Method for synchronously recycling iron resources and silicon resources in copper slag

Abstract

The present application relates to the field of solid waste resource utilization, and discloses a method for synchronously recovering iron resources and silicon resources in copper slag. The method comprises the following steps: mixing copper slag and molten salt to prepare dry composite briquettes; then, the temperature is raised and weak oxidizing gas CO2 is introduced for oxidation roasting; finally, the sample is subjected to alkali leaching and drying, and then magnetic separation is performed, so that the magnetic material and the non-magnetic material of the modified copper slag are separated, and the iron-rich concentrate is obtained, and the leaching solution contains aluminosilicate, which can be used as a precursor solution for synthesizing molecular sieves. Compared with the traditional magnetization roasting, the process of the present application is simple and easy to implement, and the magnetization transformation of the copper slag can be realized at a relatively low roasting temperature, and the separation of iron and silicon is realized by alkali leaching, and the iron resources and silicon resources in the copper slag can be synchronously recovered after magnetic separation; in addition, CO2 is reduced to CO during the oxidation of the copper slag, and a gas energy source is generated.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization, specifically to a method for simultaneously recovering iron and silicon resources from copper slag. Background Technology

[0002] Copper slag is a byproduct of copper smelting, primarily derived from flotation tailings, smelting slag, converter slag, and refining slag. Approximately 2-3 tons of copper slag are produced for every ton of refined copper produced. Copper slag is typically high in density, difficult to grind, and has a complex mineral phase composition. It mainly contains fir olivine, magnetite, small amounts of matte, and some metal oxides such as calcium oxide and aluminum oxide. Copper slag contains approximately 40% iron, making it a valuable secondary metallurgical resource. Efficiently recovering the iron resources from copper slag can effectively alleviate the current over-reliance on imported iron ore resources and achieve the healthy and efficient development of the metallurgical industry.

[0003] The extraction of iron from copper slag can be broadly classified into four categories: direct magnetic separation, wet magnetic separation, reduction magnetic separation, and oxidation magnetic separation.

[0004] Direct magnetic separation: This method uses methods such as ball milling to refine the particle size of copper slag, forcing the magnetic and non-magnetic substances to separate, and then obtains iron concentrate through magnetic separation. However, since the iron in copper slag mainly exists in the form of fir olivine, which has weak magnetism, the selected iron concentrate has a low content and low iron grade.

[0005] Wet leaching with magnetic separation involves leaching the roasted copper slag with acid or alkali to dissolve soluble non-magnetic substances, followed by magnetic separation of the slag sample. However, due to the high chemical stability of the fir olivine phase, leaching efficiency needs to be improved by increasing leaching pressure, leaching temperature, and leachate concentration. Furthermore, the acid leaching process involves significant iron dissolution, requiring the addition of H₂O₂ to promote iron precipitation.

[0006] Reduction-magnetic separation: A solid reducing agent or reducing gas is added to copper slag to reduce the iron-bearing mineral phase in the slag to elemental iron, which is then separated from gangue by magnetic separation. However, reduction-magnetic separation usually requires temperatures above 1000 degrees Celsius, resulting in high energy consumption and significant greenhouse gas emissions. Furthermore, excessive carbon reducing agent can lead to the formation of the byproduct Fe3C.

[0007] Oxidation-magnetic separation: The non-magnetic iron-bearing phase in copper slag is oxidized to magnetite (Fe3O4) in an oxidizing atmosphere, and then separated from the gangue by magnetic separation to obtain magnetic materials, thus enriching the iron element. When recovering iron using the molten oxidation method, CaO needs to be introduced to modify the composition of the copper slag, thereby releasing FeO from the fir olivine. Then, with the help of oxygen, the iron components in the slag are enriched into the magnetite phase. To achieve the aggregation and growth of the magnetite phase, the molten slag needs to have good fluidity; therefore, the molten oxidation process requires a high temperature (>1300℃) and high energy consumption. Low-temperature oxidation roasting requires strict control of the oxygen potential in the atmosphere; otherwise, the copper slag is easily over-oxidized, generating Fe2O3. Furthermore, the slow oxidation rate of copper slag at low temperatures also limits the application of the process.

