A method for treating iron-aluminum slag

Abstract

This article relates to a method for treating iron-aluminum slag, belonging to the field of waste residue treatment technology. This method utilizes at least one of water-soluble silicon and water-soluble phosphorus to treat the iron-aluminum slag, and controls the pH value to be adjusted within a specific range by adding alkali twice, thereby reducing the extractable content of Ni, Co, and Mn in the iron-aluminum slag and minimizing environmental pollution caused by heavy metal leaching.

Description

Technical Field

[0001] This article relates to the field of waste residue treatment technology, and in particular to a method for treating iron and aluminum slag. Background Technology

[0002] Iron-aluminum slag is a waste residue generated during the impurity removal process in the battery recycling industry. Its main components are Fe, Al, S, and Na, with small amounts of Ni, Co, and Mn. Because the metallic compounds in iron-aluminum slag mainly exist in the form of highly soluble sulfates, heavy metal leakage during storage can easily pollute the environment. To avoid heavy metal leakage, NaOH or Na₂CO₃ is currently commonly used to stabilize Ni, Co, and Mn before storage, but the problem of poor heavy metal stability persists. Especially for Co, even with only alkaline stabilization, the proportion of acid-extractable cobalt (determined by the BCR continuous extraction method) remains above 80%.

[0003] Iron-aluminum slag is a waste residue produced in large quantities during the battery recycling process. Due to its complex composition, it is difficult to utilize its high added value and its market absorption is limited. Therefore, it is necessary to explore methods for stabilizing heavy metals in iron-aluminum slag to reduce environmental pollution caused by iron-aluminum slag during storage. Summary of the Invention

[0004] The purpose of this paper is to overcome the shortcomings of the existing technology and provide a method for treating iron-aluminum slag, so as to reduce the extractable content of Ni, Co and Mn in iron-aluminum slag and reduce the environmental pollution caused by heavy metal leaching from iron-aluminum slag.

[0005] To achieve the above objectives, this paper provides a method for treating iron-aluminum slag, comprising the following steps:

[0006] The iron-aluminum slag to be treated is mixed and dispersed with at least one of water-soluble silicon and water-soluble phosphorus, as well as water, to obtain a solid-liquid mixture;

[0007] After adjusting the pH value to 4-5 by adding alkali to the solid-liquid mixture, the mixture is aged for the first time. Then, after adjusting the pH value to above 7 by adding alkali, the mixture is aged for the second time. The solid and liquid are separated, and the resulting solid is the target iron-aluminum slag.

[0008] Wherein, the time of the first aging and the time of the second aging are each independently ≥0;

[0009] The water-soluble phosphorus can ionize into at least one of phosphate, phosphite and hypophosphite in acidic and / or neutral aqueous solutions.

[0010] The water-soluble silicon can ionize into silicate ions in acidic and / or neutral aqueous solutions and / or alkaline aqueous solutions with a pH < 11.

[0011] The above treatment method utilizes at least one of water-soluble silicon and water-soluble phosphorus to treat iron-aluminum slag. The silicon in the water-soluble silicon, after pH adjustment with alkali and aging treatment, forms a network gel that encapsulates elements such as Ni, Co, and Mn in the iron-aluminum slag within this gel structure. Furthermore, water-soluble silicon can react with Mn in the iron-aluminum slag to form MnSiO3, which has poor water solubility, thereby reducing the extractable content of Ni, Co, and Mn in the iron-aluminum slag. Water-soluble phosphorus can react with Ni, Co, and Fe in the iron-aluminum slag to form CoNiFePO4, which has very poor water solubility, improving the stabilization effect of Ni, Co, and Mn in the iron-aluminum slag and reducing the extractable content of Ni, Co, and Mn in the iron-aluminum slag.

