A method for treating oily wastewater

Abstract

The present invention provides a method for treating oily wastewater. The method relates to the field of oily wastewater treatment. A solid-oil-water slurry phase obtained by mixing a hydrophobic ZIF material with oily wastewater and allowing it to stand is placed in an acidic environment. The oil-containing hydrophobic ZIF material is dissolved with acid, and a ligand corresponding to the hydrophobic ZIF material is added to the aqueous phase after acid hydrolysis to recover the hydrophobic ZIF material and the oil. Through acid hydrolysis, the hydrophobic ZIF material is decomposed into its constituent components in an acidic environment, and oil substances can be completely released, avoiding the situation where oil substances remain on the solid material, thereby improving the oil recovery rate and recycling the hydrophobic ZIF material, reducing material consumption and waste generation.

Description

Technical Field

[0001] The present invention relates to the field of oily wastewater treatment, and in particular to a method for treating oily wastewater. Background Art

[0002] Oily wastewater is a common industrial wastewater source, primarily from the petroleum industry, machinery manufacturing, chemical industry, and pharmaceutical industry. This wastewater contains large amounts of organic substances such as grease, mineral oil, and lubricants. If discharged directly without treatment, it can cause serious environmental pollution. Removing and recovering oil from oily wastewater can improve the economic benefits of energy companies while minimizing the impact on the ecological environment, achieving environmental protection goals.

[0003] Traditional methods for treating oily wastewater primarily include physical, chemical, and biological methods. Physical methods include gravity separation, centrifugation, and filtration; chemical methods include flocculation, flotation, and chemical oxidation; and biological methods utilize the metabolic activity of microorganisms to degrade oil pollutants into harmless substances. However, traditional methods have several limitations when treating oily wastewater: physical methods are less effective for treating small oil droplets and emulsified oil; chemical methods require the addition of large amounts of chemicals, resulting in high treatment costs and the potential for secondary pollution; and biological methods are less effective for treating highly concentrated and toxic oily wastewater.

[0004] Hydrophobic ZIF materials have gained popularity in the oily wastewater treatment industry due to their excellent hydrophobicity and chemical stability, high specific surface area, high porosity, and functional tunability. Currently, after using hydrophobic ZIF materials to treat oily wastewater, they are often separated from the oil through physical extrusion, centrifugation, or solvent washing, allowing the ZIF materials to be reused for oily wastewater treatment.

[0005] However, the oil recovered by physical extrusion is limited, and a large part of it will remain in the ZIF material, which also affects the secondary use of the material; centrifugal separation is affected by equipment costs and material density differences, and is not widely used; solvent washing has an impact on the environment on the one hand, and on the other hand, certain solvents may also affect the structure of the ZIF material, reducing its adsorption capacity, thereby affecting its recycling. Summary of the Invention

[0006] In view of the technical problems existing in the prior art, the present invention aims to provide a method for treating oily wastewater, which comprises the following steps:

[0007] S1: mixing the hydrophobic ZIF material with oily wastewater to form a solid-liquid mixed system, and then performing static stratification to obtain a solid-oil-water slurry phase and a clear water phase, and separating the two phases;

[0008] S2: adding acid solution or introducing acid gas to the solid-oil-water slurry phase until all the solids are dissolved, and then standing to separate the water phase and the oil phase, which are then separated and recovered;

[0009] S3 adds the corresponding organic ligand of the hydrophobic ZIF material to the aqueous phase, raises the temperature to 50~70℃, and continuously stirs to obtain a white slurry. The white slurry is filtered to obtain the recovered hydrophobic ZIF material and water. The recovered hydrophobic ZIF material can be reused for oily wastewater treatment.

[0010] The molar ratio of the organic ligand in step S3 to the hydrophobic ZIF material in step S1 is 1-4:1.

[0011] Preferably, the oil content of the oily wastewater is 50 mg / L~100000 mg / L, and the pH is 7~14.

[0012] Preferably, the oily wastewater includes but is not limited to electro-desalted wastewater or oilfield produced water.

