Comprehensive recovery method of acid waste liquid in process of producing graphene oxide by chemical method

Abstract

The invention relates to a comprehensive recovery method of acid waste liquid in a process of producing graphene oxide by a chemical method. The method comprises the following steps: filtering the acid waste liquid to remove impurities; the method comprises the following steps: introducing ammonia gas into the acidic waste liquid, controlling the adding amount of the ammonia gas, enabling the reaction temperature to be within a proper range by virtue of reaction heat generated in a reaction process, and enabling a reaction system to be still acidic, so that part of SO4 < 2-> ions in the acidic waste liquid react with NH3 to generate (NH4) 2SO4, and the residual SO4 < 2-> is combined with Mn < 2 + > ions to form a MnSO4 supersaturated solution which is completely separated out in a salt form; filtering while the solution is hot to obtain a MnSO4 crystal substance and a potassium ammonium sulfate solution; introducing ammonia gas into the ammonium potassium sulfate solution to obtain a mixed solution; and carrying out reduced pressure distillation on the mixed solution to obtain a solid which is the ammonium potassium sulfate compound. The method has the beneficial effects that the resource utilization benefit of each element in the acid waste liquid is maximized, and the production cost of ammonium sulfate potassium compound fertilizer and graphene oxide is reduced.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a comprehensive method for recovering acidic wastewater during the chemical production of graphene oxide. Background Technology

[0002] Graphene and its derivatives have attracted widespread attention in fields such as energy storage, heat dissipation, catalysis, biomedicine, and multifunctional composite materials due to their unique two-dimensional structure and numerous excellent properties. Low-cost preparation of graphene materials is essential for large-scale applications. Large-scale preparation of graphene oxide via wet chemical methods is an important industrial route for obtaining graphene materials. In the improved Hummers' method, large amounts of concentrated sulfuric acid (H2SO4) and water are typically used to ensure sufficient oxidation and necessary purification, thus raising concerns about the treatment of acidic wastewater during large-scale graphene oxide production.

[0003] In the process of preparing graphene oxide using the improved Hummers' method, the acidic wastewater generated typically contains a large amount of waste sulfuric acid, small amounts of manganese and potassium ions, as well as trace amounts of heavy metals introduced from the raw materials. To address the environmental problems caused by the discharge of such wastewater, many domestic enterprises have conducted extensive research and proposed the following solutions: Patent application number 2017111267081 discloses a method for treating acidic waste liquid during graphene production, namely, reacting ammonia water with the waste sulfuric acid; and blowing compressed air or oxygen into the reaction system to dissolve the Mn in the waste sulfuric acid. 2+ Precipitation and solid-liquid separation; However, this process still has some significant problems: 1) The process consumes a large amount of ammonia water, resulting in high raw material costs. Furthermore, after the reaction, the generated potassium ammonium sulfate solution needs to be distilled under reduced pressure to obtain solid potassium ammonium sulfate that can be used as fertilizer. In this process, the introduction of water from the ammonia water undoubtedly increases the energy consumption of the reduced pressure distillation, thereby increasing the cost of wastewater treatment and indirectly increasing the industrial production cost of graphene oxide; 2) The process requires the introduction of additional oxygen, necessitating the addition of oxygen storage tanks and corresponding supporting facilities within the plant area, further increasing the industrial production cost of graphene oxide.

[0004] Patent application number 2021102627489 discloses a method for treating graphene production wastewater and its application. This method employs a two-stage treatment process: first, neutralization is performed using magnesium oxide or magnesium hydroxide, and then OH groups are formed by the dispersion of magnesium oxide or magnesium hydroxide in the water. - Neutralize most of the H in the waste liquid from graphene production + The second stage uses potassium hydroxide as a neutralizer; the first stage has already been neutralized with magnesium oxide or magnesium hydroxide, and only a very small amount of potassium hydroxide is added in the second stage.2+ With excess OH - The reaction forms manganese hydroxide, which has low solubility in water and easily precipitates. During precipitation, it readily flocculates with suspended graphene oxide, and filtration can remove Mn from the graphene production wastewater. 2+ Magnesium sulfate for fertilizer can be obtained by recovering the filtrate from graphene oxide suspension and distilling it under reduced pressure. However, the magnesium hydroxide and potassium hydroxide added during the reaction result in the presence of potassium sulfate in the prepared MgSO4·7H2O, which has low purity. Moreover, magnesium sulfate has low economic value and its use in the fertilizer industry is limited, making it unsuitable for large-scale industrial production. It is evident that this process does not maximize the utilization efficiency of the various elements in the waste acid.

