A deep treatment process for acetonitrile wastewater and an integral catalyst

Abstract

This application discloses a process for advanced treatment of acetonitrile wastewater and a monolithic catalyst, belonging to the fields of wastewater treatment technology and environmental functional materials technology. This application utilizes a transition-metal-doped aluminum sol in a one-step process to prepare an alumina monolithic catalyst for high-temperature Fenton oxidation treatment of acetonitrile wastewater. This process combines the high activity of the transition-metal-doped aluminum sol monolithic catalyst with the strong oxidizing power of high-temperature Fenton oxidation, effectively resolving the difficulty in degrading acetonitrile wastewater. After treatment, the acetonitrile wastewater can meet discharge standards, offering advantages such as high treatment efficiency, low energy consumption, and no secondary pollution.

Description

Technical Field

[0001] The present application relates to an acetonitrile wastewater deep treatment process and an integral catalyst, belonging to the technical fields of wastewater treatment technology and environmental functional materials. Background Art

[0002] Acetonitrile (CH3CN), a colorless, transparent liquid, exhibits high transparency, good solubility, and low UV background absorption. Its excellent solvent properties have led to its widespread application in organic synthesis, pharmaceuticals, textiles, and analytical fields. Acetonitrile is often used as a solvent in preparative chromatography for the separation and purification of high-purity pharmaceuticals, but this also generates significant amounts of acetonitrile waste.

[0003] The high-concentration acetonitrile wastewater produced by preparative chromatography contains a high water content and small amounts of impurities such as inorganic salts, organic acids, and proteins, making it difficult to treat and highly environmentally hazardous. For this high-concentration acetonitrile wastewater, companies within the industry typically entrust specialized hazardous waste treatment facilities to dispose of it, which is not only costly but also wasteful. Some companies in the industry use distillation to recover acetonitrile, but the residual liquid still contains high concentrations of acetonitrile and other difficult-to-degrade organic matter, posing a certain threat to the environment.

[0004] Traditional treatment methods such as biological treatment and adsorption methods have problems such as low efficiency, high cost, and easy generation of secondary pollution. Fenton oxidation, as an advanced oxidation technology, can effectively decompose refractory organic matter. However, conventional homogeneous Fenton oxidation has certain limitations. To solve the problems existing in homogeneous Fenton technology, researchers at home and abroad have made continuous efforts to load iron or other active components onto solid phase carriers, or directly use solid metal oxides as catalysts to replace the iron source in traditional Fenton reactions, and develop high-efficiency and high-temperature heterogeneous Fenton oxidation technology. The catalyst in the heterogeneous system is easy to separate from water and recycle, and the system has a wider pH range and higher H2O2 utilization rate. In addition, by controlling the amount of active metal dissolved in the solid catalyst, the generation of large amounts of iron sludge can be avoided. Therefore, heterogeneous Fenton technology has greater advantages than homogeneous methods. However, room-temperature heterogeneous Fenton still has certain limitations in terms of treatment efficiency. The high-temperature heterogeneous Fenton reaction is a reaction that uses cheap and non-toxic H2O2 as an oxidant under moderate temperature and pressure conditions (40~150℃, 0~1.0MPa) in the presence of a high-efficiency catalyst to oxidize organic pollutants in wastewater into small molecular organic matter with low toxicity or easy biodegradation, and ultimately mineralize the organic pollutants into CO2 and H2O.

[0005] By utilizing the residual heat of the distilled water from acetonitrile wastewater to realize the Fenton reaction under high temperature conditions, the treatment efficiency of acetonitrile wastewater can be significantly improved while reducing energy consumption and the risk of secondary pollution.

[0006] Solid catalysts can slag due to friction during loading, so developing monolithic catalysts for high-temperature Fenton oxidation is also of great significance. Patent CN111250087B relates to the preparation of a catalyst for catalytic ozone oxidation, using a two-step process to obtain an aluminum sol followed by impregnation with ceramics to prepare the catalyst. In contrast, the present invention uses a one-step process to combine the active component and support to prepare a monolithic catalyst for high-temperature Fenton oxidation treatment of acetonitrile wastewater. Summary of the Invention

[0007] In response to the above-mentioned technical problems, this application proposes a deep treatment process for acetonitrile wastewater and a monolithic catalyst technical solution. By using transition metal-doped aluminum sol to prepare an alumina monolithic catalyst and combining it with high-temperature Fenton oxidation, the treatment efficiency of acetonitrile wastewater is significantly improved, while reducing energy consumption and secondary pollution.

