A composite treatment agent for oily wastewater and its application

Abstract

The present invention relates to a composite treatment agent for oily wastewater and its application, belonging to the technical field of wastewater treatment. The composite treatment agent for oily wastewater of the present invention is mainly composed of the following components by weight: 25-35 parts of an aluminum salt flocculant, 8-12 parts of sodium polyacrylate, 4-9 parts of ethylenediaminetetraacetic acid salt, 2-6 parts of pyrophosphate, 1-4 parts of xanthan gum, 2-5 parts of an alkali metal salt of hexadecylbenzenesulfonate, 3-8 parts of alginate, 1-2 parts of a biological agent, and 5-10 parts of rare earth-modified attapulgite; the biological agent includes yeast, Bacillus subtilis, and lactic acid bacteria. The raw materials used in the composite treatment agent for oily wastewater of the present invention are low in toxicity, can avoid secondary pollution to the environment, are easy to use, require a small amount, have a high oil removal rate, and have a very obvious water purification effect. The water quality of the treated oilfield wastewater can meet the standards for reinjection into the formation and the comprehensive water quality discharge standards, and can reduce environmental pollution.

Description

Technical Field

[0001] The invention relates to a composite treating agent for oily sewage and application thereof, belonging to the technical field of sewage treatment. Background Art

[0002] Oily wastewater primarily originates from the following industrial sectors: petroleum, petrochemicals, steel, coking, gasification plants, and machining. Oily wastewater contains oily pollutants. Among these oily pollutants, only heavy tar has a relative density of 1.1; the relative densities of other oils are less than 1. Therefore, oily wastewater can have adverse effects on humans, animals, plants, and even the entire ecosystem. Furthermore, the oily pollutants in oily wastewater have significant potential as energy sources, particularly in oilfield production.

[0003] Oilfield oily wastewater has a complex composition, primarily derived from drilling wastewater, well-washing wastewater, acid fracturing fluid wastewater, and produced fluids. Oilfield oily wastewater contains not only emulsified oil but also sand, gravel, solid particles, and various metal ions. Consequently, with increasing demands for oilfield oily wastewater treatment, currently used sedimentation and filtration processes are no longer sufficient. To more effectively remove pollutants from oily wastewater, a variety of oily wastewater treatment agents have been developed. For example, Chinese patent application CN 108046349 A discloses an oilfield wastewater treatment agent comprising the following raw materials: aluminum sulfate, sodium polyacrylate, tea saponin crystals, hydroxylated lecithin, disodium EDTA, sodium malate, sodium chloride, grapefruit peel powder, guar gum, sodium lauryl sulfate, diazolidinyl urea, and a bio-infectant; the bio-infectant is selected from yeast, Bacillus subtilis, or lactic acid bacteria. When used to treat oily wastewater from oilfields, this oilfield wastewater treatment agent has the advantages of low dosage, high oil removal rate, and significant water purification. However, this oilfield wastewater treatment agent still suffers from low oil removal rate and large dosage requirements. Chinese patent application CN106335948A discloses an oilfield wastewater treatment agent composed of the following raw materials, by weight: 28-36 parts activated carbon, 7-15 parts hollow wood, 3-8 parts montan wax, 12-20 parts hydrogen peroxide, and 15-23 parts acrylic emulsion. This oilfield wastewater treatment agent has the advantages of fast treatment speed, good treatment effect, no secondary water pollution, recyclability, low production cost, and no corrosion or damage to treatment equipment. However, the preparation cost of this oilfield wastewater treatment agent is relatively high.

[0004] Therefore, there is an urgent need to develop a low-cost composite oily wastewater treatment agent that can effectively remove pollutants in oily wastewater. Summary of the Invention

[0005] The object of the present invention is to provide a composite oily wastewater treating agent which has low cost and can effectively remove pollutants in the oily wastewater.

[0006] Another object of the present invention is to provide an application of a composite oily wastewater treatment agent in treating oily wastewater in oil fields.

[0007] In order to achieve the above objectives, the technical solution adopted by the composite treatment agent for oily wastewater of the present invention is:

[0008] A composite treatment agent for oily wastewater mainly consists of the following components in parts by mass: 25-35 parts of an aluminum salt flocculant, 8-12 parts of sodium polyacrylate, 4-9 parts of ethylenediaminetetraacetate, 2-6 parts of pyrophosphate, 1-4 parts of xanthan gum, 2-5 parts of an alkali metal salt of hexadecylbenzenesulfonate, 3-8 parts of alginate, 1-2 parts of a biological agent, and 5-10 parts of rare earth-modified attapulgite; the biological agent comprises yeast, Bacillus subtilis, and lactic acid bacteria, and the total number of viable yeast cells, Bacillus subtilis, and lactic acid bacteria in each gram of the biological agent is 34 billion to 60 billion CFU.

