Method for neutralizing acidic etching waste liquid

Abstract

The application provides a neutralization utilization method of acid etching waste liquid. The method comprises the following steps: mixing the acid etching waste liquid with an ammonium bicarbonate solution; in the mixing process, the temperature of the mixing is controlled to be 40-60 DEG C, and the pH value is adjusted to be 3.5-4.5 to obtain a slurry; the slurry is separated to obtain copper oxychloride wet crystals and an ammonium chloride crude product solution; the copper oxychloride wet crystals are subjected to dechlorination treatment by using an alkaline solution, and filtration is performed to obtain copper oxide filter cake and a chloride waste liquid; the temperature of the dechlorination treatment is 70-90 DEG C; the copper oxide filter cake is subjected to post-treatment to obtain copper sulfate; and the ammonium chloride crude product solution is subjected to precipitation treatment to obtain an ammonium chloride finished product solution. The steps S3 and S4 have no sequence. The method realizes the full utilization of the acid etching waste liquid cation and anion by using the ammonium bicarbonate, and prepares electroplating-grade copper sulfate and industrial-grade ammonium chloride products.

Description

Technical Field

[0001] This invention relates to the technical field of wastewater treatment in the printed circuit board industry, and specifically to a method for neutralizing and utilizing acidic etching waste liquid. Background Technology

[0002] The printed circuit board (PCB) industry, the foundation of the electronics manufacturing industry, generates a large amount of etching wastewater, mainly including three categories: acidic etching wastewater, alkaline etching wastewater, and micro-etching wastewater, with a daily national output of approximately 4,000 tons. With advancements in PCB technology and stricter regulations from national environmental protection departments regarding ammonia nitrogen in industrial wastewater, most PCB manufacturers have abandoned alkaline etching processes. Many older production lines that used alkaline etching solutions have also upgraded to include online recycling systems, significantly reducing the amount of alkaline etching wastewater circulating in the market awaiting treatment.

[0003] Traditional hazardous waste recycling companies commonly use a "waste-to-waste" process involving the combined treatment of acidic and alkaline etching solutions. This process produces basic copper chloride as a byproduct, with ammonium chloride as a secondary product. When the market demand for alkaline etching solutions is insufficient, ammonia is purchased to maintain production. However, this process is problematic. Firstly, the addition of ammonia requires additional investment in auxiliary materials, and its storage within the plant must be managed as an explosive. Secondly, the typical concentration of ammonia is 18%, which significantly reduces the concentration of the ammonium chloride filtrate produced by the original process, increasing downstream evaporation costs with the addition of ammonia.

[0004] When existing acidic and alkaline etching waste liquids are treated together, the neutralization reaction produces basic copper chloride wet crystals and an ammonium chloride solution containing a small amount of copper ions. The copper ions in the ammonium chloride solution are removed by ion exchange resin, and then the ion exchange resin is regenerated by high acid backwashing. The treatment facilities are large and the operation is complicated.

[0005] As the market faces difficulties in receiving alkaline etching solutions and competition among hazardous waste disposal companies intensifies, establishing a better comprehensive utilization process for acidic etching waste liquid requires a new process that can produce higher-value products to achieve the original process objectives, considering factors such as auxiliary material procurement, treatment process, and ease of operation. Summary of the Invention

[0006] To overcome the shortcomings of existing acid etching wastewater treatment processes, such as high cost, complex operation, and low product quality, this invention provides a method for neutralizing and utilizing acid etching wastewater. This method utilizes ammonium bicarbonate to achieve full utilization of the anions and cations in the acid etching wastewater; ammonium sulfide is used to remove impurity ions from the ammonium chloride solution, producing ammonium chloride product. The process of this invention can achieve a comprehensive copper recovery rate of over 99.8% and produce electroplating-grade copper sulfate and industrial-grade ammonium chloride products.

[0007] The present invention solves the above problems through the following technical solution:

[0008] This invention provides a method for neutralizing and utilizing acidic etching waste liquid, which includes the following steps:

[0009] S1. Mix the acidic etching waste liquid with the ammonium bicarbonate solution; during the mixing process, control the mixing temperature to 40-60℃ and adjust the pH value to 3.5-4.5 to obtain a slurry;

[0010] S2. Separate the slurry to obtain wet copper oxychloride crystals and crude ammonium chloride solution;

[0011] S3. The copper oxychloride wet crystals are dechlorinated using an alkaline solution, and the resulting copper oxide filter cake and chloride waste liquid are obtained by filtration; the temperature of the dechlorination treatment is 75-90℃.

