Method for extracting and separating aluminum from ferrophosphorus waste leachate

Abstract

The invention discloses a method for extracting and separating aluminum from ferrophosphorus waste leachate, which comprises the following steps: mixing ferrophosphorus waste with water to prepare slurry, performing acid leaching under the condition that the pH value is 1.5-2.5, and adding a reducing agent to obtain the leachate; diluting a carboxylic acid extracting agent and an acidic phosphorus extracting agent, and extracting the leachate under the condition that the pH value is 1-3 to respectively obtain an Al-loaded organic phase and a Fe-containing raffinate; and finally, collecting the Al-loaded organic phase, mixing the Al-loaded organic phase with water, stirring, washing, carrying out reverse extraction on the washed Al-loaded organic phase by using acid liquor, separating aluminum from the ferrophosphorus waste, and collecting the reverse-extracted organic phase for recycling. According to the method, aluminum can be effectively removed, the technical problem that iron and aluminum are difficult to separate is effectively solved, and meanwhile the balance between efficient extraction and difficult back extraction of the acid phosphorus extraction agent can be achieved.

Description

Technical Field

[0001] The invention belongs to the field of recycling ferrophosphorus waste, and in particular relates to a method for extracting and separating aluminum from ferrophosphorus waste leaching solution. Background Art

[0002] With the rapid development of the new energy vehicle industry, the effective treatment and disposal of the lithium iron phosphate batteries it relies on after reaching the end of their service life has become an increasingly important issue that needs to be addressed. Waste lithium iron phosphate batteries contain rich valuable metal resources, mainly including key elements such as lithium, nickel, cobalt, and manganese, and have extremely high recycling and reuse value. At present, the main methods for recycling waste phosphoric acid are pyrolysis and wet processing. Wet acid leaching has become the most widely used method in industry due to its simple technical process, high recovery purity, and low recovery cost. However, the aluminum foil and the positive electrode material cannot be separated during the pretreatment process, so that the waste leachate contains aluminum impurities, which has a great impact on the purity of the product. At present, the aluminum impurities in the feed solution are removed in industry by adding soda ash solution to the leachate to convert it into a precipitate for removal. The iron and aluminum mixture in the precipitate produced by this method is difficult to separate, and the auxiliary material consumption is large.

[0003] Another commonly used industrial method for separating aluminum from leachate is extraction, which involves adding a suitable extractant to the leachate to allow the extractant to enter the organic phase and be separated from the feed liquid. Commonly used acidic phosphorus extractants have a good extraction effect on aluminum, but a large amount of iron will also enter the organic phase during the extraction process, making it difficult to separate iron from aluminum. In addition, the molecular structure of the acidic phosphorus extractant contains phosphate groups, and the complexes formed by these groups and metal ions often have high stability and are not easy to dissociate under normal conditions. The difficulty of stripping the acidic phosphorus extractant increases, making it difficult to recycle the extractant and increasing the cost of use.

[0004] Therefore, a solution is now proposed to overcome the difficulty of removing aluminum in the current extraction process. Summary of the invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a method for extracting and separating aluminum from ferrophosphorus waste leachate, which can not only effectively remove aluminum and effectively solve the technical problem of difficult iron-aluminum separation, but also achieve a balance between efficient extraction by acidic phosphorus extractants and difficult back-extraction.

[0006] Technical solution: The method for extracting and separating aluminum from ferrophosphorus waste leaching solution of the present invention comprises the following steps:

[0007] (1) mixing ferrophosphorus waste with water to prepare pulp, acid leaching is performed at a pH of 1.5-2.5 and a reducing agent is added to obtain a leachate;

[0008] (2) after diluting the carboxylic acid extractant and the acidic phosphorus extractant, extracting the above-mentioned leachate at a pH of 1-3 to obtain an organic phase loaded with Al and a raffinate containing Fe, respectively;

[0009] (3) Collecting the Al-loaded organic phase and mixing it with water for washing; stripping the Al-loaded organic phase with acid solution to separate aluminum from the ferrophosphorus waste; and collecting the stripped organic phase for recycling.

