Method for enriching rare earth ore in low-grade apatite

Abstract

The invention provides a method for enriching rare earth ore in low-grade apatite. The method comprises the steps of ore pretreatment, graded desliming, three-time graded flotation and four-time rare earth rough concentrate concentration. According to the method, efficient mineral dissociation is achieved by optimizing the pretreatment process, an environment-friendly zinc phosphate complex is adopted to replace lead nitrate to serve as a modification activating agent, the flotation selectivity and the recovery rate of the rare earth minerals are improved by combining the synergistic effect of a specific regulator and a collecting agent, and finally the rare earth minerals with the raw ore grade being 0.15%-0.50% are enriched to the grade being 11.65%-12.55%; and the recovery rate reaches 85% or above, meanwhile, the production cost is reduced, the lead pollution risk is eliminated, and green and efficient utilization of low-grade apatite associated rare earth resources is achieved.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing technology, and specifically relates to a method for enriching rare earth minerals in low-grade apatite. Background Technology

[0002] Apatite, a globally important phosphate resource, is widely used in fertilizers, chemicals, and building materials. In recent years, with the deepening of mineral resource exploration and development, the reserves of high-grade apatite ore have gradually decreased, making the development and utilization of low-grade apatite ore a focus of industry attention. At the same time, a large amount of low-grade apatite ore contains associated rare earth elements (such as lanthanum, cerium, and neodymium). These rare earth elements possess unique physicochemical properties and are indispensable key materials for strategic emerging industries such as new energy, high-end equipment manufacturing, and electronic information, possessing extremely high economic value and strategic significance.

[0003] However, the development of rare earth resources in low-grade apatite faces two major challenges: First, the content of rare earth elements in apatite ore is low (usually ≤0.50% in the original ore grade), and they are closely associated with gangue minerals such as apatite, quartz, and feldspar in the form of fine-grained intercalation. The mineral intercalation relationship is complex, and conventional separation techniques are difficult to achieve effective separation of rare earth minerals from gangue minerals. Second, existing enrichment technologies have significant defects and are difficult to balance efficiency, cost, and environmental protection requirements.

[0004] Currently, the main methods for enriching rare earth minerals in low-grade apatite in the industry include flotation and acid leaching. Flotation is widely used due to its relatively simple operation and wide adaptability; however, traditional flotation processes are highly sensitive to ore properties, and commonly used fatty acid and hydroxamic acid collectors have poor selectivity for rare earth minerals, easily reacting with apatite, carbonates, and other minerals, making it difficult to break through 8% in rare earth concentrate grade and resulting in recovery rates generally below 70%. Furthermore, to improve selectivity, large amounts of inhibitors need to be added, increasing reagent costs and easily causing instability in the slurry system, affecting subsequent separation. Acid leaching uses strong acids (such as hydrochloric acid and sulfuric acid) to dissolve gangue minerals to enrich rare earths, but this method suffers from high acid consumption (≥50 kg of acid per ton of ore) and high production costs. Moreover, the acidic wastewater generated during leaching contains large amounts of heavy metal ions and fluoride ions, which, if not properly treated, can severely pollute soil and water bodies, posing extremely high environmental risks and failing to meet the current development requirements for green mine construction.

[0005] Furthermore, some studies have attempted to employ a combined magnetic separation-flotation process. However, since most rare earth minerals in low-grade apatite are weakly magnetic or non-magnetic, conventional magnetic separation equipment struggles to effectively separate them. Moreover, existing activation technologies largely rely on lead-containing reagents such as lead nitrate. While these can enhance the surface activity of rare earth minerals, lead is toxic and easily remains in mineral products and wastewater, posing a risk of secondary pollution. Additionally, the transportation and storage of lead reagents require strict control, increasing production management costs. Therefore, developing a method for enriching rare earth minerals in low-grade apatite that achieves efficient dissociation and selective enrichment, uses environmentally friendly modified reagents to replace toxic lead-containing reagents, and simultaneously meets low-cost and environmental requirements, is a key breakthrough for promoting the large-scale development of associated rare earth resources in low-grade apatite. This method is of significant practical importance for ensuring national rare earth resource security and improving the comprehensive utilization rate of phosphate rock resources. Summary of the Invention

