Resource recycling method of tetramethylammonium hydroxide wastewater

Abstract

The invention provides a resource recycling method of tetramethylammonium hydroxide wastewater, which comprises the following steps: (1) introducing carbon dioxide into the tetramethylammonium hydroxide wastewater to carry out degumming reaction, and carrying out first solid-liquid separation treatment to obtain a tetramethylammonium carbonate solution and glue waste; (2) carrying out low-temperature evaporation and recrystallization treatment on the tetramethyl ammonium carbonate solution, and carrying out second solid-liquid separation treatment to obtain tetramethyl ammonium carbonate crystals; (3) mixing the tetramethyl ammonium carbonate crystals, a transforming agent and a solvent for a transformation reaction, and carrying out third solid-liquid separation treatment to obtain a crude tetramethyl ammonium hydroxide solution and calcium carbonate; and (4) carrying out nanofiltration treatment on the crude tetramethylammonium hydroxide solution to obtain tetramethylammonium hydroxide. According to the method disclosed by the invention, tetramethylammonium hydroxide can be recycled at a high recovery rate under the condition of degumming, and tetramethylammonium hydroxide with electronic-grade purity is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of resource recovery and relates to a resource recovery method for tetramethylammonium hydroxide wastewater. Background Art

[0002] Tetramethylammonium hydroxide (TMAH), a strongly alkaline organic compound, is widely used in semiconductors, liquid crystal displays, organic synthesis, and other fields. In semiconductor photolithography, TMAH is used as a developer to remove unexposed portions of photoresist. In liquid crystal display manufacturing, it serves as an etchant and cleaning agent, enabling precise surface treatment of LCD panels. However, with the increasing use of TMAH, the resulting large amounts of wastewater containing TMAH have become an urgent environmental concern.

[0003] Tetramethylammonium hydroxide wastewater is highly alkaline. Direct discharge not only severely damages the soil, water, and other ecological environments, corroding drainage pipes, but also affects the survival of aquatic organisms, leading to imbalances in aquatic ecosystems. Furthermore, the tetramethylammonium hydroxide contained in it is a high-value chemical, and direct discharge results in a significant waste of resources. Therefore, effective treatment and resource recovery of tetramethylammonium hydroxide wastewater has significant environmental and economic benefits.

[0004] CN116119853A discloses a method for recovering tetramethylammonium hydroxide developer waste liquid, which comprises the following steps: first allowing the tetramethylammonium hydroxide developer waste liquid to stand and filter, then adding an acidic reagent for treatment, then adding sulfuric acid for further treatment, and then adding barium chloride to form barium sulfate precipitate and tetramethylammonium hydroxide solution, and then adjusting the pH value to alkaline, and then passing through an ion exchange resin to obtain a tetramethylammonium hydroxide aqueous solution.

[0005] CN108623052A discloses a method for recovering tetramethylammonium hydroxide from secondary wastewater of developer waste, comprising a collection step, a first adjustment step, a filtration step, a purification step, and an electrolytic dialysis step. First, the secondary wastewater generated after the developer wastewater is collected and tetramethylammonium hydroxide is recovered is then adjusted with an acid solution to form a tetramethylammonium salt aqueous solution with the tetramethylammonium hydroxide ions and the acid solution, rendering the waste photoresist insoluble in the secondary wastewater. Next, a filtration step is performed to remove the waste photoresist to obtain a tetramethylammonium salt aqueous solution. The metal ions contained in the tetramethylammonium salt aqueous solution are then purified using a resin tower to obtain a tetramethylammonium salt aqueous solution.

[0006] The above-mentioned solution adds an acidic substance to neutralize the alkaline substances in the wastewater. Although it can reduce the pH value of the wastewater, it produces a large amount of saline wastewater and cannot achieve resource recovery and utilization of tetramethylammonium hydroxide. While the use of resin can separate and recover tetramethylammonium hydroxide to a certain extent, it has disadvantages such as easy saturation of the resin, difficulty in regeneration, and low treatment efficiency. It is difficult to meet the comprehensive requirements of wastewater treatment efficiency, resource recovery rate, and economic benefits in actual production. Therefore, it is urgent to develop a method for recovering tetramethylammonium hydroxide wastewater that can efficiently recover tetramethylammonium hydroxide. Summary of the Invention

