A resourceful treatment process of nickel-containing etching waste liquid

Abstract

The application discloses a kind of resource processing technology of nickel-containing etching waste liquid, comprising the following steps: S1, pretreatment: adding lye to nickel-containing etching waste liquid to adjust pH to 3.5~4.0, then heated stirring treatment, again, standing aging treatment, obtain containing nickel fluoride turbidity liquid;S2, centrifugal: the centrifugal treatment of containing nickel fluoride turbidity liquid;S3, main reaction: with hot water to clean nickel fluoride by-product, cleaning wastewater is added to the etching waste liquid after pretreatment, then add hydrofluoric acid to adjust the ratio of ammonium fluoride and hydrofluoric acid to 0.9~1.2:1, after reaction, obtain reaction liquid;S4, concentration;S6, centrifugal;S7, drying: ammonium bifluoride crystal is dried to obtain ammonium bifluoride product.The application controls precipitated nickel fluoride by adjusting process conditions, solves the influence of nickel-ammonium complexation on the direction of treating nickel-containing etching waste liquid by precipitation method by pH control, reduces auxiliary material addition and environmental pollution, realizes resource recycling, and reduces production cost.

Description

Technical Field

[0001] This invention relates to the field of waste liquid treatment technology, and in particular to a resource-based treatment process for nickel-containing etching waste liquid. Background Technology

[0002] Nickel-containing etching wastewater is commonly found in the electroplating and metallurgical industries. It mainly originates from the pickling and rinsing of metal parts during the pretreatment process, as well as the rinsing water after plating in acidic electroplating tanks such as acidic copper and nickel plating. Nickel-containing etching wastewater from PCB (printed circuit board) factories also discharges nickel-containing wastewater from the nickel plating cleaning process. The nickel concentration is high. The characteristics of nickel-containing etching wastewater are that the nickel content is relatively high, between 1% and 5%, and the solution also contains 8% to 15% hydrofluoric acid and 7% to 18% ammonium fluoride.

[0003] For semiconductor etching waste liquid, which is mainly composed of ammonium fluoride and hydrofluoric acid, the difficulty in treating nickel-containing etching waste liquid compared to ordinary nickel-containing waste liquid lies in the fact that in the presence of high ammonia nitrogen, simple precipitation methods easily produce nickel-ammonium complexes, which prevents nickel from being efficiently precipitated. Patent application CN112645396A discloses a method for treating fluorinated nickel slag generated during the preparation of nitrogen trifluoride. The fluorinated nickel slag mainly contains nickel, iron, fluorine, and ammonia nitrogen. First, the solid powder of nickel-containing waste slag is dissolved in hydrofluoric acid solution. During the dissolution process, an oxidizing substance is added to promote the dissolution of the fluorinated nickel slag, resulting in a mixed solution containing nickel fluoride, ammonium fluoride, iron fluoride, and hydrofluoric acid. Then, ammonia water is used to adjust the pH value, causing iron to precipitate in the form of iron hydroxide. Nickel fluoride and ammonium fluoride in the solution are separated from the mixed solution by recrystallization based on their differences in solubility.

[0004] This technology uses hydrogen peroxide in the dissolution of fluorine-containing nickel slag. Firstly, it oxidizes ferrous ions, causing them to precipitate and lowering the pH to improve precipitation efficiency. Secondly, it can appropriately disrupt the stability of nickel-ammonium complexes at pH above 5. However, the aforementioned nickel-containing etching wastewater does not contain iron, so oxidants are unnecessary. If used for complex breaking, oxidants are not very effective; a combination of advanced oxidation and physical adsorption methods is required. Furthermore, hydrogen peroxide and other oxidants are controlled chemicals, making their purchase and usage inconvenient. Summary of the Invention

[0005] The main objective of this invention is to provide a simple, efficient, and low-material-consumption resource recovery process for nickel-containing etching waste liquid.

[0006] To achieve the above objectives, the present invention provides a resource recovery process for nickel-containing etching waste liquid, comprising the following steps:

[0007] S1. Pretreatment: Add alkaline solution to nickel-containing etching waste liquid to adjust the pH value to 3.5-4.0, then heat and stir, and then let it stand and age to obtain nickel fluoride turbid liquid.

[0008] S2. Centrifugation: Centrifuge the nickel fluoride turbid liquid to obtain nickel fluoride by-product and pretreated etching waste liquid.

