Low-quality lithium ore separation and enrichment method

Abstract

The invention relates to the field of mineral separation, and provides a low-quality lithium ore separation and enrichment method which comprises the following steps: crushing lithium ore to obtain particles with the average particle size of 1-5mm; weighing the crushed lithium ore particles and solid sodium hydroxide, mixing, and carrying out ball milling for 1-5 hours; adding water into a ball milling product, and carrying out ball milling for 5-20 hours until the average particle size of solid particles is 1-50 microns; carrying out strong magnetic separation on the ball-milled ore pulp to obtain magnetic minerals; filtering and drying the non-magnetic ore pulp to obtain filter residues; water is added into the filter residues to obtain slurry with the mass concentration of 20%-40%, sodium hexametaphosphate is added into the slurry, the pH of the slurry is adjusted to be 7-9, stirring is conducted for 3-7 min, then didecyl dimethyl ammonium chloride is added, stirring is conducted for 5-8 min, flotation is conducted for 5-10 min, and lithium concentrate is obtained. A combined method of alkali grinding dissociation, strong magnetic separation and selective flotation is adopted, the technical bottleneck of efficient enrichment of the low-quality lithium ore is broken through, and no complex flotation reagent is needed.

Description

Technical Field

[0001] The present application relates to the field of mineral processing, and in particular to a method for separating and enriching low-quality lithium ores. Background Art

[0002] Lithium and its compounds are essential materials for electric vehicles and renewable energy. With the continuous advancement of technologies such as computers, digital cameras, mobile phones, and electric vehicles, the role of lithium has become increasingly prominent. Furthermore, lithium plays a crucial role in industry and science and technology, leading to an increasingly urgent demand for lithium. Lithium is primarily extracted from lithium-containing minerals. Global lithium reserves are abundant but unevenly distributed. To date, scientists have discovered over 150 lithium-containing minerals, but only four are currently suitable for development: apatite (Li2O content 7%-9%), spodumene (Li2O content 6%-7%), lithium-bearing sansitite (Li2O content 3.5%-4.5%), and lepidolite (Li2O content 3%-4%). Currently, lithium is primarily isolated and extracted from lithium ore and is a cornerstone of the development of the new energy vehicle industry.

[0003] Besides lithium-containing materials, the main minerals in lithium ore samples are gangue minerals such as feldspar, quartz, and mica, i.e., gangue components primarily consisting of SiO2 and Al2O3. Furthermore, most lithium ore is fine-grained, embedded within the gangue minerals. Therefore, grinding is often required to dissociate the individual particles. However, this process inevitably leads to overgrinding of the lithium ore, resulting in lithium loss in the fine mud. Furthermore, the flotation of ultrafine minerals also suffers from high reagent consumption and low flotation grade, leading to the loss of lithium resources. Currently, 200 mesh is widely used as the general particle size for grinding and dissociating lithium. However, at this particle size, some lithium is still not completely dissociated from the embedded ore, resulting in a large amount of lithium remaining in the tailings, causing flotation losses.

