Method for resource utilization of high calcium-magnesium phosphorus tailings

Abstract

The application discloses a method for resource utilization of high calcium-magnesium phosphorus tailings, which comprises the following steps: adding a leaching agent and water into the phosphorus tailings to obtain a calcium-magnesium leaching solution and high-quality phosphorus ore; adding a pH regulator and a surfactant into the calcium-magnesium leaching solution to obtain a calcium leaching solution and magnesium hydroxide slag containing impurities through reaction and filtration; adding an alkaline substance into the calcium leaching solution and introducing CO2 to prepare light calcium carbonate and a salt solution; preparing a magnesium bicarbonate solution by introducing CO2 into the magnesium hydroxide slag after slurry preparation; and finally obtaining light magnesium carbonate through pyrolysis, filtration, washing and drying. The method realizes efficient separation of calcium and magnesium in high calcium-magnesium solid waste, and high-purity light calcium carbonate, light magnesium carbonate and high-quality phosphorus ore are prepared. In addition, the method realizes cyclic utilization of CO2 generated in the process, thereby reducing the emission of greenhouse gases. The method realizes high-value utilization of the phosphorus tailings, and has high product purity and simple process.

Description

Technical Field

[0001] This invention belongs to the field of tailings resource utilization technology, specifically relating to a method for the resource utilization of high-calcium-magnesium-phosphorus tailings. Background Technology

[0002] Phosphate tailings are high-calcium and magnesium solid waste generated during phosphate ore beneficiation. Their main chemical components are CaO, MgO, SiO2, and P2O5. my country's comprehensive utilization rate of phosphate tailings is low, with large quantities piled up in tailings ponds. This not only occupies significant land resources but also impacts the surrounding ecological environment. Phosphate tailings are rich in elements such as calcium and magnesium. Extracting and converting these elements can not only reduce tailings production but also transform them into high-value-added products, bringing economic benefits while addressing environmental pollution, improving the ecological environment, and remediating land use.

[0003] Currently, the main ways to comprehensively utilize phosphorus tailings include reprocessing into phosphorus concentrate, mine backfilling, preparation of building materials, production of phosphorus-containing fertilizers, and preparation of microcrystalline glass. However, due to the low phosphorus content of phosphorus tailings, the development of reagents used in flotation is difficult. While developing phosphorus tailings into building materials and fertilizers can dispose of large quantities of phosphorus tailings, the product value is low. Converting the calcium and magnesium in phosphorus tailings into light calcium carbonate and light magnesium carbonate is an efficient method for utilizing the calcium and magnesium elements in phosphorus tailings and a way to achieve high-value utilization of phosphorus tailings.

[0004] The key to preparing light calcium carbonate and light magnesium carbonate from phosphate tailings is the separation of calcium and magnesium. Currently, methods for calcium and magnesium separation from phosphate tailings include carbonation, acid hydrolysis, and ammonium leaching. Carbonation involves calcining and digesting the phosphate tailings before further carbonation. Calcium is converted into calcium carbonate and remains in the filter residue, while magnesium exists as magnesium bicarbonate in the filtrate. For example, patent CN102923739A uses this method to separate calcium and magnesium. However, the resulting calcium carbonate product contains unreacted magnesium and insoluble impurities, resulting in low product purity, and calcination consumes a large amount of energy. Acid hydrolysis involves adding hydrochloric acid, sulfuric acid, or organic acids to dissolve magnesium and calcium in the phosphate tailings, and then separating calcium and magnesium by adding a precipitant or carbonation. For example, patent CN111484063A uses hydrochloric acid to dissolve the phosphate tailings, obtaining a filtrate containing calcium and magnesium. A decalcifying agent is then used to precipitate calcium to obtain calcium sulfate whiskers. Because elements such as iron and aluminum in the phosphate tailings are released during acid hydrolysis, the prepared calcium and magnesium products contain these metallic elements. Ammonium leaching is a method that uses ammonium salts to leach calcined phosphate tailings and separates calcium and magnesium through multiple leaching processes. For example, in patent CN104860278A, ammonium nitrate is used to leach calcium and ammonium sulfate is used to leach magnesium in the filter residue. This method has a low leaching rate and high energy consumption.

