Method for extracting lithium from low-grade lithium ore by low-temperature high-pressure pulsed electric field activation

Abstract

The application relates to a method for activating low-grade lithium ore by low-temperature high-voltage pulse electric field to extract lithium, which comprises the following steps: grinding the low-grade lithium ore to form a slurry, and performing high-voltage pulse electric field treatment under the condition that the temperature is 25-50 DEG C; selectively leaching the treated slurry by using a composite organic acid, wherein the composite organic acid comprises citric acid, malic acid and acetic acid; after the leaching is completed, solid-liquid separation is realized, valuable metals are recovered by precipitation, and tailings are low-temperature resourceized. The application adopts the mode of low-temperature constant temperature control, high-voltage pulse electric field lattice distortion activation, hard rock lithium ore organic acid low-temperature lithium extraction, and is low-temperature, non-roasting, green, low-corrosion and high-leaching rate throughout. Meanwhile, the lithium extraction device ensures that only lattice distortion occurs in the mineral, and no thermal side reaction is generated, the citric acid-malic acid-acetic acid ternary compound leaching system can be optimized, and zero solid waste storage of tailings can be realized.

Description

Technical Field

[0001] This application relates to the fields of clean metallurgy of low-grade new energy minerals, field-enhanced mineral activation, and solid waste resource utilization. Specifically, it relates to a method for lithium extraction from low-grade lithium ore by activating it with a low-temperature, high-pressure pulsed electric field. Background Technology

[0002] With the rapid expansion of the new energy storage and power battery industries, high-grade lithium resources are becoming increasingly depleted, and low-grade lepidolite, clay lithium ore, and low-grade spodumene have become the main focus of industry development. Existing lithium extraction processes are mainly divided into three categories: high-temperature roasting, strong acid leaching, and conventional organic acid leaching, all of which have significant technical shortcomings. High-temperature roasting requires calcination at 800-1100℃, which consumes a lot of energy, causes serious equipment damage, and generates toxic waste gases such as hydrogen fluoride and sulfur dioxide during the production process, resulting in extremely high environmental costs. At the same time, high temperatures can easily cause lithium ore to sinter and become encapsulated, which in turn leads to a decrease in leaching rate.

[0003] The strong acid leaching method uses concentrated sulfuric acid and concentrated hydrochloric acid systems, which causes severe equipment corrosion, dissolution of large amounts of impurities, complex subsequent purification, and extremely high pressure for waste acid treatment, which is not in line with the development direction of green mines.

[0004] Conventional low-temperature organic acid leaching processes are green and pollution-free, but they cannot destroy the dense silicate crystal structure of lithium ore. The lithium element is tightly wrapped in the crystal lattice, resulting in extremely poor activity at room temperature and low temperature. The leaching rate is generally below 85%, making industrial mass production impossible.

[0005] In existing publicly available technologies, high-voltage pulsed electric fields are mostly used for ore crushing, pre-dissociation, and energy saving in grinding; low-voltage pulsed electric fields are mostly used for clay ion migration and desorption, and their application scope is relatively narrow.

[0006] In view of the above, this application is hereby submitted. Summary of the Invention

[0007] The primary objective of this application is to provide a method for lithium extraction from low-grade lithium ore by low-temperature high-pressure pulsed electric field activation. This method employs low-temperature constant temperature control, high-pressure pulsed electric field lattice distortion activation, and low-temperature lithium extraction from hard rock lithium ore using organic acids. The entire process is low-temperature, non-roasting, green, low-corrosion, and has a high leaching rate.

[0008] The second objective of this application is to provide a lithium extraction device that is compatible with the lithium extraction method of activating low-grade lithium ore with the above-mentioned low-temperature high-pressure pulsed electric field, ensuring that the mineral only undergoes lattice distortion and does not produce thermal side reactions. It can be optimized for the ternary compound leaching system of citric acid-malic acid-acetic acid and can achieve zero solid waste storage of tailings.

