Method for comprehensive utilization of mixed sulfuric acid and nitric acid wastewater

Abstract

The application belongs to the technical field of wastewater treatment, and particularly relates to a comprehensive utilization method of sulfuric acid and nitric acid mixed acid wastewater. The method comprises the following steps: S1, mixing the sulfuric acid and nitric acid mixed acid wastewater and waste PCB circuit board, and performing a self-catalytic oxidation reaction, pressure filtration, to obtain a copper sulfate solution and tail gas; S2, adding urea to the copper sulfate solution, adding phosphoric acid and ammonia water after no bubbles are generated, stirring, filtering, to obtain a purified copper sulfate solution; the purified copper sulfate solution is subjected to evaporation crystallization, centrifugation and washing separation, to obtain copper sulfate pentahydrate; S3, the tail gas in step S1 is subjected to spray absorption, to obtain dilute nitric acid, and then lime is added to adjust the pH to 1.2-1.6, and then ammonia water is added to adjust the pH to 7, to obtain a calcium ammonium nitrate mother liquor, and the calcium ammonium nitrate mother liquor is subjected to evaporation crystallization and granulation, to obtain calcium ammonium nitrate. The application first cooperatively prepares high-purity copper sulfate pentahydrate and calcium ammonium nitrate from the sulfuric acid and nitric acid mixed acid wastewater and the waste PCB circuit board.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for the comprehensive utilization of sulfuric acid and nitric acid mixed acid wastewater. Background Technology

[0002] Due to the rapid development of modern electronic information products, the PCB (printed circuit board) industry has developed rapidly. The production process of PCB boards uses a large amount of sulfuric acid and nitric acid inorganic acids, which will generate sulfuric acid and nitric acid mixed acid wastewater. If discharged directly, it will not only pollute the environment, but also lead to resource waste. Resource-based treatment of it is a green industry that has environmental, economic and social benefits.

[0003] There are many existing methods for treating mixed acid wastewater. For example, Chinese Patent No. CN107673523A discloses a method for recycling and treating mixed acid wastewater, which includes the following steps: passing the mixed acid wastewater into a first electrolytic cell, where organic impurities in the mixed acid wastewater change from a liquid state to a solid state; filtering the mixed acid wastewater after the first electrolysis; introducing the filtered mixed acid wastewater into a temperature-controlled transfer tank, where the temperature of the mixed acid wastewater is adjusted to 40-50°C; and introducing the temperature-adjusted mixed acid wastewater into a second electrolytic cell, where copper ions in the mixed acid wastewater precipitate to form copper powder. Chinese Patent Publication No. CN118954823A discloses a waste acid resource utilization process, including the following steps: S1, filtering the waste acid solution and then performing membrane distillation to obtain permeate and concentrate; S2, performing diffusion dialysis on the concentrate to obtain dialysate and residual permeate; S3, adding sodium hydroxide solution to the residual permeate to adjust the pH value, centrifuging to obtain aluminum hydroxide precipitate and a mixed solution containing sodium sulfate and sodium nitrate; S4, evaporating and crystallizing the mixed solution containing sodium sulfate and sodium nitrate to obtain sodium sulfate and a first residual liquid; S5, cooling and crystallizing the first residual liquid to obtain sodium nitrate; the membrane distillation includes a first membrane distillation and a second membrane distillation.

[0004] However, the electrolysis and membrane distillation processes involved in the above technical solutions are costly.

[0005] Currently, there is a large amount of waste PCB circuit boards in the PCB industry that urgently need to be recycled and reused. Therefore, it would be of great significance to achieve the synergistic and comprehensive utilization of sulfuric acid and nitric acid mixed acid wastewater and waste PCB circuit boards. Summary of the Invention

[0006] This invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial solution. Specifically, this invention provides a method for the comprehensive utilization of sulfuric acid and nitric acid mixed acid wastewater. This method utilizes sulfuric acid and nitric acid mixed acid wastewater and waste PCB circuit boards, and through self-catalytic oxidation reduction; urea, phosphoric acid, and ammonia water impurity removal, spray absorption, evaporation and crystallization steps, it can obtain high-purity copper sulfate product and by-product ammonium calcium nitrate, realizing the resource utilization of sulfuric acid and nitric acid mixed acid wastewater and waste PCB circuit boards.

[0007] To achieve the above-mentioned objective, this invention provides a method for the comprehensive utilization of sulfuric acid and nitric acid mixed acid wastewater, comprising the following steps:

[0008] S1. Mix sulfuric acid and nitric acid mixed acid wastewater with waste PCB circuit boards, and carry out a catalytic oxidation reaction on its own. After pressure filtration, copper sulfate solution and tail gas are obtained.

