Method for recovering waste etching liquid containing phosphoric acid, acetic acid and nitric acid

Abstract

The invention provides a method for recovering waste etching liquid containing phosphoric acid, acetic acid and nitric acid, which comprises the following steps: carrying out reduced pressure distillation on the waste etching liquid under a reduced pressure condition, distilling and condensing light components of nitric acid and acetic acid to obtain mixed acid liquor of acetic acid and nitric acid, and detecting the content of nitric acid, acetic acid and water in the mixed acid liquor; adding sodium hydroxide or potassium hydroxide and the like into mixed acid liquor of acetic acid and nitric acid, so that all nitric acid in the mixed acid liquor generates nitrate; and adding acetic anhydride into the acetic acid-containing mixed solution, fully reacting, filtering the separated salt, adding an extracting agent into the filtrate, and collecting the high-purity acetic acid. According to the method, phosphoric acid, acetic acid and nitrate in the waste etching liquid are recycled, the recycled acetic acid is high in purity, high in recycling rate and high in operability, large-scale production can be met, resource recycling is achieved to the maximum extent, direct emission of non-phosphorus resources of the waste etching liquid is avoided, and resource waste and environmental pollution are avoided.

Description

Technical Field

[0001] The invention belongs to the field of electronic chemicals, and in particular relates to a method for recovering waste etching liquid containing phosphoric acid, acetic acid and nitric acid. Background Art

[0002] With the rapid development of thin film transistor liquid crystal displays, the amount of aluminum etching solution used for wet etching is also increasing rapidly, and the waste liquid generated is also increasing. Waste aluminum etching solution mainly contains phosphoric acid, nitric acid, acetic acid and a small amount of aluminum and other metal ions. Other waste etching solutions mainly containing phosphoric acid, nitric acid, acetic acid and a small amount of additives, such as waste silver etching solution, waste titanium nitride and tungsten selective etching solution, etc., are also gradually increasing.

[0003] At present, the main domestic waste acid treatment methods include: concentration method, neutralization method, roasting method, extraction method, ion exchange method, etc., none of which can effectively convert waste acid into resources, and it is inevitable to generate waste, which will also have an impact on the environment.

[0004] Chinese patent CN200510075397 proposes a method for purifying phosphoric acid by combining fractionation and esterification, wherein nitric acid is first vaporized and separated, and then most of the acetic acid is separated by negative pressure distillation, and then the remaining phosphoric acid and a small amount of acetic acid mixed solution are esterified with ethanol to convert acetic acid into acetate, thereby separating acetic acid from phosphoric acid. This method does not produce waste liquid and can effectively separate phosphoric acid from etching liquid. However, this process is not only complicated, but also reduces the concentration of phosphoric acid. Some ethanol will remain in the phosphoric acid, affecting the product quality. Chinese patent CN201910730637.9 proposes a method for graded recovery of phosphoric acid, acetic acid and nitric acid from waste etching liquid. Through reduced pressure distillation, acetic acid and nitric acid in the etching liquid are volatilized and recovered by condensation; high-purity phosphoric acid is obtained by adding additives to the remaining phosphoric acid solution, crystallization, washing, dissolution, etc. This method can completely separate phosphoric acid, acetic acid, and nitric acid without producing waste acid. However, this method has a complicated process, and the yield is low and the energy consumption is high in the phosphoric acid crystallization and melting purification process, and it cannot be applied to industrial production on a large scale. From the above examples, we can see that the main component of waste etching solution is phosphoric acid, so the research focus is mainly on the recovery of phosphoric acid. Most of the waste liquid is either harmlessly treated as three wastes, and the resources are not recycled and wasted. Or only the phosphorus resources in it are recovered. However, there is little research on the recovery of acetic acid and nitric acid. Most of the acetic acid and nitric acid are discharged as waste liquid. Or they are not separated, but the recovery and utilization of this part of the waste liquid is difficult to promote and industrialize. Summary of the invention

[0005] In order to solve the above problems, the present invention aims to provide a method for recovering waste etching liquid containing phosphoric acid, acetic acid and nitric acid. In addition to recycling the main phosphorus resources in the waste etching liquid, the mixed waste liquid containing acetic acid and a small amount of nitric acid as the light component after distillation is recycled, thereby improving the recycling rate of acetic acid and also improving the mass concentration and purity of acetic acid after separation. The recovered acetic acid can be reused in the production of various etching solutions. It can also be purified as electronic grade acetic acid. At the same time, industrial phosphoric acid and nitrates are also recovered as fertilizers or made into reagents.

