Method for extracting and removing metal impurities from raffinate acid

Abstract

The invention provides a method for extracting and removing metal impurities from raffinate acid, which comprises the following steps of: a) standing the raffinate acid and separating to obtain supernatant liquid; b) mixing the supernatant liquid obtained in the step a) with an extracting agent, extracting, standing and separating to obtain raffinate acid from which metal impurities are extracted and removed; the extraction agent is trioctyl amine carboxylate. Compared with the prior art, the method has the advantages that the specific extraction agent is selected and matched with the specific process steps, and the overall better interaction is realized, so that the main metal impurities are extracted and removed from the raffinate acid by utilizing the trioctylamine carboxylate, and the concentration of the metal salt in the raffinate acid can be greatly reduced; and finally, the content of metal salt impurities in an extraction oil phase during phosphoric acid extraction is reduced, so that the purity of wet-process phosphoric acid is improved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical industry, and more specifically to a method for extracting and removing metal impurities from raffinate acid. Background Art

[0002] With the development of my country's phosphate fertilizer industry, phosphate rock with a content of more than 30% is becoming increasingly scarce. The Ministry of Land and Resources has listed phosphate rock as one of the 20 minerals that cannot meet the requirements of national economic development after 2010. Guizhou Province is a province rich in phosphorus resources, and the phosphorus chemical industry plays an important role in economic development.

[0003] At present, the industrial preparation of phosphoric acid mainly includes thermal method and wet method; among them, the wet method has low cost and has become the main method for phosphoric acid production. However, in the process of preparing phosphoric acid by this method, a large amount of raffinate acid is produced, which contains a large amount of phosphorus and metal salts. If it is not used, it will not only cause a waste of phosphorus resources, but also produce a large amount of industrial waste liquid, which brings great environmental problems to production. Therefore, it is urgent to remove impurities from the raffinate acid and reduce the metal (sesquioxide) content therein so that the phosphorus resources therein can be recycled. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a method for extracting and removing metal impurities from raffinate acid, using trioctylamine carboxylate as an extractant to extract and separate metal salts in the raffinate acid, which can significantly reduce the concentration of metal salts in the raffinate acid, and ultimately reduce the content of metal salt impurities in the extracted oil phase during phosphoric acid extraction, thereby improving the purity of wet-process phosphoric acid.

[0005] The present invention provides a method for extracting and removing metal impurities from raffinate acid, comprising the following steps:

[0006] a) allowing the raffinate to stand for separation to obtain a supernatant;

[0007] b) mixing the supernatant obtained in step a) with an extractant, performing extraction, and obtaining a raffinate acid after metal impurities have been removed by extraction after standing and separation;

[0008] The extractant is trioctylamine carboxylate.

[0009] Preferably, the standing time in step a) is 20 h to 30 h.

[0010] Preferably, in the supernatant in step a), the content of P2O5 is 25wt% to 47wt%, the content of iron oxide in the sesquioxide is 0.2wt% to 1.5wt%, the content of magnesium oxide is 1wt% to 2.5wt%, the content of aluminum oxide is 1wt% to 3wt%, and the content of calcium oxide is 0.4wt% to 0.9wt%.

[0011] Preferably, the trioctylamine carboxylate in step b) is selected from one or more of trioctylamine caproate, trioctylamine heptanoate, trioctylamine octanoate and trioctylamine nonanoate.

[0012] Preferably, the trioctylamine carboxylate is trioctylamine nonanoate, trioctylamine caproate, trioctylamine caprylate or trioctylamine heptanoate.

[0013] Preferably, the water-to-oil ratio of the extraction in step b) is 1:(1-6).

[0014] Preferably, the extraction temperature in step b) is 20°C to 60°C.

[0015] Preferably, the extraction time in step b) is 10 min to 40 min.

[0016] Preferably, the main ions of the metal impurities in step b) include Al 3+ , Ca 2+ Mg 2+ , Fe 3+ One or more of .

[0017] Preferably, the main ions of the metal impurities are Al 3+ , Ca 2+ Mg 2+ and Fe 3+ .