[0009] S2. Add urea to the copper sulfate solution. After no more bubbles are produced, add phosphoric acid and ammonia. Stir and filter to obtain a purified copper sulfate solution. The purified copper sulfate solution is then separated by evaporation crystallization, centrifugation, and washing to obtain copper sulfate pentahydrate.

[0010] S3. The tail gas described in step S1 is sprayed and absorbed to obtain dilute nitric acid. Lime is added to adjust the pH to 1.2-1.6, and then ammonia water is added to adjust the pH to 7 to obtain calcium ammonium nitrate mother liquor. The calcium ammonium nitrate mother liquor is evaporated, crystallized, and granulated to obtain calcium ammonium nitrate.

[0011] Optionally, the sulfuric acid and nitric acid mixed acid wastewater in step S1 has a mass percentage concentration of 50-60% and an acidity of 12-18 mol.

[0012] Optionally, the mass ratio of sulfuric acid to nitric acid in the sulfuric acid-nitric acid mixed acid wastewater described in step S1 is 1-10:1.

[0013] Further, optionally, the mass ratio of sulfuric acid to nitric acid in the sulfuric acid-nitric acid mixed acid wastewater in step S1 is 1-4:1.

[0014] Optionally, the copper content of the waste PCB circuit board in step S1 is 15-25 wt%.

[0015] Optionally, the waste PCB circuit board described in step S1 is subjected to crushing.

[0016] Optionally, the mass ratio of the sulfuric acid and nitric acid mixed wastewater to the waste PCB circuit board in step S1 is 1:90-110.

[0017] Optionally, the temperature for the self-catalytic oxidation reaction described in step S1 is 25-30°C, and the time for the self-catalytic oxidation reaction is 30-60 min.

[0018] Optionally, the amount of urea added in step S2 is 1-1.2 times the residual nitrate content in the copper sulfate solution.

[0019] Optionally, the amount of phosphoric acid added in step S2 is 1.3-1.7 times the total content of metal impurities in the sulfuric acid and nitric acid mixed acid wastewater.

[0020] Optionally, the metallic impurities in the sulfuric acid and nitric acid mixed acid wastewater include iron, nickel, zinc, calcium, and magnesium.

[0021] Optionally, the amount of ammonia added in step S2 is used to adjust the pH of the copper sulfate solution to 1.5-1.8.

[0022] Optionally, in step S2, activated carbon is added before adding urea to remove oil, insoluble substances, etc.

[0023] Optionally, the amount of activated carbon added is 0.1-0.3% of the weight of the copper sulfate solution.

[0024] Optionally, the stirring temperature in step S2 is 25-30°C, and the stirring time is 20-40 min.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention is the first to co-prepare copper sulfate pentahydrate and calcium ammonium nitrate from mixed sulfuric acid and nitric acid wastewater and waste PCB circuit boards. The method of this invention is mild and, under specific purification conditions, not only obtains high-purity (99.6% and above) copper sulfate pentahydrate, but also achieves a copper ion recovery rate of 99.9%. In addition, it can reduce the generation of hazardous waste and realize the resource-based treatment of mixed sulfuric acid and nitric acid wastewater. Attached Figure Description

[0027] Figure 1 This is a flowchart of the comprehensive utilization method of sulfuric acid and nitric acid mixed acid wastewater in Embodiment 1 of the present invention.

[0028] Figure 2 This is a photograph of the copper sulfate pentahydrate prepared in Example 1 of the present invention.

[0029] Figure 3 This is a photograph of the calcium ammonium nitrate prepared in Example 1 of the present invention. Detailed Implementation

[0030] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0031] Unless otherwise specified, the raw materials, reagents or apparatus used in the following examples and comparative examples are available from conventional commercial sources or can be obtained by existing known methods.

[0032] Reference Figure 1 A method for comprehensive utilization of sulfuric acid and nitric acid mixed acid wastewater includes the following steps:

[0033] S1. Mix sulfuric acid and nitric acid mixed acid wastewater with waste PCB circuit boards, and carry out a catalytic oxidation reaction on its own. After pressure filtration, copper sulfate solution and tail gas are obtained.

[0034] S2. Add urea to the copper sulfate solution. After no more bubbles are produced, add phosphoric acid and ammonia. Stir and filter to obtain a purified copper sulfate solution. The purified copper sulfate solution is then separated by evaporation crystallization, centrifugation, and washing to obtain copper sulfate pentahydrate.

