A method for comprehensively recovering apatite, rare earth and gypsum from a low-grade and difficult-to-separate phosphorus-containing iron tailings of gypsum type

Abstract

The application relates to a method for comprehensively recovering apatite, rare earth and gypsum from a gypsum-type low-grade and refractory phosphorus-containing iron tailings, and relates to the technical field of ore dressing. According to the mineral composition and distribution characteristics of the gypsum-type low-grade and refractory phosphorus-containing iron tailings, through development of related flotation reagents and design and optimization of a flotation process, a principle process of 'grinding-magnetic separation for removing iron-flotation for removing sulfur-asynchronous flotation for removing gypsum-positive flotation of apatite' is proposed, qualified phosphorus concentrate (P2O5), rare earth elements and gypsum products can be obtained, the grade of the gypsum is more than 90%, the P2O5 grade of the mixed concentrate of phosphorus and rare earth is 30.83%, the recovery rate is 49.11%, the REO grade of the rare earth is 0.82%, and the recovery rate is 42.88%, the comprehensive utilization of the associated apatite, rare earth and gypsum resources in the gypsum-type low-grade and refractory phosphorus-containing iron tailings is realized, the method has the advantages of good separation effect, high resource utilization rate and the like, and has good social and economic values.

Description

TECHNICAL FIELD

[0001] The application relates to a processing method of phosphorus iron tailings, in particular to a method for comprehensively recovering apatite, rare earth and gypsum from a low-grade and difficult-to-select phosphorus-containing iron tailing of a gypsum type, and belongs to the technical field of phosphorus ore dressing. BACKGROUND

[0002] Phosphorus ore can be used to prepare chemical fertilizer, phosphoric acid, phosphide and other phosphate, and is widely applied to the fields of agriculture, chemical industry, medicine, military industry, food, light industry, battery and the like, and has important strategic value for food security and industrial development.

[0003] In the north of China, there are rich phosphorus-containing iron ore resources, iron minerals in the minerals are mainly magnetite, and phosphorus minerals are mainly apatite, the phosphorus content in the ores is generally low, the dressing ratio is large, and the cost is high, therefore, the magnetite in the phosphorus ore is usually recovered by adopting a magnetic separation process, and the phosphorus tailings enter a tailing pond, thereby causing great waste of phosphorus resources. Therefore, it is of great significance to comprehensively recover and experimentally study the low-grade phosphorus ore resources associated with the iron tailings.

[0004] The conventional process of direct flotation of the phosphorus ore usually adds water glass as an inhibitor and fatty acid as a collector to perform direct flotation, but for the low-grade and difficult-to-select type of phosphorus ore, due to the low phosphorus content in the raw ore and the complex mineral composition, the single direct flotation or reverse flotation has the defects of low selectivity of reagents, unsatisfactory dressing effect and the like, and high-quality phosphorus concentrate cannot be obtained. Meanwhile, part of hematite is inevitably contained in the phosphorus-containing iron tailings, and the hematite with good floatability will also be floated in large quantities when the phosphorus ore is floated, thereby causing the iron content in the phosphorus concentrate to exceed the standard and affecting the quality of the concentrate. SUMMARY

[0005] In view of the defects of the prior art, the application aims to provide a method for comprehensively recovering apatite, rare earth and gypsum from a low-grade and difficult-to-select phosphorus-containing iron tailing of a gypsum type, the method adopts a process of “grinding-magnetic separation for removing iron-flotation for removing sulfur-reverse flotation for removing gypsum-direct flotation for apatite”, and can realize efficient and high-selectivity enrichment and recovery of the apatite in the low-grade and difficult-to-select phosphorus-containing iron tailing of the gypsum type, and the rare earth and gypsum resources are also comprehensively utilized, and the method has the advantages of good separation effect, high resource utilization rate, environmental friendliness and the like.

