystal precipitate. After centrifugation, yellow sodium iron alum crystal and lithium and rubidium mother liquor are obtained. The acid leaching solution can be purified by adjusting the pH and the iron element can be enriched and recovered.

[0068] Step S4. Take 12g of washed and dried acid leaching residue, add 4g of sodium hydroxide solid, and ball mill at 250rpm for 90 min to mix evenly. Place the mixture in a silicon carbide crucible and perform alkaline fusion treatment in a microwave atmosphere furnace under an argon protective atmosphere. The reaction temperature is 400℃, the heating rate is 45℃ / min, and the holding time is 60min. The microwave heating power is 2000W, of which the heating section is 2000W, and the power of the holding section will be automatically adjusted according to the temperature. The microwave frequency is 2450MHz.

[0069] Step S5. Take out the material after the reaction in step S4, add 130g of deionized water, and perform ultrasonic water leaching treatment. The leaching temperature is 70℃, the leaching time is 60min, the ultrasonic frequency is 40KHz, and the ultrasonic power is 180W. After liquid-solid separation, take 20ml of the leaching solution, add tetraethyl orthosilicate, tetrapropylammonium hydroxide, and sodium ferrous sulfate crystals. The molar ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide is 1.5:1, and the amount of sodium ferrous sulfate crystals is 0.1 g / ml. Stir at room temperature for 2 hours to obtain the precursor. Step S6. The precursor obtained in step S5 is placed in a polytetrafluoroethylene container and hydrothermally synthesized in a microwave digester at a temperature of 170°C for 2 hours. The microwave power is 1500W, with the heating section at 1500W and the holding section power automatically adjusted according to the temperature. After filtration, washing, and drying, the product is placed in a muffle furnace for oxidative calcination to remove the template agent. The oxidative calcination temperature is 500°C for 4 hours. Ion exchange is performed using a 1.3 mol / L NH4NO3 solution as the exchanger, with a liquid-to-solid ratio of 20:1, an exchange temperature of 70°C, and an exchange time of 4 hours. Iron-modified ZSM-5 molecular sieve is obtained and named Fe@ZSM-5.

[0070] The chemical composition of the lithium slag used in this embodiment is shown in Table 2: Table 2 Chemical composition (wt.%) of lithium tailings slag used in this embodiment Comparative Example 1 Unlike Example 1, S1 does not use microwave treatment, but is dried in a conventional drying oven at 60°C for 24 hours.

[0071] Comparative Example 2 Unlike Example 1, S2 uses conventional heating for alkali fusion treatment, with an alkali fusion temperature of 400°C, a heating rate of 10°C / min, and a holding time of 60min.

[0072] Test Instance The X-ray powder diffraction spectra and particle size distributions of lithium slag before and after microwave irradiation in Example 1 are as follows: Figure 3 , 4 As shown, after microwave irradiation of lithium slag, the amount of CaSO4·2H2O decreased significantly, and the particle size became smaller. The degree of dissociation can be observed through changes in particle size, and it is evident that the degree of dissociation is high.

[0073] like Figure 3 , 4 As shown in Figure 5, after microwave irradiation of lithium slag, the amount of CaSO4·2H2O decreased significantly. After irradiation for 30 minutes, the CaSO4·2H2O in the lithium slag disappeared completely. The leaching rates of lithium, rubidium, and iron were as follows: Figure 5 As shown in Table 3, increasing the microwave power and extending the microwave irradiation time resulted in more cracks in the lithium slag, which improved the leaching rates of lithium, rubidium, and iron during ultrasonic acid leaching.

[0074] The XRD pattern of the molecular sieve prepared in Example 1 is as follows: Figure 6 As shown, its diffraction peaks are consistent with the data in standard PDF#004-0926, indicating that the prepared Fe@ZSM-5 sample has formed a qualitative MFI structure, that is, the characteristic structure of ZSM-5 molecular sieve. Figure 7 ,8 The morphology and EDS spectrum of Fe@ZSM-5 molecular sieve are shown. Al elements are uniformly distributed on the molecular sieve, and Fe elements are also present, indicating that Al and Fe elements in lithium slag were successfully used in the synthesis of molecular sieve.

[0075] The leaching rates of lithium, rubidium, and iron during acid leaching were determined as follows: Record the mass of lithium slag and the volume of leachate used. Measure the lithium, rubidium, and iron content in the lithium slag raw material and the leachate, respectively, and calculate using the following formula: E i =(C i ×V)×100% / (m0×w i ) In the formula: E i Leaching rate of element i (lithium, rubidium, iron), %; C i Mass concentration of element i in leachate, g / L; V, volume of leachate, L; m0, mass of lithium slag, g; w i Mass fraction of element i in lithium slag raw material.

