High-salt extreme working condition nano-modified biodegradable demulsifier and preparation method thereof

Abstract

The present application relates to a kind of high salt extreme working condition nano modified biodegradable demulsifier, by weight parts, including the following components: cationic starch derivative biological matrix 70-75 parts, epoxy-quaternary ammonium salt bifunctional modified nano silicon dioxide 3-5 parts, amino acid type biological base amphiphilic surfactant 6-8 parts, nano cellulose whisker 2-3 parts, biological base phosphate high temperature stabilizer 2-4 parts, deionized water 10-15 parts.The present application also relates to a kind of preparation method of high salt extreme working condition nano modified biodegradable demulsifier.The present application has the following beneficial effects: solve the defects such as insufficient salt tolerance and temperature tolerance of existing demulsifier in high salt, high temperature extreme working condition, low demulsification efficiency, large dosage, poor biodegradability, etc., to meet the demulsification dehydration and environmental protection treatment needs of deep well exploitation, high salt oil and gas field, high salt refining wastewater.

Description

Technical Field

[0001] This invention relates to the fields of environmentally friendly oilfield chemicals, oily wastewater treatment, and high-salt wastewater purification, and particularly to a nano-modified biodegradable demulsifier for high-salt extreme conditions and its preparation method. Background Technology

[0002] As oil and gas resource development continues to expand into deep wells, ultra-deep wells, high-salinity oil and gas reservoirs, and deep-sea oil and gas fields, the produced water and crude oil emulsions generated during the extraction process exhibit characteristics such as high salinity, high temperature, high emulsification stability, and complex composition. This places extremely high demands on the salt resistance, temperature resistance, demulsification efficiency, and environmental friendliness of demulsifiers. Simultaneously, the oilfield and refining industries require demulsifiers not only to achieve efficient oil-water separation but also to possess good biodegradability to avoid secondary pollution of soil and water bodies.

[0003] Currently, conventional demulsifiers generally suffer from the following technical defects:

[0004] (1) Insufficient salt tolerance. Conventional demulsifiers typically have a mineralization tolerance of ≤10×10⁻⁶. 4 mg / L is prone to salting out, charge shielding, and molecular aggregation in high-salt environments, which leads to a sharp decline in demulsification performance and makes it impossible to meet the requirements for stable use in high-salt conditions.

[0005] (2) Limited temperature range. Conventional demulsifiers generally have a long-term operating temperature of no more than 120℃. Under high-temperature conditions in deep wells, they are prone to structural damage, delamination, and failure.

[0006] (3) Low demulsification efficiency and large dosage. Conventional demulsifiers typically have a demulsification rate of ≤80% and a dosage as high as 150–300 mg / L, resulting in high treatment costs and difficulty in achieving stable oil content standards in the effluent.

[0007] (4) Poor biodegradability. Traditional demulsifiers are mostly petroleum-based non-degradable polymers, and environmentally friendly products have a biodegradability rate of only ≥60% after 28 days, which easily accumulates in the environment.

[0008] In existing technologies, single bio-based demulsifiers generally suffer from shortcomings in temperature and salt resistance, while single nano-modified demulsifiers have poor biodegradability and high usage costs. Neither type of product can simultaneously achieve a synergistic improvement in high salt resistance, high temperature resistance, high degradation rate, high efficiency, and low dosage (References: CN110295126A, CN111892789A, "Research Progress on Demulsification Technology for High-Salinity Produced Water in Oilfields", Oil and Gas Field Environmental Protection, 2022). Therefore, it is necessary to develop a demulsifier that can withstand temperatures ≥30×10⁻⁶. 4 High-mineralization, stable operation at 120–180℃, biodegradable, and high-efficiency, low-consumption demulsifiers have become key technical issues that urgently need to be addressed in the field of oilfield and refining wastewater treatment. Summary of the Invention

[0009] Based on the shortcomings of the existing technology, the technical problem to be solved by the present invention is to provide a nano-modified biodegradable demulsifier for high-salt extreme working conditions and its preparation method, so as to solve the defects of existing demulsifiers such as insufficient salt and temperature resistance, low demulsification efficiency, large dosage and poor biodegradability under high-salt and high-temperature extreme working conditions, so as to meet the demulsification, dehydration and environmental protection treatment needs of deep well mining, high-salt oil and gas fields and high-salt refining wastewater.