[0012] The copper oxide filter cake is then post-processed to obtain copper sulfate;

[0013] S4. The crude ammonium chloride solution is subjected to precipitation treatment and filtration to obtain the finished ammonium chloride solution; the reagent for precipitation treatment is a saturated ammonium sulfide solution.

[0014] Steps S3 and S4 have no specific order.

[0015] In this invention, by mixing ammonium bicarbonate with acidic etching waste liquid, a milder neutralization reaction can occur, avoiding production risks caused by violent reactions; and, it can maintain a high copper content in the wet copper oxychloride crystals, and also reduce the entrainment of carbonate ions in the wet copper oxychloride crystals.

[0016] In step S1 of the present invention, when the pH value during the mixing process is too low, the wet copper oxychloride crystals in the slurry will be difficult to filter, and a large number of chloride ions will be carried in it; while when the pH value during the mixing process is too high, the filtration performance of the wet copper oxychloride crystals in the slurry will be better, but more copper ions will be attached to the crude ammonium chloride solution, increasing the cost of removing impurities from the crude ammonium chloride solution in the future.

[0017] In step S1 of the present invention, the amount of ammonium bicarbonate solution added can be determined by adjusting the pH value during the mixing process.

[0018] In some embodiments, step S1 includes mixing by adding the acidic etching waste liquid to the ammonium bicarbonate solution.

[0019] In step S1 of the present invention, when the mixing temperature is too low, the produced copper oxychloride wet crystals are difficult to filter due to poor crystal form; when the mixing temperature is too high, ammonium bicarbonate tends to decompose, reducing the effect of the neutralization reaction and also increasing energy consumption.

[0020] In a specific implementation, in step S1, the temperature of the ammonium bicarbonate solution is 40-60°C, for example, 50°C.

[0021] In some implementations, the mixing process in step S1 is carried out under constant temperature conditions.

[0022] In a specific implementation, in step S1, the ammonium bicarbonate solution is a supersaturated suspension prepared from solid ammonium bicarbonate and a solvent; the solvent includes tap water or the crude ammonium chloride solution in step S2.

[0023] Ammonium bicarbonate is a white, water-soluble crystal with a slight ammonia odor. Its ammonium content is 22.8%, and its unit ammonium purchase cost is 40% lower than that of ammonia solution. It is also more convenient to transport and store than ammonia solution. Its dissolution process is strongly endothermic, and the ammonia odor is significantly reduced when the solution is slightly acidic.

[0024] In step S1 of the present invention, those skilled in the art should understand that the acidic etching waste liquid is conventional in the art, and it contains copper chloride, and the copper ions in the copper chloride need to be recycled.

[0025] In some embodiments, the acidic etching waste liquid specifically refers to the strongly acidic waste liquid produced in the PCB printed circuit board industry, which contains Cu, Cl, Na and Fe elements.

[0026] In some embodiments, in step S1, the density of the acidic etching waste liquid is 1–1.3 g / cm³. 3 .

[0027] In some embodiments, in step S1, the COD value of the acidic etching waste liquid is 3000 to 15000 ppm.

[0028] In some embodiments, in step S1, the acidity of the acidic etching waste liquid is 1 to 6 mmol / g.

[0029] In step S1 of the present invention, during the mixing process, alkaline etching waste liquid may be introduced to replace part of the ammonium bicarbonate solution.

[0030] In some implementations, the separation method in step S2 includes filtration.

[0031] In step S2 of the present invention, the crude ammonium chloride solution contains copper ions.

[0032] In some embodiments, in step S2, when the copper content in the crude ammonium chloride solution is ≥1000ppm, the crude ammonium chloride solution is returned to step S1 to be mixed and reacted with the acidic etching waste liquid.

[0033] In step S2 of the present invention, the residual amount of copper ions in the crude ammonium chloride solution can be preliminarily assessed by monitoring the color of the crude ammonium chloride solution; when the crude ammonium chloride solution is light blue, the copper content is <1000ppm, and when the crude ammonium chloride solution is bluish-green, the copper content is ≥1000ppm.

