Resourceful treatment method for nitric acid waste liquid

Abstract

The invention belongs to the technical field of extraction, and particularly relates to a nitric acid waste liquid resourceful treatment method which comprises a first separation step and a second separation step, in the first separation step, a cross-flow extraction process with more than four stages is adopted, a loaded organic phase is obtained through single-stage extraction, and raffinate obtained through last-time extraction is used for standby application; uniformly mixing the loaded organic phase obtained by single-stage extraction to obtain a loaded organic phase I, and performing reverse extraction on the loaded organic phase I by using a reverse extraction agent I to obtain reverse extraction liquid I; and in the second separation step, the pH value of the raffinate is adjusted to 2.5-3 by using an alkaline substance, then the raffinate is extracted by using a phosphoric acid extraction agent to obtain a loaded organic phase II, and then the loaded organic phase II is subjected to step-by-step reverse extraction by using a stripping agent and a stripping agent III to obtain a reverse extraction solution II and a reverse extraction solution III. Therefore, iron is enriched in the strip liquor I and the strip liquor III, and copper is enriched in the strip liquor II, so that separation of copper and iron from the nitric acid waste liquor and separation of copper and iron are realized, and further resource utilization of the nitric acid waste liquor is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of extraction, and in particular relates to a method for resource processing of nitric acid waste liquid. Background Art

[0002] In some industrial production processes, dirt and metal oxides will be generated on the equipment, which are mainly cleaned by dilute acid, including hydrochloric acid, sulfuric acid, nitric acid and hydrofluoric acid. In some specific production sites, some dirt and metal oxides need to be cleaned with nitric acid to be completely dissolved. This is because nitric acid itself is oxidizing, which can greatly improve the cleaning effect. At the same time, most nitrates are soluble in water, which can greatly ensure the cleanliness of the cleaning. In addition, the substrate equipment cleaned with nitric acid does not have the risk of causing pitting corrosion of the equipment like hydrochloric acid cleaning; moreover, nitric acid is particularly effective in cleaning copper rust. Therefore, nitric acid is mainly used to clean stainless steel, carbon steel, brass, copper and carbon steel-stainless steel equipment and brass-carbon steel welding combined equipment in industrial production. In addition, nitric acid has the characteristics of fast removal of iron oxide scale and iron scale in a short time in removing scale and rust, and has low corrosion to carbon steel, stainless steel and copper. Therefore, the use prospect of nitric acid in specific places is extremely broad.

[0003] However, nitric acid pickling waste liquid has serious oxidizing and acidic properties, and is extremely corrosive. Moreover, there are a large number of metal ions in the pickling waste liquid, and it contains a certain amount of valuable metals. Its direct discharge not only wastes resources but also pollutes the environment and directly endangers the health of animals and plants. At present, the treatment methods of nitric acid pickling waste liquid mainly include high-temperature roasting method, neutralization precipitation method, membrane filtration method, solvent extraction method and vacuum distillation method, etc. Different treatment methods are selected for different components in nitric acid pickling waste liquid. Among them, the high-temperature roasting method requires greater energy consumption, and compared with some nitric acid waste liquids with low valuable metals, the recovery cost is too high, and the economic benefits are poor, and a large amount of pollution will be generated; the neutralization precipitation method requires the addition of a large amount of alkaline substances, which is costly, and will produce a large amount of waste salt slag, increasing the subsequent treatment cost; the membrane filtration method and vacuum distillation method have high requirements for equipment and high treatment costs; the solvent extraction method has high requirements for the extractant, and it is difficult to achieve universal treatment.

[0004] For waste liquid containing high iron, low copper and high nitric acid, the copper-iron extractants circulating on the market cannot extract copper in a high-acid system; while the iron in a high-acid system can be preferentially extracted by some extractants. Therefore, the waste liquid containing high iron, low copper and high nitric acid may be separated in steps. First, the preliminary separation of copper and iron is achieved, and then other methods are used to achieve a complete separation of copper and iron, as well as a complete separation of copper, iron and nitric acid waste liquid. However, how to carry out step-by-step separation to achieve the resource utilization of the waste liquid containing high iron, low copper and high nitric acid is a technical problem that needs to be solved urgently. Summary of the invention

[0005] The present invention aims to provide a method for resource treatment of nitric acid waste liquid, so as to achieve separation of copper, iron and nitric acid in high-iron, low-copper and high-nitric acid waste liquid by step-by-step separation, thereby realizing resource utilization of high-iron, low-copper and high-nitric acid waste liquid.