[0013] Preferably, the particle size of the hydrophobic ZIF material is 0.001 μm to 500 μm.

[0014] Preferably, the particle size of the hydrophobic ZIF material is preferably 0.2 μm to 10 μm.

[0015] Preferably, the mass ratio of the hydrophobic ZIF material to the oil in the oily wastewater is 0.88~2:1.

[0016] Preferably, the dosage of the hydrophobic ZIF material is 100 mg / L to 200,000 mg / L.

[0017] Preferably, the hydrophobic ZIF material includes one or more of ZIF-7, ZIF-8, ZIF-11 or ZIF-90.

[0018] Preferably, the mixing operation method includes high-speed stirring, ultrasound or shaking;

[0019] Preferably, the mixing operation method includes high-speed stirring, and the stirring speed is 500 rpm.

[0020] Preferably, the pH of the acid solution is 1-6.

[0021] Preferably, the acidic environment includes hydrochloric acid, sulfuric acid aqueous solution, sulfurous acid aqueous solution, acetic acid aqueous solution, formic acid aqueous solution or oxalic acid aqueous solution; the acidic gas includes CO2;

[0022] Preferably, the CO2 injection pressure is 0.15~0.25MPa.

[0023] Beneficial effects of the present invention:

[0024] The present invention places the solid-oil-water slurry phase obtained by mixing a hydrophobic ZIF material with oily wastewater and letting it stand in an acidic environment, dissolves the oil-containing hydrophobic ZIF material with acid, and adds the corresponding ligand of the hydrophobic ZIF material to the aqueous phase after acid hydrolysis to recover the hydrophobic ZIF material and oil.

[0025] Through acid hydrolysis, the hydrophobic ZIF material is decomposed into its constituent components in an acidic environment, and the oil substances can be completely released, avoiding the situation where they remain on the solid material, thereby improving the oil recovery rate.

[0026] Adding the appropriate ligand to the aqueous phase after acid hydrolysis can regenerate the hydrophobic ZIF material, allowing it to be reused for oily wastewater treatment. This process allows for the recycling of the hydrophobic ZIF material, reducing material consumption and waste generation, and improving the economic and environmental performance of the entire process. The acid hydrolysis and regeneration steps are relatively simple, can be implemented on an industrial scale, and are economically feasible. DETAILED DESCRIPTION

[0027] According to a first aspect of the present invention, a method for treating oily wastewater is provided, the method comprising the following steps:

[0028] S1: mixing the hydrophobic ZIF material with oily wastewater to form a solid-liquid mixed system, and then performing static stratification to obtain a solid-oil-water slurry phase and a clear water phase, and separating the two phases;

[0029] S2: placing the solid-oil-water slurry phase in an acidic environment, allowing it to stand for stratification to obtain a water phase and an oil phase, which are then separated and recovered;

[0030] S3 adds the corresponding organic ligand of the hydrophobic ZIF material to the aqueous phase, raises the temperature to 50~70℃, and continues stirring for 0.5~1.5h to obtain a white slurry. The white slurry is filtered to obtain the recovered hydrophobic ZIF material and water. The recovered hydrophobic ZIF material can be reused for oily wastewater treatment.

[0031] The molar ratio of the organic ligand in step S3 to the hydrophobic ZIF material in step S1 is 1-4:1.

[0032] In the present invention, the hydrophobic ZIF material decomposes into its constituent components in an acidic environment, completely releasing the oil. This process effectively separates the hydrophobic ZIF material from the oil, avoiding the incomplete separation that can occur during conventional mechanical separation. Adding a corresponding ligand to the aqueous phase after acid hydrolysis can promote the regeneration of the hydrophobic ZIF material, enabling its recycling and reuse.

[0033] If the molar ratio of the organic ligand in step S3 to the hydrophobic ZIF material in step S1 is greater than 4:1, the ligand will be wasted; if the molar ratio is less than 1:1, the hydrophobic ZIF material cannot be completely recovered.

[0034] In the present invention, the standing and stratification time is 1 to 12 hours, and the standing and stratification time is, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours.