[0034] In step S3 of the present invention, the dechlorination process converts wet copper oxychloride crystals into copper oxide precipitate and separates copper from chlorine.

[0035] In some embodiments, in step S3, the alkaline solution includes liquid alkali.

[0036] In a specific implementation, the concentration of the liquid alkali is 30%, where % refers to the proportion of the mass of NaOH to the total mass of the liquid alkali.

[0037] In a specific embodiment, the mass ratio of the added liquid alkali to the wet copper oxychloride crystals is (0.5-0.6):1.

[0038] In some embodiments, the temperature of the dechlorination treatment in step S3 is 85–90°C.

[0039] In some embodiments, the dechlorination treatment in step S3 takes 20 to 40 minutes.

[0040] In some embodiments, in step S3, the final pH value of the dechlorination treatment of the copper oxychloride wet crystals is controlled to be 10-12.

[0041] In a specific embodiment, after the pH value of the wet copper oxychloride crystals reaches the endpoint pH value, the reaction continues for another 15 minutes to ensure that all the wet copper oxychloride crystals are converted.

[0042] In some embodiments, in step S3, after the filtration step, the copper oxide filter cake is rinsed.

[0043] In some embodiments, step S3 includes acid hydrolysis, hot filtration, evaporation, concentration, and crystallization; wherein the post-treatment process satisfies one or more of the following conditions:

[0044] ①The reagent used for the acidolysis treatment is a sulfuric acid solution;

[0045] ② The final pH value of the acid hydrolysis treatment of the copper oxide filter cake is controlled to be 4-5;

[0046] ③ The acid hydrolysis treatment temperature is 60-80℃.

[0047] In a specific implementation, the sulfuric acid solution may be sourced from waste sulfuric acid from chip manufacturing companies.

[0048] In a specific embodiment, the sulfuric acid solution may consist of 70% sulfuric acid and water, with a mass ratio of sulfuric acid to water of 1:(3-4).

[0049] In step S3 of the present invention, during the post-processing, the concentration of copper ions in the solution at the end of the post-processing is controlled to be no greater than 80 g / L, so as to avoid the precipitation of copper ions due to natural crystallization.

[0050] In step S3 of the present invention, the copper sulfate is an electroplating grade copper sulfate product.

[0051] In some embodiments, step S4 includes immersing the reagent for precipitation treatment into the crude ammonium chloride solution.

[0052] In some embodiments, in step S4, the amount of ammonium sulfide saturated solution added is 0.5%, where % is the proportion of the volume of the ammonium sulfide saturated solution to the total volume of the crude ammonium chloride solution.

[0053] In step S4 of the present invention, ammonium sulfide in the saturated ammonium sulfide solution acts as a precipitant to precipitate heavy metal ions.

[0054] In step S4 of the present invention, ammonium sulfide is used to precipitate the various metal ions remaining in the crude ammonium chloride solution, avoiding the use of ion exchange resin to treat the crude ammonium chloride solution containing a small amount of copper ions. This treatment method is simpler to operate and the system investment is further reduced.

[0055] In step S4 of the present invention, the crude ammonium chloride solution rapidly changes from blue to black through the precipitation treatment.

[0056] In some embodiments, the precipitation treatment time in step S4 is 10 to 25 minutes.

[0057] In step S4 of the present invention, the filtration process is odorless throughout, and an almost colorless and transparent ammonium chloride solution and copper sulfide precipitate are obtained.

[0058] In some embodiments, in step S4, the ammonium chloride product solution is sequentially evaporated, concentrated, and crystallized to obtain ammonium chloride solid.

[0059] In step S4 of the present invention, the ammonium chloride solid is an industrial-grade ammonium chloride product.

[0060] In this invention, the neutralization and utilization method of the acidic etching waste liquid can eliminate the need to purchase ammonia water when there is insufficient alkaline etching waste liquid available on the market, and will not increase the amount of ammonium chloride solution evaporation treatment at the back end of the system, while still being compatible with the co-treatment requirements of a small amount of alkaline etching waste liquid.

[0061] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0062] The reagents and raw materials used in this invention are all commercially available.