[0009] S3. Main reaction: Wash the nickel fluoride by-product with hot water, add the washing wastewater to the pretreated etching waste liquid, and then add hydrofluoric acid to adjust the ratio of ammonium fluoride to hydrofluoric acid to 0.9-1.2:1. After the reaction, the reaction solution is obtained.

[0010] S4. Concentration: The reaction solution is concentrated to obtain a concentrated solution;

[0011] S5. Cooling: Cooling the concentrate.

[0012] S6. Centrifugation: Centrifuge the cooled concentrate to obtain ammonium bifluoride crystals and nickel-containing mother liquor. Reuse the nickel-containing mother liquor in step S1 to remove nickel again.

[0013] S7. Drying: The ammonium bifluoride crystals are dried to obtain the ammonium bifluoride product.

[0014] Furthermore, in step S1, the alkaline solution is ammonia water with a concentration of 10-20%.

[0015] Furthermore, in step S1, the temperature conditions for heating and stirring are 30–50°C, and the time is 0.5–1.5 h.

[0016] Furthermore, in step S1, the settling and aging process takes 5 to 6 hours.

[0017] Furthermore, in step S2, the centrifugation speed is 2500–3500 r / min.

[0018] Furthermore, in step S3, the temperature of the hot water is 50–60°C.

[0019] Furthermore, in step S3, the reaction temperature is 40–50°C and the reaction time is 25–35 min.

[0020] Furthermore, in step S4, the temperature conditions for the concentration treatment are 70–120°C, and the pressure conditions are -0.03–0.08 MPa.

[0021] Furthermore, in step S5, the cooling temperature is 5–20°C, and in step S6, the centrifugal speed is 2500–3500 r / min.

[0022] Furthermore, in step S7, the drying temperature is 60–80°C and the pressure is -1000–-1600 Pa.

[0023] The design principle of this invention is as follows:

[0024] Generally, Ni does not form complexes at pH less than 5, Ni forms complexes with anions at pH 5–12, and the complexes decompose and break down at pH greater than 12. The approach of this invention to eliminate the influence of nickel-ammonium complexes is not to treat ammonia nitrogen first, but rather to remove nickel in the initial pretreatment stage, where the waste liquid is already strongly acidic and nickel-ammonium complexes have not yet formed. This application adjusts the pH of the waste liquid to 3.5–4.0 by adding a small amount of alkali solution. Within this range, nickel-ammonium complexes will not form, but the acidity is reduced, allowing nickel fluoride to precipitate and be removed. However, the addition of alkali solution in this process can lead to localized over-alkali formation, resulting in the formation of nickel-ammonium complexes in certain areas. Therefore, this invention uses heating and stirring to avoid the formation of nickel-ammonium complexes due to localized over-alkali and accelerates the formation of nickel fluoride. Further, static aging promotes the growth of nickel fluoride crystals, ensuring effective separation from the waste liquid during subsequent centrifugation.

[0025] Based on the solubility characteristics, washing the nickel fluoride byproduct with hot water can remove ammonium fluoride and ammonium hydrogen fluoride. The resulting product is then mixed with the waste liquid for further treatment. Before adding hydrofluoric acid for adjustment, the content of ammonium fluoride and hydrofluoric acid in the waste liquid is tested, and the amount of hydrofluoric acid to be used is calculated. The two react to produce ammonium hydrogen fluoride. After concentration, although the residual nickel concentration increases slightly, the solubility of ammonium hydrogen fluoride varies significantly with temperature. Cooling and crystallization effectively separate the nickel-containing mother liquor and ammonium hydrogen fluoride crystals, yielding a qualified ammonium hydrogen fluoride product. The nickel-containing mother liquor is then returned to the pretreatment process for further defluorination. This method involves cyclical nickel removal, achieving continuous production of ammonium hydrogen fluoride while simultaneously regenerating and disposing of nickel.

[0026] The beneficial effects of this invention are reflected in:

[0027] This invention controls the precipitation of nickel fluoride by adjusting process conditions and uses pH control to address the impact of nickel-ammonium complexation on the precipitation method for treating nickel-containing etching waste liquid. This reduces the addition of auxiliary materials and environmental pollution, achieves resource recycling, and lowers production costs.