[0009] The composite oily wastewater treatment agent of the present invention is easy to use, readily marketable, and highly valuable. Furthermore, it requires only a small amount of water, achieves a high oil removal rate, and significantly improves water purification. The water quality of treated oilfield wastewater meets standards for reinjection into formations and comprehensive water quality discharge, thereby reducing environmental pollution. Furthermore, the raw materials used in the composite oily wastewater treatment agent of the present invention are less toxic, thus avoiding secondary environmental pollution. This makes the agent more environmentally friendly, highly competitive, and highly productive. Among them, aluminum salt flocculants have a flocculating effect and can remove solid impurities in oily wastewater; sodium polyacrylate has a scale inhibition effect and can prevent scaling of conveying pipelines and treatment containers; in oilfield wastewater, the metal ions with high content and easy to form scale salts are mainly divalent calcium and magnesium ions. Ethylenediaminetetraacetic acid can effectively prevent metal ions such as calcium and magnesium from chemically reacting to form scale-like precipitation through chelation; pyrophosphate is a synergist that can improve the flocculating effect of aluminum salt flocculants; xanthan gum has good water solubility, thickening properties, stability to acid and alkali, and stability to enzymatic reactions. It is used to accelerate degradation with increasing temperature, and is not easy to flocculate. It has antioxidant and anti-enzymatic capabilities, can increase the duration and meets environmental protection requirements. At the same time, the cost of use is low; alkylbenzene sulfonates have the effect of reducing oil-water interfacial tension; alginate has an ion exchange effect; biological bacterial agents have the effect of removing organic matter; rare earth-modified attapulgite has an adsorption effect.

[0010] Preferably, the total number of viable yeast, Bacillus subtilis, and lactic acid bacteria per 1g of the biological agent is 45 billion CFU to 49.2 billion CFU. Preferably, the ratio of the number of viable yeast, Bacillus subtilis, and lactic acid bacteria in the biological agent is (6-12):(20-50):(1-2).

[0011] Preferably, the aluminum salt flocculant is aluminum sulfate and / or polyaluminum chloride. Preferably, the EDTA salt is selected from one or any combination of disodium EDTA, dipotassium EDTA, and tetrasodium EDTA.

[0012] Preferably, the pyrophosphate is an alkali metal pyrophosphate. For example, the pyrophosphate is sodium pyrophosphate. Preferably, the alginate is an alkali metal alginate. For example, the alginate is sodium alginate.

[0013] Preferably, the viscosity average molecular weight of the sodium polyacrylate is 1000 to 5000. When the molecular weight of the sodium polyacrylate is within the above range, it can be used as a scale inhibitor and dispersant and a corrosion inhibitor.

[0014] Preferably, the rare earth modified attapulgite is prepared by a method comprising the following steps: first, immersing the attapulgite in an acid solution and an alkali solution in sequence for immersion treatment, then calcining the attapulgite after the soaking treatment, and then crushing the calcined attapulgite to obtain attapulgite powder, and finally immersing the attapulgite powder in a rare earth treatment agent for modification treatment; the rare earth treatment agent is composed of the following components in parts by mass: 8 to 13 parts of polyethylene glycol, 5 to 8 parts of rare earth salt, 10 to 15 parts of alkylphenol polyoxyethylene ether, 3 to 7 parts of quaternary ammonium salt surfactant, and 200 to 250 parts of water.

[0015] Preferably, the particle size of the attapulgite is not less than 325 mesh.

[0016] Preferably, the rare earth salt is a rare earth sulfate and / or a rare earth nitrate. Preferably, the rare earth element in the rare earth salt is selected from one or any combination of cerium, neodymium, and lanthanum.

[0017] Preferably, the alkylphenol polyoxyethylene ether is nonylphenol polyoxyethylene ether. Preferably, the quaternary ammonium salt surfactant is selected from one or any combination of dodecyldimethylbenzylammonium bromide, dodecyldimethylbenzylammonium chloride, and dodecyldiethylbenzylammonium bromide. For example, the quaternary ammonium salt surfactant is dodecyldimethylbenzylammonium bromide.