[0006] The technical solution of the present invention is as follows: A method for recovering waste etching liquid containing phosphoric acid, acetic acid and nitric acid, the method comprising the following steps: S1 performs vacuum distillation on the waste etching solution under reduced pressure conditions, distills out the light components of nitric acid and acetic acid first, condenses them through a condenser and collects them to obtain a mixed acid solution of acetic acid and nitric acid, and processes the heavy components to recover the phosphorus resources therein and make industrial phosphoric acid; S2 takes the mixed acid solution of acetic acid and nitric acid obtained in step S1, and detects the nitric acid, acetic acid and water content therein; S3, based on the result of the nitric acid detected in step S2, adding sodium hydroxide or potassium hydroxide to the mixed acid solution of acetic acid and nitric acid, so that all the nitric acid therein is converted into nitrate; S4 accurately adds acetic anhydride to the mixed solution containing acetic acid in step S3 for full reaction. The initial dripping speed of acetic anhydride can be slightly faster, such as 2 drops per second, and the feeding speed can be accelerated later, 6-10 drops per second. It can even be faster. In this process, acetic anhydride and water react almost without reaction at low temperature at the beginning, and the heat of the previous alkali neutralization reaction is well utilized to promote the reaction of acetic anhydride and water. When the acetic anhydride hydrolysis reaction proceeds normally, the reaction is exothermic, and the subsequent acceleration of the feeding of acetic anhydride can prevent the temperature of the system material from soaring too fast, thereby promoting the occurrence of the hydrolysis reaction. At the same time, as the hydrolysis reaction occurs, more and more acetic acid is generated, and the solubility of nitrate in acetic acid solution decreases. When the reaction is carried out to a certain extent, the water content in the system is low, nitrate will precipitate, and the crystal precipitation will absorb heat, which further promotes the hydrolysis reaction of acetic anhydride. In addition, during the entire reaction process, the temperature of the heat source provided outside can be 40-80°C, but at 40-50, very good results can be achieved, high temperature is not required, and the reaction time is not long, which is faster. In this way, the whole operating system is relatively stable and safe, and the high temperature resistance requirements of the equipment are not high. And at the end of the reaction, it is obvious that some solid nitrates have precipitated. When salt is seen to precipitate and the reaction liquid becomes turbid, stop heating and let it cool down to about 13-20℃. After filtering out most of the salt, the filtrate can be added with the extractant anhydrous ethanol, cool down for deep desalination, directly filter the salt impurities, and collect the filtrate.

[0007] The filtrate of S5 S4 is distilled or distilled under reduced pressure or cooled to precipitate acetic acid crystals, which are separated and high-purity acetic acid is collected; at the same time, the extractant is recovered and can be reused.

[0008] The salt solid obtained by filtering S6 S4 is washed and dried to prepare sodium nitrate or potassium nitrate solid, which can be used as fertilizer or for other purposes.

[0009] Furthermore, phosphorus pentoxide may be added to the waste etching solution for reaction before the reduced pressure distillation in step S1).

[0010] Furthermore, during the vacuum distillation process of step S1), the pressure is controlled at -100 ~ -10KPa, and the distillation temperature is controlled at 80 ~ 115°C. The phosphorus resources in the heavy component are directly recovered to make industrial phosphoric acid, and the light components (nitric acid and acetic acid) are collected by condensation after distillation, and the condensation temperature is 40 ~ 70°C.

[0011] Furthermore, in step S2, a sample of the mixed waste liquid containing acetic acid and nitric acid to be treated is taken to detect the contents of nitric acid, acetic acid and water therein.

[0012] Furthermore, the amount of sodium hydroxide or potassium hydroxide added in step S3 is 1-1.2 times the amount of nitric acid.

[0013] Furthermore, in step S4, the amount of acetic anhydride added is 0.7-1.1 times the amount of water content in the waste liquid. Water also includes water generated during the reaction. The temperature at this stage can be controlled at 40-80°C; when the reaction liquid is relatively turbid, the temperature can be adjusted to 13-20°C to facilitate crystal precipitation.

[0014] Furthermore, the extractant added in step S4 is anhydrous ethanol, which is added at a volume ratio of 5%-50%. Furthermore, in step S4, acetic acid is extracted after the reaction by distillation, the distillation temperature is maintained at 80-120°C, and the pressure is controlled at -0.05- -0.1MPa by vacuum distillation, and the vacuum distillation temperature is 40-100°C. Furthermore, the filter membrane used for filtering and desalting in the above steps is made of polytetrafluoroethylene filter membrane.