[0028] This invention abandons the use of flocculants (the use of flocculants will introduce impurity ions into the system. As a solution with high fluorine content, the metal ions in the flocculant will also form corresponding fluorides, affecting the quality of nickel fluoride products and reducing the recovery rate of heavy fluoride in waste liquid). Instead, it chooses to use a heating and aging process to allow nickel fluoride to stand and age before filtration, which can improve the recovery purity of nickel fluoride.

[0029] This invention adjusts the pH to acidic, therefore the recovery process involves evaporation and concentration to directly prepare ammonium bifluoride, i.e., acidic ammonium fluoride. Since the nickel removal treatment stage can reduce nickel content to below 100 ppm, a single crystallization step in the subsequent ammonium bifluoride synthesis process can achieve a finished product with an appearance conforming to national standards and a nickel content of less than 0.05%, without affecting product quality. This invention provides a simple and efficient solution to the problem of disposing of nickel-containing etching wastewater. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the resource recovery process for nickel-containing etching waste liquid according to the present invention.

[0031] Figure 2 This is a schematic diagram of the equipment structure for implementing the resource recovery treatment process of nickel-containing etching waste liquid according to the present invention.

[0032] Explanation of reference numerals in the attached diagram: 1 Waste liquid storage tank, 2 Pretreatment reactor, 3 Centrifuge, 4 By-product storage tank, 5 Main reactor, 6 Concentration reactor, 7 Cooler, 8 Centrifuge, 9 Cyclone separator, 10 Finished product storage tank. Detailed Implementation

[0033] See Figure 1 and Figure 2 To enable those skilled in the art to better understand the technical solutions described in this invention, the following embodiments are provided for illustration.

[0034] Unless otherwise specified, the raw materials, reagents or devices used in the following embodiments can be obtained from conventional commercial sources or by existing known methods; unless otherwise specified, the methods used in the embodiments of the present invention are methods mastered by those skilled in the art.

[0035] Example 1

[0036] The resource recovery process for nickel-containing etching waste liquid includes the following steps:

[0037] S1. Pretreatment: The nickel-containing etching waste liquid with ammonium fluoride concentration of 15.12%, hydrofluoric acid concentration of 14.09%, and nickel concentration of 5% in waste liquid storage tank 1 is passed into pretreatment reactor 2. Ammonia water with a concentration of 15% is added to adjust the pH value to 3.8. Then, the reaction is carried out at 35℃ and stirring speed of 120r / min for 1h, and then allowed to stand for aging treatment for 6h to obtain nickel fluoride turbid liquid.

[0038] S2. Centrifugation: The nickel fluoride turbid liquid is passed into centrifuge 3 and centrifuged at 3000 r / min. The solid obtained by centrifugation is nickel fluoride by-product, and the liquid obtained is the pretreated etching waste liquid. The nickel concentration was tested to be 95.06 ppm.

[0039] S3. Main reaction: The nickel fluoride by-product is cleaned with hot water at 50°C. The cleaned nickel fluoride by-product enters the by-product storage tank 4. The cleaning wastewater and the pretreated etching waste liquid are fed into the main reaction vessel 5. After detecting the content of ammonium fluoride and hydrofluoric acid in the waste liquid, hydrofluoric acid is added to adjust the ratio of ammonium fluoride to hydrofluoric acid to 1:1. Then, the reaction is carried out at 45°C for 30 minutes to obtain the reaction solution.

[0040] S4. Concentration: The reaction solution is passed into the concentration reactor 6 and concentrated at 0.02 MPa and 113 °C for 20 min to obtain a concentrated solution with an ammonium bifluoride mass concentration of 55.22%.

[0041] S5. Cooling: Pass the concentrate into cooler 7 and cool it to 20°C;

[0042] S6. Centrifugation: The cooled concentrate is fed into centrifuge 8 and centrifuged at 3000 r / min. The solid obtained by centrifugation is ammonium bifluoride crystals, and the liquid obtained is nickel-containing mother liquor with a nickel concentration of 175.86 ppm. The nickel-containing mother liquor is recycled to step S1 to remove nickel again.

[0043] S7. Drying: The ammonium bifluoride crystals are fed into the cyclone separator 9 and dried at -1500Pa and 70℃ until the moisture content is 0.1%. The resulting ammonium bifluoride product is then placed into the finished product storage tank 10. In this embodiment, the ammonium bifluoride product has an ammonium bifluoride content of 99.4%, a nickel content of 0.0053%, and a recovery rate of 99.5%.

