Method for resourceful treatment of nitric acid waste liquid

Abstract

The application belongs to the technical field of extraction and specifically relates to a nitric acid waste liquid resource treatment method, which comprises a first separation step and a second separation step. The first separation step adopts a four-stage or more cross-flow extraction process, single-stage extraction obtains loaded organic phase, and the raffinate obtained by the last extraction is used. The loaded organic phase obtained by single-stage extraction is mixed to obtain loaded organic phase I, the loaded organic phase I is back-extracted by using back-extractant I, and back-extraction liquid I is obtained. In the second separation step, the pH value of the raffinate is adjusted to 2.5-3 by using an alkaline substance, the raffinate is extracted by using a phosphoric acid-based extractant, loaded organic phase II is obtained, and the loaded organic phase II is stepwise back-extracted by using back-extractant and back-extractant III, back-extraction liquid II and back-extraction liquid III are obtained. In this way, iron is enriched in back-extraction liquid I and back-extraction liquid III, and copper is enriched in back-extraction liquid II, so that the separation of copper and iron from the nitric acid waste liquid is realized, the separation of copper and iron is further realized, and the resource utilization of the nitric acid waste liquid is realized.

Description

Technical Field

[0001] This invention belongs to the field of extraction technology, specifically relating to a method for the resource-based treatment of nitric acid waste liquid. Background Technology

[0002] In some industrial production processes, dirt and metal oxides are generated on equipment, which are mainly cleaned using dilute acids, including hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid. In certain specific production environments, some dirt and metal oxides require nitric acid cleaning to completely dissolve. This is because nitric acid itself has oxidizing properties, which greatly enhances the cleaning effect. Furthermore, most nitrates are water-soluble, ensuring a high degree of cleanliness. In addition, equipment cleaned with nitric acid does not carry the risk of pitting corrosion like that cleaned with hydrochloric acid; moreover, nitric acid is particularly effective at removing copper rust. Therefore, in industrial production, nitric acid is mainly used for cleaning stainless steel, carbon steel, brass, copper, and carbon steel-stainless steel equipment, as well as brass-carbon steel welded combinations. Moreover, nitric acid is characterized by its speed and efficiency in removing scale and rust, removing iron oxide scale and rust quickly, and has low corrosiveness to carbon steel, stainless steel, and copper. Therefore, nitric acid has a very broad application prospect in specific environments.

[0003] However, nitric acid pickling wastewater is highly oxidizing and acidic, exhibiting strong corrosiveness. Furthermore, it contains a large amount of metal ions, including some valuable metals. Direct discharge not only wastes resources but also pollutes the environment, directly harming plant and animal health. Currently, the main treatment methods for nitric acid pickling wastewater include high-temperature roasting, neutralization precipitation, membrane filtration, solvent extraction, and vacuum distillation, with different methods selected based on the different components in the wastewater. High-temperature roasting requires significant energy consumption, resulting in excessively high recovery costs and poor economic efficiency compared to nitric acid wastewater with low levels of valuable metals, while also generating substantial pollution. Neutralization precipitation requires the addition of large amounts of alkaline substances, leading to high costs and the generation of large amounts of waste salt residue, increasing subsequent treatment costs. Membrane filtration and vacuum distillation require sophisticated equipment and have high treatment costs. Solvent extraction has specific requirements for the extractant and is difficult to apply universally.

[0004] For waste liquid containing high iron, low copper, and high nitric acid, commercially available copper-iron extractants cannot extract copper in a high-acid system; however, iron in a high-acid system can be preferentially extracted by some extractants. Therefore, a stepwise separation method may be adopted for waste liquid containing high iron, low copper, and high nitric acid to first achieve preliminary separation of copper and iron, and then achieve complete separation of copper and iron as well as complete separation of copper, iron, and nitric acid waste liquid through other methods. However, how to carry out stepwise separation to achieve the resource utilization of waste liquid containing high iron, low copper, and high nitric acid is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] The present invention aims to provide a method for the resource-based treatment of nitric acid waste liquid, in order to achieve the separation of copper, iron and nitric acid in high-iron, low-copper and high-nitric acid waste liquid through stepwise separation, thereby realizing the resource utilization of high-iron, low-copper and high-nitric acid waste liquid.