[0006] In order to realize the above technical purpose, the application provides a method for comprehensively recovering apatite, rare earth and gypsum from a low-grade and difficult-to-select phosphorus-containing iron tailing of a gypsum type, and the method comprises the following steps:

[0007] 1) the low-grade and difficult-to-select phosphorus-containing iron tailing of the gypsum type is subjected to regrinding treatment, and the obtained ore slurry is sequentially subjected to magnetic separation for removing iron and reverse flotation for removing sulfur, to obtain sulfur-removing tailings and sulfur concentrate;

[0008] 2) The desulfurization tailings are subjected to asynchronous flotation desulfurization by using carbonate adjusting agent and fatty acid collector LH to obtain gypsum concentrate and desulfurization tailings;

[0009] 3) The desulfurization tailings are subjected to apatite direct flotation by using carbonate adjusting agent, saltified water glass inhibitor, acidified water glass inhibitor, cellulose inhibitor ZY, and fatty acid collector LH to obtain apatite and rare earth mixed concentrate.

[0010] The present application is directed to the mineral composition and distribution characteristics of the gypsum type low-grade refractory phosphorus-containing iron tailings, and a process flow of "grinding-magnetic separation to remove iron-flotation desulfurization-asynchronous flotation desulfurization-direct flotation of apatite" is adopted to realize the efficient separation and comprehensive recovery of apatite, rare earth and gypsum in the gypsum type low-grade refractory phosphorus-containing iron tailings. The gypsum type low-grade refractory phosphorus-containing iron tailings are first re-ground to realize the liberation of the associated phosphorus iron ore, which is beneficial to the subsequent magnetic separation process to separate the iron ore. The re-ground slurry is subjected to magnetic separation to remove the residual small amount of magnetite and hematite minerals. The slurry after removing the iron ore is subjected to reverse flotation to remove sulfur. The desulfurization tailings are adjusted by using carbonate adjusting agent to adjust the hydrophilic and hydrophobic properties of the two calcium-containing minerals of gypsum and apatite, and the flotation rate of gypsum and apatite is controlled by using fatty acid collector LH to realize the high-selectivity asynchronous flotation separation of gypsum and apatite, and gypsum is preferentially separated. The desulfurization tailings are phosphorus ore enrichment minerals, and the phosphorus ore is mainly recovered by direct flotation. In the flotation process, carbonate adjusting agent is used to adjust the pH, saltified water glass inhibitor is used to selectively inhibit the silicon-containing gangue minerals, acidified water glass inhibitor is used to selectively inhibit calcite gangue minerals, cellulose inhibitor ZY is used to selectively inhibit gypsum and iron dolomite gangue minerals, and fatty acid collector LH is used to float apatite. Finally, apatite and rare earth mixed concentrate are obtained. The method of the present application can separate gypsum with a grade of more than 90%. The P2O5 grade in the apatite and rare earth mixed concentrate reaches 30.83%, and the recovery rate can reach 49.11%. The REO grade of rare earth can reach 0.82%, and the recovery rate can reach 42.88%.

[0011] As a preferred scheme, the main chemical composition of the gypsum type low-grade phosphorus-containing iron tailings is as follows: P2O5 grade is 2.5% to 7.0%, CaO mass content is 15% to 25%, MgO mass content is 1.5% to 5%, SO3 mass content is 15% to 26%, SiO2 mass content is 18% to 34%, Fe2O3 mass content is 25% to 38%, and rare earth elements are mainly present in apatite minerals. The phosphorus grade of the gypsum type low-grade phosphorus-containing iron tailings involved in the present application is low, and the iron content is high. It is difficult to obtain high-grade phosphorus concentrate by conventional beneficiation methods.

[0012] As a preferred scheme, the gypsum type low-grade and refractory phosphorus-containing iron tailings are re-ground to a particle size of-0.074 mm, and the mass percentage of the particle size is 80% to 90%. Grinding the gypsum type low-grade and refractory phosphorus-containing iron tailings to an appropriate particle size is conducive to the complete separation of mineral monomers and the subsequent separation.

[0013] As a preferred scheme, the magnetic separation for removing iron adopts a magnetic drum, and the magnetic field strength used in the magnetic separation is 0.4 to 0.8 T.

[0014] As a preferred scheme, the reverse flotation desulfurization includes a roughing, a cleaning and a scavenging process. The reverse flotation desulfurization process uses copper sulfate activator, organic mercapto collector and No. 2 oil frother. As a more preferred scheme, the reagent system of the roughing is that the amount of the copper sulfate activator is 40 to 80 g / t, the amount of the organic mercapto collector is 50 to 100 g / t, and the amount of the No. 2 oil frother is 10 to 15 g / t. The reagent system of the scavenging is that the amounts of the copper sulfate activator, the organic mercapto collector and the No. 2 oil frother are all half of the reagent amounts of the roughing. The preferred organic mercapto collector is at least one of a xanthate collector, a black drug collector and an ethylthiuram.

