Method for recovering and preparing refined phosphoric acid from iron phosphate waste residue

Abstract

The invention discloses a method for recovering and preparing refined phosphoric acid from iron phosphate waste residues, which comprises the following steps: firstly, carrying out acid leaching reaction on the iron phosphate waste residues, and filtering to obtain a phosphoric acid solution mixed with metal impurities; adding an extraction agent formed by compounding an extraction agent B and an extraction agent C into the phosphoric acid solution for extraction and phase separation to obtain an organic phase loaded with phosphoric acid and metal impurities; washing the organic phase loaded with the phosphoric acid and the metal impurities by adopting a composite washing solvent formed by compounding an extracting agent C and an acid solution to remove the metal impurities in the organic phase so as to obtain an organic phase loaded with the phosphoric acid; and finally, carrying out reverse extraction on the obtained organic phase loaded with phosphoric acid by adopting pure water to obtain a phosphoric acid solution, and carrying out evaporation concentration to obtain refined phosphoric acid. According to the method, on the basis that the iron phosphate waste residues are subjected to acid leaching to obtain the phosphoric acid solution, the composite extraction agent is adopted for assisted extraction, and the composite washing solvent is adopted for washing after extraction, so that the phosphoric acid yield can be increased (the yield can reach 90% or above), impurities wrapped by the phosphoric acid can be deeply removed, and the method is suitable for industrial production. The purity of refined phosphoric acid is improved and can reach 85% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of recycling iron phosphate waste residues, and in particular relates to a method for recycling and preparing refined phosphoric acid from iron phosphate waste residues. Background Art

[0002] In the new energy industry, lithium iron phosphate batteries are widely used in new energy vehicles, electric buses, etc. due to their low price and high safety. With the rapid development of the industry, the demand for lithium iron phosphate batteries is increasing. However, the amount of scrapped lithium iron phosphate batteries is also increasing rapidly. Therefore, how to reasonably and environmentally friendly deal with scrapped lithium iron phosphate batteries is a major problem that needs to be solved in the industry.

[0003] At present, the recycling of waste lithium iron phosphate batteries mainly involves selective recycling by oxidative acid leaching after pretreatment to extract lithium metal. However, a large amount of ferrophosphorus slag is generated in this process. If it is not properly treated and utilized, the large amount of valuable metal phosphorus and iron contained in it will cause waste of resources and environmental pollution. Therefore, the effective recycling of ferrophosphorus slag generated during the recycling process has considerable economic and environmental benefits.

[0004] Phosphoric acid (H3PO4) is an important component in the production of phosphates used as fertilizers. Due to the huge demand for fertilizers and other applications, phosphoric acid is the second largest inorganic acid after sulfuric acid and occupies an important position in the chemical industry. Currently, the main methods for preparing phosphoric acid are thermal and wet methods, but the raw materials for both methods are phosphate ore. With the reduction of phosphate ore supply, it is critical to prepare phosphoric acid by recycling ferrophosphorus slag.

[0005] For preparing phosphoric acid from ferrophosphorus slag, a method for preparing phosphoric acid by recovering ferrophosphorus slag is disclosed in the existing patent CN 116835661 A, which first converts the phosphorus element in the ferrophosphorus slag into sodium phosphate by using sodium hydroxide, then adds calcium hydroxide to convert it into calcium phosphate, and finally adds sulfuric acid, and filters to obtain calcium sulfate and phosphoric acid. The phosphoric acid obtained in this process is crude phosphoric acid, and the added calcium hydroxide makes the obtained phosphoric acid contain a higher content of calcium ions. The obtained phosphoric acid needs to be further impurity-removed and concentrated before it can be applied, and many steps involve high-temperature treatment, and the risk factor is high. Therefore, this method is not conducive to large-scale refined phosphoric acid.

[0006] Based on this, a new method for recovering and preparing refined phosphoric acid from iron phosphate waste is now studied. This method can improve the yield of phosphoric acid while deeply removing the impurities contained therein to improve the purity, that is, achieving a balance between yield and purity. Summary of the invention

[0007] Purpose of the invention: The technical problem to be solved by the present invention is to provide a new method for recovering and preparing refined phosphoric acid from iron phosphate waste residue, which can improve the yield of phosphoric acid while deeply removing the impurities contained therein, thereby improving the purity of the refined phosphoric acid.