[0006] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a method for enriching rare earth minerals in low-grade apatite. This method achieves efficient mineral liberation through optimized pretreatment processes, uses environmentally friendly zinc phosphate complexes to replace lead nitrate as a modifier and activator, and combines the synergistic effect of specific modifiers and collectors to improve the flotation selectivity and recovery rate of rare earth minerals. Ultimately, the rare earth minerals with a grade of 0.15% to 0.50% in the original ore are enriched to a grade of 11.65% to 12.55%, with a recovery rate of over 85%. At the same time, it reduces production costs, eliminates the risk of lead pollution, and realizes the green and efficient utilization of rare earth resources associated with low-grade apatite.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for enriching rare earth minerals in low-grade apatite, the method being as follows: S1. Ore pretreatment: Low-grade apatite ore is coarsely crushed using a jaw crusher to obtain coarse crushed products, which initially reduces the ore particle size and lays the foundation for subsequent medium crushing processes. The resulting crushed products are then fed into a cone crusher for further crushing to obtain medium crushed products, which further improve the uniformity of ore particles and avoid particle size inconsistencies during subsequent grinding. Finally, the medium crushed products are fed into a ball mill for grinding to obtain a ground slurry. This process ensures sufficient liberation of rare earth minerals and gangue minerals, while avoiding mineral mudding due to over-grinding or insufficient liberation due to under-grinding, providing high-quality raw materials for subsequent classification and flotation processes. S2, Staged Desliming: The slurry obtained from grinding in S1 is fed into a hydrocyclone for classification and desliming. During the classification process, fine mud with a particle size <0.02mm is discharged with the overflow and discarded as ore mud (testing showed that the rare earth content in this fine mud was extremely low and had no recycling value). The resulting underflow mineral particle slurry with a particle size ≥0.02mm is then introduced into the next stage of classification and flotation. Through classification and desliming, the adsorption and consumption of subsequent flotation reagents by fine mud can be significantly reduced, and the adhesion of fine mud to the mineral surface can be avoided from affecting the flotation selectivity. At the same time, the slurry fluidity is improved, creating favorable conditions for efficient classification and flotation. S3, Staged Flotation The bottom flow mineral particle slurry obtained from S2 after classification and desliming is subjected to three flotation processes to remove gangue minerals and enrich rare earth minerals. S301, First Flotation (Initial Separation): The solids mass fraction in the underflow mineral particle slurry obtained after classification and desliming in S2 is adjusted to 28%–35% to obtain the first flotation slurry. This slurry is then fed into a flotation machine for the first flotation to initially separate the siliceous gangue minerals from the apatite-rare earth mineral mixture. The specific method is as follows: First, sodium carbonate is added as a modifier to the first flotation slurry and stirred for 3 to 5 minutes. Then, sodium hydroxide is added to adjust the pH of the slurry to 8 to 9, which improves the dispersibility of the slurry and provides a stable slurry environment for the subsequent action of reagents. Subsequently, water glass, an inhibitor, is added and stirred for 5 to 8 minutes. Water glass can selectively adsorb onto the surface of siliceous gangue minerals such as quartz, enhancing their hydrophilicity and thus inhibiting the floating of siliceous gangue. Next, add a fatty acid-based collector and stir for 3 to 5 minutes. The collector can be specifically adsorbed on the surface of apatite, making the apatite hydrophobic and facilitating its subsequent separation from siliceous gangue. Finally, add the frother pine oil and stir for 1 to 2 minutes to form stable flotation foam; Then, it is sent to the flotation machine for the first flotation. The siliceous gangue floats to the surface with the foam and becomes tailings. The bottom product of the first flotation is a mixture of apatite and rare earth minerals, which completes the initial separation. S302, Second Flotation (Rare Earth Activation and Further Separation): The solids content of the bottom product (apatite-rare earth mineral mixture) from the first flotation in S301 is adjusted to 30%–40% to obtain the second flotation pulp, which enters the secondary flotation stage. The core of this stage is to further separate rare earth minerals from apatite through rare earth activation and selective inhibition. The specific method is as follows: First, a modified rare earth activator—zinc phosphate complex—is added to the second flotation slurry. The mixture is stirred for 12 to 25 minutes at a stirring speed of 600 to 800 r / min. The phosphate groups in the zinc phosphate complex can react with the La groups on the surface of rare earth minerals. 3 ⁺、Ce 3 Rare earth ions such as ⁺ form a stable chelate structure, constructing an active adsorption layer on the surface of rare earth minerals, significantly enhancing the hydrophobic transformation potential of the rare earth mineral surface; at the same time, zinc ions can undergo coordination reactions with hydroxyl groups on the surface of rare earth minerals, increasing the positive charge sites on the surface of rare earth minerals, and can also combine with interfering ions such as carbonate and fluoride ions in the slurry, reducing their contamination on the surface of rare earth minerals, creating favorable conditions for subsequent collector adsorption. Then, add type C modifier and stir for 5 min to 10 min at a stirring speed of 500 r / min to 700 r / min. Type C modifier can selectively adsorb onto the surface of apatite and form a stable chelate with calcium ions on the surface of apatite, enhancing the hydrophilicity of apatite and effectively preventing the adsorption reaction between apatite and subsequent collectors, thereby further improving the separation selectivity of rare earth minerals and apatite. Finally, type F collector is added, and the mixture is stirred for 8 to 15 minutes at a stirring speed of 600 to 800 r / min for a second flotation. Some apatite is discharged with the bottom of the tank, while rare earth minerals float with the foam, resulting in a rare earth-apatite mixed rough concentrate, thus completing further separation. The phosphate and carboxyl groups in type F collector can form strong chemical bonds with the active sites on the surface of rare earth minerals after activation by zinc phosphate complex, significantly improving the collector's adsorption capacity and selectivity for rare earth minerals. S303, Third Flotation: The solids mass fraction of the rare earth-apatite mixed rough concentrate obtained in S302 is adjusted to 30%–38% to obtain the third flotation pulp, thus completing the enrichment of rare earth minerals. The specific method is as follows: First, an auxiliary collector is added to the third flotation slurry. The auxiliary collector can further enhance the collection ability of rare earth minerals and make up for the shortcomings of the main collector in collecting low-grade minerals. Subsequently, sodium hydroxide was added as an adjuster to adjust the pH of the slurry to 9-11, and the mixture was stirred for 2-3 minutes to obtain the adjusted slurry. This pH range can further enhance the hydrophobicity of the rare earth mineral surface and inhibit the flotation of residual apatite. The adjusted slurry is fed into a flotation machine for a third flotation. Through flotation, rare earth minerals float to the surface with the froth, and the froth product obtained is the rare earth crude concentrate, while the product at the bottom of the tank is the phosphate concentrate, which is used for the recovery and utilization of phosphate resources. S4. Rare Earth Coarse and Concentrate Refining: To further improve the grade of rare earth concentrate, the rare earth rough concentrate obtained from S303 is subjected to four consecutive beneficiation processes to gradually remove residual gangue minerals and impurities. S401, First Selection: The solids mass fraction of the rare earth rough concentrate obtained in S303 is adjusted to 25%–35% to obtain a first-stage refined slurry. Water glass, an inhibitor, is added to the first-stage refined slurry and stirred for 3–5 minutes for flotation. Water glass can selectively inhibit residual siliceous gangue minerals, causing them to be discharged with the bottom of the tank. The froth product obtained from the first-stage refined slurry is a preliminarily purified rare earth concentrate. S402, Second Selection: Add water glass to the first refined foam product obtained in S401, reducing the amount of water glass used. Stir for 2 to 4 minutes and then perform flotation. By reducing the amount of water glass used, residual gangue is suppressed while avoiding excessive suppression of rare earth minerals. The residual siliceous gangue minerals are discharged with the bottom of the tank, resulting in the second refined foam product. S403, Third Selection: Add water glass, an inhibitor, to the second-selected foam product obtained in S402. Reduce the amount of water glass used, stir for 1 to 3 minutes, and then perform flotation. Trace residual impurities are discharged with the bottom of the tank, resulting in the third-selected foam product. At this point, the focus is on deep removal of trace residual impurities to ensure a steady increase in the grade of rare earth concentrate. S404, Fourth Selection: The third-stage refined froth product obtained from S403 is subjected to flotation without the addition of any reagents. Through physical separation, the last trace residual impurity particles are removed to obtain high-grade rare earth concentrate.

[0008] Preferably, the rare earth content in the low-grade apatite ore in S1 is 0.15% to 0.50%; the particle size of the coarse crushing product in S1 is <50mm; the particle size of the medium crushing product is <20mm; the ball mill speed in the grinding process is 18r / min to 22r / min; the solid mass fraction in the slurry during the grinding process is 65% to 75%; the grinding time is 30min to 60min; and the mass fraction of slurry with a particle size <0.045mm in the slurry after grinding is 80% to 90%.

[0009] Preferably, the feed pressure of the graded desliming process in S2 is 0.15MPa to 0.25MPa, the overflow pipe diameter is 50mm to 80mm, and the underflow port diameter is 20mm to 30mm.

[0010] Preferably, the fatty acid collector in S301 is oleic acid or oxidized paraffin soap; the mass ratio of the low-grade apatite ore in S1 to the sodium carbonate, water glass, fatty acid collector, and pine oil in S301 is 1t:(500-1000)g:(800-1500)g:(100-300):(30-60)g; the impeller speed of the flotation machine in the first flotation in S301 is 1800r / min-2200r / min, and the froth scraping speed is 15 times / min-20 times / min.

[0011] Preferably, the C-type modifier in S302 is citric acid or diethyl tartrate; the F-type collector is a compound of hydroxyethyl phosphoric acid and benzohydroxyxamic acid in a mass ratio of 1:2; the mass ratio of the low-grade apatite ore in S1 to the zinc phosphate complex, C-type modifier and F-type collector in S302 is 1t:(350~650)g:(150~300)g:(80~200)g; the impeller speed of the flotation machine in the second flotation in S302 is 1700r / min~2100r / min, and the froth scraping speed is 14 times / min~18 times / min. Preferably, the auxiliary collector in S303 is a mixture of oxidized paraffin soap and hydroxamic acid in a mass ratio of 1:(3-5); the mass ratio of the low-grade apatite ore in S1 to the auxiliary collector in S303 is 1t:(100-300)g; the impeller speed of the flotation machine in the third flotation in S303 is 1600r / min to 2000r / min, and the froth scraping speed is 12 times / min to 18 times / min.

[0012] Preferably, the mass ratio of the low-grade apatite ore in S1 to the water glass in S401 is 1t:(200~400)g; the impeller speed of the flotation machine in S401 is 1400r / min~1500r / min, and the froth scraping speed is 15 times / min~20 times / min.

[0013] Preferably, the mass ratio of the low-grade apatite ore in S1 to the water glass in S402 is 1t:(100~200)g; the impeller speed of the flotation machine in S402 is 1400r / min~1500r / min, and the froth scraping speed is 15 times / min~20 times / min.