[0015] As a preferred scheme, the asynchronous flotation for removing gypsum includes a roughing, a cleaning and a scavenging process. As a more preferred scheme, the reagent system of the roughing is that the amount of the carbonate regulator is 0.5 to 2 kg / t, and the amount of the fatty acid salt collector LH is 50 to 150 g / t. The reagent system of the scavenging is that the amount of the fatty acid salt collector LH is half of the amount of the fatty acid salt collector LH of the roughing. In the asynchronous flotation process, the carbonate regulator includes at least one of sodium carbonate, sodium bicarbonate, calcium carbonate and potassium carbonate, which can transform the surface of the gypsum from hydrophilic to hydrophobic by forming calcium carbonate on the surface of the gypsum to increase the hydrophobicity, thereby expanding the difference in the flotation rate with the apatite and preferentially completing the hydrophobic floating. The fatty acid collector LH is obtained by saponification of 30 to 50 parts by mass of oleic acid, 10 to 20 parts by mass of linoleic acid, 10 to 15 parts by mass of lauric acid, 3 to 8 parts by mass of linolenic acid and 10 to 20 parts by mass of ricinoleic acid with 0.4 to 0.6 parts by mass of sodium hydroxide. More specifically, the fatty acid collector LH is prepared by saponification reaction of the mixed fatty acid and sodium hydroxide in an aqueous solution at 70 to 90°C. The fatty acid salt collector LH of the present application is used by combination of long-chain fatty acids, short-chain fatty acids, saturated fatty acids and unsaturated fatty acids, and is subjected to a certain degree of saponification treatment, which reduces the critical micelle concentration of the combined reagent, improves the stability and rheological properties of the flotation froth, and further increases the selectivity of the collector. In the asynchronous flotation process, except for the second scavenging, the rest of the middlings are sequentially returned to the previous operation.

[0016] As a preferred scheme, the apatite direct flotation includes one roughing, 4-6 times of cleaning and one scavenging process. As a more preferred scheme, the reagent system of the roughing is that the amount of the carbonate regulator is 0.5-1.5 kg / t, the amount of the salted water glass inhibitor is 500-1500 g / t, the amount of the cellulose inhibitor ZY is 50-100 g / t, and the amount of the fatty acid collector LH is 1 kg / t-2 kg / t. In the apatite direct flotation process, the middlings of the other cleaning processes are sequentially returned to the previous process except the middling of the third cleaning.

[0017] As a more preferred scheme, the reagent system of the cleaning is that the salted water glass inhibitor and the cellulose inhibitor ZY are used in the first two cleaning processes, and the acidified water glass inhibitor and the cellulose inhibitor ZY are used in the third cleaning process and the following cleaning processes; the amount of the acidified water glass inhibitor in the first cleaning process is 80-150 g / t, the amount of the cellulose inhibitor ZY is 8-15 g / t, and the amount of the inhibitor in the second cleaning process and the following cleaning processes is 0.5-1 times of the amount of the inhibitor in the previous cleaning process (the amount of the acidified water glass inhibitor in the third cleaning is relative to the amount of the salted water glass in the second cleaning).

[0018] As a more preferred scheme, the salted water glass inhibitor is prepared by reacting at least one of calcium chloride, iron chloride and aluminum sulfate with water glass according to the mass ratio of 1:2-4; and the acidified water glass inhibitor is prepared by reacting water glass with concentrated sulfuric acid or hydrochloric acid according to the mass ratio of 5:1-5:3.

[0019] As a more preferred scheme, the cellulose inhibitor ZY is composed of the following components in mass parts: carboxymethyl cellulose 50-70 parts, starch 15-20 parts and dextrin 10-15 parts. The carboxymethyl cellulose has a stronger inhibiting effect on gypsum, the starch has a stronger inhibiting effect on iron-containing minerals, and the selectivity of the dextrin to the iron-containing minerals is better than that of the carboxymethyl cellulose and the starch. Through the combined use of the three reagents, the inhibiting effect and the selectivity to the complex gangue minerals are strengthened by the synergistic effect, and the grade of the apatite in the concentrate is improved.