[0010] The present invention is based on the process route of removing aluminum impurities from ferrophosphorus waste. A reducing agent is used to reduce trivalent iron to divalent iron during acid leaching. On the one hand, it can ensure that Al is preferentially and effectively extracted in the subsequent extraction, while divalent iron is retained in the leachate, thereby improving the separation of iron and aluminum; on the other hand, it reduces the loss of iron caused by the trivalent iron being extracted into the organic phase in the subsequent extraction; based on the leaching conditions, during the extraction, a synergistic extractant composed of a carboxylic acid extractant and an acidic phosphorus extractant is used for extraction under a pH of 1-3, so that Al in the leachate can be effectively extracted into the organic phase, while divalent Fe is retained in the residual phase. In addition, based on the compounding of the carboxylic acid extractant and the acidic phosphorus extractant, and the extraction mechanism of the two with Al, that is, aluminum is combined with the carboxylic acid extractant and the acidic phosphorus extractant to form a compound, and the compound can make Al more easily released from the extractant by using an acid solution during back extraction, while maintaining the stability of the extractant structure, so that it can be used again in the subsequent extraction process.

[0011] Furthermore, in step (1) of the method, the volume ratio of the ferrophosphorus waste to water is 1:(1-5).

[0012] Furthermore, in step (1) of the method, the acid solution used for acid leaching is concentrated sulfuric acid, concentrated hydrochloric acid or concentrated nitric acid, and the acid leaching time is 20-90 minutes.

[0013] Furthermore, in step (1) of the method, the reducing agent is one or more of ascorbic acid, sodium bisulfite, ammonium bisulfite, sodium sulfite, and ammonium sulfite, and the amount of the reducing agent added is 0.05 to 1 mol / L.

[0014] Furthermore, in step (2) of the method, the dilution of the carboxylic acid extractant and the acidic phosphorus extractant is carried out by mixing the carboxylic acid extractant and the acidic phosphorus extractant in a volume ratio of 1: (0.02-0.3): (0.5-0.8).

[0015] Furthermore, the carboxylic acid extractant of the method comprises at least one of versatic 10, versatic 911, oxyacetic acid, bromolauric acid or neodecanoic acid.

[0016] Furthermore, the acidic phosphorus extractant used in the method may include one of di(2-ethylhexyl)phosphoric acid, 2-ethylhexyl monophosphate (2-ethylhexyl) ester, dodecyl monophosphate or di(2-ethylhexyl) phosphinic acid.

[0017] Preferably, the carboxylic acid extractant of the method can be neodecanoic acid, and the acidic phosphorus extractant can be di(2-ethylhexyl)phosphoric acid. Based on the synergistic extractants, during extraction, aluminum is combined with one neodecanoic acid and two di(2-ethylhexyl)phosphoric acids to form a compound, and during stripping, an acid solution is used to react the hydrogen ions in the acid solution with the compound, and neodecanoic acid and di(2-ethylhexyl)phosphoric acid are recovered for recycling.

[0018] Furthermore, the diluent used in the method may include one of sulfonated kerosene, 200# solvent oil, 260# solvent oil or light white oil.

[0019] Furthermore, in step (5) of the method, the acidity of the acid solution is 2-12 mol H + The volume ratio of the organic phase loaded with Al to the acid solution is 1:(1-6).

[0020] Beneficial effects: Compared with the prior art, the significant advantages of the present invention are: this method can not only effectively remove aluminum and effectively solve the technical problem of difficult iron-aluminum separation, but also can achieve a balance between the efficient extraction of acidic phosphorus extractants and the difficulty of back extraction. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Flow chart of the method of the present invention. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be noted that the extractant used in the present invention can be directly purchased from the market.

[0023] The method for extracting and separating aluminum from ferrophosphorus waste leachate of the present invention comprises the following steps:

[0024] (1) mixing ferrophosphorus waste with water to prepare pulp, adding a reducing agent and performing acid leaching at a pH of 1.5-2.5 to obtain a leachate;

[0025] (2) after diluting the carboxylic acid extractant and the acidic phosphorus extractant, extracting the above-mentioned leachate at a pH of 1-3 to obtain an organic phase loaded with Al and a raffinate containing Fe, respectively;

[0026] (3) Collecting the Al-loaded organic phase and mixing it with water for washing; stripping the Al-loaded organic phase with acid solution to separate aluminum from the ferrophosphorus waste; and collecting the stripped organic phase for recycling.

[0027] Among them, for the extraction of step (2), single-stage extraction or multi-stage extraction can be used. Single-stage extraction is to extract the leaching solution once to obtain the organic phase and the extract; multi-stage extraction is to extract the raffinate obtained after the leaching solution is extracted again, and the cycle is repeated until the target requirement is achieved, for example Figure 1 The number of stages of multi-stage extraction in the process can be set. Similarly, single-stage or multi-stage stripping can be achieved for stripping.