[0018] The present invention provides a method for extracting and removing metal impurities from raffinate acid, comprising the following steps: a) separating the raffinate acid after standing to obtain a supernatant; b) mixing the supernatant obtained in step a) with an extractant, extracting, standing to separate, and obtaining the raffinate acid after metal impurities have been extracted; the extractant is trioctylamine carboxylate. Compared with the prior art, the present invention selects a specific extractant and a specific process step to achieve overall better interaction, thereby realizing the extraction and removal of major metal impurities from the raffinate acid by trioctylamine carboxylate, and can significantly reduce the concentration of metal salts in the raffinate acid, and finally reduce the content of metal salt impurities in the extracted oil phase during phosphoric acid extraction, thereby improving the purity of wet-process phosphoric acid.

[0019] At the same time, the method provided by the present invention has simple process, mild conditions, easy control, low cost and broad application prospects. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The present invention provides a method for extracting and removing metal impurities from raffinate acid, comprising the following steps:

[0022] a) allowing the raffinate to stand for separation to obtain a supernatant;

[0023] b) mixing the supernatant obtained in step a) with an extractant, performing extraction, and obtaining a raffinate acid after metal impurities have been removed by extraction after standing and separation;

[0024] The extractant is trioctylamine carboxylate.

[0025] The invention firstly allows the raffinate to stand for separation to obtain a supernatant.

[0026] In the present invention, the raffinate acid is produced in the process of preparing phosphoric acid by a wet method well known to those skilled in the art, and the present invention has no special limitation on its source.

[0027] In the present invention, the standing time is preferably 20h to 30h, more preferably 24h. In the present invention, since the viscosity of the raffinate sample is too high, it is difficult to measure the concentration before standing. Therefore, the sample is allowed to stand for a period of time and then the supernatant is obtained by solid-liquid separation; and the precipitate can also be removed at the same time.

[0028] In the present invention, in the supernatant, the content of P2O5 is preferably 25wt% to 47wt%, more preferably 26wt% to 46wt%, the content of iron oxide in the main metal sesquioxide is preferably 0.2wt% to 1.5wt%, more preferably 0.4wt% to 0.6wt%, the content of magnesium oxide is preferably 1wt% to 2.5wt%, more preferably 1.2wt% to 1.5wt%, the content of aluminum oxide is preferably 1wt% to 3wt%, more preferably 2.1wt% to 2.6wt%, and the content of calcium oxide is preferably 0.4wt% to 0.9wt%, more preferably 0.60wt% to 0.85wt%.

[0029] After obtaining the supernatant, the present invention mixes the supernatant with an extractant to perform extraction, and then, after standing and separating, obtains the raffinate acid after the metal impurities have been removed by extraction.

[0030] In the present invention, the extractant is trioctylamine carboxylate (there is no report on the use of carboxylic acid alkylamine extractants for wet-process phosphoric acid and raffinate purification); the trioctylamine carboxylate is preferably selected from one or more of trioctylamine caproate, trioctylamine heptanoate, trioctylamine octanoate, and trioctylamine nonanoate, and more preferably trioctylamine nonanoate, trioctylamine caproate, trioctylamine octanoate, or trioctylamine heptanoate. The present invention has no special restrictions on the source of the extractant, and commercially available products or self-made products (synthesized from trioctylamine and carboxylic acid) known to those skilled in the art can be used.

[0031] The inventors have found that trioctylamine carboxylate has good extraction performance for metal salts. In view of the problem of high metal impurity content in raffinate acid, if an extractant with good separation effect on metal salts can be obtained and the metal salt content can be reduced, it will be beneficial to the extraction of phosphorus and improve the purity of wet-process phosphoric acid. Therefore, if trioctylamine carboxylate can be used as an extractant with good extraction performance for major metal ions such as calcium, magnesium, iron, and aluminum in the raffinate acid system, the metal ion content in the system can be reduced, which will be beneficial to improve the purity of wet-process phosphoric acid and will be of great significance to improving the economic benefits of the phosphoric acid industry.