[0009] To achieve the above objectives, this application provides a method for lithium extraction from low-grade lithium ore by activation with a low-temperature, high-pressure pulsed electric field, comprising the following steps: Low-grade lithium ore is ground into a slurry and then subjected to high-voltage pulse electric field treatment at a temperature of 25-50℃. The treated slurry is selectively leached with a composite organic acid, which includes citric acid, malic acid, and acetic acid. After leaching, solid-liquid separation, precipitation and recovery of valuable metals, and low-temperature resource utilization of tailings are achieved.

[0010] To address the common technical shortcomings of existing lithium extraction processes from low-grade lepidolite, clay lithium ore, and low-grade spodumene, such as high energy consumption from high-temperature roasting, significant pollution from strong acid leaching, low leaching rate at low temperatures, difficulty in breaking the inertness of mineral lattices, and low utilization rate of solid waste, this application proposes an integrated lithium extraction method that utilizes high-voltage pulsed electric field lattice pre-activation under low-temperature constant-temperature conditions, selective leaching with low-corrosion composite organic acids, multi-metal synergistic recovery, and full resource utilization of tailings.

[0011] The core of the above-mentioned lithium extraction method lies in the use of the dielectric breakdown effect of the microsecond-level high-voltage pulse electric field under the conditions of low temperature (5-50℃) throughout the process, without roasting or high-temperature thermal phase change, to precisely destroy the dense structure of lithium silicate crystals, generate uniform microcracks and lattice distortion inside the mineral, significantly reduce the energy barrier for lithium ion extraction, and completely overcome the technical defects of insufficient mineral activity and low recovery rate in traditional low-temperature leaching.

[0012] By matching a ternary compound green leaching system of citric acid-malic acid-acetic acid, highly selective leaching of lithium is achieved, the dissolution of a large number of impurities is suppressed, and associated metals such as potassium, aluminum, rubidium, and cesium are recovered simultaneously. Finally, the tailings are completely converted into inorganic fillers for building materials through low-temperature modification, achieving low carbon, low corrosion, and zero solid waste emissions throughout the entire process.

[0013] The low-grade lithium ore in this application is one or more mixed ores of lepidolite, clay-type lithium ore, and low-grade spodumene, with a lithium content of 0.3%-1.2% in the raw ore.

[0014] Preferably, as a further feasible option, the electric field strength of the high-voltage pulse electric field treatment is 25-40 kV / cm, the pulse width is 5-15 μs, the pulse frequency is 200-400 Hz, and the high-voltage pulse electric field treatment time is 3-8 min.

[0015] Preferably, as a further feasible option, the high-voltage pulse electric field treatment temperature is 35°C, the electric field strength is 32kV / cm, the pulse width is 10μs, the pulse frequency is 300Hz, and the activation time is 5min.

[0016] The above process uses a water-cooled closed-loop constant temperature control system, which can continuously remove the pulsed instantaneous trace Joule heat, ensuring that there is no temperature rise, no thermal roasting, and no mineral thermal phase change throughout the activation process, and the system temperature fluctuation does not exceed ±2℃.

[0017] Preferably, as a further feasible option, the composite organic acid is a mixture of citric acid, malic acid and acetic acid, with a mass ratio of (1-4):(1-3):1.

[0018] Preferably, as a further feasible option, the mass ratio of citric acid, malic acid and acetic acid in the composite organic acid is 3:2:1.

[0019] Preferably, as a further feasible option, the selective leaching temperature is 60-90°C, the stirring speed is 300-500 r / min, and the leaching time is 2-4 h.

[0020] Preferably, as a further feasible option, the mass concentration of the added complex organic acid is 8%-15%.

[0021] Preferably, as a further feasible option, the slurry formed by grinding low-grade lithium ore includes a lithium ore slurry with a particle size of 200 mesh and a mass percentage content of 60-75%, and the solid-liquid ratio of the slurry is 1:(2-4).

[0022] Preferably, as a further feasible option, the method for low-temperature resource utilization of tailings includes the following steps: drying the tailings, ultra-fine grinding, and low-temperature cross-linking modification at 60-80℃.

