Quaternary ammonium salt ionic liquid, preparation method and method for extracting phenol in phenol-containing wastewater

Abstract

The invention discloses quaternary ammonium salt ionic liquid, a preparation method and a method for extracting phenol in phenolic wastewater. The quaternary ammonium salt ionic liquid is L-carnitine-ethylene glycol ionic liquid. The method comprises the following steps: stirring an extracting agent and quantitative and fixed-concentration phenol model oil at room temperature, and standing to obtain layered two phases, so as to realize effective separation of phenol-containing wastewater and phenol-containing wastewater; according to the method, L-carnitine is taken as a raw material, a lower-layer ionic liquid phase is separated in a liquid separation mode, ethyl acetate is used for back extraction, standing and layering are performed after stirring, an upper-layer oil phase is rectified, and when the molar ratio of L-carnitine to ethylene glycol is 1: 8, the extraction efficiency of phenol reaches up to 99.8% or above; and after 4-10 times of cyclic extraction, the extraction agent still shows very strong extraction and separation capability. The quaternary ammonium salt ionic liquid used in the method is high in separation efficiency, high in cyclic extraction capacity, environmentally friendly and capable of being repeatedly used, and the recovery rate can reach 90% or above.

Description

Technical Field

[0001] The invention belongs to the field of separation in the phenol-containing wastewater industry, and specifically belongs to a quaternary ammonium salt ionic liquid, a preparation method and a method for extracting phenol in phenol-containing wastewater. Background Art

[0002] Phenolic wastewater mainly comes from coking, oil refining, petrochemical and other industries. It contains volatile phenol and non-volatile phenol, as well as pollutants such as oil and sulfide. The unsaturated bonds on the phenol ring are easy to oxidize, which is also an important factor affecting the indicators of phenolic wastewater. Therefore, extracting phenol from phenolic wastewater is not only important for environmental improvement and water quality improvement.

[0003] Phenolic wastewater is highly toxic and has complex components, making it difficult to treat. Conventional treatment methods such as physical, chemical and biological methods can remove some pollutants, but they cannot meet the requirements of green environmental protection. For example, using a large amount of acid and alkali to absorb phenols from model oil through chemical conversion has considerable efficiency, but it will produce a large amount of wastewater containing phenolic compounds, which will seriously corrode equipment and have high toxicity and mutagenic effects on humans, animals and aquatic organisms. Therefore, their concentration in sewage is strictly limited by many restrictions or regulations. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a quaternary ammonium salt ionic liquid, a preparation method and a method for extracting phenol in phenol-containing wastewater. The present invention uses L-carnitine-ethylene glycol ionic liquid as an extractant, and realizes the separation of phenol in phenol-containing wastewater by forming hydrogen bonds between the strongly polar atoms contained in the anions and cations and phenol.

[0005] The objectives of the present invention are achieved through the following technical solutions.

[0006] A quaternary ammonium salt ionic liquid, wherein the quaternary ammonium salt ionic liquid is L-carnitine-ethylene glycol ionic liquid, which is non-volatile, easily soluble in organic solvents, has a temperature operating range of 10-100° C., and has the following structural formula:

[0007]

[0008] The method for preparing a quaternary ammonium salt ionic liquid comprises the following steps:

[0009] Step (1) Grinding of L-carnitine: Grind a certain amount of L-carnitine solid into powder, dry it in a vacuum drying oven, and then place it on tin foil for later use;

[0010] Step (2) Synthesis of L-carnitine-ethylene glycol ionic liquid: Take an appropriate amount of L-carnitine solid powder and add it into ethylene glycol solution to completely dissolve it to obtain the target product L-carnitine-ethylene glycol ionic liquid.

[0011] In step (2) of the preparation method, the molar ratio of L-carnitine to ethylene glycol in the ionic liquid is 1:1-1:16.