[0010] To solve one of the above-mentioned technical problems, the present invention adopts the following technical solution:

[0011] A nano-modified biodegradable demulsifier for high-salt extreme working conditions, characterized in that, by weight, it comprises the following components: 70-75 parts of cationic starch derivative biomatrix, 3-5 parts of epoxy-quaternary ammonium salt bifunctional modified nano silica, 6-8 parts of amino acid-type bio-based amphoteric surfactant, 2-3 parts of nanocellulose whiskers, 2-4 parts of bio-based phosphate high-temperature stabilizer, and 10-15 parts of deionized water.

[0012] The functions, parameters, and dosages of each component are as follows:

[0013] (1) Cationic starch derivative biomatrix: 70–75 parts, as the core matrix, has strong salt resistance and good biodegradability, and can maintain molecular structure stability and achieve charge neutralization and demulsification in high salt systems.

[0014] (2) Epoxy-quaternary ammonium salt bifunctional modified nano silica: 3–5 parts, used to improve the salt and temperature resistance of the system, enhance the ability to destroy the oil-water interface, ensure that the demulsification rate decreases by ≤5% after the salt resistance test, and stabilize the interface structure.

[0015] (3) Amino acid-based bio-based amphoteric surfactant: 6–8 parts, used to balance the system charge, reduce interfacial tension, and improve the adaptability and demulsification speed of high-salt complex systems.

[0016] (4) Nanocellulose whiskers: 2–3 parts, used to improve the viscosity and dispersion stability of the system, prevent demulsifier loss and sedimentation, and ensure the dispersion stability of the product at room temperature for ≥6 months.

[0017] (5) Bio-based phosphate high temperature stabilizer: 2–4 parts, used to improve high temperature stability, protect the molecular structure of demulsifier, and ensure that the system does not separate after 24 hours at 180°C, which is suitable for high temperature mining conditions in deep wells.

[0018] (6) Deionized water: 10–15 parts, used as a dispersion medium to adjust the concentration and viscosity of the system, with no impurities precipitated, suitable for high-salt wastewater ratio.

[0019] The five components achieve demulsification under extreme conditions through the following synergistic mechanism: the cationic starch derivative biomatrix neutralizes the negative charge of the emulsion, weakening the electrostatic stabilization effect of the emulsion system; the modified nano-silica penetrates the oil-water interface film; the amino acid-based bio-based amphoteric surfactant reduces the interfacial tension between oil and water, accelerating the separation of the two phases; nano-cellulose whiskers regulate the viscosity of the system to prevent drug loss; and the bio-based phosphate high-temperature stabilizer protects the molecular structure of each component from degradation at 180°C. With the multi-component synergy, the overall performance is far superior to systems with a single component or lacking any one component.

[0020] Preferably, the salinity of the cationic starch derivative biomatrix is ​​≥30×10⁻⁶. 4 mg / L.

[0021] Preferably, the epoxy-quaternary ammonium salt bifunctional modified nano silica has a particle size of 10-20 nm, a specific surface area of ​​200-300 m² / g, and its surface is simultaneously covered with epoxy groups and quaternary ammonium cations.

[0022] Preferably, the surface tension of the amino acid-based bio-based amphoteric surfactant in aqueous solution is ≤28 mN / m.

[0023] Preferably, the bio-based phosphate high-temperature stabilizer ensures that the demulsifier does not separate after being placed at 180°C for 24 hours, and the temperature resistance range is 120-180°C.

[0024] Preferably, the demulsifier has a mineralization degree ≥30×10 4 Under extreme conditions of mg / L and temperature of 120-180℃, the demulsification rate is ≥98%, and the biodegradation rate after 28 days is ≥90%.

[0025] Preferably, after treating the high-salt emulsion with the demulsifier, the oil content of the dewatering water is ≤50mg / L, and the dosage is 60-100mg / L.