[0012] When water-soluble phosphorus is not used and only water-soluble silicon is used to treat iron-aluminum slag, the resulting target iron-aluminum slag has a lower extractable content of Ni, Co, and Mn, and no additional phosphorus is introduced, making it more suitable for application in the building materials industry and conducive to the resource utilization of waste residue. When only water-soluble phosphorus is used to treat iron-aluminum slag without the use of water-soluble silicon, the extractable content of Co and Ni, especially Ni with stricter content requirements, is even lower, which is more conducive to stockpiling. When both water-soluble phosphorus and water-soluble silicon are used to treat iron-aluminum slag, the extractable content of Ni, Co, and Mn in the resulting target iron-aluminum slag is even lower, which can better reduce the pollution caused by heavy metal leaching to the environment during stockpiling, thus making it more conducive to the stockpiling of iron-aluminum slag.

[0013] In the above treatment method, the purpose of the first pH adjustment is to enable aluminum (and silicon, if present, in water-soluble silicon) in the iron-aluminum slag to form macromolecular gel precursors; the purpose of the first aging is to enable aluminum (and silicon, if present, to form a network gel structure); the purpose of the second pH adjustment is to form poorly water-soluble metal hydroxides (using water-soluble silicon also forms poorly water-soluble MnSiO3, and using water-soluble phosphorus also forms poorly water-soluble CoNiFePO4); the purpose of the second aging is to make the structure of the above-mentioned poorly water-soluble substances more stable and the crystal form more complete. By controlling the target pH values ​​of the two pH adjustments within the above-mentioned specific range, the extractable content of Ni, Co, and Mn in the iron-aluminum slag can be effectively reduced.

[0014] In some embodiments, the method for treating the iron-aluminum slag satisfies: x = a·m + b·n, where,

[0015] x mol is the molar amount of silicate ions in the water-soluble silicon;

[0016] m mol is the molar amount of Mn element in the iron-aluminum slag;

[0017] n mol is the sum of the molar amounts of Co and Ni elements in the iron-aluminum slag;

[0018] a = 4 - 7;

[0019] b = 2-5. When the amount of water-soluble silicon used satisfies the above relationship, it can better reduce the extractable content of Ni, Co and Mn in iron-aluminum slag.

[0020] In some embodiments, the method for treating the iron-aluminum slag satisfies: y = c·n, where,

[0021] y mol is the sum of the molar amounts of phosphate, phosphite and hypophosphite in the water-soluble phosphorus;

[0022] n mol is the sum of the molar amounts of Co and Ni elements in the iron-aluminum slag;

[0023] c = 1.5-3. When the amount of water-soluble phosphorus used satisfies the above relationship, it can better reduce the extractable content of Ni, Co and Mn in iron-aluminum slag.

[0024] In some embodiments, during the preparation of the solid-liquid mixture, the iron-aluminum slag to be treated is mixed and dispersed with water-soluble silicon and water-soluble phosphorus. Simultaneously treating the iron-aluminum slag with water-soluble silicon and water-soluble phosphorus can better reduce the extractable content of Ni, Co, and Mn in the iron-aluminum slag.

[0025] In some embodiments, the water-soluble silicon includes at least one of silicic acid, sodium silicate, potassium silicate, water glass, and silicon-containing wastewater. Among these, the use of sodium silicate and / or water glass is not only effective in reducing the extractable content of Ni, Co, and Mn in iron-aluminum slag, but also has a wider range of sources and lower costs.

[0026] In some embodiments, the water-soluble phosphorus includes at least one of sodium phosphate, potassium phosphate, ammonium phosphate, phosphoric acid, sodium phosphite, calcium phosphate, and phosphorus-containing wastewater. The use of sodium phosphate and / or phosphorus-containing wastewater not only effectively reduces the extractable content of Ni, Co, and Mn in iron-aluminum slag but also at a lower cost.

[0027] In some embodiments, the first aging period is 0-5 hours, and the second aging period is 0-4 hours. In one embodiment, the first aging period is 3-5 hours, and the second aging period is 2-4 hours.

[0028] When the first aging time is 0-5 hours and the second aging time is 0-4 hours, especially when the first aging time is 3-5 hours and the second aging time is 2-4 hours, the stabilization effect of Ni, Co and Mn in the iron-aluminum slag is better, that is, the extractable content of Ni, Co and Mn in the target iron-aluminum slag is lower.