[0012] The method for using a quaternary ammonium salt ionic liquid to extract phenol from phenol-containing wastewater comprises the following steps:

[0013] Step (1) using a quaternary ammonium salt ionic liquid as an extractant to carry out an extraction reaction with a phenol model oil simulating phenol-containing wastewater, and then standing to perform phase separation, thereby finally obtaining an upper oil phase from which phenol is removed and a lower ionic liquid phase containing phenol;

[0014] Step (3) adding stripping agent ethyl acetate to the lower layer of the ionic liquid phase containing phenol, stirring and standing to separate the layers, the upper layer is the stripping agent phase containing phenol, and the lower layer is a quaternary ammonium salt ionic liquid extractant, and the quaternary ammonium salt ionic liquid can be regenerated and used;

[0015] Step (4) adds phenol model oil in the same mass ratio as that in step (1) to the quaternary ammonium salt ionic liquid extractant, performs cyclic extraction, and the number of cycles is 4-10 times, and the phenol-containing stripping agent phase is distilled to obtain product phenol and stripping agent, and the stripping agent can be reused.

[0016] In step (1) of the method for extracting phenol from phenol-containing wastewater, the mass ratio of the quaternary ammonium salt ionic liquid to the phenol model oil is 1:1-1:6.

[0017] In step (1) of the method for extracting phenol from phenol-containing wastewater, the extraction reaction temperature is 25-50°C.

[0018] In the method for extracting phenol from phenol-containing wastewater in step (1), the extraction reaction time is 10-110 minutes.

[0019] The extraction rate of phenol in step (1) of the method for extracting phenol from phenol-containing wastewater is 89.94%-99.9%;

[0020] The extraction efficiency E% of phenol was calculated according to the following formula:

[0021] E%=(C0V0-C t V t ) / C0V0×100%, where

[0022] C0 represents the initial concentration of phenol in the phenol model oil, g / L

[0023] V0 is the initial volume of phenol model oil, mL

[0024] C t Represents the concentration of residual phenol in the toluene phase after extraction, g / L

[0025] V t The volume of phenol remaining in the toluene phase after extraction, mL.

[0026] The method for extracting phenol from phenol-containing wastewater and the preparation method of phenol model oil are as follows: phenol-containing wastewater is mainly composed of neutral hydrocarbons, namely aromatic hydrocarbons and aliphatic hydrocarbons, acidic phenols, and a small amount of free water; in order to reduce the difficulty of analysis, phenol and toluene are used to simulate the phenol model oil, wherein phenol represents acidic phenols, toluene represents neutral hydrocarbons, and the concentration of phenol in the phenol model oil is 50-200g / L.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The quaternary ammonium salt ionic liquid extractant used in the present invention has low gas pressure and no volatility as raw materials of the alkaloid L-carnitine and ethylene glycol, so it is environmentally friendly; the quaternary ammonium salt ionic liquid has a wide operating temperature range of 10-100° C., so it can remain stable under various temperature conditions. It shows good stability to both air and water, is not easy to decompose or deteriorate, has stable properties, so it has thermal stability and chemical stability; the quaternary ammonium salt ionic liquid is easy to separate from other substances, and can be recycled and reused through simple treatment, which reduces production costs and reduces waste generation, so it is recyclable.

[0029] The preparation of L-carnitine-ethylene glycol ionic liquid is obtained by direct synthesis, which is simple and efficient to operate; it has low temperature requirements and does not require high temperature conditions; it has low requirements for equipment and ordinary equipment can meet the needs; L-carnitine-ethylene glycol ionic liquid has almost no volatility and will not cause environmental pollution, which is in line with the concept of green environmental protection.

[0030] L-carnitine-ethylene glycol ionic liquid has good solubility for phenolic substances and can efficiently extract phenolic substances from phenolic wastewater; it can be recycled, reducing treatment costs and reducing waste generation; it has low requirements for extraction temperature and extraction pressure, is easy to operate, and reduces energy consumption and equipment costs; it is applicable to phenolic wastewater of different concentrations, and can effectively extract both high-concentration and low-concentration wastewater; it can be used in conjunction with other technologies to give full play to their respective advantages and improve the treatment effect of phenolic wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is the NMR spectrum of L-carnitine-ethylene glycol ionic liquid.