[0004] Currently, research on this topic is focused on developing new flotation reagents or adjustment processes. For example, CN115999774A discloses a method for beneficiating low-grade spodumene, comprising the following steps: wet-grinding the raw ore to be beneficiated to produce a first slurry, then adding water and stirring the first slurry to produce a slurry of a predetermined concentration; adding a first predetermined reagent to the resulting slurry for reverse flotation to produce sludge and deslimed tailings; and adding a second predetermined reagent to the deslimed tailings for forward flotation to produce lithium concentrate and tailings. The second predetermined reagent includes an adjustment agent, a composite depressant, and a composite collector. The composite depressant is a compound of tannic acid, hydroxycitric acid, lactic acid, and sodium lignin sulfonate; and the composite collector is a compound of oleic acid, tall oil, naphthenic acid, and white oil. This reverse flotation desliming-forward flotation process for recovering spodumene separates a large amount of gangue minerals. The combined action of the composite depressant and collector allows for the effective recovery of low-grade spodumene. CN116103514A discloses a method for extracting lithium, aluminum, sulfur and silicon from low-grade clay-type lithium ore, comprising the steps of flotation desulfurization and decarbonization pre-enrichment, roasting, primary leaching, purification and impurity removal, and secondary leaching. The clay-type lithium ore is mainly composed of clay minerals, with a lithium oxide content of no more than 1wt%, and lithium elements are mainly present in the clay-type lithium ore in the form of lithium chlorite. A combined dressing and smelting process is adopted to obtain sulfur concentrate, lithium carbonate, aluminum oxide and high-silicon slag through graded extraction, thereby realizing the comprehensive utilization of low-grade clay-type lithium ore. CN115999762A discloses a combined gravity-flotation beneficiation method for low-grade spodumene ore. The raw ore is fed into a crushing-screening operation, and the obtained undersize product is fed into a high-frequency vibrating screen for wet screening. The undersize product is fine mud, and the oversize product is fed into a three-product heavy medium cyclone for separation to obtain gravity-separated spodumene concentrate, gravity-separated tailings, and gravity-separated middlings, respectively. The fine mud is combined with the gravity-separated middlings and fed into a grinding-classification operation. The classification overflow is used as flotation feed for flotation recovery of spodumene. The spodumene flotation operation adopts a process flow of one coarse, two fine, and one scavenger, with the middlings returned in sequence, to ultimately obtain a flotation spodumene concentrate with a Li2O grade of ≥5.7% and a flotation spodumene tailing with a Li2O grade of ≤0.35%. CN115870086A discloses a method for recovering lithium concentrate from lithium-containing ore. The method comprises: using a SABC crushing and grinding system to crush the lithium-containing ore to obtain ore particles with a particle size of no greater than 0.25 mm; subjecting the material to a first magnetic separation to obtain a first magnetic mineral and a first non-magnetic mineral; subjecting the first non-magnetic mineral to a gravity separation to obtain a gravity-separated non-lithium concentrate and gravity-separated tailings, wherein the gravity separation comprises a spreading chute process and a shaking table process in sequence; desludging and classifying the gravity-separated tailings to obtain ore sand and ore slime; and flotation separation of the ore sand to obtain lithium concentrate. The method has a low production cost and is beneficial for improving the recovery rate of lithium-containing ores, especially ultra-low-grade lithium-containing ores, and the grade of lithium concentrate.CN113046548A discloses a beneficiation method for low-grade spodumene ore, comprising the following steps: S1, crushing the low-grade spodumene ore into blocks with a diameter of less than 5 cm; S2, preheating, preheating the block ore after crushing in S1 to a temperature of 200-500°C; S3, sintering, transferring the block ore preheated in step S2 to a sintering furnace, heating it to 1000-1100°C, and sintering it for 0.5-1h; S4, screening lithium concentrate ore powder, naturally cooling the powder after sintering in step S3 to room temperature, and then screening it with 100-200 mesh. The fine powder under the sieve is the lithium concentrate ore powder selected from the ore; the coarse powder on the sieve is coarse sand containing part of the lithium concentrate. CN109701735A discloses a composite collector comprising amino acids, fatty acids, and diesel fuel in a weight ratio of (80-90):(5-10):(5-10). The composite collector can improve the lithium grade in spodumene concentrate without wasting lithium resources, while also reducing the content of iron impurities. However, the aforementioned methods all suffer from problems such as large lithium losses, complex and costly flotation reagents, and cumbersome procedures.

[0005] Therefore, how to effectively sort low-quality lithium ore through simple processes, improve its economic value, and make full use of low-grade lithium ore is a technical problem that needs to be solved urgently. Summary of the Invention

[0006] To address the problems of low lithium recovery rates in low-quality lithium ore, complex and costly flotation reagents, and cumbersome processes, a method for the separation and enrichment of low-quality lithium ore is provided. The method comprises the following steps: crushing the lithium ore; mixing the crushed lithium ore particles with solid sodium hydroxide and then ball milling; adding water to the milled product and continuing to ball mill until the solid particles have an average particle size of 1-50μm; obtaining magnetic minerals through strong magnetic separation, filtering the non-magnetic slurry, and drying to obtain a filter residue; adding sodium hexametaphosphate and didecyldimethylammonium chloride to the filter residue and flotating for 5-10 minutes with agitation to obtain a lithium concentrate. This method utilizes a combined process of alkaline milling dissociation, strong magnetic separation, and selective flotation, breaking through the technical bottleneck of efficient enrichment of low-quality lithium ore (Li2O <1.2%). It does not require complex flotation reagents and offers significant advantages in terms of grade improvement, recovery, cost control, and environmental friendliness.