[0005] Patent application number 202210051324.2 discloses a graded treatment method for manganese-containing waste acid. The method involves adding alkaline oxides or hydroxides such as magnesium hydroxide, polyhydrated magnesium oxide, or magnesium oxide to the manganese-containing waste acid until the solution pH value is >7, then heating, filtering to obtain filtrate and manganese-rich filter residue while ensuring that no crystals precipitate in the solution, and then cooling the filtrate to crystallize it. However, this process has some problems: 1) Although the process can recover magnesium sulfate for fertilizer production by obtaining MgSO4·7H2O through thermal concentration, it requires the addition of potassium permanganate as a strong oxidant when treating heavy metal manganese ions in wastewater, resulting in significant differences in treatment efficiency, poor process stability, and difficulty in cost control; 2) In addition to sulfuric acid, the waste acid also contains a certain amount of potassium sulfate, and the thermal concentration and recrystallization methods cannot separate potassium sulfate and magnesium sulfate, thus resulting in the presence of potassium sulfate in the prepared MgSO4·7H2O, leading to low purity. Similar to the problems of the previous patent, this process also fails to fully utilize the various elements in the waste acid. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a comprehensive recovery method for acidic waste liquid in the chemical production of graphene oxide, so as to overcome the shortcomings of the prior art.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A comprehensive method for recovering acidic waste liquid during the chemical production of graphene oxide includes the following steps: S100. The acidic waste liquid generated during the chemical production of graphene oxide is filtered to remove impurities. The acidic waste liquid contains sulfuric acid, manganese sulfate, potassium sulfate and a small amount of graphene oxide. S200. Ammonia gas is introduced into the acidic waste liquid. By controlling the amount of ammonia added, the reaction temperature is kept within a suitable range by utilizing the heat generated during the reaction, and the reaction system remains acidic, thus reducing the SO4 content in the acidic waste liquid. 2-The ions react with NH3 to produce (NH4)2SO4, leaving SO42-. 2- With Mn 2+ Ions combine to form a supersaturated MnSO4 solution and precipitate out completely in the form of salt. The solution is filtered while hot to obtain MnSO4 crystals and potassium ammonium sulfate solution. S300. Ammonia gas is then introduced into the potassium ammonium sulfate solution. When the pH of the system is 7-9, the introduction of ammonia gas is stopped to obtain a mixed solution. S400. The mixed solution is subjected to vacuum distillation, and the solid obtained by distillation is the potassium ammonium sulfate complex.

[0008] Based on the above technical solution, the present invention can be further improved as follows.

[0009] Furthermore, the acidic waste liquid contains sulfuric acid with a mass fraction of 30%–50%, manganese sulfate with a mass fraction of 0.5%–2.0%, and potassium sulfate with a mass fraction of 1.0%–3%.

[0010] Furthermore, the filtration and impurity removal methods include one or a combination of vacuum filtration, sand filtration, ultrafiltration, membrane filtration, and sedimentation.

[0011] Furthermore, the residue obtained from filtration and impurity removal is sent to the graphene oxide production system.

[0012] Furthermore, the reaction temperature in S200 is maintained at 50℃~90℃ by utilizing the heat generated during the reaction process.

[0013] Furthermore, the amount of ammonia added to the S200 is controlled to keep the pH of the reaction system at 5-7 and the reaction time at least 30 minutes.

[0014] Furthermore, the reaction time is 30 to 60 minutes.

[0015] Furthermore, the S200 internal hot filtration is one or a combination of vacuum filtration and membrane filtration.

[0016] Furthermore, ammonia gas is stopped being introduced into the S300 system when the system pH value is 7.

[0017] Furthermore, the temperature for vacuum distillation within the S400 is 20℃~30℃, and the pressure is -0.05MPa~-0.3MPa.

[0018] Furthermore, the vacuum distillation temperature was 25℃ and the pressure was -0.1MPa.

[0019] Furthermore, the water vapor obtained from internal distillation in the S400 is condensed and used for tail gas absorption and recycling.

[0020] Furthermore, if excessive ammonia gas is introduced during the process, resulting in ammonia leakage, it can be absorbed by a two-stage absorption device and then recycled.

[0021] Furthermore, the recycling method is one of the following: gas circulation pump reuse or circulating distilled water absorbing the tail gas and then reheating.