[0018] Preferably, the viscosity average molecular weight of the polyethylene glycol is 200 to 600. For example, the viscosity average molecular weight of the polyethylene glycol is 400 to 600. Preferably, the acid solution is a phosphoric acid solution with a mass fraction of 1 to 3%; and the soaking time in the acid solution is 4 to 8 minutes.

[0019] Preferably, the alkali solution is a sodium hydroxide solution with a mass fraction of 1-3%, and the soaking time in the alkali solution is 2-4 minutes. Soaking the attapulgite soil, which has been soaked in an acid solution, in a sodium hydroxide solution with a mass fraction of 1-3% can produce an alkaline attapulgite bar, which is used to improve the acid resistance of the attapulgite bar.

[0020] Preferably, the calcination temperature is 700-750°C.

[0021] Preferably, the calcination treatment time is 1 to 2 hours.

[0022] Preferably, the particle size of the attapulgite powder is 0.16 mm to 0.25 mm.

[0023] Preferably, the modification treatment lasts for 4 to 6 hours. For example, the modification treatment lasts for 4 hours.

[0024] Preferably, after the modification treatment is completed, the modified system is subjected to solid-liquid separation, and the solid obtained by solid-liquid separation is dried to obtain rare earth-modified attapulgite. Preferably, the drying temperature is 300-350°C. For example, the drying temperature is 300°C.

[0025] The technical solution adopted by the application of the composite oily wastewater treatment agent of the present invention in treating oily wastewater in oil fields is:

[0026] The application of the above-mentioned composite oily wastewater treatment agent in treating oily wastewater in oil fields.

[0027] The composite oily wastewater treatment agent of the present invention has the advantages of high oil removal rate and obvious water purification effect when used to treat oily wastewater in oil fields. The treated water quality can meet the standards for reinjection into the formation and comprehensive water quality discharge standards, and can reduce environmental pollution.

[0028] Preferably, the ratio of the mass of the oil in the oilfield oily wastewater to the mass of the oily wastewater composite treatment agent is (3965-4025):(400-800).

[0029] Preferably, the mass of the oily wastewater composite treatment agent used for each 1L of oilfield oily wastewater is 400-800mg. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0031] The yeast used in Examples 1-3 of the present invention and Comparative Examples 1-4 was produced by Shandong Xinbaiyuan Biotechnology Co., Ltd., with a viable count of 20 billion CFU / g; Bacillus subtilis was produced by Shandong Xinfuwo Bioengineering Co., Ltd., with a viable count of 100 billion CFU / g; lactic acid bacteria was produced by Weifang Ruichen Biotechnology Co., Ltd., with a viable count of 10 billion CFU / g; sodium polyacrylate was a low molecular weight sodium polyacrylate (2000-5000) powder aqueous dispersant produced by Zouping County Delin New Materials Technology Co., Ltd.; the manufacturer of attapulgite was Shijiazhuang Yuanjing Mineral Products Co., Ltd.; the manufacturer of polyethylene glycol was Shandong Xincheng Chemical Co., Ltd.; and the manufacturer of rare earth salts was Shandong Desheng New Materials Co., Ltd.

[0032] 1. Specific embodiments of the composite treatment agent for oily wastewater of the present invention are as follows:

[0033] Example 1

[0034] The composite treatment agent for oily wastewater of this embodiment is composed of the following components in parts by mass: 25 parts of an aluminum salt flocculant, 8 parts of sodium polyacrylate, 4 parts of ethylenediaminetetraacetate, 2 parts of pyrophosphate, 1 part of xanthan gum, 2 parts of alkylbenzene sulfonate, 3 parts of alginate, 1 part of a biological agent, and 5 parts of rare earth-modified attapulgite; the aluminum salt flocculant is aluminum sulfate, the ethylenediaminetetraacetate is disodium ethylenediaminetetraacetate, the pyrophosphate is sodium pyrophosphate, the alkylbenzene sulfonate is sodium hexadecylbenzene sulfonate, and the alginate is sodium alginate; the biological agent is composed of yeast, Bacillus subtilis, and lactic acid bacteria in a mass ratio of 3:2:1; the total number of viable yeast, Bacillus subtilis, and lactic acid bacteria in each 1g of the biological agent is 450 CFU, and the ratio of the number of viable yeast, Bacillus subtilis, and lactic acid bacteria in the biological agent is 6:20:1.