[0020] As a more preferred scheme, in the asynchronous flotation process, the middling of the scavenging is separately discharged, and the middlings of the other processes are sequentially returned to the previous process.

[0021] As a more preferred scheme, in the apatite direct flotation process, the middling of the third cleaning is separately discharged, and the middlings of the other processes are sequentially returned to the previous process.

[0022] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0023] 1. This invention achieves the recovery of extremely low-grade apatite from gypsum-type low-grade and difficult-to-select phosphorus-iron tailings by adopting a process flow of "grinding-magnetic separation to remove iron-flotation-desulfurization-reverse flotation to remove gypsum-direct flotation to remove apatite". At the same time, it realizes the resource recovery and utilization of gypsum and rare earth. It has the advantages of good separation effect and high resource utilization rate, and has good social and economic value.

[0024] 2. In the positive flotation process of apatite, this invention, by adopting a suitable reagent system, can effectively inhibit the flotation of hematite, gypsum, silicate minerals and carbonate minerals, thereby greatly improving the grade and recovery rate of phosphate concentrate and reducing the iron content in the phosphate concentrate. Under the preferred beneficiation conditions, the P2O5 grade in the phosphate and rare earth mixed concentrate is 30.83% with a recovery rate of 49.11%, and the rare earth REO grade is 0.82% with a recovery rate of 42.88%.

[0025] 3. Compared with conventional reverse-direct flotation process for phosphate rock, the present invention has high separation efficiency, low cost, environmental friendliness, and good prospects for industrial application. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of the present invention for the comprehensive recovery of apatite, rare earth elements and gypsum from gypsum-type low-grade and difficult-to-process phosphorus-iron tailings.

[0027] Figure 2 The image shows the XRD pattern of the gypsum product obtained in Example 1.

[0028] Figure 3 The image shows the XRD pattern of the apatite concentrate obtained in Example 1. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail and completely below with reference to the accompanying drawings and embodiments. Of course, the following embodiments are for further illustration of the invention and are not intended to limit the scope of protection of the claims of this invention.

[0030] Example 1

[0031] Taking the iron tailings from a beneficiation plant in Anhui Province as the research object, the main minerals and their contents in this phosphorus-containing iron tailings are as follows: P2O5 grade 2.57%, CaO mass content 18.76%, MgO mass content 3.29%, SO3 mass content 19.50%, SiO2 mass content 23.29%, and Fe2O3 mass content 32.42%. The raw ore belongs to the gypsum-containing type of low-grade phosphorus-containing iron tailings.

[0032] The mineral processing method in this case study includes the following steps.

[0033] (1) The raw ore is ground to obtain a grinding product with a particle size of -0.074mm and a particle size of 84.48%. The grinding product is directly fed into the magnetic separation process with a magnetic field strength of 0.7T.

[0034] (2) Desulfurization: The magnetic separation tailings in step 1 enter the reverse flotation desulfurization process. The amount of copper sulfate activator used in the desulfurization roughing process is 50g / t, the amount of butyl xanthate collector is 50g / t, the amount of No. 2 oil is 15g / t, the amount of desulfurization scavenging reagent is halved, and no reagent is added for desulfurization fine selection.

[0035] (3) Degypsum: The desulfurized tailings from step 2 enter the degypsum process. In the degypsum roughing process, the amount of sodium carbonate modifier is 1.5 kg / t, the amount of collector LH is 120 g / t, the amount of collector LH in the degypsum scavenging process is 60 g / t, and no reagent is added in the degypsum fine selection.

[0036] (4) Phosphate rock direct flotation: The gypsum-removed tailings from step 3 enter the phosphate rock direct flotation process, and after a roughing, scavenging, and cleaning process, flotation phosphate concentrate is obtained. The roughing agents are sodium carbonate, salinized water glass (water glass and calcium chloride at a mass ratio of 2:1), cellulose inhibitor ZY (mixed with 55 parts carboxymethyl cellulose, 20 parts starch, and 12 parts dextrin), and fatty acid collector LH (50 parts oleic acid, 15 parts linoleic acid, 12 parts sodium laurate, 5 parts linolenic acid, 15 parts ricinoleic acid, and 0.5 parts sodium hydroxide, prepared by saponification) are used at dosages of 1000 g / t, 1000 g / t, 50 g / t, and 12 g / t, respectively. 00g / t; For Selected 1, the dosage of salt-treated water glass and cellulose inhibitor ZY is 100g / t and 10g / t respectively; for Selected 2, the dosage of salt-treated water glass and ZY is 50g / t and 5g / t respectively; for Selected 3, the dosage of acid-treated water glass (prepared from water glass and concentrated sulfuric acid at a mass ratio of 5:2) and cellulose inhibitor ZY is 30g / t and 3g / t respectively; for Selected 4, the dosage of cellulose inhibitor ZY is 15g / t; and for Selected 5, the dosage of cellulose inhibitor ZY is 10g / t. Among these, Selected 2 middlings are processed separately, while the remaining middlings are sequentially returned to the previous operation.