[0005] In summary, the preparation of light calcium carbonate and light magnesium carbonate from phosphogypsum suffers from technical defects such as insufficient product purity, high energy consumption, and complex processes. In particular, the low product purity is a key factor restricting the industrialization of high-value utilization technology for phosphate tailings. It is necessary to continue to develop an efficient method for separating calcium and magnesium from phosphate tailings to obtain high-purity calcium and magnesium products, while also simplifying the process and reducing energy consumption. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for the resource utilization of high-calcium-magnesium phosphorus tailings. The method utilizes a compound organic acid to react with calcium and magnesium in the phosphorus tailings to generate soluble chelated calcium and magnesium. Then, by adjusting the pH and adding a surfactant, the calcium and magnesium are efficiently separated. Finally, light calcium carbonate and light magnesium carbonate are prepared separately, which has the advantages of high purity of calcium and magnesium products and low energy consumption.

[0007] To achieve the above objectives, the present invention provides a method for the resource utilization of high-calcium-magnesium-phosphorus tailings, comprising the following steps:

[0008] (1) Grind the phosphate tailings through a 100-mesh sieve to obtain phosphate tailings powder;

[0009] (2) Mix phosphorus tailings powder, leaching agent and water in proportion, stir and react thoroughly, and then filter to obtain calcium magnesium leaching solution and phosphate rock;

[0010] (3) Add pH adjuster and surfactant to the calcium magnesium leaching solution obtained in step (2), stir and react, then let stand, cool and filter to obtain calcium leaching solution and magnesium hydroxide slag containing impurities.

[0011] (4) Add an alkaline substance to the calcium leaching solution obtained in step (3) and introduce CO2 while stirring and reacting. Stop the gas flow when the pH value of the solution is 8, continue stirring for 0.5-1h, and filter to obtain light calcium carbonate and salt solution.

[0012] (5) Add water to the magnesium hydroxide slag containing impurities obtained in step (3) to make a 10wt%-20wt% magnesium hydroxide slag slurry, introduce CO2, and react while stirring. Stop the gas flow when the pH value of the solution is 7, and filter to obtain magnesium bicarbonate solution.

[0013] (6) The magnesium bicarbonate solution obtained in step (5) is pyrolyzed, filtered and dried to obtain light magnesium carbonate;

[0014] (7) Concentrate and crystallize the ammonium salt solution obtained in step (4) to recover the ammonium salt crystals.

[0015] Preferably, the mass ratio of phosphorus tailings powder, leaching agent and water in step (2) is 1:2-3:6-12; the reaction temperature is 80-90℃ and the reaction time is 3-5h.

[0016] Preferably, the extractant is a compound of gluconic acid, lactic acid, acetic acid and iminosuccinic acid.

[0017] More preferably, the extractant contains 30%-70% gluconic acid, 10%-25% lactic acid, 10%-25% acetic acid and 10%-20% iminosuccinic acid.

[0018] Preferably, the pH adjuster in step (3) is calcium oxide, and the pH value of the calcium magnesium leaching solution is 11 after the addition of calcium oxide; the surfactant is tetrabutyl titanate; the reaction temperature is 80-90℃, and the reaction time is 0.5-1h.

[0019] More preferably, the amount of surfactant used is 1-3.5‰ of the mass of the phosphorus tailings powder.

[0020] Preferably, the alkaline substance in step (4) is ammonia, potassium hydroxide or sodium hydroxide, with a concentration of 20-30%, and the mass ratio of alkaline substance to leaching agent is 2.05-3.15:1.

[0021] Preferably, the flow rate of CO2 introduced in steps (4) and (5) is 300-500 mL / min.

[0022] Preferably, the pyrolysis temperature in step (6) is 70-80℃, and the drying temperature is 200-240℃.

[0023] Preferably, the CO2 generated in step (2) is collected and mixed with the CO2 generated in step (6) pyrolysis to obtain CO2 with a mass fraction of 20%-35%, and then the collected CO2 is passed into steps (4) and (5) for reaction.