[0008] Based on the above analysis, traditional methods such as direct magnetic separation, wet magnetic separation, reduction-magnetic separation, and molten oxidation-magnetic separation all have many shortcomings in the recovery of iron from copper slag. Therefore, developing a method that can efficiently separate and recover iron and silicon resources from copper slag would be of great significance for promoting the efficient utilization of copper slag. Summary of the Invention

[0009] In view of this, the purpose of the present invention is to provide a method for simultaneously recovering iron and silicon resources from copper slag, so that the method can use copper slag as raw material to simultaneously and efficiently recover iron oxide concentrate and aluminosilicate, while improving the recovery rate and grade of iron oxide concentrate.

[0010] To solve the aforementioned technical problems, or at least partially solve them, the present invention provides a method for solving the aforementioned technical problems, or at least partially solves them. As a first aspect of the present invention, a method for simultaneously recovering iron and silicon resources from copper slag is provided, comprising:

[0011] Step 1: Add molten salt and dispersion medium to copper slag, mix well and obtain composite agglomerates;

[0012] Step 2: The composite agglomerate is oxidized and calcined by introducing carbon dioxide gas in a protective gas atmosphere;

[0013] Step 3: The calcined composite agglomerates are subjected to alkaline leaching, centrifuged, and precipitate and filtrate are obtained. The filtrate contains aluminosilicate and is used as a precursor solution for the synthesis of 4A molecular sieve.

[0014] Step 4: After precipitation and magnetic separation, ferric oxide concentrate is obtained.

[0015] Optionally, the molten salt includes one or more of hydroxides, chlorides, sulfates, and carbonates; further optionally, the carbonate includes sodium carbonate and / or potassium carbonate.

[0016] Optionally, the dispersion medium is anhydrous ethanol.

[0017] Optionally, the volume ratio of the protective gas to carbon dioxide is (100-200):(10-100); further optionally, the protective gas is an inert gas.

[0018] Optionally, the oxidative calcination temperature is 600-850℃ and the time is 1-3h.

[0019] Optionally, the alkaline leaching includes: immersing the calcined composite agglomerate in an alkaline solution and stirring. Further optionally, the alkaline solution includes a sodium hydroxide solution.

[0020] Optionally, step 4 includes:

[0021] The precipitate is ground into powder, mixed with water, ball-milled, and then subjected to wet magnetic separation to obtain iron oxide concentrate.

[0022] Compared with existing technologies for extracting iron from copper slag, the present invention has at least the following advantages:

[0023] 1. Compared with existing direct magnetic separation and wet magnetic separation methods, the current direct magnetic separation method can only extract a small amount of iron(III) oxide from copper slag through fine grinding and adjusting the magnetic field strength, but cannot recover the iron element from the fir olivine in the copper slag. Wet magnetic separation requires pressurization, increased temperature, and leachate concentration to promote the dissolution of fir olivine. This invention, however, modifies the fir olivine in copper slag by introducing carbonate molten salt, resulting in an aluminosilicate phase that is more easily dissolved. Furthermore, magnetic separation yields iron concentrate with a higher iron content.

[0024] 2. Compared with existing reduction-magnetic separation and melt oxidation-magnetic separation methods, both require higher reaction temperatures and longer reaction times. Reduction methods generate large amounts of carbon dioxide, while melt oxidation methods consume large amounts of oxygen and require strict control of the cooling rate, which does not meet the goals of energy conservation and emission reduction. This invention, however, by adding composite molten salt, achieves the transformation of fir olivine into magnetite at a lower temperature (e.g., 750℃) and a shorter reaction time (e.g., 1 hour). Then, with the aid of alkaline leaching, efficient separation of iron and silicon is achieved, generating clean energy CO while consuming CO2.

[0025] 3. The method of the present invention involves alkaline leaching followed by magnetic separation, which separates the magnetic and non-magnetic substances in the modified copper slag to obtain iron-rich concentrate. The leachate contains aluminosilicates, which can be used as a precursor for the synthesis of molecular sieves, thus achieving the goal of simultaneously recovering iron and silicon resources from the copper slag. Attached Figure Description

[0026] Figure 1The figure shows the change in CO generation rate with temperature during the oxidation process of copper slag in a CO2 atmosphere; the molten salt is 58 mol% Na2CO3 + 42 mol% K2CO3.

[0027] Figure 2 The image shows the XRD analysis results of copper slag after oxidation in CO2 atmosphere for 1 hour, oxidation modification with the addition of composite molten salt for 1 hour, and alkaline leaching of the oxidized copper slag; the molten salt is 58 mol% Na2CO3 + 42 mol% K2CO3.