[0014] Preferably, the mass ratio of the low-grade apatite ore in S1 to the water glass in S403 is 1t:(50~100)g; the impeller speed of the flotation machine in S403 is 1400r / min~1500r / min, and the froth scraping speed is 15 times / min~20 times / min.

[0015] Preferably, in the S404 flotation process, the impeller speed of the flotation machine is 1400 r / min to 1500 r / min, and the froth scraping speed is 15 times / min to 20 times / min; the rare earth grade in the high-grade rare earth concentrate is 11.65% to 12.55%.

[0016] Compared with the prior art, the present invention has the following advantages: 1. The method of this invention features high enrichment ratio and high recovery rate: This invention utilizes a pretreatment system of "coarse crushing - medium crushing - fine grinding" to precisely control the particle size of the grinding product to <0.045mm, accounting for 80% to 90%, thereby achieving full dissociation of rare earth minerals and gangue minerals, laying a high-quality raw material foundation for subsequent flotation. The core innovation lies in using zinc phosphate complex as a modified rare earth activator. Its phosphate groups form a stable chelate structure with rare earth ions, and zinc ions undergo coordination reactions with hydroxyl groups on the mineral surface, resulting in a dual effect that significantly enhances the surface activity of rare earth minerals. Combined with the selective inhibition of apatite by a type C modifier and the synergistic collection by a type F collector and auxiliary collector, the flotation selectivity of rare earth minerals is greatly enhanced. In practical applications, low-grade apatite ore with a rare earth content of 0.15% to 0.50% can be enriched to obtain high-grade rare earth concentrate with a rare earth content of 11.65% to 12.55%, and the rare earth recovery rate can be stably maintained at over 85%. Compared with the traditional lead nitrate activation process, the enrichment effect is 15% to 20% more stable, effectively solving the industry pain points of "difficulty in achieving high grades and large fluctuations in recovery rate" in traditional processes.

[0017] 2. This invention completely eliminates the risk of lead pollution and has significant environmental performance: This invention abandons the toxic lead nitrate activator relied upon in traditional processes and innovatively uses zinc phosphate complex as a modified activator. This activator is a mature industrial application, non-toxic, and leaves no heavy metal residue. It not only avoids lead residue in rare earth concentrates (tested to have a final lead content ≤0.001%, far below the ≤0.01% limit in the "Rare Earth Concentrates" (GB / T 23591-2022), but also completely solves the pollution problem of lead-containing wastewater. Simultaneously, the flotation wastewater generated during the process only requires simple sedimentation and filtration treatment to achieve a recycling rate of over 85%. The wastewater discharge indicators fully comply with the national "Emission Standard for Pollutants from Nonferrous Metals Industry" (GB 25465-2010), eliminating the need for additional high-cost wastewater treatment facilities. This provides a feasible path for the green development of low-grade apatite-associated rare earth resources, helping mining enterprises achieve the goal of "zero pollution and low emissions" in green mine construction.

[0018] 3. This invention achieves dual optimization of production costs and management difficulty: In terms of cost control, on the one hand, the raw material cost of zinc phosphate complex is basically the same as that of traditional lead nitrate. Although the amount used is 10% to 15% higher than that of lead nitrate composite system, the overall economic benefits are balanced by reducing the amount of inhibitor (20% to 25% lower than traditional process) and increasing the recovery rate of phosphate concentrate (the grade of bottom phosphate concentrate can reach more than 30%, which can be directly sold as phosphate rock product). The comprehensive processing cost per ton of ore does not increase significantly. On the other hand, the process adopts general mineral processing equipment such as jaw crusher, cone crusher, ball mill, hydrocyclone, and conventional flotation machine. There is no need to add high-end special equipment. The equipment investment cost is reduced by 30% to 40% compared with customized process. Moreover, the equipment is easy to operate and maintain, reducing the equipment operation and maintenance costs of enterprises. In terms of management, zinc phosphate complexes are non-toxic and do not require special transportation and storage in accordance with the "Regulations on the Safety Management of Hazardous Chemicals". This eliminates the need for investment in dedicated hazardous materials storage warehouses and safety protection facilities, while also reducing management links such as safety management training and emergency drills. The safety management cost per ton of ore is reduced by 15 to 20 yuan, and the production management process is greatly simplified.

[0019] 4. Synergistic Effect of the Invention on Reagents, Ensuring Stable Product Quality: This invention constructs a synergistic system of "zinc phosphate complex - C-type modifier," forming a unique technical advantage: The hydroxyl groups of the C-type modifier can form a coordination structure with zinc ions in the zinc phosphate complex, further enhancing the adsorption stability of zinc ions on the surface of rare earth minerals, avoiding the loss of activity caused by the free flow of zinc ions in the slurry, and increasing the retention rate of active sites on the surface of rare earth minerals by more than 25%; At the same time, the C-type modifier can chelate impurity ions such as iron and aluminum in the slurry (chelation efficiency of more than 90%), reducing the interference of impurity ions on the zinc phosphate complex, ensuring the stable existence of active sites on the surface of rare earth minerals, and providing a guarantee for the precise adsorption of subsequent F-type collectors and auxiliary collectors. This synergistic effect effectively avoids the limitations of single-agent action, ensuring that the final rare earth concentrate grade is consistently above 11.65%, with grade fluctuations controlled within ±0.5%. This solves the problem of product quality fluctuations caused by the instability of the slurry system in traditional processes, and meets the stringent requirements of downstream rare earth smelting enterprises for the stability of raw material quality.

[0020] 5. This invention enables comprehensive resource utilization and enhances economic value: While enriching rare earth resources, this invention optimizes the design of the graded flotation and beneficiation processes to achieve a phosphate concentrate grade of over 30% produced from the bottom of the flotation tank. This meets the Class II phosphate concentrate standard in the "Phosphate Rock and Phosphate Concentrate" (GB / T 18682-2020), allowing it to be directly sold as a raw material for phosphate chemicals. This achieves "dual recovery and dual utilization" of apatite and rare earth resources. Compared to traditional processes that only recover a single resource, the economic benefit per ton of ore for enterprises increases by 30% to 40%. This not only improves the resource utilization rate of low-grade apatite ore but also opens up diversified profit channels for enterprises, enhancing their market competitiveness. It has significant demonstrative significance for promoting the "zero-waste" comprehensive utilization of low-grade mineral resources.

[0021] The present invention will be further described in detail below with reference to the embodiments. Detailed Implementation

[0022] Example 1 The source of the low-grade apatite ore in this example is the Haoteger rare earth mining area in Mongolia. The main target mineral is rare earth, and the beneficial minerals are apatite, mica, etc. The rare earth minerals are basically hosted in the apatite minerals. The ore composition is relatively complex and contains a lot of ore slime.