[0029] In some embodiments, the steps of adjusting the pH value to 4-5 by adding alkali to the solid-liquid mixture for the first aging, and then adjusting the pH value to 7 or above by adding alkali for the second aging are carried out at 15-80°C. In one embodiment, the steps of adjusting the pH value to 4-5 by adding alkali to the solid-liquid mixture for the first aging, and then adjusting the pH value to 7 or above by adding alkali for the second aging are carried out at 15-30°C.

[0030] The first aging process involves adding alkali to the solid-liquid mixture to adjust the pH to 4-5, followed by a second aging process involving adding alkali to adjust the pH to above 7. This process is carried out at 15-80°C, with particularly good results at 15-30°C. This results in better stabilization of Ni, Co, and Mn in the iron-aluminum slag, meaning that the extractable content of Ni, Co, and Mn in the target iron-aluminum slag is lower.

[0031] In some embodiments, when adjusting the pH value to above 7 with alkali and then carrying out the second aging process, the pH value is adjusted to 7-9 with alkali. This results in better stabilization of Ni, Co, and Mn in the iron-aluminum slag and reduces the amount of raw materials used.

[0032] In some embodiments, the solid content in the solid-liquid mixture is 30 wt.% to 80 wt.%.

[0033] In some embodiments, the iron-aluminum slag is the waste residue generated during the recycling of nickel-cobalt-manganese ternary battery cathode materials after removing iron and aluminum.

[0034] In some embodiments, the iron-aluminum slag comprises the following elements by mass fraction: Fe 14%-20%, Al 5%-9%, S 10%-15%, Na 4%-8%, Ni 0.8%-1.2%, Co 0.3%-0.6%, Mn 0.4%-0.6%, wherein,

[0035] Fe exists in the forms of ferric sulfate and / or ferric hydroxide;

[0036] Al exists in forms including aluminum sulfate and / or aluminum hydroxide;

[0037] Ni exists in the form of sulfates and / or hydroxides;

[0038] Co exists in the form of sulfates and / or hydroxides;

[0039] Mn exists in the form of sulfates and / or hydroxides.

[0040] Compared with existing technologies, the advantages of this paper are as follows: This paper uses at least one of water-soluble silicon and water-soluble phosphorus to treat iron-aluminum slag, and controls the pH value to be adjusted within a specific range by adding alkali twice, so as to reduce the extractable content of Ni, Co and Mn in iron-aluminum slag, reduce the environmental pollution caused by heavy metal leaching in iron-aluminum slag, and make it suitable for the building materials industry or for stockpiling. Attached Figure Description

[0041] Figure 1 This is a process flow diagram of the iron-aluminum slag treatment method in Example 1. Detailed Implementation

[0042] To better illustrate the purpose, technical solutions, and advantages of this paper, the following will provide further explanation in conjunction with specific embodiments.

[0043] Unless otherwise specified, all materials used in the examples and comparative examples are commercially available. The iron-aluminum slag used in the following examples and comparative examples is waste residue generated during the recycling of the same batch of nickel-cobalt-manganese ternary battery cathode materials, containing the following elements by mass fraction: Fe 18%, Al 8%, S 13%, Na 6%, Ni 1%, Co 0.5%, Mn 0.5%.

[0044] Fe exists in the forms of ferric sulfate and ferric hydroxide;

[0045] Al exists in the forms of aluminum sulfate and aluminum hydroxide;

[0046] Ni exists in the forms of sulfates and hydroxides;

[0047] Co exists in the forms of sulfates and hydroxides;

[0048] Mn exists in the forms of sulfates and hydroxides. The content of each element was determined using inductively coupled plasma (ICP-AES).