[0037] Final concentrate product specifications: P2O5 grade 30.83%, Fe2O3 content 1.79%, MgO content 0.86%, P2O5 recovery rate 47.11%.

[0038] Example 2

[0039] The main minerals and their contents in gypsum-type low-grade phosphorus-iron tailings are as follows: P2O5 grade 4.27%, CaO mass content 20.48%, MgO mass content 2.96%, SO3 mass content 17.63%, SiO2 mass content 27.24%, and Fe2O3 mass content 26.58%.

[0040] Compared with Example 1, this example has a higher P2O5 grade and a lower iron content.

[0041] The mineral processing method in this case study includes the following steps.

[0042] (1) The raw ore is ground to obtain a grinding product with a particle size of -0.074mm and a particle size of 88.43%. The grinding product is directly fed into the magnetic separation process with a magnetic field strength of 0.6T.

[0043] (2) Desulfurization: The magnetic separation tailings in step 1 enter the reverse flotation desulfurization process. The amount of copper sulfate activator used in the desulfurization roughing process is 50g / t, the amount of butyl ammonium black collector used is 50g / t, the amount of No. 2 oil used is 15g / t, the amount of desulfurization scavenging reagent is halved, and no reagent is added for desulfurization fine selection.

[0044] (3) Degypsum: The desulfurized tailings from step 2 enter the degypsum process. During the roughing process of degypsum, the amount of sodium carbonate modifier is 1.2 kg / t, the amount of fatty acid collector LH is 80 g / t, the amount of fatty acid collector LH in the degypsum scavenging process is 40 g / t, and no reagent is added in the fine degypsum process.

[0045] (4) Phosphate rock flotation: The gypsum-removed tailings from step 3 enter the phosphate rock flotation process and are processed through a roughing, scavenging and cleaning process to obtain flotation phosphate concentrate. The dosages of the crude sodium carbonate, salinized water glass (prepared by mixing water glass and calcium chloride at a mass ratio of 2:1), cellulose inhibitor ZY (prepared by mixing 55 parts carboxymethyl cellulose, 20 parts starch, and 12 parts dextrin), and fatty acid collector LH (prepared by saponification of 50 parts oleic acid, 15 parts linoleic acid, 10 parts sodium laurate, 5 parts linolenic acid, 15 parts ricinoleic acid, and 0.5 parts sodium hydroxide) are 1000 g / t, 900 g / t, 40 g / t, and 1200 g / t, respectively. For the refined 1, the dosages of salinized water glass and cellulose inhibitor ZY are 110 g / t and 10 g / t, respectively. For the refined 2, the dosages of salinized water glass and ZY are 45 g / t and 5 g / t, respectively. For the refined 3, the dosages of acidified water glass (prepared by mixing water glass and concentrated sulfuric acid at a mass ratio of 5:2) and cellulose inhibitor ZY are 30 g / t and 3 g / t, respectively. For the refined 4, the dosage of ZY is 15 g / t. Three of the selected medium-sized mines were opened separately, while the remaining medium-sized mines were returned sequentially to the previous operation.

[0046] Final concentrate product specifications: final apatite concentrate P2O5 grade 33.48%, Fe2O3 content 1.14%, MgO content 0.89%, P2O5 recovery rate 54.83%, REO grade 0.84%, REO recovery rate 37.45%, gypsum concentrate product purity 92%.

[0047] Comparative Example 1

[0048] The difference between this comparative example and Example 1 is that the fatty acid collector LH used in the degypsum removal and phosphate rock positive flotation in Example 1 is replaced with sodium oleate alone; all other steps are the same as in Example 1.

