Method for separating phenol from phenol-containing wastewater by using imidazolyl ionic liquid

Abstract

The invention discloses a method for separating phenol in phenol-containing wastewater by using imidazolyl ionic liquid, which comprises the following steps of: performing extraction reaction on the imidazolyl ionic liquid serving as an extracting agent and phenol model oil for simulating the phenol-containing wastewater, and standing for phase separation to obtain an upper layer oil phase without phenol and a lower layer phenol-containing ionic liquid phase; adding a stripping agent ethyl acetate into a lower layer phenol-containing ionic liquid phase, stirring, standing and layering to obtain an upper layer which is a phenol-containing stripping agent phase and a lower layer which is an imidazolyl ionic liquid extraction agent, adding phenol model oil with the same mass ratio as that at the beginning of extraction into the imidazolyl ionic liquid extraction agent, and performing cyclic extraction for 4-10 times; the stripping agent phase containing phenol is rectified to obtain the product phenol and the stripping agent ethyl acetate, and the stripping agent ethyl acetate can be repeatedly used. According to the method, the imidazolyl ionic liquid is used as the extraction agent, phenol is separated from the phenol-containing wastewater, the extraction effect is improved, the ionic liquid can be recycled, no pollution is caused to the environment, and the method is an economical and practical environment-friendly technology.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a method for separating phenol from phenol-containing wastewater using imidazole-based ionic liquid. 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 of great significance for environmental improvement and water quality improvement, but also can obtain compounds with high added value.

[0003] Liquid-liquid extraction for treating phenol-containing wastewater has the advantages of high recovery rate, reusable solvents and low cost. It is a common phenol-containing wastewater recovery and treatment process in industrial applications. By utilizing the difference in solubility of phenol in wastewater and organic solvents, phenol is transferred from wastewater to the organic phase, and the wastewater is purified by separating the organic phase and the aqueous phase. Common extractants include benzene, light oil, ethyl acetate, tributyl phosphate, methyl isobutyl ketone, etc. However, many traditional extractants are highly volatile and prone to produce waste gas. Researchers are also actively looking for some emerging extractants. 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 method for separating phenol from phenol-containing wastewater by using imidazolyl ionic liquid. The imidazolyl ionic liquid used as the extractant in the present invention is easy to separate from other substances and can be recovered and reused by simple treatment, thereby reducing production costs and waste generation, and can be recycled, which is in line with the concept of green environmental protection.

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

[0006] A method for separating phenol from phenol-containing wastewater using an imidazolyl ionic liquid comprises the following steps:

[0007] Step (1): using an imidazole-based 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 has been removed and a lower ionic liquid phase containing phenol;

[0008] Step (2): adding ethyl acetate as a stripping agent to the lower phenol-containing ionic liquid phase, stirring and standing to separate the layers, the upper layer is the stripping agent phase containing phenol, and the lower layer is an imidazole-based ionic liquid extractant, which can be regenerated and used;

[0009] Step (3): adding phenol model oil in the same mass ratio as that in step (1) to the imidazole-based ionic liquid extractant, and performing cyclic extraction, the number of cycles being 4-10 times; and distilling the phenol-containing stripping agent phase to obtain product phenol and stripping agent ethyl acetate, and the stripping agent ethyl acetate can be reused.

[0010] The mass ratio of the imidazolyl ionic liquid to the phenol-containing wastewater is 1:5-1:30.

[0011] In step (2), ethyl acetate is added as a stripping agent to the lower phenol-containing ionic liquid phase, wherein the mass ratio of ethyl acetate as the stripping agent to the lower phenol-containing ionic liquid phase is 1:1-1:10.

[0012] The imidazolyl ionic liquid is 1-butyl-3-methylimidazolium chloride, and the structural formula is as follows:

[0013]

[0014] The pH of the phenol-containing wastewater is 4-7.

[0015] The extraction temperature is 25-50°C.

[0016] The extraction time is 1-7 min.

