Hydrophobic deep eutectic solvent and preparation method and application thereof

Abstract

A kind of hydrophobic eutectic solvent and its preparation method and application, fatty acid and methyltrioctylammonium chloride are placed in 80 ℃ water bath condition under stirring heating, until transparent liquid is obtained, i.e.eutectic solvent of hydrophobic fatty acid-methyltrioctylammonium chloride.The low-toxicity, stable hydrophobic eutectic solvent obtained by simple preparation process, using its excellent conductivity and extraction characteristics to extract organic matter and heavy metals in oil sludge, and under the action of external electric field, heavy metal ions move to cathode, and through reduction reaction, it is deposited on cathode, to achieve the purpose of separating organic matter and heavy metals in situ.Secondly, the more corrosion-resistant stainless steel material is selected for cathode, which is more conducive to the elution of deposited metal, and enhances the reusability of cathode.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical environmental protection technology, specifically relating to a hydrophobic eutectic solvent, its preparation method, and its application. Background Technology

[0002] With rapid societal development, the demand for and extraction rate of oil have increased year by year. However, due to limitations in extraction technology and production processes, a large amount of oily sludge has been generated. This substance contains polycyclic aromatic hydrocarbons, surfactants, and heavy metals, and is therefore listed as a national hazardous waste. Consequently, technologies for reducing and harmlessly treating oily sludge have been widely explored and applied.

[0003] Current technologies for the resource recovery of oily sludge mainly include solvent extraction, thermochemical methods, freeze / thaw processes, and centrifugal separation. These methods can effectively reduce the toxicity of oily sludge and recover products, but problems such as low product yield, complex composition, and secondary pollution caused by the technology still exist. Developing green coupled processes is an important way to improve the efficiency and quality of crude oil recovery. Therefore, while ensuring the extraction rate, separating oil and heavy metals from the product is an effective approach to improve quality. Electrochemical treatment is a relatively new method for treating heavy metal-contaminated soil. However, due to the stable properties and poor conductivity of oily sludge, the applicability of electrochemical treatment alone is limited. The introduction of electrolytes can improve this situation; however, traditional acidic or alkaline electrolytes are added to the system as new sources of pollution, increasing the difficulty of subsequent treatment. Eutectic solvents are green and non-toxic ionic liquids with good extraction capabilities and low volatility, making them suitable for cleaning oily sludge. However, this reagent has low selectivity for organic components and heavy metals in the sludge, which is not conducive to obtaining pure oil products. The excellent conductivity and good electrochemical window of eutectic solvents make them promising candidates for electrochemical applications. Reducing their hydrophilicity can further enhance their usability and facilitate subsequent separation. Summary of the Invention

[0004] Technical Problem Solved: This invention primarily addresses the shortcomings of existing oil sludge resource utilization technologies by proposing a hydrophobic eutectic solvent, its preparation method, and its applications. This invention utilizes a simple preparation process to obtain a low-toxicity, stable, hydrophobic eutectic solvent. Its excellent electrical conductivity and extraction properties are used to extract organic matter and heavy metals from oil sludge. Under the influence of an external electric field, heavy metal ions migrate towards the cathode and are deposited on the cathode through a reduction reaction, achieving in-situ separation of organic matter and heavy metals. Furthermore, the cathode is made of more corrosion-resistant stainless steel, which is more conducive to the elution of deposited metals and enhances the reusability of the cathode.

[0005] Technical solution: A method for preparing a hydrophobic eutectic solvent, comprising the following steps: placing fatty acids and methyltrioctyl ammonium chloride in a water bath at 80°C and stirring and heating, wherein the molar ratio of fatty acids to methyltrioctyl ammonium chloride is (1-6):1, until a transparent liquid is obtained, thereby obtaining a hydrophobic fatty acid-methyltrioctyl ammonium chloride eutectic solvent (HDES).

[0006] The fatty acids mentioned above are oleic acid, caprylic acid, capric acid, or lauric acid.

[0007] The molar ratio of the above fatty acids to methyltrioctylammonium chloride is 2:1.

[0008] The hydrophobic eutectic solvent obtained by the above method.

[0009] Application of the above-mentioned hydrophobic eutectic solvent in upgrading oily sludge.