[0007] The present invention aims to provide a resource recovery method for tetramethylammonium hydroxide wastewater. The method can recover tetramethylammonium hydroxide with a high recovery rate under the condition of removing glue, and obtain tetramethylammonium hydroxide with electronic grade purity.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for recycling tetramethylammonium hydroxide wastewater, which comprises the following steps:

[0010] (1) introducing carbon dioxide into tetramethylammonium hydroxide wastewater to perform a degumming reaction, and obtaining a tetramethylammonium carbonate solution and a glue waste material through a first solid-liquid separation process;

[0011] (2) subjecting the tetramethylammonium carbonate solution to low-temperature evaporation and recrystallization treatment, and subjecting it to a second solid-liquid separation treatment to obtain tetramethylammonium carbonate crystals;

[0012] (3) mixing tetramethylammonium carbonate crystals, a conversion agent, and a solvent to carry out a conversion reaction, and performing a third solid-liquid separation process to obtain a crude tetramethylammonium hydroxide solution and calcium carbonate;

[0013] (4) The crude tetramethylammonium hydroxide solution is subjected to nanofiltration to obtain tetramethylammonium hydroxide.

[0014] The first solid-liquid separation treatment, the second solid-liquid separation treatment and the third solid-liquid separation treatment of the present invention independently include centrifugation and / or filtration treatment.

[0015] The invention first neutralizes and removes glue by introducing carbon dioxide, then uses low-temperature evaporation to avoid decomposition of tetramethylammonium carbonate, and then uses recrystallization to purify to obtain a tetramethylammonium carbonate product. The purified tetramethylammonium carbonate undergoes a conversion reaction with high-purity lime to obtain tetramethylammonium hydroxide again, and then calcium ions are removed through a nanofiltration membrane to obtain electronic-grade tetramethylammonium hydroxide.

[0016] Preferably, the endpoint pH of the degumming reaction in step (1) is 6 to 8, for example, 6, 6.5, 7, 7.5 or 8, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0017] Tetramethylammonium hydroxide (TMAH) is a developer and cleaning agent commonly used in the manufacture of semiconductors and liquid crystal display panels. Its wastewater contains colloidal substances such as photoresist, organic polymers or particulate matter. The present invention introduces carbon dioxide into the tetramethylammonium hydroxide wastewater, controls the pH of the solution to remove the glue, and completely converts the tetramethylammonium hydroxide into tetramethylammonium carbonate. The degumming method is simple and highly efficient.

[0018] Preferably, the temperature of the low-temperature evaporation in step (2) is 45°C to 55°C, for example, 45°C, 48°C, 50°C, 52°C or 55°C, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0019] The present invention adopts a low-temperature evaporation method to avoid the decomposition of tetramethylammonium carbonate, and the low-temperature evaporation is performed using a heat pump evaporation device.

[0020] Preferably, the temperature of the recrystallization treatment in step (2) is 25°C to 40°C, for example, 25°C, 30°C, 32°C, 35°C or 40°C, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0021] The invention utilizes that the impurity concentration in the tetramethylammonium carbonate solution is far lower than that of the tetramethylammonium carbonate solution and will not be saturated and precipitated, and simultaneously the crystallization solid-liquid separation is carried out to completely remove the impurities.

[0022] Preferably, the recrystallization treatment time in step (2) is 1 h to 3 h, for example, 1 h, 1.5 h, 2 h, 2.5 h or 3 h, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0023] Preferably, the conversion agent in step (3) comprises calcium hydroxide and / or barium hydroxide.

[0024] Preferably, the molar ratio of the tetramethylammonium carbonate crystals to the conversion agent in step (3) is 1:(1-1.2), for example: 1:1, 1:1.05, 1:1.1, 1:1.15 or 1:1.2, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0025] Preferably, the solvent in step (3) comprises ultrapure water.

[0026] Preferably, the temperature of the conversion reaction in step (3) is 30°C to 50°C, for example, 30°C, 35°C, 40°C, 45°C or 50°C, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0027] Preferably, the conversion reaction time in step (3) is 2 h to 5 h, for example, 2 h, 2.5 h, 3 h, 3.5 h, 4 h or 5 h, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0028] Preferably, the applicable pH of the nanofiltration membrane in the nanofiltration treatment in step (4) is 8 to 14, for example, 8, 9, 10, 12 or 14, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0029] Preferably, the nanofiltration membrane of the nanofiltration treatment in step (4) comprises a modified polytetrafluoroethylene (PTFE) membrane.