[0008] Technical solution: The method for recovering and preparing refined phosphoric acid from iron phosphate waste residue of the present invention comprises the following steps:

[0009] (1) subjecting the iron phosphate waste residue to acid leaching reaction and filtering to obtain a phosphoric acid solution mixed with metal impurities;

[0010] (2) adding a composite extracting liquid to a phosphoric acid solution, extracting and separating the phases at a pH value of 0.5 to 7 to obtain an organic phase loaded with phosphoric acid and metal impurities; the composite extracting agent in the composite extracting liquid comprises an extracting agent B and an extracting agent C in a volume ratio of 1:(1 to 9); the extracting agent B comprises n-butanol, n-hexanol, n-octanol, tributyl phosphate, butyl-N,N-di(2-ethylhexyl)carbamoylnonylphosphonate, methyl isobutyl ketone, di-2-ethylhexyl phosphoric acid, trioctyldecyl tertiary amine, isopentanol, sorbitol monooleate or dioctyl phosphate; the extracting agent C comprises ethylhexyl mono-2-ethylhexyl phosphate, dibutyl sulfoxide, 2-(bis((2-ethylhexyl)oxy)phosphino)-2-hydroxyacetic acid, N,N-di(1-methylheptyl)acetamide, dimethylheptyl methylphosphonate or dinonylnaphthalenesulfonic acid;

[0011] (3) washing the organic phase loaded with phosphoric acid and metal impurities with a composite washing solvent to remove the metal impurities in the organic phase and obtain an organic phase loaded with phosphoric acid; the composite washing solvent comprises an extractant C and an acid solution;

[0012] (4) The organic phase loaded with phosphoric acid obtained in step (3) is stripped with pure water to obtain a phosphoric acid solution, and then concentrated by evaporation to obtain refined phosphoric acid.

[0013] The invention is based on obtaining a phosphoric acid solution by acid leaching ferric phosphate waste residue, and adopts a composite extractant formed by compounding an extractant B and an extractant C in a volume ratio of 1:(1-9) to assist extraction. A large amount of extractant C assists extraction, and can effectively avoid the problem of low phosphoric acid yield caused by adopting a single extractant B for extraction (the extractant B has a strong binding force with phosphate radicals, resulting in difficulty in stripping), so as to improve the yield of phosphoric acid; at the same time, a small amount of extractant B preferentially selects phosphate radicals to form a complex, and reduces the extraction of impurity metals in an organic phase, that is, the phosphoric acid extraction yield is improved while reducing the content of impurity metals in the extracted phosphoric acid, so as to form a system of extractant B-phosphate complex, extractant B-trace impurity metal ion complex, extractant C-phosphate complex, and extractant C-low-content impurity metal ion complex in the organic phase.

[0014] And the present invention is based on the above organic phase system where low-impurity metals are extracted, and uses extractant C in combination with acid solution to wash and remove impurities, so that extractant C reacts with extractant C-low-content impurity ions formed in the extraction stage, and then exchanges metal ions in the extractant C-low-content impurity ion complex to obtain extractant C and metal ions entering the raffinate phase, that is, the impurity metals are washed preferentially, and phosphoric acid can be effectively avoided from being washed. At this time, the components in the organic phase are extractant B-phosphate complex, extractant B-trace impurity metal ion complex, extractant C-phosphate complex, extractant C, extractant C-trace impurity ion complex. Based on this organic phase system, the phosphate ions in the organic phase can be stripped by washing with a small amount of water, and refined phosphoric acid can be obtained after concentration, and the (stripped) extracted extractants B and extractants C can be further recycled.

[0015] Furthermore, in step (1) and step (4) of the recovery method, the amount of the acid solution added is 1 to 1.05 times the theoretical amount, and the acid solution used for the acid leaching includes at least formic acid, citric acid, phosphoric acid, nitric acid, sulfuric acid or hydrochloric acid.

[0016] Furthermore, in step (1) of the recovery method, the reaction time of the acid leaching is 1 to 5 hours, and the reaction temperature is 25 to 50°C.