[0024] The beneficial effects of this invention are as follows:

[0025] 1. A leaching agent is prepared by compounding gluconic acid, acetic acid, lactic acid, and iminosuccinic acid. This agent is then used to leach and dissolve phosphate tailings. Compared with using strong acids such as hydrochloric acid, sulfuric acid, and nitric acid to dissolve phosphate tailings, this method can accurately dissolve calcium and magnesium in the phosphate tailings without introducing dissolved phosphorus, silicon, iron, aluminum, or other elements into the solution. This reduces the content of impurities and thus improves the purity of the prepared light calcium carbonate and light magnesium carbonate. The purity of both light calcium carbonate and light magnesium carbonate can reach up to 99.1%.

[0026] 2. After leaching with a leaching agent, calcium oxide is added to adjust the pH value of the phosphorus tailings, allowing magnesium ions to precipitate as magnesium hydroxide, while calcium exists in the solution as soluble chelated calcium. This separates calcium and magnesium without introducing new impurities. At the same time, a surfactant is added after pH adjustment to promote the separation of calcium ions from the surface of the magnesium hydroxide precipitate, achieving efficient separation of calcium and magnesium and solving the problem of low product purity caused by incomplete separation of calcium and magnesium.

[0027] 3. After calcium and magnesium separation, ammonia is added to the obtained calcium leaching solution and CO2 is introduced to directly generate calcium carbonate from soluble chelated calcium. This eliminates the need for the conventional method of first converting calcium hydroxide precipitate into soluble calcium such as calcium chloride and then introducing CO2 to generate calcium carbonate precipitate. This simplifies the preparation process and accelerates the production efficiency of calcium carbonate.

[0028] 4. The CO2 generated during the leaching process and the CO2 generated during the pyrolysis process are collected, mixed, and their concentrations are adjusted. Then, they are fed into the preparation process of light calcium carbonate and magnesium bicarbonate, realizing the recycling of CO2, reducing greenhouse gas emissions, and conforming to the concept of green and environmentally friendly production.

[0029] 5. This invention uses high-calcium and magnesium solid waste—phosphate tailings—as the main raw material. Through reactions such as leaching, filtration, carbonation, and pyrolysis, high-purity light calcium carbonate and light magnesium carbonate are prepared, and the content of phosphate rock is increased from about 8% to 25%-26%, resulting in high-quality phosphate rock. This invention achieves the reduction and high-value utilization of phosphate tailings, while also realizing the enrichment and recovery of phosphorus, avoiding resource waste and environmental impact. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0031] The technical solution of the present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention should be determined by the contents of the claims. Modifications and substitutions made by those skilled in the art to the technical solution of the present invention without creative effort all fall within the scope of protection of the present invention.

[0032] In the following examples, the phosphorus tailings came from a phosphorus chemical enterprise. Their chemical composition, after elemental analysis by XRF, is shown in the table below:

[0033]

[0034] Example 1

[0035] (1) Take 100 parts of phosphorus tailings, grind them and pass them through a 100-mesh sieve to obtain phosphorus tailings powder;

[0036] (2) Gluconic acid, lactic acid, acetic acid and iminosuccinic acid were mixed in a mass percentage of 30:25:25:20 to prepare an extractant;

[0037] (3) Mix the phosphorus tailings, leaching agent and water in a mass ratio of 1:3:10, stir thoroughly to allow the leaching agent to react with the calcium and magnesium in the phosphorus tailings, separate the calcium and magnesium and phosphorus and release CO2, filter the solution after the reaction to obtain calcium and magnesium leaching solution containing organic acid calcium and organic acid magnesium and phosphorus ore, and collect the generated CO2 at the same time.

[0038] (4) Add calcium oxide to the calcium magnesium leaching solution until the pH of the leaching solution is 11, and add tetrabutyl titanate at 2.5‰ of the mass of phosphorus tailings powder. Stir the reaction thoroughly at 80°C for 3 hours, let it stand and cool to room temperature, and then filter to obtain calcium leaching solution and magnesium hydroxide slag containing impurities.

[0039] (5) Add ammonia (25wt%) to the calcium leaching solution obtained in step (4). The mass of ammonia is 2.86 times the mass of the leaching agent. Heat the solution to 40°C and introduce CO2. Stop the gas flow when the pH of the solution drops to 8. Keep the solution warm and continue stirring for 30 minutes. Filter the solution to obtain a light calcium carbonate and ammonium salt solution. The flow rate of CO2 is 300 mL / min.