[0035] In a preferred embodiment of the present invention, the oil content of the oily wastewater is 50 mg / L-100,000 mg / L, and the pH is 7-14.

[0036] In the present invention, the oil in the oily wastewater includes small-sized oil droplets such as dissolved oil or emulsified oil, and the alkaline environment with a pH of 7 to 14 ensures the stable existence of the hydrophobic ZIF material in the oily wastewater.

[0037] In a preferred embodiment of the present invention, the oily wastewater includes but is not limited to electro-desalted wastewater or oilfield produced water.

[0038] In a preferred embodiment of the present invention, the particle size of the hydrophobic ZIF material is 0.001 μm to 500 μm.

[0039] In a preferred embodiment of the present invention, the particle size of the hydrophobic ZIF material is preferably 0.2 μm to 10 μm.

[0040] In the present invention, the smaller particle size of the hydrophobic ZIF material means a larger specific surface area, which can provide more active sites for the adsorption of oil substances. Therefore, ZIF materials with small particle size can usually adsorb oil substances in wastewater more quickly and efficiently. For larger particles, due to the smaller specific surface area and fewer adsorption sites, the adsorption efficiency is reduced, and the removal effect of oil substances is not as good as that of small particle size materials. Therefore, the particle size of the hydrophobic ZIF material is not higher than 500μm. However, smaller particles require greater costs in the synthesis process, and the adsorption capacity advantage of small particles decreases as the particle size becomes smaller. Therefore, the minimum particle size of the hydrophobic ZIF material is not less than 0.001μm

[0041] In a preferred embodiment of the present invention, the mass ratio of the hydrophobic ZIF material to the oil in the oily wastewater is 0.88-2:1.

[0042] In a preferred embodiment of the present invention, the dosage of the hydrophobic ZIF material is 100 mg / L to 200,000 mg / L.

[0043] In a preferred embodiment of the present invention, the hydrophobic ZIF material includes one or more of ZIF-8, ZIF-61, ZIF-67 or ZIF-72.

[0044] In the present invention, the hydrophobic ZIF material is, for example, ZIF-8, ZIF-61, ZIF-67, ZIF-72, ZIF-61 and ZIF-8, ZIF-8 and ZIF-67, ZIF-61 and ZIF-67, ZIF-8, ZIF-61 and ZIF-67, ZIF-8, ZIF-61 and ZIF-72, or ZIF-67, ZIF-8 and ZIF-72.

[0045] In a preferred embodiment of the present invention, the mixing operation method includes high-speed stirring, ultrasound or shaking;

[0046] Preferably, the mixing operation method includes high-speed stirring, and the stirring speed is 500 rpm.

[0047] In a preferred embodiment of the present invention, the pH of the acid solution is 3-5.

[0048] In a preferred embodiment of the present invention, the acid solution includes hydrochloric acid, sulfuric acid aqueous solution, sulfurous acid aqueous solution, acetic acid aqueous solution, formic acid aqueous solution or oxalic acid aqueous solution;

[0049] In the present invention, the acid solution is, for example, hydrochloric acid, sulfuric acid aqueous solution, sulfurous acid aqueous solution, acetic acid aqueous solution, formic acid aqueous solution or oxalic acid aqueous solution;

[0050] In a preferred embodiment of the present invention, the acid gas includes CO2;

[0051] Preferably, the CO2 injection pressure is 0.15~0.25MPa.

[0052] In the present invention, the CO2 introduction pressure is, for example, 0.15 MPa, 0.16 MPa, 0.17 MPa, 0.18 MPa, 0.19 MPa, 0.20 MPa, 0.21 MPa, 0.22 MPa, 0.23 MPa, 0.24 MPa or 0.25 MPa.

[0053] In the present invention, the method for treating the oily wastewater is specifically as follows:

[0054] S1: adding a hydrophobic ZIF material to oily wastewater and stirring at a high speed of 500 rpm. The mass ratio of the hydrophobic ZIF material to the oil in the oily wastewater is 0.88 to 2:1, and the amount of the hydrophobic ZIF material added is 100 mg / L to 200,000 mg / L. After forming a solid-liquid mixed system, the mixture is allowed to stand until stratification occurs, obtaining a solid-oil-water slurry phase and a clear water phase, and the two phases are separated.