[0049] The acid-extractable and residual contents of Ni, Co, and Mn in the target iron-aluminum slag obtained in the examples and comparative examples were determined by the BCR continuous extraction method. The test steps are as follows:

[0050] Step 1: Testing of the acid-extractable state

[0051] Weigh 1.000 g of sample into a 50 mL polypropylene centrifuge tube, add 40 mL of 0.11 mol / L acetic acid extraction solution, shake at room temperature for 16 h, and then centrifuge (5000 r / min, 10 min). Pour the supernatant into a polyethylene bottle (take 10 mL of extraction solution and 10 mL of HNO3 into a beaker, cover, place on a hot plate for digestion and make up to volume, then determine the Ni, Co, and Mn contents, the same below). Add 20 mL of deionized water to wash the residue, shake for 20 min, centrifuge, and discard the washing solution.

[0052] Step 2: Test of the reversible state

[0053] Add 40 mL of 0.5 mol / L hydroxylamine hydrochloride extraction solution to the residue from step one, shake at room temperature for 16 h, and then centrifuge. Repeat the remaining steps as in step one.

[0054] Step 3: Testing for Oxidizable States

[0055] Add 10 mL of H2O2 to the residue from step two, cap the centrifuge tube, and digest at room temperature for 1 hour. Then remove the cap and digest in an 85°C water bath for 1 hour. Heat until the solution is nearly dry, then add another 10 mL of H2O2 and heat until the solution is nearly dry. After cooling, add 50 mL of 1 mol / L ammonium acetate extract, and shake at room temperature for 16 hours. The remaining steps are the same as in step one.

[0056] Step 4: Testing of the residual state

[0057] Weigh 0.1000g of the residue after the third extraction step and transfer it to a 50mL polytetrafluoroethylene beaker. Then add 10mL HNO3, 1mL HF and 1mL HClO4. After covering, digest the residue on a hot plate until it is clear and transparent. Then determine the contents of Ni, Co and Mn.

[0058] The concentrations of HNO3 used above are 65-68 wt.%, H2O2 is 30 wt.%, HF is 40 wt.%, and HClO4 is 70-72 wt.%.

[0059] Example 1

[0060] This embodiment provides a method for treating iron-aluminum slag, which includes the following steps:

[0061] according to Figure 1 The process flow shown involves mixing 100g of iron-aluminum slag to be treated with 8.2g of sodium phosphate, 17g of sodium silicate and water for 1 hour to obtain a solid-liquid mixture with a solid content of 50wt.%.

[0062] The temperature of the obtained solid-liquid mixture was controlled at 25℃. Under the condition of 25℃, NaOH was first added to the solid-liquid mixture to adjust the pH value to 4 (i.e., the first pH adjustment) and then aged for 5 hours (i.e., the first aging). Then NaOH was added to adjust the pH value to 8 (i.e., the second pH adjustment) and then aged for 4 hours (i.e., the second aging). The solid and liquid were separated to obtain the target iron-aluminum slag.

[0063] Example 2

[0064] This embodiment provides a method for treating iron-aluminum slag, which differs from Embodiment 1 in that the method for preparing the solid-liquid mixture is different. The method for preparing the solid-liquid mixture in this embodiment is as follows:

[0065] 100g of iron-aluminum slag to be treated was mixed with 10g of sodium phosphate, 25g of sodium silicate and water and stirred for 1 hour to obtain a solid-liquid mixture with a solid content of 30wt.%.

[0066] Example 3

[0067] This embodiment provides a method for treating iron-aluminum slag, which differs from Embodiment 1 in that the method for preparing the solid-liquid mixture is different. The method for preparing the solid-liquid mixture in this embodiment is as follows:

[0068] 100g of iron-aluminum slag to be treated was mixed with wastewater containing 0.1mol phosphate and 0.14mol silicate and stirred for 1 hour to obtain a solid-liquid mixture with a solid content of 40wt.%.

[0069] Example 4

[0070] This embodiment provides a method for treating iron-aluminum slag, which differs from Embodiment 1 in that the amount of sodium silicate used in this embodiment is 10.6g.

[0071] Example 5

[0072] This embodiment provides a method for treating iron-aluminum slag, which differs from Embodiment 1 in that the amount of sodium silicate used in this embodiment is 23.8g.

[0073] Example 6

[0074] This embodiment provides a method for treating iron-aluminum slag, which differs from Embodiment 1 in that the amount of sodium silicate used in this embodiment is 0g.