[0010] The application steps are as follows: add the hydrophobic eutectic solvent to the oily sludge, adjust the pH to acidic, stir evenly, and then transfer the mixed solution to the electrochemical system; select graphite as the anode and stainless steel as the cathode, and use an external electric field to electrolyze the mixed solution; after electrolysis, remove the two electrodes, place them in ethanol solution for ultrasonic washing and drying, and obtain the metal deposition layer in the cathode drying solution; initially separate the supernatant and the lower layer of sludge from the layered mixture, and then centrifuge the supernatant and sludge to separate the three phases of water, extracted hydrophobic eutectic solvent and sludge.

[0011] The mass ratio of the above-mentioned hydrophobic eutectic solvent to the oily sludge mixed solution is (3-9):1. The acid used to adjust the acidity of the mixed solution is a 2 mol / L dilute hydrochloric acid solution, and the pH range is 3-6.

[0012] The applied electric field voltage is 1 to 3V, the distance between the two electrodes is 1 to 4cm, the electrolysis temperature is 18℃ to 65℃, and the electrolysis time is 6 to 18h.

[0013] The above washing and drying temperature range for both electrodes is 40-80℃, the centrifugation rate is 3000-4000 r / min, and the centrifugation time is 10-30 min.

[0014] Beneficial effects: 1) Utilizing electrochemical principles and a continuous deposition process, heavy metals in oil sludge are continuously separated, ultimately achieving the goal of separating, purifying, and extracting organic matter; 2) Using fatty acids as hydrogen bond donors promotes the leaching of heavy metals from oil sludge, and the hydrophobicity of the eutectic solvent is more conducive to separation from the aqueous phase; 3) The green and biodegradable eutectic solvent possesses good conductivity, a relatively wide electrochemical window, and recyclability and reusability, which are important advantages as an electrolyte; 4) In addition to controlling the temperature of the electrochemical system, heavy metal salts in the oil sludge can act as hydrogen bond acceptors, reducing the viscosity of the eutectic solvent and thus enhancing its conductivity. The reduction of heavy metals restores its hydrophobic properties; 5) The separation of heavy metals and organic matter facilitates the release of some bound water in the oil sludge, and the water content in the oil sludge can be reduced through electrolysis. Detailed Implementation

[0015] Oily sludge from a petrochemical refinery was selected as the target treatment sample (moisture content 13.5%, oil content 58%).

[0016] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited thereto.

[0017] Example 1

[0018] A method for upgrading oily sludge using a hydrophobic eutectic solvent and electrochemical methods, comprising the following specific steps:

[0019] (1) Mix octanoic acid and methyltrioctyl ammonium chloride at a molar ratio of 1:1 and heat in an 80°C water bath for 60 minutes until a transparent liquid is obtained, namely hydrophobic octanoic acid-methyltrioctyl ammonium chloride eutectic solvent (HDES).

[0020] (2) Weigh the pre-prepared HDES transparent solution at a mass ratio of 3:1 and add it to 25g of sludge. Add hydrochloric acid solution (2mol / L) to adjust the pH of the mixed solution to 4. Stir well and then add it to the electrochemical system.

[0021] (3) An electrochemical system was constructed using graphite as the anode and stainless steel as the cathode, with a distance of 2.5 cm between the two electrodes, and an external voltage of 1.5 V was applied. The mixed solution obtained in step (2) was heated and the temperature was controlled at 55 °C for electrolysis for 12 h.

[0022] After electrolysis, the external power supply was disconnected, and the anode graphite material and cathode stainless steel material were removed and ultrasonically washed in ethanol solution for 5 minutes. Then they were dried at 60°C for later use. The removal rate of zinc in the sludge was 72%, the removal rate of copper was 62%, the removal rate of lead was 55%, the removal rate of nickel was 58%, and the removal rate of cobalt was 58%.

[0023] The supernatant and lower sediment were initially separated from the stratified mixture. The supernatant and sediment were then centrifuged for 30 minutes at a rate of 4000 r / min to separate the three phases (water, extracted HDES, and sediment). The remaining sludge was calculated to have a water content of 6.8% and an oil content of 11%.