[0032] Figure 2It is the FTIR spectrum of L-carnitine-ethylene glycol ionic liquid. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with specific embodiments, a quaternary ammonium salt ionic liquid, a preparation method and a method for extracting phenol from phenol-containing wastewater, but is not limited to the following embodiments.

[0034] Compared with the traditional acid-base method, solvent extraction separation, especially liquid-liquid extraction, has the advantages of high productivity, high recovery and low product cost. This method is also widely used in the wastewater industry.

[0035] Ionic liquids have a wide liquid range and have broad application prospects in the extraction and separation of pollutants. Ionic liquids have selective solubility for inorganic and organic materials, are immiscible with some organic solvents, and can provide a non-aqueous two-phase system with adjustable polarity, making them widely used in extraction. Ionic liquids refer to organic salts that are liquid at room temperature. This liquid molten salt is different from other ionic compounds. It has a low vapor pressure and relatively stable chemical properties. Ionic liquids themselves have good phase-forming ability and can achieve good separation effects at a small dosage. Quaternary ammonium salt ionic liquids have a strong capture ability for phenol and can form hydrogen bonds with phenol, providing a way to extract phenol from organic solvents.

[0036] Phenol-containing wastewater is mainly composed of neutral hydrocarbons (aromatic hydrocarbons, aliphatic hydrocarbons), acidic phenolic substances, and a small amount of free water. In order to reduce the difficulty of analysis, in the present invention, phenol and toluene are used to simulate phenol model oil, wherein phenol represents acidic phenolic substances and toluene represents neutral hydrocarbon substances.

[0037] Example 1 Preparation method of quaternary ammonium salt ionic liquid

[0038] Weigh 39.4 g of L-carnitine solid and grind it into powder in a mortar. At the same time, weigh 99.4 g of ethylene glycol solvent in a beaker, and then slowly add the ground powdered L-carnitine into the ethylene glycol solution to completely dissolve it to obtain the target product, a quaternary ammonium salt ionic liquid.

[0039] Embodiment 2 The influence of different molar ratios of a quaternary ammonium salt ionic liquid on the phenol extraction efficiency The quaternary ammonium salt ionic liquid is L-carnitine-ethylene glycol ionic liquid, and L-carnitine and ethylene glycol in the quaternary ammonium salt ionic liquid are at different molar ratios such as 1:1, 1:8, and 1:16. When the mass ratio of the quaternary ammonium salt ionic liquid to the phenol model oil is 1:2, and the reaction temperature is 25°C, after stirring on a magnetic stirrer for 70min, the phenol concentration in the upper oil phase is analyzed by gas chromatograph, and the phenol extraction rates calculated are 89.94%, 92.40%, and 90.08%, respectively, and the optimal molar ratio of L-carnitine and ethylene glycol in the quaternary ammonium salt ionic liquid is 1:8.

[0040] Example 3 A method for extracting phenol from phenol-containing wastewater using a quaternary ammonium salt ionic liquid

[0041] At the beginning, the quaternary ammonium salt ionic liquid and the phenol model oil are reacted and then allowed to stand for phase separation, and finally an upper oil phase from which phenol is removed and a lower ionic liquid phase containing phenol are obtained, wherein the extraction rate of phenol can reach 89.94%-99.9%; ethyl acetate as a stripping agent is added to the lower ionic liquid phase containing phenol, and the mixture is stirred and allowed to stand for separation, wherein the upper layer is the stripping agent phase containing phenol, and the lower layer is the quaternary ammonium salt ionic liquid extractant, and the quaternary ammonium salt ionic liquid can be recycled; the phenol model oil in the same mass ratio as that at the beginning is added to the quaternary ammonium salt ionic liquid extractant, and cyclic extraction is performed, wherein the number of cycles is 4-10 times, and the stripping agent phase containing phenol is rectified to obtain product phenol and the stripping agent, and the stripping agent can be reused.