[0015] Compared with the prior art, the advantages of the present invention are: 1. The present invention separates phosphoric acid, nitric acid and acetic acid in waste etching liquid under high temperature and negative pressure conditions by using the difference in boiling points of phosphoric acid, nitric acid and acetic acid. Since phosphoric acid is the most valuable for recycling in waste etching liquid according to the content of its components, followed by acetic acid, acetic acid and nitric acid are evaporated first by vacuum distillation and separated from phosphoric acid. The heavy component obtained has a high phosphoric acid content and is very valuable for recycling. Industrial phosphoric acid can be obtained by direct treatment. The light components, gaseous nitric acid and acetic acid, are condensed through a liquid separator to obtain a mixed waste acid liquid of nitric acid and acetic acid. In this part of the mixed waste acid liquid, the concentration of acetic acid is slightly higher, while the concentration of nitric acid is not particularly high. Moreover, if it is directly distilled, it cannot be completely separated. If the acetic acid component with a slightly higher content is to be recovered, the nitric acid is converted into salt, and the energy consumption of the subsequent distillation will be very high, and the requirements for the equipment will also be very high. At the same time, the amount of acetic acid recovered is not high. The economic value of recycling is low. We added acetic anhydride, which consumed a large amount of water in the waste acid and further increased the acetic acid content in the waste acid, making subsequent distillation, rectification or vacuum distillation easier, with low temperature, low energy consumption, high recovery rate, and high-purity acetic acid recovered, with a high mass fraction and low metal and organic impurity content. The quality can also be further improved by ion exchange resin according to actual needs, reaching electronic grade level. Depending on different conditions, the recovered acetic acid contains a little water and can be directly used in the configuration of aluminum etching solution, or in the configuration of other etching solutions.

[0016] 2. Other waste etching solutions that mainly contain phosphoric acid, nitric acid, acetic acid and a small amount of additives, such as waste silver etching solution, waste titanium nitride and tungsten selective etching solution, etc., can all use the above method to recover phosphoric acid and acetic acid. At the same time, nitric acid can also be made into sodium nitrate or potassium nitrate salts.

[0017] 3. Sodium hydroxide or potassium hydroxide can be used for neutralization, or calcium hydroxide or calcium oxide and other substances that have the same ability to neutralize nitric acid can be used.

[0018] 4. The advantage of this treatment route is that it uses low-cost acid anhydride to treat waste liquid, which greatly improves the components that you want to recover. The entire experiment uses the reaction heat of the reaction itself to allow the reaction to spontaneously promote the reaction. The overall controlled temperature and other conditions are very easy to achieve, with low energy consumption and relatively higher safety. The requirements for high temperature and high pressure of the equipment are not that high.

[0019] 5. Other mixed solutions containing nitric acid and acetic acid can also be recovered by this method. DETAILED DESCRIPTION

[0020] The following will be combined with the specific embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The embodiments described 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 making creative work belong to the protection scope of the present invention.

[0021] In the context of this specification, except for the contents explicitly described, any matters or items not mentioned directly use the technology known in the art. Moreover, any embodiment described in this patent can be freely combined with one or more other embodiments described in this patent, and the technical solutions or technical ideas formed thereby are regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed in this patent, unless a person skilled in the art considers that the combination is obviously unreasonable.

[0022] The data points disclosed in the present invention include not only the specifically disclosed numerical points, but also the endpoints of each numerical range. Any combination of these data points should be regarded as the disclosed or recorded range of the present invention, regardless of whether these numerical points are disclosed one by one in this article. The percentages in the following examples and comparative examples are all by mass. The reagents are all 99% pure; the water is deionized water.

[0023] In the embodiments and comparative examples, waste etching liquid from an electronics factory was taken, and its main chemical components are shown in Table 1 below. Other impurities such as gold impurities are relatively low and are not listed.

[0024] Table 1

[0025] Example 1 Take 500mL of waste etching liquid, phosphorus pentoxide and other materials and add them into a distillation bottle, control the pressure at -80KPa, the temperature at 80℃, perform vacuum distillation, control the condensation temperature at 40℃, and condense and recover the distillate as a mixture of nitric acid and acetic acid. At the same time, the heavy component is made into industrial phosphoric acid through aeration and water addition.