[0030] The modified PTFE membrane of the present invention is obtained by grafting acrylic acid monomers on the surface of PTFE through initiation by ultraviolet light or gamma rays.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The method of the present invention can convert tetramethylammonium hydroxide into tetramethylammonium carbonate with low solubility in water under the condition of removing the glue, and then perform low-temperature evaporation and recrystallization to obtain high-purity tetramethylammonium carbonate crystals. Then, the tetramethylammonium carbonate is subjected to a conversion (double decomposition) reaction with lime to obtain tetramethylammonium hydroxide again. After nanofiltration treatment to remove calcium ions, tetramethylammonium hydroxide with electronic grade purity (6N, ≥99.9999%) can be obtained.

[0033] (2) The method for recycling tetramethylammonium hydroxide wastewater of the present invention can obtain tetramethylammonium hydroxide with a purity of more than 99.91%, and a recovery rate of tetramethylammonium hydroxide of more than 95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a process flow chart of the resource recovery method of tetramethylammonium hydroxide wastewater described in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0036] The examples and comparative examples of the present invention use tetramethylammonium hydroxide wastewater to dissolve photoresist, impurities and tetramethylammonium hydroxide, and the mass concentration of the tetramethylammonium hydroxide is 3%.

[0037] Example 1

[0038] This embodiment provides a method for recycling tetramethylammonium hydroxide wastewater. The process flow diagram of the recycling method is as follows: Figure 1 As shown, the resource recovery method includes the following steps:

[0039] (1) introducing carbon dioxide into tetramethylammonium hydroxide wastewater to perform a degumming reaction until the pH of the solution reaches 7, and filtering the obtained material to obtain a tetramethylammonium carbonate solution and a glue waste material;

[0040] (2) using a heat pump evaporation device to perform low-temperature evaporation treatment on the tetramethylammonium carbonate solution at 50° C., cooling it to 30° C. for recrystallization for 2 h, and centrifuging to obtain tetramethylammonium carbonate crystals;

[0041] (3) dissolving tetramethylammonium carbonate crystals in ultrapure water and adding calcium hydroxide (the molar ratio of tetramethylammonium carbonate to calcium hydroxide is 1:1.1) and performing a conversion reaction at 40° C. for 3 h, and filtering to obtain a crude tetramethylammonium hydroxide solution and calcium carbonate;

[0042] (4) Using a modified PTFE membrane with an applicable pH range of 8 to 14, the crude tetramethylammonium hydroxide solution is subjected to nanofiltration treatment to obtain tetramethylammonium hydroxide.

[0043] Example 2

[0044] This embodiment provides a method for recycling tetramethylammonium hydroxide wastewater. The process flow diagram of the recycling method is as follows: Figure 1 As shown, the resource recovery method includes the following steps:

[0045] (1) introducing carbon dioxide into tetramethylammonium hydroxide wastewater to perform a degumming reaction until the pH of the solution reaches 6, and filtering the obtained material to obtain a tetramethylammonium carbonate solution and a glue waste material;

[0046] (2) using a heat pump evaporation device to perform low-temperature evaporation treatment on the tetramethylammonium carbonate solution at 55° C., cooling it to 40° C. for recrystallization for 3 hours, and centrifuging to obtain tetramethylammonium carbonate crystals;

[0047] (3) dissolving tetramethylammonium carbonate crystals in ultrapure water and adding calcium hydroxide (the molar ratio of tetramethylammonium carbonate to calcium hydroxide is 1:1.2) and performing a conversion reaction at 30°C for 5 hours, and filtering to obtain a crude tetramethylammonium hydroxide solution and calcium carbonate;

[0048] (4) Using a modified PTFE membrane with an applicable pH range of 8 to 14, the crude tetramethylammonium hydroxide solution is subjected to nanofiltration treatment to obtain tetramethylammonium hydroxide.