[0007] Specifically, the present invention proposes a method for sorting and enriching low-quality lithium ore, comprising the following steps: S1. Crushing the lithium ore to obtain particles with an average particle size of 1-5 mm; S2. Weigh the crushed lithium ore particles and solid sodium hydroxide in a mass ratio of 1:1-1.5, mix them, and ball mill for 1-5 hours; solid NaOH reacts with the lithium ore during the ball milling process, and NaOH penetrates into the mineral lattice, destroying Si-O-Al bonds and promoting the dissociation of minerals such as spodumene and lepidolite; S3. Add water to the ball-milled product of step S2 at a mass concentration of 1%-20% of the lithium ore particles, and continue ball milling for 5-20 hours until the average particle size of the solid particles is 1-50 μm; subject the ball-milled pulp to strong magnetic separation with a magnetic field strength of 1.2T-1.5T to obtain magnetic minerals; filter the non-magnetic pulp, dry it, and obtain a filter residue; through two-step ball milling, the average particle size of the solid particles is finally reduced to 1-50 μm, which significantly improves the separation efficiency of the target mineral and the gangue mineral; in addition, the dissolution and separation of quartz and alumina is further promoted in a strong alkaline environment, further improving the separation of the target mineral and the gangue mineral.

[0008] S4. Add water to the filter residue to obtain a slurry with a mass concentration of 20% to 40%, add sodium hexametaphosphate thereto, and adjust the pH to 7 to 9. Stir for 3 to 7 minutes, then add didecyldimethylammonium chloride, stir for 5 to 8 minutes, and float for 5 to 10 minutes to obtain lithium concentrate.

[0009] Preferably, the low-quality lithium ore includes at least one of spodumene, lepidolite, and petalite, and the Li2O grade in the lithium ore is lower than 1.2%.

[0010] Preferably, the crushing in step S1 is performed using a combination of a jaw crusher and a cone crusher for multi-stage crushing, and the particle size D90 is controlled by screening after crushing to be 1-5 mm. The use of a combination of a jaw crusher and a cone crusher for multi-stage crushing facilitates more effective dissociation of useful minerals from gangue minerals during the subsequent ball milling process, thereby improving the degree of monomer dissociation of the minerals.

[0011] Preferably, in step S2, the purity of the solid sodium hydroxide is ≥95%, the ball milling is one of drum ball milling, planetary ball milling, and sand milling, the ball milling medium is one of steel balls and zirconia balls, the ball-to-material mass ratio during ball milling is (5-10):1, and the ball mill speed is 300-500 rpm, so that efficient crushing and mixing can be achieved.

[0012] Preferably, in step S2, nitrogen is introduced during the ball milling process to control the temperature in the ball mill to ≤ 60° C. This prevents the ore from oxidizing at high temperatures and maintains the mineral activity. At the same time, controlling the temperature avoids changes in the mineral structure caused by overheating.

[0013] Preferably, in step S3, the high-intensity magnetic separation uses a pulsating high-gradient magnetic separator with a pulsation frequency of 200-300 times / min and a slurry flow rate of 0.5-1.5 L / min. This process can effectively remove magnetic minerals such as iron, resulting in a non-magnetic lithium ore slurry, reducing the impact of these impurities on the subsequent flotation process, thereby improving the concentrate grade.

[0014] Preferably, in step S4, the amount of sodium hexametaphosphate added is 0.5-2 kg / t of filter residue, and the amount of didecyldimethylammonium chloride added is 0.3-1 kg / t of filter residue.

[0015] Preferably, in step S4, pH adjustment is performed using at least one of sodium carbonate, sodium hydroxide, hydrochloric acid, and sulfuric acid, with a stirring speed of 1000-1500 rpm. Flotation is performed using a mechanically agitated flotation cell. By adjusting pH, selecting specific inhibitors, and selecting collectors, the ore slime can be effectively dispersed, preventing it from encapsulating the target mineral, further creating a suitable flotation environment and achieving good selectivity and collection capacity.

[0016] Preferably, after step S4, the process further comprises washing the lithium concentrate: washing the lithium concentrate with deionized water for 3-5 times, filtering and drying the lithium concentrate after washing to obtain a lithium concentrate with a Li2O grade of ≥8%.