[0023] The method for enriching rare earth minerals in low-grade apatite in this embodiment is as follows: S1. Ore pretreatment: Low-grade apatite ore with a rare earth content of 0.50% is coarsely crushed using a jaw crusher to obtain a coarse crushed product with a particle size <50mm, initially reducing the ore particle size and laying the foundation for subsequent medium crushing. The resulting coarse crushed product is then fed into a cone crusher for further crushing, obtaining a medium crushed product with a particle size <20mm, further improving the uniformity of ore particles and avoiding particle size inconsistencies during subsequent grinding. Finally, the medium crushed product is fed into a ball mill for grinding at a speed of 18 r / min, with a solids mass fraction of 65% in the slurry, and a grinding time of 30 min, resulting in a ground slurry with a particle size <0.045mm mass fraction of 80%. This ensures sufficient liberation of rare earth minerals and gangue minerals, while avoiding mineral mudding due to over-grinding or insufficient liberation due to under-grinding, providing high-quality raw materials for subsequent classification and flotation processes. S2, Staged Desliming: The slurry obtained from grinding in step S1 is fed into a hydrocyclone for classification and desliming. The hydrocyclone has a feed pressure of 0.15 MPa, an overflow pipe diameter of 50 mm, and an underflow port diameter of 20 mm. During classification, fine mud with a particle size <0.02 mm is discharged with the overflow and discarded as ore slime (tests show that the rare earth content in this fine mud is extremely low and has no recycling value). The resulting underflow mineral particle slurry with a particle size ≥0.02 mm is then introduced into the next stage of classification and flotation. Classification and desliming significantly reduces the adsorption and consumption of subsequent flotation reagents by fine mud, prevents fine mud from adhering to the mineral surface and affecting flotation selectivity, and improves slurry fluidity, creating favorable conditions for efficient classification and flotation. S3, Staged Flotation The bottom flow mineral particle slurry obtained from S2 after classification and desliming is subjected to three flotation processes to remove gangue minerals and enrich rare earth minerals. S301, First Flotation (Initial Separation): The solids mass fraction of the bottom flow mineral particle slurry obtained after classification and desliming in S2 is adjusted to 35% to obtain the first flotation slurry, which is then fed into a flotation machine for the first flotation to initially separate the siliceous gangue minerals and the apatite-rare earth mineral mixture. The specific method is as follows: First, sodium carbonate is added as a modifier to the first flotation slurry and stirred for 3 minutes. Then, sodium hydroxide is added to adjust the pH of the slurry to 8, which improves the dispersibility of the slurry and provides a stable slurry environment for the subsequent action of reagents. Subsequently, water glass, an inhibitor, was added and stirred for 5 minutes. Water glass can selectively adsorb onto the surface of siliceous gangue minerals such as quartz, enhancing their hydrophilicity and thus inhibiting the floating of siliceous gangue. Next, add a fatty acid collector (oleic acid) and stir for 5 minutes. The collector can be specifically adsorbed on the surface of apatite, making the apatite hydrophobic and facilitating its subsequent separation from siliceous gangue. Finally, add the frother pine oil and stir for 1 minute to form stable flotation foam; Then, it is fed into a flotation machine for the first flotation. The impeller speed of the flotation machine is 1800 r / min to 2200 r / min, and the froth scraping speed is 15 times / min. The siliceous gangue floats to the surface with the froth and becomes tailings. The bottom product of the first flotation is a mixture of apatite and rare earth minerals, which completes the initial separation. The mass ratio of the low-grade apatite ore in S1 to the sodium carbonate, water glass, fatty acid collector, and pine oil in S301 is 1t:500g:800g:300g:30g; S302, Second Flotation (Rare Earth Activation and Further Separation): The solids content of the bottom product (apatite-rare earth mineral mixture) from the first flotation in S301 is adjusted to 30% to obtain the second flotation pulp, which enters the secondary flotation stage. The core of this stage is to further separate rare earth minerals from apatite through rare earth activation and selective inhibition. The specific method is as follows: First, a modified rare earth activator—zinc phosphate complex—is added to the second flotation slurry, and the mixture is stirred for 12 minutes at a stirring speed of 600 r / min. The phosphate groups in the zinc phosphate complex can react with the La groups on the surface of rare earth minerals. 3 ⁺、Ce 3 Rare earth ions such as ⁺ form a stable chelate structure, constructing an active adsorption layer on the surface of rare earth minerals, significantly enhancing the hydrophobic transformation potential of the rare earth mineral surface; at the same time, zinc ions can undergo coordination reactions with hydroxyl groups on the surface of rare earth minerals, increasing the positive charge sites on the surface of rare earth minerals, and can also combine with interfering ions such as carbonate and fluoride ions in the slurry, reducing their contamination on the surface of rare earth minerals, creating favorable conditions for subsequent collector adsorption. Zinc phosphate complex was purchased commercially from Antery; Then, add type C modifier (citric acid) and stir for 5 minutes at a stirring speed of 500 r / min. Type C modifier can selectively adsorb onto the surface of apatite and form a stable chelate with calcium ions on the surface of apatite, enhancing the hydrophilicity of apatite and effectively preventing apatite from undergoing an adsorption reaction with subsequent collectors, thereby further improving the separation selectivity of rare earth minerals and apatite. Finally, type F collector (a mixture of hydroxyethyl phosphoric acid and benzoic acid in a mass ratio of 1:2) is added, and the mixture is stirred for 15 minutes at a stirring speed of 600 r / min for a second flotation. In the second flotation, the impeller speed of the flotation machine is 1700 r / min, and the froth scraping speed is 18 times / min. Some apatite is discharged with the bottom of the tank, while rare earth minerals float with the froth, resulting in a rare earth-apatite mixed rough concentrate, thus completing further separation. The phosphate and carboxyl groups in type F collector can form strong chemical bonds with the active sites on the surface of rare earth minerals after activation by zinc phosphate complex, significantly improving the adsorption capacity and selectivity of the collector for rare earth minerals. The mass ratio of the low-grade apatite ore in S1 to the zinc phosphate complex, type C modifier, and type F collector in S302 is 1t:350g:300g:80g. S303, Third Flotation: The solids mass fraction of the rare earth-apatite mixed rough concentrate obtained in S302 was adjusted to 30% to obtain the third flotation pulp, thus completing the enrichment of rare earth minerals. The specific method is as follows: First, an auxiliary collector (a mixture of oxidized paraffin soap and hydroxamic acid in a mass ratio of 1:3) is added to the third flotation pulp. The auxiliary collector can further enhance the collection ability of rare earth minerals and make up for the shortcomings of the main collector in collecting low-grade minerals. Subsequently, sodium hydroxide was added as an adjuster to adjust the pH of the slurry to 9, and the mixture was stirred for 2 minutes to obtain the adjusted slurry. This pH range can further enhance the hydrophobicity of the rare earth mineral surface and inhibit the flotation of residual apatite. The adjusted slurry is fed into a flotation machine for a third flotation. The impeller speed of the flotation machine is 1600 r / min and the froth scraping speed is 12 times / min. Through the flotation process, rare earth minerals float to the surface with the froth. The froth product obtained is the rare earth crude concentrate, and the product at the bottom of the tank is the phosphate concentrate, which is used for the recovery and utilization of phosphate resources. The mass ratio of the low-grade apatite ore in S1 to the auxiliary collector in S303 is 1t:100g; S4. Rare Earth Coarse and Concentrate Refining: To further improve the grade of rare earth concentrate, the rare earth rough concentrate obtained from S303 is subjected to four consecutive beneficiation processes to gradually remove residual gangue minerals and impurities. S401, First Selection: The solids content of the rare earth rough concentrate obtained in S303 is adjusted to 25% to obtain the first-stage refined slurry. Water glass, an inhibitor, is added to the first-stage refined slurry, and the mixture is stirred for 3 minutes. Flotation is then performed with the flotation machine impeller rotating at 1450 r / min and the froth scraping speed at 18 times / min. The water glass selectively inhibits residual siliceous gangue minerals, causing them to be discharged with the bottom of the tank. The resulting froth product from the first-stage refined process is a preliminarily purified rare earth concentrate. The mass ratio of the low-grade apatite ore in S1 to the water glass in S401 is 1t:200g; S402, Second Selection: Water glass is added to the first refined foam product obtained in S401, but the amount of water glass is reduced. After stirring for 2 minutes, flotation is carried out. The impeller speed of the flotation machine is 1450 r / min and the froth scraping speed is 18 times / min. By reducing the amount of water glass, the residual gangue is suppressed while avoiding excessive suppression of rare earth minerals. The residual siliceous gangue minerals are discharged with the bottom of the tank, and the second refined foam product is obtained. The mass ratio of the low-grade apatite ore in S1 to the water glass in S402 is 1t:100g; S403, Third Selection: Add water glass, an inhibitor, to the second-selected froth product obtained in S402. Reduce the amount of water glass used, stir for 1 minute, and then perform flotation. The impeller speed of the flotation machine is 1450 r / min, and the froth scraping speed is 18 times / min. Trace residual impurities are discharged with the bottom of the tank, resulting in the third-selected froth product. At this point, the focus is on deep removal of trace residual impurities to ensure a steady increase in the grade of rare earth concentrate. The mass ratio of the low-grade apatite ore in S1 to the water glass in S403 is 1t:50g; S404, Fourth Selection: The froth product obtained from the third purification in S403 was directly subjected to flotation without the addition of any reagents. The impeller speed of the flotation machine was 1450 r / min, and the froth scraping speed was 18 times / min. Through physical separation, the last trace residual impurity particles were removed, yielding a high-grade rare earth concentrate with a rare earth content of 11.65%. The statistical recovery rate was 86.95%, and the final lead content of the rare earth concentrate was found to be 0.001%.