[0055] S2: adding acid or introducing acid gas to the solid-oil-water slurry phase until all the solids are dissolved, and allowing it to stand until the phases separate to obtain a water phase and an oil phase, which are then separated and recovered;

[0056] S3 adds the corresponding organic ligand of the hydrophobic ZIF material to the aqueous phase, the molar ratio of the organic ligand to the hydrophobic ZIF material in step S1 is 1:1~5, stirs and heats to 50~70°C, and continues stirring for 0.5~1.5h to obtain a white slurry, and the white slurry is filtered to obtain the recovered hydrophobic ZIF material and water. The recovered hydrophobic ZIF material can be reused for oily wastewater treatment.

[0057] Example 1

[0058] In this embodiment, the hydrophobic ZIF material selected is ZIF-8, and the oily wastewater selected is oilfield produced water with an oil content of 500 mg / L.

[0059] Experimental steps:

[0060] S1: Take 0.1L of oilfield produced water, add 100mg of ZIF-8 material, stir at a stirring speed of 500rpm to form a solid-liquid mixed system, let it stand until the layers are separated, and obtain a solid-oil-water slurry phase and a clear water phase, and separate the two phases;

[0061] S2 takes the solid-oil-water slurry phase and introduces CO2 at a pressure of 0.20 MPa until all the solids are dissolved. Let it stand until the phases are separated to obtain the water phase and the oil phase. The oil phase and the water phase are separated and recovered.

[0062] S3: Add 36 mg of 2-methylimidazole, the organic ligand corresponding to the ZIF-8 material, to the aqueous phase, stir and heat to 60°C, and continue stirring for 1 hour to obtain a white slurry. Filter the white slurry to obtain the recovered hydrophobic ZIF material and water.

[0063] The oil content in the water was detected to be 20 mg / L, the oil recovery rate was 98%, and the ZIF-8 material recovery rate was 98%.

[0064] The recovered ZIF-8 material was subjected to another experiment according to the above experimental steps, that is, 98 mg of the recovered ZIF-8 material was added to 0.098 L of oilfield produced water to perform oil-water separation.

[0065] The oil content in the water was detected to be 20 mg / L, the oil recovery rate was 97.8%, and the ZIF-8 material recovery rate was 98%.

[0066] Oil recovery rate = (mass of recovered oil / mass of oil in produced water from the oil field) × 100%;

[0067] ZIF material recovery rate = (mass of recovered ZIF material / mass of used ZIF material) × 100%.

[0068] Example 2

[0069] In this embodiment, the hydrophobic ZIF material selected is ZIF-61, and the oily wastewater selected is oilfield produced water with an oil content of 500 mg / L.

[0070] Experimental steps:

[0071] S1: Take 0.1L of oilfield produced water, add 80mg of ZIF-61 material, stir at a stirring speed of 500rpm to form a solid-liquid mixed system, let it stand until the layers are separated, and obtain a solid-oil-water slurry phase and a clear water phase, and separate the two phases;

[0072] S2 takes the solid-oil-water slurry phase and introduces CO2 at a pressure of 0.15 MPa until all the solids are dissolved. After standing until separation, the water phase and the oil phase are obtained. The oil phase and the water phase are separated and recovered.

[0073] S3: Add 30 mg of imidazole and 36 mg of 2-methylimidazole, the corresponding organic ligands of ZIF-61 material, to the aqueous phase, stir and heat to 60°C, and continue stirring for 1 hour to obtain a white slurry. Filter the white slurry to obtain the recovered hydrophobic ZIF material and water.

[0074] The oil content in the water was detected to be 21 mg / L, the oil recovery rate was 95.8%, and the ZIF-61 material recovery rate was 95%.

[0075] The recovered ZIF-61 material was subjected to another experiment according to the above experimental steps, that is, 76 mg of the recovered ZIF-61 material was added to 0.095 L of oilfield produced water to perform oil-water separation.