[0075] Example 7

[0076] This embodiment provides a method for treating iron-aluminum slag, which differs from Embodiment 1 in that the amount of sodium phosphate used in this embodiment is 6.2g.

[0077] Example 8

[0078] This embodiment provides a method for treating iron-aluminum slag, which differs from Embodiment 1 in that the amount of sodium phosphate used in this embodiment is 12.5g.

[0079] Example 9

[0080] This embodiment provides a method for treating iron-aluminum slag, which differs from Embodiment 1 in that the amount of sodium phosphate used in this embodiment is 0g.

[0081] Example 10

[0082] This embodiment provides a method for treating iron-aluminum slag, which differs from Embodiment 1 in that the target pH value for the first pH adjustment in this embodiment is 5.

[0083] Example 11

[0084] This embodiment provides a method for treating iron-aluminum slag, which differs from Embodiment 1 in that the target pH value for the second pH adjustment in this embodiment is 7.

[0085] Example 12

[0086] This embodiment provides a method for treating iron-aluminum slag, which differs from Embodiment 1 in that the target pH value for the second pH adjustment in this embodiment is 9.

[0087] Example 13

[0088] This embodiment provides a method for treating iron-aluminum slag, which differs from Embodiment 1 in that the target pH value for the second pH adjustment in this embodiment is 10.

[0089] Example 14

[0090] This embodiment provides a method for treating iron-aluminum slag, which differs from Embodiment 1 in that the first aging time in this embodiment is 3 hours and the second aging time is 2 hours.

[0091] Example 15

[0092] This embodiment provides a method for treating iron-aluminum slag, which differs from Embodiment 1 in that the first aging time in this embodiment is 0 hours and the second aging time is 4 hours.

[0093] Example 16

[0094] This embodiment provides a method for treating iron-aluminum slag, which differs from Embodiment 1 in that the first aging time in this embodiment is 5 hours and the second aging time is 0 hours.

[0095] Example 17

[0096] This embodiment provides a method for treating iron-aluminum slag, which includes the following steps:

[0097] 100g of iron-aluminum slag to be treated was mixed with 8.2g of sodium phosphate, 17g of sodium silicate and water and stirred for 1 hour to obtain a solid-liquid mixture with a solid content of 50wt.%.

[0098] The temperature of the obtained solid-liquid mixture was controlled at 15℃. Under the condition of 15℃, NaOH was first added to the obtained solid-liquid mixture to adjust the pH value to 4 and then aged for 5 hours. Then NaOH was added to adjust the pH value to 8 and aged for 4 hours. The solid and liquid were separated to obtain the target iron-aluminum slag.

[0099] Example 18

[0100] This embodiment provides a method for treating iron-aluminum slag, which includes the following steps:

[0101] 100g of iron-aluminum slag to be treated was mixed with 8.2g of sodium phosphate, 17g of sodium silicate and water and stirred for 1 hour to obtain a solid-liquid mixture with a solid content of 50wt.%.

[0102] The resulting solid-liquid mixture was heated to 60°C. Then, at 60°C, NaOH was first added to the solid-liquid mixture to adjust the pH value to 4 and the mixture was aged for 5 hours. Then, NaOH was added again to adjust the pH value to 8 and the mixture was aged for 4 hours. The solid and liquid were separated to obtain the target iron-aluminum slag.

[0103] Example 19

[0104] This embodiment provides a method for treating iron-aluminum slag, which includes the following steps:

[0105] 100g of iron-aluminum slag to be treated was mixed with 8.2g of sodium phosphate, 17g of sodium silicate and water and stirred for 1 hour to obtain a solid-liquid mixture with a solid content of 50wt.%.

[0106] The resulting solid-liquid mixture was heated to 80°C, and then NaOH was added at 80°C to adjust the pH value to 4 and aged for 5 hours. Then NaOH was added again to adjust the pH value to 8 and aged for 4 hours. The solid and liquid were separated to obtain the target iron-aluminum slag.