[0006] To achieve the above objectives, the present invention provides a method for the resource-based treatment of nitric acid waste liquid, comprising:

[0007] First separation step:

[0008] 1) N-stage extraction: Divide the extracted organic phase into N equal parts, where N≥4; mix 1 part of the extracted organic phase with nitric acid waste liquid containing high iron and low copper, and extract to obtain the first loaded organic phase and the first raffinate; mix the first raffinate with a new 1 part of the extracted organic phase, and extract to obtain the second loaded organic phase and the second raffinate; and so on, mixing the raffinate obtained from the previous stage extraction with a new 1 part of the extracted organic phase until all N parts of the extracted organic phase are used up, to obtain the Nth loaded organic phase and the Nth raffinate.

[0009] 2) Back-extraction: After uniformly mixing the first loaded organic phase, the second loaded organic phase, ... the Nth loaded organic phase, the loaded organic phase I is obtained. The loaded organic phase I is mixed with the back-extraction agent I, and back-extraction is performed to obtain the lean organic phase I and the back-extraction solution I.

[0010] Second separation step:

[0011] 1) Extraction: Adjust the pH of the Nth raffinate to 2.5-3 using an alkaline substance, and then extract the alkaline-treated Nth raffinate using a phosphoric acid extractant to obtain the loaded organic phase II and raffinate II.

[0012] 2) Back-extraction: Back-extracting agent II and back-extracting agent III are used to back-extract the loaded organic phase II in steps to obtain organic-poor phase II and back-extraction solution II and back-extraction solution III.

[0013] The working principle and beneficial effects of this scheme are as follows: In this scheme, the copper and iron content in the nitric acid waste liquid is basically low in copper and high in iron, with iron existing in the form of ferric ions. In addition, there are a large amount of nitrate ions and a small amount of other metal ions. Since the acidity of the nitric acid waste liquid and the presence of iron ions have a significant impact on the resource recovery of valuable metals, this scheme uses an extraction + neutralization treatment method to separate copper and iron in the high nitric acid system stepwise, reducing the copper and iron content in the waste liquid to below 0.0001 g / L, thereby achieving the resource utilization of the nitric acid waste liquid.

[0014] The main issue is that precipitation occurs when alkaline substances are added to the high-speed iron and high-nitric acid system to adjust the pH value, affecting metal separation and purification. In this scheme, the first separation step directly uses extraction to extract some of the iron from the nitric acid waste liquid, reducing the metal content in the nitric acid waste liquid and achieving preliminary separation of copper and iron, thus avoiding precipitation in the nitric acid waste liquid. The Nth raffinate obtained from the first separation step is then further separated by adding alkaline substances to the Nth raffinate to adjust its pH value, using the phosphoric acid extractant P204 to co-extract copper and iron, and then back-extracting the loaded organic phase II in steps to achieve complete separation of copper and iron, as well as complete separation of copper and iron from the nitric acid waste liquid.

[0015] In summary, this solution effectively reduces energy consumption and alkalizes the treatment process through stepwise separation and extraction. The equipment used in the process is all conventional extraction equipment, which is low in cost, simple to operate, and has a controllable processing scale, making it suitable for the separation of copper-containing nitric acid waste liquid.

[0016] Optionally, in the first separation step, the extraction of the organic phase includes a diluent and a phosphoric acid extractant, P204.

[0017] In this scheme, the phosphoric acid extractant P204 can extract iron ions in a high nitric acid system.

[0018] Optionally, in the first separation step, the volume fraction of the phosphoric acid extractant P204 in the extracted organic phase is 20-30%.