[0035] S3. The tail gas described in step S1 is sprayed and absorbed to obtain dilute nitric acid. Lime is added to adjust the pH to 1.2-1.6, and then ammonia water is added to adjust the pH to 7 to obtain calcium ammonium nitrate mother liquor. The calcium ammonium nitrate mother liquor is evaporated, crystallized, and granulated to obtain calcium ammonium nitrate.

[0036] In some preferred embodiments, the sulfuric acid and nitric acid mixed acid wastewater in step S1 has a mass percentage concentration of 50-60% and an acidity of 12-18 mol.

[0037] Specifically, the mass percentage concentration of the sulfuric acid and nitric acid mixed acid wastewater in step S1 is 52%, 54%, 55%, 56%, 58%, or 60%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] Specifically, the acidity of the sulfuric acid and nitric acid mixed acid wastewater in step S1 is 12 mol / L, 14 mol / L, 16 mol / L, or 18 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Solutions outside this range require pretreatment, such as adding ammonia or adjusting the acidity with liquid alkali.

[0040] If the mass percentage concentration and acidity of the sulfuric acid and nitric acid mixed acid wastewater exceed the above range, ammonia or liquid alkali can be added for adjustment.

[0041] In some preferred embodiments, the mass ratio of sulfuric acid to nitric acid in the sulfuric acid-nitric acid mixed acid wastewater in step S1 is 1-10:1.

[0042] Specifically, in step S1, the mass ratio of sulfuric acid to nitric acid in the sulfuric acid-nitric acid mixed acid wastewater is 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1, preferably 1:1, 2:1, 3:1, or 4:1.

[0043] In some preferred embodiments, the waste PCB circuit board in step S1 is crushed to accelerate the reaction rate.

[0044] In some preferred embodiments, the copper content of the waste PCB circuit board in step S1 is 15-25 wt%.

[0045] Specifically, the copper content of the waste PCB circuit board mentioned in step S1 is 15wt%, 17wt%, 19wt%, 20wt%, 22wt%, 24wt%, and 45wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0046] In some preferred embodiments, the mass ratio of the sulfuric acid and nitric acid mixed acid wastewater to the waste PCB circuit board in step S1 is 1:90-110.

[0047] Specifically, the mass ratio of the sulfuric acid and nitric acid mixed acid wastewater to the waste PCB circuit board in step S1 is 1:90, 1:95, 1:100, 1:105, or 1:110, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] In some preferred embodiments, the temperature for the self-catalytic oxidation reaction in step S1 is 25-30°C, and the time for the self-catalytic oxidation reaction is 30-60 min.

[0049] Specifically, the reaction temperature in step S1 is 25°C, 26°C, 27°C, 28°C, 29°C, or 30°C, but is not limited to the listed values; other unlisted values ​​within the range are also applicable. The reaction time is 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, or 60 min, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0050] In some preferred embodiments, the amount of urea added in step S2 is 1-1.2 times the residual nitrate content in the copper sulfate solution.

[0051] Specifically, the amount of urea added in step S2 is 1, 1.1, or 1.2 times the residual nitrate content in the copper sulfate solution, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0052] In some preferred embodiments, the amount of phosphoric acid added in step S2 is 1.3-1.7 times the total content of metal impurities in the sulfuric acid and nitric acid mixed acid wastewater.

[0053] Specifically, the amount of phosphoric acid added in step S2 is 1.3 times, 1.4 times, 1.5 times, 1.6 times, and 1.7 times the total content of metal impurities in the sulfuric acid and nitric acid mixed acid wastewater, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0054] The metallic impurities in the aforementioned sulfuric acid and nitric acid mixed acid wastewater include iron, nickel, zinc, calcium, and magnesium.

[0055] In some preferred embodiments, the amount of ammonia added in step S2 is used to adjust the pH of the copper sulfate solution to 1.5-1.8.

[0056] Specifically, the amount of ammonia added in step S2 is to adjust the pH of the copper sulfate solution to 1.5, 1.6, 1.7, or 1.8, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0057] In some preferred embodiments, step S2 involves adding activated carbon before adding urea to remove oil, insoluble substances, etc.

[0058] In some preferred embodiments, the amount of activated carbon added is 0.1-0.3% of the weight of the copper sulfate solution.

[0059] Specifically, the amount of activated carbon added is 0.1%, 0.15%, 0.2%, 0.25%, or 0.3% of the weight of the copper sulfate solution, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0060] In some preferred embodiments, the stirring temperature in step S2 is 25-30°C, and the stirring time is 20-40 min.

