A method for treating iron-containing waste residue by waste and battery-grade iron phosphate

Abstract

The application discloses a kind of with waste to treat iron-containing waste slag and battery-grade iron phosphate.The method comprises the following steps: S1, iron-containing waste slag is treated by acid leaching, and solid-liquid separation is carried out after acid leaching to obtain a first filtrate;S2, reducing waste slag is added to the first filtrate, and the ferric iron in the first filtrate is reduced to ferrous iron;S3, the pH of the first filtrate is adjusted and controlled to 1.5-3, and then solid-liquid separation is carried out to obtain a second filtrate, phosphoric acid is added to the second filtrate to obtain a mixed solution;S4, an oxidizing agent is added to the mixed solution, and solid-liquid separation is carried out after reaction to obtain a solid, which is washed and dried to obtain iron phosphate.The method for treating iron-containing waste slag in the application can treat at least two types of waste slag simultaneously using the waste-to-waste technology, which not only reduces the treatment cost of waste slag, but also converts waste slag into high-value battery-grade iron phosphate product, greatly reducing the preparation cost of battery-grade iron phosphate.

Description

Technical Field

[0001] This invention relates to the field of industrial solid waste resource utilization technology, and in particular to a method for treating iron-containing waste residue using waste-to-waste technology and battery-grade iron phosphate. Background Technology

[0002] Lithium iron phosphate (LFP) batteries have seen rapid expansion in applications such as new energy vehicles due to their excellent cycle life, high safety, and cost advantages. As a key raw material for LFP production, the quality of iron phosphate directly affects its physical and chemical properties. Battery-grade LFP used in cathode material production has extremely strict limitations on impurity content, which necessitates high purity of the basic raw materials. Typically, high-purity phosphoric acid (or phosphate) is used to react with iron salts. However, these high-purity raw materials are often expensive, resulting in high production costs. Therefore, exploring the preparation of a low-cost battery-grade LFP has become an urgent problem to be solved.

[0003] In industrial production, iron-containing solid wastes such as sulfuric acid slag, copper smelting slag, ferrophosphate slag, and battery black powder are usually treated separately due to their different sources and characteristics. However, this approach is costly because: firstly, each type of waste requires specialized equipment, resulting in high initial and maintenance costs; secondly, pollutant treatment requires separate facilities, leading to significant investment in reagents and equipment; thirdly, limited processing capacity results in high unit energy consumption, requires a professional team, increases labor costs, and the complex processes are prone to inefficiency; and fourthly, it is difficult to efficiently utilize each component, leading to resource waste and hidden costs. Summary of the Invention

[0004] This invention discloses a method for treating iron-containing waste residue using waste-to-waste technology and battery-grade iron phosphate, in order to solve the above-mentioned technical problems in the prior art.

[0005] To solve the above problems, the present invention adopts the following technical solution:

[0006] In a first aspect, this application provides a method for treating iron-containing waste slag using waste-to-waste treatment, comprising the following steps:

[0007] S1. The iron-containing waste residue is acid-leached, and then solid-liquid separation is performed to obtain the first filtrate containing ferric iron.

[0008] S2. Add reducing waste residue to the first filtrate to reduce the ferric iron in the first filtrate to ferrous iron;

[0009] S3. Adjust and control the pH of the first filtrate treated in step S2 to 1.5~3, then perform solid-liquid separation to obtain the second filtrate. Add phosphoric acid to the second filtrate to obtain a mixed solution.

[0010] S4. Add an oxidant to the mixed solution, react and then separate the solid and liquid. The obtained solid is washed and dried to obtain iron phosphate.

[0011] Secondly, this application provides a battery-grade iron phosphate, which is prepared by the above-mentioned method of treating iron-containing waste residue with waste.

[0012] The technical solution adopted in this invention can achieve the following beneficial effects:

[0013] The method for treating iron-containing waste slag using a waste-to-waste approach in this application employs a technology that can simultaneously treat at least two types of waste slag. This not only reduces the treatment cost of the waste slag but also transforms it into high-value battery-grade iron phosphate, significantly lowering the production cost of battery-grade iron phosphate. Furthermore, the acid added during acid leaching can simultaneously treat both the iron-containing waste slag and the reducing waste slag, achieving not only waste-to-waste treatment but also the gradient utilization of the acid. Specifically, it has the following advantages:

[0014] (1) The method of treating iron-containing waste residue by treating waste in this application takes iron-containing waste residue as the main treatment object and reduces waste residue as a reducing agent. It adopts the treatment idea of ​​treating waste by treating waste, and uses the waste residue that originally needed to be disposed of separately as a raw material (reducing agent) in the process, which reduces the treatment cost of waste residue and reduces the environmental risks such as land occupation, heavy metal leakage, and air pollution caused by waste residue stockpiling, landfilling or incineration. At the same time, the reducing waste residue replaces the traditional chemical reducing agent (such as iron powder), which can reduce the amount of reducing agent used and reduce the treatment cost of waste residue.