[0019] In this scheme, the extraction effect of phosphate extractant P204 is good when the volume fraction is 20-30% for iron ions in high nitric acid system.

[0020] Optionally, in the first separation step, the volume ratio of one part of the extracted organic phase to the nitric acid waste liquid containing high iron and low copper is 4 to 3:1, and the single-stage extraction time is at least 3 minutes.

[0021] The O / A ratio and extraction time in this scheme can ensure that iron ions are fully extracted.

[0022] Optionally, in the first separation step, the volume ratio of the supported organic phase I to the stripping agent I is 1:1 to 1.5, the stripping time is at least 3 minutes, and the stripping agent I is an HCl solution.

[0023] The O / A ratio and back-extraction time in this scheme can ensure that iron ions are fully back-extracted.

[0024] Optionally, in the first separation step, there is also a washing process between the N-stage extraction and back-extraction: the first loaded organic phase, the second loaded organic phase... the Nth loaded organic phase are mixed evenly and then mixed with wash water, and the loaded organic phase I and wastewater are obtained after washing.

[0025] In this scheme, washing water is used to wash the supported organic phase I to remove the entrainment of the supported organic phase I.

[0026] Optionally, in the first separation step, the volume ratio of the loaded organic phase I to the washing water is 1:1 to 2, and the washing time is at least 3 minutes, with the washing water being pure water.

[0027] The O / A ratio and washing time in this scheme can ensure that the entrainment of the extracted organic phase is completely eluted, and the wastewater after washing can be returned to the feed liquid (nitric acid waste liquid) after multiple cycles.

[0028] Optionally, in the second separation step, the phosphoric acid extractant is P2O4, the volume fraction of the phosphoric acid extractant is 10-15%, and the volume ratio of the phosphoric acid extractant to the Nth raffinate is 2-1:1.

[0029] The O / A ratio in this scheme ensures the co-extraction effect of the phosphate extractant P204 on copper and iron.

[0030] Optionally, in the second separation step, the stripping agent II is an H2SO4 solution, the stripping agent III is an HCl solution, and the volume ratio of the supported organic phase II to the stripping agent II / stripping agent III is 1 to 1.5:1.

[0031] The O / A ratio in this scheme ensures that stripping agent II fully strips copper ions and stripping agent III fully strips iron ions.

[0032] Optionally, in the second separation step, both extraction and back-extraction have at least two stages, with each stage of extraction lasting at least 3 minutes.

[0033] In this scheme, the extraction and back-extraction stages in the second separation step are limited to two or more stages, and the extraction time and back-extraction time for a single stage are limited to more than 3 minutes, which can ensure the full separation of copper and iron from nitric acid waste liquid and the full separation of copper and iron. Attached Figure Description

[0034] Figure 1 This is a schematic flowchart of a method for resource recovery treatment of nitric acid waste liquid in an embodiment of the present invention. Detailed Implementation

[0035] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0036] This invention provides a method for the resource-based treatment of nitric acid waste liquid, comprising:

[0037] First separation step:

[0038] 1) N-stage extraction: The extractable organic phase is divided into N equal parts, where N≥4; one part of the extractable organic phase is mixed with nitric acid waste liquid containing high iron and low copper, and extracted to obtain the first loaded organic phase and the first raffinate; the first raffinate is mixed with a new part of the extractable organic phase, and extracted to obtain the second loaded organic phase and the second raffinate; and so on, mixing the raffinate obtained from the previous stage extraction with a new part of the extractable organic phase until all N parts of the extractable organic phase are used up, obtaining the Nth loaded organic phase and the Nth raffinate. The extractable organic phase includes a diluent and a phosphoric acid extractant P204, with a volume fraction of 20-30% in the extractable organic phase; the volume ratio of one part of the extractable organic phase to the nitric acid waste liquid containing high iron and low copper is 4-3:1, and the single-stage extraction time is at least 3 minutes; N is preferably 4-6.