[0017] Furthermore, in step (2) of the recovery method, the composite extract comprises a composite extractant and a diluent in a volume ratio of 1:(1 to 9).

[0018] Furthermore, in step (2) of the recovery method, the O / A ratio of the composite extract to the phosphoric acid solution of the extraction solution is (1-9):1.

[0019] Furthermore, in step (3) of the recovery method, the proportion of extractant C in the composite washing solvent is 5 to 50%, the proportion of acid solution is 50 to 95%, the concentration of acid solution is 10 to 90%, and the amount of composite washing solvent used is 5 to 50% of the volume of the organic phase loaded with phosphoric acid and metal impurities.

[0020] Furthermore, in step (4) of the recovery method, the amount of pure water used is 10 to 150% of the volume of the organic phase loaded with phosphoric acid.

[0021] Beneficial effect: Compared with the prior art, the significant advantages of the present invention are: the method is based on obtaining a phosphoric acid solution by acid leaching the iron phosphate waste residue, and assisting the extraction by using a composite extractant prepared by compounding different amounts of extractant B and extractant C, and after the extraction, washing is carried out by using a composite washing solvent prepared by compounding different amounts of extractant C and acid solution, thereby improving the yield of phosphoric acid (the yield can reach more than 90%) while deeply removing the impurities contained therein, thereby improving the purity of the refined phosphoric acid, and the purity can reach more than 85%. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention discloses a flow chart of recovering phosphorus from ferric phosphate waste to prepare refined phosphoric acid. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0024] It should be noted that in the following embodiments of the present invention, the ferrophosphorus slag is produced from the selective lithium extraction process of lithium iron phosphate, and contains 96% ferrophosphate, 3% carbon, and the rest are inevitable impurity ions in terms of weight percentage.

[0025] Example 1

[0026] This embodiment 1 is a method for recovering and preparing refined phosphoric acid from iron phosphate waste residue, such as Figure 1 As shown, the following steps are included:

[0027] (1) Take 150g of iron phosphate waste residue, add 109g of hydrochloric acid to react, the reaction temperature is room temperature (25°C), the reaction time is 1h, after the reaction is completed, filter and remove the carbon residue, at this time, a mixed solution of ferric chloride and phosphoric acid is obtained.

[0028] (2) extracting the mixed solution of ferric chloride and phosphoric acid obtained in step (1) by a composite extracting liquid, wherein the composite extracting liquid comprises a composite extracting agent and a diluent sulfonated kerosene in a volume ratio of 1:4, the composite extracting agent is n-butanol and ethylhexyl phosphate mono-2-ethylhexyl ester in a volume ratio of 1:3, the composite extracting liquid and the mixed solution O / A=1:1, and after extraction and standing for phase separation, an organic phase loaded with phosphoric acid and a ferric chloride solution are obtained.

[0029] (3) washing the organic phase loaded with phosphoric acid and metal impurities obtained in step (2) with a composite washing solvent to remove the metal impurities in the organic phase and obtain an organic phase loaded with phosphoric acid; the composite washing solvent comprises 10% of ethylhexyl mono-2-ethylhexyl phosphate and 90% of a hydrochloric acid solution, the concentration of the hydrochloric acid solution is 25%, and the amount of the composite washing solvent is 10% of the volume of the organic phase.

[0030] (4) Adding pure water to the purified organic phase loaded with phosphoric acid obtained in step (3) for stripping, wherein the pure water used is 60% of the volume of the purified organic phase, and the mixture is allowed to stand for phase separation to obtain a stripped organic phase and a phosphoric acid solution.

[0031] (5) The phosphoric acid solution obtained by stripping in step (4) is heated and concentrated to obtain high-purity refined phosphoric acid; during the concentration, the temperature of the phosphoric acid is controlled at 70 to 85° C., and the temperature of the low-pressure steam is controlled at 135 to 140° C.

[0032] Comparative Example 1-1

[0033] The comparative example 1-1 is substantially the same as the example 1, except that only n-butanol is used for extraction.

[0034] Comparative Example 1-2

[0035] The comparative example 1-2 is substantially the same as the example 1, except that only hydrochloric acid is used for washing.