[0024] Example 2

[0025] A method for upgrading oily sludge using a hydrophobic eutectic solvent and electrochemical methods, comprising the following specific steps:

[0026] (1) Mix octanoic acid and methyltrioctyl ammonium chloride at a molar ratio of 1:1 and heat in an 80°C water bath for 60 minutes until a transparent liquid is obtained, namely hydrophobic octanoic acid-methyltrioctyl ammonium chloride eutectic solvent (HDES).

[0027] (2) Weigh the pre-prepared HDES transparent solution at a mass ratio of 6:1 and add it to 25g of sludge. Add hydrochloric acid solution (2mol / L) to adjust the pH of the mixed solution to 4. Stir well and then add it to the electrochemical system.

[0028] (3) An electrochemical system was constructed using graphite as the anode and stainless steel as the cathode, with a distance of 3.5 cm between the two electrodes, and an external voltage of 2.5 V was applied. The mixed solution obtained in step (2) was heated and the temperature was controlled at 55 °C for electrolysis for 12 h.

[0029] After electrolysis, the external power supply was disconnected, and the anode graphite material and cathode stainless steel material were removed and ultrasonically washed in ethanol solution for 5 minutes. Then they were dried at 60°C for later use. The removal rate of zinc in the sludge was 75%, the removal rate of copper was 66%, the removal rate of lead was 71%, the removal rate of nickel was 74%, and the removal rate of cobalt was 60%.

[0030] The supernatant and lower sediment were initially separated from the stratified mixture. The supernatant and sediment were then centrifuged for 30 minutes at a rate of 4000 r / min to separate the three phases (water, extracted HDES, and sediment). The remaining sludge was calculated to have a water content of 5.2% and an oil content of 5.8%.

[0031] Example 3

[0032] A method for upgrading oily sludge using a hydrophobic eutectic solvent and electrochemical methods, comprising the following specific steps:

[0033] (1) Mix octanoic acid and methyltrioctyl ammonium chloride at a molar ratio of 2:1, and heat in an 80°C water bath for 60 minutes until a transparent liquid is obtained, namely hydrophobic octanoic acid-methyltrioctyl ammonium chloride eutectic solvent (HDES).

[0034] (2) Weigh the pre-prepared HDES transparent solution at a mass ratio of 6:1 and add it to 25g of sludge. Add hydrochloric acid solution (2mol / L) to adjust the pH of the mixed solution to 4. Stir well and then add it to the electrochemical system.

[0035] (3) An electrochemical system was constructed using graphite as the anode and stainless steel as the cathode, with a distance of 2.5 cm between the two electrodes, and an external voltage of 2.5 V was applied. The mixed solution obtained in step (2) was heated and the temperature was controlled at 55 °C for electrolysis for 12 h.

[0036] After electrolysis, the external power supply was disconnected, and the anode graphite material and cathode stainless steel material were removed and ultrasonically washed in ethanol solution for 5 minutes. Then they were dried at 60°C for later use. The removal rate of zinc in the sludge was 92%, the removal rate of copper was 85%, the removal rate of lead was 80%, the removal rate of nickel was 82%, and the removal rate of cobalt was 81%.

[0037] The supernatant and lower sediment were initially separated from the stratified mixture. The supernatant and sediment were then centrifuged for 30 minutes at a rate of 4000 r / min to separate the three phases (water, extracted HDES, and sediment). The remaining sludge was calculated to have a water content of 4.2% and an oil content of 5.5%.

[0038] Example 4

[0039] A method for upgrading oily sludge using a hydrophobic eutectic solvent and electrochemical methods, comprising the following specific steps:

[0040] (1) Mix octanoic acid and methyltrioctyl ammonium chloride at a molar ratio of 2:1, and heat in an 80°C water bath for 60 minutes until a transparent liquid is obtained, namely hydrophobic octanoic acid-methyltrioctyl ammonium chloride eutectic solvent (HDES).

[0041] (2) Weigh the pre-prepared HDES transparent solution at a mass ratio of 6:1 and add it to 25g of sludge. Add hydrochloric acid solution (2mol / L) to adjust the pH of the mixed solution to 4. Stir well and then add it to the electrochemical system.