[0039] 2) Washing: The first loaded organic phase, the second loaded organic phase, ... the Nth loaded organic phase are mixed evenly and then mixed with wash water. After washing, the loaded organic phase I and wastewater are obtained. The volume ratio of the loaded organic phase I to the wash water is 1:1 to 2, and the washing time is at least 3 minutes. The wash water is pure water.

[0040] 3) Back-extraction: The supported organic phase I is mixed with back-extraction agent I, and back-extraction is performed to obtain lean organic phase I and back-extraction solution I. The volume ratio of supported organic phase I to back-extraction agent I is 1:1 to 1.5, the back-extraction time is at least 3 min, and back-extraction agent I is an HCl solution with a concentration of 6 mol / L.

[0041] Second separation step:

[0042] 1) Extraction: The pH of the Nth raffinate is adjusted to 2.5–3 using an alkaline substance, and then the alkalinized Nth raffinate is extracted with a phosphoric acid extractant to obtain the loaded organic phase II and raffinate II. The phosphoric acid extractant is P2O4, with a volume fraction of 10–15%, and the volume ratio of phosphoric acid extractant to the Nth raffinate is 2–1:1.

[0043] 2) Back-extraction: Back-extracting agent II and back-extracting agent III are used to back-extract the supported organic phase II in steps to obtain a lean organic phase II and back-extracting solution II and back-extracting solution III. Among them, back-extracting agent II is an H2SO4 solution, back-extracting agent III is an HCl solution, and the volume ratio of supported organic phase II to back-extracting agent II / back-extracting agent III is 1 to 1.5:1.

[0044] Furthermore, in the second separation step, both extraction and back-extraction have two or more stages, and the duration of each single-stage extraction and back-extraction is more than 3 minutes.

[0045] The following specific examples illustrate the present invention in detail. It should also be understood that the following examples are only for specific illustrative purposes and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0046] Example 1

[0047] In this embodiment, the composition of a certain nitric acid waste liquid to be treated is as follows: Cu 0.55g / L, Fe 139.46g / L, HNO3 15%, and the pH value of the nitric acid waste liquid is <0.

[0048] A method for resource recovery treatment of nitric acid waste liquid, the overall process of which is as follows: Figure 1 As shown, the method specifically includes the following steps:

[0049] First separation step:

[0050] 1) N-stage extraction: The organic phase to be extracted is divided into four equal parts. The organic phase includes a diluent and a phosphoric acid extractant, P204, with a volume fraction of 20%. The diluent is kerosene. One part of the organic phase is mixed with the above-mentioned nitric acid waste liquid, and extracted to obtain the first loaded organic phase and the first raffinate. The first raffinate is mixed with a new part of the organic phase to obtain the second loaded organic phase and the second raffinate. The second raffinate is mixed with a new part of the organic phase to obtain the third loaded organic phase and the third raffinate. The third raffinate is mixed with a new part of the organic phase to obtain the fourth loaded organic phase and the fourth raffinate. The ratio of each extraction stage is 4:1, and the extraction time for each stage is 3 minutes. The iron content in the fourth raffinate is 2 g / L, and the copper content is 0.55 g / L.

[0051] 2) Washing: Mix the first, second, third and fourth loaded organic phases evenly and then mix with pure water. The washing ratio is 1:1 and the washing time is 3 minutes. After washing, the loaded organic phase I and wastewater are obtained.

[0052] 3) Back-extraction: The supported organic phase I was subjected to two-stage countercurrent back-extraction using back-extraction agent I (6 mol / L HCl solution). The back-extraction ratio was 1:1, and the back-extraction time was 3 min, yielding an organic-lean phase I and back-extraction solution I (ferric chloride solution). The copper content in back-extraction solution I was below 0.0001 g / L.

