A method for recycling acidic etching waste

Abstract

The present application relates to the field of recycling technology of etching waste, and specifically discloses a recycling method of acidic etching waste, including the following steps: S100 water washing: adding deionized water to the sediment in proportion, fully dissolving the soluble substances in the sediment at a temperature of 55-75°C; S200 pickling: removing the filter residue after water washing, adding hydrochloric acid, adjusting the pH to 1.8-3.5, reacting to generate calcium fluoride precipitation, and obtaining calcium fluoride after washing and drying; S300 neutralization: adding sodium hydroxide to the pickling filtrate, adjusting the pH to 9-10, reacting to generate strontium hydroxide precipitation, and obtaining strontium hydroxide after washing and drying; S400 double decomposition reaction: using hydrochloric acid to adjust the pH to 7-8, adding ammonium fluoride to the solution, reacting to generate barium fluoride precipitation, and obtaining barium fluoride after washing and drying. The purpose of this patent is to solve the problems that the stage semiconductor etching waste liquid sediment is often mixed with a large amount of impurities, and there are problems such as high difficulty in separation and purification, great difficulty in recycling, and complex recycling process.

Description

Technical Field

[0001] The invention relates to the technical field of recycling etching waste materials, and in particular to a recycling method for acidic etching waste materials. Background Art

[0002] In modern industrial production, especially in high-tech fields such as semiconductor manufacturing, etching processes play a vital role. As a by-product of this process, the sediments in the etching waste liquid have attracted widespread attention. As the chemical substances in the etching solution continue to react with the etched material, accompanied by fluctuations in temperature, concentration and other conditions, the solute is very easy to reach a supersaturated state, and then precipitate from the waste liquid to form solid substances, which we call sediments. Its composition is highly complex, which mainly depends on the chemical formula used in the etching process and the characteristics of the etched material. Taking semiconductor etching as an example, in semiconductor etching, if a fluoride-containing etching solution is used to etch silicon wafers, the sediment may contain components such as silicon fluoride. When the etching object is transformed into a metal material, semiconductor etching metal usually uses an acidic etching solution, such as a mixture of hydrofluoric acid and ammonium fluoride as an etching solution, or a sulfuric acid etching solution, etc. The sediments produced during the semiconductor metal etching process are likely to contain fluorides, sulfates, etc.

[0003] These sediments are not worthless industrial waste. From the perspective of resource recycling and economic benefits, it is of great significance to reasonably recycle the components in the sediments. For example, semiconductor etching waste liquid is usually a mixed liquid containing calcium fluoride, barium fluoride, strontium fluoride, hydrofluoric acid and other components. The content of calcium fluoride and barium fluoride in the sediment of the mixed liquid is relatively high, and it has recycling value. Although the content of strontium is limited, it is also worth recycling as a rare element. However, due to the large number of types of substances contained in the mixed liquid, it is difficult to separate and purify various substances. The existing methods for etching waste of this content mainly recycle barium fluoride with a high content and relatively high economic value. Therefore, it is urgent to study a separation process to achieve the separation and recovery of calcium fluoride, barium fluoride, and strontium fluoride, and solve the problems of difficulty in recycling etching waste liquid, complexity of existing recycling processes, and inability to achieve simultaneous recovery of multiple substances. Summary of the invention

[0004] In view of the shortcomings of the prior art, the technical problem solved by the present invention is to provide a method for resource recovery of acid etching waste, so as to solve the problems that the current semiconductor etching waste liquid sediment is often mixed with a large amount of impurities, which makes separation and purification difficult, recycling difficult, and the recycling process complicated.