[0028] Example 1

[0029] The method for separating aluminum impurities from the ferrophosphorus waste leachate of Example 1 comprises the following steps:

[0030] (1) The lithium iron phosphate battery powder waste was mixed with water at a volume ratio of 1:1 for 45 minutes to obtain a slurry; the pH of the slurry was adjusted to 1.7 with concentrated sulfuric acid, and 0.5 mol / L ascorbic acid was added to carry out acid leaching for 30 minutes. After the reaction was completed, the lithium iron phosphate battery powder leachate was obtained by filtering.

[0031] (2) Neodecanoic acid, di(2-ethylhexyl)phosphoric acid and sulfonated kerosene are mixed in a volume ratio of 1:2:7 to form a synergistic extractant which is added to a continuous extraction tank as a light phase, and the leachate is added as a heavy phase in a ratio of O / A=1:1 for extraction.

[0032] (3) The pH of the extraction system was adjusted to 2 using 2 mol / L liquid alkali, and the extraction was carried out by stirring. After extraction and phase separation, an organic phase loaded with Al and a raffinate containing Fe were obtained.

[0033] (4) Collect the organic phase loaded with Al and mix it with water in a volume ratio of 2:1 for washing. The washed organic phase is treated with 6 mol H + The sulfuric acid is stripped according to O / A=1:3, and the organic phase after stripping is collected for subsequent recycling.

[0034] Example 2

[0035] The method for separating aluminum impurities from the ferrophosphorus waste leachate of Example 2 comprises the following steps:

[0036] (1) The lithium iron phosphate battery powder waste was mixed with water at a volume ratio of 1:2 for 60 minutes to obtain a slurry; the pH of the slurry was adjusted to 2 with concentrated sulfuric acid, and 0.05 mol / L sodium bisulfite was added to perform acid leaching for 50 minutes. After the reaction was completed, the battery powder leachate was filtered to obtain the battery powder leachate.

[0037] (2) Hydroxyacetic acid, 2-ethylhexyl mono(2-ethylhexyl) phosphate and light white oil are mixed in a volume ratio of 1:0.5:3.5 to form a synergistic extractant which is added to a continuous extraction tank as a light phase, and an leaching solution is added as a heavy phase in a ratio of O / A=1:2 for extraction.

[0038] (3) The pH of the extraction system was adjusted to 2.2 using 2.5 mol / L liquid alkali, and the extraction was carried out by stirring. After extraction and phase separation, an organic phase loaded with Al and a raffinate containing Fe were obtained.

[0039] (4) Collect the organic phase loaded with Al and mix it with water in a volume ratio of 2:1 for washing. The washed organic phase is treated with 9 mol H + The sulfuric acid is stripped according to O / A=1:2, and the organic phase after stripping is collected for subsequent recycling.

[0040] Example 3

[0041] The method for separating aluminum impurities from the ferrophosphorus waste leachate of Example 3 comprises the following steps:

[0042] (1) The lithium iron phosphate battery powder waste was mixed with water at a volume ratio of 1:3 for 75 minutes to obtain a slurry; the pH of the slurry was adjusted to 2.2 with concentrated sulfuric acid, and 1 mol / L of ammonium bisulfite was added to perform acid leaching for 70 minutes. After the reaction was completed, the lithium iron phosphate battery powder leachate was obtained by filtering.

[0043] (2) Neodecanoic acid, dodecyl phosphate monoester and 260# solvent oil were mixed in a volume ratio of 1:1:3 to form a synergistic extractant, which was added to a continuous extraction tank as a light phase, and the leachate was added as a heavy phase in a ratio of O / A=1:3 for extraction.

[0044] (3) The pH of the extraction system was adjusted to 2.5 using 2.5 mol / L liquid alkali, and the extraction was carried out by stirring. After extraction and phase separation, an organic phase loaded with Al and a raffinate containing Fe were obtained.

[0045] (4) Collect the organic phase loaded with Al and mix it with water in a volume ratio of 2:1 for washing. The washed organic phase is washed with 12 mol H + The sulfuric acid is stripped according to O / A=1:1, and the organic phase after stripping is collected for subsequent recycling.

