A method for recovering magnetite from reconstituted copper residue

Abstract

The application discloses a method for recovering magnetite from restructured copper residue, comprising the following steps: analyzing the microstructure of the restructured copper residue, and measuring the hardness value of the magnetite and the magnesium-based silicate matrix; crushing the restructured copper residue into powdery residue, and then performing magnetic separation to obtain magnetite I; drying the magnetite I, crushing the dried magnetite I, analyzing the microstructure of the crushed magnetite I, determining the dissociation degree of the magnetite, and then performing magnetic separation to obtain magnetite II; repeating the drying-crushing-microstructure analysis-magnetic separation steps to sequentially obtain magnetite III and magnetite IV. The application clarifies the embedded characteristics of the magnetite and the magnesium-based silicate in the restructured copper residue through microstructure analysis, lays a foundation for dissociation of the magnetite and the magnesium-based silicate through hardness analysis, effectively improves the single dissociation degree and grade of the magnetite through a multi-stage crushing-magnetic separation process, and realizes effective improvement of the iron component recovery index in the copper residue.

Description

Technical Field

[0001] This invention relates to the field of copper slag treatment technology, and more specifically to a method for recovering magnetite from reconstituted copper slag. Background Technology

[0002] An effective method for recovering iron components from bulk industrial solid waste copper slag is to oxidize the iron-containing phases in the slag to magnetite (Fe3O4), and then dissociate and magnetically separate it from the silicate matrix, thereby recovering the iron components in the form of Fe3O4 mineral. It has been reported that the silicates in copper slag and its reconstructed products are mainly dicalcium silicate (Ca2SiO4) or common pyroxene (CaMgSi2O6). Compared with the high hardness of magnetite, dicalcium silicate and common pyroxene are both relatively soft minerals. Therefore, there has been considerable research on the dissociation and separation of magnetite from these two minerals, and relatively ideal recovery indicators have been obtained.

[0003] In the prior art, such as Chinese invention patent application CN119592784A (publication date March 11, 2025), a method for extracting iron from copper slag by magnetic separation and its application are disclosed. The method includes the following steps: mixing copper slag and a calcium oxide-based additive to obtain mixed copper slag, wherein the calcium oxide-based additive includes calcium oxide and / or calcium oxide raw materials, the calcium oxide raw materials being able to generate calcium oxide through heating, and the amount of calcium oxide-based additive added satisfying the following: the total mass of primary calcium oxide and / or generated calcium oxide is 29%–47% of the mass of fir olivine in the copper slag; the calcium oxide raw materials include calcium carbonate and / or calcium sulfate; heating the mixed copper slag to 1250–1800℃ and holding it at that temperature for 30–120 minutes to obtain modified copper slag; the modified copper slag is then subjected to slow cooling, crushing, and magnetic separation to obtain iron. This invention enriches iron in the liquid phase, fundamentally achieving a significant increase in the iron resource recovery rate from copper slag.

[0004] For example, Chinese invention patent application CN120651693A (published on September 16, 2025) discloses a composite alkali modifier for enhancing the resource utilization of copper slag and its application method. The method includes mixing CaO and MgO to form a composite alkali modifier; weighing the composite alkali modifier to achieve a certain relationship with the amount of SiO2 in the copper slag; uniformly mixing the composite alkali modifier with the copper slag to obtain modified copper slag; heating the modified copper slag to a molten state to obtain molten slag; keeping the molten slag at a constant temperature and continuously blowing in oxidizing gas for oxidation to obtain reconstituted slag; cooling the reconstituted slag to room temperature to obtain cooled slag; crushing the cooled slag and performing magnetic separation to obtain magnetite as the magnetic material and silicates as the non-magnetic material. The composite alkali modifier composed of CaO and MgO modifies the copper slag, causing it to oxidize in a molten state, enriching the Fe component in the slag into magnetic magnetite without generating hematite, thus achieving efficient enrichment of the iron component in the copper slag and laying the foundation for the reduction and resource utilization of copper slag.

[0005] For example, Chinese invention patent application CN110156353A (published on August 23, 2019) discloses a method and application for the joint treatment of copper slag and magnesium slag. Industrial copper slag and self-pulverized magnesium slag are mixed in a mass ratio of (50-90):100 to obtain mixed slag. The mixture is then finely ground to below 200 mesh, mixed evenly, and pressed into a cake shape to obtain cake-shaped mixed slag. The cake-shaped mixed slag is placed in a muffle furnace and heated to 1100-1300℃ in an air atmosphere and then roasted at a constant temperature for 1-3 hours. After roasting, the sample is taken out, cooled with compressed air, and then finely ground and magnetically separated to obtain iron-rich concentrate and silicate-rich tailings.