[0044] Example 2

[0045] The resource recovery process for nickel-containing etching waste liquid includes the following steps:

[0046] S1. Pretreatment: The nickel-containing etching waste liquid with ammonium fluoride concentration of 8.14%, hydrofluoric acid concentration of 12.98%, and nickel concentration of 2.11% in waste liquid storage tank 1 is introduced into pretreatment reactor 2. Ammonia water with a concentration of 20% is added to adjust the pH value to 4.0. Then, the reaction is carried out at 30℃ and stirring speed of 130r / min for 1.5h, and then allowed to stand for aging for 5.5h to obtain nickel fluoride turbid liquid.

[0047] S2. Centrifugation: The nickel fluoride turbid liquid is passed into centrifuge 3 and centrifuged at 3500 r / min. The solid obtained by centrifugation is nickel fluoride by-product, and the liquid obtained is the pretreated etching waste liquid. The nickel concentration was tested to be 85.87 ppm.

[0048] S3. Main reaction: The nickel fluoride by-product is cleaned with hot water at 55℃. The cleaned nickel fluoride by-product enters the by-product storage tank 4. The cleaning wastewater and the pretreated etching waste liquid are fed into the main reaction vessel 5. After detecting the content of ammonium fluoride and hydrofluoric acid in the waste liquid, hydrofluoric acid is added to adjust the ratio of ammonium fluoride to hydrofluoric acid to 0.9:1. Then, the reaction is carried out at 40℃ for 35 minutes to obtain the reaction solution.

[0049] S4. Concentration: The reaction solution is passed into the concentration reactor 6 and concentrated at 0.08 MPa and 70°C for 60 min to obtain a concentrated solution with a mass concentration of 57.74% ammonium bifluoride.

[0050] S5. Cooling: Pass the concentrate into cooler 7 and cool it to 15°C;

[0051] S6. Centrifugation: The cooled concentrate is fed into centrifuge 8 and centrifuged at 3500 r / min. The solid obtained by centrifugation is ammonium bifluoride crystals, and the liquid obtained is nickel-containing mother liquor with a nickel concentration of 466.37 ppm. The nickel-containing mother liquor is recycled to step S1 to remove nickel again.

[0052] S7. Drying: The ammonium bifluoride crystals are fed into the cyclone separator 9 and dried at -1000Pa and 80℃ until the moisture content is 0.05%. The resulting ammonium bifluoride product is then sent to the finished product storage tank 10. In this embodiment, the ammonium bifluoride product has an ammonium bifluoride content of 99.8%, a nickel content of 0.014%, and a recovery rate of 99.9%.

[0053] Example 3

[0054] The resource recovery process for nickel-containing etching waste liquid includes the following steps:

[0055] S1. Pretreatment: The nickel-containing etching waste liquid with ammonium fluoride concentration of 15.50%, hydrofluoric acid concentration of 8.61%, and nickel concentration of 3.1% in waste liquid storage tank 1 is passed into pretreatment reactor 2. Ammonia water with a concentration of 10% is added to adjust the pH value to 3.5. Then, the reaction is carried out at 50℃ and stirring speed of 105r / min for 0.5h, and then allowed to stand for aging treatment for 5h to obtain nickel fluoride turbid liquid.

[0056] S2. Centrifugation: The nickel fluoride turbid liquid is passed into centrifuge 3 and centrifuged at 2500 r / min. The solid obtained by centrifugation is nickel fluoride by-product, and the liquid obtained is the pretreated etching waste liquid. The nickel concentration was tested to be 52.06 ppm.

[0057] S3. Main reaction: The nickel fluoride by-product is washed with hot water at 60℃. The washed nickel fluoride by-product enters the by-product storage tank 4. The washing wastewater and the pretreated etching waste liquid are fed into the main reaction vessel 5. After detecting the content of ammonium fluoride and hydrofluoric acid in the waste liquid, hydrofluoric acid is added to adjust the ratio of ammonium fluoride to hydrofluoric acid to 1.2:1. Then, the reaction is carried out at 50℃ for 25 minutes to obtain the reaction solution.

[0058] S4. Concentration: The reaction solution is passed into the concentration reaction vessel 6 and concentrated at -0.03MPa and 120℃ for 30 minutes to obtain a concentrated solution with an ammonium bifluoride mass concentration of 58.24%.