[0024] Example 2 The low-grade apatite ore in this example comes from the Zhuopan rare earth mine in Yongping, Yunnan. The main rare earth carrier mineral is apatite, followed by monazite and epidote. The average rare earth content in apatite is 1.9%, accounting for 85% of the total rare earth content in the ore. The apatite contains an average of 35.30% P2O5, 58.85% CaO, and 3.60% F, and belongs to the fluorapatite family.

[0025] The method for enriching rare earth minerals in low-grade apatite in this embodiment is as follows: S1. Ore pretreatment: Low-grade apatite ore with a rare earth content of 0.35% was coarsely crushed using a jaw crusher to obtain a coarse crushed product with a particle size <50mm. This coarse product was then fed into a cone crusher for further crushing to obtain a medium crushed product with a particle size <20mm. Finally, the medium crushed product was fed into a ball mill for grinding. The ball mill speed was 22 r / min, the solids mass fraction in the slurry was 75%, and the grinding time was 60 min, resulting in a ground slurry with a particle size <0.045mm mass fraction of 90%. S2, Staged Desliming: The slurry obtained after grinding in S1 is fed into a hydrocyclone for classification and desliming. The feed pressure of the hydrocyclone is 0.25 MPa, the overflow pipe diameter is 80 mm, and the underflow port diameter is 30 mm. During the classification process, fine mud with a particle size <0.02 mm is discharged with the overflow and discarded as sludge (it was found that the rare earth content in this fine mud is extremely low and has no recycling value). The resulting underflow mineral particle slurry with a particle size ≥0.02 mm is then fed into the next stage of classification and flotation. S3, Classification Flotation: The bottom flow mineral particle slurry obtained from S2 after classification and desliming is subjected to three flotation processes to remove gangue minerals and enrich rare earth minerals. S301, First Flotation (Initial Separation): The solids mass fraction of the bottom flow mineral particle slurry obtained after classification and desliming in S2 is adjusted to 28% to obtain the first flotation slurry, which is then fed into a flotation machine for the first flotation to initially separate the siliceous gangue minerals and the apatite-rare earth mineral mixture. The specific method is as follows: First, sodium carbonate, a modifier, is added to the first flotation slurry and stirred for 5 minutes. Then, sodium hydroxide is added to adjust the pH of the slurry to 9. Then, add the inhibitor water glass and stir for 8 minutes; Next, add the fatty acid collector (oxidized paraffin soap) and stir for 3 minutes; Finally, add the frother pine oil and stir for 2 minutes to form stable flotation foam; Then, it is sent to a flotation machine for the first flotation. The impeller speed of the flotation machine is 2200 r / min and the froth scraping speed is 20 times / min. The siliceous gangue floats to the surface with the froth and becomes tailings. The bottom product of the first flotation is a mixture of apatite and rare earth minerals, which completes the initial separation. The mass ratio of the low-grade apatite ore in S1 to the sodium carbonate, water glass, fatty acid collector, and pine oil in S301 is 1t:1000g:1500g:100g:60g; S302, Second Flotation (Rare Earth Activation and Further Separation): The solids content of the bottom product (apatite-rare earth mineral mixture) from the first flotation in S301 is adjusted to 40% to obtain the second flotation pulp, thus completing the further separation of rare earth minerals and apatite. The specific method is as follows: First, a modified rare earth activator—zinc phosphate complex—is added to the second flotation slurry, and the mixture is stirred for 25 minutes at a stirring speed of 800 r / min. Zinc phosphate complex was purchased commercially from Antery; Then, add type C modifier (diethyl tartrate) and stir for 10 minutes at a stirring speed of 700 r / min; Finally, type F collector (a mixture of hydroxyethyl phosphoric acid and benzoic acid in a mass ratio of 1:2) was added, and the mixture was stirred for 8 minutes at a stirring speed of 800 r / min for a second flotation. In the second flotation, the impeller speed of the flotation machine was 2100 r / min, and the froth scraping speed was 14 times / min. Some apatite was discharged with the bottom of the tank, while rare earth minerals floated with the froth, resulting in a rare earth-apatite mixed rough concentrate, thus completing further separation. The mass ratio of the low-grade apatite ore described in S1 to the zinc phosphate complex, type C modifier, and type F collector described in S302 is 1t:650g:150g:200g; S303, Third Flotation: The solids mass fraction of the rare earth-apatite mixed rough concentrate obtained in S302 was adjusted to 38% to obtain the third flotation pulp, thus completing the enrichment of rare earth minerals. The specific method is as follows: First, an auxiliary collector (a mixture of oxidized paraffin soap and hydroxamic acid in a mass ratio of 1:5) is added to the third flotation pulp. Subsequently, sodium hydroxide was added as an adjuster to adjust the pH of the slurry to 11, and the mixture was stirred for 3 minutes to obtain the adjusted slurry. The adjusted slurry is fed into a flotation machine for the third flotation. The impeller speed of the flotation machine is 2000 r / min and the froth scraping speed is 18 times / min. Through the flotation process, rare earth minerals float to the surface with the froth. The froth product obtained is the rare earth crude concentrate, and the product at the bottom of the tank is the phosphate concentrate, which is used for the recovery and utilization of phosphate resources. The mass ratio of the low-grade apatite ore in S1 to the auxiliary collector in S303 is 1t:300g; S4. Rare Earth Coarse and Concentrate Refining: To further improve the grade of rare earth concentrate, the rare earth rough concentrate obtained from S303 is subjected to four consecutive beneficiation processes to gradually remove residual gangue minerals and impurities. S401, First Selection: The solids mass fraction of the rare earth rough concentrate obtained in S303 is adjusted to 35% to obtain the first-stage refined slurry. Water glass, an inhibitor, is added to the first-stage refined slurry, and the mixture is stirred for 5 minutes. Flotation is then performed with the flotation machine impeller rotating at 1500 r / min and the froth scraping speed at 15 times / min. The water glass selectively inhibits residual siliceous gangue minerals, causing them to be discharged with the bottom of the tank. The resulting froth product from the first-stage refined process is a preliminarily purified rare earth concentrate. The mass ratio of the low-grade apatite ore in S1 to the water glass in S401 is 1t:400g; S402, Second Selection: Water glass is added to the first refined foam product obtained in S401, but the amount of water glass is reduced. After stirring for 4 minutes, flotation is carried out. The impeller speed of the flotation machine is 1500 r / min and the froth scraping speed is 15 times / min. By reducing the amount of water glass, the residual gangue is suppressed while avoiding excessive suppression of rare earth minerals. The residual siliceous gangue minerals are discharged with the bottom of the tank, and the second refined foam product is obtained. The mass ratio of the low-grade apatite ore in S1 to the water glass in S402 is 1t:200g; S403, Third Selection: Add water glass, an inhibitor, to the second-selected froth product obtained in S402. Reduce the amount of water glass used, stir for 3 minutes, and then perform flotation. The impeller speed of the flotation machine is 1500 r / min, and the froth scraping speed is 15 times / min. Trace residual impurities are discharged with the bottom of the tank, resulting in the third-selected froth product. At this point, the main focus is on the deep removal of trace residual impurities to ensure a steady increase in the grade of rare earth concentrate. The mass ratio of the low-grade apatite ore in S1 to the water glass in S403 is 1t:100g; S404, Fourth Selection: The froth product obtained from the third purification in S403 was directly subjected to flotation without the addition of any reagents. The flotation machine impeller speed was 1500 r / min, and the froth scraping speed was 15 times / min. Through physical separation, the last trace residual impurity particles were removed, yielding a high-grade rare earth concentrate with a rare earth content of 12.55%. The statistical recovery rate was 85.25%. Testing revealed that the final rare earth concentrate had a lead content of 0.001%.

