Preparation method of nano magnesium oxide
By calcining and hydrothermal treatment of phosphate tailings, the problems of uneven dispersion and low purity in the preparation of nano-magnesium oxide were solved, realizing the preparation of high-purity nano-magnesium oxide and the resource utilization of phosphate tailings.
Patent Information
- Application Number
- CN202511092601.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-05
- Publication Date
- 2025-11-11
AI Technical Summary
Existing nano-magnesium oxide preparation technologies suffer from problems such as uneven product dispersion, easy agglomeration, and low purity, and fail to effectively utilize phosphorus tailings resources.
By calcining and activating phosphorus tailings, magnesium is enriched using ammonium salt solution, magnesium hydroxide precipitate is prepared by hydrothermal method, and finally nano-magnesium oxide is prepared by calcination, thus achieving the enrichment and uniform dispersion of magnesium.
This method produces uniformly dispersed and highly pure nano-magnesium oxide, providing an effective way to utilize phosphorus tailings resources while reducing raw material costs and process complexity.
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Figure CN120922898A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nano-magnesium oxide preparation technology, and in particular to a method for preparing nano-magnesium oxide. Background Technology
[0002] Phosphate rock, as a non-metallic mineral, is abundant globally, but demand is increasing daily. Furthermore, with this rising demand, the P2O5 content in commercial phosphate rock is gradually decreasing. To increase the supply of phosphate rock, medium- and low-grade phosphate rock is enriched, with flotation being the most widely used technology. Phosphate tailings, a byproduct of phosphate ore beneficiation, are typically considered mining waste. However, they still contain significant amounts of magnesium. Through a series of methods, magnesium can be recovered, and the P2O5 grade can be increased, offering significant development potential in various industries, including chemical engineering.
[0003] Nano-magnesium oxide is a high-performance nanomaterial characterized by its small particle size, large specific surface area, high surface activity, and excellent adsorption performance. It can be used to remove heavy metal ions and organic pollutants. Nano-magnesium oxide also exhibits good stability and mechanical strength, making it suitable for high-temperature and high-power environments. Furthermore, it possesses flame-retardant, antibacterial, and corrosion-resistant properties, making it suitable as a catalyst or catalyst carrier in chemical reactions. In addition, nano-magnesium oxide demonstrates good biocompatibility in the pharmaceutical field, and can be used as a drug carrier, antibacterial dressing, and biosensors. The particle size of nano-magnesium oxide determines its applicability in different fields; smaller particle sizes are more suitable for applications requiring high activity and high adsorption performance, while larger particle sizes are better suited for scenarios requiring mechanical strength and stability.
[0004] Existing technology discloses a solid-state method for preparing nano-magnesium oxide, which utilizes basic magnesium carbonate for preparation. However, this invention suffers from uneven grinding pressure during manual or mechanical ball milling, resulting in a wide particle size distribution of the precursor basic magnesium carbonate, leading to agglomeration of the prepared nano-magnesium oxide.
[0005] The main problems with existing nano-magnesium oxide preparation technologies are uneven product dispersion, easy agglomeration, high impurity content, and low purity; furthermore, existing technologies do not disclose the reuse of phosphate tailings to prepare nano-magnesium oxide. Summary of the Invention
[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing nano-magnesium oxide. The method involves calcining phosphorus tailings to activate them, obtaining calcined tailings. Then, ammonium salts are reacted with the calcined tailings to enrich magnesium. Magnesium hydroxide precipitate is then uniformly formed using a hydrothermal method. Finally, nano-magnesium oxide is prepared by calcination. The prepared nano-magnesium oxide is uniformly dispersed and has high purity, providing a new approach for the effective disposal of phosphorus tailings, a major form of solid waste.
[0007] To achieve the above objectives, the present invention adopts the following technical solution:
[0008] This invention provides a method for preparing nano-magnesium oxide, comprising the following steps:
[0009] Phosphate tailings are calcined at 500–1200℃ to obtain calcined tailings.
[0010] The calcined tailings are added to an ammonium salt solution for reaction, filtered, and leaching residue is obtained.
[0011] The leaching residue is added back to the ammonium salt solution to react, yielding a mother liquor; the mother liquor is then evaporated and concentrated to obtain a concentrated solution.
[0012] The concentrate and dispersant are mixed and stirred, and then ammonia water is added to obtain a mixture.