[0028] Figure 3 The image shows a 4A molecular sieve obtained by mixing sodium aluminate with alkaline leaching filtrate of oxidized copper slag as a precursor solution and aging it at 90 degrees Celsius for 8 hours. Detailed Implementation

[0029] This invention discloses a method for simultaneously recovering iron and silicon resources from copper slag. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired result. It is particularly important to note that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The method of this invention has been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods described herein without departing from the content, spirit, and scope of this invention to implement and apply the technology of this invention.

[0030] In a first aspect of the invention, a method for simultaneously recovering iron and silicon resources from copper slag includes:

[0031] Step 1: Add molten salt and dispersion medium to copper slag, mix well, and dry to obtain composite lumps;

[0032] Step 2: The composite agglomerate is oxidized and calcined by introducing carbon dioxide gas in a protective gas atmosphere;

[0033] Step 3: The calcined composite agglomerates are subjected to alkaline leaching, centrifuged, and precipitate and filtrate are obtained. The filtrate contains aluminosilicate and is used as a precursor solution for the synthesis of 4A molecular sieve.

[0034] Step 4: After precipitation and magnetic separation, ferric oxide concentrate is obtained.

[0035] In some embodiments of the present invention, the diameter of the composite agglomerate is 1-4 cm; in other embodiments of the present invention, the diameter of the composite agglomerate is 1-2 cm.

[0036] In some embodiments of the present invention, the molten salt has multiple functions, such as: ① reducing the temperature required for the oxidation modification of copper slag, reducing the oxidation activation energy of fir olivine, and increasing the activity of ferrous oxide; ② enhancing the enrichment and growth of magnetite; ③ releasing SiO2 from fir olivine and converting it into soluble aluminosilicates. Figure 2 The XRD results show that the copper slag without the addition of composite molten salt still contains a large amount of fir olivine after 1 hour of oxidation, while after adding 30wt% composite molten salt, all the fir olivine mineral phase in the copper slag is converted into Fe3O4, and aluminosilicate is obtained at the same time. The molten salt may include one or more of hydroxides, hydrochlorides, sulfates, and carbonates, and the amount used is 10-40% of the mass of the copper slag. In some other embodiments of the present invention, it has been found that the use of carbonates in the recycling process is more stable than other molten salts and does not cause pollution. Therefore, the molten salt of the present invention is selected from carbonates, including sodium carbonate and / or potassium carbonate. In some other embodiments of the present invention, the molten salt is sodium carbonate and potassium carbonate, and the molar percentage ratio of sodium carbonate and potassium carbonate is (1-99):(99-1), or (20-80):(80-20), or (40-60):(60-40), or (50-60):(50-40). In some other embodiments of the present invention, the molar percentage ratio of sodium carbonate and potassium carbonate is 58:42.

[0037] In some embodiments of the present invention, carbon dioxide is used as a weak oxidizing atmosphere to oxidize copper slag, and the added molten salt can promote the efficient oxidation of copper slag by carbon dioxide under low temperature conditions. This not only reduces process energy consumption and avoids copper slag melting, but also ensures that the iron-containing mineral phase in the copper slag is not over-oxidized to ferric oxide. In other embodiments of the present invention, the volume ratio of the protective gas to carbon dioxide is (100-200):(10-100), or it can be (120-160):(40-80). In other embodiments of the present invention, the volume ratio of the protective gas to carbon dioxide is 120:80 or 160:40.

[0038] In some other embodiments of the present invention, the protective gas is an inert gas, such as argon, xenon, krypton, radon, etc.

[0039] In some embodiments of the present invention, the dispersion medium used to make composite agglomerates can be a commonly used organic solvent, such as anhydrous ethanol, which can be removed after the composite agglomerates are dried. The amount used should be such that agglomerates can be formed.

[0040] In some embodiments of the present invention, it can be seen from the results of the change in CO generation rate with temperature during the oxidation process of copper slag in a CO2 atmosphere (see [link to relevant documentation]). Figure 1On the one hand, the ferrolithium phase in the copper slag is oxidized by CO2 to generate Fe3O4 and SiO2, and on the other hand, CO2 is reduced to obtain CO gas. Figure 1 The results show that the oxidation rate of copper slag in a CO2 atmosphere without the addition of molten salt is extremely slow. However, with the addition of molten salt, the CO generation rate increases rapidly when the roasting temperature is above 600 degrees Celsius. This indicates that molten salt can significantly improve the oxidation rate of fir olivine in copper slag, enabling its efficient conversion to Fe3O4. Based on the above results, the oxidation roasting temperature described in this invention is 600-850 degrees Celsius, and the time is 1-3 hours. The temperature can also be 650-800 degrees Celsius, for example, 650 degrees Celsius, 660 degrees Celsius, 670 degrees Celsius, 680 degrees Celsius, 690 degrees Celsius, 700 degrees Celsius, 710 degrees Celsius, 720 degrees Celsius, 730 degrees Celsius, 740 degrees Celsius, 750 degrees Celsius, 760 degrees Celsius, 780 degrees Celsius, 790 degrees Celsius, or 800 degrees Celsius; the time can be 1 hour, 2 hours, or 3 hours.