[0046] Comparative Example 1

[0047] The basic steps of Comparative Example 1 are the same as those of Example 1, except that no neodecanoic acid is added to the extract.

[0048] Comparative Example 2

[0049] The basic steps of Comparative Example 2 are the same as those of Example 1, except that no di(2-ethylhexyl)phosphoric acid is added to the extract.

[0050] Performance Testing

[0051] ICP was used to test the aluminum content in the leachate, raffinate and strip raffinate, and Fe in the Al-containing organic liquid was detected. The results are shown in Tables 1 and 2. The multi-level reference in the table below was 6 levels.

[0052] Table 1 Test results of Example 1 to Example 3, Comparative Example 1 and Comparative Example 2 (A1)

[0053] Example Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Stock solution (g / L) 1.903 1.86 1.798 1.843 1.824 Raffinate (g / L) 0.288 0.356 0.34 0.366 1.271 Multi-stage raffinate (g / L) 0.0181 0.0116 0.0109 0.1973 0.8891 Single stage extraction rate 84.87％ 80.86％ 81.09％ 80.14％ 30.32％ Multi-stage extraction rate 99.05％ 99.38％ 99.39％ 89.29％ 51.26％ Stripping rate 98.89％ 99.14％ 99.18％ 17.60％ 98.01％

[0054] Table 2 Fe content of organic phase loaded with Al

[0055] Example Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Stock solution (g / L) 103.9 105.8 101.2 102.3 104.1 Raffinate (g / L) 94.8 96.9 92.3 86.3 92.1 Multi-stage raffinate (g / L) 87.6 89.4 86.6 75.3 82.9 Al-loaded organic phase 8.76％ 8.41％ 8.79％ 15.64％ 11.53％ Multi-stage Al-loaded organic phase 15.69％ 15.50％ 14.43％ 26.39％ 20.37％

[0056] It can be seen from Tables 1 and 2 that the extraction process of the present invention can increase the extraction rate of aluminum to more than 99%; and at the same time reduce the content of Fe in the extraction phase to less than 9%, that is, it achieves effective separation of iron and aluminum, and reduces the loss of iron in the recovery of ferrophosphorus waste.

[0057] In order to further demonstrate the importance of the reaction conditions of the extraction method of the present invention, the present invention carried out corresponding parallel tests for key parameters, and the specific setting of the parallel tests is as follows.

[0058] Parallel test

[0059] The basic steps were the same as those in Example 2, except that the pH conditions in step (3) were 0.5, 1, 2.2, 3 and 3.5, respectively. The results obtained are shown in Tables 3 and 4 below.

[0060] Table 3 Test results of parallel tests (A1)

[0061] Experimental Group pH=0.5 pH = 1 pH = 2.2 pH = 3 pH=3.5 Stock solution (g / L) 1.86 1.87 1.86 1.85 1.86 Raffinate (g / L) 0.514 0.379 0.356 0.348 0.346 Multi-stage raffinate (g / L) 0.135 0.0163 0.0116 0.0104 0.0085 Single stage extraction rate 72.37％ 79.73％ 80.86％ 81.19％ 81.4％ Multi-stage extraction rate 92.74％ 99.13％ 99.38％ 99.44％ 99.54％ Stripping rate 98.55％ 98.96％ 99.14％ 99.27％ 99.33％

[0062] Table 4 Fe content of Al-loaded organic phase

[0063] Example pH = 0.5 pH = 1 pH = 2.2 pH = 3 pH=3.5 Stock solution (g / L) 105.3 104.6 105.8 105.7 104.9 Raffinate (g / L) 96.74 95.83 96.9 96.11 91.15 Multi-stage raffinate (g / L) 90.36 89.4 89.4 88.4 74.75 Al-loaded organic phase 8.13％ 8.38％ 8.41％ 9.07％ 13.11％ Multi-stage Al-loaded organic phase 14.19％ 14.53％ 15.50％ 16.37％ 28.74％

[0064] Combining Table 3 and Table 4, it can be seen that based on the leaching conditions and specific extractants of the present invention, sufficient extraction of Al can be achieved under pH conditions of 1-3, and the entry of Fe into the extraction phase is effectively reduced, thereby achieving sufficient separation of iron and aluminum.

[0065] Comparative Example 3

[0066] The basic steps are the same as those in Example 1, except that no reducing agent is introduced in step (1). The results obtained are shown in Tables 5 and 6 below.