[0013] The mixture was subjected to a hydrothermal reaction, filtered, washed, and dried to obtain the precursor.
[0014] The precursor was calcined to obtain nano-magnesium oxide.
[0015] Preferably, in the step of adding calcined tailings to an ammonium salt solution for reaction, filtering, and obtaining leaching residue, the ammonium salt in the ammonium salt solution includes at least one of ammonium chloride, ammonium nitrate, and ammonium sulfate, and the reaction temperature is 40-50°C and the reaction time is 20-60 min.
[0016] The concentration of the ammonium salt solution is 1.5–2 mol / L.
[0017] The mass ratio of ammonium salt solution to calcined tailings is (1.9–2.4):1.
[0018] Preferably, in the step of adding the leaching residue back into the ammonium salt solution to react and obtain the mother liquor, the ammonium salt in the ammonium salt solution includes at least one of ammonium chloride, ammonium nitrate, and ammonium sulfate, and the reaction temperature is 40-50°C and the reaction time is 20-60 min.
[0019] The concentration of the ammonium salt solution is 0.08–0.1 mol / L.
[0020] The mass ratio of the leaching residue to the ammonium salt solution is 1:(589-600).
[0021] Preferably, in the step of evaporating and concentrating the mother liquor to obtain the concentrated solution, the concentrated solution contains Mg 2+ The concentration is 0.2–0.5 mol / L.
[0022] Preferably, the dispersant includes at least one of polyethylene glycol 2000, EDTA-2Na, and sodium citrate.
[0023] Preferably, in the step of mixing the concentrate and the dispersant and then adding ammonia to obtain the mixture, the mass-to-volume ratio of the dispersant to the concentrate is (0.01-0.1) g:(80-100) mL.
[0024] The concentration of the ammonia solution is 1–1.5 mol / L;
[0025] The ammonia water contains NH3 and the concentrate contains Mg 2+ The molar ratio is (1~3.5):1.
[0026] Preferably, in the step of hydrothermal reaction of the mixture, the hydrothermal reaction temperature is 120-200°C and the time is 2-8 hours.
[0027] Preferably, in the step of calcining the precursor, the calcination temperature is 500-700℃ and the time is 1.5-2.5h.
[0028] Preferably, in the step of calcining the phosphate tailings at 500–1200°C, the calcination time is 0.5–2 hours.
[0029] Preferably, the mixture is subjected to a hydrothermal reaction, filtered, washed with water, then washed with ethanol, and dried to obtain the precursor;
[0030] Before calcining the phosphate tailings at 500–1200°C, the process also includes grinding the phosphate tailings and passing them through a 200–300 mesh sieve.
[0031] The method for preparing nano-magnesium oxide of the present invention has the following advantages compared with the prior art:
[0032] The method for preparing nano-magnesium oxide of this invention involves first calcining phosphorus tailings at 500–1200°C to activate them, obtaining calcined tailings. The calcined tailings are then added to an ammonium salt solution for reaction, filtered, and leached to obtain leaching residue. This leaching residue is then added back to the ammonium salt solution to obtain mother liquor, and magnesium is enriched in the calcined tailings using ammonium salt leaching. A hydrothermal reaction is then used to obtain a uniform magnesium hydroxide precipitate, which serves as the precursor. Finally, the precursor is calcined to obtain nano-magnesium oxide. The nano-magnesium oxide prepared by this method is uniformly dispersed and has high purity, providing a new approach for the effective disposal of phosphorus tailings, a major form of solid waste. The method for preparing nano-magnesium oxide of this invention uses magnesium derived from phosphorus tailings, making the raw materials readily available and inexpensive. The process is simple, and it yields uniformly dispersed and highly pure nano-magnesium oxide. Attached Figure Description
[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0034] Figure 1 This is a scanning electron microscope (SEM) image of the nano-magnesium oxide prepared in Example 1;
[0035] Figure 2 The particle size distribution diagram is shown for the nano-magnesium oxide prepared in Example 1.
[0036] Figure 3 This is a scanning electron microscope (SEM) image of the nano-magnesium oxide prepared in Example 2;
[0037] Figure 4 The image shows the XRD pattern of the nano-magnesium oxide prepared in Example 2.
[0038] Figure 5 This is a particle size distribution diagram of the nano-magnesium oxide prepared in Example 2. Detailed Implementation
[0039] To facilitate understanding of the present invention, a more comprehensive description of the invention will be provided below in conjunction with specific embodiments. Preferred embodiments of the invention are given in the specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.