[0026] The mixed waste acid solution of acetic acid and nitric acid recovered by the above condensation was sampled and tested. The content of nitric acid was 12.58%, and the content of acetic acid was 27.94%. Take 50.0010g of the mixed waste acid solution of acetic acid and acetic acid, add potassium hydroxide with a purity of 90.87 to the recovered mixed solution of acetic acid and nitric acid under stirring, and the amount of potassium hydroxide added is 6.1527g solid. Mix and react thoroughly. After a few minutes, 178.8717g of acetic anhydride was gradually added in multiple times, the reaction temperature was controlled at 50°C, and the reaction was fully mixed for 2 hours. The temperature was controlled at 110°C for distillation. Distillation obtained 195.5216g of acetic acid with a recovery rate of 87.2% of acetic acid. At the same time, 10.0102g of potassium nitrate solid was obtained.

[0027] Embodiment 2: Take 500mL of waste etching liquid, phosphorus pentoxide and other materials and add them into a distillation bottle, control the pressure at -80KPa, the temperature at 80℃, perform vacuum distillation, control the condensation temperature at 40℃, and condense and recover the distillate as a mixture of nitric acid and acetic acid. At the same time, the heavy component is made into industrial phosphoric acid through aeration and water addition.

[0028] The mixed waste acid liquid of acetic acid and nitric acid obtained by the above condensation recovery was sampled and tested. The content of nitric acid was 8.99% and the content of acetic acid was 31.49%. Take 50.0070g of the mixed waste acid liquid of acetic acid and acetic acid, add sodium hydroxide to the recovered mixed solution of acetic acid and nitric acid under stirring, and the amount of sodium hydroxide added is 2.9407g solid. Mix and react thoroughly. After tens of minutes, 168.8032g of acetic anhydride is gradually added dropwise several times, the reaction temperature is controlled at 60°C, and the reaction is fully mixed for 2 hours. The temperature of the vacuum distillation is controlled at 75°C, and the pressure is controlled at about -0.087MPa, with a slight negative pressure. Collect acetic acid by vacuum distillation. 189g of acetic acid with a purity of more than 98% can be obtained, and the recovery rate of acetic acid is 88.3%. At the same time, 6.0214g of nitrate solid is obtained.

[0029] Embodiment 3: Take 500mL of waste etching liquid, phosphorus pentoxide and other materials and add them into a distillation bottle, control the pressure at -50KPa, the temperature at 100℃, perform vacuum distillation, control the condensation temperature at 50℃, and condense and recover the distillate as a mixture of nitric acid and acetic acid. At the same time, the heavy component is made into industrial phosphoric acid through aeration and water addition.

[0030] The mixed waste acid liquid of acetic acid and nitric acid recovered by the above condensation was sampled and tested. The content of nitric acid was 10.04% and the content of acetic acid was 29.52%. Take 49.9960g of the mixed waste acid liquid of acetic acid and acetic acid, add sodium hydroxide to the recovered mixed solution of acetic acid and nitric acid under stirring, and the amount of sodium hydroxide added is 3.3331g solid. Mix and react thoroughly. After tens of minutes, 161.65g of acetic anhydride is gradually added in multiple times, the reaction temperature is controlled at 45°C, and the reaction is fully mixed for 3 hours. The vacuum distillation temperature is controlled at 70°C, the pressure is controlled at about -0.1MPa, and the acetic acid is collected by vacuum distillation. 182.8664g of acetic acid with a purity of more than 98% can be obtained, and the recovery rate of acetic acid is 89.4%. At the same time, 6.5762g of nitrate solid is obtained.

[0031] Embodiment 4: Take 500mL of waste etching liquid and add it to a distillation bottle. Control the pressure at -80KPa and the temperature at 80℃. Perform vacuum distillation and control the condensation temperature at 40℃. Condensate and recover the distillate as a mixture of nitric acid and acetic acid. At the same time, the heavy component is made into industrial phosphoric acid through aeration and water addition.

[0032] The mixed waste acid liquid of acetic acid and nitric acid recovered by the above condensation was sampled and tested. The content of nitric acid was 8.99% and the content of acetic acid was 31.49%. Take 49.9985g of the mixed waste acid liquid of acetic acid and acetic acid, add potassium hydroxide with a purity of 90.87% to the recovered mixed solution of acetic acid and nitric acid under stirring, and the amount of potassium hydroxide added is 4.4007g solid. Mix and react thoroughly. After reacting for a few minutes, 176.1320g of acetic anhydride is gradually added in several times. The speed of acetic anhydride can be slightly faster at the beginning, and it can be accelerated later. The reaction temperature is controlled at 40°C, and the reaction is fully mixed for 2 hours. Filter at room temperature to obtain 216.7114g of 99.6% acetic acid, and the recovery rate of acetic acid is 96.99%. At the same time, 6.5002g of potassium nitrate solid is obtained. Take 100g of the acetic acid filtrate with high purity, add 40mL of anhydrous ethanol, cool to 0℃, let stand until the salt inside is precipitated, filter out the precipitated nitrate, control the filtrate temperature at 75℃, control the pressure at about -0.85MPa, and collect high-purity acetic acid by vacuum distillation. The purity of acetic acid is above 99.85%.