[0015] (2) The method for treating iron-containing waste residue in this application involves the iron in the waste residue being converted into battery-grade iron phosphate through steps such as acid leaching, reduction, impurity removal, and oxidation. Iron phosphate is a core raw material for lithium-ion battery cathode materials, with high market demand and economic value. This method realizes the transformation from low-value waste residue to high-value products, improves the utilization efficiency of iron resources, and achieves high-value recycling of iron resources.

[0016] (3) The method for treating iron-containing waste residue using waste-to-waste approach in this application controls the pH to 1.5-3 in step S3. The pH difference in the precipitation of different metal ion hydroxides allows for selective impurity removal: ferrous iron (Fe²⁺) 2+ The hydroxide of Fe(OH)₂ begins to precipitate at approximately pH 6.4, and remains stable in solution under strongly acidic conditions at pH 1.5–3 without precipitation; while common impurity ions (such as Al) 3+ Cr 3+ Ti 4+ Pb 2+ Cu 2+The hydroxide precipitate (etc.) has a low pH, and can form a precipitate that can be removed at pH 1.5-3. This step significantly reduces the impurity content in the subsequent ferric phosphate, ensuring product purity. In step S4, the oxidant oxidizes ferrous iron to ferric iron, which reacts rapidly with phosphate ions in the solution to form a ferric phosphate precipitate with extremely low solubility. The reaction is thorough and the product is stable, further reducing the possibility of impurity co-precipitation and obtaining battery-grade ferric phosphate.

[0017] (4) The core raw materials of the method for treating iron-containing waste residue by treating waste in this application are iron-containing waste residue and reducing waste residue, both of which are wastes and have low acquisition costs, or even free; phosphoric acid can also use industrial-grade low-priced raw materials; oxidants (such as hydrogen peroxide, sodium hypochlorite, etc.) are inexpensive, and the overall raw material cost is far lower than that of processes using pure chemical reagents. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0019] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0020] This application provides a method for treating iron-containing waste slag using waste-to-waste treatment, comprising the following steps:

[0021] S1. The iron-containing waste residue is subjected to acid leaching treatment, and solid-liquid separation is performed after acid leaching to obtain the first filtrate containing ferric iron; the acid leaches the iron from the iron-containing waste residue, and the iron exists in the form of ferric iron, with trace amounts existing in the form of ferrous iron.

[0022] S2. Add reducing waste residue to the first filtrate to reduce the ferric iron in the first filtrate to ferrous iron. The reducing waste residue plays a reducing role, and its reducing property is used to reduce the ferric iron in the first filtrate to ferrous iron, laying the foundation for subsequent pH adjustment and impurity removal.

[0023] S3. Adjust and control the pH of the first filtrate treated in step S2 to 1.5-3, then perform solid-liquid separation to obtain the second filtrate. Add phosphoric acid to the second filtrate to obtain a mixed solution. When the pH of the first filtrate is 1.5-3, impurities in the first filtrate (such as Al) are reduced. 3+ Cr 3+ Ti 4+ Pb 2+ Cu 2+ (etc.) are converted into precipitates and removed, and the resulting second filtrate is a pure solution containing ferrous iron and phosphate ions; phosphoric acid is added to replenish phosphorus in the second filtrate in preparation for the subsequent formation of ferric phosphate;

[0024] S4. Add an oxidizing agent to the mixed solution. After the reaction, perform solid-liquid separation. The obtained solid is washed and dried to obtain ferric phosphate. Adding an oxidizing agent to the mixed solution oxidizes ferrous iron to ferric iron ions, which then react rapidly with phosphate ions to form ferric phosphate precipitate.

[0025] In some embodiments, in step S2, the reducing waste residue is ferrophosphate slag. Using ferrophosphate slag instead of traditional chemical reducing agents (such as iron powder) not only treats the waste residue but also allows for the high-value recovery of phosphorus and iron from the ferrophosphate slag, while simultaneously reducing the waste residue treatment cost.

[0026] In some embodiments, when the reducing waste residue in step S2 is ferrophosphate slag, the amount of ferrophosphate slag added is: based on the mass of ferric iron in the first filtrate, the mass ratio of ferric iron to ferrophosphate slag is 1:1.5~3.