[0026] The present invention also provides a method for preparing a nano-modified biodegradable demulsifier for high-salt extreme conditions, comprising the following steps:

[0027] S1: Add deionized water to the reactor, heat to 40-50℃, start stirring under normal pressure, slowly add cationic starch derivative bio-matrix, and continue stirring until completely dissolved and dispersed;

[0028] S2: Under normal pressure, epoxy-quaternary ammonium salt bifunctional modified nano-silica and nano-cellulose whiskers are added sequentially and dispersed by high-speed shearing to form a uniform and stable nano-dispersion system;

[0029] S3: Add amino acid-based bio-based amphoteric surfactant and bio-based phosphate high-temperature stabilizer to the above system, and stir at a constant temperature until the system is homogeneous and transparent;

[0030] S4: Cool the above system to room temperature, filter it through a stainless steel filter to remove impurities, and obtain the target high-salt extreme condition nano-modified biodegradable demulsifier.

[0031] Preferably, in step S1, the stirring speed is 150–200 r / min, the stirring time is 60 min, and the system pH is controlled at 6.5–7.5; in step S2, the shear rate is 8000–12000 r / min, the dispersion time is 30 min, and the system temperature is 40–50℃; in step S3, the stirring speed is 200–250 r / min, the stirring is carried out at a constant temperature for 40 min, and the system pH is controlled at 6.5–7.5; and in step S4, the system is filtered through a 200-mesh stainless steel filter to remove impurities.

[0032] Discharge conditions: ambient temperature and pressure, discharge pH 6.5-7.5, no visible particles, no stratification.

[0033] Storage conditions: Temperature 5-35℃, relative humidity ≤85%, sealed and protected from light, shelf life ≥6 months.

[0034] The nano-modified biodegradable demulsifier for high-salt extreme conditions obtained by the technical solution of this invention can be applied to mineralization of 20×10⁻⁶. 4 -40×10 4 Demulsification, dehydration and purification treatment of high-salt crude oil emulsions with a concentration of mg / L, an oil content of 500-5000 mg / L, a temperature of 120-180℃, and a pH of 6.0-9.0, as well as high-salt produced water from oil fields or high-salt oily wastewater from refining.

[0035] The technical solution described in this invention has the following advantages compared with the prior art:

[0036] (1) Strong adaptability to extreme working conditions: salt tolerance ≥30×10 4 With a concentration of mg / L and a temperature resistance of 120-180℃, it can be used stably in high-salt, high-temperature deep wells / high-salt oil and gas fields, solving the problems of salt precipitation and high-temperature failure of traditional products.

[0037] (2) High efficiency in demulsification and lower dosage: The demulsification rate is ≥98%, and the dosage is only 1 / 3-1 / 2 of that of conventional products, which significantly reduces the cost of use.

[0038] (3) Green, environmentally friendly and biodegradable: ≥90% biodegradation rate in 28 days, far exceeding that of traditional environmentally friendly products, environmentally friendly and free of residual pollution.

[0039] (4) Better effluent quality: The oil content of the dewatering water is ≤50mg / L, which is far superior to the industry discharge standard. The effluent can be directly reused or discharged in compliance with the standard.

[0040] (5) Stable storage and use: Stable dispersion at room temperature for ≥6 months, no stratification at 180℃ for 24 hours, good stability, and convenient storage and transportation.

[0041] (6) The process is simple and easy to industrialize: the preparation conditions are mild and no complex reaction equipment is required, making it suitable for large-scale production. Detailed Implementation

[0042] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the protection scope of the present invention.

[0043] Example 1: A nano-modified biodegradable demulsifier for high-salt extreme conditions, comprising the following components by weight: 72 parts of cationic starch derivative biomatrix, 4 parts of epoxy-quaternary ammonium salt bifunctional modified nano silica, 7 parts of amino acid-type bio-based amphoteric surfactant, 2.5 parts of nanocellulose whiskers, 3 parts of bio-based phosphate high-temperature stabilizer, and 11.5 parts of deionized water.

[0044] The preparation method is as follows:

[0045] S1: Add deionized water to the reactor, heat to 45°C, start stirring under normal pressure at a stirring rate of 180 r / min, slowly add cationic starch derivative bio-matrix, and continue stirring for 60 min until completely dissolved and dispersed. Adjust the pH of the system to 7.0.