[0006] Existing technologies for recovering iron components from copper slag mostly focus on the mineral phase regulation during the oxidation process of modified copper slag. There is relatively little research on the dissociation characteristics and separation properties of iron-containing and silicon-containing phases in the oxidation products. Ignoring the difference in hardness between magnetite and silicates leads to unsatisfactory indicators in subsequent magnetic separation processes. Therefore, most studies on the dissociation and separation of magnetite in reconstructed copper slag only provide crushing particle size and magnetic separation intensity, while rarely mentioning the specific magnetic separation process and the phase composition of the magnetic separation products.

[0007] In the limited reports on magnetic separation of copper slag oxidation products, most studies focus on the enrichment of magnetite, while there are few studies on the composition, hardness and intercalation relationship of silicates with magnetite, which are closely related to the recovery of iron components in copper slag.

[0008] Therefore, there is an urgent need for a separation method that, based on mineralogical analysis of reconstructed copper slag, involves crushing and magnetic separation to form a specific separation method for the dissociation and separation of magnetite and forsterite in reconstructed copper slag. Summary of the Invention

[0009] To address the above technical problems, this invention provides a method for recovering magnetite from reconstructed copper slag, comprising the following steps: Step S1: Analyze the microstructure of the reconstructed copper slag, determine the hardness values ​​of magnetite and magnesium silicate matrix in the reconstructed copper slag, crush the reconstructed copper slag into powder, and obtain the magnetic mineral particles by magnetic separation, which is magnetite I. Step S2: Dry magnetite I, crush the dried magnetite I, analyze the microstructure of the crushed magnetite I, determine the degree of liberation of magnetite I, and then perform magnetic separation to obtain magnetite II; Step S3: Dry magnetite II, crush the dried magnetite II, analyze the microstructure of the crushed magnetite II, determine the degree of liberation of magnetite II, and then perform magnetic separation to obtain magnetite III. Step S4: Dry magnetite III, crush the dried magnetite III, analyze the microstructure of the dried magnetite III, determine the degree of liberation of magnetite III, and then perform magnetic separation to obtain magnetite IV.

[0010] The method for recovering magnetite from reconstituted copper slag in this invention involves performing microstructural analysis on the magnetite product obtained in the previous recovery stage before each recovery stage. This accurately determines the degree of liberation of the magnetite within it, and based on the analysis results of the degree of liberation, the crushing particle size and magnetic separation parameters are adjusted accordingly to achieve stepwise liberation and enrichment. This results in magnetite IV with a high grade and recovery rate. This method overcomes the problems of low recovery rate and poor grade caused by insufficient magnetite liberation in traditional single crushing and magnetic separation processes, significantly improving the efficiency and economic value of recovering magnetite from reconstituted copper slag. The degree of liberation mentioned in this invention refers to the percentage by mass of completely monomeric magnetite particles out of the total magnetite (monomers + intergrowths), reflecting the extent to which magnetite is separated from silicate gangue.

[0011] The reconstructed copper slag is a cooling slag obtained by modifying and oxidizing copper slag with MgO. Its mineral phase is mainly composed of magnetite and forsterite, and the mass of MgO is 5-15% of the weight of the reconstructed copper slag. Unless otherwise specified, the specific source and modification method of the reconstructed copper slag are not particularly limited in this invention.

[0012] Hardness values ​​can be determined using well-known hardness testing methods in the art, such as Vickers hardness, Rockwell hardness, or Brinell hardness. Unless otherwise specified, the specific method for determining hardness values ​​is not particularly limited in this invention.

[0013] The crushing operation can employ one or more of the following: planetary ball mill, cone crusher, impact crusher, hammer crusher, and roller crusher. Unless otherwise specified, the specific type of equipment used for crushing is not particularly limited in this invention.

[0014] Furthermore, step S5 is included: drying the powdered magnetite IV to obtain dry-based magnetite IV. By adding a final drying step, a nearly moisture-free dry-based magnetite product can be obtained, which facilitates subsequent transportation, storage, or direct sale as a product, thereby improving the product's practicality and commercial value.