[0023] The core mechanism of the technical solution in this application is that the high-voltage microsecond pulse electric field in the low-temperature constant temperature water environment produces a triple effect of dielectric breakdown, microcrack propagation and lattice distortion on the silicate lattice of lithium ore, breaking some of the Si-O and Al-O mineral framework bonds and significantly reducing the energy barrier for lithium ion extraction.

[0024] Pulse discharge releases energy instantaneously at the microsecond level. The energy is mainly used for lattice structure destruction, and the proportion converted into heat energy is extremely low. With the help of a water-cooled constant temperature system, heat accumulation can be completely suppressed, and the entire process can maintain a low temperature and no thermal phase change.

[0025] The activated minerals have significantly increased porosity and improved ion diffusion channels. Combined with the selective chelation effect of ternary complex organic acids, this enables ultra-high efficiency lithium leaching under low-temperature conditions.

[0026] By overcoming the bottleneck of low-temperature lithium extraction technology through external field micro-lattice modification, we can achieve efficient, low-carbon, and clean resource development and utilization of low-grade and difficult-to-process lithium ores.

[0027] The lithium extraction method described in this application is stable and has controllable parameters. The overall lithium leaching rate can reach more than 97.5%, which is more than 12% higher than the conventional low-temperature organic acid process. The energy consumption is reduced by 75% compared with the roasting process, which greatly improves the industrial performance parameters of the existing process.

[0028] Preferably, the specific process parameters for solid-liquid separation and precipitation recovery of valuable metals are as follows: stirring speed of 250 r / min throughout the process, system temperature of 40-60℃; first, adjust pH to 4.0-4.5 and react at 40℃ for 60 min to precipitate aluminum; then adjust pH to 8.0-8.5 and react at 50℃ for 90 min to precipitate potassium; finally, adjust pH to 9.0-9.5 in stages and precipitate rubidium at 55℃, and precipitate cesium at pH 10.0-10.5 and 60℃, with settling and standing times of 90 min, 120 min, and 160 min for each stage, respectively, and the excess coefficient of precipitating agent is 1.05-1.15 times.

[0029] More preferably, the temperature is controlled at 50°C, and the pH of the primary precipitation is 4.2, the secondary precipitation is 8.2, the tertiary precipitation is 9.2 for rubidium and 10.2 for cesium.

[0030] Preferably, the operation steps for low-temperature resource utilization of tailings are as follows: wet tailings are dried at 60-80℃ for 45-75 minutes until the moisture content is ≤3%; ultrafine pulverization is performed until the content of -325 mesh is ≥92%; 0.3%-0.8% silane coupling agent, 5%-10% light calcium carbonate, and 2%-4% organic acid dispersant are added based on the mass of dry tailings; constant temperature crosslinking modification is performed at 60-80℃ for 90-150 minutes with a stirring speed of 300 r / min; after cooling and sieving, all of the tailings are used to prepare inorganic fillers for building materials.

[0031] More preferably, the drying temperature is 70°C, the drying time is 60 min, the crosslinking modification is carried out at 70°C for 120 min, the amount of silane coupling agent added is 0.5%, light calcium carbonate is 7%, and dispersant is 3%.

[0032] This application also provides a lithium extraction device, which uses the above-mentioned method of activating low-grade lithium ore with a low-temperature high-pressure pulsed electric field to extract lithium. The lithium extraction device includes, in sequence, a low-temperature high-pressure pulsed electric field constant temperature activation device, an organic acid closed leaching reactor, and a complete set of units for low-temperature drying, ultrafine grinding, and cross-linking modification of lithium extraction tailings.

[0033] The existing equipment does not have an independent water-cooled constant temperature jacket. After the pulse discharge generates heat, the system heats up freely, mostly at room temperature / high temperature dissociation, and is only used for ore pre-crushing and energy saving in grinding; there is no temperature control design with 25-50℃ lock-in and temperature fluctuation ±2℃.