[0027] In some embodiments, in step S2, when the reducing waste residue is ferrophosphate slag, the reaction temperature of the first filtrate and the ferrophosphate slag is 80~100℃, and the reaction time is 1.5~3h.

[0028] In some embodiments, in step S2, the reducing waste residue is battery black powder. When the reducing waste residue is battery black powder, sulfuric acid is added to the first filtrate when the battery black powder is added to the first filtrate.

[0029] In some embodiments, when battery black powder is used as the reducing waste residue in step S2, the first filtrate is first diluted with water 6-7.5 times to obtain a diluted solution; then, battery black powder and sulfuric acid are added to the diluted solution; wherein, the amount of battery black powder added is: based on the mass of ferric iron in the diluted solution, the mass ratio of ferric iron to battery black powder is 1:30-40; the amount of sulfuric acid added is: the mass ratio of sulfuric acid to battery black powder is 0.5-0.9:1, and the sulfuric acid concentration is 98%. Using battery black powder instead of traditional chemical reducing agents (such as iron powder) utilizes the elemental aluminum in the battery black powder to reduce ferric iron to ferrous iron; at the same time, the addition of sulfuric acid can increase the acidity of the diluted solution, dissolving the phosphorus and iron in the battery black powder. This not only treats the waste residue but also recovers the phosphorus and iron in the battery black powder at a high value, while reducing the waste residue treatment cost.

[0030] In some embodiments, when battery black powder is used as the reducing waste residue in step S2, the reaction temperature is room temperature and the reaction time is 1.5 to 3 hours.

[0031] In some embodiments, in step S3, adjusting and controlling the pH of the first filtrate to 1.5-3 is done by adding an alkaline solution.

[0032] In some embodiments, the alkaline solution includes any one of sodium hydroxide, sodium carbonate, and sodium bicarbonate.

[0033] In some embodiments, step S3, adjusting and controlling the pH of the first filtrate to 1.5-3, includes: first adding battery black powder to the first filtrate to adjust its pH to 0.3-1.3; then adding an alkaline solution to the first filtrate to control its pH to 1.5-3. The purpose of adding battery black powder is to neutralize the pH while ensuring the acidity of the first filtrate completely dissolves the lithium iron phosphate in the battery black powder. Therefore, using battery black powder to replace part of the alkaline solution can significantly reduce the amount of alkaline solution used. Furthermore, it can also treat battery black powder waste simultaneously, dissolving the phosphorus and iron in the battery black powder and converting it into high-value iron phosphate products.

[0034] In some embodiments, in step S3, the amount of phosphoric acid added is based on the total iron in the second filtrate, and the ratio of the molar amount of phosphate to the molar amount of total iron in the second filtrate after the addition of phosphoric acid is 1.05~1.15:1 (preferably 1.05:1).

[0035] In some embodiments, in step S1, the iron-containing waste residue includes at least one of sulfuric acid residue and copper smelting residue.

[0036] In some embodiments, the acid used in step S1 for acid leaching is sulfuric acid.

[0037] In some embodiments, in step S1, when the iron-containing waste residue is subjected to acid leaching treatment, the acid used is sulfuric acid with a concentration of 98%; during the acid leaching treatment, water is also added to the iron-containing waste residue, and the mass ratio of iron-containing waste residue, acid and water is 100:80~150:200~500.

[0038] In some embodiments, the acid used in step S1 for acid leaching is a mixture of sulfuric acid and phosphoric acid.

[0039] In some embodiments, in step S1, when the iron-containing waste slag is subjected to acid leaching treatment, the acid used is a mixed acid consisting of 98% sulfuric acid and 85% phosphoric acid.

[0040] In some embodiments, in step S1, when the iron-containing waste slag is acid-leached, the acid used is a mixed acid consisting of 98% sulfuric acid and 85% phosphoric acid mixed in a 1:1 mass ratio. During the acid leaching process, water is also added to the iron-containing waste slag, and the mass ratio of the iron-containing waste slag, mixed acid, and water is 100:90~300:200~500. It should be noted that the sulfuric acid used in this application is 98% concentrated sulfuric acid; it should also be noted that, in addition to 98% concentrated sulfuric acid, other concentrations of sulfuric acid (such as 50%, 70%, 80%, etc.) can also be selected according to actual reaction requirements. Similarly, the phosphoric acid used in this application is 85% phosphoric acid; it should also be noted that, in addition to 85% phosphoric acid, other concentrations of phosphoric acid (such as 50%, 75%, etc.) can also be selected according to actual reaction requirements. Furthermore, the 1:1 mass ratio of 98% sulfuric acid and 85% phosphoric acid is merely an illustrative example; other ratios can also be used for acid leaching.