[0017] Preferably, in step S4, the flotation foam product undergoes secondary concentrating, adding 0.2-0.5 kg / t of flotation foam of sodium hexametaphosphate and 0.1-0.4 kg / t of flotation foam of didecyldimethylammonium chloride. This secondary concentrating further purifies the concentrate, yielding a high-quality lithium concentrate with a higher LiO grade. The secondary concentrating process involves stirring for 2-5 minutes and flotation for 1-3 minutes.

[0018] The beneficial effects of the present invention include: 1. The present invention can effectively improve the grade and recovery rate of lithium concentrate. Through multi-stage crushing, alkaline milling dissociation, high-concentration alkaline solution ball milling and selective flotation, the Li2O grade in the raw ore can be enriched from ≤1.2% to ≥8%, reaching the standard of industrial-grade lithium concentrate; 2. By using magnetic separation, secondary concentration and flotation of didecyldimethylammonium chloride + sodium hexametaphosphate, the Li2O recovery rate can reach ≥95%, which is significantly higher than the traditional process; 3. Specific treatment processes can effectively improve the dissociation of lithium ore. In the first ball milling, solid NaOH and ore undergo a mechanochemical reaction during the ball milling process. NaOH penetrates into the mineral lattice, destroying the Si-O-Al bond and promoting the dissociation of minerals such as spodumene and lepidolite. The second ball milling in a strong alkaline environment allows the lithium minerals to be fully dissociated into monomers while avoiding the fine mud caused by over-grinding, reducing reagent consumption and flotation foam entrainment. In addition, it can further promote the destruction of Si-O-Al bonds and accelerate the dissociation of lithium ore and gangue components such as quartz. 4. The method of the present invention has a simple process, is easy to operate, does not require complex flotation agents, has low cost, significantly improves the sorting efficiency and concentrate grade of lithium ore, greatly improves resource utilization and economic benefits, and provides reliable technical support for the effective development and utilization of low-grade lithium resources. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this invention pertains. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless specifically defined as herein, should not be interpreted in an idealized or overly formal sense. The reagents used herein may be commercially available products, and performance testing standards refer to industry or national standards.

[0021] It will be understood by those skilled in the art that, unless otherwise stated, the singular forms "a," "an," "said," and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the stated features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The term "and / or" used herein includes all or any unit and all combinations of one or more associated listed items.

[0022] The following is a further detailed description of the characteristics and performance of the present application in conjunction with the examples: the lithium ore is selected from the low-quality spodumene, lepidolite, and phosphate lithium aluminum stone composite lithium ore of the Jiajika lithium mine in Sichuan. The main valuable element in the ore is lithium, containing Li2O 1.05wt%, SiO2 and Al2O3 contents of 68.4wt% and 14.5wt% respectively. Lithium is mainly found in spodumene and lepidolite, and a small amount is found in phosphate lithium aluminum stone. It is an ultra-low-grade spodumene, lepidolite and phosphate lithium aluminum stone composite lithium ore.