[0063] The positive and progressive effects of this invention are as follows:

[0064] 1. This invention replaces alkaline etching waste liquid with ammonium bicarbonate and neutralizes it with acidic etching waste liquid, thereby achieving a comprehensive copper recovery rate of over 99.8% and producing electroplating-grade copper sulfate and industrial-grade ammonium chloride products.

[0065] 2. This invention provides a comprehensive resource utilization process for anions and cations in acidic etching waste liquid, which is widely adaptable, has low treatment costs, simple operation procedures, good operating environment, readily available reagents, and high product value. The resource utilization products are electroplating grade copper sulfate and national standard ammonium chloride solids, and the discharged wastewater is crystallization evaporation distillate condensate, which meets the requirements for direct discharge to general sewage treatment plants / plants. Attached Figure Description

[0066] Figure 1 This is a process flow diagram of the neutralization and utilization method of acidic etching waste liquid in Embodiment 1 of the present invention. Detailed Implementation

[0067] The following detailed description, in conjunction with the accompanying drawings, illustrates a method for neutralizing and utilizing acidic etching waste liquid with ammonium salts. These examples do not constitute a limitation of the present invention.

[0068] Table 1 shows the composition and properties of the acidic etching waste liquid in Example 1 and Comparative Examples 1-4.

[0069] Table 1

[0070]

[0071] Example 1

[0072] This embodiment provides a method for neutralizing and utilizing acidic etching waste liquid. Figure 1 This is a process flow diagram of the neutralization and utilization method of acidic etching waste liquid in this embodiment.

[0073] The method for neutralizing and utilizing the acidic etching waste liquid includes the following steps:

[0074] S1: Place 1000g of solid ammonium bicarbonate in a 5L beaker, add water, and dissolve it in a water bath at a constant temperature of 50℃; slowly add acidic etching waste liquid to the ammonium bicarbonate solution, controlling the mixing temperature at 50℃; take an appropriate amount of the reaction slurry in a small beaker and let it stand, observe that the color of the supernatant turns light blue, and at this time, detect the pH of the solution. When the pH shows about 4.0, stop adding acidic etching waste liquid to stop the neutralization reaction and obtain the slurry;

[0075] S2: Let the slurry obtained in step S1 stand for 5-10 minutes, and filter it with a Buchner funnel; to obtain wet copper oxychloride crystals and a crude ammonium chloride solution containing a small amount of copper, the solution is transparent and light blue; the crude ammonium chloride solution can be used as a solvent to dissolve the ammonium bicarbonate solid in step S1.

[0076] S3: Add 0.5 to 0.6 times the mass of 30% liquid alkali to the wet copper oxychloride crystals obtained in step S2, heat to 90℃ for high-temperature conversion for 40 minutes, and carry out dechlorination treatment. The final pH value of the dechlorination treatment is controlled in the range of 10 to 12. Filter while hot to obtain copper oxide filter cake and sodium chloride waste liquid.

[0077] S4: The copper oxide filter cake obtained above is rinsed and then heated to 80°C with an equal mass of 70% sulfuric acid and 4 times the mass of tap water to acid dissolve it. The insoluble matter is filtered out while hot. The pH of the clear liquid after dissolution is controlled between 4 and 5 by adding appropriate copper oxide mud. Pure copper sulfate solution and a small amount of acid-insoluble matter are obtained by filtration. The pure copper sulfate solution is simply evaporated and concentrated to obtain 720g of copper sulfate product. The sample test and analysis report is shown in Table 2 below. Table 2 shows the composition of the copper sulfate product.

[0078] Table 2

[0079]

[0080]

[0081] S5: Take 2.5L of the light blue crude ammonium chloride solution containing copper ions obtained by filtration in step S2. Use a pipette to immerse 12.5mL of the prepared saturated ammonium sulfide solution into the crude ammonium chloride solution containing copper ions. Stir appropriately with a glass rod. The solution quickly changes from light blue to a solid suspension with black suspended matter. Continue stirring and react for 25min. Filter to obtain a small amount of black filter cake, which is copper sulfide. The filtrate is colorless, which is the finished ammonium chloride solution. Take samples of the finished ammonium chloride solution for analysis, as shown in Table 3 below. Table 3 shows the elemental composition of the finished ammonium chloride solution.

[0082] Table 3

[0083]

[0084] S6: Evaporate, concentrate and crystallize the ammonium chloride product solution obtained in step S5 to obtain industrial-grade ammonium chloride solid. The sample analysis report of the ammonium chloride solid is shown in Table 4 below. Table 4 shows the composition of the ammonium chloride solid.