[0041] In some embodiments, in step S1, the iron-containing waste residue is acid-leached at a temperature of 20~95℃ for 1~3 hours.

[0042] In some embodiments, in step S4, after adding the oxidant, the reaction is carried out at a temperature of 45~50°C for 0.5~1.5 hours.

[0043] This application provides a battery-grade iron phosphate, which is obtained by the above-mentioned waste-to-waste treatment method for iron-containing waste residue.

[0044] The following detailed embodiments illustrate a method for treating iron-containing waste slag using waste-to-waste technology and battery-grade iron phosphate provided in this application.

[0045] I. Raw Material Description (Source, Substance Content):

[0046] Sulfuric acid residue: tailings or waste residue from sulfuric acid processing in sulfuric acid plants.

[0047] Copper smelting slag: a byproduct of the smelting or blowing stage in the copper ore smelting process.

[0048] Phosphorus-iron slag: a byproduct of yellow phosphorus production, mainly composed of phosphorus and iron.

[0049] Battery black powder: It comes from battery recycling plants and its main components are lithium, phosphorus and iron.

[0050] The composition and content of sulfuric acid slag, copper smelting slag, phosphorus iron slag, and battery black powder used in the embodiments of this application are shown in Table 1 below; wherein, phosphorus and iron are expressed as mass percentages, and other components are expressed as ppm.

[0051] Table 1. Raw Material Composition Content Table

[0052]

[0053] II. Testing Standards for Ferric Phosphate

[0054] The iron phosphate obtained in the following examples was tested according to HG / T 4701-2021 Iron phosphate for batteries.

[0055] III. Examples

[0056] Example 1:

[0057] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0058] S1. Take 100g of sulfuric acid residue, 120g of 98% sulfuric acid, and 300g of water. Mix the three together evenly, heat to 95℃, and soak for 2.5h while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0059] S2. Add 60g of phosphorus iron slag to the first filtrate and mix evenly. Heat to 90℃ and react for 2 hours under stirring to reduce the trivalent iron in the first filtrate to divalent iron.

[0060] S3. Add 137.5g of 40% sodium hydroxide solution to the first filtrate treated in step S2, adjust and control the pH of the first filtrate to 2, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 64.8g of 85% phosphoric acid to the second filtrate and mix well to obtain a mixed solution.

[0061] S4. Add 33.4g of 30% hydrogen peroxide to the mixed solution and react at 45℃ for 1 hour. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0062] Testing revealed that 80.89g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 2 below.

[0063] Table 2. Impurities and content of ferric phosphate in Example 1

[0064]

[0065] Example 2:

[0066] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0067] S1. Take 100g of sulfuric acid residue, 55g of 98% sulfuric acid, 55g of 85% phosphoric acid, and 300g of water. Mix the four ingredients evenly, heat to 95℃, and soak for 2.5h while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0068] S2. Add 45g of phosphorus iron slag to the first filtrate and mix evenly. Heat to 90℃ and react for 2 hours under stirring to reduce the trivalent iron in the first filtrate to divalent iron.

[0069] S3. Add 138.3g of 40% sodium hydroxide solution to the first filtrate treated in step S2, adjust and control the pH of the first filtrate to 2, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 10g of 85% phosphoric acid to the second filtrate and mix well to obtain a mixed solution.

[0070] S4. Add 33.4g of 30% hydrogen peroxide to the mixed solution and react at 45℃ for 1 hour. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0071] Testing revealed that 80.89g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 3 below.

[0072] Table 3. Impurities and content of ferric phosphate in Example 2

[0073]

[0074] Example 3:

[0075] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0076] S1. Take 100g of copper smelting slag, 100g of 98% sulfuric acid, and 400g of water. Mix the three together evenly, heat to 95℃, and soak for 3 hours while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0077] S2. Add 50g of phosphorus iron slag to the first filtrate and mix evenly. Heat to 90℃ and react for 2 hours under stirring to reduce the trivalent iron in the first filtrate to divalent iron.

[0078] S3. Add 133.2g of 40% sodium hydroxide solution to the first filtrate treated in step S2, adjust and control the pH of the first filtrate to 2, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 56.85g of 85% phosphoric acid to the second filtrate and mix well to obtain a mixed solution.

[0079] S4. Add 29.28g of 30% hydrogen peroxide to the mixed solution and react at 45℃ for 1 hour. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0080] Testing revealed that 70.9g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 4 below.