[0008] This application adopts the following technical solutions:

[0009] According to the first aspect of the present application, a process for deep treatment of acetonitrile wastewater and an integral catalyst are provided.

[0010] The acetonitrile wastewater deep treatment process is a high-temperature Fenton oxidation technology for acetonitrile wastewater, which uses a high-temperature oxidation monolithic catalyst.

[0011] Optionally, the acetonitrile wastewater advanced treatment process comprises the following steps:

[0012] The acetonitrile wastewater is introduced into a high-temperature Fenton oxidation reactor equipped with a monolithic catalyst and reacted in the presence of hydrogen peroxide.

[0013] Optionally, the preparation method of the monolithic catalyst comprises the following steps:

[0014] A mixed solution containing aluminum sol, transition metal salt, pore-forming agent and coagulant is injected into a mold for molding, and then the molded solid product is dried and calcined to obtain the monolithic catalyst.

[0015] Optionally, the preparation method of the monolithic catalyst comprises the following steps:

[0016] S1. Add transition metal salt to aluminum sol and mix well to obtain solution A;

[0017] S2. Adding a pore-forming agent to solution A under stirring to obtain solution B;

[0018] S3. Adding a coagulant to solution B under stirring to obtain solution C, then injecting solution C into a mold for curing, and demolding to obtain a gel product C-3;

[0019] S4, drying the gel product C-3 to obtain a solid product D-3;

[0020] S5. calcining the solid product D-3 to obtain a monolithic catalyst.

[0021] Optionally, in step S1, the aluminum sol is obtained by reacting aluminum foil and hydrochloric acid;

[0022] The molar ratio of aluminum element to hydrochloric acid in the aluminum foil is 1.3-1.8:1;

[0023] The amount of the transition metal salt added to solution A, calculated as the transition metal element, is 0.5-10 wt.% of the weight of the monolithic catalyst.

[0024] Optionally, the solid content of the aluminum sol is 20-30 wt.%, and the density is 1.2-1.4 g / ml.

[0025] Optionally, the transition metal is selected from the nitrate or sulfate of at least one of iron, cobalt, manganese, titanium and copper.

[0026] Optionally, in step S2, the pore-forming agent is selected from at least one of ammonium lauryl sulfate, sodium lauryl sulfate, and glycerol.

[0027] Optionally, the amount of the pore-forming agent is 0.01-0.25 wt.% of the weight of solution A.

[0028] Optionally, in step S3, the coagulant is selected from at least one of ammonium chloride, potassium chloride, potassium hydroxide, and calcium chloride.

[0029] Optionally, the content of the heavy coagulant in the solution C is 0.01-0.10 mmol / g.

[0030] Optionally, the stirring conditions in steps S2 and S3 include: high-speed stirring with a rotation speed of 2000-5000 rpm.

[0031] Optionally, in step S4, the drying conditions include: a temperature of 20-50° C. and a time of 3-8 hours.

[0032] Optionally, in step S5, the calcination conditions include: a calcination temperature of 480-560° C. and a calcination time of 2-5 hours.

[0033] Optionally, in step S5, the calcination temperature is preferably 500-550°C.

[0034] Optionally, the dimensions of the monolithic catalyst are: 2-10 cm in height and 2-10 cm in diameter.

[0035] Optionally, the porosity of the monolithic catalyst is 60-90%.

[0036] Optionally, the loading amount of the transition metal element on the alumina monolithic catalyst is 0.5-10 wt.%; the loading amount of the transition metal element on the catalyst is calculated based on the mass of the transition metal element.

[0037] Optionally, the monolithic catalyst is used as a catalyst in a high-temperature Fenton oxidation technology.

[0038] Optionally, the acetonitrile wastewater is acetonitrile wastewater.

[0039] Optionally, the residual temperature of the acetonitrile wastewater is 40-90° C., the concentration of the acetonitrile wastewater is 0.02-0.06%, and the TOC concentration of the acetonitrile wastewater is 100-300 mg / L.