[0061] Specifically, the stirring temperature in step S2 is 25℃, 26℃, 27℃, 28℃, 29℃, or 30℃, but is not limited to the listed values; other unlisted values ​​within the range are also applicable. The stirring time is 20min, 30min, or 40min, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0062] Specifically, step S3 involves adding lime to adjust the pH to 1.2, 1.4, or 1.6, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0063] The mechanism of the technical solution of this invention is as follows:

[0064] Waste PCB circuit boards contain high-purity Cu monomers. In step S1, the nitric acid in the sulfuric acid and nitric acid wastewater reacts with the waste PCB circuit boards through a catalytic oxidation reaction to produce Cu. 2+ And the generation of NO exhaust gas, Cu 2+ It reacts with sulfate ions in sulfuric and nitric acid wastewater to produce copper sulfate solution:

[0065] ;

[0066] .

[0067] In step S2, urea is first added to remove residual nitric acid, phosphoric acid, and ammonia from the copper sulfate solution. Under specific pH conditions, these react with metallic impurities in the copper sulfate solution to form a precipitate, which is then purified by pressure filtration.

[0068] ;

[0069] This represents metallic impurities.

[0070] The inventors discovered that the order in which urea, phosphoric acid, and ammonia are added in step S2 is crucial; otherwise, the purity of the resulting copper sulfate pentahydrate will decrease significantly.

[0071] The exhaust gas in step S3 is absorbed by spraying to obtain dilute nitric acid:

[0072] ;

[0073] .

[0074] This invention is the first to co-prepare copper sulfate pentahydrate and calcium ammonium nitrate from mixed sulfuric acid and nitric acid wastewater and waste PCB circuit boards. The method of this invention is mild and, under specific purification conditions, not only obtains high-purity (99.6% and above) copper sulfate pentahydrate, but also achieves a copper ion recovery rate of 99.9% and above. In addition, it can reduce the generation of hazardous waste and realize the resource-based treatment of mixed sulfuric acid and nitric acid wastewater.

[0075] Example 1: Comprehensive utilization method of sulfuric acid and nitric acid mixed acid wastewater from a PCB circuit board:

[0076] In this embodiment, the mass ratio of sulfuric acid to nitric acid in the mixed sulfuric acid and nitric acid wastewater is 2:1; the mass percentage concentration is 55%; the acidity is 12.33 mol / L; Fe: 33.2 mg / L; Ni: 6.5 mg / L; Zn: 12.1 mg / L; Ca: 6.3 mg / L; Mg: 9.6 mg / L; and the copper content of the waste PCB circuit board is 20 wt%.

[0077] S1. Add the sulfuric acid and nitric acid mixed acid wastewater and the crushed waste PCB circuit board (the mass ratio of sulfuric acid and nitric acid mixed acid wastewater to waste PCB circuit board is 1:100) into the catalytic oxidation reaction tank. After the catalytic oxidation reaction is carried out at 25°C for 60 minutes, the supernatant of the reaction tank is removed by pressure filtration to remove the residual PCB circuit board, and copper sulfate solution and tail gas are obtained.

[0078] S2. The copper sulfate solution is pumped into a pretreatment tank. Activated carbon (0.3% of the weight of the copper sulfate solution) is added first to remove oil and insoluble matter. Then urea (1 times the residual nitrate content in the copper sulfate solution) is added. After no more bubbles are generated, phosphoric acid (1.5 times the total metal impurities in the sulfuric acid and nitric acid mixed wastewater) is added. At the same time, sufficient ammonia is added to adjust the pH to 1.5. The mixture is stirred at 25°C for 30 minutes and filtered to obtain a purified copper sulfate solution. The purified copper sulfate solution is then evaporated, crystallized, centrifuged, and washed to obtain copper sulfate pentahydrate.

[0079] S3. The tail gas described in step S1 is sprayed and absorbed to obtain dilute nitric acid. Lime is added to adjust the pH to 1.5, and then ammonia water is added to adjust the pH to 7 to obtain calcium ammonium nitrate mother liquor. The calcium ammonium nitrate mother liquor is evaporated, crystallized, and granulated to obtain calcium ammonium nitrate.

[0080] The copper recovery rate of the pentahydrate copper sulfate obtained in this example is 99.9%, the purity is 99.6%, the chloride ion content is 10 ppm, and no metallic impurities are detected, far exceeding the requirements for superior grade electroplated copper sulfate specified in standard HG / T 3592-2020.