[0040] (6) Add water to the magnesium hydroxide slag containing impurities obtained in step (4) to make a slurry, and prepare a magnesium hydroxide slag slurry with a slurry concentration of 10wt%. Heat the slurry to keep its temperature at 40℃ and introduce CO2. Stop the gas flow when the pH of the solution drops to 7. Filter to obtain magnesium bicarbonate solution; wherein the flow rate of CO2 is 300mL / min.

[0041] (7) The magnesium bicarbonate solution was heated to 70°C for pyrolysis, filtered to obtain magnesium carbonate precipitate, and the magnesium carbonate precipitate was dried at 200°C to obtain light magnesium carbonate; CO2 generated during the pyrolysis process was collected.

[0042] The CO2 generated in steps (3) and (7) is collected, mixed, and adjusted to a concentration of 20 wt% CO2 gas, and then passed into steps (5) and (6) for recycling.

[0043] The prepared light calcium carbonate is spherical with an average particle size of 2 μm and a sedimentation volume of 4.5 mL / g. The light magnesium carbonate is rod-shaped with a short diameter of 2-5 μm and a long diameter of 5-50 μm.

[0044] Example 2

[0045] The method and steps are the same as in Example 1, with appropriate adjustments to the proportions, concentrations, and experimental conditions of various raw materials, as follows:

[0046] The extractant in step (2) consists of 35% gluconic acid, 25% lactic acid, 25% acetic acid and 15% iminosuccinic acid;

[0047] In step (3), the mass ratio of phosphorus tailings powder, leaching agent and water is changed from 1:3:10 to 1:3:12;

[0048] In step (4), the stirring temperature is changed from 80℃ to 85℃, and the stirring time is extended from 3h to 4h;

[0049] In step (5), the mass of ammonia water (25wt%) was changed from 2.86 times to 3.01 times the mass of the leaching agent, the reaction temperature was changed from 40℃ to 45℃, and the flow rate of CO2 was changed from 300mL / min to 400mL / min.

[0050] In step (6), the concentration of magnesium hydroxide slag slurry was changed from 10wt% to 15%, the reaction temperature was reduced to 30℃, and the CO2 flow rate was changed from 300mL / min to 400mL / min.

[0051] In step (7), the pyrolysis temperature is increased from 70℃ to 75℃;

[0052] The concentration of CO2 gas introduced was increased from 20 wt% to 25 wt%.

[0053] The prepared light calcium carbonate is spherical with an average particle size of 3.5 μm and a sedimentation volume of 4.8 mL / g. The light magnesium carbonate is rod-shaped with a short diameter of 2-5 μm and a long diameter of 2-40 μm.

[0054] Example 3

[0055] The method and steps are the same as in Example 1, with appropriate adjustments to the proportions, concentrations, and experimental conditions of various raw materials, as follows:

[0056] The extractant in step (2) consists of 40% gluconic acid, 25% lactic acid, 20% acetic acid and 15% iminosuccinic acid;

[0057] In step (4), the stirring temperature is changed from 80℃ to 90℃, and the stirring time is extended from 3h to 5h;

[0058] In step (5), the mass of ammonia water (25wt%) was changed from 2.86 times to 2.82 times the mass of the leaching agent, the reaction temperature was increased from 40℃ to 50℃, and the flow rate of CO2 was 400mL / min.

[0059] In step (6), the concentration of magnesium hydroxide slag slurry is changed from 10wt% to 20%, the reaction temperature is reduced to 30℃, and the CO2 flow rate is 400mL / min;

[0060] In step (7), the pyrolysis temperature is increased from 70℃ to 80℃, and the drying temperature is increased from 200℃ to 220℃;

[0061] The concentration of CO2 gas was increased from 20 wt% to 30 wt%.

[0062] The prepared light calcium carbonate is spherical with an average particle size of 3 μm and a sedimentation volume of 3.8 mL / g. The light magnesium carbonate is rod-shaped with a short diameter of 2-4 μm and a long diameter of 2-20 μm.