[0085] Table 4

[0086]

[0087]

[0088] As shown in Tables 1-4 above, the method of this embodiment can produce electroplating grade copper sulfate and industrial grade ammonium chloride products.

[0089] In addition, the above-mentioned method can achieve a comprehensive copper recovery rate of over 99.8%.

[0090] This embodiment provides a comprehensive resource utilization process for anions and cations in acidic etching waste liquid, which is widely adaptable, has low treatment costs, simple operation procedures, good operating environment, readily available reagents, and high product value. The resource products are electroplating grade copper sulfate and national standard ammonium chloride solids, and the discharged wastewater is crystallization evaporation distillate condensate, which meets the requirements for direct discharge to general sewage treatment plants / stations.

[0091] Comparative Example 1:

[0092] This comparative example discloses a method for neutralizing and utilizing acidic etching waste liquid.

[0093] The comparative example adjusts step S1 of Example 1, specifically:

[0094] According to the operating steps of Example 1, the water bath environment involved in step S1 is removed. When preparing ammonium bicarbonate, its temperature is lower than 40°C due to the endothermic process. The mixing temperature of acidic etching waste liquid and ammonium bicarbonate solution is also lower than 40°C. Although the acidic etching waste liquid can still react with ammonium bicarbonate solution, the suspension after the reaction cannot be filtered, and the slurry formed cannot be naturally settled and separated.

[0095] Therefore, electroplating-grade copper sulfate and national standard ammonium chloride solids cannot be obtained through the subsequent processes of Example 1.

[0096] Comparative Example 2:

[0097] This comparative example discloses a method for neutralizing and utilizing acidic etching waste liquid.

[0098] The comparative example adjusts step S1 of Example 1, specifically:

[0099] Following the operating steps of Example 1, when the water bath environment involved in step S1 was raised to 70°C, it was found that the entire operating environment was filled with the smell of decomposed ammonia when no acidic etching waste liquid was added, resulting in an extremely poor operating environment.

[0100] The excessively high mixing temperature caused the ammonium bicarbonate to decompose, severely impacting the operating environment and reducing its neutralization effect.

[0101] Comparative Example 3:

[0102] This comparative example discloses a method for neutralizing and utilizing acidic etching waste liquid.

[0103] The comparative example adjusts steps S1, S2, and S5 of Example 1, specifically:

[0104] Following the operation process of step S1 in Example 1, the reaction endpoint of neutralizing ammonium bicarbonate in the acidic etching waste liquid is controlled to a pH value of approximately 5, and the addition of acidic etching waste liquid is stopped.

[0105] Following the procedure in step S2 of Example 1, the supernatant obtained after filtration (a crude ammonium chloride solution containing a small amount of copper) was sapphire blue; the degree of separation between the filter cake and the filtrate was tested, and the residual copper content in the filtrate was 3400 ppm;

[0106] According to the operation process of step S5 in Example 1, 4% by volume of saturated ammonium sulfide solution was added to remove excess metal ions from the bright blue ammonium chloride filtrate. Although the filtrate color was clarified, the amount of ammonium sulfide added was too large, resulting in a very strong odor in the solution, making it difficult to operate and affecting the operating environment.

[0107] Comparative Example 4:

[0108] This comparative example discloses a method for neutralizing and utilizing acidic etching waste liquid.

[0109] The comparative example adjusts step S3 of Example 1, specifically:

[0110] Following the procedure in step S3 of Example 1, the temperature for adding 30% liquid alkali to copper oxychloride in step S3 was set to 70°C (i.e., the dechlorination treatment temperature). After continuous stirring for 1 hour, the slurry remained light blue with only a small amount of gray showing. Filtration of the slurry after conversion was difficult, making further separation of copper and chlorine impossible. Therefore, electroplating-grade copper sulfate could not be obtained through the subsequent process of Example 1.

[0111] It should be noted that the implementation scheme provided by this invention is only an optimized way to achieve the desired effect and does not constitute a limitation on the invention itself.

[0112] The foregoing describes the process objective, basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims.