[0006] In order to achieve the above object, the scheme of the present invention is: a method for recycling nitric acid waste liquid, comprising:

[0007] First separation step:

[0008] 1) N-stage extraction: the extracted organic phase is equally divided into N parts, N ≥ 4; one part of the extracted organic phase is mixed with the nitric acid waste liquid containing high iron and low copper, and the first loaded organic phase and the first raffinate are obtained through extraction; the first raffinate is mixed with a new part of the extracted organic phase, and the second loaded organic phase and the second raffinate are obtained through extraction; and so on, the raffinate obtained from the previous stage of extraction is mixed with a new part of the extracted organic phase, until N parts of the extracted organic phase are exhausted, and the Nth loaded organic phase and the Nth raffinate are obtained;

[0009] 2) Stripping: uniformly mixing the first loaded organic phase, the second loaded organic phase, ... the Nth loaded organic phase to obtain a loaded organic phase I, mixing the loaded organic phase I with a stripping agent I, and stripping to obtain a lean organic phase I and a stripping solution I;

[0010] Second separation step:

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

[0012] 2) Stripping: Stripping the loaded organic phase II in steps using stripping agent II and stripping agent III to obtain lean organic phase II and stripping liquid II and stripping liquid 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, wherein the iron exists in the form of trivalent iron ions, and there are also a large number 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 great influence on the resource recovery of valuable metals, this scheme uses extraction + neutralization treatment to separate copper and iron in the high nitric acid system in steps, reducing the copper and iron content in the waste liquid to below 0.0001g / L, thereby realizing the resource utilization of the nitric acid waste liquid.

[0014] Mainly, after adding alkaline substances to the high-iron and high-nitric acid system to adjust the pH value, precipitation will occur, which affects the separation and purification of metals. In the present scheme, the first separation step directly uses the extraction method to extract part of the iron in the nitric acid waste liquid, reduce the metal content in the nitric acid waste liquid, achieve the initial separation of copper and iron, and avoid precipitation in the nitric acid waste liquid; and the Nth raffinate obtained in the first separation step continues to the next separation, by adding alkaline substances to the Nth raffinate to adjust its pH value, using phosphoric acid extractant P204 to co-extract copper and iron, and then step-by-step back-extraction loaded organic phase II, to achieve complete separation of copper and iron, as well as complete separation of copper and iron from nitric acid waste liquid.

[0015] In summary, this scheme effectively reduces consumption and alkalizes the treatment process through step-by-step separation and extraction. The equipment used in the process are all conventional extraction equipment with low cost, simple operation, and controllable treatment scale, which is suitable for the separation of copper-containing nitric acid waste liquid.

[0016] Optionally, in the first separation step, the extracted 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, when the volume fraction of the phosphoric acid extractant P204 is 20-30%, the extraction effect of iron ions in the high nitric acid system is good.

[0020] Optionally, in the first separation step, the volume ratio of one portion 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 the full extraction of iron ions.

[0022] Optionally, in the first separation step, the volume ratio of the loaded 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 stripping time in this scheme can ensure that the iron ions are fully stripped.

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

[0025] In this scheme, washing water is used to wash the loaded organic phase I to elute the entrained organic phase I.

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

[0027] The O / A ratio and washing time in this scheme can ensure that the entrained organic phase of the extraction is completely eluted, and the waste water 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 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.

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

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

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

[0032] Optionally, in the second separation step, the number of extraction and stripping stages is at least two, and the single-stage extraction time and the single-stage stripping time are both at least 3 minutes.

[0033] In this scheme, the number of extraction and stripping stages in the second separation step is limited to two or more stages, and the single-stage extraction time and the single-stage stripping time are limited to more than 3 minutes, which can ensure the sufficient separation of copper and iron from nitric acid waste liquid and the sufficient separation of copper and iron. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention is a schematic diagram of a method for recycling nitric acid waste liquid. DETAILED DESCRIPTION

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

[0036] The present invention provides a method for recycling nitric acid waste liquid, comprising:

[0037] First separation step:

[0038] 1) N-stage extraction: the extracted organic phase is divided into N equal parts, N≥4; one part of the extracted organic phase is mixed with the nitric acid waste liquid containing high iron and low copper, and the first loaded organic phase and the first raffinate are obtained by extraction; the first raffinate is mixed with a new part of the extracted organic phase, and the second loaded organic phase and the second raffinate are obtained by extraction; and so on, the raffinate obtained by the previous stage extraction is mixed with a new part of the extracted organic phase until the N parts of the extracted organic phase are exhausted, and the Nth loaded organic phase and the Nth raffinate are obtained. Wherein, the extracted organic phase includes a diluent and a phosphoric acid extractant P204, and the volume fraction of the phosphoric acid extractant P204 in the extracted organic phase is 20-30%; the volume ratio of one part of the extracted organic phase to the nitric acid waste liquid containing high iron and low copper is 4-3:1, 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 washing water, and washed to obtain a loaded organic phase I and waste water. The volume ratio of the loaded organic phase I to the washing water is 1:1-2, and the washing time is at least 3 minutes, and the washing water is pure water.

[0040] 3) Stripping: Mix the loaded organic phase I with the stripping agent I, and obtain the lean organic phase I and the stripping solution I by stripping. The volume ratio of the loaded organic phase I to the stripping agent I is 1:1-1.5, the stripping time is at least 3 minutes, the stripping agent I is HCl solution, and the concentration of the HCl solution is 6 mol / L.

[0041] Second separation step:

[0042] 1) Extraction: Use an alkaline substance to adjust the pH value of the Nth raffinate to 2.5-3, and then use a phosphoric acid extractant to extract the Nth raffinate after alkalization to obtain a loaded organic phase II and a raffinate II. 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.

[0043] 2) Stripping: Stripping the loaded organic phase II with stripping agent II and stripping agent III in steps to obtain lean organic phase II and stripping solution II and stripping solution III. Stripping agent II is H2SO4 solution, stripping agent III is HCl solution, and the volume ratio of loaded organic phase II to stripping agent II / stripping agent III is 1 to 1.5:1.

[0044] Moreover, in the second separation step, the number of extraction and stripping stages is two or more, and the single-stage extraction time and the single-stage stripping time are both more than 3 minutes.

[0045] The following specific examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to specifically illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range according to the description herein, and are not limited to the specific values ​​​​exemplified below.

[0046] Example 1

[0047] The composition of a certain nitric acid waste liquid to be treated in this embodiment is as follows: Cu 0.55g / L, Fe 139.46g / L, HNO315%, and the pH value of the nitric acid waste liquid is <0.

[0048] A method for recycling nitric acid waste liquid, the overall process of the method is as follows: Figure 1 As shown, the method specifically comprises the following steps:

[0049] First separation step:

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

[0051] 2) Washing: the first loaded organic phase, the second loaded organic phase, the third loaded organic phase and the fourth loaded organic phase are uniformly mixed and then mixed with pure water, the washing ratio is 1:1, the washing time is 3 minutes, and the loaded organic phase I and waste water are obtained after washing.

[0052] 3) Stripping: The loaded organic phase I is subjected to two-stage countercurrent stripping using stripping agent I (6 mol / L HCl solution) with a stripping ratio of 1:1 and a stripping time of 3 min to obtain a lean organic phase I and stripping solution I (ferric chloride solution). The copper content in the stripping solution I is below 0.0001 g / L.

[0053] In the first separation step, most of the iron in the nitric acid waste liquid is separated through a four-stage cross-current extraction process to obtain a high-concentration ferric chloride solution, thereby achieving a preliminary separation of copper and iron in the nitric acid waste liquid and iron and nitric acid waste liquid.

[0054] Second separation step:

[0055] 1) Extraction: Use sodium hydroxide to adjust the pH value of the fourth raffinate to 2.5, then use a 10% volume fraction of phosphoric acid extractant P204 to extract the alkaline treated fourth raffinate, the extraction ratio is 2:1, the extraction time is 3 minutes, and the loaded organic phase II and raffinate II are obtained. The main component of raffinate II is sodium nitrate, which contains trace impurity ions except copper and iron. After further treatment, sodium nitrate product can be obtained.

[0056] 2) Stripping: Stripping agent II (2 mol / L H2SO4 solution) and stripping agent III (6 mol / L HCl solution) are used to strip the loaded organic phase II in steps, with a stripping ratio of 1.5:1 and a stripping time of 3 minutes to obtain lean organic phase II and stripping solution II and stripping solution III. The main component of stripping solution II is CuSO4, and the iron content is below 0.0008 g / L. After repeated circulation, it can be used to produce electrolytic copper; the main component of stripping solution III is FeCl3, and ferric chloride product can be obtained after repeated circulation.