[0063] Example 4

[0064] The method and steps are the same as in Example 1, with appropriate adjustments to the proportions, concentrations, and experimental conditions of various raw materials, as follows:

[0065] The extractant in step (2) consists of 50% gluconic acid, 15% lactic acid, 15% acetic acid and 20% iminosuccinic acid;

[0066] In step (3), the mass ratio of phosphorus tailings powder, leaching agent and water is changed from 1:3:10 to 1:2:8;

[0067] In step (4), the stirring temperature is changed from 80℃ to 90℃, and the stirring time is extended from 3h to 5h;

[0068] In step (7), the drying temperature is increased from 200℃ to 220℃;

[0069] The CO2 flow rate was 400 mL / min, and the CO2 concentration was 35 wt%.

[0070] The prepared light calcium carbonate is spherical with an average particle size of 3 μm and a sedimentation volume of 4.3 mL / g. The light magnesium carbonate is rod-shaped with a short diameter of 2-5 μm and a long diameter of 2-40 μm.

[0071] Example 5

[0072] The method and steps are the same as in Example 1, with appropriate adjustments to the proportions, concentrations, and experimental conditions of various raw materials, as follows:

[0073] The extractant in step (2) consists of 60% gluconic acid, 10% lactic acid, 10% acetic acid and 20% iminosuccinic acid;

[0074] In step (4), the stirring temperature is changed from 80℃ to 90℃, and the stirring time is extended from 3h to 5h;

[0075] The temperature of the solution is 45℃ when CO2 is introduced in step (5);

[0076] In step (6), the concentration of magnesium hydroxide slag slurry is 20%, and the reaction temperature is 25℃;

[0077] In step (7), the pyrolysis temperature is changed to 78℃ and the drying temperature is changed to 240℃;

[0078] The concentration of CO2 introduced was 28 wt%.

[0079] The prepared light calcium carbonate is spherical with an average particle size of 3 μm and a sedimentation volume of 4.6 mL / g. The light magnesium carbonate is rod-shaped with a short diameter of 2-4 μm and a long diameter of 3-45 μm.

[0080] Example 6

[0081] The method and steps are the same as in Example 1, with appropriate adjustments to the proportions, concentrations, and experimental conditions of various raw materials, as follows:

[0082] The extractant in step (2) consists of 70% gluconic acid, 10% lactic acid, 10% acetic acid and 10% iminosuccinic acid;

[0083] In step (3), the mass ratio of phosphorus tailings powder, leaching agent and water is changed from 1:3:10 to 1:2.5:12;

[0084] In step (4), the stirring time is extended from 3 hours to 4 hours, while the temperature remains unchanged;

[0085] In step (5), the mass of ammonia water (25wt%) was changed from 2.86 times the mass of the leaching agent to 2.18 times, and the solution temperature was changed from 40℃ to 45℃.

[0086] In step (6), the concentration of magnesium hydroxide slag slurry is changed from 10wt% to 15wt%, and the reaction temperature is changed from 40℃ to 30℃.

[0087] The pyrolysis temperature in step (7) is changed from 70℃ to 80℃, and the drying temperature is changed from 200℃ to 220℃;

[0088] The CO2 flow rate was 400 mL / min, and the CO2 concentration was 23 wt%.

[0089] The prepared light calcium carbonate is spherical with an average particle size of 4.5 μm and a sedimentation volume of 3.6 mL / g. The light magnesium carbonate is rod-shaped with a short diameter of 3-5 μm and a long diameter of 5-50 μm.

[0090] Comparative Example 1

[0091] Calcium carbonate and magnesium hydroxide were prepared from phosphorus tailings according to the method described in Example 1 of CN112694115A. The specific method is as follows:

[0092] (1) Add phosphorus tailings and hydrochloric acid to the decomposition tank, react for 30 min and then separate the solid and liquid to obtain a filtrate containing calcium chloride and magnesium chloride.

[0093] (2) Add ammonium bicarbonate to the list page obtained in step (1) to react and crystallize. Control the pH value to 4.8 and the reaction temperature to 9-42℃. After reacting for 30 minutes, separate the solid and liquid to obtain calcium carbonate containing impurities and filtrate. Wash the calcium carbonate containing impurities with water to obtain calcium carbonate (I).

[0094] (3) Add ammonium bicarbonate to the filtrate obtained in step (3) to react and crystallize, control the pH value to 5.8, and after reacting for 35 min, separate the solid and liquid to obtain high-quality calcium carbonate and filtrate. The filtrate mainly contains magnesium chloride. Wash the high-quality calcium carbonate with water to obtain calcium carbonate (II).