[0046] S2: Under normal pressure, keep the system temperature at 45℃, then add epoxy-quaternary ammonium salt bifunctional modified nano silica and nano cellulose whiskers in sequence, and perform high-speed shear dispersion at a rate of 10000r / min for 30min to form a uniform and stable nano dispersion system.

[0047] S3: Add amino acid-based bio-based amphoteric surfactant and bio-based phosphate high-temperature stabilizer to the above system, stir at a constant temperature for 40 minutes until the system is homogeneous and transparent, and maintain the pH of the system at 7.0;

[0048] S4: Cool the above system to room temperature (25°C), filter it through a 200-mesh stainless steel filter to remove impurities, and obtain the target high-salt extreme condition nano-modified biodegradable demulsifier.

[0049] Example 2: A nano-modified biodegradable demulsifier for high-salt extreme working conditions, comprising the following components by weight: 70 parts of cationic starch derivative biomatrix, 3 parts of epoxy-quaternary ammonium salt bifunctional modified nano silica, 6 parts of amino acid-type bio-based amphoteric surfactant, 2 parts of nanocellulose whiskers, 2 parts of bio-based phosphate high-temperature stabilizer, and 15 parts of deionized water.

[0050] The preparation method is as follows:

[0051] S1: Add deionized water to the reactor, heat to 45°C, start stirring under normal pressure at a stirring rate of 180 r / min, slowly add cationic starch derivative bio-matrix, and continue stirring for 60 min until completely dissolved and dispersed. Adjust the pH of the system to 7.0.

[0052] S2: Under normal pressure, keep the system temperature at 45℃, then add epoxy-quaternary ammonium salt bifunctional modified nano silica and nano cellulose whiskers in sequence, and perform high-speed shear dispersion at a rate of 10000r / min for 30min to form a uniform and stable nano dispersion system.

[0053] S3: Add amino acid-based bio-based amphoteric surfactant and bio-based phosphate high-temperature stabilizer to the above system, stir at a constant temperature for 40 minutes until the system is homogeneous and transparent, and maintain the pH of the system at 7.0;

[0054] S4: Cool the above system to room temperature, filter it through a 200-mesh stainless steel filter to remove impurities, and obtain the target high-salt extreme condition nano-modified biodegradable demulsifier.

[0055] Example 3: A nano-modified biodegradable demulsifier for high-salt extreme working conditions, comprising the following components by weight: 75 parts of cationic starch derivative biomatrix, 5 parts of epoxy-quaternary ammonium salt bifunctional modified nano silica, 8 parts of amino acid-type bio-based amphoteric surfactant, 3 parts of nanocellulose whiskers, 4 parts of bio-based phosphate high-temperature stabilizer, and 10 parts of deionized water.

[0056] The preparation method is as follows:

[0057] S1: Add deionized water to the reactor, heat to 45°C, start stirring under normal pressure at a stirring rate of 180 r / min, slowly add cationic starch derivative bio-matrix, and continue stirring for 60 min until completely dissolved and dispersed. Adjust the pH of the system to 7.0.

[0058] S2: Under normal pressure, keep the system temperature at 45℃, then add epoxy-quaternary ammonium salt bifunctional modified nano silica and nano cellulose whiskers in sequence, and perform high-speed shear dispersion at a rate of 10000r / min for 30min to form a uniform and stable nano dispersion system.

[0059] S3: Add amino acid-based bio-based amphoteric surfactant and bio-based phosphate high-temperature stabilizer to the above system, stir at a constant temperature for 40 minutes until the system is homogeneous and transparent, and maintain the pH of the system at 7.0;

[0060] S4: Cool the above system to room temperature, filter it through a 200-mesh stainless steel filter to remove impurities, and obtain the target high-salt extreme condition nano-modified biodegradable demulsifier.

[0061] Comparative Example 1: Unmodified nano-silica

[0062] Ingredients: 72 parts cationic starch derivative bio-matrix, 7 parts amino acid-based bio-based amphoteric surfactant, 2.5 parts nanocellulose whiskers, 3 parts bio-based phosphate high-temperature stabilizer, and 15.5 parts deionized water.

[0063] The preparation method is the same as in Example 1.