[0040] Optionally, the reaction conditions include: the initial pH of the acetonitrile wastewater is 2-7, mH2O2:mTOC=1.5-17.5:1, and the volume space velocity of the acetonitrile wastewater is 0.5-6h -1 .

[0041] Optionally, after deep treatment of the acetonitrile wastewater, the acetonitrile concentration is reduced to less than 0.5 mg / L and the TOC is reduced to less than 100 mg / L, meeting the discharge standards.

[0042] The beneficial effects of this application include:

[0043] (1) The acetonitrile wastewater deep treatment process and the integral catalyst provided in this application adopt a one-step method to prepare the catalyst using an active component carrier. The catalyst has a regular shape and the whole catalyst can be directly filled into the reactor, thereby avoiding mutual friction between the catalyst surfaces during transportation and use and protecting the effective catalytic components formed by surface modification. In addition, the catalyst has the characteristics of high strength, friction resistance, and the active components are not easy to lose.

[0044] (2) The acetonitrile wastewater deep treatment process provided in this application utilizes the waste heat from the distillation of acetonitrile waste liquid. The high-temperature Fenton reaction accelerates the generation rate of hydroxyl radicals, shortens the reaction time, improves the utilization rate of hydrogen peroxide, and has high treatment efficiency.

[0045] (3) The acetonitrile wastewater deep treatment process provided in this application has no secondary pollution, and the catalyst can be easily recovered and reused. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a flow chart of the wastewater treatment equipment for this application.

[0047] 1. Water inlet tank; 2. Hydrogen peroxide storage tank; 3. First liquid inlet pump; 4. Second liquid inlet pump; 5. Reactor temperature; 6. Furnace wall heating temperature; 7. Reactor; 8. Heating jacket; 9. Water outlet tank. DETAILED DESCRIPTION

[0048] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0049] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0050] Unless otherwise specified, conventional methods were used for testing, and instrument settings were those recommended by the manufacturer.

[0051] The analysis method in the examples of this application is as follows:

[0052] TOC (total organic carbon) was determined using a TOC-VCPH / CPN analyzer produced by Shimadzu Corporation of Japan; pH was determined using a Leiji PHS-3C precision pH meter; acetonitrile content was detected using a GC-2100 gas chromatograph equipped with an FID detector and an FFAP column (30m×0.32mm×0.25μm), with an inlet temperature of 200℃, a carrier gas flow rate of 2.0mL / min, an injection volume of 1.0μL, a split ratio of 10:1, FID250℃, a column temperature of 60℃ maintained for 1min, a heating rate of 8℃ / min, an air flow rate of 450mL / min, and an air flow rate of 45mL / min.

[0053] The application of the prepared catalyst in high-temperature Fenton reaction was evaluated using a fixed-bed continuous reaction evaluation device with a heating jacket. The reaction temperature was set to 50°C, the catalyst loading volume was 50 mL, the pH was adjusted to the corresponding value with dilute sulfuric acid, and the space velocity was 0.5 h -1 .

[0054] The high-temperature Fenton oxidation reactor and the schematic diagram of the treatment process used in the high-temperature Fenton oxidation treatment in the embodiment of the present application are shown in FIG. Figure 1 As shown:

[0055] The high-temperature Fenton oxidation reactor includes a water inlet at the bottom of the reactor, which is connected to the water tank 1 through the first liquid inlet pump 3, and the water inlet is connected to the hydrogen peroxide storage tank 2 through the second liquid inlet pump 4 (the first liquid inlet pump and the second liquid inlet pump can be plunger pumps). The reactor 7 is filled with an integral catalyst, and a heating jacket 8 is provided outside the reactor 7 for heating the reactor to a corresponding temperature. The temperature in the reactor 7 is detected by the reactor temperature monitor 5, and problems with the heating jacket 8 are detected by the furnace wall heating temperature monitor. A water outlet is provided on the top of the reactor, and the water after the reaction flows out through the water outlet, and the water outlet is connected to the water outlet tank 9.