[0042] Example 4 Effect of different mass ratios of a quaternary ammonium salt ionic liquid to phenol model oil on phenol extraction efficiency

[0043] The quaternary ammonium salt ionic liquid is L-carnitine-ethylene glycol ionic liquid, and the quaternary ammonium salt ionic liquid and the phenol model oil are at different mass ratios of 1:1, 1:2, 1:6, etc. When the molar ratio of the quaternary ammonium salt ionic liquid is 1:8 and the reaction temperature is 25°C, after stirring on a magnetic stirrer for 70 minutes, the phenol concentration in the upper oil phase is determined by a gas chromatograph, and the phenol extraction rates are calculated to be 95.92%, 99.99%, and 99.31%, respectively, and the optimal mass ratio of the quaternary ammonium salt ionic liquid to the phenol model oil is 1:2.

[0044] Example 5 Effect of different reaction temperatures of a quaternary ammonium salt ionic liquid and phenol model oil on phenol extraction efficiency

[0045] The quaternary ammonium salt ionic liquid is L-carnitine-ethylene glycol ionic liquid, and the quaternary ammonium salt ionic liquid and the phenol model oil are at different reaction temperatures such as 25°C, 35°C, and 50°C. When the molar ratio of the quaternary ammonium salt ionic liquid is 1:8, and the mass ratio of the quaternary ammonium salt ionic liquid to the phenol model oil is 1:2, after stirring on a magnetic stirrer for 70 minutes, the phenol concentration in the upper oil phase is measured by gas chromatography, and the phenol extraction rates are calculated to be 98.26%, 97.48%, and 97.75%, respectively, and the optimal reaction temperature of the quaternary ammonium salt ionic liquid and the phenol model oil is 25°C.

[0046] Example 6 Effect of different reaction times of a quaternary ammonium salt ionic liquid and phenol model oil on phenol extraction efficiency

[0047] The quaternary ammonium salt ionic liquid is L-carnitine-ethylene glycol ionic liquid, and the quaternary ammonium salt ionic liquid and the phenol model oil are at different reaction times of 30min, 70min, 110min, etc. When the mass ratio of the quaternary ammonium salt ionic liquid to the phenol model oil is 1:2, the reaction temperature is 25°C, after stirring on a magnetic stirrer for different reaction times, the phenol concentration in the upper oil phase is measured by gas chromatograph, and the phenol extraction rates are calculated to be 99.25%, 99.60%, and 99.10%, respectively, and the optimal reaction time of the quaternary ammonium salt ionic liquid and the phenol model oil is 70min.

[0048] From the above examples, it can be concluded that the optimal reaction conditions are a mass ratio of ionic liquid to model oil of 1:2, a reaction temperature of 25°C, and a reaction time of 70 min. The phenol concentration in the upper oil phase is measured by gas chromatography, and the phenol extraction rate is 99.9%. The phenol extraction efficiency E% is calculated according to the following formula:

[0049] E%=(C0V0-C t V t ) / C0V0×100%, where

[0050] C0 represents the initial concentration of phenol in the phenol model oil, g / L

[0051] V0 is the initial volume of phenol model oil, mL

[0052] C t Represents the concentration of residual phenol in the toluene phase after extraction, g / L

[0053] V t The volume of phenol remaining in the toluene phase after extraction, mL

[0054] like Figure 1The NMR spectrum of L-carnitine-ethylene glycol ionic liquid is shown in the figure. From the figure, we can see that the structure of the new extractant synthesized from L-carnitine and ethylene glycol is not only conjugated on the benzene ring, but also has a hydroxyl functional group, which can form a hydrogen bond with phenol to achieve a better extraction effect.

[0055] like Figure 2 The FTIR spectrum of L-carnitine-ethylene glycol ionic liquid is shown in the figure. It can be seen from the figure that L-carnitine-ethylene glycol ionic liquid has a characteristic peak at 3395 cm -1 The stretching vibration of hydrogen bond -0H appears at 1084cm -1 There is obvious CN bond stretching vibration at 880 -1 The typical para-substitution of the aromatic ring appeared at the position of the 2-hydroxy-1-nitropropene, which verified the successful synthesis of L-carnitine-ethylene glycol ionic liquid.