[0107] Example 20

[0108] This embodiment provides a method for treating iron-aluminum slag, which includes the following steps:

[0109] 100g of iron-aluminum slag to be treated was mixed with 4.9g of phosphoric acid, 13.44g of silicic acid and water and stirred for 1 hour to obtain a solid-liquid mixture with a solid content of 80wt.%.

[0110] The resulting solid-liquid mixture was heated to 80°C, and then NaOH was added at 80°C to adjust the pH value to 4 and aged for 5 hours. Then NaOH was added again to adjust the pH value to 8 and aged for 4 hours. The solid and liquid were separated to obtain the target iron-aluminum slag.

[0111] Example 21

[0112] This embodiment provides a method for treating iron-aluminum slag, which includes the following steps:

[0113] 100g of iron-aluminum slag to be treated was mixed with 6.3g of sodium phosphite, 17g of sodium silicate and water and stirred for 1 hour to obtain a solid-liquid mixture with a solid content of 30wt.%.

[0114] The resulting solid-liquid mixture was heated to 80°C, and then NaOH was added at 80°C to adjust the pH value to 4 and aged for 5 hours. Then NaOH was added again to adjust the pH value to 8 and aged for 4 hours. The solid and liquid were separated to obtain the target iron-aluminum slag.

[0115] Comparative Example 1

[0116] This comparative example provides a method for treating iron-aluminum slag, which differs from Example 1 in that sodium silicate and sodium phosphate are not used in this comparative example.

[0117] Comparative Example 2

[0118] This comparative example provides a method for treating iron-aluminum slag, which differs from Example 1 in that the target pH value for the first pH adjustment in this comparative example is 7.

[0119] Comparative Example 3

[0120] This comparative example provides a method for treating iron-aluminum slag, which differs from Example 1 in that the target pH value for the second pH adjustment in this comparative example is 6.

[0121] The test results of the acid-extractable content of Ni, Co, and Mn and the residual content of Ni, Co, and Mn in the target iron-aluminum slag obtained from the above embodiments and comparative examples are shown in Table 1.

[0122] Table 1

[0123]

[0124]

[0125] As can be seen from the above data, the iron-aluminum slag treatment methods in the embodiments of this paper can improve the stabilization effect of Ni, Co and Mn in iron-aluminum slag, reduce the acid-extractable content of Ni, Co and Mn in iron-aluminum slag, and increase the residual content of Ni, Co and Mn, making iron-aluminum slag suitable for the building materials industry or for stockpiling. In particular, when water-soluble silicon and water-soluble phosphorus are used to treat iron-aluminum slag at the same time, the stabilization effect of Ni, Co and Mn is better. The acid-extractable content of Ni, Co and Mn in the target iron-aluminum slag is below 22%, below 35% and below 40%, respectively; the residual content of Ni, Co and Mn is above 68%, above 60% and above 55%, respectively, which is more conducive to stockpiling.

[0126] Comparative Example 1, due to the lack of water-soluble silicon and water-soluble phosphorus, resulted in poor stabilization effects of Ni, Co, and Mn, making it unsuitable for both the building materials industry and storage.

[0127] Comparative Examples 2-3 suffered from deviations in the stabilization effects of Ni, Co, and Mn due to either an excessively high pH value during the first adjustment or an excessively low pH value during the second adjustment. Furthermore, the target iron-aluminum slag contains phosphorus, making it unsuitable for the building materials industry.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this article and are not intended to limit the scope of protection of this article. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this article without departing from the essence and scope of the technical solutions of this article.