[0022] The beneficial effects of this invention are as follows: This process does not require the addition of oxidants such as O2 or KMnO4. Instead, it uses a staged direct introduction of NH3. In the first stage, the heat generated by the reaction of NH3 with the acidic waste liquid maintains the system at a suitable temperature. Simultaneously, the pH value of the system is controlled. Within this pH and temperature range, the solution remains acidic, and at this point, some SO42- in the acidic waste liquid is neutralized. 2- The ions react with NH3 to produce (NH4)2SO4, leaving SO42-. 2- With Mn 2+ The first stage involves ion bonding to form a supersaturated MnSO4 solution, which is then completely precipitated as salt. In the second stage, NH3 is introduced to fully react the sulfuric acid in the potassium ammonium sulfate solution until the pH reaches 7-9. The mixed solution is then subjected to vacuum distillation. The resulting water vapor is condensed and recycled for tail gas absorption. The solid obtained from distillation is potassium ammonium sulfate, which can be directly sold as compound fertilizer. This process ensures the purity of the obtained potassium ammonium sulfate compound fertilizer, reaching over 99%. As a compound fertilizer, its price can reach over a thousand yuan. This process maximizes the utilization of various elements in the acidic wastewater generated during the chemical production of graphene oxide, significantly reduces the production cost of potassium ammonium sulfate compound fertilizer, and indirectly reduces the production cost of graphene oxide. It has advantages such as low energy consumption and full utilization of wastewater resources, solving the problem of high production costs and low added value of traditional acidic wastewater treatment processes, which indirectly leads to high production costs of graphene oxide. Attached Figure Description

[0023] Figure 1 This is a flowchart of a comprehensive recovery method for acidic waste liquid during the chemical production of graphene oxide. Detailed Implementation

[0024] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0025] Example 1 like Figure 1 As shown, a comprehensive method for recovering acidic wastewater during the chemical production of graphene oxide includes the following steps: S100. Take 1000 kg of acidic waste liquid generated during the chemical production of graphene oxide. The mass fractions of sulfuric acid, manganese ions and potassium ions in the acidic waste liquid are 50%, 0.7% and 0.5% respectively. The waste liquid is filtered and impurities are removed by vacuum filtration. S200. Ammonia gas is introduced into the filtered acidic waste liquid to react with the acid. Since the reaction between ammonia and acidic waste liquid (sulfuric acid) is exothermic, the amount of ammonia added is controlled to maintain the reaction temperature at 50°C using the heat generated during the reaction, and the pH of the reaction system is maintained at 5. The reaction time is 40 minutes. At this pH value, the solution is still acidic, and some SO42- in the acidic waste liquid is released. 2- The ions react with NH3 to produce (NH4)2SO4, leaving SO42-. 2- With Mn 2+ Ions combine to form a supersaturated MnSO4 solution and precipitate out completely in the form of salt. The solution is filtered while hot to obtain MnSO4 crystals and potassium ammonium sulfate solution. S300. Add ammonia gas to the hot potassium ammonium sulfate solution obtained above for the second time to allow the sulfuric acid in the solution to react fully. After reacting fully for 30 minutes, stop the ammonia gas supply when the pH of the system is 7. All the acid in the solution will be neutralized to obtain a mixed solution. S400. The above mixed solution is subjected to vacuum distillation at a temperature of 25℃ and a pressure of -0.1MPa. The water vapor obtained from distillation is condensed and used for tail gas absorption and recycling. The solid obtained from distillation is potassium ammonium sulfate compound, which can be sold directly as compound fertilizer.

[0026] Example 2 like Figure 1 As shown, a comprehensive method for recovering acidic wastewater during the chemical production of graphene oxide includes the following steps: S100. Take 1000 kg of acidic waste liquid generated during the chemical production of graphene oxide. The mass fractions of sulfuric acid, manganese ions and potassium ions in the acidic waste liquid are 50%, 0.7% and 0.5% respectively. The waste liquid is filtered and impurities are removed by vacuum filtration. S200. Ammonia gas is introduced into the filtered acidic waste liquid to react with the acid. Since the reaction between ammonia and acidic waste liquid (sulfuric acid) is exothermic, the amount of ammonia added is controlled to maintain the reaction temperature at 60°C using the heat generated during the reaction, and the pH of the reaction system is maintained at 5.5. The reaction time is 60 minutes. At this pH value, the solution is still acidic, and some SO42- in the acidic waste liquid is released. 2- The ions react with NH3 to produce (NH4)2SO4, leaving SO42-. 2- With Mn 2+ Ions combine to form a supersaturated MnSO4 solution and precipitate out completely in the form of salt. Then, the solution is filtered while hot to obtain MnSO4 crystals and potassium ammonium sulfate solution. S300. Add ammonia gas to the hot potassium ammonium sulfate solution obtained above for the second time to allow the sulfuric acid in the solution to react fully. After reacting fully for 60 minutes, stop the ammonia gas supply when the pH of the system is 7. All the acid in the solution will be neutralized to obtain a mixed solution. S400. The above mixed solution is subjected to vacuum distillation at a temperature of 25℃ and a pressure of -0.1MPa. The water vapor obtained from distillation is condensed and used for tail gas absorption and recycling. The solid obtained from distillation is potassium ammonium sulfate compound, which can be sold directly as compound fertilizer.