[0035] Rare earth modified attapulgite is prepared by a method comprising the following steps:

[0036] (1) First, attapulgite with a particle size of 325 mesh was immersed in a 1% phosphoric acid solution for 4 minutes, and then immersed in a 1% sodium hydroxide solution for 2 minutes. The immersed attapulgite was rinsed with deionized water to obtain acid-base treated attapulgite.

[0037] (2) The acid-base treated attapulgite was placed in a calcining furnace and calcined at 700°C for 1 hour. The calcined attapulgite was then crushed and sieved to obtain calcined attapulgite (attapulgite powder) with a particle size of 0.16 mm to 0.25 mm.

[0038] (3) The calcined attapulgite with a particle size of 0.16 mm to 0.25 mm is immersed in a rare earth treatment agent for modification. The modification time is 4 hours, and then the modified system is filtered. The solid obtained by filtration is the modified attapulgite. The rare earth treatment agent is composed of the following components in parts by mass: 8 parts of polyethylene glycol, 5 parts of rare earth salt, 10 parts of alkylphenol polyoxyethylene ether, 3 parts of quaternary ammonium surfactant, and 200 parts of water. The viscosity average molecular weight of polyethylene glycol is 400; the rare earth salt is lanthanum sulfate; the alkylphenol polyoxyethylene ether is nonylphenol polyoxyethylene ether; the quaternary ammonium surfactant is dodecyldimethylbenzylammonium bromide;

[0039] (4) The modified attapulgite is placed in a drying oven at 300° C. for drying to a constant weight to obtain rare earth-modified attapulgite.

[0040] Example 2

[0041] The composite treatment agent for oily wastewater of this embodiment is composed of the following components in parts by mass: 30 parts of an aluminum salt flocculant, 10 parts of sodium polyacrylate, 8 parts of ethylenediaminetetraacetate, 4 parts of pyrophosphate, 3 parts of xanthan gum, 4 parts of alkylbenzene sulfonate, 6 parts of alginate, 1.5 parts of a biological agent, and 8 parts of rare earth-modified attapulgite; the aluminum salt flocculant is aluminum sulfate, the ethylenediaminetetraacetate is disodium ethylenediaminetetraacetate, the pyrophosphate is sodium pyrophosphate, the alkylbenzene sulfonate is sodium hexadecylbenzene sulfonate, and the alginate is sodium alginate; the biological agent is composed of yeast, Bacillus subtilis, and lactic acid bacteria in a mass ratio of 5:4:1.5; the total number of viable yeast, Bacillus subtilis, and lactic acid bacteria per 1 g of the biological agent is 490 CFU, and the ratio of the number of viable yeast, Bacillus subtilis, and lactic acid bacteria in the biological agent is 20:80:3.

[0042] Rare earth modified attapulgite is prepared by a method comprising the following steps:

[0043] (1) First, attapulgite with a particle size of 325 mesh was immersed in a 2% phosphoric acid solution for 6 minutes, and then immersed in a 2% sodium hydroxide solution for 3 minutes. The immersed attapulgite was rinsed with deionized water to obtain acid-base treated attapulgite.

[0044] (2) The acid-base treated attapulgite was placed in a calcining furnace and calcined at 730° C. for 1.5 h. The calcined attapulgite was then crushed and sieved to obtain calcined attapulgite (attapulgite powder) with a particle size of 0.16 mm to 0.25 mm.

[0045] (3) The calcined attapulgite with a particle size of 0.16 mm to 0.25 mm is immersed in a rare earth treatment agent for modification. The modification time is 4 hours, and then the modified system is filtered. The solid obtained by filtration is the modified attapulgite. The rare earth treatment agent is composed of the following components in parts by mass: 10 parts of polyethylene glycol, 7 parts of rare earth salt, 13 parts of alkylphenol polyoxyethylene ether, 5 parts of quaternary ammonium surfactant, and 220 parts of water. The viscosity average molecular weight of polyethylene glycol is 400; the rare earth salt is neodymium nitrate; the alkylphenol polyoxyethylene ether is nonylphenol polyoxyethylene ether; the quaternary ammonium surfactant is dodecyldimethylbenzylammonium bromide;

[0046] (4) The modified attapulgite is placed in a drying oven at 300° C. for drying to a constant weight to obtain rare earth-modified attapulgite.