[0023] Example 1 A method for separating and enriching low-quality lithium ore comprises the following steps: S1. Use a combination of jaw crusher and cone crusher for multi-stage crushing, and screen the crushed particles to a particle size D90 of 1-5mm. S2. Weigh the crushed lithium ore particles and solid sodium hydroxide with a purity of ≥95% in a mass ratio of 1:1, mix them, and then ball-mill for 5 hours; the ball milling is performed by roller milling, the ball milling medium is steel balls, the ball-to-material mass ratio during ball milling is 5:1, and the ball mill speed is 300 rpm; nitrogen protection is introduced during the ball milling process, and the temperature in the ball mill is controlled to be ≤60°C; S3, according to the mass concentration of lithium ore particles 1% to the ball milling product of step S2, water was added, and the ball milling was continued for 20h to a solid particle average particle size of 10-50μm; the ore pulp after ball milling was subjected to strong magnetic separation using a pulsating high gradient magnetic separator with a magnetic field strength of 1.2T, a pulsation frequency of 300 times / min, and a slurry flow rate of 1.5L / min to obtain magnetic minerals; the non-magnetic slurry was filtered and dried to obtain a filter residue; S4. Add water to the filter residue to obtain a slurry with a mass concentration of 20%, add 2 kg / t of sodium hexametaphosphate to the slurry, adjust the pH to 7, and stir at 1500 rpm for 7 minutes. Then, add 1 kg / t of didecyldimethylammonium chloride to the slurry, stir for 5 minutes, and float on a mechanical agitation flotation machine for 10 minutes. Wash with deionized water 3-5 times, filter and dry after washing to obtain a lithium concentrate with a Li2O grade of 8.3%. The calculated Li2O recovery rate is 95.2%. Example 2 A method for separating and enriching low-quality lithium ore comprises the following steps: S1. Use a combination of jaw crusher and cone crusher for multi-stage crushing, and screen the crushed particles to a particle size D90 of 1-5mm. S2. Weigh the crushed lithium ore particles and solid sodium hydroxide with a purity of ≥95% in a mass ratio of 1:1.5, mix them, and then ball-mill for 1 hour; the ball milling is sand milling, the ball milling medium is zirconia balls, the ball-to-material mass ratio during ball milling is 10:1, and the ball mill speed is 500 rpm; nitrogen protection is introduced during the ball milling process, and the temperature in the ball mill tank is controlled to be ≤55°C; S3, according to the mass concentration of lithium ore particles 20% to the ball milling product of step S2, continue ball milling for 5h, to the average particle size of the solid particles is 1-30μm; the slurry after ball milling is subjected to strong magnetic separation using a pulsating high gradient magnetic separator with a magnetic field strength of 1.5T, a pulsation frequency of 200 times / min, and a slurry flow rate of 0.5L / min to obtain magnetic minerals; the non-magnetic slurry is filtered and dried to obtain a filter residue; S4. Add water to the filter residue to obtain a slurry with a mass concentration of 40%, add 0.5 kg / t of sodium hexametaphosphate to the slurry, adjust the pH to 9, and stir at 1000 rpm for 3 minutes. Then, add 0.8 kg / t of didecyldimethylammonium chloride to the filter residue, stir for 8 minutes, float on a mechanical agitator flotation machine for 5 minutes, wash with deionized water 3-5 times, filter and dry after washing, and perform secondary concentration on the product. During the secondary concentration, add 0.2 kg / t of sodium hexametaphosphate and 0.4 kg / t of didecyldimethylammonium chloride as flotation foam, stir for 5 minutes, and float for 3 minutes. After flotation, wash with deionized water, filter and dry to obtain a lithium concentrate with a Li2O grade of 8.9%. The calculated Li2O recovery rate is 96.3%. Example 3 A method for separating and enriching low-quality lithium ore comprises the following steps: S1. Use a jaw crusher and a cone crusher for multi-stage crushing. After crushing, the particle size D90 is controlled by screening to 2-3mm. S2. Weigh the crushed lithium ore particles and solid sodium hydroxide with a purity of ≥95% in a mass ratio of 1:1.3, mix them, and then ball-mill for 3 hours; the ball mill is a planetary ball mill, the ball-to-material mass ratio during ball milling is 7:1, and the ball mill speed is 400 rpm; nitrogen protection is introduced during the ball milling process, and the temperature in the ball mill is controlled to be ≤50°C; S3, according to the mass concentration of lithium ore particles 10% to the ball milling product of step S2, water was added, and the ball milling was continued for 15h to a solid particle average particle size of 10-40μm; the ore pulp after ball milling was subjected to strong magnetic separation using a pulsating high gradient magnetic separator with a magnetic field strength of 1.3T, a pulsation frequency of 250 times / min, and a slurry flow rate of 1L / min to obtain magnetic minerals; the non-magnetic ore pulp was filtered and dried to obtain a filter residue; S4. Add water to the filter residue to obtain a slurry with a mass concentration of 30%, add 0.6 kg / t of filter residue of sodium hexametaphosphate, adjust the pH to 8, and stir at 1200 rpm for 5 minutes. Then, add 0.3 kg / t of filter residue of didecyldimethylammonium chloride, stir for 6 minutes, float on a mechanical agitation flotation machine for 8 minutes, wash with deionized water 3-5 times, filter and dry after washing, and perform secondary concentration on the product. During the secondary concentration, add 0.5 kg / t of flotation foam of sodium hexametaphosphate and 0.1 kg / t of flotation foam of didecyldimethylammonium chloride, stir for 3 minutes, and float for 1 minute. After flotation, wash with deionized water, filter and dry to obtain a lithium concentrate with a Li2O grade of 9.1%. The calculated Li2O recovery rate is 95.1%. Comparative Example 1 A method for separating and enriching low-quality lithium ore comprises the following steps: S1. Use a jaw crusher to crush the lithium ore, and sieve it to control the particle size D90 to 10-20mm after crushing; S2. Weigh the crushed lithium ore particles and ball mill them for 5 h; the ball mill is a drum mill with steel balls as the milling medium, the ball-to-material mass ratio during ball milling is 5:1, and the ball mill speed is 300 rpm; nitrogen protection is introduced during the ball milling process, and the temperature in the ball mill is controlled to be ≤60°C; S3, according to the mass concentration of lithium ore particles 1% to the ball milling product of step S2, water was added, and the ball milling was continued for 20h to a solid particle average particle size of 74μm; the ore pulp after ball milling was subjected to strong magnetic separation using a pulsating high gradient magnetic separator with a magnetic field strength of 1.2T, a pulsation frequency of 300 times / min, and a slurry flow rate of 1.5L / min to obtain magnetic minerals; the non-magnetic ore pulp was filtered and dried to obtain a filter residue; S4. Add water to the filter residue to obtain a slurry with a mass concentration of 20%, add 2 kg / t of sodium hexametaphosphate to the slurry, adjust the pH to 7, and stir at 1500 rpm for 7 minutes. Then, add 1 kg / t of didecyldimethylammonium chloride to the slurry, stir for 5 minutes, and float on a mechanical agitation flotation machine for 10 minutes. Wash with deionized water 3-5 times, filter and dry after washing to obtain a lithium concentrate with a Li2O grade of 3.2%. The calculated Li2O recovery rate is 25.7%.