[0076] The oil content in the water was detected to be 21 mg / L, the oil recovery rate was 95.8%, and the ZIF-61 material recovery rate was 95%.

[0077] Example 3

[0078] In this embodiment, the hydrophobic ZIF material selected is ZIF-67, and the oily wastewater selected is oilfield produced water with an oil content of 500 mg / L.

[0079] Experimental steps:

[0080] S1: Take 0.1L of oilfield produced water, add 62mg of ZIF-67 material, stir at a stirring speed of 500rpm to form a solid-liquid mixed system, let it stand until the layers separate, and obtain a solid-oil-water slurry phase and a clear water phase, and separate the two phases;

[0081] S2 takes the solid-oil-water slurry phase and introduces CO2 at a pressure of 0.25 MPa until all the solids are dissolved. Let it stand until the phases are separated to obtain the water phase and the oil phase. The oil phase and the water phase are separated and recovered.

[0082] S3: Add 36.1 mg of 2-methylimidazole, the organic ligand corresponding to the ZIF-67 material, to the aqueous phase, stir and heat to 60°C, and continue stirring for 1 hour to obtain a white slurry. Filter the white slurry to obtain the recovered ZIF-67 material and water.

[0083] The oil content in the water was detected to be 30 mg / L, the oil recovery rate was 95.7%, and the ZIF-67 material recovery rate was 95%.

[0084] The recovered ZIF-67 material was subjected to another experiment according to the above experimental steps, that is, 58.9 mg of the recovered ZIF-67 material was added to 0.095 L of oilfield produced water to perform oil-water separation.

[0085] The oil content in the water was detected to be 30 mg / L, the oil recovery rate was 95.7%, and the ZIF-67 material recovery rate was 95%.

[0086] Example 4

[0087] In this embodiment, the hydrophobic ZIF material selected is ZIF-72, and the oily wastewater selected is oilfield produced water with an oil content of 500 mg / L.

[0088] Experimental steps:

[0089] S1: Take 0.1L of oilfield produced water, add 44mg of ZIF-72 material, stir at a stirring speed of 500rpm to form a solid-liquid mixed system, let it stand until the layers separate, and obtain a solid-oil-water slurry phase and a clear water phase, and separate the two phases;

[0090] S2 takes the solid-oil-water slurry phase and introduces CO2 at a pressure of 0.15 MPa until all the solids are dissolved. After standing until separation, the water phase and the oil phase are obtained. The oil phase and the water phase are separated and recovered.

[0091] S3: Add 70 mg of 4,5-dichloroimidazole, the organic ligand corresponding to the ZIF-72 material, to the aqueous phase, stir and heat to 60°C, and continue stirring for 1 hour to obtain a white slurry. Filter the white slurry to obtain the recovered ZIF-72 material and water.

[0092] The oil content in the water was detected to be 21 mg / L, the oil recovery rate was 93%, and the ZIF-72 material recovery rate was 95%.

[0093] The recovered ZIF-72 material was subjected to another experiment according to the above experimental steps, that is, 41.8 mg of the recovered ZIF-72 material was added to 0.095 L of oilfield produced water for oil-water separation.

[0094] The oil content in the water was detected to be 21 mg / L, the oil recovery rate was 93%, and the ZIF-72 material recovery rate was 95%.

[0095] Example 5

[0096] In this embodiment, the hydrophobic ZIF material selected is ZIF-8, and the oily wastewater selected is electro-desalted wastewater with an oil content of 100,000 mg / L.

[0097] Experimental steps:

[0098] S1: Take 0.1L of oilfield produced water, add 20g of ZIF-8 material, stir at a stirring speed of 500rpm to form a solid-liquid mixed system, let it stand until it delaminates, and obtain a solid-oil-water slurry phase and a clear water phase, and separate the two phases;

[0099] S2 takes the solid-oil-water slurry phase and introduces CO2 at a pressure of 0.20 MPa until all the solids are dissolved. Let it stand until the phases are separated to obtain the water phase and the oil phase. The oil phase and the water phase are separated and recovered.