[0047] Example 3

[0048] The composite treatment agent for oily wastewater of this embodiment is composed of the following components in parts by mass: 35 parts of an aluminum salt flocculant, 12 parts of sodium polyacrylate, 9 parts of ethylenediaminetetraacetate, 6 parts of pyrophosphate, 4 parts of xanthan gum, 5 parts of alkylbenzene sulfonate, 8 parts of alginate, 2 parts of a biological agent, and 10 parts of rare earth-modified attapulgite; the aluminum salt flocculant is aluminum sulfate, the ethylenediaminetetraacetate is disodium ethylenediaminetetraacetate, the pyrophosphate is sodium pyrophosphate, the alkylbenzene sulfonate is sodium hexadecylbenzene sulfonate, and the alginate is sodium alginate; the biological agent is composed of yeast, Bacillus subtilis, and lactic acid bacteria in a mass ratio of 6:5:2; the total number of viable yeast, Bacillus subtilis, and lactic acid bacteria per 1 g of the biological agent is 492 CFU, and the ratio of the number of viable yeast, Bacillus subtilis, and lactic acid bacteria in the biological agent is 6:25:1.

[0049] Rare earth modified attapulgite is prepared by a method comprising the following steps:

[0050] (1) First, attapulgite with a particle size of 325 mesh was immersed in a 3% phosphoric acid solution for 8 minutes, and then immersed in a 3% sodium hydroxide solution for 4 minutes. The immersed attapulgite was rinsed with deionized water to obtain acid-base treated attapulgite.

[0051] (2) The acid-base treated attapulgite was placed in a calcining furnace and calcined at 750°C for 2 hours. The calcined attapulgite was then crushed and sieved to obtain calcined attapulgite (attapulgite powder) with a particle size of 0.16 mm to 0.25 mm.

[0052] (3) The calcined attapulgite with a particle size of 0.16 mm to 0.25 mm is immersed in a rare earth treatment agent for modification. The modification time is 4 hours, and then the modified system is filtered. The solid obtained by filtration is the modified attapulgite. The rare earth treatment agent is composed of the following components in parts by mass: 13 parts of polyethylene glycol, 8 parts of rare earth salt, 15 parts of alkylphenol polyoxyethylene ether, 7 parts of quaternary ammonium salt surfactant, and 250 parts of water. The viscosity average molecular weight of polyethylene glycol is 600; the rare earth salt is cerium sulfate; the alkylphenol polyoxyethylene ether is nonylphenol polyoxyethylene ether; the quaternary ammonium salt surfactant is dodecyldimethylbenzylammonium bromide;

[0053] (4) The modified attapulgite is placed in a drying oven at 300° C. for drying to a constant weight to obtain rare earth-modified attapulgite.

[0054] Comparative Example 1

[0055] The only difference between the composite treating agent for oily wastewater of this comparative example and the composite treating agent for oily wastewater of Example 1 is that the mass fraction of the rare earth-modified attapulgite in the composite treating agent for oily wastewater of this comparative example is 0.

[0056] Comparative Example 2

[0057] The only difference between the composite treatment agent for oily wastewater in this comparative example and the composite treatment agent for oily wastewater in Example 1 is that the mass fraction of the biological agent in the composite treatment agent for oily wastewater in this comparative example is 0.

[0058] Comparative Example 3

[0059] The only difference between the composite treatment agent for oily wastewater in this comparative example and the composite treatment agent for oily wastewater in Example 1 is that the mass fraction of xanthan gum in the composite treatment agent for oily wastewater in this comparative example is 0.

[0060] Comparative Example 4

[0061] The only difference between the composite treating agent for oily wastewater of this comparative example and the composite treating agent for oily wastewater of Example 1 is that the mass fraction of pyrophosphate in the composite treating agent for oily wastewater of this comparative example is 0.

[0062] 2. Specific examples of the application of the composite oily wastewater treatment agent of the present invention in treating oily wastewater in oil fields are as follows:

[0063] The composite treating agent for oily wastewater of Examples 1-3 can be used to treat oily wastewater in oilfields.

[0064] Experimental example

[0065] Using oily wastewater from an oilfield as the experimental subject, 50 mL of the oily wastewater was first placed in a beaker. The composite oily wastewater treatment agents of Examples 1-3 and Comparative Examples 1-4 were then added (the addition amounts of the composite oily wastewater treatment agents were set at 400 mg / L and 800 mg / L, respectively). After stirring for 3 minutes, the wastewater was allowed to stand for 5 minutes to purify the wastewater. The oil content and turbidity of the wastewater before and after purification were measured, respectively. The results are shown in Tables 1 and 2. The turbidity was measured using turbidimetry, while the oil content of the wastewater was measured using a gravimetric method (using petroleum ether extraction followed by evaporation and weighing).