Claims

1. A quaternary ammonium salt ionic liquid, characterized in that: The quaternary ammonium salt ionic liquid is L-carnitine-ethylene glycol ionic liquid, which is non-volatile, easily soluble in organic solvents, has a temperature operating range of 10-100° C., and has the following structural formula:

2. The method for preparing a quaternary ammonium salt ionic liquid according to claim 1, wherein The following steps are involved: Step (1) Grinding of L-carnitine: Grind a certain amount of L-carnitine solid into powder, dry it in a vacuum drying oven, and then place it on tin foil for later use; Step (2) Synthesis of L-carnitine-ethylene glycol ionic liquid: Take an appropriate amount of L-carnitine solid powder and add it into ethylene glycol solution to completely dissolve it to obtain the target product L-carnitine-ethylene glycol ionic liquid.

3. The method for preparing a quaternary ammonium salt ionic liquid according to claim 2, wherein In step (2), the molar ratio of L-carnitine to ethylene glycol in the ionic liquid is 1:1-1:

16.

4. The method for extracting phenol from phenol-containing wastewater using a quaternary ammonium salt ionic liquid according to claim 1, characterized in that: The following steps are involved: Step (1) using a quaternary ammonium salt ionic liquid as an extractant to carry out an extraction reaction with a phenol model oil simulating phenol-containing wastewater, and then standing to perform phase separation, thereby finally obtaining an upper oil phase from which phenol is removed and a lower ionic liquid phase containing phenol; Step (3) adding stripping agent ethyl acetate to the lower layer of the ionic liquid phase containing phenol, stirring and standing to separate the layers, the upper layer is the stripping agent phase containing phenol, and the lower layer is a quaternary ammonium salt ionic liquid extractant, and the quaternary ammonium salt ionic liquid can be regenerated and used; Step (4) adds phenol model oil in the same mass ratio as that in step (1) to the quaternary ammonium salt ionic liquid extractant, performs cyclic extraction, and the number of cycles is 4-10 times, and the phenol-containing stripping agent phase is distilled to obtain product phenol and stripping agent, and the stripping agent can be reused.

5. A method for extracting phenol from phenol-containing wastewater using a quaternary ammonium salt ionic liquid according to claim 4, characterized in that: In step (1), the mass ratio of the quaternary ammonium salt ionic liquid to the phenol model oil is 1:1-1:

6.

6. A method for extracting phenol from phenol-containing wastewater using a quaternary ammonium salt ionic liquid according to claim 4, characterized in that: In step (1), the extraction reaction temperature is 25-50°C.

7. The method for extracting phenol from phenol-containing wastewater using a quaternary ammonium salt ionic liquid according to claim 4, characterized in that: In step (1), the extraction reaction time is 10-110 min.

8. The method for extracting phenol from phenol-containing wastewater using a quaternary ammonium salt ionic liquid according to claim 4, characterized in that: The extraction rate of phenol in step (1) is 89.94%-99.9%; The extraction efficiency E% of phenol was calculated according to the following formula: E%=(C0V0-C t V t ) / C0V0×100%, where C0 represents the initial concentration of phenol in the phenol model oil, g / L V0 is the initial volume of phenol model oil, mL C t Represents the concentration of residual phenol in the toluene phase after extraction, g / L V t The volume of phenol remaining in the toluene phase after extraction, mL.

9. The method for extracting phenol from phenol-containing wastewater using a quaternary ammonium salt ionic liquid according to claim 4, characterized in that: The preparation method of phenol model oil is as follows: phenol-containing wastewater is mainly composed of neutral hydrocarbons, namely aromatic hydrocarbons and aliphatic hydrocarbons, acidic phenols, and a small amount of free water; in order to reduce the difficulty of analysis, phenol and toluene are used to simulate phenol model oil, wherein phenol represents acidic phenols, toluene represents neutral hydrocarbons, and the concentration of phenol in phenol model oil is 50-200g / L.

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