[0032] In the present invention, the water-to-oil ratio of the extraction is preferably 1:(1-6), more preferably 1:(2-3).

[0033] In the present invention, the extraction temperature is preferably 20°C to 60°C, more preferably 30°C to 40°C.

[0034] In the present invention, the extraction time is preferably 10 min to 40 min, more preferably 25 min to 35 min.

[0035] The present invention uses trioctylamine carboxylate as an extractant to extract and separate metal ion impurities in the raffinate acid to obtain the raffinate acid after the metal impurities are removed by extraction; the main ions of the metal impurities preferably include Al 3+ , Ca 2+ Mg 2+ , Fe 3+ One or more of, more preferably Al 3+ , Ca 2+ Mg 2+ and Fe 3+ .

[0036] In the present invention, in addition to the purified raffinate acid, the organic phase after extraction is further processed and recovered by static separation, and the present invention has no special restrictions on this. The present invention obtains the extraction phase and the raffinate phase respectively by the above static separation, and the metal impurities in the wet-process phosphoric acid raffinate acid enter the extraction phase, and the extraction phase is separated and purified to obtain various metal salts; the raffinate phase can be further extracted with an extractant such as an organic solvent to obtain a high-purity phosphoric acid product.

[0037] The invention adopts hydrophobic trioctylamine carboxylate with good solubility for metal salt to extract raffinate acid, and the metal salt content in the raffinate acid is greatly reduced after the treatment, thereby creating favorable conditions for the subsequent reuse of the raffinate acid and further preparation of industrial-grade phosphoric acid; the invention reduces the metal impurity content in the raffinate acid through extraction, directly or indirectly reduces the metal impurity concentration in the wet-process phosphoric acid production system, and is helpful to improve the purity of the wet-process phosphoric acid.

[0038] The present invention provides a method for extracting and removing metal impurities from raffinate acid, comprising the following steps: a) separating the raffinate acid after standing to obtain a supernatant; b) mixing the supernatant obtained in step a) with an extractant, extracting, standing to separate, and obtaining the raffinate acid after metal impurities have been extracted; the extractant is trioctylamine carboxylate. Compared with the prior art, the present invention selects a specific extractant and a specific process step to achieve overall better interaction, thereby realizing the extraction and removal of major metal impurities from the raffinate acid by trioctylamine carboxylate, and can significantly reduce the concentration of metal salts in the raffinate acid, and finally reduce the content of metal salt impurities in the extracted oil phase during phosphoric acid extraction, thereby improving the purity of wet-process phosphoric acid.

[0039] At the same time, the method provided by the present invention has simple process, mild conditions, easy control, low cost and broad application prospects.

[0040] In order to further illustrate the present invention, the following examples are provided for detailed description.

[0041] Example 1

[0042] Take the residual acid sample, let it stand for 24 hours and take the supernatant. Analysis and detection show that the content of P2O5 is 26.36wt%, the content of iron oxide in the sesquioxide is 0.42wt%, the content of magnesium oxide is 1.28wt%, the content of aluminum oxide is 2.14wt%, and the content of calcium oxide is 0.66wt%. The supernatant is extracted with trioctylamine nonanoate as the extractant, and the extraction conditions are: water-oil ratio 1:2, temperature 35℃, and time 30min.

[0043] Measured Al 3+ , Ca 2+ Mg 2+ and Fe 3+The extraction rates were 19.40%, 86.91%, 25.79% and 24.39% respectively.

[0044] Example 2

[0045] Take the residual acid sample, let it stand for 24 hours and take the supernatant. Analysis and detection show that the content of P2O5 is 32.31wt%, the content of iron oxide in the sesquioxide is 0.45wt%, the content of magnesium oxide is 1.45wt%, the content of aluminum oxide is 2.57wt%, and the content of calcium oxide is 0.83wt%. The supernatant is extracted with trioctylamine hexanoate as the extractant, and the extraction conditions are: water-oil ratio 1:2, temperature 35℃, and time 30min.