[0042] (3) An electrochemical system was constructed using graphite as the anode and stainless steel as the cathode, with a distance of 2.5 cm between the two electrodes, and an external voltage of 3.5 V was applied. The mixed solution obtained in step (2) was heated and the temperature was controlled at 25 °C for electrolysis for 12 h.

[0043] After electrolysis, the external power supply was disconnected, and the anode graphite material and cathode stainless steel material were removed and ultrasonically washed in ethanol solution for 5 minutes. Then they were dried at 60°C for later use. The removal rate of zinc in the sludge was 63%, the removal rate of copper was 55%, the removal rate of lead was 71%, the removal rate of nickel was 63%, and the removal rate of cobalt was 58%.

[0044] The supernatant and lower sediment were initially separated from the stratified mixture. The supernatant and sediment were then centrifuged for 30 minutes at a rate of 4000 r / min to separate the three phases (water, extracted HDES, and sediment). The remaining sludge was calculated to have a water content of 5.8% and an oil content of 6.2%.

[0045] Through the tests conducted in the above examples, it was found that the separation and deposition of heavy metals in HDES and electrochemical systems exhibit selectivity, which is significantly affected by the type, viscosity, and electrochemical window of HDES. When the amount of HDES is low, the metal ion conductivity is poor, and the oil phase extraction capacity decreases. Therefore, appropriately increasing the amount of HDES can improve the separation efficiency of heavy metals from the oil phase in oil sludge. Secondly, maintaining a certain temperature during the electrodeposition process and reducing the system viscosity can enhance the electrotransmission capacity of HDES. In addition, the external voltage and electrode spacing are also important factors affecting the removal efficiency of heavy metals. When the voltage exceeds the tolerance range of HDES, the solvent system becomes unstable, which weakens the metal reduction and water electrolysis processes.

[0046] Table 1. Heavy metal content in original oily sludge and treated sludge.

[0047]

[0048] Test sample: dried sludge

[0049] Table 2. HDES properties and viscosity changes after heating the mixture.

[0050]

Claims

1. The application of a hydrophobic eutectic solvent in upgrading oily sludge, characterized in that, The steps are as follows: add the hydrophobic eutectic solvent hydrophobic fatty acid-methyltrioctylammonium chloride to the oily sludge, adjust the pH to acidic and stir evenly, then transfer the mixed solution to the electrochemical system; select graphite as the anode and stainless steel as the cathode, and use an external electric field to electrolyze the mixed solution; After electrolysis, the two electrodes were removed, and the electrodes were ultrasonically washed and dried in ethanol solution. The metal deposition layer was then obtained in the cathode drying solution. The supernatant and the lower layer of sediment were initially separated from the layered mixture. Then, the supernatant and sediment were centrifuged to separate the three phases: water, the hydrophobic eutectic solvent after extraction, and sediment.

2. The application according to claim 1, characterized in that, The mass ratio of the hydrophobic eutectic solvent to the oily sludge mixture is (3-9):

1. The acid used to adjust the acidity of the mixture is a 2 mol / L dilute hydrochloric acid solution, and the pH range is 3-6.

3. The application according to claim 1, characterized in that, The applied electric field voltage in the electrolysis step is 1 to 3V, the distance between the two electrodes is 1 to 4cm, the electrolysis temperature is 18℃ to 65℃, and the electrolysis time is 6 to 18h.

4. The application according to claim 1, characterized in that, In the ultrasonic washing and drying process, the drying temperature range of the two electrodes after washing is 40-80℃, the centrifugation rate in the centrifugation step is 3000-4000 r / min, and the centrifugation time is 10-30 min.

5. The application according to claim 1, characterized in that, The hydrophobic eutectic solvent is prepared by the following method: fatty acid and methyltrioctyl ammonium chloride are placed in a water bath at 80°C and stirred and heated, wherein the molar ratio of fatty acid to methyltrioctyl ammonium chloride is (1-6):1, until a transparent liquid is obtained, which is the hydrophobic fatty acid-methyltrioctyl ammonium chloride eutectic solvent (HDES).

6. The application according to claim 5, characterized in that, The fatty acid is oleic acid, caprylic acid, capric acid, or lauric acid.

7. The application according to claim 5, characterized in that, The molar ratio of the fatty acid to methyltrioctylammonium chloride is 2:1.

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