[0056] Example 1

[0057] 1) Aluminum foil and hydrochloric acid were stirred in a molar ratio of 1.4:1 to obtain an aluminum sol with a solid content of 23 wt.% and a density of 1.3 g / mL. Ferric nitrate nonahydrate was added, calculated as 3% of the mass of the aluminum sol, and uniformly stirred to dissolve it in the aluminum sol, to obtain an iron-aluminum sol mixed solution A-3Fe.

[0058] 2) stirring the aluminum sol A-3Fe at 3000 rpm using a mechanical stirrer, and adding 0.1 wt% sodium dodecyl sulfate to form pores to obtain B-3Fe;

[0059] 3) Add potassium chloride at a concentration of 0.05 mmol / g to B-3Fe, continue stirring at high speed, and inject it into a mold with a diameter of 2 cm and a height of 10 cm to obtain C-3Fe.

[0060] 4) Demolding the C-3Fe and drying it at 20°C for 3 hours to obtain D-3Fe;

[0061] 5) D-3Fe was placed in air atmosphere at 520 o C was calcined for 3 h to obtain the integral catalyst E-3Fe.

[0062] Example 2

[0063] 1) Aluminum foil and hydrochloric acid were stirred in a molar ratio of 1.4:1 to obtain an aluminum sol with a solid content of 23 wt.% and a density of 1.3 g / mL. Copper nitrate trihydrate was added, calculated as 3% of the mass of the aluminum sol, and dissolved in the aluminum sol with uniform stirring to obtain an iron-aluminum sol mixed solution A-3Cu.

[0064] 2) stirring the aluminum sol A-3Cu at 3000 rpm using a mechanical stirrer, and adding 0.15 wt% sodium dodecyl sulfate to form pores to obtain B-3Cu;

[0065] 3) Add potassium chloride at a concentration of 0.1 mmol / g to B-3Fe, continue stirring at high speed, and inject it into a mold with a diameter of 2 cm and a height of 10 cm to obtain C-3Cu.

[0066] 4) Demolding C-3Cu and drying at 20°C for 3 h to obtain D-3Cu;

[0067] 5) Place D-3Cu in air at 520 o C was calcined for 3 h to obtain the monolithic catalyst E-3Cu.

[0068] Example 3

[0069] 1) Aluminum foil and hydrochloric acid were stirred in a molar ratio of 1.6:1 to obtain an aluminum sol with a solid content of 23 wt.% and a density of 1.4 g / mL. Ferric nitrate nonahydrate was added, calculated as 3% of the mass of the aluminum sol, and 50% of manganese nitrate was added, calculated as 1% of the mass of the aluminum sol. The mixture was uniformly stirred and dissolved in the aluminum sol to obtain an iron-manganese-aluminum sol mixed solution A-3Fe1Mn.

[0070] 2) Aluminum sol A-3Fe1Mn was stirred at 3000 rpm using a mechanical stirrer, and 0.2 wt% sodium dodecyl sulfate was added to form pores to obtain B-3Fe1Mn;

[0071] 3) Add potassium chloride at a concentration of 0.08 mmol / g to B-3Fe1Mn, continue stirring at high speed, and inject into a mold with a diameter of 2 cm and a height of 10 cm to obtain C-3Fe1Mn.

[0072] 4) Demolding the C-3Fe1Mn and drying it at 30°C for 3 hours to obtain D-3Fe1Mn;

[0073] 5) D-3Fe1Mn was placed in air at 550 o C was calcined for 3 h to obtain the integral catalyst E-3Fe1Mn.

[0074] Example 4

[0075] 1) Aluminum foil and hydrochloric acid were stirred in a molar ratio of 1.6:1 to obtain an aluminum sol with a solid content of 23 wt.% and a density of 1.4 g / mL. Ferric nitrate nonahydrate was added, accounting for 2.7% of the mass of the aluminum sol. Cobalt nitrate hexahydrate was then added, accounting for 0.3% of the mass of the aluminum sol. The mixture was uniformly stirred and dissolved in the aluminum sol to obtain an iron-cobalt-aluminum sol mixed solution A-2.7Fe0.3Co.

[0076] 2) Aluminum sol A-2.7Fe0.3Co was stirred at 3000 rpm using a mechanical stirrer, and 0.09 wt% sodium dodecyl sulfate was added to form pores to obtain B-2.7Fe0.3Co;

[0077] 3) Add 0.03 mmol / g of ammonium chloride to the B-3Fe1Co, continue stirring at high speed, and inject into a mold with a diameter of 2 cm and a height of 10 cm to obtain C-2.7Fe0.3Co.