[0095] (4) Ammonia gas is introduced into the filtrate containing magnesium chloride to control the pH value to 8, and magnesium hydroxide precipitate and ammonium chloride solution are obtained. After solid-liquid separation, magnesium hydroxide solid is obtained. Finally, high-quality magnesium hydroxide is obtained by washing.

[0096] (5) The ammonium chloride solution obtained in step (4) is concentrated and crystallized to obtain ammonium chloride crystals.

[0097] The prepared calcium carbonate was spherical with an average particle size of 15 μm and a sedimentation volume of 2.6 mL / g.

[0098] Comparative Example 2

[0099] The methods and steps are the same as in Example 1, except that the leaching agent is changed to iminosuccinic acid. Light calcium carbonate and light magnesium carbonate are prepared respectively. The light calcium carbonate is spherical with an average particle size of 6 μm and a sedimentation volume of 2.8 mL / g. The light magnesium carbonate is rod-shaped with a short diameter of 2-5 μm and a long diameter of 3-45 μm.

[0100] Comparative Example 3

[0101] The methods and steps are the same as in Example 1, except that the leaching agents are changed to 50% gluconic acid and 50% iminosuccinic acid, respectively, to prepare light calcium carbonate and light magnesium carbonate. The light calcium carbonate is spherical with an average particle size of 4 μm and a sedimentation volume of 3.1 mL / g; the light magnesium carbonate is rod-shaped with a short diameter of 3-5 μm and a long diameter of 5-40 μm.

[0102] Comparative Example 4

[0103] The methods and steps are the same as in Example 1, except that the leaching agents are changed to 40% gluconic acid, 30% lactic acid and 30% acetic acid to prepare light calcium carbonate and light magnesium carbonate respectively. The light calcium carbonate is spherical with an average particle size of 4 μm and a sedimentation volume of 2.9 mL / g; the light magnesium carbonate is rod-shaped with a short diameter of 2-5 μm and a long diameter of 3-50 μm.

[0104] Comparative Example 5

[0105] The methods and steps are the same as in Example 1, except that tetrabutyl titanate is not added in step (4). Light calcium carbonate and light magnesium carbonate are prepared respectively. The light calcium carbonate is spherical with an average particle size of 10 μm and a sedimentation volume of 2.3 mL / g. The light magnesium carbonate is rod-shaped with a short diameter of 2-5 μm and a long diameter of 4-50 μm.

[0106] Comparative Example 6

[0107] The method and steps are the same as in Example 1, except that the amount of tetrabutyl titanate in step (4) is changed to 3.5‰. Light calcium carbonate and light magnesium carbonate are prepared respectively. The light calcium carbonate is spherical with an average particle size of 3μm and a sedimentation volume of 4.8mL / g. The light magnesium carbonate is rod-shaped with a short diameter of 2-4μm and a long diameter of 5-40μm.

[0108] Comparative Example 7

[0109] The method and steps are the same as in Example 1, except that the tetrabutyl titanate in step (4) is replaced with sodium stearate to prepare light calcium carbonate and light magnesium carbonate respectively. The light calcium carbonate is spherical with an average particle size of 3.5 μm and a sedimentation volume of 3.8 mL / g; the light magnesium carbonate is rod-shaped with a short diameter of 3-5 μm and a long diameter of 5-40 μm.

[0110] Comparative Example 8

[0111] The method and steps are the same as in Example 1, except that in step (5), ammonia and CO2 are replaced with an equal amount of ammonium carbonate to prepare light calcium carbonate and light magnesium carbonate respectively. The light calcium carbonate is spherical with an average particle size of 20 μm and a sedimentation volume of 1.2 mL / g; the light magnesium carbonate is rod-shaped with a short diameter of 2-5 μm and a long diameter of 4-40 μm.