[0015] Furthermore, the moisture content of dried magnetite I, magnetite II, magnetite III, and magnetite IV is all <0.1%.

[0016] Furthermore, step S1 includes the following steps: Step S11: Analyze the microstructure of the reconstructed copper slag to determine the intercalation characteristics of magnetite and magnesium silicate matrix; Step S12: Perform hardness testing on the reconstructed copper slag to determine the hardness values ​​of the magnetite and magnesium silicate matrix; Step S13: Crush the reconstructed copper slag into powdery slag with a particle size of -80 to -70 μm; Step S14: The powdered slag is subjected to wet magnetic separation in a Davis tube with a magnetic induction intensity of 280-320 mT. The obtained powdered magnetic fraction is magnetite I. As a preferred embodiment of the present invention, by setting a specific crushing particle size of -74 μm and a magnetic induction intensity of 280-320 mT in step S1, magnetite and magnesium silicate matrix can be initially and effectively separated in the first crushing and magnetic separation stage, obtaining magnetite I product with relatively ideal grade and recovery rate, providing a good raw material basis for subsequent multi-stage enrichment.

[0017] Furthermore, step S2 includes the following steps: Step S21: Dry magnetite I in a vacuum drying oven at 60℃~80℃ for 6h~10h to obtain dry-basis magnetite I (moisture content <0.1%). Step S22: Crush dry-based magnetite I to a particle size of -50μm; Step S23: Perform microstructural analysis on dry-based magnetite I to determine if its degree of liberation is greater than 50%. If not, crush magnetite I again until the degree of liberation of the magnetite is greater than 50%. Step S24: Wet magnetic separation is performed in a Davis tube with a magnetic induction intensity of 230-270 mT. The obtained powdered magnetic fraction is magnetite II. As a preferred embodiment of the present invention, by setting a specific crushing particle size of -50 μm and a magnetic induction intensity of 230-270 mT in step S2, and by adaptively adjusting the crushing and magnetic separation parameters based on the analysis results of the liberation degree of magnetite I in step S22, the magnetite particles that have not yet been fully liberated in magnetite I can be further liberated and enriched, effectively improving the grade of magnetite II.

[0018] Furthermore, step S3 includes the following steps: Step S31: Dry magnetite II in a vacuum drying oven at 60℃~80℃ for 6h~10h to obtain dry-basis magnetite II (moisture content <0.1%). Step S32: Crush dry-based magnetite II to a particle size of -38μm; Step S33: Perform microstructural analysis on dry-based magnetite II to determine whether its degree of liberation is greater than 65%. If not, crush magnetite II again until the degree of liberation of the magnetite is greater than 65%. Step S34: Wet magnetic separation is performed in a Davis tube with a magnetic induction intensity of 180-220 mT, and the obtained powdered magnetic fraction is magnetite III. As a preferred embodiment of the present invention, by setting a specific crushing particle size of -38 μm and a magnetic induction intensity of 180-220 mT in step S3, and by adaptively adjusting the crushing and magnetic separation parameters based on the analysis results of the liberation degree of magnetite II in step S32, the fine-grained magnetite encapsulated in the magnesium silicate matrix in magnetite II can be further liberated and enriched, and the grade of magnetite III is further improved compared with magnetite II.

[0019] Furthermore, step S4 includes the following steps: Step S41: Dry magnetite III in a vacuum drying oven at 60℃~80℃ for 6h~10h to obtain dry-basis magnetite III (moisture content <0.1%). Step S42: Crush dry-based magnetite III to a particle size of -30μm; Step S43: Perform microstructural analysis on dry-based magnetite III to determine whether its degree of liberation is greater than 75%. If not, break magnetite III again until the degree of liberation of the magnetite is greater than 75%. Step S44: Wet magnetic separation is carried out in a Davis tube with a magnetic induction intensity of 130-170 mT, and the obtained powdered magnetic fraction is magnetite IV. Step S45: After drying in a vacuum drying oven at 60℃~80℃ for 6h~10h, dry-basis magnetite IV (moisture content <0.1%) is obtained. As a preferred embodiment of the present invention, by setting a specific crushing particle size of -30μm and a magnetic induction intensity of 130~170mT in step S4, and by adaptively adjusting the crushing and magnetic separation parameters based on the analysis results of the liberation degree of magnetite III in step S42, the residual intergrowths in magnetite III can be liberated to the maximum extent, ultimately obtaining a high-grade, high-recovery magnetite IV product.