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

[0058] Embodiment 2-embodiment 5 are basically the same as embodiment 1, and the difference lies in the selection of some parameters, as shown in Table 1 for details.

[0059] Table 1 Parameter selection table of Example 1 to Example 5

[0060]

[0061]

[0062] The degree of separation of copper and iron from nitric acid waste liquid is reflected in the copper and iron content in raffinate II, and the complete separation of copper and iron is reflected in the iron impurity content in stripping liquid II and the copper impurity content in stripping liquid III. As shown in Table 1, the contents of copper and iron in raffinate II are both below 0.0001 g / L, the iron content in stripping liquid II is below 0.0008 g / L, and the copper content in stripping liquid III is below 0.0001 g / L. It can be seen that the degree of separation of copper and iron from nitric acid waste liquid in the present invention is high, and the degree of separation of copper and iron is also high. The present invention can well carry out resource treatment of nitric acid waste liquid.

[0063] Comparative Example 1

[0064] This comparative example is substantially the same as Example 1, except that: in this comparative example, in the first separation step, sodium hydroxide is first added to the nitric acid waste liquid to adjust the pH value of the nitric acid waste liquid, so that the pH value of the nitric acid waste liquid is increased from <0 to 1. During this process, the nitric acid waste liquid gradually becomes turbid, and it is impossible to directly extract iron. After filtering and separating the nitric acid waste liquid, the Cu content in the nitric acid waste liquid is analyzed to be 0.5 g / L, resulting in direct loss of valuable metals, and the separation of copper and iron is not achieved.

[0065] Comparative Example 2

[0066] This comparative example is basically the same as Example 1, except that: in this comparative example, in the second separation step, sodium hydroxide is not used to adjust the pH value of the fourth raffinate. As a result, the iron ion content in the raffinate II is still 1-2 g / L, and the copper ion content is basically the same as that of the nitric acid waste liquid, and the separation of copper and iron and the separation of copper and iron from the nitric acid waste liquid cannot be achieved.

[0067] Comparative Example 3

[0068] This comparative example is basically the same as Example 1, except that: in this comparative example, in the second separation step, the stripping agent II is a 1 mol / L H2SO4 solution, the Cu content in the stripping solution II is 0.37 g / L, the Fe content is 0.0006 g / L, and the Cu content in the stripping solution III is 0.18 g / L, and the Fe content is 1.0 g / L. In this comparative example, the acidity of the stripping agent II is too low, which affects the stripping effect of copper in the loaded organic phase II, making the stripping incomplete, so that the loaded organic phase II strips the remaining copper into the stripping solution III when using the stripping agent 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 this comparative example, in the second separation step, the stripping agent II is a 2.5 mol / L H2SO4 solution, the Cu content in the stripping solution II is 0.55 g / L, the Fe content is 0.0051 g / L, and the Cu content in the stripping solution III is 0.0001 g / L, and the Fe content is 0.995 g / L. In this comparative example, excessive acidity of the stripping agent II will strip iron, affect the purity of copper sulfate in the stripping solution II, and reduce 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 loaded organic phase II, resulting in incomplete iron stripping, reducing the extraction capacity of the extractant in the subsequent cyclic extraction process, and ultimately affecting the separation of copper and iron and 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 of Example 1, but this comparative example does not carry out the second separation step. The 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 stripping agent I is a 2 mol / L H2SO4 solution.

[0074] In this comparative example, the copper ion content in the raffinate I was 0.55 g / L, the iron ion content was 139.46 g / L, and no copper ions and iron ions were detected in the stripping solution I. It can be seen that the use of Mextral984H cannot effectively extract copper ions and iron ions, and it is even more impossible to achieve copper and iron separation. At the same time, the extractant Mextral984H undergoes a significant color change, and the extractant is severely degraded.

[0075] Comparative Example 6

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

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

[0078] After a lot of attempts, the inventors did not find a suitable extractant that could directly extract copper from nitric acid waste liquid, so they gave up the method of separating copper ions before using a phosphoric acid extractant, and chose to use a phosphoric acid extractant to extract iron ions before separating copper and iron and separating copper and iron from nitric acid waste liquid. Due to the high acidity of nitric acid waste liquid, the extraction capacity of the phosphoric acid extractant P204 easily reaches its limit, affecting the separation effect. Therefore, after completing the preliminary separation of copper and iron, conditions are created for the second separation step by neutralizing the Nth raffinate. Due to the strong oxidizing characteristics of the nitric acid system, the selection of the extractant in the second separation step is also extremely important. In this process, the inventors also tried a large number of candidate extractants, and comparative example 7 is used as an example to illustrate.