[0081] Table 4. Impurities and content of ferric phosphate in Example 3

[0082]

[0083] Example 4:

[0084] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0085] S1. Take 100g of copper smelting slag, 45g of 98% sulfuric acid, 45g of 85% phosphoric acid, and 410g of water. Mix the four ingredients evenly, heat to 95℃, and soak for 3 hours while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0086] S2. Add 58g of phosphorus iron slag to the first filtrate and mix evenly. Heat to 90℃ and react for 2 hours under stirring to reduce the trivalent iron in the first filtrate to divalent iron.

[0087] S3. Add 134.8g of 40% sodium hydroxide solution to the first filtrate treated in step S2, adjust and control the pH of the first filtrate to 2, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 11.85g of 85% phosphoric acid to the second filtrate and mix well to obtain a mixed solution.

[0088] S4. Add 25.83g of 30% hydrogen peroxide to the mixed solution and react at 45℃ for 1 hour. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0089] Testing revealed that 62.5g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 5 below.

[0090] Table 5. Impurities and content of ferric phosphate in Example 4

[0091]

[0092] Example 5:

[0093] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0094] S1. Take 100g of sulfuric acid residue, 80g of 98% sulfuric acid, and 200g of water. Mix the three together evenly, heat to 30℃, and soak for 3.0h while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0095] S2. Add 45g of phosphorus iron slag to the first filtrate and mix evenly. Heat to 90℃ and react for 2 hours under stirring to reduce the trivalent iron in the first filtrate to divalent iron.

[0096] S3. Add 151.2g of 40% sodium hydroxide solution to the first filtrate treated in step S2, adjust and control the pH of the first filtrate to 3, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 64.8g of 85% phosphoric acid to the second filtrate and mix well to obtain a mixed solution.

[0097] S4. Add 33.4g of 30% hydrogen peroxide to the mixed solution and react at 45℃ for 1 hour. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0098] Testing revealed that 80.89g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 6 below.

[0099] Table 6. Impurities and content of ferric phosphate in Example 5

[0100]

[0101] Example 6:

[0102] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0103] S1. Take 100g of sulfuric acid residue, 150g of 98% sulfuric acid, and 500g of water. Mix the three together evenly, heat to 95℃, and soak for 2.5h while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0104] S2. Add 45g of phosphorus iron slag to the first filtrate and mix evenly. Heat to 90℃ and react for 2 hours under stirring to reduce the trivalent iron in the first filtrate to divalent iron.

[0105] S3. Add 102.7g of 40% sodium hydroxide solution to the first filtrate treated in step S2, adjust and control the pH of the first filtrate to 1.5, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 64.8g of 85% phosphoric acid to the second filtrate and mix well to obtain a mixed solution.

[0106] S4. Add 33.4g of 30% hydrogen peroxide to the mixed solution and react at 45℃ for 1 hour. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0107] Testing revealed that 80.89g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 7 below.

[0108] Table 7. Impurities and content of ferric phosphate in Example 6

[0109]

[0110] Example 7:

[0111] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0112] S1. Take 100g of sulfuric acid residue, 150g of 98% sulfuric acid, and 500g of water. Mix the three together evenly, heat to 95℃, and soak for 2.5h while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0113] S2. Add 50.7g of phosphorus iron slag to the first filtrate and mix well. Heat to 80℃ and react for 3 hours under stirring to reduce the trivalent iron in the first filtrate to divalent iron.

[0114] S3. Add 137.6g of 40% sodium hydroxide solution to the first filtrate treated in step S2, adjust and control the pH of the first filtrate to 2, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 64.42g of 85% phosphoric acid to the second filtrate and mix well to obtain a mixed solution.

[0115] S4. Add 33.17g of 30% hydrogen peroxide to the mixed solution and react at 50℃ for 0.5 hours. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0116] Testing revealed that 80.35g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 8 below.

[0117] Table 8. Impurities and content of ferric phosphate in Example 7

[0118]

[0119] Example 8:

[0120] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0121] S1. Take 100g of sulfuric acid residue, 150g of 98% sulfuric acid, and 500g of water. Mix the three together evenly, heat to 95℃, and soak for 2.5h while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0122] S2. Add 90.6g of phosphorus iron slag to the first filtrate and mix well. Heat to 100℃ and react for 1.5h under stirring to reduce the trivalent iron in the first filtrate to divalent iron.