[0049] Comparative Example 2

[0050] The difference between this comparative example and Example 1 is that the cellulose inhibitor ZY in Example 1 was replaced with carboxymethyl cellulose, while the other experimental procedures and parameters remained the same as in Example 1.

[0051] Comparative Example 3

[0052] The difference between this comparative example and Example 1 is that the salinized water glass inhibitor and acidified water glass inhibitor in Example 1 are replaced with water glass as the inhibitor, while the other experimental procedures and parameters are consistent with those in Example 1.

[0053] Comparative Example 4

[0054] The difference between this comparative example and Example 1 is that no gypsum removal process was performed before the apatite flotation, while the other test procedures and parameters remained the same as in Example 1.

[0055] Comparative Example 5

[0056] The difference between this comparative example and Example 1 is that no desulfurization process was performed before gypsum flotation, while the other test procedures and parameters remained the same as in Example 1.

[0057] Comparative Example 6

[0058] The difference between this comparative example and Example 1 is that the raw ore did not undergo magnetic separation to remove iron, but directly entered the flotation desulfurization process. All other test processes and parameters were consistent with those of Example 1.

[0059] Comparative Example 7

[0060] The difference between this comparative example and Example 1 is that during the positive flotation of apatite, the middlings of the third stage of the cleaning process are not opened separately, but are directly returned to the cleaning process of the first stage. All other test procedures and parameters are consistent with those of Example 1.

[0061] Table 1. Relevant test results for Comparative Examples 1-7

[0062]

[0063] As shown in Table 1, in Comparative Example 1, the traditional collector oleic acid was used instead of the novel fatty acid collector LH from this invention. Compared to Example 1, the recovered phosphate concentrate had lower P2O5 grade and recovery rate, and higher Fe2O3 and MgO content, indicating a poorer selectivity of the collector during flotation. Comparative Example 2 shows that single carboxymethyl cellulose had a weaker inhibitory effect than the mixed inhibitor ZY, resulting in higher Fe2O3 and MgO content in the concentrate product. Comparative Examples 3-7 demonstrate the continuity and synergy of the processes in this invention; the absence of any single process would prevent the achieving the beneficiation effect of gypsum-type low-grade phosphorus-iron tailings as shown in Examples 1 and 2.

[0064] The mineral processing method provided by this invention can recover phosphorus resources from iron tailings with extremely low phosphorus grade, and obtain phosphorus concentrate products with qualified iron content, thereby realizing the comprehensive utilization of phosphorus resources associated with iron ore.

Claims

1. A method for the comprehensive recovery of apatite, rare earth elements, and gypsum from gypsum-type, low-grade, difficult-to-process phosphorus-iron tailings, characterized in that: Includes the following steps: 1) Gypsum-type low-grade, difficult-to-process phosphorus-iron tailings are regrinded, and the resulting slurry is then subjected to magnetic separation for iron removal and reverse flotation for desulfurization to obtain desulfurized tailings and sulfur concentrate. 2) The desulfurized tailings are subjected to asynchronous flotation to remove gypsum using carbonate modifiers and fatty acid collectors LH, resulting in gypsum concentrate and de-gypsum tailings; 3) The degypsum tailings are subjected to positive flotation of apatite using carbonate modifiers, salinized water glass inhibitors, acidified water glass inhibitors, cellulose inhibitors ZY and fatty acid collectors LH to obtain a mixed concentrate of apatite and rare earth elements.

2. The method for comprehensively recovering apatite, rare earth elements, and gypsum from gypsum-type, low-grade, difficult-to-process phosphorus-iron tailings according to claim 1, characterized in that: The main chemical composition of the gypsum-type low-grade phosphorus-iron tailings is as follows: P2O5 grade is 2.5%–7.0%, CaO mass content is 15%–25%, MgO mass content is 1.5%–5%, SO3 mass content is 15%–26%, SiO2 mass content is 18%–34%, Fe2O3 mass content is 25%–38%, and rare earth elements are mainly found in apatite minerals.

3. A method for comprehensively recovering apatite, rare earth elements, and gypsum from gypsum-type, low-grade, difficult-to-process phosphorus-iron tailings according to claim 1 or 2, characterized in that: The gypsum-type low-grade, difficult-to-process phosphorus-iron tailings are regrinded until the particle size meets the requirement of -0.074mm particle size with a mass ratio of 80% to 90%.