[0079] Comparative Example 7

[0080] This comparative example is basically the same as Example 1, except that in this comparative example, in the second separation step, the phosphoric acid extractant used is P507. The raffinate II contains 0.51 g / L of copper ions and 0.21 g / L of iron ions, which indicates that the use of extractants P507 and P204 together cannot achieve the separation of copper and iron in nitric acid waste liquid and 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, and copper and iron could not be effectively separated. This shows that under this working condition, P204 is the most suitable extractant in the entire extraction + neutralization treatment process for separating copper and iron.

[0082] The above are only embodiments of the present invention. The invention is not limited to the fields involved in this implementation case. The common sense such as the known specific structures and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field to which the invention belongs before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the present invention. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to explain the content of the claims.

Claims

1. A method for recycling nitric acid waste liquid, characterized in that: include: First separation step: 1) N-stage extraction: the extracted organic phase is equally divided into N parts, N ≥ 4; one part of the extracted organic phase is mixed with the nitric acid waste liquid containing high iron and low copper, and the first loaded organic phase and the first raffinate are obtained through extraction; the first raffinate is mixed with a new part of the extracted organic phase, and the second loaded organic phase and the second raffinate are obtained through extraction; and so on, the raffinate obtained from the previous stage of extraction is mixed with a new part of the extracted organic phase, until N parts of the extracted organic phase are exhausted, and the Nth loaded organic phase and the Nth raffinate are obtained; 2) Stripping: uniformly mixing the first loaded organic phase, the second loaded organic phase, ... the Nth loaded organic phase to obtain a loaded organic phase I, mixing the loaded organic phase I with a stripping agent I, and stripping to obtain a lean organic phase I and a stripping solution I; Second separation step: 1) Extraction: using an alkaline substance to adjust the pH value of the Nth raffinate to 2.5-3, and then using a phosphoric acid extractant to extract the alkalized Nth raffinate to obtain a loaded organic phase II and a raffinate II; 2) Stripping: Stripping the loaded organic phase II in steps using stripping agent II and stripping agent III to obtain lean organic phase II and stripping liquid II and stripping liquid III.

2. The method for recycling nitric acid waste liquid according to claim 1, wherein: In the first separation step, the extracted organic phase includes a diluent and a phosphoric acid extractant P204.

3. The method for recycling nitric acid waste liquid according to claim 2, wherein: In the first separation step, the volume fraction of the phosphoric acid extractant P204 in the extracted organic phase is 20-30%.

4. The method for recycling nitric acid waste liquid according to claim 3, wherein: In the first separation step, the volume ratio of one portion 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.

5. The method for recycling nitric acid waste liquid according to claim 4, wherein: In the first separation step, the volume ratio of the loaded organic phase I to the stripping agent I is 1:1-1.5, the stripping time is at least 3 minutes, and the stripping agent I is HCl solution.

6. The method for recycling nitric acid waste liquid according to claim 1, characterized in that: In the first separation step, there is washing between the N-stage extraction and the back extraction: the first loaded organic phase, the second loaded organic phase ... the Nth loaded organic phase are evenly mixed and then mixed with washing water, and the loaded organic phase I and waste water are obtained by washing.

7. The method for recycling nitric acid waste liquid according to claim 6, wherein: In the first separation step, the volume ratio of the loaded organic phase I to the washing water is 1:1-2, and the washing time is at least 3 minutes, and the washing water is pure water.

8. The method for recycling nitric acid waste liquid according to claim 1, wherein: 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.

9. The method for recycling nitric acid waste liquid according to claim 7, characterized in that: In the second separation step, the stripping agent II is H2SO4 solution, the stripping agent III is HCl solution, and the volume ratio of the loaded organic phase II to the stripping agent II / stripping agent III is 1 to 1.5:

1.

10. The method for recycling nitric acid waste liquid according to claim 1, characterized in that: In the second separation step, the number of extraction and stripping stages is at least two, and the single-stage extraction time and the single-stage stripping time are at least 3 minutes.

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