[0040] The order in which the embodiments are described below is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.
[0041] This invention provides a method for preparing nano-magnesium oxide, comprising the following steps:
[0042] S1. Calcine the phosphorus tailings at 500-1200℃ to obtain calcined tailings;
[0043] S2. Add the calcined tailings to the ammonium salt solution for reaction, filter, and obtain leaching residue;
[0044] S3. Add the leaching residue back into the ammonium salt solution to react and obtain the mother liquor; evaporate and concentrate the mother liquor to obtain the concentrated solution.
[0045] S4. Mix the concentrate and dispersant, stir, and then add ammonia water to obtain a mixture.
[0046] S5. The mixture is subjected to a hydrothermal reaction, filtered, washed, and dried to obtain the precursor.
[0047] S6. The precursor is calcined to obtain nano-magnesium oxide.
[0048] The method for preparing nano-magnesium oxide of this invention involves first calcining phosphorus tailings at 500–1200°C to activate them, obtaining calcined tailings; then adding the calcined tailings to an ammonium salt solution for reaction, followed by filtration to obtain leaching residue; adding the leaching residue back to the ammonium salt solution for reaction to obtain mother liquor, and enriching the magnesium element in the calcined tailings using ammonium salt leaching; then using a hydrothermal reaction to obtain a uniform magnesium hydroxide precipitate, which serves as the precursor; finally, calcining the precursor to obtain nano-magnesium oxide. The nano-magnesium oxide prepared by this method is uniformly dispersed and has high purity, and provides a new approach for the effective disposal of phosphorus tailings, a major solid waste. The method for preparing nano-magnesium oxide of this invention uses magnesium derived from phosphorus tailings, making the raw materials readily available and inexpensive, and the process is simple, resulting in uniformly dispersed and highly pure nano-magnesium oxide particles.
[0049] In some embodiments, in the step of adding calcined tailings to an ammonium salt solution (specifically an aqueous solution) for reaction, filtering, and obtaining leaching residue, the ammonium salt in the ammonium salt solution includes at least one of ammonium chloride, ammonium nitrate, and ammonium sulfate, and the reaction temperature is 40-50°C and the reaction time is 20-60 min.
[0050] The concentration of the ammonium salt solution is 1.5–2 mol / L.
[0051] The mass ratio of ammonium salt solution to calcined tailings is (1.9–2.4):1.
[0052] In some embodiments, in the step of adding the leaching residue back into an ammonium salt solution (specifically an aqueous solution) to react and obtain a mother liquor, the ammonium salt in the ammonium salt solution includes at least one of ammonium chloride, ammonium nitrate, and ammonium sulfate, and the reaction temperature is 40-50°C and the reaction time is 20-60 min.
[0053] The concentration of the ammonium salt solution is 0.08–0.1 mol / L.
[0054] The mass ratio of leaching residue to ammonium salt solution is 1:(589-600).
[0055] In some embodiments, in the step of evaporating and concentrating the mother liquor to obtain a concentrated solution, the Mg in the concentrated solution... 2+ The concentration is 0.2–0.5 mol / L.
[0056] In some embodiments, the dispersant includes at least one of polyethylene glycol 2000, EDTA-2Na (disodium ethylenediaminetetraacetate), and sodium citrate.
[0057] In some embodiments, in the step of mixing the concentrate and the dispersant and stirring, and then adding ammonia water to obtain the mixture, the mass-volume ratio of the dispersant to the concentrate is (0.01-0.1) g:(80-100) mL.
[0058] The concentration of ammonia water is 1–1.5 mol / L;
[0059] NH3 in ammonia water and Mg in the concentrate 2+ The molar ratio is (1~3.5):1.
[0060] In some embodiments, in the step of subjecting the mixture to a hydrothermal reaction, the hydrothermal reaction temperature is 120–200°C and the time is 2–8 hours.
[0061] In some embodiments, the calcination step of the precursor is carried out at a temperature of 500–700°C for a time of 1.5–2.5 h.
[0062] In some embodiments, in the step of calcining the phosphate tailings at 500–1200°C, the calcination time is 0.5–2 h.
[0063] In some embodiments, the mixture is subjected to a hydrothermal reaction, filtered, washed with water, then washed with ethanol, and dried to obtain the precursor.
[0064] In some embodiments, before calcining the phosphate tailings at 500–1200°C, the phosphate tailings are further ground and passed through a 200–300 mesh sieve.