[0026] Example 3 The source of the low-grade apatite ore in this embodiment is: Gezhongwu, Xinhua Phosphate Mine, Zhijin, Guizhou. Rare earth elements are mainly hosted in collophane, and associated minerals are quartz, dolomite, magnesium calcite and calcite, etc.

[0027] The method for enriching rare earth minerals in low-grade apatite in this embodiment is as follows: S1. Ore pretreatment: Low-grade apatite ore with a rare earth content of 0.15% was coarsely crushed using a jaw crusher to obtain a coarse crushed product with a particle size <50mm. This coarse crushed product was then fed into a cone crusher for further crushing to obtain a medium crushed product with a particle size <20mm. Finally, the medium crushed product was fed into a ball mill for grinding at a speed of 20 r / min. The solids content of the slurry during grinding was 70%, and the grinding time was 40 min, resulting in a ground slurry with a particle size <0.045mm comprising 85% of the slurry. S2, Staged Desliming: The slurry obtained after grinding in S1 is fed into a hydrocyclone for classification and desliming. The feed pressure of the hydrocyclone is 0.20 MPa, the overflow pipe diameter is 60 mm, and the underflow port diameter is 25 mm. During the classification process, fine mud with a particle size <0.02 mm is discharged with the overflow and discarded as sludge (it was found that the rare earth content in this fine mud is extremely low and has no recycling value). The resulting underflow mineral particle slurry with a particle size ≥0.02 mm is then fed into the next stage of classification and flotation. S3, Classification Flotation: The bottom flow mineral particle slurry obtained from S2 after classification and desliming is subjected to three flotation processes to remove gangue minerals and enrich rare earth minerals. S301, First Flotation (Initial Separation): The solids mass fraction of the bottom flow mineral particle slurry obtained after classification and desliming in S2 is adjusted to 32% to obtain the first flotation slurry, which is then fed into a flotation machine for the first flotation to initially separate the siliceous gangue minerals and the apatite-rare earth mineral mixture. The specific method is as follows: First, sodium carbonate, a modifier, is added to the first flotation slurry and stirred for 4 minutes. Then, sodium hydroxide is added to adjust the pH of the slurry to 8. Then, add the inhibitor water glass and stir for 6 minutes; Next, add the fatty acid collector (oleic acid) and stir for 4 minutes; Finally, add the frother pine oil and stir for 1.5 minutes to form stable flotation foam; Then, it is fed into a flotation machine for the first flotation. The impeller speed of the flotation machine is 2000 r / min and the froth scraping speed is 18 times / min. The siliceous gangue floats to the surface with the froth and becomes tailings. The bottom product of the first flotation is a mixture of apatite and rare earth minerals, which completes the initial separation. The mass ratio of the low-grade apatite ore in S1 to the sodium carbonate, water glass, fatty acid collector, and pine oil in S301 is 1t:800g:1000g:200g:40g; S302, Second Flotation (Rare Earth Activation and Further Separation): The solids mass fraction of the bottom product (apatite-rare earth mineral mixture) from the first flotation in S301 is adjusted to 35% to obtain the second flotation pulp, which enters the secondary flotation stage to further separate the rare earth minerals from the apatite. The specific method is as follows: First, a modified rare earth activator—zinc phosphate complex—is added to the second flotation slurry, and the mixture is stirred for 20 minutes at a stirring speed of 700 r / min. Zinc phosphate complex was purchased commercially from Antery; Then, add type C modifier (diethyl tartrate) and stir for 8 minutes at a stirring speed of 600 r / min; Finally, type F collector (a mixture of hydroxyethyl phosphoric acid and benzoic acid in a mass ratio of 1:2) is added, and the mixture is stirred for 10 minutes at a stirring speed of 700 r / min for a second flotation. In the second flotation, the impeller speed of the flotation machine is 1900 r / min, and the froth scraping speed is 15 times / min. Some apatite is discharged with the bottom of the tank, while rare earth minerals float with the froth, resulting in a rare earth-apatite mixed rough concentrate, completing further separation. The mass ratio of the low-grade apatite ore in S1 to the zinc phosphate complex, type C modifier, and type F collector in S302 is 1t:450g:250g:120g. S303, Third Flotation: The solids mass fraction of the rare earth-apatite mixed rough concentrate obtained in S302 was adjusted to 35% to obtain the third flotation pulp, thus completing the enrichment of rare earth minerals. The specific method is as follows: First, an auxiliary collector (a mixture of oxidized paraffin soap and hydroxamic acid in a mass ratio of 1:4) is added to the third flotation pulp. Subsequently, sodium hydroxide was added as an adjuster to adjust the pH of the slurry to 10, and the mixture was stirred for 2.5 minutes to obtain the adjusted slurry. The adjusted slurry is fed into a flotation machine for the third flotation. The impeller speed of the flotation machine is 1800 r / min and the froth scraping speed is 16 times / min. Through the flotation process, rare earth minerals float to the surface with the froth. The froth product obtained is the rare earth crude concentrate, and the product at the bottom of the tank is the phosphate concentrate, which is used for the recovery and utilization of phosphate resources. The mass ratio of the low-grade apatite ore in S1 to the auxiliary collector in S303 is 1t:200g; S4. Rare Earth Coarse and Concentrate Refining: To further improve the grade of rare earth concentrate, the rare earth rough concentrate obtained from S303 is subjected to four consecutive beneficiation processes to gradually remove residual gangue minerals and impurities. S401, First Selection: The solids content of the rare earth rough concentrate obtained in S303 is adjusted to 30% to obtain the first-stage refined slurry. Water glass, an inhibitor, is added to the first-stage refined slurry, and the mixture is stirred for 4 minutes. Flotation is then performed with the flotation machine impeller rotating at 1400 r / min and the froth scraping speed at 20 times / min. The water glass selectively inhibits residual siliceous gangue minerals, causing them to be discharged with the bottom of the tank. The resulting froth product from the first-stage refined process is a preliminarily purified rare earth concentrate. The mass ratio of the low-grade apatite ore in S1 to the water glass in S401 is 1t:300g; S402, Second Selection: Water glass is added to the first refined foam product obtained in S401, but the amount of water glass is reduced. After stirring for 3 minutes, flotation is carried out. The impeller speed of the flotation machine is 1400 r / min and the froth scraping speed is 20 times / min. By reducing the amount of water glass, the residual gangue is suppressed while avoiding excessive suppression of rare earth minerals. The residual siliceous gangue minerals are discharged with the bottom of the tank, and the second refined foam product is obtained. The mass ratio of the low-grade apatite ore in S1 to the water glass in S402 is 1t:150g; S403, Third Selection: Add water glass, an inhibitor, to the second-selected froth product obtained in S402. Reduce the amount of water glass used, stir for 2 minutes, and then perform flotation. The impeller speed of the flotation machine is 1400 r / min, and the froth scraping speed is 20 times / min. Trace residual impurities are discharged with the bottom of the tank, resulting in the third-selected froth product. At this point, the main focus is on the deep removal of trace residual impurities to ensure a steady increase in the grade of rare earth concentrate. The mass ratio of the low-grade apatite ore in S1 to the water glass in S403 is 1t:80g; S404, Fourth Selection: The froth product obtained from the third purification in S403 was directly subjected to flotation without the addition of any reagents. The flotation machine impeller speed was 1400 r / min, and the froth scraping speed was 20 times / min. Through physical separation, the last trace residual impurity particles were removed, yielding a high-grade rare earth concentrate with a rare earth content of 12.00%. The statistical recovery rate was 86.50%. Testing revealed that the final rare earth concentrate contained 0.002% lead.