[0024] Comparative Example 2 A method for separating and enriching low-quality lithium ore comprises the following steps: S1. Use a combination of jaw crusher and cone crusher for multi-stage crushing, and screen the crushed particles to a particle size D90 of 1-5mm. S2. Weigh the crushed lithium ore particles and solid sodium hydroxide with a purity of ≥95% in a mass ratio of 5:1, mix them, and ball-mill for 3 h; the ball milling is performed by roller milling, the ball-to-material mass ratio is 5:1, and the ball mill speed is 300 rpm; nitrogen protection is introduced during the ball milling process, and the temperature in the ball mill is controlled to be ≤60°C; S3, according to the mass concentration of lithium ore particles 25% to the ball milling product of step S2, continue ball milling for 20h, to the average particle size of the solid particles is 30-80μm; the slurry after ball milling is subjected to strong magnetic separation using a pulsating high gradient magnetic separator with a magnetic field strength of 1.2T, a pulsation frequency of 300 times / min, and a slurry flow rate of 2L / min to obtain magnetic minerals; the non-magnetic slurry is filtered and dried to obtain a filter residue; S4. Add water to the filter residue to obtain a slurry with a mass concentration of 15%, add 0.4 kg / t of sodium hexametaphosphate to the slurry, stir at 1500 rpm for 7 minutes, then add 1.2 kg / t of didecyldimethylammonium chloride to the slurry, stir for 5 minutes, float on a mechanical agitation flotation machine for 10 minutes, wash with deionized water 3-5 times, filter and dry after washing to obtain a lithium concentrate with a Li2O grade of 5.4%. The calculated Li2O recovery rate is 52.8%. Comparative Example 3 A method for separating and enriching low-quality lithium ore comprises the following steps: S1. Use a combination of jaw crusher and cone crusher for multi-stage crushing, and screen the crushed particles to a particle size D90 of 1-5mm. S2. Weigh the crushed lithium ore particles and mix them with sodium carbonate with a purity of ≥95% in a mass ratio of 1:1.5, and then ball-mill them for 1 hour; the ball milling is sand milling, the ball milling medium is zirconia balls, the ball-to-material mass ratio during ball milling is 10:1, and the ball mill speed is 500 rpm; nitrogen protection is introduced during the ball milling process, and the temperature in the ball mill is controlled to be ≤55°C; S3, according to the mass concentration of lithium ore particles 20% to the ball milling product of step S2, continue ball milling for 5h, to the average particle size of the solid particles is 10-30μm; the slurry after ball milling is subjected to strong magnetic separation using a pulsating high gradient magnetic separator with a magnetic field strength of 1.5T, a pulsation frequency of 200 times / min, and a slurry flow rate of 0.5L / min to obtain magnetic minerals; the non-magnetic slurry is filtered and dried to obtain a filter residue; S4. Add water to the filter residue to obtain a slurry with a mass concentration of 40%, add 0.5 kg / t of sodium hexametaphosphate to the slurry, adjust the pH to 9, and stir at 1000 rpm for 3 minutes. Then, add 0.8 kg / t of didecyldimethylammonium chloride to the slurry, stir for 8 minutes, float on a mechanical agitator flotation machine for 5 minutes, wash with deionized water 3-5 times, filter and dry after washing, and perform secondary concentration on the product. During the secondary concentration, add 0.2 kg / t of sodium hexametaphosphate and 0.4 kg / t of didecyldimethylammonium chloride as flotation foam, stir for 5 minutes, and float for 3 minutes. After flotation, wash with deionized water, filter and dry to obtain a lithium concentrate with a Li2O grade of 5.7%. The calculated Li2O recovery rate is 41.6%. Comparative Example 4 A method for separating and enriching low-quality lithium ore comprises the following steps: S1. Use a combination of jaw crusher and cone crusher for multi-stage crushing, and screen the crushed particles to a particle size D90 of 1-5mm. S2. Weigh crushed lithium ore particles and solid sodium hydroxide with a purity of ≥95% in a mass ratio of 1:1.5, add water to the lithium ore particles