Claims

1. A method for neutralizing and utilizing acidic etching waste liquid, characterized in that, It includes the following steps: S1. Mixing acidic etching waste liquid with ammonium bicarbonate solution; the mixing method includes: adding the acidic etching waste liquid to the ammonium bicarbonate solution; the mixing process is carried out under constant temperature conditions; during the mixing process, the mixing temperature is controlled at 40~60℃, and the pH value is adjusted to 3.5~4.5 to obtain a slurry; the ammonium bicarbonate solution is a supersaturated suspension prepared from solid ammonium bicarbonate and solvent; S2. Separate the slurry to obtain wet copper oxychloride crystals and crude ammonium chloride solution; S3. The copper oxychloride wet crystals are dechlorinated using an alkaline solution, and the resulting copper oxide filter cake and chloride waste liquid are obtained by filtration; the temperature of the dechlorination treatment is 75~90℃; The copper oxide filter cake is then post-processed to obtain copper sulfate; S4. The crude ammonium chloride solution is subjected to precipitation treatment and filtration to obtain the finished ammonium chloride solution; the reagent for precipitation treatment is a saturated ammonium sulfide solution. Steps S3 and S4 have no specific order.

2. The method for neutralizing and utilizing acidic etching waste liquid as described in claim 1, characterized in that, Step S1 satisfies one or two of the following conditions: ① The temperature of the ammonium bicarbonate solution is 40~60℃; ②The solvent includes tap water or the crude ammonium chloride solution from step S2.

3. The method for neutralizing and utilizing acidic etching waste liquid as described in claim 1, characterized in that, In step S1, the acidic etching waste liquid meets one or more of the following conditions: ①The acidic etching waste liquid is a strongly acidic waste liquid containing Cu, Cl, Na and Fe elements produced in the PCB printed circuit board industry; ② The density of the acidic etching waste liquid is 1~1.3 g / cm³. 3 ; ③ The COD value of the acidic etching waste liquid is 3000~15000 ppm; ④ The acidity of the acidic etching waste liquid is 1~6 mmol / g.

4. The method for neutralizing and utilizing acidic etching waste liquid as described in claim 1, characterized in that, In step S2, the separation method includes vacuum filtration.

5. The method for neutralizing and utilizing acidic etching waste liquid as described in claim 1, characterized in that, In step S2, when the copper content in the crude ammonium chloride solution is ≥1000ppm, the crude ammonium chloride solution is returned to step S1 and mixed with the acidic etching waste liquid for reaction.

6. The method for neutralizing and utilizing acidic etching waste liquid as described in claim 1, characterized in that, Step S3 satisfies one or more of the following conditions: ①The alkaline solution includes liquid alkali; ② The dechlorination treatment temperature is 85~90℃; ③ The dechlorination treatment time is 20~40 min; ④ The final pH value of the dechlorination treatment of the copper oxychloride wet crystals is controlled to be 10~12; ⑤ After the filtration step, the copper oxide filter cake is rinsed.

7. The method for neutralizing and utilizing acidic etching waste liquid as described in claim 6, characterized in that, The concentration of the liquid alkali is 30%, where % refers to the proportion of the mass of NaOH to the total mass of the liquid alkali. The mass ratio of the added liquid alkali to the wet copper oxychloride crystals is (0.5~0.6):

1.

8. The method for neutralizing and utilizing acidic etching waste liquid as described in claim 1, characterized in that, In step S3, the post-processing includes acid hydrolysis, hot filtration, evaporation, concentration, and crystallization; wherein the post-processing meets one or more of the following conditions: ①The reagent used for the acidolysis treatment is a sulfuric acid solution; ② The final pH value of the acid hydrolysis treatment of the copper oxide filter cake is controlled to be 4~5; ③ The acid hydrolysis treatment temperature is 60~80℃.

9. The method for neutralizing and utilizing acidic etching waste liquid as described in claim 1, characterized in that, Step S4 satisfies one or more of the following conditions: ①The precipitation treatment method includes: adding the precipitation treatment reagent dropwise into the crude ammonium chloride solution by immersion; ② The amount of ammonium sulfide saturated solution added is 0.5%, where % is the proportion of the volume of the ammonium sulfide saturated solution to the total volume of the crude ammonium chloride solution; ③ The precipitation treatment time is 10~25 min; ④ The ammonium chloride solution is successively evaporated, concentrated, and crystallized to obtain solid ammonium chloride.

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