[0028] The method of this invention features high enrichment ratio and high recovery rate: Through a pretreatment system of "coarse crushing-medium crushing-fine grinding," the particle size of the grinding product is precisely controlled to be <0.045mm, accounting for 80%–90%, achieving full liberation of rare earth minerals and gangue minerals, laying a high-quality raw material foundation for subsequent flotation. The core innovation lies in using zinc phosphate complex as a modified rare earth activator. Its phosphate groups form a stable chelate structure with rare earth ions, and zinc ions undergo coordination reactions with hydroxyl groups on the mineral surface, significantly enhancing the surface activity of rare earth minerals through this dual effect. Combined with the selective inhibition of apatite by a type C modifier and the synergistic collection by a type F collector and auxiliary collector, the flotation selectivity of rare earth minerals is greatly enhanced. In practical applications, low-grade apatite ore with a rare earth content of 0.15% to 0.50% can be enriched to obtain high-grade rare earth concentrate with a rare earth content of 11.65% to 12.55%, and the rare earth recovery rate can be stably maintained at over 85%. Compared with the traditional lead nitrate activation process, the enrichment effect is 15% to 20% more stable, effectively solving the industry pain points of "difficulty in achieving high grades and large fluctuations in recovery rate" in traditional processes.

[0029] This invention completely eliminates the risk of lead pollution and has significant environmental performance: It abandons the toxic lead nitrate activator relied upon in traditional processes and innovatively uses zinc phosphate complex as a modified activator. This activator is a mature industrial application, non-toxic, and leaves no heavy metal residue. This not only avoids lead residue in rare earth concentrates (tested to have a final lead content ≤0.001%, far below the ≤0.01% limit in the "Rare Earth Concentrates" (GB / T 23591-2022), but also completely solves the pollution problem of lead-containing wastewater. Simultaneously, the flotation wastewater generated during the process only requires simple sedimentation and filtration treatment to achieve a recycling rate of over 85%. The wastewater discharge indicators fully comply with the national "Emission Standard of Pollutants for Nonferrous Metals Industry" (GB 25465-2010), eliminating the need for additional high-cost wastewater treatment facilities. This provides a feasible path for the green development of low-grade apatite-associated rare earth resources, helping mining enterprises achieve the goal of "zero pollution and low emissions" in green mine construction.

[0030] This invention achieves dual optimization of production costs and management difficulty: In terms of cost control, on the one hand, the raw material cost of zinc phosphate complex is basically the same as that of traditional lead nitrate. Although the amount used is 10% to 15% higher than that of lead nitrate composite system, the overall economic benefits are balanced by reducing the amount of inhibitor (20% to 25% lower than traditional process) and increasing the recovery rate of phosphate concentrate (the grade of bottom phosphate concentrate can reach more than 30%, which can be sold directly as phosphate rock product). The comprehensive processing cost per ton of ore does not increase significantly. On the other hand, the process adopts general mineral processing equipment such as jaw crusher, cone crusher, ball mill, hydrocyclone, and conventional flotation machine. There is no need to add high-end special equipment. The equipment investment cost is reduced by 30% to 40% compared with customized process. Moreover, the equipment is easy to operate and maintain, reducing the equipment operation and maintenance costs of enterprises. In terms of management, zinc phosphate complexes are non-toxic and do not require special transportation and storage in accordance with the "Regulations on the Safety Management of Hazardous Chemicals". This eliminates the need for investment in dedicated hazardous materials storage warehouses and safety protection facilities, while also reducing management links such as safety management training and emergency drills. The safety management cost per ton of ore is reduced by 15 to 20 yuan, and the production management process is greatly simplified.

[0031] This invention features a synergistic effect of reagents, ensuring stable product quality: The invention constructs a synergistic system of "zinc phosphate complex - C-type modifier," forming a unique technical advantage: The hydroxyl groups of the C-type modifier can form a coordination structure with zinc ions in the zinc phosphate complex, further enhancing the adsorption stability of zinc ions on the surface of rare earth minerals, avoiding the loss of activity caused by the free flow of zinc ions in the slurry, and increasing the retention rate of active sites on the surface of rare earth minerals by more than 25%; simultaneously, the C-type modifier can chelate impurity ions such as iron and aluminum in the slurry (chelation efficiency of over 90%), reducing the interference of impurity ions on the zinc phosphate complex, ensuring the stable existence of active sites on the surface of rare earth minerals, and providing a guarantee for the precise adsorption of subsequent F-type collectors and auxiliary collectors. This synergistic effect effectively avoids the limitations of single-agent action, ensuring that the final rare earth concentrate grade is consistently above 11.65%, with grade fluctuations controlled within ±0.5%. This solves the problem of product quality fluctuations caused by the instability of the slurry system in traditional processes, and meets the stringent requirements of downstream rare earth smelting enterprises for the stability of raw material quality.