[0020] Furthermore, the microstructures of the reconstructed copper slag, magnetite I, magnetite II, and magnetite III were analyzed using an optical microscope or a scanning electron microscope. As a preferred embodiment of this invention, microstructural analysis using an optical microscope or a scanning electron microscope allows for clear and accurate observation of the morphology, grain size distribution, and embedding relationship of magnetite with the magnesium silicate matrix, providing a reliable basis for determining the degree of liberation.

[0021] Furthermore, the drying method is drying in a protective atmosphere, vacuum drying, or drying in a sealed oven. As a preferred embodiment of the present invention, by employing the above-mentioned drying methods, oxidation of the magnetite during the drying process can be effectively avoided, ensuring that the phase composition and magnetic properties of the magnetite remain unchanged, thereby ensuring the accuracy and stability of subsequent magnetic separation.

[0022] Compared with existing technologies, the advantages and effects of this application are as follows: 1. Before performing magnetic separation recovery on the reconstituted copper slag, this application first analyzes the microstructure of the reconstituted copper slag using scanning electron microscopy or optical microscopy to determine the embedding characteristics of magnetite in the magnesium silicate matrix. This step can accurately determine the distribution, grain size, and embedding relationship of magnetite in the magnesium silicate matrix, thus providing a scientific basis for determining the appropriate crushing particle size and avoiding problems such as over-crushing or insufficient dissociation caused by inappropriate crushing particle size.

[0023] 2. This application uses a Vickers hardness tester, Rockwell hardness tester, or Brinell hardness tester to determine the hardness values ​​of magnetite and magnesium silicate matrix in reconstructed copper slag. Since the hardness of forsterite (Mg2SiO4) is relatively close to that of magnetite (magnetite hardness approximately 756–841 HV, forsterite matrix hardness approximately 641–715 HV), both being relatively hard minerals, hardness testing can accurately assess the difficulty of dissociating magnetite from the magnesium silicate matrix, thereby determining the appropriate crushing method and crushing force, effectively improving dissociation efficiency.

[0024] 3. This application adopts a four-stage crushing-magnetic separation process, which gradually reduces the crushing particle size and the magnetic induction intensity, which helps to reduce the total amount of material in each stage of magnetic separation. Furthermore, through staged liberation and magnetic separation, the degree of liberation of high-hardness minerals magnetite and magnesium silicate in the reconstituted copper slag is effectively improved. The total iron grade of magnetite gradually increases from about 40% to 45% in the first stage of magnetic separation to about 58% to 62% in the fourth stage of magnetic separation, thus effectively improving the iron component recovery index in copper slag.

[0025] 4. This application specifically focuses on the systematic study of the dissociation and separation of forsterite (Mg2SiO4), a hard silicate with a hardness close to that of magnetite, from magnetite. It has formed a separation process technology package specifically for the dissociation and separation of magnetite and forsterite in reconstructed copper slag, laying a technical foundation for the dissociation and separation of magnetite from hard forsterite in reconstructed copper slag.

[0026] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the preferred embodiments of this application are described in detail below with reference to the accompanying drawings.

[0027] The above and other objects, advantages and features of this application will become more apparent to those skilled in the art from the following detailed description of specific embodiments in conjunction with the accompanying drawings. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application 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 some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In all drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0029] in: Figure 1 A flowchart of a method for recovering magnetite from reconstituted copper slag; Figure 2 To reconstruct the XRD pattern of copper slag; Figure 3 SEM images of reconstructed copper slag obtained after modification and oxidation with 5% MgO; Figure 4 Hardness diagram of magnetite and magnesium silicate matrix in reconstructed copper slag after modification with 5% MgO and oxidation. Figure 4 (a) Hardness diagram of magnetite in reconstructed copper slag after modification and oxidation with 5% MgO; Figure 4 (b) Hardness diagram of the magnesium silicate matrix in the reconstructed copper slag after modification and oxidation with 5% MgO; Figure 5 XRD patterns of magnetite and magnesium silicate matrix in reconstructed copper slag were obtained by adding 5% MgO to modify and oxidize the copper slag. Figure 5 (a) XRD pattern of magnetite in reconstructed copper slag after modification and oxidation with 5% MgO; Figure 5 (b) XRD pattern of magnesium silicate matrix in reconstructed copper slag after modification and oxidation with 5% MgO; Figure 6 SEM images of reconstructed copper slag obtained by adding 10% MgO for modification and oxidation; Figure 7 Hardness diagram of magnetite and magnesium silicate matrix in reconstructed copper slag after modification and oxidation with 10% MgO; Figure 7(a) Hardness diagram of magnetite in reconstructed copper slag after modification and oxidation with 10% MgO; Figure 7 (b) Hardness diagram of the magnesium silicate matrix in the reconstructed copper slag after modification and oxidation with 10% MgO; Figure 8 SEM images of reconstructed copper slag obtained by adding 15% MgO for modification and oxidation; Figure 9 Hardness diagram of magnetite and magnesium silicate matrix in reconstructed copper slag after modification and oxidation with 15% MgO; Figure 9 (a) Hardness diagram of magnetite in reconstructed copper slag after modification and oxidation with 15% MgO; Figure 9 (b) Hardness diagram of the magnesium silicate matrix in the reconstructed copper slag after modification and oxidation with 15% MgO. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. In the following description, specific details such as specific configurations and components are provided merely to help fully understand the embodiments of this application. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. In addition, for clarity and brevity, descriptions of known functions and structures are omitted in the embodiments.