[0005] In order to solve the above problems, the technical solution adopted by the present invention is: a resource recovery method for acidic etching waste, wherein the etching waste is a mixture including calcium fluoride, barium fluoride, strontium fluoride and hydrofluoric acid, and the method comprises the following steps:

[0006] S100 water washing: filter the residue to obtain sediment, add deionized water to the sediment in proportion, and fully dissolve the soluble substances in the sediment at a temperature of 55-75°C;

[0007] S200 acid washing: remove the filter residue after washing with water, add hydrochloric acid, adjust the pH to 1.8-3.5, wash and dry the remaining precipitate to obtain calcium fluoride;

[0008] S300 neutralization: sodium hydroxide is added to the acid-washed filtrate to adjust the pH to 9-10, and strontium hydroxide precipitate is generated by reaction, and strontium hydroxide is obtained after washing and drying;

[0009] S400 double decomposition reaction: Use hydrochloric acid to adjust the pH to 7-8, add ammonium fluoride to the solution, react to generate barium fluoride precipitate, and then wash and dry to obtain barium fluoride.

[0010] The technical principle and beneficial effects of the scheme are as follows: the scheme recovers calcium fluoride, barium fluoride, strontium and other substances in the sediment through water washing, acid washing, neutralization and double decomposition reaction. First, soluble substances such as hydrofluoric acid, magnesium sulfate and aluminum sulfate in the sediment are removed by water washing; then, barium fluoride and strontium fluoride in the filter residue after water washing are dissolved in the solution at room temperature by acid washing, and then the remaining undissolved substances, namely calcium fluoride and aluminum fluoride, are washed and dried. After acid washing and water washing again, the aluminum ions in the precipitate are reduced, and the precipitate is mainly calcium fluoride; then, the filtrate after acid washing is neutralized. Since the reaction sequence is mainly determined by the equilibrium constant of the precipitation dissolution equilibrium, that is, the solubility product constant, strontium hydroxide with a smaller solubility product constant is precipitated first, and by controlling the pH value of the reaction solution, the reaction process is controlled to mainly generate strontium hydroxide precipitate, so that in the presence of barium ions, high-purity separation of strontium hydroxide is achieved to obtain strontium hydroxide precipitate; finally, barium fluoride is obtained by double decomposition reaction.

[0011] The sediment of semiconductor etching waste liquid is recovered by this scheme, and the efficient and high-quality recovery of calcium fluoride, barium fluoride, strontium and other substances in the sediment is achieved. In the existing scheme, when strontium ions and barium ions exist at the same time, strontium hydroxide and barium hydroxide precipitates will be formed after adding sodium hydroxide, and the barium hydroxide content is high, which makes it difficult to separate the strontium hydroxide precipitate from the generated precipitate. Therefore, based on this technical bias of the prior art, when facing the separation and purification of barium and strontium, alkaline precipitation is usually not used for the separation of barium, and sulfuric acid is generally used to generate barium sulfate for precipitation; while this scheme controls the precipitation conditions, that is, controls the pH value of the solution, and achieves the separation of strontium hydroxide with high purity in the presence of barium ions.

[0012] According to experimental tests, the purity of calcium fluoride obtained in this embodiment is more than 95%, the purity of strontium hydroxide is more than 98%, and the purity of barium fluoride is 98.5%. These high-purity products can be directly applied to multiple industrial fields, such as chemical raw materials, electronic materials, etc., realizing the high-value utilization of waste and reducing environmental pollution. In addition, the recycling process of this scheme is simple, and the recycling of calcium fluoride, barium fluoride and strontium hydroxide can be completed through four main steps.

[0013] Furthermore, deionized water is added in the step S100 at a solid-liquid ratio of 1:2.5-1:3.5. By controlling the optimal solid-liquid ratio, it can be ensured that soluble salts such as hydrofluoric acid, magnesium sulfate, and aluminum sulfate are efficiently eluted and enter the water phase during the water washing process, which can reduce the waste of water resources while ensuring the recovery efficiency.

[0014] Furthermore, the reaction time of step S100 or step S200 is 55-65 minutes. By controlling the optimal duration of water washing and acid washing, it is possible to ensure that the best washing effect is achieved in the shortest time, thereby improving the recovery efficiency. This helps to remove impurities in the sediment, thereby improving the purity and quality of the recovered product.