at a mass concentration of 20% of the lithium ore particles, stir and disperse them evenly, then add solid sodium hydroxide thereto, and ball mill for 5 hours to a solid particle size of 40-100 μm. The ball milling medium is zirconia balls. The ball-to-material mass ratio during ball milling is 10:1, and the ball mill speed is 500 rpm. During the ball milling process, nitrogen protection is introduced to control the temperature in the ball mill jar to ≤55°C. The milled slurry is subjected to strong magnetic separation using a pulsating high gradient magnetic separator with a magnetic field strength of 1.5 T, a pulsation frequency of 200 times / min, and a slurry flow rate of 0.5 L / min to obtain magnetic minerals. The non-magnetic slurry is filtered and dried to obtain a filter residue. S3. Add water to the filter residue to obtain a slurry with a mass concentration of 40%, add 0.5 kg / t of sodium hexametaphosphate to the slurry, adjust the pH to 9, and stir at 1000 rpm for 3 minutes. Then, add 0.8 kg / t of didecyldimethylammonium chloride to the slurry, stir for 8 minutes, float on a mechanical agitator flotation machine for 5 minutes, wash with deionized water 3-5 times, filter and dry after washing, and perform secondary concentration on the product. During the secondary concentration, add 0.2 kg / t of sodium hexametaphosphate and 0.4 kg / t of didecyldimethylammonium chloride as flotation foam, stir for 5 minutes, and float for 3 minutes. After flotation, wash with deionized water, filter and dry to obtain a lithium concentrate with a Li2O grade of 6.1%. The calculated Li2O recovery rate is 44.7%. Comparative Example 5 A method for separating and enriching low-quality lithium ore comprises the following steps: S1. Use a combination of jaw crusher and cone crusher for multi-stage crushing, and screen the crushed particles to a particle size D90 of 1-5mm. S2. Weigh the crushed lithium ore particles and solid sodium hydroxide with a purity of ≥95% in a mass ratio of 200:1, mix them, and then ball-mill for 1 hour; the ball milling is sand milling, the ball milling medium is zirconia balls, the ball-to-material mass ratio during ball milling is 10:1, and the ball mill speed is 500 rpm; S3, according to the mass concentration of lithium ore particles in step S2, 1M sodium hydroxide solution was added, and the ball milling was continued for 5h to a solid particle average particle size of 10-30μm; the slurry after ball milling was subjected to strong magnetic separation using a pulsating high gradient magnetic separator with a magnetic field strength of 1.5T, a pulsation frequency of 200 times / min, and a slurry flow rate of 0.5L / min to obtain a magnetic mineral; the non-magnetic slurry was filtered and dried to obtain a filter residue; S4. Add water to the filter residue to obtain a slurry with a mass concentration of 20%, add 0.5 kg / t of sodium hexametaphosphate to the slurry, adjust the pH to 8, and stir at 1000 rpm for 3 minutes. Then, add 0.8 kg / t of didecyldimethylammonium chloride to the slurry, stir for 8 minutes, float on a mechanical agitator flotation cell for 5 minutes, wash with deionized water 3-5 times, filter and dry after washing, and perform secondary concentration on the product. During the secondary concentration, add 0.2 kg / t of sodium hexametaphosphate and 0.4 kg / t of didecyldimethylammonium chloride as flotation foam, stir for 5 minutes, and float for 3 minutes. After flotation, wash with deionized water, filter and dry to obtain a lithium concentrate with a Li2O grade of 6.7%. The calculated Li2O recovery rate is 56.8%. The above is a detailed description of a method for sorting and enriching low-quality lithium ore. From the examples and comparative examples, it can be seen that the specific method of the present invention can obtain high-grade lithium concentrate with a content of more than 8%, and the recovery rate of Li2O is also relatively high, reaching 95%, which is significantly higher than that of the traditional process. The method of the present invention does not require complex flotation reagents and has low cost, providing reliable technical support for the effective development and utilization of low-grade lithium resources.