[0036] The element contents of the refined phosphoric acid recovered in Example 1 and Comparative Examples 1-1 and 1-2 were tested, and the results are shown in Table 1 below.

[0037] Table 1 Element contents of the refined phosphoric acid recovered from Example 1, Comparative Example 1-1 and Comparative Example 1-2

[0038]

[0039]

[0040] As can be seen from Table 1, compared with the recovery method of the present invention, although Comparative Example 1-1 uses only n-butanol in the extractant B for extraction, the selectivity of the impurities in the extraction stage and the priority of the impurities in the washing process can make the final impurity metal content lower, but the content of phosphoric acid is also relatively small, and the yield is also low. Although Comparative Example 1-2 uses a composite extractant extraction method, the washing is only done with hydrochloric acid, resulting in the impurity metals not being effectively removed during the washing, and the phosphoric acid is also washed, thereby not only reducing the content of phosphoric acid compared to the present invention, but also failing to effectively remove the impurity metals in depth.

[0041] Example 2

[0042] The method for recovering and preparing refined phosphoric acid from ferric phosphate waste residue in Example 2 comprises the following steps:

[0043] (1) 150 g of iron phosphate waste residue was added with 199 g of sulfuric acid for reaction at room temperature (25° C.) for 2 h. After the reaction was completed, the carbon residue was filtered out to obtain a mixed solution of iron sulfate and phosphoric acid;

[0044] (2) extracting the mixed solution of ferric sulfate and phosphoric acid obtained in step (1) by a composite extracting liquid, wherein the composite extracting liquid comprises a composite extracting agent and a diluent sulfonated kerosene in a volume ratio of 1:5, the composite extracting agent is n-hexanol and dibutyl sulfoxide in a volume ratio of 1:2, the composite extracting liquid and the mixed solution O / A=2:1, and after extraction and standing for phase separation, an organic phase loaded with phosphoric acid and a ferric sulfate solution are obtained;

[0045] (3) washing the organic phase loaded with phosphoric acid and metal impurities obtained in step (2) with a composite washing solvent to remove the metal impurities in the organic phase and obtain an organic phase loaded with phosphoric acid; the composite washing solvent comprises 10% dibutyl sulfoxide and 90% sulfuric acid solution, the concentration of the sulfuric acid solution is 40%, and the amount of the composite washing solvent is 5% of the volume of the organic phase;

[0046] (4) Adding pure water to the purified organic phase loaded with phosphoric acid obtained in step (3) for stripping, wherein the pure water used is 40% of the volume of the purified organic phase, and the mixture is allowed to stand for phase separation to obtain a stripped organic phase and a phosphoric acid solution.

[0047] (5) The phosphoric acid solution obtained by stripping in step (4) is heated and concentrated to obtain high-purity refined phosphoric acid; during the concentration, the temperature of the phosphoric acid is controlled at 70 to 85° C., and the temperature of the low-pressure steam is controlled at 135 to 140° C.

[0048] Comparative Example 2-1

[0049] The comparative example 2-1 is substantially the same as the example 1, except that only dibutyl sulfoxide is used for extraction.

[0050] Comparative Example 2-2

[0051] The comparative example 2-2 is substantially the same as the example 1, except that only sulfuric acid is used for washing.

[0052] The element content of the recovered refined phosphoric acid obtained in Example 2 and Comparative Example 2-1 and Comparative Example 2-2 was tested, and the results obtained are shown in Table 2 below.

[0053] Table 2 Element contents of the refined phosphoric acid recovered from Example 2, Comparative Example 2-1 and Comparative Example 2-2

[0054] Example Yield <![CDATA[H3PO4]]> Fe Mg F Ca C <![CDATA[SO4 2- ]]> Cl unit Example 2 95.00 85.09 0.003 0.003 0.02 0.004 0.004 0.02 0.001 ％ Comparative Example 2-1 84.02 71.37 0.004 0.003 0.06 0.005 0.006 0.03 0.003 ％ Comparative Example 2-2 91.17 79.84 0.01 0.007 0.06 0.008 0.007 0.06 0.003 ％

[0055] Example 3

[0056] The method for recovering and preparing refined phosphoric acid from ferric phosphate waste residue in Example 3 comprises the following steps:

[0057] (1) 450 g of iron phosphate waste residue was added with 136 g of a mixed acid of nitric acid / hydrochloric acid for reaction, wherein the ratio of nitric acid to hydrochloric acid was 1 / 2, the reaction temperature was 30° C., the reaction time was 2 h, and after the reaction was completed, the carbon residue was filtered out to obtain a mixed solution of iron nitrate, iron chloride and phosphoric acid;

[0058] (2) extracting the mixed solution obtained in step (1) with a composite extractant, wherein the composite extractant comprises a composite extractant and a diluent sulfonated kerosene in a volume ratio of 1:3, the composite extractant is butyl-N,N-di(2-ethylhexyl)carbamoylnonylphosphonate and 2-(bis((2-ethylhexyl)oxy)phosphino)-2-hydroxyacetic acid in a volume ratio of 1:5, the composite extractant and the mixed solution O / A=4:1, and after extraction and standing for phase separation, an organic phase loaded with phosphoric acid and a solution of ferric nitrate and ferric chloride are obtained;

[0059] (3) washing the organic phase loaded with phosphoric acid and metal impurities obtained in step (2) with a composite washing solvent to remove the metal impurities in the organic phase and obtain an organic phase loaded with phosphoric acid; the composite washing solvent comprises 40% of 2-(bis((2-ethylhexyl)oxy)phosphino)-2-hydroxyacetic acid and 60% of nitric acid solution, the concentration of the nitric acid solution is 20%, and the amount of the composite washing solvent is 20% of the volume of the organic phase;

[0060] (4) adding pure water to the purified organic phase loaded with phosphoric acid obtained in step (3) for stripping, wherein the pure water used is 80% of the volume of the purified organic phase, and the mixture is allowed to stand for phase separation to obtain a stripped organic phase and a phosphoric acid solution.

[0061] (5) The phosphoric acid solution obtained by stripping in step (4) is heated and concentrated to obtain high-purity refined phosphoric acid; during the concentration, the temperature of the phosphoric acid is controlled at 70 to 85° C., and the temperature of the low-pressure steam is controlled at 135 to 140° C.

[0062] Comparative Example 3-1

[0063] The comparative example 3-1 is substantially the same as the example 1, except that only a single butyl-N,N-di(2-ethylhexyl)carbamoylnonylphosphonate is used for extraction.

[0064] Comparative Example 3-2

[0065] The comparative example 3-2 is substantially the same as the example 1, except that only nitric acid is used for washing.

[0066] The element content of the recovered refined phosphoric acid obtained in Example 3 and Comparative Examples 3-1 and 3-2 was tested, and the results obtained are shown in Table 3 below.

[0067] Table 3 Element contents of the refined phosphoric acid recovered from Example 3, Comparative Example 3-1 and Comparative Example 3-2

[0068] Example Yield <![CDATA[H3PO4]]> Fe Mg F Ca C <![CDATA[SO4 2- ]]> Cl unit Example 3 93.89 85.11 0.003 0.002 0.02 0.003 0.004 0.02 0.001 ％ Comparative Example 3-1 84.76 71.79 0.003 0.005 0.04 0.004 0.006 0.03 0.001 ％ Comparative Example 3-2 85.23 78.92 0.008 0.006 0.05 0.007 0.006 0.04 0.002 ％

[0069] It can be seen from the above embodiments that the method of the present invention is based on obtaining a phosphoric acid solution by acid leaching the iron phosphate waste residue, and assisting the extraction by using a composite extractant prepared by compounding different amounts of extractant B and extractant C, and after the extraction, a composite washing liquid prepared by compounding different amounts of extractant C and acid solution is used for washing, thereby improving the yield of phosphoric acid (the yield can reach more than 90%), while deeply removing the impurities contained therein, thereby improving the purity of the refined phosphoric acid, and the purity can reach more than 85%.