4. A method for comprehensively recovering apatite, rare earth elements, and gypsum from gypsum-type, low-grade, difficult-to-process phosphorus-iron tailings according to claim 1 or 2, characterized in that: The magnetic separation for iron removal uses a magnetic drum, and the magnetic field strength used in the magnetic separation is 0.4 to 0.8 T.

5. A method for comprehensively recovering apatite, rare earth elements, and gypsum from gypsum-type, low-grade, difficult-to-process phosphorus-iron tailings according to claim 1 or 2, characterized in that: The reverse flotation desulfurization process includes one roughing, one cleaning and one scavenging process; The reverse flotation desulfurization process uses copper sulfate activator, organic mercapto collector, and No. 2 oil foaming agent.

6. A method for comprehensively recovering apatite, rare earth elements, and gypsum from gypsum-type, low-grade, difficult-to-process phosphorus-iron tailings according to claim 5, characterized in that: The reagent system for the roughing process is as follows: the dosage of copper sulfate activator is 40-80 g / t, the dosage of organic mercapto collector is 50-100 g / t, and the dosage of No. 2 oil foaming agent is 10-15 g / t. The reagent system for the scavenging process is as follows: the amounts of copper sulfate activator, organic mercapto collector, and No. 2 oil foaming agent are all halved compared to the amounts of reagents used in the roughing process.

7. A method for comprehensively recovering apatite, rare earth elements, and gypsum from gypsum-type, low-grade, difficult-to-process phosphorus-iron tailings according to claim 1 or 2, characterized in that: The asynchronous flotation degypsum removal process includes one roughing process, two cleaning processes, and two scavenging processes; except for the middlings in the second scavenging process, the remaining middlings are sequentially returned to the previous process.

8. A method for comprehensively recovering apatite, rare earth elements, and gypsum from gypsum-type, low-grade, difficult-to-process phosphorus-iron tailings according to claim 7, characterized in that: The reagent system for the roughing process is as follows: the dosage of carbonate modifier is 0.5-2 kg / t, and the dosage of fatty acid collector LH is 50-150 g / t. The fatty acid collector LH is obtained by saponification of 30-50 parts by weight of oleic acid, 10-20 parts by weight of linoleic acid, 10-15 parts by weight of lauric acid, 3-8 parts by weight of linolenic acid and 10-20 parts by weight of ricinoleic acid with 0.4-0.6 parts by weight of sodium hydroxide. The reagent system for the scavenging process is as follows: the amount of LH, a fatty acid collector used in the roughing process, is halved.

9. A method for comprehensively recovering apatite, rare earth elements, and gypsum from gypsum-type, low-grade, difficult-to-process phosphorus-iron tailings according to claim 1 or 2, characterized in that: The apatite positive flotation process includes one roughing process, four to six cleaning processes, and one scavenging process; except for the third cleaning process which opens up the middlings, the remaining middlings are sequentially returned to the previous process.

10. A method for comprehensively recovering apatite, rare earth elements, and gypsum from gypsum-type, low-grade, difficult-to-process phosphorus-iron tailings according to claim 9, characterized in that: The reagent system for the roughing process is as follows: the dosage of carbonate modifier is 0.5-1.5 kg / t, the dosage of salinized water glass inhibitor is 500-1500 g / t, the dosage of cellulose inhibitor ZY is 50-100 g / t, and the dosage of fatty acid collector LH is 1 kg / t-2 kg / t. The selected reagent system is as follows: the first two selection processes use saline water glass inhibitors and cellulose inhibitors, and the third and subsequent selection processes use acidified water glass inhibitors and cellulose inhibitors; in the first selection process, the dosage of acidified water glass inhibitor is 80-150 g / t, and the dosage of cellulose inhibitor ZY is 8-15 g / t; in the second and subsequent selection processes, the dosage of inhibitors is 0.5-1 times that of the previous selection process. The salinized water glass inhibitor is prepared by reacting at least one of calcium chloride, ferric chloride, and aluminum sulfate with water glass at a mass ratio of 1:2 to 4. The acidified water glass inhibitor is prepared by reacting water glass with concentrated sulfuric acid or hydrochloric acid at a mass ratio of 5:1 to 5:

3. The cellulose inhibitor ZY is composed of the following components in parts by weight: 50-70 parts carboxymethyl cellulose, 15-20 parts starch, and 10-15 parts dextrin.

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