[0034] The low-temperature high-voltage pulsed electric field isothermal activation device in this application, through a water-cooled isothermal structure combined with a low-temperature pulsed process, ensures at the equipment level that the minerals only undergo lattice distortion and do not produce thermal side reactions, thus forming the hardware basis for the above-mentioned lithium extraction method to achieve a high leaching rate of 97.5%.

[0035] Conventional organic acid leaching kettles lack layered insulation and have a built-in multi-point temperature control sensor combination. Ordinary stirred kettles have poor stirring uniformity and low mass transfer efficiency in the chelation reaction of ternary organic acids.

[0036] The closed organic acid leaching reactor described in this application is equipped with a 300-500 r / min variable frequency stirrer and a full-range temperature control system, precisely matching the 60-90℃ organic acid leaching range. Its closed structure prevents the volatilization and loss of organic acids, and the pressure relief valve is suitable for weak acid systems operating under normal pressure. The overall equipment structure is optimized for the citric acid-malic acid-acetic acid ternary complex leaching system, completely distinguishing it from strong acid high-pressure leaching reactors and high-temperature calcining reactors.

[0037] In addition, most existing lithium slag resource utilization equipment is equipped with high-temperature calcination kilns above 600℃, and there are no integrated continuous units for low-temperature drying and low-temperature cross-linking modification at 60-80℃.

[0038] The lithium extraction tailings low-temperature drying-ultrafine pulverization-crosslinking modification unit in this application recovers the waste organic acid from the front-end leaching as a modifying dispersant, and condenses and reuses the organic acid from the drying tail gas, achieving a closed-loop circulation of reagents throughout the entire equipment line. The low-temperature modification chamber is equipped with a constant temperature jacket and low-speed stirring, suitable for the low-temperature crosslinking reaction of silane coupling agents.

[0039] The entire process flow layout and equipment series sequence of the lithium extraction unit correspond to and are compatible with the lithium extraction method in this application. It can achieve zero solid waste storage of tailings, complete ground drying, ultrafine crushing and low-temperature cross-linking modification, and convert 100% of the lithium extraction tailings into building filler, eliminate solid waste storage, and form a complete green closed-loop end-of-line unit.

[0040] Compared with the prior art, the beneficial effects of this application are as follows: 1) It overcomes the industry's inherent prejudice that low temperature inevitably leads to low leaching rate. By modifying the crystal lattice with physical external field, it activates inert lithium ore at the microscopic level and achieves an ultra-high leaching rate of over 97.5% under conditions without high temperature or strong corrosive agents.

[0041] 2) Low-temperature pulses generate no heat accumulation, ensuring stable and controllable processes. The narrow pulse width and low-frequency pulse design result in extremely low heat generation. Combined with a water-cooled closed-loop constant temperature system, the entire process is strictly controlled at a low temperature of 25-50℃, preventing high temperatures, mineral sintering, thermal decomposition, and phase change side reactions. This allows for stable and continuous industrial operation.

[0042] 3) Green and low-carbon, with no high-temperature exhaust gas or waste acid emissions throughout the process. Organic acids are degradable and recyclable, and all tailings are modified to prepare building materials and fillers, achieving zero solid waste storage.

[0043] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a schematic diagram of the lithium extraction method according to Embodiment 1 of this application; Figure 2 This is a schematic diagram of the low-temperature high-voltage pulsed electric field isothermal activation device used in the lithium extraction method of Embodiment 1 of this application. Figure 3 This is a schematic diagram of the closed organic acid leaching reactor used in the lithium extraction method of Example 1 of this application. Figure 4 This is a schematic diagram of the structure of the lithium extraction tailings low-temperature drying-ultrafine grinding-crosslinking modification complete unit used in the lithium extraction method of Embodiment 1 of this application. Figure 5 This is a comparison diagram of the leaching effect in Experiment Example 1 of this application.