[0033] Example 5 Take 500mL of waste etching liquid and add it to a distillation bottle. Control the pressure at -80KPa and the temperature at 80℃. Perform vacuum distillation and control the condensation temperature at 40℃. Condensate and recover the distillate as a mixture of nitric acid and acetic acid. At the same time, the heavy component is made into industrial phosphoric acid through aeration and water addition.

[0034] The mixed waste acid liquid of acetic acid and nitric acid recovered by the above condensation was sampled and tested. The content of nitric acid was 8.99% and the content of acetic acid was 31.49%. Take 49.9985g of the mixed waste acid liquid of acetic acid and acetic acid, add potassium hydroxide with a purity of 90.87% to the recovered mixed solution of acetic acid and nitric acid under stirring, and the amount of potassium hydroxide added is 4.4007g solid. Mix and react thoroughly. After reacting for a few minutes, 176.1320g of acetic anhydride is gradually added in several times. The speed of acetic anhydride can be slightly faster at the beginning, and it can be accelerated later. The reaction temperature is controlled at 40°C, and the reaction is fully mixed for 2 hours. Filter at room temperature to obtain 216.7114g of 99.6% acetic acid, and the recovery rate of acetic acid is 96.99%. At the same time, 6.5002g of potassium nitrate solid is obtained. Take 100 g of the acetic acid filtrate with higher purity, add 40 mL of anhydrous ethanol, cool to 0°C, let it stand until the salt inside is precipitated, filter out the precipitated nitrate, and continue to cool the filtrate to allow the acetic acid to crystallize. The purity of the separated acetic acid is above 99.85%.

[0035] Comparative Example 1 Based on Example 1, the difference is that potassium hydroxide is not added to the recovered acetic acid and nitric acid mixed solution, acetic anhydride is directly added, the reaction temperature is controlled at 50°C, and the mixture is fully mixed and reacted for 2 hours. The temperature is directly lowered to allow acetic acid crystals to precipitate, and acetic acid crystals are successively precipitated 3 times, filtered and separated, and the purity of the obtained acetic acid crystals is 95.6%. At the same time, the remaining 19.87% of the solution containing acetic acid and nitric acid is also unable to precipitate acetic acid crystals by cooling, and the recovery rate of the collected acetic acid is 83.65%.

[0036] Comparative Example 2 Based on Example 1, potassium hydroxide and acetic anhydride are not added during the entire operation, and the rest is the same as Example 1. The light component obtained is directly distilled according to the different boiling points of nitric acid and acetic acid. The temperature is first controlled at 85°C, and there is no fraction, and then it is adjusted to about 110°C for distillation. The fractions collected by distillation were tested and found to contain both nitric acid and acetic acid, and the two could not be completely separated. After checking the data and combining the test, it was found that the boiling point of nitric acid is 83°C, and it is easy to form an azeotropic system with water, and the boiling point reaches 122°C, while the boiling point of acetic acid is 118°C. The azeotropic system formed by the mixed acid is difficult to be effectively separated by ordinary distillation.

[0037] Comparative Example 3 Based on Example 1, acetic anhydride is not added, 500 mL of waste etching liquid is added to a distillation flask, the pressure is controlled at -80 KPa, the temperature is controlled at 80°C, and the vacuum distillation is carried out, the condensation temperature is controlled at 40°C, and the distillate is condensed and recovered as a mixed solution of nitric acid and acetic acid. At the same time, the heavy component is made into industrial phosphoric acid through aeration and water addition operations.

[0038] The mixed waste acid liquid of acetic acid and nitric acid recovered by the above condensation was sampled and tested, and the content of nitric acid was 8.99%, and the content of acetic acid was 31.49%. Take 50.0070g of the mixed waste acid liquid of acetic acid and acetic acid, and add sodium hydroxide to the recovered mixed liquid of acetic acid and nitric acid under stirring, and the amount of sodium hydroxide added is 2.9407g solid. Mix the reaction thoroughly. The distillation temperature is controlled at 100℃, and the distillation is first collected to detect the water content. The water content of this solution is high. While the water is evaporated, the acetic acid content of the residual liquid is also concentrated. However, the energy consumed by the subsequent distillation of acetic acid is high, and the amount of acetic acid obtained is low.