[0053] In the first separation step, most of the iron in the nitric acid waste liquid is separated by a four-stage cross-flow extraction process to obtain a high-concentration ferric chloride solution, thus achieving the initial separation of copper and iron in the nitric acid waste liquid as well as the separation of iron from the nitric acid waste liquid.

[0054] Second separation step:

[0055] 1) Extraction: The pH of the fourth raffinate was adjusted to 2.5 using sodium hydroxide. Then, the alkalized fourth raffinate was extracted with a 10% (v / v) phosphoric acid extractant, P204, at an extraction ratio of 2:1 for 3 minutes, yielding an organic-loaded phase II and raffinate II. Raffinate II mainly consists of sodium nitrate and contains trace impurity ions other than copper and iron. Further processing yields the sodium nitrate product.

[0056] 2) Back-extraction: Back-extraction agent II (2 mol / L H₂SO₄ solution) and back-extraction agent III (6 mol / L HCl solution) are used for stepwise back-extraction of the loaded organic phase II. The back-extraction ratio is 1.5:1, and the back-extraction time is 3 min, yielding organic-lean phase II and back-extraction solutions II and III. Back-extraction solution II mainly consists of CuSO₄ with an iron content below 0.0008 g / L. After repeated cycles, it can be used to produce electrolytic copper. Back-extraction solution III mainly consists of FeCl₃, and after repeated cycles, it yields ferric chloride.

[0057] In the second separation step, a two-extraction, two-countercurrent extraction process is used to achieve complete separation of copper and iron in nitric acid waste liquid, thereby realizing the resource utilization of nitric acid waste liquid.

[0058] Examples 2-5 are basically the same as Example 1, except for the selection of some parameters, as detailed in Table 1.

[0059] Table 1. Parameter Selection Table for Examples 1-5

[0060]

[0061]

[0062] The degree of separation between copper and iron and nitric acid waste liquid is reflected in the amount of copper and iron in raffinate II. Complete separation of copper and iron is reflected in the amount of iron impurities in back-extraction liquid II and the amount of copper impurities in back-extraction liquid III. As shown in Table 1, the copper and iron contents in raffinate II are both below 0.0001 g / L, the iron content in back-extraction liquid II is below 0.0008 g / L, and the copper content in back-extraction liquid III is below 0.0001 g / L. It can be seen that the degree of separation between copper and iron and nitric acid waste liquid in this invention is high, and the degree of separation between copper and iron is also high. This invention can effectively treat nitric acid waste liquid for resource recovery.

[0063] Comparative Example 1

[0064] This comparative example is basically the same as Example 1, except that in the first separation step, sodium hydroxide was added to the nitric acid waste liquid to adjust its pH value from <0 to 1. During this process, the nitric acid waste liquid gradually became turbid, making direct iron extraction impossible. After filtration and separation, analysis revealed a Cu content of 0.5 g / L, resulting in a direct loss of valuable metals and failing to achieve copper-iron separation.

[0065] Comparative Example 2

[0066] This comparative example is basically the same as Example 1, except that in this comparative example, sodium hydroxide was not used to adjust the pH of the fourth raffinate in the second separation step. As a result, the iron ion content in raffinate II remains at 1-2 g / L, and the copper ion content is basically the same as that of the original nitric acid waste liquid, thus failing to achieve the separation of copper and iron, as well as the separation of copper and iron from the nitric acid waste liquid.

[0067] Comparative Example 3

[0068] This comparative example is basically the same as Example 1, except that in the second separation step, the stripping agent II is a 1 mol / L H2SO4 solution, the Cu content in stripping solution II is 0.37 g / L and the Fe content is 0.0006 g / L, and the Cu content in stripping solution III is 0.18 g / L and the Fe content is 1.0 g / L. In this comparative example, the acidity of stripping agent II is too low, which affects the stripping effect of copper in the supported organic phase II, resulting in incomplete stripping. Consequently, when using stripping agent III, the remaining copper in the supported organic phase II is stripped into stripping solution III, affecting the copper-iron separation effect.