[0046] icon: 1-Pulse power generator; 2-Upper high voltage electrode; 3-Lower grounding electrode; 4-Sealed slurry cavity; 5-Constant temperature control jacket; 6-Water cooling circulation inlet; 7-Slurry feed port; 8-Slurry discharge port; 9-Pulse power supply; 10-Electric field action zone; 21-Tank body base; 22-Insulated outer shell; 23-Central variable frequency stirring paddle; 24-Leachate filling port; 25-Slurry feeding port; 26-Built-in temperature sensor; 27-Temperature control heating component; 28-Bottom discharge port; 29-Pressure relief valve; 31-Drum type low temperature dryer; 32-Ultra-fine powder pulverizer; 33-Low temperature constant temperature modification reaction chamber; 34-Finished product filler silo. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0048] In the description of this application, it should be noted that the terms "inner" and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0049] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "setup" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0050] Example 1 like Figure 1 As shown, the lithium extraction method for low-grade lithium ore activated by a low-temperature, high-pressure pulsed electric field is carried out according to the following steps: S1. Raw ore pretreatment: Low-grade lithium ore (lepidolite, lithium content 1%) is crushed, screened, ground and classified to obtain a 200-mesh lithium ore slurry with a content of 70% and a solid-liquid ratio of 1:3.

[0051] S2. Low-temperature, high-voltage pulsed electric field lattice activation: The slurry is fed into a low-temperature, high-voltage pulsed electric field isothermal activation device with a water-cooled isothermal jacket. The structural diagram of this device is shown below. Figure 2 As shown, it includes a pulse power generator 1, an upper high-voltage electrode 2, a lower grounding electrode 3, a slurry sealed cavity 4, a constant temperature control jacket 5, a water-cooled circulation inlet 6, a slurry feed port 7, and a slurry discharge port 8.

[0052] By employing vertically opposed electrodes and a closed-loop temperature control structure with a full-area water-cooled jacket, combined with the applied pulse power supply 9, the pulse can release energy instantaneously in microseconds to destroy the silicate lattice, while the water-cooled jacket continuously removes heat, achieving thermal phase change and no calcination throughout the dielectric lattice activation process; the upper and lower electrodes are sealed and immersed in the slurry, and the electric field action zone 10 fully covers the slurry, avoiding uneven activation in certain areas.

[0053] Under a constant system temperature of 35℃, a high-voltage pulsed electric field was applied for treatment; the pulsed electric field parameters were: electric field strength 32kV / cm, pulse width 10μs, pulse frequency 300Hz, and activation treatment time 5min.

[0054] S3. Green composite organic acid selective leaching: The activated slurry is transferred to a closed organic acid leaching reactor. The specific structure of the reactor is as follows: Figure 3 As shown, the reactor includes a vessel body 21, an insulated outer shell 22, a central variable frequency stirring paddle 23, a leachate filling port 24, a slurry feeding port 25, a built-in temperature control sensor 26, a temperature control heating component 27, a bottom discharge port 28, and a pressure relief valve 29, forming an integrated sealed reactor.

[0055] A 10% (w / w) composite organic acid leachate was added and leached at 70°C with stirring at 400 r / min for 3 h. The composite organic acid was prepared by mixing citric acid, malic acid, and acetic acid in a (w / w) ratio of 3:2:1.

[0056] S4. Solid-liquid separation and solution purification: After leaching, solid-liquid separation is achieved by plate and frame filter press to obtain lithium-rich leachate and lithium extraction tailings; the lithium-rich leachate is then subjected to flocculation, ultrafiltration and low-temperature concentration to obtain high-purity lithium-rich solution. The device adopts plate and frame filter press, pH segmented precipitation kettle and flocculation ultrafiltration concentration unit.

[0057] S5. Associated Metal Gradient Recovery: By adjusting the pH value of the lithium-rich solution in stages, valuable metals such as aluminum, potassium, rubidium, and cesium are recovered through stepwise precipitation. The specific operation process of this step is as follows: 1. Pre-processing basic conditions Raw materials: High-purity lithium-rich solution obtained in step S4, with a lithium concentration of 18-25 g / L and containing Al³⁺. + K + 、Rb + Cs + Soluble ions, total impurity metal content 3-7 g / L; Equipment: Segmented adjustable pH closed stirred sedimentation tank, equipped with online pH sensor and pressure filtration separation unit; Stirring reference speed: 250 r / min, system temperature controlled at 40-60℃ throughout the process (low temperature avoids lithium co-precipitation loss).