[0059] S5. Cooling: Pass the concentrate into cooler 7 and cool it to 5°C;

[0060] S6. Centrifugation: The cooled concentrate is fed into centrifuge 8 and centrifuged at 2500 r / min. The solid obtained by centrifugation is ammonium bifluoride crystals, and the liquid obtained is nickel-containing mother liquor with a nickel concentration of 198.99 ppm. The nickel-containing mother liquor is recycled to step S1 to remove nickel again.

[0061] S7. Drying: The ammonium bifluoride crystals are fed into the cyclone separator 9 and dried at -1600Pa and 60℃ until the moisture content is 0.1%. The resulting ammonium bifluoride product is then sent to the finished product storage tank 10. In this embodiment, the ammonium bifluoride product has an ammonium bifluoride content of 99.5%, a nickel content of 0.0060%, and a recovery rate of 99.6%.

[0062] Comparative Example 1

[0063] This comparative example was operated according to the same method as Example 1, except that the heating and stirring conditions in step S1 were omitted. After testing, the nickel concentration in the pretreated etching waste liquid was 2450 ppm. It can be seen that omitting heating and stirring affects the precipitation of nickel fluoride, significantly reducing the nickel removal effect.

[0064] Comparative Example 2

[0065] This comparative example was operated according to the same method as in Example 1, except that the static aging process was omitted in step S1. After testing, the nickel concentration in the pretreated etching waste liquid was 816 ppm. It can be seen that if the static aging process is omitted, nickel fluoride cannot form crystals well, affecting subsequent separation.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A resource-based treatment process for nickel-containing etching waste liquid, characterized in that, Includes the following steps: S1. Pretreatment: Add alkaline solution to nickel-containing etching waste liquid to adjust the pH value to 3.5-4.0, then heat and stir, and then let it stand and age to obtain nickel fluoride turbid liquid. The alkaline solution is ammonia water with a concentration of 10-20%; The heating and stirring treatment is carried out at a temperature of 30–50°C for 0.5–1.5 hours. S2. Centrifugation: Centrifuge the nickel fluoride turbid liquid to obtain nickel fluoride by-product and pretreated etching waste liquid. S3. Main reaction: Wash the nickel fluoride by-product with hot water, add the washing wastewater to the pretreated etching waste liquid, and then add hydrofluoric acid to adjust the ratio of ammonium fluoride to hydrofluoric acid to 0.9-1.2:

1. After the reaction, the reaction solution is obtained. S4. Concentration: The reaction solution is concentrated to obtain a concentrated solution; S5. Cooling: Cooling the concentrate. S6. Centrifugation: Centrifuge the cooled concentrate to obtain ammonium bifluoride crystals and nickel-containing mother liquor. Reuse the nickel-containing mother liquor in step S1 to remove nickel again. S7. Drying: The ammonium bifluoride crystals are dried to obtain the ammonium bifluoride product.

2. The resource recovery process for nickel-containing etching waste liquid as described in claim 1, characterized in that, In step S1, the settling and aging process takes 5 to 6 hours.

3. The resource recovery process for nickel-containing etching waste liquid as described in claim 1 or 2, characterized in that, In step S2, the centrifugation speed is 2500-3500 r / min.

4. The resource recovery process for nickel-containing etching waste liquid as described in claim 1 or 2, characterized in that, In step S3, the temperature of the hot water is 50-60℃.

5. The resource recovery process for nickel-containing etching waste liquid as described in claim 1 or 2, characterized in that, In step S3, the reaction temperature is 40–50°C and the reaction time is 25–35 min.

6. The resource recovery process for nickel-containing etching waste liquid as described in claim 1 or 2, characterized in that, In step S4, the temperature conditions for concentration treatment are 70 to 120°C, and the pressure conditions are -0.03 to 0.08 MPa.

7. The resource recovery process for nickel-containing etching waste liquid as described in claim 1 or 2, characterized in that, In step S5, the cooling temperature is 5–20°C, and in step S6, the centrifugation speed is 2500–3500 r / min.

8. The resource recovery process for nickel-containing etching waste liquid as described in claim 1 or 2, characterized in that, In step S7, the drying temperature is 60–80°C and the pressure is -1000–-1600 Pa.

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