[0031] It should be understood that the phrase "an embodiment" or "this embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "an embodiment" or "this embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0032] Furthermore, reference numerals and / or letters may be repeated in different examples within this application. Such repetition is for the purpose of simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or settings discussed.

[0033] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. The term " / and" describes another type of relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the related objects before and after it have an "or" relationship.

[0034] In this article, the term "at least one" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, "at least one of A and B" can mean: A exists alone, A and B exist simultaneously, or B exists alone.

[0035] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion.

[0036] Example 1 This embodiment describes a method for recovering magnetite from reconstructed copper slag.

[0037] Please refer to Figure 1 As shown, Figure 1 This is a flowchart of a method for recovering magnetite from reconstituted copper slag.

[0038] A method for recovering magnetite from reconstituted copper slag includes the following steps: Step S1: Analyze the microstructure of the reconstructed copper slag, determine the hardness values ​​of magnetite and magnesium silicate matrix in the reconstructed copper slag, crush the reconstructed copper slag into powder, and obtain the magnetic mineral particles by magnetic separation, which is magnetite I. Step S2: Dry magnetite I, crush the dried magnetite I, analyze the microstructure of the crushed magnetite I, determine the degree of liberation of magnetite I, and then perform magnetic separation to obtain magnetite II; Step S3: Dry magnetite II, crush the dried magnetite II, analyze the microstructure of the crushed magnetite II, determine the degree of liberation of magnetite II, and then perform magnetic separation to obtain magnetite III. Step S4: Dry magnetite III, crush the dried magnetite III, analyze the microstructure of the dried magnetite III, determine the degree of liberation of magnetite III, and then perform magnetic separation to obtain magnetite IV. Step S5: After drying magnetite IV, dry-basis magnetite IV is obtained.

[0039] The hardness value mentioned in step S1 is Vickers hardness, Rockwell hardness, or Brinell hardness.

[0040] The reconstructed copper slag in step S1 contains magnetite and forsterite. The reconstructed copper slag is a cooled slag obtained by modifying and oxidizing copper slag with MgO, wherein the mass of MgO is 5-15% of the weight of the reconstructed copper slag. The chemical composition of the copper slag is shown in Table 1 below. Table 1. Chemical composition (%) of copper slag used in the examples Example 2 Based on Example 1, this example discloses the specific steps of a method for recovering magnetite from reconstructed copper slag obtained by modifying and oxidizing copper slag with 5% MgO.

[0041] A1: The microstructure of the reconstructed copper slag was analyzed by scanning electron microscopy to determine the embedding characteristics of magnetite and magnesium silicate matrix; the hardness values ​​of magnetite and magnesium silicate matrix in the reconstructed copper slag were measured by Vickers hardness tester; the reconstructed copper slag was crushed into powder with a particle size of -74μm using a sealed laboratory crusher; the powder was subjected to wet magnetic separation in a Davis tube with a magnetic induction intensity of 300mT, and the obtained powdered magnetic fraction was magnetite I.

[0042] A2: Powdered magnetite I was dried in a vacuum drying oven at 80℃ for 6 hours to obtain dry-basis magnetite I (moisture content <0.1%); dry-basis magnetite I was crushed to a particle size of -50μm in a sealed chemical crusher, and the microstructure of dry-basis magnetite I was analyzed by scanning electron microscopy to determine that the degree of liberation of magnetite I was >50%; wet magnetic separation was carried out in a Davis tube with a magnetic induction intensity of 250mT, and the magnetic part obtained was powdered magnetite II.