[0058] 2. Stepwise precipitation with precise pH, reagent, temperature control, sedimentation, and separation parameters. Preferential precipitation of aluminum - pH adjustment target: 4.0-4.5; Neutralizing agent: Low-concentration food-grade calcium hydroxide emulsion (5% by mass, green and free of chlorine impurities); Reaction temperature: 40℃, stirring time: 60min; Settling time: 90 min; plate and frame filter press to separate aluminum hydroxide filter cake (aluminum salt raw material can be sold externally). Key control points: pH should not exceed 4.5 to prevent the loss of small amounts of lithium through simultaneous co-precipitation; Precipitation of potassium: The filtrate is transferred to a secondary precipitation tank to remove aluminum and then the mother liquor is used. pH adjustment target: 8.0-8.5; Conditioner: Dilute lithium hydroxide solution (concentration 10 g / L, introducing cations without additional impurities); Reaction temperature: 50℃, stirring time: 90 min; Precipitating agent: Add saturated potassium hexafluorosilicate precipitant, the amount added is 1.05 times the theoretical amount of potassium; Settling time: 120 min; potassium fluorosilicate product is separated by pressure filtration, and potassium salt chemical raw material is produced as a by-product. Stepwise enrichment of rubidium and cesium (dilute alkali metal gradient precipitation): The secondary potassium removal mother liquor is transferred to the tertiary precipitation tank; Rubidium precipitation section: pH: 9.0-9.5, temperature 55℃, stirring for 100 min, precipitant used: dilute sodium tetraphenylborate solution, added in excess of 1.1 times, allowed to settle for 150 min, and the rubidium salt filter cake was separated. Cesium precipitation section: final pH: 10.0-10.5, temperature 60℃, stirring for 120 min, adding sodium tetraphenylborate precipitant with an excess coefficient of 1.15 times, allowing to settle for 180 min, and then filtering to obtain high-purity cesium salt solid, which can be purified to prepare cesium-based electronic materials; Control parameters for lithium mother liquor reuse: The final liquid after all associated metals have been separated has a stable pH of 7.0-7.5 and a lithium loss rate of ≤1.2%, and is directly sent to the concentration process to prepare battery-grade lithium products.

[0059] The entire process involves no strong alkalis or acids, the precipitating agent can be easily regenerated and recycled, and the precipitate residue is free of heavy metal pollution.

[0060] Throughout the process, the temperature was controlled at 50℃ in stages. The first stage for aluminum removal was at pH 4.2 and the reaction time was 60 min. The second stage for potassium precipitation was at pH 8.2 and the reaction time was 90 min. The third stage for rubidium precipitation was at pH 9.2 and the cesium precipitation time was at pH 10.2. The stirring speed in each stage was 250 r / min, and the settling time in each stage was 90 / 120 / 160 min respectively. The excess coefficient of the precipitating agent was controlled at 1.05-1.15 times.

[0061] S6. Low-Temperature Resource Utilization of Lithium Extraction Tailings: Lithium extraction tailings are dried, ultrafine ground, and modified by low-temperature cross-linking at 60-80℃ to prepare inorganic environmentally friendly building materials, achieving full resource utilization of solid waste. Specific equipment used includes... Figure 4 As shown, this step follows the process of drying wet slag → ultrafine grinding → low-temperature cross-linking modification → sieving and grading → finished building material filler. The specific process is as follows: 1. The low-temperature drum dryer 31 performs the drying process: drying temperature range: 60-80℃ (strictly low temperature, prohibition >90℃ to avoid secondary sintering of the crystal lattice), drum dwell time: 45-75min, moisture content at the end of drying: ≤3%, equipment accessories: hot air closed-loop circulation, exhaust gas condensation and recovery of trace organic acids, and circulation back to the S3 leaching process. 2. The ultrafine powder pulverization process uses a drum-type low-temperature dryer 31 to feed the dry residue into an ultrafine powder pulverizer 32. The output particle size is ≥92% of 325 mesh. The pulverizer speed is 2800 r / min. The pulverization is carried out at room temperature using a dry method without heating. 3. Additive mixing and low-temperature crosslinking modification: Specifically, the additives are mixed and stirred. The modification equipment is a low-temperature constant-temperature modification reaction chamber 33, with temperature control at 60-80℃. Modifying additive ratio (based on dry tailings quality): silane coupling agent KH-550: 0.5%, light calcium carbonate filler: 7%, low molecular weight organic dispersant (recycled citric acid residual mother liquor): 3%, modification temperature: 70℃, stirring speed in the chamber: 300 r / min, crosslinking reaction time: 90-150 min, crosslinking reaction atmosphere: atmospheric pressure, sealed, slight nitrogen isolation to prevent oxidation, and no waste gas emission.