[0123] S3. Add 138.1g of 40% sodium hydroxide solution to the first filtrate treated in step S2, adjust and control the pH of the first filtrate to 2, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 65.28g of 85% phosphoric acid to the second filtrate and mix well to obtain a mixed solution.

[0124] S4. Add 33.62g of 30% hydrogen peroxide to the mixed solution and react at 47℃ for 1 hour. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0125] Testing revealed that 81.43g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 9 below.

[0126] Table 9. Impurities and content of ferric phosphate in Example 8

[0127]

[0128] Example 9:

[0129] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0130] S1. Take 100g of sulfuric acid residue, 120g of 98% sulfuric acid, and 300g of water. Mix the three together evenly, heat to 95℃, and soak for 2.5h while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0131] S2. Add 45g of phosphorus iron slag to the first filtrate and mix evenly. Heat to 90℃ and react for 2 hours under stirring to reduce the trivalent iron in the first filtrate to divalent iron.

[0132] S3. First, add 80g of battery black powder to the first filtrate treated in step S2 and adjust the pH of the mixed solution to 1.03. Then, add 43.7g of 40% sodium hydroxide solution to the mixed solution, adjust and control the pH of the first filtrate to 2, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 72.06g of 85% phosphoric acid to the second filtrate and mix evenly to obtain the mixed solution.

[0133] S4. Add 38.96g of 30% hydrogen peroxide to the mixed solution and react at 45℃ for 1 hour. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0134] Testing revealed that 94.37g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 10 below.

[0135] Table 10. Impurities and content of ferric phosphate in Example 9

[0136]

[0137] Example 10:

[0138] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0139] S1. Take 100g of sulfuric acid residue, 120g of 98% sulfuric acid, and 300g of water. Mix the three together evenly, heat to 95℃, and soak for 2.5h while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0140] S2. Add 45g of phosphorus iron slag to the first filtrate and mix evenly. Heat to 90℃ and react for 2 hours under stirring to reduce the trivalent iron in the first filtrate to divalent iron.

[0141] S3. First, add 50g of battery black powder to the first filtrate treated in step S2 and adjust the pH of the first filtrate to 0.68; then add 81.2g of 40% sodium hydroxide solution to the first filtrate, adjust and control the pH of the first filtrate to 2, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 71.77g of 85% phosphoric acid to the second filtrate and mix evenly to obtain a mixed solution.

[0142] S4. Add 36.95g of 30% hydrogen peroxide to the mixed solution and react at 45℃ for 1 hour. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0143] Testing revealed that 89.5g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 11 below.

[0144] Table 11 Impurities and content of ferric phosphate in Example 10

[0145]

[0146] Example 11:

[0147] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0148] S1. Take 100g of sulfuric acid residue, 55g of 98% sulfuric acid, 55g of 85% phosphoric acid, and 300g of water. Mix the four ingredients evenly, heat to 95℃, and soak for 2.5h while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0149] S2. Add 45g of phosphorus iron slag to the first filtrate and mix evenly. Heat to 90℃ and react for 2 hours under stirring to reduce the trivalent iron in the first filtrate to divalent iron.

[0150] S3. First, add 80g of battery black powder to the first filtrate treated in step S2 and adjust the pH of the first filtrate to 1.05. Then, add 43.2g of 40% sodium hydroxide solution to the first filtrate, adjust and control the pH of the first filtrate to 2, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 15.04g of 85% phosphoric acid to the second filtrate and mix evenly to obtain a mixed solution.

[0151] S4. Add 38.96g of 30% hydrogen peroxide to the mixed solution and react at 45℃ for 1 hour. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0152] Testing revealed that 94.37g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 12 below.

[0153] Table 12 Impurities and content of ferric phosphate in Example 11

[0154]

[0155] Example 12:

[0156] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0157] S1. Take 100g of copper smelting slag, 100g of 98% sulfuric acid, and 400g of water. Mix the three together evenly, heat to 60℃, and soak for 3 hours while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0158] S2. Add 52.6g of phosphorus iron slag to the first filtrate and mix well. Heat to 90℃ and react for 2 hours under stirring to reduce the trivalent iron in the first filtrate to divalent iron.

[0159] S3. First, add 80g of battery black powder to the first filtrate treated in step S2 and adjust the pH of the first filtrate to 1.21. Then, add 41.3g of 40% sodium hydroxide solution to the first filtrate, adjust and control the pH of the first filtrate to 2, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 70.9g of 85% phosphoric acid to the second filtrate and mix well to obtain a mixed solution.

[0160] S4. Add 35.06g of 30% hydrogen peroxide to the mixed solution and react at 45℃ for 1 hour. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0161] Testing revealed that 84.9g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 13 below.

