A method for recovering and preparing refined phosphoric acid from ferric phosphate waste

Abstract

The present invention discloses a method for recovering and preparing refined phosphoric acid from ferric phosphate waste residue, wherein the ferric phosphate waste residue is first subjected to acid leaching reaction and filtration to obtain a phosphoric acid solution mixed with metal impurities; an extractant composed of extractant B and extractant C is added to the phosphoric acid solution for extraction and phase separation to obtain an organic phase loaded with phosphoric acid and metal impurities; a composite washing solvent composed of extractant C and acid solution is then used to wash the organic phase loaded with phosphoric acid and metal impurities to remove the metal impurities in the organic phase to obtain an organic phase loaded with phosphoric acid; finally, the obtained organic phase loaded with phosphoric acid is stripped with pure water to obtain a phosphoric acid solution, and refined phosphoric acid is obtained by evaporation and concentration. The method of the present invention is based on obtaining a phosphoric acid solution by acid leaching the ferric phosphate waste residue, and then the composite extractant is used to assist extraction, and the composite washing solvent is used for washing after extraction, thereby being able to improve the phosphoric acid yield (the yield can reach more than 90%) while removing the depth of the impurities it carries, thereby improving the purity of the refined phosphoric acid, and the purity can reach more than 85%.

Description

Technical Field

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

[0002] In the new energy industry, lithium iron phosphate batteries are widely used in new energy vehicles, electric buses, and other applications due to their low price and high safety. With the rapid development of the industry, demand for lithium iron phosphate batteries is increasing. However, the number of discarded lithium iron phosphate batteries is also rapidly increasing. Therefore, how to properly and environmentally handle these discarded lithium iron phosphate batteries is a major challenge that the industry urgently needs to solve.

[0003] Currently, the recycling of spent lithium iron phosphate batteries primarily involves pretreatment followed by oxidative acid leaching to extract the lithium metal for selective recovery. However, this process produces a large amount of ferrophosphorus slag. If not properly processed and utilized, the large amounts of valuable metals phosphorus and iron contained in it can lead to resource waste and environmental pollution. Therefore, effectively recycling this ferrophosphorus slag produced during the recycling process offers significant economic and environmental benefits.

[0004] Phosphoric acid (H3PO4) is a key component in the production of phosphates used in fertilizers. Due to the enormous demand for fertilizers and other applications, phosphoric acid is the second most produced inorganic acid after sulfuric acid and holds a crucial position in the chemical industry. Currently, phosphoric acid is produced primarily through thermal and wet methods, but both rely on phosphate rock as the raw material. With the dwindling supply of phosphate rock, recovering ferrophosphorus slag to produce phosphoric acid has become increasingly important.

[0005] For preparing phosphoric acid from ferrophosphorus slag, a method for preparing phosphoric acid by recycling ferrophosphorus slag is disclosed in 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 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 being studied. This method can improve the yield of phosphoric acid while deeply removing the impurities it carries with it, thereby improving 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 novel method for recovering and preparing refined phosphoric acid from ferric phosphate waste, 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 of the present invention for recovering and preparing refined phosphoric acid from ferric phosphate waste residue comprises the following steps:

[0009] (1) subjecting the ferric phosphate waste residue to acid leaching 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, which is then concentrated by evaporation to obtain refined phosphoric acid.

[0013] The present invention is based on obtaining a phosphoric acid solution by acid leaching ferric phosphate waste residue. A composite extractant prepared by compounding an extractant B and an extractant C in a volume ratio of 1:(1-9) is used for assisted extraction. A large amount of extractant C assists in extraction, thereby effectively avoiding the problem of low phosphoric acid yield caused by using a single extractant B for extraction (the extractant B has a strong binding force with phosphate radicals, resulting in difficulty in back extraction), thereby improving the yield of phosphoric acid. At the same time, a small amount of extractant B preferentially selects phosphate radicals to form a complex, thereby reducing the extraction of impurity metals in an organic phase, that is, achieving improved phosphoric acid extraction yield while reducing the content of impurity metals in the extracted phosphoric acid, thereby forming 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] The present invention is based on the above-mentioned organic phase system in which 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 the metal ions in the extractant C-low-content impurity ion complex to obtain extractant C and the 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, and 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 (strip) extracted extractants B and 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 in 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 5-50%, the proportion of acid solution is 50-95%, the concentration of acid solution is 10-90%, and the amount of composite washing solvent used is 5-50% 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 effects: Compared with the prior art, the significant advantages of the present invention are: this 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 composed of different amounts of extractant B and extractant C, and after extraction, washing is carried out using a composite washing solvent composed of different amounts of extractant C and acid solution. This can improve 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 provides a flow chart for 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 with reference to the accompanying drawings and embodiments.