[0078] 4) Demolding the C-3Fe1Co and drying at 35°C for 3 hours to obtain D-2.7Fe0.3Co;

[0079] 5) D-3Fe1Co was placed in air at 550 oC was calcined for 3 h to obtain the integral catalyst E-2.7Fe0.3Co.

[0080] Test Example 1

[0081] The monolithic catalysts prepared in Examples 1 to 4 were subjected to high-temperature Fenton oxidation treatment on acetonitrile wastewater obtained by distillation of actual acetonitrile wastewater from a preparative chromatography company. The test conditions and results are shown in Table 1.

[0082] Table 1

[0083]

[0084] The test results above demonstrate that the addition of various transition metals to alumina monolithic catalysts exhibits a certain degree of activity in the high-temperature Fenton reaction for treating acetonitrile wastewater. The addition of Mn improves the initial activity of the catalyst, while Fe exhibits better activity than Cu. The further addition of Co promotes the catalytic reaction of Fe-containing catalysts. The prepared alumina monolithic catalyst is suitable for advanced acetonitrile wastewater treatment using the high-temperature Fenton oxidation process. As a monolithic catalyst, it reduces bed resistance and prevents loss of active components, offering promising application prospects.

[0085] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A process for advanced treatment of acetonitrile wastewater, characterized in that: The acetonitrile wastewater advanced treatment process comprises the following steps: The acetonitrile wastewater is passed into a high-temperature Fenton oxidation reactor equipped with a monolithic catalyst to react in the presence of hydrogen peroxide; The preparation method of the monolithic catalyst comprises the following steps: S1. Adding a transition metal salt to the aluminum sol and mixing uniformly to obtain a solution A; S2. Adding a pore-forming agent to solution A under stirring to obtain solution B; S3. Under stirring conditions, a coagulant is added to solution B to obtain solution C, and then solution C is injected into a mold for curing, and demolding is performed to obtain a gel product C-3; S4, drying the gel product C-3 to obtain a solid product D-3; S5. calcining the solid product D-3 to obtain a monolithic catalyst; In step S1, the aluminum sol is obtained by reacting aluminum foil and hydrochloric acid; The molar ratio of aluminum element to hydrochloric acid in the aluminum foil is 1.3-1.8:1; The amount of transition metal salt added to solution A, calculated as transition metal element, is 0.5-10 wt.% of the weight of the monolithic catalyst; The transition metal salt is selected from the nitrate or sulfate of at least one of iron, cobalt, manganese, titanium and copper; In step S2, the pore-forming agent is selected from at least one of ammonium lauryl sulfate, sodium lauryl sulfate, and glycerol; The amount of the pore-forming agent is 0.01-0.25 wt.% of the weight of solution A; In step S3, the coagulant is selected from at least one of ammonium chloride, potassium chloride, potassium hydroxide, and calcium chloride; The content of the heavy coagulant in the solution C is 0.01-0.10 mmol / g.

2. The acetonitrile wastewater advanced treatment process according to claim 1, wherein In step S4, the drying conditions include: a temperature of 20-50° C. and a drying time of 3-8 hours.

3. The acetonitrile wastewater advanced treatment process according to claim 1, wherein In step S5, the calcination conditions include: a calcination temperature of 480-560° C. and a calcination time of 2-5 hours.

4. The acetonitrile wastewater advanced treatment process according to claim 1, wherein The dimensions of the monolithic catalyst are: 2-10 cm in height and 2-10 cm in diameter; The porosity of the monolithic catalyst is 60~90%.

5. The acetonitrile wastewater advanced treatment process according to claim 1, wherein The residual temperature of the acetonitrile wastewater is 40-90° C., the concentration of the acetonitrile wastewater is 0.02-0.06%, and the TOC concentration of the acetonitrile wastewater is 100-300 mg / L; The reaction conditions include: the initial pH of the acetonitrile wastewater is 2-7, mH2O2:mTOC=1.5-17.5:1, and the volume space velocity of the acetonitrile wastewater is 0.5-6h -1 .

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