[0162] Table 13 Impurities and content of ferric phosphate in Example 12

[0163]

[0164] Example 13:

[0165] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0166] S1. Take 100g of sulfuric acid residue, 120g of 98% sulfuric acid, and 300g of water. Mix the three together evenly, heat to 95℃, and soak for 2.5h while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0167] S2. Take 50g of the first filtrate, dilute it with water to 345g, add 118.8g of battery black powder and 65.4g of 98% sulfuric acid, stir and react at room temperature for 2h to reduce the ferric iron in the first filtrate to ferrous iron.

[0168] S3. Add 9g of 40% sodium hydroxide solution to the first filtrate treated in step S2, adjust and control the pH of the first filtrate to 2, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 50.15g of 85% phosphoric acid to the second filtrate and mix well to obtain a mixed solution.

[0169] S4. Add 24.76g of 30% hydrogen peroxide to the mixed solution and react at 45℃ for 1 hour. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0170] Testing revealed that 59.97g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 14 below.

[0171] Table 14. Impurities and content of ferric phosphate in Example 13

[0172]

[0173] Example 14:

[0174] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0175] S1. Take 100g of sulfuric acid residue, 55g of 98% sulfuric acid, 55g of 85% phosphoric acid, and 300g of water. Mix the four ingredients evenly, heat to 95℃, and soak for 2.5h while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0176] S2. Take 50g of the first filtrate, dilute it with water to 345g, add 146.4g of battery black powder and 73.2g of 98% sulfuric acid, stir and react at room temperature for 3h to reduce the ferric iron in the first filtrate to ferrous iron.

[0177] S3. Add 8.95g of 40% sodium hydroxide solution to the first filtrate treated in step S2, adjust and control the pH of the first filtrate to 2, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 41.37g of 85% phosphoric acid to the second filtrate and mix well to obtain a mixed solution.

[0178] S4. Add 32.64g of 30% hydrogen peroxide to the mixed solution and react at 45℃ for 1 hour. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0179] Testing revealed that 79.06 g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 15 below.

[0180] Table 15 Impurities and content of ferric phosphate in Example 14

[0181]

[0182] Example 15:

[0183] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0184] S1. Take 100g of copper smelting slag, 100g of 98% sulfuric acid, and 400g of water. Mix the three together evenly, heat to 95℃, and soak for 3 hours while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0185] S2. Take 50g of the first filtrate, dilute it with water to 345g, add 100g of battery black powder and 55g of 98% sulfuric acid, stir and react at room temperature for 1.5h to reduce the ferric iron in the first filtrate to ferrous iron.

[0186] S3. Add 8.98g of 40% sodium hydroxide solution to the first filtrate treated in step S2, adjust and control the pH of the first filtrate to 2, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 50.06g of 85% phosphoric acid to the second filtrate and mix well to obtain a mixed solution.

[0187] S4. Add 23.64g of 30% hydrogen peroxide to the mixed solution and react at 45℃ for 1 hour. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0188] Testing revealed that 57.27g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 16 below.

[0189] Table 16 Impurities and content of ferric phosphate in Example 15

[0190]

[0191] Example 16:

[0192] A method for treating iron-containing waste slag using waste-to-waste technology includes the following steps:

[0193] S1. Take 100g of sulfuric acid residue, 120g of 98% sulfuric acid, and 300g of water. Mix the three together evenly, heat to 95℃, and soak for 2.5h while stirring. Then filter to obtain the first filtrate containing ferric iron.

[0194] S2. Take 50g of the first filtrate, dilute it with water to 345g, add 108g of battery black powder and 86.4g of 98% sulfuric acid, stir and react at room temperature for 2h to reduce the ferric iron in the first filtrate to ferrous iron.

[0195] S3. Add 4.3g of 40% sodium hydroxide solution to the first filtrate treated in step S2, adjust and control the pH of the first filtrate to 1.5, keep stirring at room temperature, and then filter to obtain the second filtrate. Add 50.15g of 85% phosphoric acid to the second filtrate and mix well to obtain a mixed solution.

[0196] S4. Add 24.82g of 30% hydrogen peroxide to the mixed solution and react at 45℃ for 1 hour. After the reaction, filter the solution and wash, dry and calcine the solid to obtain anhydrous ferric phosphate.

[0197] Testing revealed that 60.13g of ferric phosphate was obtained in this example, with a purity of 99.99%. Impurities in the ferric phosphate are listed in Table 17 below.