[0069] Comparative Example 4

[0070] This comparative example is basically the same as Example 1, except that in the second separation step, the stripping agent II is a 2.5 mol / L H2SO4 solution, the Cu content in stripping solution II is 0.55 g / L and the Fe content is 0.0051 g / L, and the Cu content in stripping solution III is 0.0001 g / L and the Fe content is 0.995 g / L. In this comparative example, the excessive acidity of stripping agent II will cause iron to be stripped, affecting the purity of copper sulfate in stripping solution II and reducing the copper-iron separation effect.

[0071] In addition, when the stripping agent III is a low-concentration HCl solution, the low acidity of the stripping agent III will affect the stripping effect of the supported organic phase II, resulting in incomplete iron stripping. This will reduce the extraction capacity of the extractant in the subsequent cyclic extraction process, and ultimately affect the separation of copper and iron as well as the separation effect of copper, iron and nitric acid waste liquid.

[0072] Comparative Example 5

[0073] This comparative example is basically the same as the first separation step in Example 1, but this comparative example does not perform the second separation step. Other differences are: in this comparative example, in the first separation step, the extraction organic phase used includes a diluent and an extractant Mextral984H, and the back-extraction agent I is a 2 mol / L H2SO4 solution.

[0074] In this comparative example, the copper ion content in raffinate I was 0.55 g / L, and the iron ion content was 139.46 g / L, while no copper or iron ions were detected in back-extraction solution I. This demonstrates that Mextral984H cannot effectively extract copper and iron ions, let alone achieve copper-iron separation. Furthermore, the extractant Mextral984H underwent a significant color change, indicating severe degradation.

[0075] Comparative Example 6

[0076] This comparative example is basically the same as the first separation step in Example 1, but this comparative example does not perform the second separation step. Other differences are: in this comparative example, in the first separation step, the extraction organic phase used includes diluent (kerosene) and extractant TBP, the back-extraction agent I is pure water, and this comparative example uses five-stage cross-flow extraction.

[0077] In this comparative example, the fifth raffinate contained 0.55 g / L of copper ions and 135.72 g / L of iron ions, indicating that TBP cannot effectively separate copper and iron in a high nitric acid system.

[0078] After numerous trials, the inventors failed to find a suitable extractant to directly extract copper from nitric acid waste liquid. Therefore, they abandoned the method of separating copper ions before using phosphoric acid extractants and instead chose to extract iron ions with phosphoric acid extractants before separating copper and iron, and then separating copper, iron, and nitric acid waste liquid. Because of the high acidity of the nitric acid waste liquid, the extraction capacity of the phosphoric acid extractant P204 easily reached its limit, affecting the separation effect. Therefore, after completing the initial separation of copper and iron, the Nth raffinate was neutralized to create conditions for the second separation step. Due to the strong oxidizing properties of the nitric acid system, the selection of the extractant in the second separation step is also extremely important. During this process, the inventors also tried a large number of candidate extractants, as illustrated in Comparative Example 7.

[0079] Comparative Example 7

[0080] This comparative example is basically the same as Example 1, except that in this comparative example, the phosphoric acid extractant used in the second separation step is P507. The raffinate II contains 0.51 g / L of copper ions and 0.21 g / L of iron ions, indicating that the combined use of extractants P507 and P204 cannot achieve the separation of copper and iron from nitric acid waste liquid, nor the separation of copper and iron from nitric acid waste liquid.

[0081] In addition, the inventors also tried extractants such as P272, 292P, and 471P in the second separation step, and found that the amount of copper ions in the raffinate II was greater than 0.5 g / L and the amount of iron ions was greater than 0.2 g / L, making it impossible to effectively separate copper and iron. This indicates that under these conditions, P204 is the most suitable extractant for the entire extraction + neutralization process to separate copper and iron.