[0112] The purity of the phosphate rock, calcium carbonate, and magnesium carbonate prepared in the above examples and comparative examples was tested, and the results are shown in Table 1:

[0113] Table 1 Purity of Phosphate Rock, Calcium Carbonate, and Magnesium Carbonate

[0114]

[0115]

[0116] As shown in the table above, the magnesium product prepared in Comparative Example 1 is magnesium hydroxide with a purity of only 97%. The calcium carbonate products are divided into two categories: calcium carbonate (I) with a purity of only 50% and calcium carbonate (II) with a purity of only 96.2%. In contrast, the magnesium product prepared in Examples 1-6 is light magnesium carbonate with a content of over 98%, and the content of light calcium carbonate is also over 98%, making them high-purity products with high economic value. At the same time, Examples 1-6 also increased the P2O5 content from 8.12% to over 25%, preparing high-quality phosphate rock and achieving the enrichment and purification of phosphorus elements contained in phosphate tailings, reducing the difficulty of subsequent utilization. The P2O5 content in Comparative Examples 2-4 is lower than that in Examples 1-6, and the mixture of the four leaching agents is more conducive to improving the P2O5 grade in high-quality phosphate rock.

Claims

1. A method for the resource utilization of high-calcium-magnesium-phosphorus tailings, characterized in that: Includes the following steps: (1) Grind the phosphate tailings through a 100-mesh sieve to obtain phosphate tailings powder; (2) Mix the phosphate tailings powder, leaching agent and water in proportion, stir and react thoroughly, and then filter to obtain calcium magnesium leaching solution and phosphate rock; (3) Add pH adjuster and surfactant to the calcium magnesium leaching solution obtained in step (2), stir and react, then let stand, cool and filter to obtain calcium leaching solution and magnesium hydroxide slag containing impurities. (4) Add ammonia to the calcium leaching solution obtained in step (3) and pass CO2 through it. Stir and react while stirring. Stop the gas flow when the pH of the solution is 8. Continue stirring for 0.5-1h and filter to obtain a light calcium carbonate and ammonium salt solution. (5) Add water to the magnesium hydroxide slag containing impurities obtained in step (3) to make a magnesium hydroxide slag slurry of 10wt%-20wt%, introduce CO2, and react while stirring. Stop the gas flow when the pH value of the solution is 7, and filter to obtain magnesium bicarbonate solution. (6) The magnesium bicarbonate solution obtained in step (5) is pyrolyzed, filtered and dried to obtain light magnesium carbonate; (7) Concentrate and crystallize the ammonium salt solution obtained in step (4) to recover the ammonium salt crystals; The extractant is prepared by combining 30%-70% gluconic acid, 10%-25% lactic acid, 10%-25% acetic acid and 10%-20% iminosuccinic acid by mass percentage.

2. The method for resource utilization of high-calcium-magnesium-phosphate tailings according to claim 1, characterized in that: The mass ratio of phosphorus tailings powder, leaching agent and water in step (2) is 1:2-3:6-12; the reaction temperature is 80-90℃ and the reaction time is 3-5h.

3. The method for resource utilization of high-calcium-magnesium-phosphate tailings according to claim 1, characterized in that: The pH adjuster in step (3) is calcium oxide, and the pH value of the calcium magnesium leaching solution is 11 after the addition of calcium oxide; the surfactant is tetrabutyl titanate; the reaction temperature is 80-90℃, and the reaction time is 0.5-1h.

4. The method for resource utilization of high-calcium-magnesium-phosphate tailings according to claim 3, characterized in that: The amount of surfactant used is 2.6‰ of the mass of the phosphorus tailings powder.

5. The method for resource utilization of high-calcium-magnesium-phosphorus tailings according to claim 1, characterized in that: The mass ratio of ammonia water to leaching agent in step (4) is 2.05-3.15:1; the pH value of the solution when the aeration is stopped is 8.

6. The method for resource utilization of high-calcium-magnesium-phosphate tailings according to claim 1, characterized in that: In steps (4) and (5), the flow rate of CO2 introduced is 300-500 mL / min.

7. The method for resource utilization of high-calcium-magnesium-phosphate tailings according to claim 1, characterized in that: The pyrolysis temperature in step (6) is 70-80℃, and the drying temperature is 200-240℃.

8. The method for resource utilization of high-calcium-magnesium-phosphorus tailings according to claim 1, characterized in that: The CO2 produced in step (2) is collected and mixed with the CO2 produced in step (6) pyrolysis to obtain CO2 with a mass fraction of 20%-35%. The collected CO2 is then passed into steps (4) and (5) for further reaction.

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