[0015] Furthermore, the washing in step S200 or step S300 or step S400 is performed with deionized water, and the solid-liquid ratio of deionized water to the precipitate is 1:2.5-1:3.5. The impurities in the precipitate are further reduced by washing with deionized water, and the content of the target substance in the precipitate is increased.

[0016] Furthermore, the temperature in step S100 is 60° C. Through precise temperature control, energy consumption and water resource waste can also be reduced. Compared with blindly using high-temperature water or normal temperature water for washing, operating within the optimal temperature range can not only meet the need for dissolving impurities, but also reduce production costs to a certain extent.

[0017] Furthermore, the concentrations of the hydrochloric acid and sodium hydroxide solutions are both 3 mol / L. The hydrochloric acid concentration of 3 mol / L is relatively easy to prepare and does not require excessive raw material input; at the same time, compared with high-concentration hydrochloric acid, its danger is relatively low. At this concentration, hydrochloric acid can selectively dissolve some target substances, while having little effect on other substances that need to be retained. For example, there may be multiple metal compounds in the sediment at the same time. 3 mol / L hydrochloric acid can preferentially dissolve those metal compounds with higher activity according to their chemical activity differences, thereby achieving the purpose of separation and purification. Selectivity in recovering specific valuable components such as calcium fluoride can avoid excessive pickling and loss of target components. When the sodium hydroxide solution reacts with the acidic solution containing strontium ions, the concentration of 3 mol / L can well control the formation of precipitation. If the sodium hydroxide concentration is too high, it may cause the precipitation to form quickly and agglomerate, affecting the purity of the precipitation and subsequent separation; if the concentration is too low, the target metal ions may not be completely precipitated. At this concentration, the metal ions can gradually react with the hydroxide ions to generate a precipitate with uniform particles and high purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The figure is a flow chart of the steps of the method of the present invention. DETAILED DESCRIPTION

[0019] The following is further described in detail through specific implementation methods:

[0020] The material in this embodiment comes from the sediment deposited from a large semiconductor etching waste liquid in Shenzhen, and its main components are barium fluoride, calcium fluoride, etc. The test data are shown in Table 1 below;

[0021] Table 1 Content of each component in sediment

[0022]

[0023] The flow chart of this method is basically as shown in the attached Figure 1 As shown:

[0024] A method for recycling acidic etching waste, comprising the following steps:

[0025] S100 water washing: add 300 ml of deionized water to 100 g of sediment at a solid-liquid ratio of 1:3, and react at 60°C for 60 minutes to fully dissolve the soluble substances in the sediment;

[0026] S200 acid washing: remove the filter residue after washing, add 3 mol / L hydrochloric acid, adjust the pH to 2.4, react at room temperature for 60 minutes to generate calcium fluoride precipitation, and obtain calcium fluoride after washing and drying;

[0027] S300 neutralization: add 3 mol / L sodium hydroxide to the acid-washed filtrate to adjust the pH to 9.6, react to generate strontium hydroxide precipitate, and then wash and dry to obtain strontium hydroxide;

[0028] S400 double decomposition reaction: Use hydrochloric acid to adjust the pH to 7.6, and gradually add ammonium fluoride solution to the solution until no white precipitate is generated in the supernatant. The reaction generates barium fluoride precipitate, which is then washed and dried to obtain barium fluoride.

[0029] This scheme recovers organic substances such as calcium fluoride, barium fluoride, and strontium in the sediment through water washing, acid washing, neutralization, and double decomposition reaction. First, soluble substances such as hydrofluoric acid, magnesium sulfate, and aluminum sulfate in the sediment are removed by water washing; then, barium fluoride and strontium fluoride in the filter residue after water washing are dissolved in the solution at room temperature by acid washing, and then the remaining undissolved substances such as calcium fluoride and aluminum fluoride are washed and dried. After acid washing and water washing again, the aluminum ions in the precipitate are reduced, and the precipitate is mainly calcium fluoride; then, the filtrate after acid washing is neutralized, and the pH value of the reaction solution is controlled to control the reaction process to mainly generate strontium hydroxide precipitation, so that in the presence of barium ions, high-purity separation of strontium hydroxide is achieved; finally, barium fluoride is obtained through double decomposition reaction.