[0067] Table 5 Test results of Example 1 and Comparative Example 3 (A1)

[0068]

[0069]

[0070] Table 6 Fe content of Al-loaded organic phase in Example 1 and Comparative Example 3

[0071] Example Example 1 Comparative Example 3 Stock solution (g / L) 103.9 104.7 Raffinate (g / L) 94.8 85.35 Multi-stage raffinate (g / L) 87.6 65.4 Al-loaded organic phase 8.76％ 18.48％ Multi-stage Al-loaded organic phase 15.69％ 37.54％

[0072] Combining Tables 5 and 6, it can be seen that when the reducing agent is not introduced during leaching, trivalent iron is preferentially extracted during extraction, thereby reducing the extraction rate of Al; and at the same time, the iron content in the extraction phase increases, increasing the loss of iron and making it difficult to separate iron and aluminum.

[0073] In addition to the above embodiments, in the method for extracting and separating aluminum from ferrophosphorus waste leachate of the present invention, the volume ratio of the carboxylic acid extractant and the acidic phosphorus extractant is within the range of 1:(0.5-8):(3-10) of the present invention, during acid leaching, the volume ratio of ferrophosphorus waste to water is within the range of 1:(1-5) of the present invention, the acidity of the acid solution during stripping is within the range of 2-12 mol H+ of the present invention, and the volume ratio of the organic phase loaded with Al to the acid solution is within the range of 1:(1-6) of the present invention, and similar technical effects can be achieved. Therefore, the embodiments are no longer listed one by one.

Claims

1. A method for extracting and separating aluminum from ferrophosphorus waste leachate, characterized in that: The steps include: (1) mixing ferrophosphorus waste with water to prepare pulp, acid leaching is performed at a pH of 1.5-2.5 and a reducing agent is added to obtain a leachate; (2) after diluting the carboxylic acid extractant and the acidic phosphorus extractant, extracting the above-mentioned leachate at a pH of 1-3 to obtain an organic phase loaded with Al and a raffinate containing Fe, respectively; (3) Collecting the Al-loaded organic phase and mixing it with water for washing; stripping the Al-loaded organic phase with acid solution to separate aluminum from the ferrophosphorus waste; and collecting the stripped organic phase for recycling.

2. The method for extracting and separating aluminum from ferrophosphorus waste leachate according to claim 1, characterized in that: In step (1), the volume ratio of the ferrophosphorus waste to water is 1:(1-5).

3. The method for extracting and separating aluminum from ferrophosphorus waste leachate according to claim 1, characterized in that: In step (1), the acid solution used for acid leaching is concentrated sulfuric acid, concentrated hydrochloric acid or concentrated nitric acid, and the acid leaching time is 20-90 minutes.

4. The method for extracting and separating aluminum from ferrophosphorus waste leachate according to claim 1, characterized in that: In step (1), the reducing agent is one or more of ascorbic acid, sodium bisulfite, ammonium bisulfite, sodium sulfite, and ammonium sulfite, and the amount of the reducing agent added is 0.05-1 mol / L.

5. The method for extracting and separating aluminum from ferrophosphorus waste leachate according to claim 1, characterized in that: In step (2), the dilution of the carboxylic acid extractant and the acidic phosphorus extractant is performed by mixing the carboxylic acid extractant, the acidic phosphorus extractant and the diluent in a volume ratio of 1:(0.5-8):(3-10).

6. The method for extracting and separating aluminum from ferrophosphorus waste leachate according to claim 5, characterized in that: The carboxylic acid extractant includes at least one of versatic 10, versatic 911, oxyacetic acid, bromolauric acid or neodecanoic acid.

7. The method for extracting and separating aluminum from ferrophosphorus waste leachate according to claim 5, characterized in that: The acidic phosphorus extractant includes one of di(2-ethylhexyl)phosphoric acid, 2-ethylhexyl phosphate mono(2-ethylhexyl) ester, dodecyl phosphate monoester or di(2-ethylhexyl) phosphinic acid.

8. The method for extracting and separating aluminum from ferrophosphorus waste leachate according to claim 5, characterized in that: The diluent includes at least one of sulfonated kerosene, 200# solvent oil, 260# solvent oil or light white oil.

9. The method for extracting and separating aluminum from ferrophosphorus waste leachate according to claim 1, characterized in that: In step (5), the acidity of the acid solution is 2-12 mol H + The volume ratio of the organic phase loaded with Al to the acid solution is 1:(1-6).

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