[0081] Example 2: Comprehensive utilization method of sulfuric acid and nitric acid mixed acid wastewater from a PCB circuit board:

[0082] In this embodiment, the sulfuric acid to nitric acid ratio in the mixed sulfuric acid and nitric acid wastewater is 4:1; the mass percentage concentration is 60%; the acidity is 15.52 mol / L; Fe: 38.8 mg / L; Ni: 9.2 mg / L; Zn: 9.9 mg / L; Ca: 7.5 mg / L; Mg: 8.2 mg / L; and the copper content of the waste PCB circuit board is 20 wt%.

[0083] S1. Add the sulfuric acid and nitric acid mixed acid wastewater and the crushed waste PCB circuit board (the mass ratio of sulfuric acid and nitric acid mixed acid wastewater to waste PCB circuit board is 1:110) into the catalytic oxidation reaction tank. After the catalytic oxidation reaction is carried out at 25°C for 60 minutes, the supernatant of the reaction tank is removed by pressure filtration to remove the residual PCB circuit board, and copper sulfate solution and tail gas are obtained.

[0084] S2. The copper sulfate solution is pumped into a pretreatment tank. Activated carbon (0.3% of the weight of the copper sulfate solution) is added first to remove oil and insoluble matter. Then urea (1.1 times the residual nitrate content in the copper sulfate solution) is added. After no more bubbles are generated, phosphoric acid (1.6 times the total metal impurities in the sulfuric acid and nitric acid mixed wastewater) is added. At the same time, sufficient ammonia is added to adjust the pH to 1.6. The mixture is stirred at 25°C for 30 minutes and filtered to obtain a purified copper sulfate solution. The purified copper sulfate solution is then evaporated, crystallized, centrifuged, and washed to obtain copper sulfate pentahydrate.

[0085] S3. The tail gas described in step S1 is sprayed and absorbed to obtain dilute nitric acid. Lime is added to adjust the pH to 1.5, and then ammonia water is added to adjust the pH to 7 to obtain calcium ammonium nitrate mother liquor. The calcium ammonium nitrate mother liquor is evaporated, crystallized, and granulated to obtain calcium ammonium nitrate.

[0086] The copper recovery rate of the pentahydrate copper sulfate obtained in this example is 99.9%, the purity is 99.8%, the chloride ion content is 15 ppm, and no metallic impurities are detected, which far exceeds the requirements for superior grade electroplated copper sulfate specified in standard HG / T 3592-2020.

[0087] Comparative Example 1: Comprehensive Utilization Method of Sulfuric Acid and Nitric Acid Mixed Acid Wastewater from a PCB Circuit Board

[0088] The sulfuric acid to nitric acid ratio in the mixed sulfuric acid and nitric acid wastewater used in this comparative example was 2:1; the mass percentage concentration was 55%; the acidity was 12.33 mol / L; Fe: 33.2 mg / L; Ni: 6.5 mg / L; Zn: 12.1 mg / L; Ca: 6.3 mg / L; Mg: 9.6 mg / L; and the copper content of the waste PCB circuit board was 20 wt%.

[0089] S1. Add the sulfuric acid and nitric acid mixed acid wastewater and the crushed waste PCB circuit board (the mass ratio of sulfuric acid and nitric acid mixed acid wastewater to waste PCB circuit board is 1:100) into the catalytic oxidation reaction tank. After the catalytic oxidation reaction is carried out at 25°C for 60 minutes, the supernatant of the reaction tank is removed by pressure filtration to remove the residual PCB circuit board, and copper sulfate solution and tail gas are obtained.

[0090] S2. The copper sulfate solution is pumped into a pretreatment tank. Activated carbon (0.3% of the weight of the copper sulfate solution) is added first to remove oil and insoluble matter. Phosphoric acid (1.5 times the total metal impurities in the sulfuric acid-nitric acid mixed wastewater) is then added, along with sufficient ammonia to adjust the pH to 1.5. The mixture is stirred at 25°C for 30 minutes, and then urea (1 times the residual nitrate content in the copper sulfate solution) is added. After no more bubbles are generated, the solution is filtered to obtain a purified copper sulfate solution. The purified copper sulfate solution is then evaporated, crystallized, centrifuged, and washed to obtain copper sulfate pentahydrate.

[0091] S3. The tail gas described in step S1 is sprayed and absorbed to obtain dilute nitric acid. Lime is added to adjust the pH to 1.5, and then ammonia water is added to adjust the pH to 7 to obtain calcium ammonium nitrate mother liquor. The calcium ammonium nitrate mother liquor is evaporated, crystallized, and granulated to obtain calcium ammonium nitrate.