[0062] 4. After the modified powder is cooled to room temperature, it is sieved and graded into two building material filler specifications: 200 mesh and 325 mesh. There is no waste residue after sieving, and all of it is recycled for secondary grinding.

[0063] The wet tailings from lithium extraction were dried at 70℃ for 60 minutes until the moisture content was ≤3%; then ultra-finely pulverized to 325 mesh ≥92%; 0.5% silane coupling agent, 7% light calcium carbonate, and 3% recycled organic acid dispersant were added according to the dry residue weight, and the mixture was cross-linked at 70℃ for 120 minutes with a stirring speed of 300 r / min; after cooling and sieving, inorganic environmentally friendly building filler was obtained and recycled to the finished filler silo 34. The tailings were 100% resource-based and there was no solid waste discharge.

[0064] Testing revealed that in step S5 of the above embodiment, the overall recovery rate of associated metals was 93.5%, and the lithium loss was 0.9%. The lithium extraction tailings obtained in step S6 can be used in wall putty, concrete admixtures, and waterproof fillers.

[0065] Example 2 The specific operation steps are the same as in Example 1, except that in step S2, a high-voltage pulsed electric field is applied under the condition that the system temperature is constant at 25°C. The pulsed electric field parameters are: electric field strength 40kV / cm, pulse width 5μs, pulse frequency 400Hz, activation treatment time 3min, and the lithium leaching rate is 97.5% after final testing.

[0066] Example 3 The specific operation steps are the same as in Example 1, except that in step S2, a high-voltage pulsed electric field is applied under the condition that the system temperature is constant at 50°C. The pulsed electric field parameters are: electric field strength 25kV / cm, pulse width 15μs, pulse frequency 200Hz, activation treatment time 8min, and the final detection shows that the lithium leaching rate reaches 97.3%.

[0067] Example 4 The specific operating steps are the same as in Example 1, except that in step S3, an 8% (w / w) composite organic acid leaching solution is added, and the solution is leached at a constant temperature of 90°C and a stirring speed of 300 r / min for 4 hours. The composite organic acid is prepared by mixing citric acid, malic acid, and acetic acid in a mass ratio of 1:1:1. The final test showed that the lithium leaching rate reached 97.6%.

[0068] Example 5 The specific operating steps are the same as in Example 1, except that in step S3, a 15% (w / w) composite organic acid leaching solution is added, and the solution is leached at a constant temperature of 60°C and stirred at 500 rpm for 2 hours. The composite organic acid is prepared by mixing citric acid, malic acid, and acetic acid in a mass ratio of 4:3:1. The final test showed that the lithium leaching rate reached 97.8%.

[0069] Experimental Example 1 See Figure 5 As shown, through Figure 5 The comparison of leaching effects (reference 4 corresponds to Example 1 of this application) shows that: reference 1 is a traditional high-temperature roasting and roasting kiln equipment with high energy consumption and exhaust gas pollution, and the lithium leaching rate is only 85%; reference 2 is a strong acid leaching and strong acid resistant high-pressure reactor with severe corrosion and many impurities, and the leaching rate is 91%; reference 3 is a common organic acid leaching and conventional stirred tank with no lattice activation and strong mineral inertness, and the leaching rate is only 83%.