[0032] This invention enables comprehensive resource utilization and enhances economic value. While enriching rare earth resources, the optimized design of the graded flotation and beneficiation processes ensures that the grade of the phosphate concentrate produced from the bottom of the flotation tank reaches over 30%, meeting the Class II phosphate concentrate standard in the "Phosphate Rock and Phosphate Concentrate" (GB / T 18682-2020). This concentrate can be directly sold as a raw material for phosphate chemicals, achieving "dual recovery and dual utilization" of apatite and rare earth resources. Compared to traditional processes that only recover a single resource, the economic benefit per ton of ore for enterprises increases by 30%–40%. This not only improves the resource utilization rate of low-grade apatite ore but also opens up diversified profit channels for enterprises, enhancing their market competitiveness. It has significant demonstrative significance for promoting the "zero-waste" comprehensive utilization of low-grade mineral resources.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for enriching rare earth ores in low-grade apatite, characterized by, The method comprises the following steps: S1, ore pretreatment: Coarse crushing of low-grade apatite ore to obtain a coarse crushing product, crushing the obtained crushing product to obtain a medium crushing product, and performing grinding treatment on the obtained medium crushing product to obtain a ground ore slurry; S2, classification desliming: The ground ore slurry obtained in S1 is subjected to classification desliming treatment, and fine mud with a particle size of less than 0.02 mm is discharged as overflow and discarded as mud, to obtain a bottom flow mineral particle slurry after classification desliming; S3, classification flotation The bottom flow mineral particle slurry after classification desliming obtained in S2 is subjected to three times of flotation in turn to realize the removal of gangue minerals and the enrichment of rare earth minerals; S301, first flotation: The solid mass fraction of the bottom flow mineral particle slurry obtained in S2 is adjusted to 28% to 35% to obtain a first flotation slurry, and the first flotation is performed to preliminarily separate siliceous gangue minerals from apatite-rare earth mineral mixture, and the specific method is as follows: Sodium carbonate is added to the first flotation slurry, stirred for 3 min to 5 min, then sodium hydroxide is added, the pH of the slurry is adjusted to 8 to 9, then water glass is added, stirred for 5 min to 8 min, then a fatty acid collector is added, stirred for 3 min to 5 min, then pine oil is added, stirred for 1 min to 2 min, to form a flotation froth, and the first flotation is performed, and the siliceous gangue floats up as tailings, and the first flotation tank bottom product is the apatite-rare earth mineral mixture, and the preliminary separation is completed; S302, second flotation: The solid mass fraction of the slurry of the first flotation tank bottom product in S301 is adjusted to 30% to 40% to obtain a second flotation slurry, and the further separation of rare earth minerals from apatite is completed, and the specific method is as follows: Zinc phosphate complex is added to the second flotation slurry, stirred at a stirring speed of 600 r / min to 800 r / min for 12 min to 25 min, then C-type modifier is added, stirred at a stirring speed of 500 r / min to 700 r / min for 5 min to 10 min, then F-type collector is added, stirred at a stirring speed of 600 r / min to 800 r / min for 8 min to 15 min, and the second flotation is performed, part of the apatite is discharged from the tank bottom, and the rare earth minerals float up as froth, to obtain a rare earth-apatite mixed rough concentrate, and the further separation is completed; S303, third flotation: The solid mass fraction of the rare earth-apatite mixed rough concentrate slurry obtained in S302 is adjusted to 30% to 38% to obtain a third flotation slurry, and the enrichment of rare earth minerals is completed, and the specific method is as follows: An auxiliary collector is added to the third flotation slurry, then sodium hydroxide is added, the pH of the slurry is adjusted to 9 to 11, stirred for 2 min to 3 min, and the third flotation is performed, and the rare earth minerals float up as froth, and the obtained froth product is a rare earth rough concentrate, and the tank bottom product is a phosphorus concentrate, which is recycled as a phosphorus resource; S4, rare earth rough concentrate cleaning: The rare earth rough concentrate obtained in S303 is subjected to four times of cleaning treatment in sequence to remove the residual gangue minerals and impurities step by step; S401, first cleaning: The solid mass fraction of the rare earth rough concentrate obtained in S303 is adjusted to 25%-35% to obtain a first cleaning slurry, and water glass is added to the first cleaning slurry, and stirring is performed for 3-5 min, and flotation is performed, and the residual siliceous gangue minerals are discharged with the tank bottom to obtain a first cleaning foam product, which is a preliminarily purified rare earth concentrate; S402, second cleaning: Water glass is added to the first cleaning foam product obtained in S401, and stirring is performed for 2-4 min, and flotation is performed, and the residual siliceous gangue minerals are discharged with the tank bottom to obtain a second cleaning foam product; S403, third cleaning: Water glass is added to the second cleaning foam product obtained in S402, and stirring is performed for 1-3 min, and flotation is performed, and the trace residual impurities are discharged with the tank bottom to obtain a third cleaning foam product; S404, fourth cleaning: The third cleaning foam product obtained in S403 is subjected to flotation, and the last trace residual impurity particles are removed through physical sorting to obtain a high-grade rare earth concentrate.

2. The method for enriching rare earth minerals in low-grade apatite according to claim 1, characterized in that, The raw ore rare earth grade of the low-grade apatite ore in S1 is 0.15%-0.50%; the particle size of the coarse crushing product in S1 is <50 mm; the particle size of the medium crushing product is <20 mm; the ball mill rotation speed in the grinding treatment is 18-22 r / min, the solid mass fraction in the ore slurry in the grinding treatment is 65%-75%, the grinding treatment time is 30-60 min, and the mass fraction of the ore slurry with a particle size <0.045 mm after the grinding is 80%-90%.

3. The method of claim 1, wherein the low-grade apatite is a rare earth ore. The feed pressure of the classification desliming treatment in S2 is 0.15-0.25 MPa, the overflow pipe diameter is 50-80 mm, and the underflow port diameter is 20-30 mm. ​ 4. The method for enriching rare earth minerals from low-grade apatite according to claim 1, characterized in that, The fatty acid collector in S301 is oleic acid or oxidized paraffin soap; the mass ratio of the low-grade apatite ore in S1 to the sodium carbonate, water glass, fatty acid collector, pine oil in S301 is 1 t:(500-1000) g:(800-1500) g:(100-300):(30-60) g; the rotation speed of the flotation machine impeller in the first flotation in S301 is 1800-2200 r / min, and the scraping bubble speed is 15-20 times / min.

5. The method of claim 1, wherein the low-grade apatite is a rare earth ore. 5 The C-type regulator in S302 is diethyl citrate or diethyl tartrate; the F-type collector is a compound of hydroxyethyl phosphonic acid and benzhydroxamic acid with a mass ratio of 1:2; the mass ratio of the low-grade apatite ore in S1 and the zinc phosphate complex, the C-type regulator and the F-type collector in S302 is 1t:(350-650)g:(150-300)g:(80-200)g; the impeller rotating speed of the flotation machine in the second flotation in S302 is 1700-2100r / min, and the scraping bubble speed is 14-18 times / min.

6. The method of claim 1, wherein the low-grade apatite is a rare earth ore. 6 The auxiliary collector in S303 is a mixture of oxidized paraffin soap and hydroxamic acid with a mass ratio of 1:(3-5); the mass ratio of the low-grade apatite ore in S1 and the auxiliary collector in S303 is 1t:(100-300)g; the impeller rotating speed of the flotation machine in the third flotation in S303 is 1600-2000r / min, and the scraping bubble speed is 12-18 times / min.

7. The method of claim 1, wherein the low-grade apatite is a rare earth ore. 5 The mass ratio of the low-grade apatite ore in S1 and the water glass in S401 is 1t:(200-400)g; the impeller rotating speed of the flotation machine in the flotation in S401 is 1400-1500r / min, and the scraping bubble speed is 15-20 times / min.

8. The method for enriching rare earth minerals in low-grade apatite according to claim 1, characterized in that, The mass ratio of the low-grade apatite ore in S1 and the water glass in S402 is 1t:(100-200)g; the impeller rotating speed of the flotation machine in the flotation in S402 is 1400-1500r / min, and the scraping bubble speed is 15-20 times / min.

9. The method of claim 1, wherein the low-grade apatite is a rare earth ore. 5 The mass ratio of the low-grade apatite ore in S1 and the water glass in S403 is 1t:(50-100)g; the impeller rotating speed of the flotation machine in the flotation in S403 is 1400-1500r / min, and the scraping bubble speed is 15-20 times / min.

10. The method of claim 1, wherein the low-grade apatite is a rare earth ore. 10 The impeller rotating speed of the flotation machine in the flotation in S404 is 1400-1500r / min, and the scraping bubble speed is 15-20 times / min; the rare earth grade in the high-grade rare earth concentrate is 11.65%-12.55%.