[0041] In some embodiments of the present invention, alkaline leaching can be used to dissolve and remove the aluminosilicate phase from the copper slag, such as... Figure 2 The XRD results show that after alkaline leaching of the oxidized copper slag, the aluminosilicate phase in the copper slag was basically dissolved and removed. The filtrate after alkaline leaching can be used as a precursor for the synthesis of 4A molecular sieves. For example, using the filtrate after alkaline leaching as a precursor, mixing it with sodium aluminate, and aging it at 90 degrees Celsius for 8 hours yields 4A molecular sieves. More specifically, according to the composition of 4A molecular sieves (Na2O×Al2O3×SiO2×4.5H2O), sodium aluminate is added to the filtrate, and the mixture is aged at 90 degrees Celsius for 8 hours in a hydrothermal reactor. The appearance of the prepared 4A molecular sieve is shown in the figure. Figure 3 .

[0042] In some other embodiments of the present invention, the alkaline leaching includes: immersing the calcined composite agglomerates in an alkaline solution and stirring. More specifically, the calcined composite agglomerates are immersed in the alkaline solution and stirred for 0.5-1 hour, with a solid-liquid ratio of 10-50 g / L, for example 20 g / L, 30 g / L, or 40 g / L, at a temperature of 80±10℃.

[0043] In some embodiments of the present invention, the alkaline solution comprises a sodium hydroxide solution; in other embodiments of the present invention, the concentration of the sodium hydroxide solution is 0.5 mol / L to 1.5 mol / L.

[0044] In some embodiments of the present invention, step 4 includes:

[0045] The precipitate is ground into powder, mixed with water, ball-milled, and then subjected to wet magnetic separation to obtain iron oxide concentrate.

[0046] In some other embodiments of the present invention, the precipitated powder is mixed with water in equal mass to form a slurry, which is then ball-milled and wet magnetic separation is performed under a magnetic field strength of 100-160 mT to obtain iron oxide concentrate.

[0047] In certain embodiments of the present invention, the present invention provides a specific method for simultaneously recovering iron and silicon resources from copper slag, comprising:

[0048] (1) Add 10%-40wt% of composite molten salt to copper slag, mix well, and use anhydrous ethanol as the dispersion medium to prepare composite lumps with a diameter of 1-4 cm. Place the lumps in a drying oven to dry them to obtain dry lumps.

[0049] (2) Place the dry lumps obtained in step (1) into an alumina crucible and place the crucible in the reaction zone of a tube furnace. Inert gas is introduced into one side of the tube furnace to remove air from the furnace.

[0050] (3) After removing impurities in step (2), oxidative roasting is carried out in a weak oxidizing atmosphere of CO2. The roasting temperature is 750℃-850℃ and the roasting time is 1-3 hours. After roasting, the mixture is naturally cooled to room temperature in an argon atmosphere.

[0051] (4) Take out the oxidized lumps from step (3) and grind them through a 200-mesh sieve;

[0052] (5) The powder ground in step (4) is leached with alkali to dissolve the non-magnetic aluminosilicate phase and disrupt the intercalation of gangue and magnetite phases.

[0053] (6) Centrifuge the solution after step (5). The filtrate contains dissolved aluminosilicates and can be used as a precursor for 4A molecular sieve.

[0054] (7) After the precipitate is mixed with water, it is ball-milled and then wet magnetic separation is carried out in a magnetic separator to obtain high-grade iron oxide.

[0055] In specific embodiments of the present invention, unless otherwise specified, the experimental environment and parameter conditions of each group in the test are kept consistent. In the present invention, the copper slag is the copper slag obtained after extracting copper from copper sulfide concentrate by pyrometallurgy.

[0056] The following is a further explanation of a method for simultaneously recovering iron and silicon resources from copper slag provided by the present invention.