[0030] The present invention is used to recover the sediment of semiconductor etching waste liquid, thereby realizing efficient and high-quality recovery of organic substances such as calcium fluoride, barium fluoride and strontium in the sediment. According to experimental tests, the purity of calcium fluoride prepared in this embodiment is 95%, the purity of strontium hydroxide is 98.4%, and the purity of barium fluoride is 99%.

[0031] Through the following experiments, the optimal experimental parameters of the experimental parameters of each step of this scheme are verified respectively.

[0032] 1. Washing

[0033] (1) Take 100g of sediment from each of the three groups numbered 1, 2, 3, 4, and 5 as shown in Table 1, add 100mL, 200ml, 300ml, 500ml, and 1000ml of deionized water to the sediment respectively, stir thoroughly in 60℃ water, and react for 60 minutes. Test the contents of hydrofluoric acid, magnesium sulfate, and aluminum sulfate in the sediment respectively.

[0034] Table 2 Changes in characteristic ion concentrations in water-washed solid-liquid ratio and water-washed residue

[0035]

[0036] (2) Take 100g of sediments from each of the three groups numbered 6, 7, 8, 9, and 10, add 300ml of deionized water to the sediments, and control the temperature at 20℃, 40℃, 60℃, 80℃, and 100℃, respectively. The reaction time is 60 minutes, and the contents of hydrofluoric acid, magnesium sulfate, and aluminum sulfate in the sediments are tested respectively.

[0037] Table 3 Comparison of washing temperature with changes in characteristic ion concentration in washed residue

[0038]

[0039] (3) Take 100g of sediments and add 300ml of deionized water to the sediments in 5 groups numbered 11, 12, 13, 14, and 15 respectively, and control the temperature at 60°C. The reaction time is 15 minutes, 30 minutes, 60 minutes, and 120 minutes, and the contents of hydrofluoric acid, magnesium sulfate, and aluminum sulfate in the sediments are tested respectively.

[0040] Table 4 Comparison of washing time with changes in characteristic ion concentration in washed residue

[0041]

[0042] From the above experiments, it can be seen that when the solid-liquid ratio is 1:3, the reaction temperature is 60°C, and the reaction time is 60 minutes, the water washing effect is better.

[0043] 2. Pickling

[0044] (1) After washing, take 5 portions of the washed residue, adjust the pH to 6-5, 5-4, 4-3, 3-2, and 2-1 with 3 mol / L hydrochloric acid, and set control groups 16, 17, 18, 19, and 20. Set the acid washing time to 60 minutes. After acid washing, filter, take the residue, wash it with deionized water with a solid-liquid ratio of 1:3, and then dry it. Determine the content of calcium fluoride in the residue.

[0045] Table 6 Effect of pickling pH ratio on calcium fluoride content in pickling residue

[0046]

[0047] The data show that the reaction time is 60 minutes. As the pH content decreases, the residue mass decreases and the purity of calcium fluoride increases. When the pH is between 2 and 3, the calcium fluoride content is 95%.

[0048] (2) After washing, take 5 portions of the washed residue, adjust the pH to 2-3 with 3 mol / L hydrochloric acid, and set the reaction time to 15 minutes, 30 minutes, 60 minutes, 80 minutes, and 120 minutes to set control groups 21, 22, 23, 24, and 25. After acid washing, filter, take the residue, wash it with deionized water with a solid-liquid ratio of 1:3, and then dry it. Determine the content of calcium fluoride in the residue.

[0049] Table 7 Effect of pickling time ratio on calcium fluoride content in pickling residue

[0050]

[0051] According to laboratory data, the best conditions for acid washing are pH 2-3 and the reaction time is 60 minutes to achieve the best effect.