[0065] The following specific embodiments further illustrate the preparation method of nano-magnesium oxide according to the present invention. This section, in conjunction with specific embodiments, further explains the content of the present invention, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.
[0066] The chemical composition of the phosphorus tailings in the following examples and comparative examples is shown in Table 1 below. The contents in Table 1 are mass contents (%).
[0067] Table 1 - Chemical Composition of Phosphate Tailings
[0068]
[0069] Example 1
[0070] This embodiment provides a method for preparing nano-magnesium oxide, including the following steps:
[0071] S1. Grind the phosphate tailings and pass them through a 200-mesh sieve, then calcine them at 500℃ for 2 hours to obtain calcined tailings;
[0072] S2. Add the calcined tailings to a 1.5 mol / L NH4Cl solution, with a mass ratio of NH4Cl solution to calcined tailings of 2:1. React at 40℃ for 30 min, filter, and obtain leaching residue.
[0073] S3. Add the leaching residue back into a 0.08 mol / L ammonium sulfate solution, with a mass ratio of leaching residue to ammonium sulfate solution of 1:589. React at 35℃ for 40 min, filter, and obtain mother liquor (containing MgSO4); evaporate and concentrate the mother liquor to a MgSO4 concentration of 0.4 mol / L to obtain concentrated solution.
[0074] S4. Mix 90 mL of the concentrated solution with 0.06 g of dispersant (specifically EDTA-2Na) and stir. Then add 1 mol / L ammonia water to obtain a mixed solution. The NH3 in the ammonia water reacts with the Mg in the concentrated solution. 2+ The molar ratio is 2.5:1;
[0075] S5. The mixture was hydrothermally reacted at 160℃ for 3 hours, filtered, washed with water, then washed with ethanol, and dried to obtain the precursor.
[0076] S6. The precursor was calcined at 600℃ for 2 hours to obtain nano-magnesium oxide with an average particle size of 606nm.
[0077] Example 2
[0078] This embodiment provides a method for preparing nano-magnesium oxide, including the following steps:
[0079] S1. Grind the phosphate tailings and pass them through a 200-mesh sieve, then calcine them at 900℃ for 2 hours to obtain calcined tailings;
[0080] S2. Add the calcined tailings to a 1.5 mol / L NH4Cl solution, with a mass ratio of NH4Cl solution to calcined tailings of 2:1. React at 40℃ for 30 min, filter, and obtain leaching residue.
[0081] S3. Add the leaching residue back into a 0.08 mol / L ammonium sulfate solution, with a mass ratio of leaching residue to ammonium sulfate solution of 1:589. React at 35℃ for 40 min, filter, and obtain mother liquor (containing MgSO4); evaporate and concentrate the mother liquor to a MgSO4 concentration of 0.4 mol / L to obtain concentrated solution.
[0082] S4. Mix 90 mL of the concentrated solution with 0.1 g of dispersant (specifically sodium citrate) and stir. Then add 1 mol / L ammonia water to obtain a mixed solution. The NH3 in the ammonia water reacts with the Mg in the concentrated solution. 2+ The molar ratio is 2.5:1;
[0083] S5. The mixture was hydrothermally reacted at 180℃ for 3 hours, filtered, washed with water, then washed with ethanol, and dried to obtain the precursor.
[0084] S6. The precursor was calcined at 600℃ for 2 hours to obtain nano-magnesium oxide with an average particle size of 247nm.
[0085] Comparative Example 1
[0086] This embodiment provides a method for preparing nano-magnesium oxide, including the following steps:
[0087] S1. Grind the phosphate tailings and pass them through a 200-mesh sieve;
[0088] S2. Add the phosphate tailings that have passed through a mesh sieve to a 1.5 mol / L NH4Cl solution. The mass ratio of NH4Cl solution to phosphate tailings is 2:1. React at 40℃ for 30 min, filter, and obtain leaching residue.
[0089] S3. Add the leaching residue back into a 0.08 mol / L ammonium sulfate solution, with a mass ratio of leaching residue to ammonium sulfate solution of 1:589. React at 35℃ for 40 min, filter, and obtain mother liquor (containing MgSO4); evaporate and concentrate the mother liquor to a MgSO4 concentration of 0.4 mol / L to obtain concentrated solution.