[0076] The lithium, rubidium, and iron leaching rates of the examples and comparative examples are shown in Table 3. The lithium leaching residue without microwave irradiation treatment has a lower lithium, rubidium, and iron leaching rate, indicating that microwave irradiation treatment can dissociate the lithium leaching residue, which is beneficial for the leaching of lithium, rubidium, and iron.

[0077] Table 3. Lithium, rubidium, and iron leaching rates in the examples and comparative examples. The performance of ZSM-5 molecular sieves in the examples and comparative examples is shown in Table 4: The performance testing of ZSM-5 molecular sieves was conducted as follows: The catalytic performance of the prepared catalyst was tested in an isothermal quartz tube fixed-bed reactor using methanol as raw material. The prepared molecular sieve was pressed into tablets, crushed, and then sieved. Catalyst particles with a size of 40-60 mesh were selected. 0.4 g of the sieved molecular sieve sample particles were weighed and packed into the isothermal reaction zone. The upper and lower ends of the molecular sieve fixed bed were filled with quartz sand of the same particle size to ensure stable gas flow and uniform heat distribution. Before the reaction began, it was first subjected to a nitrogen atmosphere at 450℃ (71 mL / min). -1The molecular sieve was activated for 2 hours. After the activation reaction was complete, the nitrogen valve was closed, and methanol was pumped into the reaction apparatus via a dual-plunger pump. After vaporization by the heater, it entered the reactor to begin the catalytic reaction at a temperature of 450℃. The reaction products were passed into a gas chromatograph and analyzed using an FID detector equipped with capillary columns HJ-Al2O3 / S and HJ-OV-101. The carrier gas was N2, the vaporization chamber temperature was 260℃, the detection chamber temperature was 260℃, the injection time was 1 min, and the column flow rate was 3.4 mL / min. The methanol conversion rate, olefin selectivity, and aromatic selectivity were calculated using the following formulas: Methanol conversion rate = (n CH3OH,in -n CH3OH,out )×100% / n CH3OH,in ; Aromatic selectivity = n aro ×100% / (n CH3OH,in -n CH3OH,out ); Olefin selectivity = n i ×100% / (n CH3OH,in -n CH3OH,out ); In the formula, n CH3OH,in n represents the amount of carbon atoms in the methanol entering the reactor. CH3OH,out n represents the amount of carbon atoms in the unreacted methanol that enters the reactor. aro n represents the amount of carbon atoms in the aromatic hydrocarbon product. i This represents the amount of carbon atoms in the olefin product.

[0078] The molecular sieve prepared by microwave alkaline fusion treatment achieved a methanol conversion rate of 97.45%, an olefin selectivity of 60.82%, and an aromatic selectivity of 37.23%, significantly higher than that of commercially available ZSM-5 molecular sieves. In contrast, the molecular sieve prepared by conventional alkaline fusion treatment showed a higher methanol conversion rate than commercially available ZSM-5 molecular sieves, but a significantly lower rate than that prepared by microwave alkaline fusion treatment. These results indicate that the molecular sieve prepared by microwave alkaline fusion treatment possesses superior catalytic performance.

[0079] Table 4 Catalytic performance of ZSM-5 molecular sieves in the examples and comparative examples. Although the invention has been described herein with reference to several illustrative embodiments, it should be understood that many other modifications and implementations can be devised by those skilled in the art, which will fall within the scope and spirit of the principles disclosed herein. More specifically, various modifications and improvements can be made to the components or layout of the subject matter arrangement within the scope of the disclosure, drawings, and claims. Besides modifications and improvements to the components or layout, other uses will be apparent to those skilled in the art.

Claims

1. A method for separating valuable metals from lithium slag using microwave activation and for resource recycling, characterized in that, Includes the following steps: Step S1. Microwave irradiation is applied to the lithium slag to dehydrate, crush, and dissociate it, resulting in dry lithium slag with a high degree of dissociation. Step S2. The dried lithium slag is subjected to ultrasonic acid leaching treatment to enrich lithium, rubidium, and iron; Step S3. After enrichment, the pH of the acid leaching solution is adjusted to convert the iron element into sodium ferric sulfate crystals, and the acid leaching solution is separated and purified. Step S4. Mix the acid leaching residue with alkali and perform microwave alkali fusion activation; Step S5. Extract silicon and aluminum elements by ultrasonic water leaching. Mix the silicon and aluminum-containing leachate with silicon source, template agent, and sodium ferrous sulfate crystals from step S3 to obtain the precursor. Step S6. The precursor is subjected to microwave hydrothermal synthesis, oxidative calcination and ion exchange to obtain iron-modified ZSM-5 molecular sieve.