[0100] S3: Add 36 g of 2-methylimidazole, the organic ligand corresponding to the ZIF-8 material, to the aqueous phase, stir and heat to 60°C, and continue stirring for 1 hour to obtain a white slurry. Filter the white slurry to obtain the recovered ZIF-8 material and water.

[0101] The oil content in the water was detected to be 21 mg / L, the oil recovery rate was 99.8%, and the ZIF-8 material recovery rate was 98.5%.

[0102] The recovered ZIF-8 material was subjected to another experiment according to the above experimental steps, that is, 19.7 g of the recovered ZIF-8 material was added to 0.0985 L of oilfield produced water to perform oil-water separation.

[0103] The oil content in the water was detected to be 21 mg / L, the oil recovery rate was 99.8%, and the ZIF-8 material recovery rate was 98.5%.

[0104] Example 6

[0105] In this embodiment, the hydrophobic ZIF material selected is ZIF-8, and the oily wastewater selected is oilfield produced water with an oil content of 50 mg / L.

[0106] Experimental steps:

[0107] S1: Take 0.1L of oilfield produced water, add 10mg of ZIF-8 material, stir at a stirring speed of 500rpm to form a solid-liquid mixed system, let it stand until the layers separate, and obtain a solid-oil-water slurry phase and a clear water phase, and separate the two phases;

[0108] S2 takes the solid-oil-water slurry phase and introduces CO2 at a pressure of 0.20 MPa until all the solids are dissolved. Let it stand until the phases are separated to obtain the water phase and the oil phase. The oil phase and the water phase are separated and recovered.

[0109] S3: Add 3.6 mg of 2-methylimidazole, the organic ligand corresponding to the ZIF-8 material, to the aqueous phase, stir and heat to 60°C, and continue stirring for 1 hour to obtain a white slurry. Filter the white slurry to obtain the recovered ZIF-8 material and water.

[0110] The oil content in the water was detected to be 8 mg / L, the oil recovery rate was 92%, and the ZIF-8 material recovery rate was 95%.

[0111] The recovered ZIF-8 material was subjected to another experiment according to the above experimental steps, that is, 19 mg of the recovered ZIF-8 material was added to 0.095 L of oilfield produced water to perform oil-water separation.

[0112] The oil content in the water was detected to be 8 mg / L, the oil recovery rate was 92%, and the ZIF-8 material recovery rate was 95%.

[0113] Example 7

[0114] In this embodiment, the hydrophobic ZIF material selected is ZIF-8, and the oily wastewater selected is oilfield produced water with an oil content of 500 mg / L.

[0115] Experimental steps:

[0116] S1: Take 0.1L of oilfield produced water, add 100mg of ZIF-8 material, stir at a stirring speed of 500rpm to form a solid-liquid mixed system, let it stand until the layers are separated, and obtain a solid-oil-water slurry phase and a clear water phase, and separate the two phases;

[0117] S2: Take the solid-oil-water slurry phase and add hydrochloric acid with a pH of 3 until all the solids are dissolved. Let it stand until the phases separate to obtain the water phase and the oil phase. Separate and recover the oil phase and the water phase.

[0118] S3: Add 143 mg of 2-methylimidazole, the organic ligand corresponding to the ZIF-8 material, to the aqueous phase, stir and heat to 60°C, and continue stirring for 1 hour to obtain a white slurry. Filter the white slurry to obtain the recovered ZIF-8 material and water.

[0119] The oil content in the water was detected to be 23 mg / L, the oil recovery rate was 94.5%, and the ZIF-8 material recovery rate was 98%.

[0120] The recovered ZIF-8 material was subjected to another experiment according to the above experimental steps, that is, 98 mg of the recovered ZIF-8 material was added to 0.098 L of oilfield produced water to perform oil-water separation.

[0121] The oil content in the water was detected to be 23 mg / L, the oil recovery rate was 94.5%, and the ZIF-8 material recovery rate was 98%.

[0122] Example 8

[0123] In this embodiment, the hydrophobic ZIF material selected is ZIF-8, and the oily wastewater selected is oilfield produced water with an oil content of 500 mg / L.