[0070] The lithium extraction method and apparatus in this application are characterized by low temperature and no roasting throughout the process, low corrosion, lithium leaching rate of 98.2%, energy consumption reduced by 75% compared to roasting process, simultaneous recovery of associated metals, and full resource utilization of tailings.

[0071] This application solves the problem of pulsed heat generation by using a water-cooled constant-temperature pulse device, achieving high leaching at low temperatures. A weak acid closed reactor enables selective lithium extraction, and a matching low-temperature modification device allows for the utilization of solid waste without high temperatures. A low-temperature pH gradient precipitation reactor enables low-loss recovery of associated metals.

[0072] It should be noted that, where there is no conflict, the features in the embodiments of this application can be combined with each other.

[0073] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for lithium extraction from low-grade lithium ore activated by a low-temperature, high-pressure pulsed electric field, characterized in that, Includes the following steps: Low-grade lithium ore is ground into a slurry and then subjected to high-voltage pulse electric field treatment at a temperature of 25-50℃. The treated slurry is selectively leached with a composite organic acid, which includes citric acid, malic acid, and acetic acid. After leaching, solid-liquid separation, precipitation and recovery of valuable metals, and low-temperature resource utilization of tailings are achieved.

2. The method for lithium extraction from low-grade lithium ore by low-temperature high-pressure pulsed electric field activation according to claim 1, characterized in that, The electric field strength of the high-voltage pulse electric field treatment is 25-40 kV / cm, the pulse width is 5-15 μs, the pulse frequency is 200-400 Hz, and the treatment time is 3-8 min.

3. The method for lithium extraction from low-grade lithium ore by low-temperature high-pressure pulsed electric field activation according to claim 2, characterized in that, The high-voltage pulsed electric field treatment was performed at a temperature of 35℃, an electric field strength of 32kV / cm, a pulse width of 10μs, a pulse frequency of 300Hz, and an activation time of 5min.

4. The method for lithium extraction from low-grade lithium ore by low-temperature high-pressure pulsed electric field activation according to claim 1, characterized in that, The composite organic acid is a mixture of citric acid, malic acid and acetic acid, with a mass ratio of (1-4):(1-3):

1.

5. The method for lithium extraction from low-grade lithium ore by low-temperature high-pressure pulsed electric field activation according to claim 4, characterized in that, The mass ratio of citric acid, malic acid, and acetic acid in the composite organic acid is 3:2:

1.

6. The method for lithium extraction from low-grade lithium ore by low-temperature high-pressure pulsed electric field activation according to any one of claims 1-5, characterized in that, The selective leaching temperature is 60-90℃, the stirring speed is 300-500r / min, and the leaching time is 2-4h.

7. The method for lithium extraction from low-grade lithium ore by low-temperature high-pressure pulsed electric field activation according to any one of claims 1-5, characterized in that, The added compound organic acid has a mass concentration of 8%-15%.

8. The method for lithium extraction from low-grade lithium ore by low-temperature high-pressure pulsed electric field activation according to any one of claims 1-5, characterized in that, The slurry formed by grinding low-grade lithium ore includes lithium ore slurry with a particle size of 200 mesh and a mass percentage content of 60-75%, and the solid-liquid ratio of the slurry is 1:(2-4).

9. The method for lithium extraction from low-grade lithium ore by low-temperature high-pressure pulsed electric field activation according to any one of claims 1-5, characterized in that, The method for low-temperature resource utilization of tailings includes the following steps: the tailings are dried, ultra-fine ground, and cross-linked modified at a low temperature of 60-80℃.

10. A lithium extraction apparatus, employing the lithium extraction method for low-grade lithium ore activated by a low-temperature high-pressure pulsed electric field as described in any one of claims 1-9, characterized in that, The lithium extraction device includes, in sequence, a low-temperature high-pressure pulsed electric field constant temperature activation device, an organic acid closed leaching reactor, and a complete set of units for low-temperature drying, ultrafine pulverization, and cross-linking modification of lithium extraction tailings.

Images