[0017] The extraction rate of phenol in step (1) is 79.08%-99.99%;

[0018] The extraction efficiency E% of phenol was calculated according to the following formula:

[0019] E%=(C 0 V 0 -C t V t ) / C 0 V 0 × 100%, where

[0020] C 0 represents the initial concentration of phenol in the phenol model oil, g / L

[0021] V 0 is the initial volume of phenol model oil, mL

[0022] C t Represents the concentration of residual phenol in the toluene phase after extraction, g / L

[0023] V t The volume of phenol remaining in the toluene phase after extraction, mL.

[0024] 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 solutions are used to simulate phenol-containing wastewater, wherein phenol represents acidic phenols, toluene represents neutral hydrocarbons, and the concentration of phenol in phenol model oil is 50-200g / L.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The imidazolyl ionic liquid extractant used in the present invention is easily soluble in organic solvents, has low vapor pressure and is non-volatile; the imidazolyl ionic liquid has a wide operating temperature range of 25-50°C, so that it can remain stable under various temperature conditions; the imidazolyl ionic liquid is easily separated from other substances, and can be recovered and reused through simple treatment, thereby reducing production costs and waste generation, and can be recycled; after 4-10 cycles of extraction, the extractant still exhibits a strong extraction and separation ability, which is in line with the concept of green environmental protection.

[0027] Imidazole-based ionic liquids have low requirements for extraction temperature and extraction pressure, are easy to operate, and reduce energy consumption and equipment costs; they are applicable to phenol-containing wastewaters of different concentrations, and can effectively extract both high-concentration and low-concentration wastewater.

[0028] The invention uses 1-butyl-3-methylimidazolium chloride ionic liquid as an extractant, and realizes the separation of phenol in phenol-containing wastewater by forming hydrogen bonds between phenol and strongly polar atoms contained in anions and cations. The separation method has mild experimental operation conditions and can be carried out at room temperature. The ionic liquid is easy to separate and recycle, which simplifies the separation operation. Compared with the traditional process, the method does not generate volatile organic pollutants during the extraction process and is more environmentally friendly. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with specific embodiments, a method for separating phenol from phenol-containing wastewater using imidazolyl ionic liquid, but is not limited to the following embodiments.

[0030] 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, the present invention uses phenol and toluene to simulate phenol model oil, wherein phenol represents acidic phenolic substances and toluene represents neutral hydrocarbon substances.

[0031] 1-Butyl-3-methylimidazolium chloride ionic liquid has high thermal stability, and the thermal decomposition temperature can reach above 200°C; 1-Butyl-3-methylimidazolium chloride ionic liquid has a low melting point and is liquid at room temperature. The low melting point property makes 1-Butyl-3-methylimidazolium chloride ionic liquid have advantages in low-temperature applications: 1-Butyl-3-methylimidazolium chloride ionic liquid has a relatively high viscosity, generally much higher than common organic solvents.

[0032] Example 1: A method for separating phenol from phenol model oil using imidazolyl ionic liquid

[0033] At the beginning, the imidazole-based 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 phenol extraction rate can reach 99.99%; ethyl acetate is added as a stripping agent 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 imidazole-based ionic liquid extractant, and the imidazole-based ionic liquid extractant can be recycled; the phenol model oil is added to the imidazole-based ionic liquid extractant in the same mass ratio as that at the beginning, and cyclic extraction is performed, wherein the number of cycles is 4-10. The stripping agent phase containing phenol is rectified to obtain product phenol and stripping agent ethyl acetate, and the stripping agent can be reused.

[0034] Example 2: Effect of different pH values ​​of an imidazolyl ionic liquid and phenol model oil on phenol extraction efficiency

[0035] The imidazolyl ionic liquid is 1-butyl-3-methylimidazolium chloride ionic liquid. The imidazolyl ionic liquid and the phenol model oil are stirred on a magnetic stirrer for 5 minutes at different pH values ​​of 4, 5, 6, and 7. When the reaction temperature of the imidazolyl ionic liquid and the phenol model oil is 25°C, the phenol concentration in the upper oil phase is determined by a gas chromatograph, and the phenol extraction rates are calculated to be 92.93%, 97.63%, 93.08%, and 90.80%, respectively, and the optimal pH value for the reaction of the imidazolyl ionic liquid and the phenol model oil is 5.