[0027] Example 3 like Figure 1 As shown, a comprehensive method for recovering acidic wastewater during the chemical production of graphene oxide includes the following steps: S100. Take 1000 kg of acidic waste liquid generated during the chemical production of graphene oxide. The mass fractions of sulfuric acid, manganese ions and potassium ions in the acidic waste liquid are 50%, 0.7% and 0.5% respectively. The waste liquid is filtered and impurities are removed by vacuum filtration. S200. Ammonia gas is introduced into the filtered acidic waste liquid to react with the acid. Since the reaction between ammonia and acidic waste liquid (sulfuric acid) is exothermic, the amount of ammonia added is controlled to maintain the reaction temperature at 80°C using the heat generated during the reaction, and the pH of the reaction system is maintained at 6. The reaction time is 60 minutes. At this pH value, the solution is still acidic, and some SO42- in the acidic waste liquid is released. 2- The ions react with NH3 to produce (NH4)2SO4, leaving SO42-. 2- With Mn 2+ Ions combine to form a supersaturated MnSO4 solution and precipitate out completely in the form of salt. Then, the solution is filtered while hot to obtain MnSO4 crystals and potassium ammonium sulfate solution. S300. Add ammonia gas to the hot potassium ammonium sulfate solution obtained above for the second time to allow the sulfuric acid in the solution to react fully. After reacting for 100 minutes, stop the ammonia gas supply when the pH of the system is 7. The acid in the solution will be completely neutralized to obtain a mixed solution. S400. The above mixed solution is subjected to vacuum distillation at a temperature of 25℃ and a pressure of -0.1MPa. The water vapor obtained from distillation is condensed and used for tail gas absorption and recycling. The solid obtained from distillation is potassium ammonium sulfate compound, which can be sold directly as compound fertilizer.

[0028] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A comprehensive method for recovering acidic waste liquid during the chemical production of graphene oxide, characterized in that, Includes the following steps: S100. The acidic waste liquid generated during the chemical production of graphene oxide is filtered to remove impurities. The acidic waste liquid contains sulfuric acid, manganese sulfate, potassium sulfate and a small amount of graphene oxide. S200. Ammonia gas is introduced into the acidic waste liquid. By controlling the amount of ammonia added, the reaction temperature is kept within a suitable range by utilizing the heat generated during the reaction, and the reaction system remains acidic, thus reducing the SO4 content in the acidic waste liquid. 2- The ions react with NH3 to produce (NH4)2SO4, leaving SO42-. 2- With Mn 2+ Ions combine to form a supersaturated MnSO4 solution and precipitate out completely in the form of salt. The solution is filtered while hot to obtain MnSO4 crystals and potassium ammonium sulfate solution. S300. Ammonia gas is then introduced into the potassium ammonium sulfate solution. When the pH of the system is 7-9, the introduction of ammonia gas is stopped to obtain a mixed solution. S400. The mixed solution is subjected to vacuum distillation, and the solid obtained by distillation is the potassium ammonium sulfate complex.

2. The comprehensive recovery method for acidic waste liquid in the chemical production of graphene oxide according to claim 1, characterized in that, The acidic waste liquid contains sulfuric acid with a mass fraction of 30%–50%, manganese sulfate with a mass fraction of 0.5%–2.0%, and potassium sulfate with a mass fraction of 1.0%–3%.

3. A comprehensive recovery method for acidic waste liquid during the chemical production of graphene oxide according to claim 1 or 2, characterized in that, The filtration and impurity removal methods include one or a combination of vacuum filtration, sand filtration, ultrafiltration, membrane filtration, and sedimentation.

4. The comprehensive recovery method for acidic waste liquid in the chemical production of graphene oxide according to claim 3, characterized in that, The S200 utilizes the heat generated during the reaction process to maintain the reaction temperature between 50°C and 90°C.

5. The comprehensive recovery method for acidic waste liquid in the chemical production of graphene oxide according to claim 4, characterized in that, The amount of ammonia added in the S200 is controlled to keep the pH of the reaction system at 5-7 and the reaction time at least 30 minutes.

6. The comprehensive recovery method for acidic waste liquid in the chemical production of graphene oxide according to claim 5, characterized in that, The reaction time is 30 min to 60 min.

7. The comprehensive recovery method for acidic waste liquid in the chemical production of graphene oxide according to claim 1, characterized in that, The S200 internal hot filtration system employs one or a combination of vacuum filtration and membrane filtration.

8. The comprehensive recovery method for acidic waste liquid in the chemical production of graphene oxide according to claim 1, characterized in that, The S400 internal vacuum distillation temperature is 20℃~30℃ and the pressure is -0.05MPa~-0.3MPa.

9. The comprehensive recovery method for acidic waste liquid in the chemical production of graphene oxide according to claim 8, characterized in that, The temperature for vacuum distillation is 25℃ and the pressure is -0.1MPa.

10. The comprehensive recovery method for acidic waste liquid in the chemical production of graphene oxide according to claim 1, characterized in that, The water vapor obtained from internal distillation in the S400 is condensed and then used for tail gas absorption and recycling.

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