[0057] Example 1:

[0058] The iron content of the copper slag used was 42.01%, and the Fe content was... 2+ Content 33.80%, mostly Fe 2+It exists in the form of fir olivine. Copper slag with 30wt% composite molten salt (58mol% Na2CO3 + 42mol% K2CO3) was pressed into composite lumps with a diameter of 10-20mm. After drying in a vacuum drying oven, the lumps were calcined at 750℃ in a weak oxidizing atmosphere (Ar:CO2 = 160:40) for 1h. The composite lumps were then cooled in the furnace with argon. After cooling, the lumps were crushed and ground to a particle size of less than 200 mesh. The sample was placed in a 1.5 mol / L NaOH solution with a solid-liquid ratio of 20 g / L and stirred at 300 r / min for 1 h in a water bath at 80 °C. Then, centrifugation was performed to obtain filter residue (the filtrate contains aluminosilicates, which can be used as a precursor liquid for molecular sieves). After alkali leaching, the filter residue was dried and ground, and then ball-milled in a conical ball mill under the condition of a slurry concentration of 50% (the powder and water were mixed in equal masses). The slurry was then magnetically separated in a magnetic separator with a magnetic field strength of 160 mT to obtain magnetic concentrate (ferric oxide concentrate). The grade of the magnetic concentrate was 65.18%, and the iron recovery rate was 85.88%.

[0059] Preparation of 4A molecular sieve: Due to the high silicon and low aluminum content in copper slag (SiO2 31 wt.%, Al2O3 5.44 wt.%), with a Si:Al molar ratio of 4.8, sodium aluminate was added to the filtrate according to the composition of 4A molecular sieve (Na2O×Al2O3×SiO2×4.5H2O) to achieve a silicon-to-aluminum ratio of 1:1 in the precursor solution. The solution was then aged at 90°C for 8 hours in a hydrothermal reactor, followed by filtration. The resulting solid was dried to obtain 4A molecular sieve. Figure 3 ).

[0060] Example 2:

[0061] Copper slag with iron content of 40.71%, Fe 2+ Content 34.45%, mostly Fe 2+ It exists in the form of fir olivine. Copper slag with 30 wt% sodium carbonate was pressed into composite agglomerates with a diameter of 10-20 mm. After drying in a vacuum drying oven, the agglomerates were calcined at 850 °C in a weak oxidizing atmosphere (Ar:CO2 = 140:60) for 1 h, and then cooled in the furnace with argon. After cooling, the agglomerates were crushed and ground to a particle size of less than 200 mesh. The sample was placed in a 0.5 mol / L NaOH solution with a solid-liquid ratio of 30 g / L and stirred at 300 r / min for 1 h in a water bath at 80 °C. The solid-liquid mixture was then centrifuged at 3000 r / min for 6 min to obtain the filter residue. After the filter residue from the alkali leaching was dried and ground, the resulting powder was ball-milled in a conical ball mill under the condition of a slurry concentration of 50% (the powder and water were mixed in equal masses). Then, it was magnetically separated in a magnetic separator with a magnetic field strength of 160mT to obtain magnetic concentrate (ferric oxide concentrate). The grade of the magnetic concentrate was 57.28%, and the iron recovery rate was 70.34%.

[0062] Example 3:

[0063] Copper slag with iron content of 41.71%, Fe 2+ Content 31.74%, mostly Fe 2+ It exists in the form of fir olivine. Copper slag with 30 wt% potassium carbonate was pressed into composite agglomerates with a diameter of 10-20 mm. After drying in a vacuum drying oven, the agglomerates were calcined at 800 °C in a weak oxidizing atmosphere (Ar:CO2 = 120:80) for 1 h, and then cooled in the furnace with argon. After cooling, the agglomerates were crushed and ground to a particle size of less than 200 mesh. The sample was placed in a 1.0 mol / L NaOH solution with a solid-liquid ratio of 30 g / L and stirred at 300 r / min for 1 h in a water bath at 80 °C. The mixture was then centrifuged at 3000 r / min for 6 min to separate the solid and liquid phases and obtain the filter residue. After the filter residue from the alkali leaching was dried and ground, the resulting powder was ball-milled in a conical ball mill at a slurry concentration of 50% (the powder and water were mixed in equal masses). Then, it was magnetically separated in a magnetic separator with a magnetic field strength of 160mT to obtain magnetic concentrate (ferric oxide concentrate). The grade of the magnetic concentrate was 71.35%, and the iron recovery rate was 62.95%.