[0064] Comparative Example 2: Without the addition of nanocellulose whiskers

[0065] Ingredients: 72 parts cationic starch derivative bio-matrix, 4 parts epoxy-quaternary ammonium salt bifunctional modified nano silica, 7 parts amino acid type bio-based amphoteric surfactant, 3 parts bio-based phosphate high temperature stabilizer, and 14 parts deionized water.

[0066] The preparation method is the same as in Example 1.

[0067] Comparative Example 3: High-temperature stabilizer without bio-based phosphate

[0068] Ingredients: 72 parts cationic starch derivative bio-matrix, 4 parts epoxy-quaternary ammonium salt bifunctional modified nano silica, 7 parts amino acid type bio-based amphoteric surfactant, 2.5 parts nanocellulose whiskers, and 14.5 parts deionized water.

[0069] The preparation method is the same as in Example 1.

[0070] Comparative Example 4: Without the addition of amino acid-based bio-based surfactants

[0071] Ingredients: 72 parts cationic starch derivative bio-matrix, 4 parts epoxy-quaternary ammonium salt bifunctional modified nano silica, 2.5 parts nano cellulose whiskers, 3 parts bio-based phosphate high-temperature stabilizer, and 14.5 parts deionized water.

[0072] Comparative Example 5: Commercially available conventional environmentally friendly demulsifiers

[0073] Performance testing: To further illustrate the effect of the high-salt extreme-condition nano-modified biodegradable demulsifier prepared in the above embodiments, testing was performed in accordance with current industry standards.

[0074] (1) Demulsification rate: Refer to SY / T5281-2016 "Test method for performance of crude oil demulsifier (bottle test method)"; take 100mL of high salt emulsion, add demulsifier and shake well, and let stand at constant temperature for 15min; Demulsification rate (%) = (amount of water removed / theoretical total water) × 100%.

[0075] (2) 28-day biodegradation rate: Refer to GB / T15818-2018 "Test method for biodegradability of surfactants"; shake culture method, activated sludge inoculation, 28-day CODCr removal rate = biodegradation rate.

[0076] (3) Salt tolerance: Prepare a series of simulated saline solutions (NaCl+CaCl2+MgCl2), dilute with demulsifier 100 times, and the highest salinity that shows no turbidity / precipitation / layering after 24 hours at room temperature is the salt tolerance.

[0077] (4) Temperature stability: The sample is placed in a high-temperature reactor and kept at 120 / 150 / 180℃ for 24 hours. It is considered qualified if there is no stratification or precipitation after cooling.

[0078] (5) Oil content in dewatered water: Refer to GB / T16489-1996 Infrared spectrophotometry.

[0079] (6) Interfacial tension: Interfacial tension between 0.1% demulsifier aqueous solution and crude oil was tested at 25℃ using an interfacial tension meter.

[0080] (7) Dosage: Set different dosage gradients and determine the optimal dosage range based on the criteria of demulsification rate ≥98% and oil content in effluent ≤50mg / L.

[0081] Stability tests were conducted on Examples 1-3 and Comparative Examples 1-5, and the specific test data are as follows:

[0082]

[0083] In summary, the high-salt extreme-condition nano-modified biodegradable demulsifiers prepared in Examples 1-3 exhibit significantly better performance indicators than any comparative example lacking a single component, demonstrating a clear synergistic effect among the five components. This synergistic effect is achieved through the combined action of the five components: cationic starch derivative biomatrix, epoxy-quaternary ammonium salt bifunctional modified nano-silica, amino acid-based bio-based amphoteric surfactant, nano-cellulose whiskers, and bio-based phosphate high-temperature stabilizer.

[0084] To further verify its performance, the demulsifier of this invention was added at a dosage of 60–100 mg / L to a mineralization of 20 × 10⁻⁶. 4 –40×10 4For high-salt crude oil emulsions with a concentration of mg / L, an oil content of 500–5000 mg / L, a temperature of 120–180℃, and a pH of 6.0–9.0, as well as high-salt produced water from oil fields or high-salt oily wastewater from refining, rapid stirring and uniform mixing followed by standing for 5–15 minutes will achieve clear stratification of the oil and water phases, completing demulsification and dehydration. The effluent can then be directly discharged in compliance with standards or reused.