[0052] 3. Neutralization

[0053] After the acid-washed filtrate, take 5 portions of 100 ml of water-washed filtrate, adjust the pH to 7-8, 8-9, 9-10, 10-11, and 12 with 3 mol / L sodium hydroxide, and set control groups 26, 27, 28, 29, and 30. After the neutralization reaction, take the filter residue, wash it with deionized water with a solid-liquid ratio of 1:3, and then dry it. Determine the content of strontium hydroxide in the filter residue

[0054] Table 8 Effect of neutralization pH on the content of strontium hydroxide produced

[0055]

[0056] As the pH increases, the precipitate mass gradually increases, but the strontium hydroxide content suddenly decreases within the pH 10-11 reaction period. This is because the barium hydroxide precipitate is produced, and the barium hydroxide precipitate mixes with the strontium hydroxide precipitate, resulting in a rapid decrease in the strontium hydroxide content of the precipitate. Therefore, pH 9-10 is the best precipitation condition for strontium hydroxide.

[0057] 4. Double decomposition reaction

[0058] Take the neutralized filtrate and adjust the pH to 7-8. Take three portions, numbered 31, 32, and 33, and add ammonium fluoride solution to the solution to generate a white precipitate. Gradually add ammonium fluoride solution until no white precipitate is generated in the supernatant. Take the filter residue and wash it with deionized water with a solid-liquid ratio of 1:3, then dry it and determine the barium fluoride content.

[0059] Table 9 Metathesis reaction experimental results

[0060]

[0061] After testing, the average barium fluoride content was 98.5%.

[0062] Through the above experiments, it can be known that more than 95% calcium fluoride, 98% strontium hydroxide, and 98.5% barium fluoride can be prepared by water washing, acid washing, neutralization and double decomposition reaction. The best conditions for water washing are solid-liquid ratio of 1:3, reaction time of 60 minutes, and reaction temperature of 60°C. The best conditions for acid washing are pH 2-3 and reaction time of 60 minutes. The best conditions for neutralization are pH 9-10, so as to achieve the purpose of recovering valuable elements in the etching waste liquid sediment.

[0063] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for recycling acidic etching waste, characterized in that: The etching waste is a mixture of calcium fluoride, barium fluoride, strontium fluoride and hydrofluoric acid, and the method comprises the following steps: S100 water washing: add deionized water to the sediment in proportion, and fully dissolve the soluble substances in the sediment at a temperature of 55-75°C; S200 acid washing: remove the filter residue after washing with water, add hydrochloric acid, adjust the pH to 1.8-3.5, and wash and dry the remaining precipitate after the reaction to obtain calcium fluoride; S300 neutralization: add sodium hydroxide to the acid-washed filtrate to adjust the pH to 9-10, react to generate strontium hydroxide precipitate, and then wash and dry to obtain strontium hydroxide; S400 double decomposition reaction: Use hydrochloric acid to adjust the pH to 7-8, add ammonium fluoride to the solution, react to generate barium fluoride precipitate, and then wash and dry to obtain barium fluoride.

2. The method for recycling acidic etching waste according to claim 1, characterized in that: In the step S100, deionized water is added according to a solid-to-liquid ratio of 1:2.5-1:3.

5.

3. The method for recycling acidic etching waste according to claim 1, characterized in that: The reaction time of step S100 or step S200 is 55-65 minutes.

4. The method for recycling acidic etching waste according to claim 1, characterized in that: The washing in step S200 or step S300 or step S400 is performed with deionized water, and the solid-liquid ratio of deionized water to precipitate is 1:2.5-1:3.

5.

5. The method for recycling acidic etching waste according to claim 1, characterized in that: The temperature in step S100 is 60°C.

6. The method for recycling acidic etching waste according to claim 1, characterized in that: The concentrations of the hydrochloric acid and sodium hydroxide solutions are both 3 mol / L.

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