[0049] Example 3

[0050] This embodiment provides a method for recycling tetramethylammonium hydroxide wastewater. The process flow diagram of the recycling method is as follows: Figure 1 As shown, the resource recovery method includes the following steps:

[0051] (1) introducing carbon dioxide into tetramethylammonium hydroxide wastewater to perform a degumming reaction until the pH of the solution reaches 8, and filtering the obtained material to obtain a tetramethylammonium carbonate solution and a glue waste material;

[0052] (2) using a heat pump evaporation device to perform low-temperature evaporation treatment on the tetramethylammonium carbonate solution at 45° C., then cooling to 25° C. for recrystallization for 1 hour, and centrifuging to obtain tetramethylammonium carbonate crystals;

[0053] (3) dissolving tetramethylammonium carbonate crystals in ultrapure water and then adding and mixing with barium hydroxide (the molar ratio of tetramethylammonium carbonate to barium hydroxide is 1:1) at 50° C. for conversion reaction for 3 h, and filtering to obtain crude tetramethylammonium hydroxide solution and calcium carbonate;

[0054] (4) Using a modified PTFE membrane with an applicable pH range of 8 to 14, the crude tetramethylammonium hydroxide solution is subjected to nanofiltration treatment to obtain tetramethylammonium hydroxide.

[0055] Example 4

[0056] The only difference between this embodiment and embodiment 1 is that the pH in step (1) is 9, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0057] Example 5

[0058] The only difference between this embodiment and embodiment 1 is that the temperature of the low-temperature evaporation treatment in step (2) is 60° C., and the other conditions and parameters are exactly the same as those in embodiment 1.

[0059] Example 6

[0060] The only difference between this embodiment and embodiment 1 is that the temperature of the recrystallization treatment in step (2) is 45° C., and the other conditions and parameters are exactly the same as those in embodiment 1.

[0061] Example 7

[0062] The only difference between this embodiment and embodiment 1 is that the temperature of the recrystallization treatment in step (2) is 20° C., and the other conditions and parameters are exactly the same as those in embodiment 1.

[0063] Example 8

[0064] The only difference between this embodiment and embodiment 1 is that the temperature of the conversion reaction in step (3) is 20° C., and the other conditions and parameters are exactly the same as those in embodiment 1.

[0065] Example 9

[0066] The only difference between this embodiment and embodiment 1 is that the temperature of the conversion reaction in step (3) is 60° C., and the other conditions and parameters are exactly the same as those in embodiment 1.

[0067] Comparative Example 1

[0068] The only difference between this comparative example and Example 1 is that step (3) directly heats and decomposes the tetramethylammonium carbonate crystals without step (4). Other conditions and parameters are exactly the same as those in Example 1.

[0069] Performance testing:

[0070] The purity and recovery of the tetramethylammonium hydroxide obtained in the examples and comparative examples were tested. The test results are shown in Table 1:

[0071] Table 1

[0072] purity(%) Recovery rate (%) Example 1 99.99 99 Example 2 99.98 98 Example 3 99.99 99 Example 4 99.93 97 Example 5 99.92 96 Example 6 99.91 95 Example 7 99.92 97 Example 8 99.93 96 Example 9 99.92 95 Comparative Example 1 90 89

[0073] As can be seen from Table 1, from Examples 1-9, the purity of tetramethylammonium hydroxide obtained by the resource recovery method of tetramethylammonium hydroxide wastewater of the present invention can reach more than 99.91%, and the recovery rate of tetramethylammonium hydroxide can reach more than 95%.

[0074] By comparing Example 1 and Example 4, it can be seen that in the resource recovery method of tetramethylammonium hydroxide wastewater according to the present invention, the endpoint pH of the degumming in step (1) affects the recovery rate of tetramethylammonium hydroxide. When the endpoint pH of the degumming is controlled at 6 to 8, the degumming effect is good and the tetramethylammonium hydroxide can be completely converted into tetramethylammonium carbonate. If the endpoint pH of the degumming is too low, the conversion effect will not be improved. If the endpoint pH of the degumming is too high, the amount of carbon dioxide introduced is insufficient, and the tetramethylammonium hydroxide cannot be completely converted into tetramethylammonium carbonate, resulting in a reduced recovery rate of tetramethylammonium hydroxide.

[0075] By comparing Example 1 and Example 5, it can be seen that in the resource recovery method of tetramethylammonium hydroxide wastewater according to the present invention, the temperature of the low-temperature evaporation treatment in step (2) affects the recovery rate of tetramethylammonium hydroxide. The temperature of the low-temperature evaporation treatment is controlled at 45° C. to 55° C., and water is removed while avoiding the decomposition of tetramethylammonium carbonate, thereby improving the subsequent recovery rate of tetramethylammonium hydroxide. If the temperature of the low-temperature evaporation treatment is too high, tetramethylammonium carbonate decomposes, resulting in a decrease in the recovery rate of tetramethylammonium hydroxide.