[0124] Experimental steps:

[0125] S1: Take 0.1L of oilfield produced water, add 100mg of ZIF-8 material, stir at a stirring speed of 500rpm to form a solid-liquid mixed system, let it stand until the layers are separated, and obtain a solid-oil-water slurry phase and a clear water phase, and separate the two phases;

[0126] S2: Take the solid-oil-water slurry phase and add acetic acid with a pH of 3 until all the solids are dissolved. Let it stand until the phases separate to obtain the water phase and the oil phase. Separate and recover the oil phase and the water phase.

[0127] S3: Add 107.5 mg of 2-methylimidazole, the organic ligand corresponding to the ZIF-8 material, to the aqueous phase, stir and heat to 60°C, and continue stirring for 1 hour to obtain a white slurry. Filter the white slurry to obtain the recovered ZIF-8 material and water.

[0128] The oil content in the detected water was 25 mg / L, the oil recovery rate was 95%, and the ZIF-8 material recovery rate was 98%.

[0129] The recovered ZIF-8 material was subjected to another experiment according to the above experimental steps, that is, 98 mg of the recovered ZIF-8 material was added to 0.098 L of oilfield produced water to perform oil-water separation.

[0130] The oil content in the detected water was 25 mg / L, the oil recovery rate was 95%, and the ZIF-8 material recovery rate was 98%.

Claims

1. A method for treating oily wastewater, characterized in that: The method comprises the following steps: S1: mixing the hydrophobic ZIF material with oily wastewater to form a solid-liquid mixed system, and then performing static stratification to obtain a solid-oil-water slurry phase and a clear water phase, and separating the two phases; S2: adding acid or introducing acid gas to the solid-oil-water slurry phase until the solid is completely dissolved, the hydrophobic ZIF material is decomposed into its constituent components in the acidic environment, and the oil substances are completely released. After standing and stratification, the water phase and the oil phase are obtained, and the oil phase and the water phase are separated and recovered; S3: adding the corresponding organic ligand of the hydrophobic ZIF material to the aqueous phase, heating to 50-70°C, and continuously stirring to obtain a white slurry. The white slurry is filtered to obtain the recovered hydrophobic ZIF material and water. The recovered hydrophobic ZIF material can be reused for oily wastewater treatment; The molar ratio of the organic ligand in step S3 to the hydrophobic ZIF material in step S1 is 1-4:1; the oil content of the oily wastewater is 50 mg / L-100,000 mg / L, and the pH is 7-14.

2. The method for treating oily wastewater according to claim 1, wherein: The oily wastewater includes but is not limited to electro-desalted wastewater or oilfield produced water.

3. The method for treating oily wastewater according to claim 1, wherein: The particle size of the hydrophobic ZIF material is 0.001 μm to 500 μm.

4. The method for treating oily wastewater according to claim 1, wherein: The particle size of the hydrophobic ZIF material is 0.2 μm to 10 μm.

5. The method for treating oily wastewater according to claim 1, wherein: The mass ratio of the hydrophobic ZIF material to the oil in the oily wastewater is 0.88-2:

1.

6. The method for treating oily wastewater according to claim 1, wherein: The dosage of the hydrophobic ZIF material is 100 mg / L~200000 mg / L.

7. The method for treating oily wastewater according to claim 1, wherein: The hydrophobic ZIF material includes one or more of ZIF-8, ZIF-61, ZIF-67 or ZIF-72.

8. The method for treating oily wastewater according to claim 1, wherein: The mixing operation method includes high-speed stirring, ultrasound or shaking.

9. The method for treating oily wastewater according to claim 1, wherein: The pH of the acid solution is 1-6.

10. The method for treating oily wastewater according to claim 1, wherein: The acid solution includes hydrochloric acid, sulfuric acid aqueous solution, sulfurous acid aqueous solution, acetic acid aqueous solution, formic acid aqueous solution or oxalic acid aqueous solution, and the acid gas includes CO2; The CO2 introduction pressure is 0.15~0.25MPa.