[0085] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

[0086] Any aspects of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A nano-modified biodegradable demulsifier for high-salt extreme working conditions, characterized in that, By weight, it includes the following components: 70-75 parts of cationic starch derivative biomatrix, 3-5 parts of epoxy-quaternary ammonium salt bifunctional modified nano silica, 6-8 parts of amino acid-type bio-based amphoteric surfactant, 2-3 parts of nanocellulose whiskers, 2-4 parts of bio-based phosphate high-temperature stabilizer, and 10-15 parts of deionized water.

2. The nano-modified biodegradable demulsifier for high-salt extreme conditions according to claim 1, characterized in that, The cationic starch derivative biomatrix has a salt tolerance ≥30×10⁻⁶. 4 mg / L.

3. The nano-modified biodegradable demulsifier for high-salt extreme conditions according to claim 1, characterized in that, The epoxy-quaternary ammonium salt bifunctional modified nano-silica has a particle size of 10-20 nm, a specific surface area of ​​200-300 m² / g, and its surface is simultaneously covered with epoxy groups and quaternary ammonium cations.

4. The nano-modified biodegradable demulsifier for high-salt extreme conditions according to claim 1, characterized in that, The surface tension of the amino acid-based bio-based amphoteric surfactant in aqueous solution is ≤28 mN / m.

5. The nano-modified biodegradable demulsifier for high-salt extreme conditions according to claim 1, characterized in that, The bio-based phosphate high-temperature stabilizer allows the demulsifier to remain without stratification or precipitation after being placed at 180°C for 24 hours, with a temperature range of 120-180°C.

6. The nano-modified biodegradable demulsifier for high-salt extreme conditions according to claim 1, characterized in that, The demulsifier has a mineralization degree ≥30×10 4 Under extreme conditions of mg / L and temperature of 120-180℃, the demulsification rate is ≥98%, and the biodegradation rate after 28 days is ≥90%.

7. The nano-modified biodegradable demulsifier for high-salt extreme conditions according to claim 1, characterized in that, After the demulsifier treats the high-salt emulsion, the oil content in the dewatering water is ≤50mg / L, and the dosage is 60-100mg / L.

8. A method for preparing a nano-modified biodegradable demulsifier for high-salt extreme conditions according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Add deionized water to the reactor, heat to 40-50℃, start stirring under normal pressure, slowly add cationic starch derivative bio-matrix, and continue stirring until completely dissolved and dispersed; S2: Under normal pressure, epoxy-quaternary ammonium salt bifunctional modified nano-silica and nano-cellulose whiskers are added sequentially and dispersed by high-speed shearing to form a uniform and stable nano-dispersion system; S3: Add amino acid-based bio-based amphoteric surfactant and bio-based phosphate high-temperature stabilizer to the above system, and stir at a constant temperature until the system is homogeneous and transparent; S4: Cool the above system to room temperature, filter it through a stainless steel filter to remove impurities, and obtain the target high-salt extreme condition nano-modified biodegradable demulsifier.

9. The preparation method of the nano-modified biodegradable demulsifier for high-salt extreme conditions as described in claim 8, characterized in that, In step S1, the stirring speed is 150–200 r / min, the stirring time is 60 min, and the system pH is controlled at 6.5–7.

5. In step S2, the shear rate is 8000–12000 r / min, the dispersion time is 30 min, and the system temperature is 40–50℃. In step S3, the stirring speed is 200–250 r / min, the stirring is carried out at a constant temperature for 40 min, and the system pH is controlled at 6.5–7.

5. In step S4, the system is filtered through a 200-mesh stainless steel filter to remove impurities.

10. The application of the nano-modified biodegradable demulsifier for high-salt extreme conditions according to any one of claims 1-7 in the treatment of oily wastewater, characterized in that, Applicable to mineralization of 20×10 4 -40×10 4 Demulsification, dehydration and purification treatment of high-salt crude oil emulsions with a concentration of mg / L, an oil content of 500-5000 mg / L, a temperature of 120-180℃, and a pH of 6.0-9.0, as well as high-salt produced water from oil fields or high-salt oily wastewater from refining.

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