[0024] It should be noted that in the following examples 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 remainder being inevitable impurity ions, by weight percentage.

[0025] Example 1

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

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

[0028] (2) extracting the mixed solution of ferric chloride and phosphoric acid obtained in step (1) by a composite extractant, wherein the composite extractant comprises a composite extractant and a diluent sulfonated kerosene in a volume ratio of 1:4, and the composite extractant comprises n-butanol and ethylhexyl mono-2-ethylhexyl phosphate in a volume ratio of 1:3, and the O / A ratio of the composite extractant to the mixed solution is 1:1. After the extraction is allowed to stand and separate, 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 used 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 back extraction, wherein the pure water used is 60% of the volume of the purified organic phase loaded with phosphoric acid, and mixing and standing to separate the phases to obtain a back-extracted 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 70-85° C., and the temperature of the low-pressure steam is controlled at 135-140° C.

[0032] Comparative Example 1-1

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

[0034] Comparative Example 1-2

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

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

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

[0038]

[0039]

[0040] As shown in Table 1, compared to the recovery method of the present invention, although Comparative Example 1-1 utilizes only n-butanol in Extractant B for extraction, and the control of impurity selectivity during the extraction stage and impurity priority during the washing process results in a lower final impurity metal content, the phosphoric acid content is also relatively low, resulting in a low yield. Comparative Example 1-2, while employing a composite extraction agent, utilizes only hydrochloric acid for washing, resulting in ineffective removal of impurity metals and also washing of phosphoric acid. Consequently, while the phosphoric acid content is reduced compared to the present invention, the impurity metals are also not effectively and deeply removed.

[0041] Example 2

[0042] This embodiment 2 is a method for recovering and preparing refined phosphoric acid from ferric phosphate waste, comprising the following steps:

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

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

[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 back extraction, wherein the pure water used is 40% of the volume of the purified organic phase loaded with phosphoric acid, and mixing and standing to separate the phases to obtain a back-extracted 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 70-85° C., and the temperature of the low-pressure steam is controlled at 135-140° C.

[0048] Comparative Example 2-1

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

[0050] Comparative Example 2-2

[0051] Comparative Example 2-2 is substantially the same as 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 Examples 2-1 and 2-2 was tested, and the results are shown in Table 2 below.

[0053] Table 2 Element contents of the purified 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] This embodiment 3 is a method for recovering and preparing refined phosphoric acid from ferric phosphate waste, comprising the following steps:

[0057] (1) 450 g of ferric phosphate waste residue was added to 136 g of a mixed acid of nitric acid and hydrochloric acid, with the ratio of nitric acid to hydrochloric acid being 1 / 2, the reaction temperature being 30° C., and the reaction time being 2 h. After the reaction was completed, the carbon residue was filtered out to obtain a mixed solution of ferric nitrate, ferric 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 comprises 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 extracting and standing to separate phases to obtain an organic phase loaded with phosphoric acid and a solution of ferric nitrate and ferric chloride;

[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, thereby obtaining 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 a nitric acid solution, wherein 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 back extraction, wherein the pure water used is 80% of the volume of the purified organic phase loaded with phosphoric acid, and mixing and standing to separate the phases to obtain a back-extracted 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 70-85° C., and the temperature of the low-pressure steam is controlled at 135-140° C.

[0062] Comparative Example 3-1

[0063] Comparative Example 3-1 is substantially the same as Example 1, except that only butyl-N,N-di(2-ethylhexyl)carbamoylnonylphosphonate is used for extraction.

[0064] Comparative Example 3-2

[0065] Comparative Example 3-2 is substantially the same as 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 are shown in Table 3 below.

[0067] Table 3 Element contents of the purified 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 examples 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 composed of different amounts of extractant B and extractant C, and after the extraction, washing is carried out using a composite washing liquid composed of different amounts of extractant C and acid solution. This can improve the phosphoric acid yield (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 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 the 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 ratio of the composite extractant to the phosphoric acid solution after dilution with 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 steps adopted, similar technical effects can be achieved within the process parameter range defined by the present invention, and thus no separate examples will be provided.

Claims

1. A method for recovering and preparing refined phosphoric acid from ferric phosphate waste, characterized in that: The steps include: (1) subjecting the ferric phosphate waste residue to acid leaching reaction and filtering to obtain a phosphoric acid solution mixed with metal impurities; (2) adding a composite extractant 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 extractant in the composite extractant comprises an extractant B and an extractant C in a volume ratio of 1:(1 to 9); the extractant 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 extractant 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, which is 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: The acid solution used for the acid leaching in step (1) and the acid solution in step (4) both include 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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