[0070] In addition, in addition to the above embodiments, in step (1) and step (4) of the present invention, the acid solution may also include formic acid, citric acid or phosphoric acid. The reaction time of acid leaching may be 1 to 5 hours, and the reaction temperature may be 25 to 50°C. In step (2), the volume ratio of the composite extractant to the diluent may be 1:(1 to 9). The O / A of the composite extractant and the phosphoric acid solution after dilution by the diluent is (1 to 9):1. In step (3), the proportion of extractant C in the composite washing solvent may be 5 to 50%, the proportion of the acid solution may be 50 to 95%, and the concentration of the acid solution may be 10 to 90%. The amount of the composite washing solvent used may be 5 to 50% of the volume of the organic phase loaded with phosphoric acid and metal impurities. In step (4), the amount of pure water used may be 10 to 150% of the volume of the organic phase loaded with phosphoric acid. That is, in the recovery step adopted, similar technical effects can be achieved within the process parameter range defined by the present invention, and thus no separate proof is required.

Claims

1. A method for recovering and preparing refined phosphoric acid from ferric phosphate waste residue, characterized in that: The steps include: (1) subjecting the iron phosphate waste residue to acid leaching reaction and filtering to obtain a phosphoric acid solution mixed with metal impurities; (2) adding a composite extracting liquid to a phosphoric acid solution, extracting and separating the phases at a pH value of 0.5 to 7 to obtain an organic phase loaded with phosphoric acid and metal impurities; the composite extracting agent in the composite extracting liquid comprises an extracting agent B and an extracting agent C in a volume ratio of 1:(1 to 9); the extracting agent B comprises n-butanol, n-hexanol, n-octanol, tributyl phosphate, butyl-N,N-di(2-ethylhexyl)carbamoylnonylphosphonate, methyl isobutyl ketone, di-2-ethylhexyl phosphoric acid, trioctyldecyl tertiary amine, isopentanol, sorbitol monooleate or dioctyl phosphate; the extracting agent C comprises ethylhexyl mono-2-ethylhexyl phosphate, dibutyl sulfoxide, 2-(bis((2-ethylhexyl)oxy)phosphino)-2-hydroxyacetic acid, N,N-di(1-methylheptyl)acetamide, dimethylheptyl methylphosphonate or dinonylnaphthalenesulfonic acid; (3) washing the organic phase loaded with phosphoric acid and metal impurities with a composite washing solvent to remove the metal impurities in the organic phase and obtain an organic phase loaded with phosphoric acid; the composite washing solvent comprises an extractant C and an acid solution; (4) The organic phase loaded with phosphoric acid obtained in step (3) is stripped with pure water to obtain a phosphoric acid solution, and then concentrated by evaporation to obtain refined phosphoric acid.

2. The method for recovering and preparing refined phosphoric acid from ferric phosphate waste according to claim 1, characterized in that: In step (1) and step (4), the acid solution used for the acid leaching includes at least one of formic acid, citric acid, phosphoric acid, nitric acid, sulfuric acid or hydrochloric acid.

3. The method for recovering and preparing refined phosphoric acid from ferric phosphate waste according to claim 1, characterized in that: In step (1), the reaction time of the acid leaching is 1 to 5 hours, and the reaction temperature is 25 to 50°C.

4. The method for recovering and preparing refined phosphoric acid from ferric phosphate waste according to claim 1, characterized in that: In step (2), the composite extract comprises a composite extractant and a diluent in a volume ratio of 1:(1-9).

5. The method for recovering and preparing refined phosphoric acid from ferric phosphate waste according to claim 1, characterized in that: In step (2), the O / A ratio of the composite extract to the phosphoric acid solution is (1-9):

1.

6. The method for recovering and preparing refined phosphoric acid from ferric phosphate waste according to claim 1, characterized in that: In step (3), the proportion of extractant C in the composite washing solvent is 5-50%, the proportion of acid solution is 50-95%, and the concentration of acid solution is 10-90%.

7. The method for recovering and preparing refined phosphoric acid from ferric phosphate waste according to claim 1, characterized in that: In step (3), the amount of the composite washing solvent used is 5 to 50% of the volume of the organic phase loaded with phosphoric acid and metal impurities.

8. The method for recovering and preparing refined phosphoric acid from ferric phosphate waste according to claim 1, characterized in that: In step (4), the amount of pure water used is 10 to 150% of the volume of the organic phase loaded with phosphoric acid.

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