[0066] Table 1 Oil content and turbidity of sewage before and after purification when 400 mg / L of the oily sewage composite treatment agent of Examples 1-3 and Comparative Examples 1-4 was added to different sewage samples

[0067]

[0068] Note: The unit of turbidity is NTU.

[0069] Table 2 Oil content and turbidity of sewage before and after purification when 800 mg / L of the oily sewage composite treatment agent of Examples 1-3 and Comparative Examples 1-6 was added to different sewage samples

[0070]

[0071] Note: The unit of turbidity is NTU.

[0072] The results show that each component in the formula of the composite treating agent for oily wastewater of the present invention has a beneficial effect on the treatment of oily wastewater, and each component is indispensable.

Claims

1. A composite treatment agent for oily wastewater, characterized in that: The invention mainly comprises the following components in parts by weight: 25-35 parts of aluminum salt flocculant, 8-12 parts of sodium polyacrylate, 4-9 parts of ethylenediaminetetraacetic acid salt, 2-6 parts of pyrophosphate, 1-4 parts of xanthan gum, 2-5 parts of alkali metal salt of hexadecylbenzenesulfonate, 3-8 parts of alginate, 1-2 parts of biological bacteria agent and 5-10 parts of rare earth modified attapulgite; the biological bacteria agent comprises yeast, Bacillus subtilis and lactic acid bacteria, and the total number of live yeast, Bacillus subtilis and lactic acid bacteria in 1g of the biological bacteria agent is 34 billion CFU to 60 billion CFU; The rare earth modified attapulgite is prepared by a method comprising the following steps: first, immersing the attapulgite in an acid solution and an alkaline solution in sequence for immersion treatment, then calcining the soaked attapulgite, then crushing the calcined attapulgite to obtain attapulgite powder, and finally immersing the attapulgite powder in a rare earth treatment agent for modification treatment; the rare earth treatment agent is composed of the following components in parts by mass: 8 to 13 parts of polyethylene glycol, 5 to 8 parts of a rare earth salt, 10 to 15 parts of an alkylphenol polyoxyethylene ether, 3 to 7 parts of a quaternary ammonium salt surfactant, and 200 to 250 parts of water.

2. The composite treating agent for oily wastewater according to claim 1, wherein: The aluminum salt flocculant is aluminum sulfate and / or polyaluminum chloride; the EDTA salt is selected from one or any combination of disodium EDTA, dipotassium EDTA, and tetrasodium EDTA.

3. The composite treating agent for oily wastewater according to claim 1, wherein: The pyrophosphate is an alkali metal pyrophosphate; and the alginate is an alkali metal alginate.

4. The composite treating agent for oily wastewater according to claim 1, wherein The total number of live yeast, Bacillus subtilis and lactic acid bacteria in each 1g of the biological agent is 45 billion CFU to 49.2 billion CFU; the ratio of the number of live yeast, Bacillus subtilis and lactic acid bacteria in the biological agent is (6-12):(20-50):(1-2).

5. The composite treating agent for oily wastewater according to claim 1, wherein: The rare earth salt is rare earth sulfate and / or rare earth nitrate; the rare earth element in the rare earth salt is selected from one or any combination of cerium, neodymium and lanthanum.

6. The composite treating agent for oily wastewater according to claim 1, wherein: The alkylphenol polyoxyethylene ether is nonylphenol polyoxyethylene ether; the quaternary ammonium salt surfactant is selected from one or any combination of dodecyldimethylbenzylammonium bromide, dodecyldimethylbenzylammonium chloride, and dodecyldiethylbenzylammonium bromide.

7. The composite treating agent for oily wastewater according to claim 1, wherein: The acid solution is a phosphoric acid solution with a mass fraction of 1 to 3%; the soaking time in the acid solution is 4 to 8 minutes; the alkali solution is a sodium hydroxide solution with a mass fraction of 1 to 3%; the soaking time in the alkali solution is 2 to 4 minutes.

8. The composite treating agent for oily wastewater according to claim 1, wherein: The calcination temperature is 700-750° C.; the particle size of the attapulgite powder is 0.16 mm-0.25 mm.

9. Use of the composite treating agent for oily wastewater according to any one of claims 1 to 8 in treating oily wastewater in oilfields.

Images