[0043] A3: Powdered magnetite II was dried in a vacuum drying oven to obtain dry-basis magnetite II (moisture content <0.1%); dry-basis magnetite II was crushed to a particle size of -38μm in a sealed chemical crusher, and the microstructure of dry-basis magnetite II was analyzed by scanning electron microscopy to determine that the degree of liberation of magnetite II was >65%; wet magnetic separation was performed in a Davis tube with a magnetic induction intensity of 200mT, and the magnetic part obtained was powdered magnetite III; magnetite III was dried in a vacuum drying oven to obtain dry-basis magnetite III (moisture content <0.1%).

[0044] A4: Microstructural analysis of dry-based magnetite III using scanning electron microscopy. After dry-based magnetite III was crushed to a particle size of -30μm in a sealed chemical crusher, the degree of liberation of magnetite III was determined to be >75%. Wet magnetic separation was carried out in a Davis tube with a magnetic induction intensity of 150mT, and the magnetic part obtained was powdered magnetite IV.

[0045] A5: After drying the powdered magnetite IV in a vacuum drying oven, dry-basis magnetite IV (moisture content <0.1%) is obtained.

[0046] The reconstructed copper slag described in A1 is obtained by adding 5% MgO to copper slag for modification and oxidation.

[0047] Please refer to Figure 2 The results showed that the main iron-bearing phase in the reconstructed copper slag was magnetite (Fe3O4), and the silicate was forsterite (Mg2SiO4).

[0048] Please refer to Figure 3 The results showed that Fe in the reconstructed copper slag was enriched into particles with an average diameter of 70 μm, and showed a clear complementary relationship with Si. Ca and Si were highly overlapping, but the distribution of Mg did not show a clear regularity. Combined with the phase identification results, the microstructure of the reconstructed copper slag was characterized by granular magnetite particles with a diameter of about 70 μm embedded in a magnesium silicate matrix.

[0049] Please refer to Figure 4 and 5 The results showed that the hardness of the magnetite and forsterite matrix were 841.2 and 641.1, respectively, indicating that both are relatively hard minerals. The close hardness values ​​also increased the difficulty of dissociating magnetite from the forsterite matrix.

[0050] Please refer to Table 2. The results show that as the number of crushing-magnetic separation stages increases, the total iron grade of the recovered magnetite continuously increases, and the rate of increase in total iron grade gradually decreases with the increase in the number of crushing-magnetic separation stages. After three crushing and three separation stages, the grade of magnetite III reached 58.21%, with a corresponding iron recovery rate of 82.97%; after four crushing and four separation stages, the grade of magnetite IV increased to 61.49%, with a corresponding iron recovery rate of 79.12%. After the four crushing and four separation stages, the XRD patterns of the recovered magnetite IV and silicate tailings (a mixture of silicate I, silicate II, silicate III, and silicate IV) are shown in Table 2. Figure 5 The results indicate that the main mineral in the recovered magnetite IV is magnetite, and diffraction peaks of other minerals are barely observable. However, in the silicate tailings, diffraction peaks of magnetite, pyroxene, and forsterite can be observed simultaneously, indicating that some incompletely liberated magnetite is sorted into the tailings along with pyroxene and forsterite.

[0051] Table 2. Detailed magnetic separation index of reconstructed copper slag obtained after modification and oxidation with 5% MgO (%) Example 3 Based on Example 1, this example discloses the specific steps of a method for recovering magnetite from reconstructed copper slag obtained by modifying and oxidizing copper slag with 10% MgO.

[0052] B1: The microstructure of the reconstructed copper slag was analyzed by scanning electron microscopy to determine the embedding characteristics of magnetite and magnesium silicate matrix; the hardness values ​​of magnetite and magnesium silicate matrix in the reconstructed copper slag were measured by Vickers hardness tester; the reconstructed copper slag was crushed into powder with a particle size of -74μm using a sealed laboratory crusher; the powder was subjected to wet magnetic separation in a Davis tube with a magnetic induction intensity of 300mT, and the obtained powdered magnetic fraction was magnetite I.

[0053] B2: Same as A2.

[0054] B3: Same as A3.