[0046] Measured Al 3+ , Ca 2+ Mg 2+ and Fe 3+ The extraction rates were 16.68%, 67.66%, 23.07% and 19.00% respectively.

[0047] Example 3

[0048] Take the residual acid sample, let it stand for 24 hours and take the supernatant. Analysis and detection show that the content of P2O5 is 45.25wt%, the content of iron oxide in the sesquioxide is 0.49wt%, the content of magnesium oxide is 1.48wt%, the content of aluminum oxide is 2.36wt%, and the content of calcium oxide is 0.66wt%. The supernatant is extracted with trioctylamine caprylate as the extractant, and the extraction conditions are: water-oil ratio 1:2, temperature 35℃, and time 30min.

[0049] Measured Al 3+ , Ca 2+ Mg 2+ and Fe 3+ The extraction rates were 13.94%, 60.50%, 20.33% and 16.58% respectively.

[0050] Example 4

[0051] Take the residual acid sample, let it stand for 24 hours and take the supernatant. Analysis and detection show that the content of P2O5 is 44.9wt%, the content of iron oxide in the sesquioxide is 0.51wt%, the content of magnesium oxide is 1.38wt%, the content of aluminum oxide is 2.16wt%, and the content of calcium oxide is 0.61wt%. The supernatant is extracted with trioctylamine heptanoate as the extractant, and the extraction conditions are: water-oil ratio 1:2, temperature 35℃, and time 30min.

[0052] Measured Al 3+ , Ca 2+ Mg 2+ and Fe3+ The extraction rates were 12.51%, 63.28%, 19.24% and 13.36% respectively.

[0053] See Table 1 below for relevant data.

[0054] Table 1 Performance data of extractants for removing metal ions from raffinate acid

[0055]

[0056] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for extracting and removing metal impurities from raffinate acid, characterized in that: The following steps are involved: a) allowing the raffinate to stand for separation to obtain a supernatant; b) mixing the supernatant obtained in step a) with an extractant, performing extraction, and obtaining a raffinate acid after metal impurities have been removed by extraction after standing and separation; The extractant is trioctylamine carboxylate.

2. The method for extracting and removing metal impurities from raffinate according to claim 1, characterized in that: The standing time in step a) is 20 h to 30 h.

3. The method for extracting and removing metal impurities from raffinate according to claim 1, characterized in that: In the supernatant in step a), the content of P2O5 is 25wt% to 47wt%, the content of iron oxide in the sesquioxide is 0.2wt% to 1.5wt%, the content of magnesium oxide is 1wt% to 2.5wt%, the content of aluminum oxide is 1wt% to 3wt%, and the content of calcium oxide is 0.4wt% to 0.9wt%.

4. The method for extracting and removing metal impurities from raffinate according to claim 1, characterized in that: The trioctylamine carboxylate in step b) is selected from one or more of trioctylamine caproate, trioctylamine heptanoate, trioctylamine octanoate and trioctylamine nonanoate.

5. The method for extracting and removing metal impurities from raffinate according to claim 4, characterized in that: The trioctylamine carboxylate is trioctylamine nonanoate, trioctylamine caproate, trioctylamine caprylate or trioctylamine heptanoate.

6. The method for extracting and removing metal impurities from raffinate according to claim 1, characterized in that: The water-to-oil ratio of the extraction in step b) is 1:(1-6).

7. The method for extracting and removing metal impurities from raffinate according to claim 1, characterized in that: The extraction temperature in step b) is 20°C to 60°C.

8. The method for extracting and removing metal impurities from raffinate according to claim 1, characterized in that: The extraction time in step b) is 10 min to 40 min.

9. The method for extracting and removing metal impurities from raffinate according to claim 1, characterized in that: The main ions of the metal impurities in step b) include Al 3+ , Ca 2+ Mg 2+ , Fe 3+ One or more of .

10. The method for extracting and removing metal impurities from raffinate according to claim 9, characterized in that: The main ions of the metal impurities are Al 3+ , Ca 2+ Mg 2+ and Fe 3+ .

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