[0064] Comparative Example 1:

[0065] Copper slag with iron content of 40.34%, Fe 2+ Content 32.78%, mostly Fe 2+ It exists in the form of fir olivine. Copper slag with 40 wt% added composite molten salt (58 mol% Na2CO3 + 42 mol% K2CO3) was pressed into composite agglomerates with a diameter of 10-20 mm. After drying in a vacuum drying oven, the agglomerates were calcined at 750 °C in a weak oxidizing atmosphere (Ar:CO2 = 120:80) for 1 h, and then cooled in the furnace with argon. After cooling, the agglomerates were crushed and ground to a particle size of less than 200 mesh. The sample was placed in deionized water with a solid-liquid ratio of 40 g / L and stirred at 300 r / min for 1 h in a water bath at 80 °C. After centrifugation at 3000 r / min for 6 min, the filter residue was collected. After drying and grinding, the resulting powder was ball-milled in a conical ball mill under the condition of 50% slurry concentration (the powder and water were mixed in equal mass). Then, it was magnetically separated in a magnetic separator with a magnetic field strength of 120mT to obtain magnetic concentrate (Fe3O4 concentrate). The grade of the magnetic concentrate was 52.71% and the iron recovery rate was 60.92%.

[0066] Comparative Example 2:

[0067] The difference from Example 1 is that no composite molten salt was added. The grade of the magnetic concentrate was 42.76%, and the iron recovery rate was 56.08%.

[0068] Comparative Example 3:

[0069] Compared to Example 1, the difference lies in the use of water leaching instead of alkaline leaching. The grade of the magnetic concentrate was 48.51%, and the iron recovery rate was 59.81%.

[0070] Experimental example:

[0071] The relevant parameter data of each embodiment and comparative example are summarized, and the filter residues obtained after alkali leaching / water leaching of each embodiment and comparative example are analyzed by XRF. The results are shown in Table 1 and Table 2, respectively.

[0072] Table 1. XRF results of filter residues obtained after alkali leaching / water leaching (calculated in oxide form)

[0073]

[0074] Table 1 lists the composition of the filter residue obtained after copper slag oxidation followed by water leaching and alkaline leaching. The comparison shows that alkaline leaching is more effective at removing silicon and aluminum oxides from the copper slag than water leaching. Analysis comparing the treatment groups with and without molten salt reveals that molten salt oxidation modification can break down the fir olivine in the copper slag, significantly increasing the solubility of silicon and aluminum in the slag.

[0075] Table 2

[0076]

[0077] Combined with Table 2 Figure 2 It can be assumed that when molten salt is not added, the iron in the copper slag is difficult to be completely oxidized to iron(III) oxide in a short time, resulting in low iron recovery rate and iron grade; when alkaline leaching is not used, the oxidized copper slag cannot achieve the separation of aluminosilicate phase and magnetic material.

[0078] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for simultaneously recovering iron and silicon resources from copper slag, characterized in that, include: Step 1: Add molten salt and dispersion medium to copper slag, mix well to obtain composite agglomerates; the molten salt is sodium carbonate and potassium carbonate, with a molar percentage ratio of (40-60):(60-40). Step 2: The composite agglomerate is oxidized and calcined by introducing carbon dioxide gas in a protective gas atmosphere; the oxidation and calcination temperature is 600-750℃ and the time is 1-3h. Step 3: The calcined composite agglomerates are subjected to alkaline leaching, centrifuged, and precipitate and filtrate are obtained. The filtrate contains aluminosilicate and is used as a precursor solution for the synthesis of 4A molecular sieve. Step 4: After precipitation and magnetic separation, ferric oxide concentrate is obtained.

2. The method according to claim 1, characterized in that, The dispersion medium is anhydrous ethanol.

3. The method according to claim 1, characterized in that, The volume ratio of the protective gas to carbon dioxide is (100-200):(10-100).

4. The method according to claim 1 or 3, characterized in that, The protective gas is an inert gas.

5. The method according to claim 1, characterized in that, The alkaline leaching includes: The roasted composite agglomerate was soaked in an alkaline solution and stirred.

6. The method according to claim 5, characterized in that, The alkaline solution includes a sodium hydroxide solution.

7. The method according to claim 1, characterized in that, Step 4 includes: The precipitate is ground into powder, mixed with water, ball-milled, and then subjected to wet magnetic separation to obtain ferric oxide concentrate.

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