[0055] B4: Same as A4.

[0056] B5: Same as A5.

[0057] The reconstructed copper slag described in B1 is obtained by adding 10% MgO to copper slag for modification and oxidation.

[0058] Please refer to Figure 2 The results showed that the main iron-containing phase of the reconstructed copper slag in this embodiment was magnetite (Fe3O4), and the silicate was forsterite (Mg2SiO4).

[0059] Please refer to Figure 6 The results showed that Fe in the reconstructed copper slag was enriched into particles with an average diameter of 70 μm, and showed a clear complementary relationship with Si. Ca and Si were highly overlapping, but the distribution of Mg did not show a clear regularity. Combined with the phase identification results, the microstructure of the reconstructed copper slag was characterized by granular magnetite particles with a diameter of about 70 μm embedded in a forsterite matrix.

[0060] Please refer to Figure 7 The results showed that the hardness of the magnetite and forsterite matrix were 756.4 and 714.8, respectively, indicating that they are hard minerals with similar hardness, and it is difficult to separate magnetite from the forsterite matrix.

[0061] Please refer to Table 3. The results show that the total iron grade of the recovered magnetite increases continuously with the increase of the number of crushing-magnetic separation stages, but the rate of increase in total iron grade gradually decreases with the increase of the number of crushing-magnetic separation stages. After four crushing and four separation stages, the grade of powdered magnetite IV increased to 59.65%, and the corresponding iron recovery rate was 82.36%.

[0062] Table 3. Detailed magnetic separation index of reconstructed copper slag obtained after modification and oxidation with 10% MgO (%) Example 4 Based on Example 1, this example discloses the specific steps of a method for recovering magnetite from reconstructed copper slag obtained by modifying and oxidizing copper slag with 15% MgO.

[0063] C1: The microstructure of the reconstructed copper slag was analyzed by scanning electron microscopy to determine the embedding characteristics of magnetite and magnesium silicate matrix; the hardness values ​​of magnetite and magnesium silicate matrix in the reconstructed copper slag were measured by Vickers hardness tester; the reconstructed copper slag was crushed into powder with a particle size of -74μm using a sealed laboratory crusher; the powder was subjected to wet magnetic separation in a Davis tube with a magnetic induction intensity of 300mT, and the obtained powdered magnetic fraction was magnetite I.

[0064] C2: Same as A2.

[0065] C3: Same as A3.

[0066] C4: Same as A4.

[0067] C5: Same as A5.

[0068] The reconstructed copper slag described in C1 is obtained by adding 15% MgO to copper slag for modification and oxidation.

[0069] Please refer to Figure 2 , Figure 2 The XRD pattern of the reconstructed copper slag showed that the main iron-bearing phase in the reconstructed copper slag of this embodiment was magnetite (Fe3O4), while the silicates were mainly composed of forsterite (Mg2SiO4) and common pyroxene (Ca(Mg,Fe)Si2O6).

[0070] Please refer to Figure 8 The results showed that Fe in the reconstructed copper slag was enriched into particles with an average diameter of 40 μm, and showed a clear complementary relationship with Si. Ca and Si were highly overlapping, but the distribution of Mg did not show a clear regularity. This indicates that the microstructure of the reconstructed copper slag is characterized by granular magnetite particles with a diameter of approximately 40 μm embedded in a magnesium silicate matrix.

[0071] Please refer to Figure 9The results showed that the hardness of the magnetite and forsterite matrices were 792.4 and 706.8, respectively, indicating that both magnetite and magnesium silicate matrices are relatively hard minerals. The close hardness values ​​also increased the difficulty of separating magnetite from the magnesium silicate matrix.

[0072] Please refer to Table 4. The results show that after four crushing and four beneficiation processes, the grade of powdered magnetite IV increased to 58.48%, with a corresponding iron recovery rate of 77.36%.

[0073] Table 4. Detailed magnetic separation index of reconstructed copper slag obtained after modification and oxidation of copper slag with 15% MgO (%) The above description is merely a preferred embodiment of the present invention and does not limit the scope of protection of the present invention. Various modifications and variations are possible with respect to the present invention. Any changes, modifications, substitutions, integrations, and parameter alterations to these embodiments within the spirit and principles of the present invention fall within the scope of protection of the claims of the present invention.