[0092] The comparative example yielded copper sulfate pentahydrate with a copper recovery rate of 99.2%, a purity of 96.9%, a chloride ion content of 50 ppm, and the following concentrations: Fe: 12.6 mg / L; Ni: 2.3 mg / L; Zn: 7.9 mg / L; Ca: 2.7 mg / L; Mg: 4.9 mg / L.

[0093] As can be seen from the comparison between Example 1 and Comparative Example 1, when phosphoric acid and ammonia are added first and then urea is added in step S2, the purity of copper sulfate pentahydrate decreases significantly.

[0094] Comparative Example 2: Comprehensive Utilization Method of Sulfuric Acid and Nitric Acid Mixed Acid Wastewater from a PCB Circuit Board

[0095] The sulfuric acid to nitric acid ratio in the mixed sulfuric acid and nitric acid wastewater used in this comparative example was 2:1; the mass percentage concentration was 55%; the acidity was 12.33 mol / L; Fe: 33.2 mg / L; Ni: 6.5 mg / L; Zn: 12.1 mg / L; Ca: 6.3 mg / L; Mg: 9.6 mg / L; and the copper content of the waste PCB circuit board was 20 wt%.

[0096] S1. Add the sulfuric acid and nitric acid mixed acid wastewater and the crushed waste PCB circuit board (the mass ratio of sulfuric acid and nitric acid mixed acid wastewater to waste PCB circuit board is 1:100) into the catalytic oxidation reaction tank. After the catalytic oxidation reaction is carried out at 25°C for 60 minutes, the supernatant of the reaction tank is removed by pressure filtration to remove the residual PCB circuit board, and copper sulfate solution and tail gas are obtained.

[0097] S2. The copper sulfate solution is pumped into a pretreatment tank. Activated carbon (0.3% of the weight of the copper sulfate solution) is added first to remove oil and insoluble matter. Then urea (1 times the residual nitrate content in the copper sulfate solution) is added. After no more bubbles are generated, phosphoric acid (2 times the total metal impurities in the sulfuric acid-nitric acid mixed wastewater) is added. At the same time, sufficient ammonia is added to adjust the pH to 1.5. The mixture is stirred at 25°C for 30 minutes and filtered to obtain a purified copper sulfate solution. The purified copper sulfate solution is then evaporated, crystallized, centrifuged, and washed to obtain copper sulfate pentahydrate.

[0098] S3. The tail gas described in step S1 is sprayed and absorbed to obtain dilute nitric acid. Lime is added to adjust the pH to 1.5, and then ammonia water is added to adjust the pH to 7 to obtain calcium ammonium nitrate mother liquor. The calcium ammonium nitrate mother liquor is evaporated, crystallized, and granulated to obtain calcium ammonium nitrate.

[0099] The copper recovery rate of the pentahydrate copper sulfate obtained in this comparative example was 95.5%, the purity was 99.7%, the chloride ion content was 8 ppm, and no metal impurities were detected.

[0100] As can be seen from the comparison between Example 1 and Comparative Example 2, when the amount of phosphoric acid added in step S2 exceeds 1.7 times the total content of metal impurities in the sulfuric acid and nitric acid mixed acid wastewater, the copper recovery rate decreases significantly.

[0101] Comparative Example 3: Comprehensive Utilization Method of Sulfuric Acid and Nitric Acid Mixed Acid Wastewater from a PCB Circuit Board

[0102] In this comparative example, the mass ratio of sulfuric acid to nitric acid in the mixed sulfuric acid and nitric acid wastewater was 2:1; the mass percentage concentration was 70%; the acidity was 20 mol / L; the Fe content was 42.5 mg / L; the Ni content was 8.9 mg / L; the Zn content was 16.2 mg / L; the Ca content was 7.1 mg / L; the Mg content was 12.6 mg / L; and the copper content of the waste PCB circuit board was 20 wt%.

[0103] S1. Add the sulfuric acid and nitric acid mixed acid wastewater and the crushed waste PCB circuit board (the mass ratio of sulfuric acid and nitric acid mixed acid wastewater to waste PCB circuit board is 1:110) into the catalytic oxidation reaction tank. After the catalytic oxidation reaction is carried out at 25°C for 60 minutes, the supernatant of the reaction tank is removed by pressure filtration to remove the residual PCB circuit board, and copper sulfate solution and tail gas are obtained.

[0104] S2. The copper sulfate solution is pumped into a pretreatment tank. Activated carbon (0.3% of the weight of the copper sulfate solution) is added first to remove oil and insoluble matter. Then urea (1 times the residual nitrate content in the copper sulfate solution) is added. After no more bubbles are generated, phosphoric acid (1.5 times the total metal impurities in the sulfuric acid and nitric acid mixed wastewater) is added. At the same time, sufficient ammonia is added to adjust the pH to 1.5. The mixture is stirred at 25°C for 30 minutes and filtered to obtain a purified copper sulfate solution. The purified copper sulfate solution is then evaporated, crystallized, centrifuged, and washed to obtain copper sulfate pentahydrate.