[0198] Table 17 Impurities and content of ferric phosphate in Example 16

[0199]

[0200] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for treating iron-containing waste slag using waste-to-waste technology, characterized in that, Includes the following steps: S1. The iron-containing waste residue is acid-leached, and then solid-liquid separation is performed to obtain the first filtrate containing ferric iron. S2. Add reducing waste residue to the first filtrate to reduce the ferric iron in the first filtrate to ferrous iron; the reducing waste residue is ferric phosphate slag or battery black powder. When battery black powder is used as the reducing waste residue, first dilute the first filtrate with water to 6 to 7.5 times its original mass to obtain a diluted solution; then add battery black powder and sulfuric acid to the diluted solution. S3. Adjust and control the pH of the first filtrate treated in step S2 to 1.5~3, then perform solid-liquid separation to obtain the second filtrate. Add phosphoric acid to the second filtrate to obtain a mixed solution. S4. Add an oxidant to the mixed solution, react and then separate the solid and liquid. The obtained solid is washed and dried to obtain iron phosphate.

2. The method for treating iron-containing waste slag using waste-to-waste technology according to claim 1, characterized in that, In step S2, when the reducing waste residue is ferrophosphate slag, the amount of ferrophosphate slag added is: based on the mass of ferric iron in the first filtrate, the mass ratio of ferric iron to ferrophosphate slag is 1:1.5~3. And / or, in step S2, when the reducing waste residue is ferrophosphate slag, the reaction temperature of the first filtrate with the ferrophosphate slag is 80~100℃, and the reaction time is 1.5~3h.

3. The method for treating iron-containing waste slag using waste-to-waste technology according to claim 1, characterized in that, In step S2, when battery black powder is used as the reducing waste residue, the amount of battery black powder added is: based on the mass of ferric iron in the diluent, the mass ratio of ferric iron to battery black powder is 1:30~40; the amount of sulfuric acid added is: the mass ratio of sulfuric acid to battery black powder is 0.5~0.9:1, and the concentration of sulfuric acid is 98%. And / or, in step S2, when the reducing waste residue is battery black powder, the reaction temperature is room temperature and the reaction time is 1.5~3h.

4. The method for treating iron-containing waste slag using waste-to-waste technology according to claim 1, characterized in that, In step S3, the amount of phosphoric acid added is based on the total iron in the second filtrate. After the addition of phosphoric acid, the ratio of the molar amount of phosphate to the molar amount of total iron in the second filtrate is 1.05~1.15:

1.

5. The method for treating iron-containing waste slag using waste-to-waste technology according to claim 1, characterized in that, In step S3, adjusting and controlling the pH of the first filtrate to 1.5~3 is done by adding an alkaline solution; Alternatively, in step S3, adjusting and controlling the pH of the first filtrate to 1.5~3 includes: first adding battery black powder to the first filtrate and adjusting the pH of the first filtrate to 0.3~1.3; Then, an alkaline solution is added to the first filtrate to control the pH of the first filtrate to 1.5-3.

6. The method for treating iron-containing waste slag using waste-to-waste technology according to claim 1, characterized in that, In step S1, the iron-containing waste residue includes at least one of sulfuric acid residue and copper smelting residue; And / or, in step S1, the acid used for acid leaching is sulfuric acid; or, the acid used for acid leaching is a mixture of sulfuric acid and phosphoric acid. And / or, in step S1, the iron-containing waste residue is acid-leached at a temperature of 20~95℃ for 1~3 hours.

7. The method for treating iron-containing waste slag using waste-to-waste technology according to claim 1, characterized in that, In step S1, when the iron-containing waste residue is subjected to acid leaching treatment, the acid used is sulfuric acid with a concentration of 98%; during the acid leaching treatment, water is also added to the iron-containing waste residue, and the mass ratio of iron-containing waste residue, acid and water is 100:80~150:200~500. Alternatively, in step S1, when the iron-containing waste slag is subjected to acid leaching treatment, the acid used is a mixed acid consisting of 98% sulfuric acid and 85% phosphoric acid; during the acid leaching treatment, water is also added to the iron-containing waste slag, and the mass ratio of iron-containing waste slag, mixed acid and water is 100:90~300:200~500.

8. The method for treating iron-containing waste slag using waste-to-waste technology according to claim 1, characterized in that, In step S4, after adding the oxidant, the reaction is carried out at a temperature of 45~50℃ for 0.5~1.5 hours.

9. A battery-grade iron phosphate, characterized in that, The battery-grade iron phosphate is prepared by the method of treating iron-containing waste residue using waste-to-waste treatment as described in any one of claims 1 to 8.

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