Claims

1. A method for recovering magnetite from reconstituted copper slag, characterized in that, Includes the following steps: Step S1: Analyze the microstructure of the reconstructed copper slag, crush the reconstructed copper slag into powder, and obtain magnetite I by magnetic separation; Step S2: Dry magnetite I, crush the dried magnetite I, analyze the microstructure of the crushed magnetite I, determine the degree of liberation of magnetite I, and then perform magnetic separation to obtain magnetite II; Step S3: Dry magnetite II, crush the dried magnetite II, analyze the microstructure of the crushed magnetite II, determine the degree of liberation of magnetite II, and then perform magnetic separation to obtain magnetite III. Step S4: Dry magnetite III, crush the dried magnetite III, analyze the microstructure of the dried magnetite III, determine the degree of liberation of magnetite III, and then perform magnetic separation to obtain magnetite IV.

2. The method for recovering magnetite from reconstructed copper slag according to claim 1, characterized in that, The mineral phases of the reconstructed copper slag in step S1 include magnetite and forsterite. The reconstructed copper slag is a cooled slag obtained by modifying and oxidizing copper slag with MgO. The mass of MgO is 5 to 15% of the weight of the reconstructed copper slag.

3. The method for recovering magnetite from reconstructed copper slag according to claim 1, characterized in that, It also includes step S5: drying magnetite IV to obtain dry-based magnetite IV.

4. The method for recovering magnetite from reconstituted copper slag according to claim 2, characterized in that, Step S1 includes the following steps: Step S11: Analyze the microstructure of the reconstructed copper slag to determine the intercalation characteristics of magnetite and magnesium silicate matrix; Step S12: Perform hardness testing on the reconstructed copper slag to determine the hardness values ​​of the magnetite and magnesium silicate matrix; Step S13: Crush the reconstructed copper slag into powdery slag with a particle size of -74μm; Step S14: The powdered slag is subjected to wet magnetic separation in a Davis tube with a magnetic induction intensity of 280-320mT. The magnetic part obtained is magnetite I.

5. The method for recovering magnetite from reconstructed copper slag according to claim 2, characterized in that, Step S2 includes the following steps: Step S21: Dry magnetite I to obtain dry-basis magnetite I; Step S22: Crush dry-based magnetite I to a particle size of -50μm; Step S23: Perform microstructure analysis on the crushed dry-basis magnetite I to determine whether its degree of liberation meets the requirements. If it does not meet the requirements, crush magnetite I again until the degree of liberation of the magnetite reaches the expected value. Step S24: Wet magnetic separation is carried out in a Davis tube with a magnetic induction intensity of 230-270 mT, and the magnetic part obtained is magnetite II.

6. The method for recovering magnetite from reconstructed copper slag according to claim 2, characterized in that, Step S3 includes the following steps: Step S31: Dry magnetite II is obtained by drying magnetite II; Step S32: Crush dry-based magnetite II to a particle size of -38μm; Step S33: Perform microstructure analysis on dry-based magnetite II to determine whether its degree of liberation meets the requirements. If it does not meet the requirements, crush magnetite II again until the degree of liberation of the magnetite reaches the expected value. Step S34: Wet magnetic separation is carried out in a Davis tube with a magnetic induction intensity of 180-220 mT, and the magnetic part obtained is magnetite III.

7. The method for recovering magnetite from reconstructed copper slag according to claim 2, characterized in that, Step S4 includes the following steps: Step S41: Dry magnetite III to obtain dry-basis magnetite III; Step S42: Crush dry-based magnetite III to a particle size of -30μm; Step S43: Perform microstructure analysis on dry-based magnetite III to determine whether its degree of liberation meets the requirements. If it does not meet the requirements, break magnetite III again until the degree of liberation of magnetite reaches the expected value. Step S44: Wet magnetic separation is carried out in a Davis tube with a magnetic induction intensity of 130-170 mT, and the magnetic part obtained is magnetite IV.

8. The method for recovering magnetite from reconstituted copper slag according to any one of claims 4 to 7, characterized in that, The microstructures of reconstructed copper slag, magnetite I, magnetite II, and magnetite III were analyzed using optical microscopy or scanning electron microscopy.

9. The method for recovering magnetite from reconstituted copper slag according to claim 8, characterized in that, The drying method is drying in a protective atmosphere, vacuum drying, or drying in a sealed oven.

10. The method for recovering magnetite from reconstructed copper slag according to claim 1, characterized in that, The hardness value mentioned in step S1 is Vickers hardness, Rockwell hardness, or Brinell hardness.

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