[0025] The above detailed description of the preferred embodiments of the present invention is only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for separation and enrichment of low-quality lithium ore, characterized in that: The following steps are involved: S1. Crushing the lithium ore to obtain particles with an average particle size of 1-5 mm; S2. Weigh the crushed lithium ore particles and solid sodium hydroxide in a mass ratio of 1:1-1.5, mix them, and then ball mill for 1-5 hours; S3, adding water to the ball-milled product of step S2 at a mass concentration of 1%-20% of the lithium ore particles, and continuing the ball milling for 5-20 hours until the average particle size of the solid particles is 1-50 μm; subjecting the ball-milled pulp to strong magnetic separation with a magnetic field strength of 1.2T-1.5T to obtain magnetic minerals; filtering the non-magnetic pulp, drying it, and obtaining a filter residue; S4. Add water to the filter residue to obtain a slurry with a mass concentration of 20% to 40%, add sodium hexametaphosphate thereto, and adjust the pH to 7 to 9. Stir for 3 to 7 minutes, then add didecyldimethylammonium chloride, stir for 5 to 8 minutes, and float for 5 to 10 minutes to obtain lithium concentrate.

2. The low-quality lithium ore separation and enrichment method according to claim 1, characterized in that: The low-quality lithium ore includes at least one of spodumene, lepidolite, and petalite, and the Li2O grade in the lithium ore is lower than 1.2%.

3. The low-quality lithium ore separation and enrichment method according to claim 1, characterized in that: The crushing in step S1 is performed by combining a jaw crusher and a cone crusher for multi-stage crushing, and the particle size D90 is controlled to be 1-5 mm by screening after crushing.

4. The low-quality lithium ore separation and enrichment method according to claim 1, characterized in that: In step S2, the purity of the solid sodium hydroxide is ≥95%, the ball milling is one of drum ball milling, planetary ball milling, and sand milling, the ball milling medium is one of steel balls and zirconia balls, the ball-to-material mass ratio during ball milling is (5-10):1, and the ball mill speed is 300-500 rpm.

5. The low-quality lithium ore separation and enrichment method according to claim 1, characterized in that: In step S2, nitrogen protection is introduced during the ball milling process to control the temperature in the ball milling tank to be ≤60°C.

6. The low-quality lithium ore separation and enrichment method according to claim 1, characterized in that: In step S3, a pulsating high gradient magnetic separator is used for the strong magnetic separation, with a pulsation frequency of 200-300 times / min and a slurry flow rate of 0.5-1.5 L / min.

7. The low-quality lithium ore separation and enrichment method according to claim 1, characterized in that: In step S4, the amount of sodium hexametaphosphate added is 0.5-2 kg / t of filter residue, and the amount of didecyldimethylammonium chloride added is 0.3-1 kg / t of filter residue.

8. The low-quality lithium ore separation and enrichment method according to claim 1, characterized in that: In step S4, at least one of sodium carbonate, sodium hydroxide, hydrochloric acid and sulfuric acid is used to adjust the pH, the stirring speed is 1000-1500 rpm, and the flotation is performed using a mechanical stirring flotation machine.

9. The low-quality lithium ore separation and enrichment method according to claim 1, characterized in that: After step S4, the process further includes washing the lithium concentrate: washing the lithium concentrate with deionized water for 3-5 times, filtering and drying the lithium concentrate after washing to obtain a lithium concentrate with a Li2O grade of ≥8%.

10. The low-quality lithium ore separation and enrichment method according to claim 1, characterized in that: In step S4, the flotation foam product undergoes secondary concentration, and 0.2-0.5 kg / t of flotation foam as sodium hexametaphosphate and 0.1-0.4 kg / t of flotation foam as didecyldimethylammonium chloride are added during the secondary concentration.