[0105] S3. The tail gas described in step S1 is sprayed and absorbed to obtain dilute nitric acid. Lime is added to adjust the pH to 1.5, and then ammonia water is added to adjust the pH to 7 to obtain calcium ammonium nitrate mother liquor. The calcium ammonium nitrate mother liquor is evaporated, crystallized, and granulated to obtain calcium ammonium nitrate.

[0106] The comparative example yielded copper sulfate pentahydrate with a copper recovery rate of 96.2%, a purity of 95.1%, a chloride ion content of 120 ppm, and the following concentrations: Fe: 14.7 mg / L; Ni: 3.8 mg / L; Zn: 9.3 mg / L; Ca: 4.5 mg / L; Mg: 6.3 mg / L.

[0107] As can be seen from the comparison between Example 1 and Comparative Example 3, when the mass percentage concentration and acidity of the sulfuric acid and nitric acid mixed acid wastewater used are not within the preferred range of the present invention, it will lead to a significant decrease in copper recovery rate and purity of copper sulfate pentahydrate.

[0108] Comparative Example 4: Comprehensive Utilization Method of Sulfuric Acid and Nitric Acid Mixed Acid Wastewater from a PCB Circuit Board

[0109] The sulfuric acid to nitric acid ratio in the mixed sulfuric acid and nitric acid wastewater used in this comparative example was 2:1; the mass percentage concentration was 55%; the acidity was 12.33 mol / L; Fe: 33.2 mg / L; Ni: 6.5 mg / L; Zn: 12.1 mg / L; Ca: 6.3 mg / L; Mg: 9.6 mg / L; and the copper content of the waste PCB circuit board was 20 wt%.

[0110] S1. Add the sulfuric acid and nitric acid mixed acid wastewater and the crushed waste PCB circuit board (the mass ratio of sulfuric acid and nitric acid mixed acid wastewater to waste PCB circuit board is 1:100) into the catalytic oxidation reaction tank. After the catalytic oxidation reaction is carried out at 25°C for 60 minutes, the supernatant of the reaction tank is removed by pressure filtration to remove the residual PCB circuit board, and copper sulfate solution and tail gas are obtained.

[0111] S2. The copper sulfate solution is pumped into a pretreatment tank. Activated carbon (0.3% of the weight of the copper sulfate solution) is added first to remove oil and insoluble matter. Then urea (0.8 times the residual nitrate content in the copper sulfate solution) is added. After no more bubbles are generated, phosphoric acid (1.5 times the total metal impurities in the sulfuric acid-nitric acid mixed wastewater) is added. At the same time, sufficient ammonia is added to adjust the pH to 1.5. The mixture is stirred at 25°C for 30 minutes and filtered to obtain a purified copper sulfate solution. The purified copper sulfate solution is then evaporated, crystallized, centrifuged, and washed to obtain copper sulfate pentahydrate.

[0112] S3. The tail gas described in step S1 is sprayed and absorbed to obtain dilute nitric acid. Lime is added to adjust the pH to 1.5, and then ammonia water is added to adjust the pH to 7 to obtain calcium ammonium nitrate mother liquor. The calcium ammonium nitrate mother liquor is evaporated, crystallized, and granulated to obtain calcium ammonium nitrate.

[0113] The comparative example yielded copper sulfate pentahydrate with a copper recovery rate of 99.2%, a purity of 96.1%, a chloride ion content of 66 ppm, and the following concentrations: Fe: 13.5 mg / L; Ni: 2.9 mg / L; Zn: 8.6 mg / L; Ca: 3.2 mg / L; Mg: 5.1 mg / L.

[0114] Comparative Example 5: Comprehensive Utilization Method of Sulfuric Acid and Nitric Acid Mixed Acid Wastewater from a PCB Circuit Board.

[0115] The sulfuric acid to nitric acid ratio in the mixed sulfuric acid and nitric acid wastewater used in this comparative example was 2:1; the mass percentage concentration was 55%; the acidity was 12.33 mol / L; Fe: 33.2 mg / L; Ni: 6.5 mg / L; Zn: 12.1 mg / L; Ca: 6.3 mg / L; Mg: 9.6 mg / L; and the copper content of the waste PCB circuit board was 20 wt%.