[0076] By comparing Example 1 with Examples 6-7, it can be seen that in the resource recovery method of tetramethylammonium hydroxide wastewater of the present invention, the temperature of the recrystallization treatment in step (2) affects the recovery rate of tetramethylammonium hydroxide. By controlling the temperature of the recrystallization treatment at 25° C. to 40° C., tetramethylammonium carbonate can be recrystallized to a large extent. If the temperature of the recrystallization treatment is too low, impurities in the solution will also be recrystallized, resulting in a decrease in the purity of the recovered tetramethylammonium hydroxide. If the temperature of the recrystallization treatment is too high, the tetramethylammonium carbonate cannot be completely recrystallized, resulting in a decrease in the recovery rate of tetramethylammonium hydroxide.

[0077] By comparing Example 1 with Examples 8-9, it can be seen that in the resource recovery method of tetramethylammonium hydroxide wastewater according to the present invention, the temperature of the conversion reaction in step (3) affects the recovery rate of tetramethylammonium hydroxide. By controlling the temperature of the conversion reaction at 30°C to 50°C, tetramethylammonium carbonate can be converted into tetramethylammonium hydroxide to a large extent. If the temperature of the conversion reaction is too low, the conversion rate of tetramethylammonium carbonate decreases, resulting in a decrease in the recovery rate of tetramethylammonium hydroxide. If the temperature of the conversion reaction is too high, tetramethylammonium carbonate decomposes during the conversion process, resulting in a decrease in the recovery rate of tetramethylammonium hydroxide.

[0078] By comparing Example 1 with Comparative Example 1, it can be seen that, compared with directly heating and decomposing tetramethylammonium carbonate crystals, the method of the present invention can greatly improve the purity of the obtained tetramethylammonium hydroxide, and the recovery rate is also significantly improved.

[0079] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for recycling tetramethylammonium hydroxide wastewater, characterized in that: The resource recovery method comprises the following steps: (1) introducing carbon dioxide into tetramethylammonium hydroxide wastewater to perform a degumming reaction, and obtaining a tetramethylammonium carbonate solution and a glue waste material through a first solid-liquid separation process; (2) subjecting the tetramethylammonium carbonate solution to low-temperature evaporation and recrystallization treatment, and subjecting it to a second solid-liquid separation treatment to obtain tetramethylammonium carbonate crystals; (3) mixing tetramethylammonium carbonate crystals, a conversion agent, and a solvent to carry out a conversion reaction, and performing a third solid-liquid separation process to obtain a crude tetramethylammonium hydroxide solution and calcium carbonate; (4) The crude tetramethylammonium hydroxide solution is subjected to nanofiltration to obtain tetramethylammonium hydroxide.

2. The resource recovery method according to claim 1, wherein: The endpoint pH of the degumming reaction in step (1) is 6-8.

3. The resource recovery method according to claim 1 or 2, characterized in that: The temperature of the low-temperature evaporation in step (2) is 45°C to 55°C.

4. The resource recovery method according to any one of claims 1 to 3, characterized in that: The temperature of the recrystallization treatment in step (2) is 25°C to 40°C.

5. The resource recovery method according to any one of claims 1 to 4, characterized in that: The recrystallization treatment time in step (2) is 1 h to 3 h.

6. The resource recovery method according to any one of claims 1 to 5, characterized in that: The conversion agent in step (3) comprises calcium hydroxide and / or barium hydroxide; Preferably, the molar ratio of the tetramethylammonium carbonate crystals to the conversion agent in step (3) is 1:(1-1.2); Preferably, the solvent in step (3) comprises ultrapure water.

7. The resource recovery method according to any one of claims 1 to 6, characterized in that: The temperature of the conversion reaction in step (3) is 30°C to 50°C.

8. The resource recovery method according to any one of claims 1 to 7, characterized in that: The conversion reaction time in step (3) is 2h to 5h.

9. The resource recovery method according to any one of claims 1 to 8, characterized in that: The applicable pH of the nanofiltration membrane in the nanofiltration treatment in step (4) is 8 to 14.

10. The resource recovery method according to any one of claims 1 to 9, characterized in that: The nanofiltration membrane of the nanofiltration treatment in step (4) includes a modified PTFE membrane.

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