[0039] The technical solution of the present invention is explained through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above specific embodiments to be implemented. Any improvements made by technicians in the relevant field based on the present invention, or equivalent replacement of the materials selected by the present invention, etc., fall within the scope of protection of the patent.

Claims

1. A method for recovering waste etching liquid containing phosphoric acid, acetic acid and nitric acid, characterized in that: The method comprises the following steps: S1: The waste etching solution is subjected to reduced pressure distillation under reduced pressure conditions, and the light components of nitric acid and acetic acid are first distilled out and condensed through a condenser to obtain a mixed acid solution of acetic acid and nitric acid. The heavy components are processed to recover the phosphorus resources therein and make industrial phosphoric acid; S2 takes the mixed acid solution of acetic acid and nitric acid obtained in step S1, and detects the nitric acid, acetic acid and water content therein; S3, based on the result of the nitric acid detected in step S2, adding sodium hydroxide or potassium hydroxide to the mixed acid solution of acetic acid and nitric acid, so that all the nitric acid therein is converted into nitrate; S4: adding acetic anhydride to the mixed solution containing acetic acid in step S3, filtering out the salt after sufficient reaction, adding an extractant to the filtrate, filtering, and collecting the filtrate; S5 The filtrate obtained in S4 is distilled or distilled under reduced pressure or cooled to precipitate acetic acid crystals, separated, and high-purity acetic acid is collected; S6 The filter residue obtained by filtering S4 is washed and dried to prepare sodium nitrate or potassium nitrate solid, which can be used as fertilizer or for other purposes.

2. The method for recovering waste etching liquid containing phosphoric acid, acetic acid and nitric acid according to claim 1, characterized in that: During the vacuum distillation process of step S1), the pressure is controlled at -100 ~ -10KPa, and the distillation temperature is controlled at 80 ~ 115°C. The heavy components are directly recovered as phosphorus resources to make industrial phosphoric acid, and the light components (nitric acid and acetic acid) are collected by condensation after distillation, and the condensation temperature is 40 ~ 70°C.

3. The method for recovering waste etching liquid containing phosphoric acid, acetic acid and nitric acid according to claim 2, characterized in that: Before the reduced pressure distillation in step S1), phosphorus pentoxide may be added to the waste etching solution for reaction.

4. The method for recovering waste etching liquid containing phosphoric acid, acetic acid and nitric acid according to claim 1, characterized in that: The step S2 takes a sample of the mixed waste liquid containing acetic acid and nitric acid to be treated, and detects the contents of nitric acid, acetic acid and water therein.

5. The method for recovering waste etching liquid containing phosphoric acid, acetic acid and nitric acid according to claim 1, characterized in that: In step S3, the amount of sodium hydroxide or potassium hydroxide added is 1-1.2 times the amount of nitric acid.

6. The method for recovering waste etching liquid containing phosphoric acid, acetic acid and nitric acid according to claim 1, characterized in that: In step S4, the amount of acetic anhydride added is 0.7-1.1 times the amount of water content in the waste liquid, and the reaction temperature is 40-80° C. When the reaction liquid is turbid, the temperature is adjusted to 13-20° C. The dripping speed of acetic anhydride is 2 drops to 10 drops per second.

7. The method for recovering waste etching liquid containing phosphoric acid, acetic acid and nitric acid according to claim 1, characterized in that: In the step S4, the added extractant is anhydrous ethanol, and the anhydrous ethanol is added in a volume ratio of 5%-50%.

8. The method for recovering waste etching liquid containing phosphoric acid, acetic acid and nitric acid according to claim 1, characterized in that: The filtrate of step S4 is distilled or distilled under reduced pressure to collect high-purity acetic acid; or the filtrate of S4 is cooled to precipitate acetic acid crystals, filtered or centrifuged to collect high-purity acetic acid, and the filter membrane used for filtering and desalting is made of polytetrafluoroethylene filter membrane.

9. The method for recovering waste etching liquid containing phosphoric acid, acetic acid and nitric acid according to claim 1, characterized in that: In the step S4, acetic acid is extracted after the reaction by distillation, the distillation temperature is maintained at 80-120°C, and the pressure is controlled at -0.05- -0.1MPa by vacuum distillation, and the vacuum distillation temperature is 40-100°C.

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