[0116] S1. Add the sulfuric acid and nitric acid mixed acid wastewater and the crushed waste PCB circuit board (the mass ratio of sulfuric acid and nitric acid mixed acid wastewater to waste PCB circuit board is 1:100) into the catalytic oxidation reaction tank. After the catalytic oxidation reaction is carried out at 25°C for 60 minutes, the supernatant of the reaction tank is removed by pressure filtration to remove the residual PCB circuit board, and copper sulfate solution and tail gas are obtained.

[0117] S2. The copper sulfate solution is pumped into a pretreatment tank. Activated carbon (0.3% of the weight of the copper sulfate solution) is added first to remove oil and insoluble matter. Then urea (1.4 times the residual nitrate content in the copper sulfate solution) is added. After no more bubbles are generated, phosphoric acid (1.5 times the total metal impurities in the sulfuric acid-nitric acid mixed wastewater) is added. At the same time, sufficient ammonia is added to adjust the pH to 1.5. The mixture is stirred at 25°C for 30 minutes, filtered, and purified copper sulfate solution is obtained. The purified copper sulfate solution is then evaporated, crystallized, centrifuged, and washed to obtain copper sulfate pentahydrate.

[0118] S3. The tail gas described in step S1 is sprayed and absorbed to obtain dilute nitric acid. Lime is added to adjust the pH to 1.5, and then ammonia water is added to adjust the pH to 7 to obtain calcium ammonium nitrate mother liquor. The calcium ammonium nitrate mother liquor is evaporated, crystallized, and granulated to obtain calcium ammonium nitrate.

[0119] The comparative example yielded copper sulfate pentahydrate with a copper recovery rate of 99.4%, a purity of 97.3%, a chloride ion content of 43 ppm, and the following concentrations: Fe: 8.2 mg / L; Ni: 2.5 mg / L; Zn: 6.5 mg / L; Ca: 2.0 mg / L; Mg: 3.2 mg / L.

[0120] As can be seen from the comparison of Example 1, Comparative Example 4 and Comparative Example 5, when the amount of urea added in step S2 is not 1-1.2 times the residual nitrate content in the copper sulfate solution, the purity of copper sulfate pentahydrate decreases significantly.

[0121] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for comprehensive utilization of sulfuric acid and nitric acid mixed acid wastewater, characterized in that, Includes the following steps: S1. Mix sulfuric acid and nitric acid mixed acid wastewater with waste PCB circuit boards, and carry out a catalytic oxidation reaction on its own. After pressure filtration, copper sulfate solution and tail gas are obtained. S2. Add urea to the copper sulfate solution. After no more bubbles are produced, add phosphoric acid and ammonia. Stir and filter to obtain a purified copper sulfate solution. The purified copper sulfate solution was subjected to evaporation crystallization, centrifugation, and washing to obtain copper sulfate pentahydrate. S3. The exhaust gas mentioned in step S1 is absorbed by spraying, and lime is added to adjust the pH to 1.2-1.

6. Then, ammonia water is added to adjust the pH to 7 to obtain calcium ammonium nitrate mother liquor. The calcium ammonium nitrate mother liquor is evaporated, crystallized, and granulated to obtain calcium ammonium nitrate. The sulfuric acid and nitric acid mixed acid wastewater described in step S1 has a mass percentage concentration of 50-60% and an acidity of 12-18 mol / L; In step S1, the mass ratio of sulfuric acid to nitric acid in the sulfuric acid-nitric acid mixed acid wastewater is 1-10:1; The copper content of the waste PCB circuit board mentioned in step S1 is 15-25 wt%; The temperature for the self-catalytic oxidation reaction described in step S1 is 25-30℃, and the time for the self-catalytic oxidation reaction is 30-60 min. The amount of urea added in step S2 is 1-1.2 times the residual nitrate content in the copper sulfate solution; The amount of phosphoric acid added in step S2 is 1.3-1.7 times the total content of metal impurities in the sulfuric acid and nitric acid mixed acid wastewater; The amount of ammonia added in step S2 is to adjust the pH of the copper sulfate solution to 1.5-1.

8.

2. The method for comprehensive utilization of sulfuric acid and nitric acid mixed acid wastewater according to claim 1, characterized in that, In step S1, the mass ratio of sulfuric acid to nitric acid in the sulfuric acid-nitric acid mixed acid wastewater is 1-4:

1.

3. The method for comprehensive utilization of sulfuric acid and nitric acid mixed acid wastewater according to claim 2, characterized in that, The metallic impurities in the sulfuric acid and nitric acid mixed acid wastewater include iron, nickel, zinc, calcium, and magnesium.

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