[0090] S4. Mix 90 mL of the concentrated solution with 0.06 g of dispersant (specifically EDTA-2Na) and stir. Then add 1 mol / L ammonia water to obtain a mixed solution. The NH3 in the ammonia water reacts with the Mg in the concentrated solution. 2+ The molar ratio is 2.5:1;
[0091] S5. The mixture was hydrothermally reacted at 160℃ for 3 hours, filtered, washed with water, then washed with ethanol, and dried to obtain the precursor.
[0092] S6. The precursor was calcined at 600℃ for 2 hours to obtain nano-magnesium oxide.
[0093] Performance testing
[0094] Figure 1 This is a scanning electron microscope (SEM) image of the nano-magnesium oxide prepared in Example 1.
[0095] Figure 2 This is a particle size distribution diagram of the nano-magnesium oxide prepared in Example 1.
[0096] from Figures 1-2 It can be seen that the product has an uneven distribution, with the particle size mainly concentrated around 1000nm, an average particle size of 606nm, and a very low content of small-diameter particles.
[0097] Figure 3 This is a scanning electron microscope (SEM) image of the nano-magnesium oxide prepared in Example 2.
[0098] Figure 4 The image shows the XRD pattern of the nano-magnesium oxide prepared in Example 2.
[0099] Figure 5 This is a particle size distribution diagram of the nano-magnesium oxide prepared in Example 2.
[0100] in, Figure 2 and Figure 5 The particle size distribution was measured using a nanoparticle size analyzer. Because the magnesium oxide nanoparticles prepared in Example 1 were relatively large, the light intensity distribution was sensitive to large particles and could not directly reflect the actual particle content. Therefore, according to the Mie scattering ethics, the light intensity was converted into volume distribution. Figure 2 The vertical axis represents the volume distribution.
[0101] from Figures 3-5 It can be seen that the synthesis process of nano-magnesium oxide was relatively successful and the sample purity was high; Figure 5 The particle size of the nano-magnesium oxide prepared in Example 2 was measured. Figure 5 The medium steady state refers to the Brownian motion of the sample particles reaching equilibrium. The three curves represent three tests performed on the sample. The results of the three tests show that the three curves have similar shapes, mainly clustered around 200 nm, with a uniform particle size distribution and an average particle size of 247 nm.
[0102] The mass percentages of magnesium oxide, calcium oxide, hydrochloric acid insolubles, sulfate (calculated as SO4), iron (Fe), and chloride (calculated as Cl) in the nano-magnesium oxide prepared in Example 1 were determined, and the results are shown in Table 2 below.
[0103] Table 2 - Mass percentage of each component in the nano-magnesium oxide prepared in Example 1
[0104] Testing items Industry Standards Example 1 Magnesium oxide (MgO) wt / % ≥92 92.3 Calcium oxide (CaO) wt / % ≤2.0 1.6 Hydrochloric acid insoluble matter wt / % / 0.18 <![CDATA[Sulfate (calculated as SO4) wt / %]]> / 0.54 Iron (Fe) wt / % ≤0.10 0.06 Chloride (as Cl) wt / % ≤0.30 0.23
[0105] The mass percentages of magnesium oxide, calcium oxide, hydrochloric acid insolubles, sulfate (calculated as SO4), iron (Fe), and chloride (calculated as Cl) in the nano-magnesium oxide prepared in Example 2 were measured, and the results are shown in Table 3 below.
[0106] Table 3 - Mass percentage of each component in the nano-magnesium oxide prepared in Example 2
[0107] Testing items Industry Standards Example 2 Magnesium oxide (MgO) wt / % ≥92 95.6 Calcium oxide (CaO) wt / % ≤2.0 1.2 Hydrochloric acid insoluble matter wt / % / 0.14 <![CDATA[Sulfate (calculated as SO4) wt / %]]> / 0.45 Iron (Fe) wt / % ≤0.10 0.06 Chloride (as Cl) wt / % ≤0.30 0.15
[0108] The mass percentages of magnesium oxide, calcium oxide, hydrochloric acid insoluble matter, sulfate (calculated as SO4), iron (Fe), and chloride (calculated as Cl) in the nano-magnesium oxide prepared in Comparative Example 1 were determined, and the results are shown in Table 4 below.
[0109] Table 4 - Mass percentage of each component in the nano-magnesium oxide prepared in Comparative Example 1
[0110]
[0111]
[0112] As shown in Table 2, the magnesium oxide content in the nano magnesium oxide prepared in Example 1 can reach 92.3%, and its impurity content is also within the range of Class I standard indicators for industrial light magnesium oxide.