Claims

1. A method for treating iron-aluminum slag, characterized in that, Includes the following steps: The iron-aluminum slag to be treated is mixed and dispersed with at least one of water-soluble silicon and water-soluble phosphorus, as well as water, to obtain a solid-liquid mixture. The iron-aluminum slag is the waste residue generated during the recycling of nickel-cobalt-manganese ternary battery cathode materials after removing iron and aluminum. After adjusting the pH value to 4-5 by adding alkali to the solid-liquid mixture, the mixture is aged for the first time. Then, after adjusting the pH value to above 7 by adding alkali, the mixture is aged for the second time. The solid and liquid are separated, and the resulting solid is the target iron-aluminum slag. Wherein, the time of the first aging and the time of the second aging are each independently ≥0; The water-soluble phosphorus can ionize into at least one of phosphate, phosphite and hypophosphite in acidic and / or neutral aqueous solutions. The water-soluble silicon can ionize into silicate ions in acidic and / or neutral aqueous solutions and / or alkaline aqueous solutions with a pH < 11.

2. The method for treating iron-aluminum slag as described in claim 1, characterized in that, In the preparation of the solid-liquid mixture, the iron-aluminum slag to be treated is mixed and dispersed with water-soluble silicon, and the treatment method of the iron-aluminum slag satisfies: x=a m+b n, where x mol is the molar amount of silicate ions in the water-soluble silicon; m mol is the molar amount of Mn element in the iron-aluminum slag; n mol is the sum of the molar amounts of Co and Ni elements in the iron-aluminum slag; a=4-7； b=2-5。 3. The method for treating iron-aluminum slag as described in claim 1, characterized in that, In the preparation of the solid-liquid mixture, the iron-aluminum slag to be treated is mixed and dispersed with water-soluble phosphorus, and the treatment method of the iron-aluminum slag satisfies: y=c n, where y mol is the sum of the molar amounts of phosphate, phosphite and hypophosphite in the water-soluble phosphorus; n mol is the sum of the molar amounts of Co and Ni elements in the iron-aluminum slag; c=1.5-3。 4. The method for treating iron-aluminum slag as described in claim 1, characterized in that, In the process of preparing the solid-liquid mixture, the iron-aluminum slag to be treated is mixed and dispersed with water-soluble silicon and water-soluble phosphorus.

5. The method for treating iron-aluminum slag as described in claim 1, characterized in that, The water-soluble silicon includes at least one of silicic acid, sodium silicate, potassium silicate, water glass, and silicon-containing wastewater; and / or The water-soluble phosphorus includes at least one of sodium phosphate, potassium phosphate, ammonium phosphate, phosphoric acid, sodium phosphite, calcium phosphate, and phosphorus-containing wastewater.

6. The method for treating iron-aluminum slag as described in any one of claims 1-5, characterized in that, At least one of conditions (1)-(3) must be satisfied: (1) The first aging time is 0-5 hours, and the second aging time is 0-4 hours; (2) The first aging process is carried out in the solid-liquid mixture after adjusting the pH value to 4-5 by adding alkali and then adjusting the pH value to 7 or above by adding alkali for the second aging process, which is carried out at 15-80℃; (3) When the pH value is adjusted to above 7 by adding alkali and then aging for the second time, the pH value is adjusted to 7-9 by adding alkali.

7. The method for treating iron-aluminum slag as described in claim 6, characterized in that, At least one of conditions S1-S2 must be satisfied: S1. The first aging time is 3-5 hours, and the second aging time is 2-4 hours; S2. The first aging process is carried out by adding alkali to the solid-liquid mixture to adjust the pH value to 4-5, and then adding alkali to adjust the pH value to above 7 for the second aging process, which is carried out at 15-30°C.

8. The method for treating iron-aluminum slag as described in any one of claims 1-5, characterized in that, The solid content in the solid-liquid mixture is 30 wt.%-80 wt.%.

9. The method for treating iron-aluminum slag as described in any one of claims 1-5, characterized in that, The iron-aluminum slag comprises the following elements by mass fraction: Fe 14%-20%, Al 5%-9%, S 10%-15%, Na 4%-8%, Ni 0.8%-1.2%, Co 0.3%-0.6%, Mn 0.4%-0.6%, wherein, Fe exists in the forms of ferric sulfate and / or ferric hydroxide; Al exists in forms including aluminum sulfate and / or aluminum hydroxide; Ni exists in the form of sulfates and / or hydroxides; Co exists in the form of sulfates and / or hydroxides; Mn exists in the form of sulfates and / or hydroxides.

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