2. A method for separating valuable metals from lithium slag using microwave activation and for resource recycling, characterized in that, Includes the following steps: Step S1. Weigh a certain mass of lithium slag and microwave it for 10-40 minutes at a microwave power of 30-80 g / kW to obtain dry lithium slag with high degree of dissociation. Step S2. Add a certain concentration of acid solution to the high dissociation degree dry lithium slag obtained in step S1, and perform ultrasonic acid leaching treatment. After leaching, separate the liquid and solid to obtain acid leaching solution and acid leaching slag. Step S3. Add an alkaline solution to the acid leaching solution enriched with lithium, rubidium, and iron obtained in step S2 to adjust the pH, so that the iron element is converted into yellow sodium iron alum crystal precipitate. After centrifugation, yellow sodium iron alum crystal and lithium and rubidium mother liquor are obtained. Step S4. After washing and drying the acid leaching residue obtained in step S3, add alkali and mix evenly by ball milling. Then, perform alkali melting treatment in a microwave atmosphere furnace under a protective atmosphere to rapidly activate and heat the residue, so that the silicon and aluminum elements in the lithium residue are converted into soluble salts. Step S5. Take out the material after the reaction in step S4, add deionized water, and perform ultrasonic water immersion treatment. Separate the liquid and solid to obtain leachate and water immersion residue. Take a certain amount of leachate, add silicon source, template agent and sodium ferrous sulfate crystals from step S3, and stir at room temperature to obtain the precursor. Step S6. The precursor obtained in step S5 is subjected to hydrothermal synthesis in a microwave digester. After the hydrothermal product is filtered, washed and dried, it is oxidized and calcined to remove the template agent, and then ion exchange is performed to obtain iron-modified ZSM-5 molecular sieve.

3. The method according to claim 1 or 2, characterized in that: In step S2, during ultrasonic acid leaching, the sulfuric acid concentration is 10~30wt.%, the liquid-solid ratio is 4~6:1, the leaching time is 30~90min, the leaching temperature is 50~80℃, the ultrasonic frequency is 40KHz, and the ultrasonic power is 175-185W.

4. The method according to claim 3, characterized in that: In step S2, an appropriate amount of acid solution is added to the acid leaching solution and returned for subsequent batches of lithium slag leaching. The acid leaching is repeated multiple times. The concentration of the sulfuric acid solution added during the acid leaching is 20~30wt.%, and the amount of sulfuric acid solution added is used to maintain the overall liquid-solid ratio of the acid leaching system at (4~6):

1. The number of cycles is 8~15.

5. The method according to claim 1 or 2, characterized in that: In step S3, sodium hydroxide solution with a concentration of 5-15 wt.% is used to adjust the pH. The solution is slowly added dropwise under strong stirring until the pH reaches 1.5-3.

6. The method according to claim 1 or 2, characterized in that: In step S4, the added alkali is sodium hydroxide, the mass ratio of dried acid leaching residue to sodium hydroxide is (3~7):1, the ball milling time is 60~180min, the rotation speed is 200~350rpm, the temperature during the microwave alkali melting process is 300~500℃, the heating rate is 40-60℃ / min, the holding time is 30~90min, the microwave heating power is 800~4000W, the microwave frequency is 2450±50 or 915±50MHz, and the protective atmosphere is argon or nitrogen.

7. The method according to claim 1 or 2, characterized in that: In step S5, the liquid-to-solid ratio of ultrasonic water immersion is (8~12):1, the immersion temperature is 40~80℃, the immersion time is 40~80min, the ultrasonic frequency is 40KHz, the ultrasonic power is 175-185W, the molar ratio of silicon source to template agent is 1~2:1, and the amount of sodium ferrous sulfate crystals is 0.05~0.2g / ml.

8. The method for preparing molecular sieves according to claim 1 or 2, characterized in that: In step S5, the silicon source is one of tetraethyl orthosilicate, silica gel, sodium silicate, or fumed silica, and the template agent is one of tetrapropylammonium hydroxide or tetrapropylammonium bromide.

9. The method according to claim 1 or 2, characterized in that: In step S6, the microwave hydrothermal synthesis temperature is 150~180℃, the holding time is 1~4 hours, the microwave power is 500~2000W, the oxidation calcination temperature is 400~600℃, and the holding time is 2~6 hours; the ion exchange uses 1~1.5mol / L NH4NO3 or NH4Cl solution as the exchanger, the liquid-solid ratio of the ion exchange process is (15~25):1, the exchange temperature is 70~80℃, and the exchange time is 3~5 hours.

10. A ZSM-5 molecular sieve, characterized in that: Obtained by the method described in any one of claims 1 to 9.

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