[0113] As shown in Table 3, the magnesium oxide content in the nano-magnesium oxide prepared in Example 2 can reach 95.6%, and its impurity content is also within the range of Class I standard indicators for industrial light magnesium oxide.
[0114] As shown in Table 4, the nano-magnesium oxide prepared in Comparative Example 1 cannot meet the industrial standard. Its magnesium oxide content is 78.7%, and the impurity content is higher than the industrial standard.
[0115] It is understood that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0116] The above are merely preferred embodiments of this application, and only specifically describe the technical principles of this application. These descriptions are only for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, as well as other specific embodiments of this application that can be conceived by those skilled in the art without creative effort, should be included within the scope of protection of this application.
Claims
1. A method for preparing nano-magnesium oxide, characterized in that, Includes the following steps: Phosphate tailings are calcined at 500–1200℃ to obtain calcined tailings. The calcined tailings are added to an ammonium salt solution for reaction, filtered, and leaching residue is obtained. The leaching residue is added back into the ammonium salt solution to react, yielding the mother liquor; The mother liquor is evaporated and concentrated to obtain a concentrated solution; The concentrate and dispersant are mixed and stirred, and then ammonia water is added to obtain a mixture. The mixture was subjected to a hydrothermal reaction, filtered, washed, and dried to obtain the precursor. The precursor was calcined to obtain nano-magnesium oxide.
2. The method for preparing nano-magnesium oxide as described in claim 1, characterized in that, In the step of adding calcined tailings to an ammonium salt solution for reaction, filtering, and obtaining leaching residue, the ammonium salt in the ammonium salt solution includes at least one of ammonium chloride, ammonium nitrate, and ammonium sulfate, and the reaction temperature is 40-50℃ and the reaction time is 20-60 min. The concentration of the ammonium salt solution is 1.5–2 mol / L. The mass ratio of ammonium salt solution to calcined tailings is (1.9–2.4):
1.
3. The method for preparing nano-magnesium oxide as described in claim 1, characterized in that, In the step of adding the leaching residue back into the ammonium salt solution to react and obtain the mother liquor, the ammonium salt in the ammonium salt solution includes at least one of ammonium chloride, ammonium nitrate, and ammonium sulfate, and the reaction temperature is 40-50℃ and the reaction time is 20-60 min. The concentration of the ammonium salt solution is 0.08–0.1 mol / L. The mass ratio of the leaching residue to the ammonium salt solution is 1:(589-600).
4. The method for preparing nano-magnesium oxide as described in claim 1, characterized in that, In the step of evaporating and concentrating the mother liquor to obtain a concentrated solution, the concentrated solution contains Mg 2+ The concentration is 0.2–0.5 mol / L.
5. The method for preparing nano-magnesium oxide as described in claim 1, characterized in that, The dispersant includes at least one of polyethylene glycol 2000, EDTA-2Na, and sodium citrate.
6. The method for preparing nano-magnesium oxide as described in claim 1, characterized in that, In the step of mixing the concentrate and the dispersant and stirring, then adding ammonia water to obtain the mixture, the mass-volume ratio of the dispersant to the concentrate is (0.01-0.1) g:(80-100) mL. The concentration of the ammonia solution is 1–1.5 mol / L; The ammonia water contains NH3 and the concentrate contains Mg 2+ The molar ratio is (1~3.5):
1.
7. The method for preparing nano-magnesium oxide as described in claim 1, characterized in that, In the step of carrying out a hydrothermal reaction of the mixture, the hydrothermal reaction temperature is 120-200℃ and the time is 2-8h.
8. The method for preparing nano-magnesium oxide as described in claim 1, characterized in that, In the step of calcining the precursor, the calcination temperature is 500-700℃ and the time is 1.5-2.5h.
9. The method for preparing nano-magnesium oxide as described in claim 1, characterized in that, In the step of calcining the phosphate tailings at 500–1200℃, the calcination time is 0.5–2 hours.
10. The method for preparing nano-magnesium oxide as described in claim 1, characterized in that, The mixture was subjected to a hydrothermal reaction, filtered, washed with water, then washed with ethanol, and dried to obtain the precursor. Before calcining the phosphate tailings at 500–1200°C, the process also includes grinding the phosphate tailings and passing them through a 200–300 mesh sieve.