[0082] The above are merely embodiments of the present invention. The invention is not limited to the fields covered by these embodiments. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can improve and implement this solution based on the guidance provided in this application and their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness or practicality of the invention. The scope of protection claimed in this application should be determined by the content of its claims. The specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for resource-based treatment of nitric acid waste liquid, characterized in that, include: First separation step: 1) N-stage extraction: Divide the extractable organic phase into N equal parts, where N≥4; mix one part of the extractable organic phase with nitric acid waste liquid containing high iron and low copper, and extract to obtain the first loaded organic phase and the first raffinate; mix the first raffinate with a new part of the extractable organic phase, and extract to obtain the second loaded organic phase and the second raffinate; and so on, mixing the raffinate obtained from the previous stage extraction with a new part of the extractable organic phase until all N parts of the extractable organic phase are used up, to obtain the Nth loaded organic phase and the Nth raffinate; wherein, the extractable organic phase includes a diluent and a phosphoric acid extractant P2O4; 2) Back-extraction: After uniformly mixing the first loaded organic phase, the second loaded organic phase, ... the Nth loaded organic phase, the loaded organic phase I is obtained. The loaded organic phase I is mixed with the back-extraction agent I, and back-extraction is performed to obtain the lean organic phase I and the back-extraction solution I. Second separation step: 1) Extraction: Adjust the pH of the Nth raffinate to 2.5-3 using an alkaline substance, and then extract the alkaline-treated Nth raffinate using a phosphoric acid extractant to obtain the loaded organic phase II and raffinate II; 2) Back-extraction: Back-extraction agent II and back-extraction agent III are used to back-extract the loaded organic phase II in steps to obtain organic-poor phase II and back-extraction liquid II and back-extraction liquid III.

2. The method for resource-based treatment of nitric acid waste liquid according to claim 1, characterized in that, In the first separation step, the volume fraction of the phosphoric acid extractant P204 in the extracted organic phase is 20-30%.

3. The method for resource-based treatment of nitric acid waste liquid according to claim 2, characterized in that, In the first separation step, the volume ratio of one part of the extracted organic phase to the nitric acid waste liquid containing high iron and low copper is 4 to 3:1, and the single-stage extraction time is at least 3 minutes.

4. The method for resource-based treatment of nitric acid waste liquid according to claim 3, characterized in that, In the first separation step, the volume ratio of the supported organic phase I to the stripping agent I is 1:1 to 1.5, the stripping time is at least 3 minutes, and the stripping agent I is an HCl solution.

5. The method for resource-based treatment of nitric acid waste liquid according to claim 1, characterized in that, In the first separation step, there is also a washing process between the N-stage extraction and back-extraction: the first loaded organic phase, the second loaded organic phase, ... the Nth loaded organic phase are mixed evenly and then mixed with wash water. After washing, the loaded organic phase I and wastewater are obtained.

6. The method for resource-based treatment of nitric acid waste liquid according to claim 5, characterized in that, In the first separation step, the volume ratio of the loaded organic phase I to the wash water is 1:1 to 2, and the washing time is at least 3 minutes. The wash water is pure water.

7. The method for resource-based treatment of nitric acid waste liquid according to claim 1, characterized in that, In the second separation step, the phosphoric acid extractant is P204, the volume fraction of the phosphoric acid extractant is 10-15%, and the volume ratio of the phosphoric acid extractant to the Nth raffinate is 2-1:

1.

8. The method for resource-based treatment of nitric acid waste liquid according to claim 6, characterized in that, In the second separation step, stripping agent II is an H2SO4 solution, stripping agent III is an HCl solution, and the volume ratio of the supported organic phase II to stripping agent II / stripping agent III is 1 to 1.5:

1.

9. The method for resource-based treatment of nitric acid waste liquid according to claim 1, characterized in that, In the second separation step, both extraction and back-extraction have at least two stages, and the duration of each single-stage extraction and back-extraction is at least 3 minutes.

Images