[0036] Example 3: Effect of different mass ratios of an imidazolyl ionic liquid to phenol model oil on phenol extraction efficiency

[0037] The imidazolyl ionic liquid is 1-butyl-3-methylimidazolium chloride ionic liquid. When the imidazolyl ionic liquid and the phenol model oil react at different mass ratios of 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, and when the reaction temperature of the imidazolyl ionic liquid and the model oil is 25°C, the mixture is stirred on a magnetic stirrer for 5 minutes, and the phenol concentration in the upper oil phase is measured by gas chromatography. The phenol extraction rates are calculated to be 99.93%, 98.63%, 93.08%, 88.80%, 85.98%, and 79.08%, respectively, and the optimal mass ratio of the imidazolyl ionic liquid to the phenol model oil is 1:5.

[0038] Example 4: Effect of different reaction temperatures of an imidazolyl ionic liquid and phenol model oil on phenol extraction efficiency

[0039] The imidazolyl ionic liquid is 1-butyl-3-methylimidazolium chloride ionic liquid. The imidazolyl ionic liquid and the phenol model oil are stirred on a magnetic stirrer for 5 minutes at different reaction temperatures such as 25°C, 30°C, 35°C, 40°C, 45°C, and 50°C. When the mass ratio of the imidazolyl ionic liquid to the phenol model oil is 1:5, the phenol concentration in the upper oil phase is determined by gas chromatography, and the phenol extraction rates are calculated to be 99.26%, 96.68%, 97.75%, 97.26%, 96.68%, and 95.75%, respectively, and the optimal temperature for the reaction of the imidazolyl ionic liquid and the phenol model oil is 25°C.

[0040] Example 5: Effect of different reaction times of an imidazolyl ionic liquid and phenol model oil on phenol extraction efficiency

[0041] The imidazolyl ionic liquid is 1-butyl-3-methylimidazolium chloride ionic liquid, and the imidazolyl ionic liquid and the phenol model oil are reacted at different reaction times of 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, etc. When the mass ratio of the imidazolyl ionic liquid to the phenol model oil is 1:5, and the reaction temperature is 25°C, after stirring with a magnetic stirrer for the above different time, the phenol concentration in the upper oil phase is measured by gas chromatograph, and the phenol extraction rates are calculated to be 98.25%, 96.96%, 97.90%, 96.25%, 99.99%, 94.90%, 93.86%, respectively, and the optimal reaction time of the imidazolyl ionic liquid and the phenol model oil is 5 min.

[0042] From the above examples, it can be concluded that the optimal reaction conditions are that the pH value of the ionic liquid and the phenol model oil is 5, the mass ratio is 1:5, the reaction temperature is 25°C, and the reaction time is 5 minutes. The phenol concentration in the upper oil phase is measured by gas chromatography, and the phenol extraction rate is 99.9%. The extraction efficiency (E%) of phenol is calculated according to the following formula:

[0043] E%=(C 0 V 0 -C t V t ) / C 0 V 0 × 100%, where

[0044] C 0 represents the initial concentration of phenol in the model oil, g / L

[0045] V 0 is the initial volume of the model oil, mL

[0046] C t Represents the concentration of residual phenol in the toluene phase after extraction, g / L

[0047] V t The volume of phenol remaining in the toluene phase after extraction, mL.

[0048] 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 have a relatively low vapor pressure and relatively stable chemical properties. Ionic liquids themselves have good phase-forming ability and can achieve good separation effects at a relatively small dosage. The extractant 1-butyl-3-methylimidazolium chloride ionic liquid used in the present invention can form hydrogen bonding, π-π conjugation and weak van der Waals forces with phenol, providing a way to extract phenol from phenol-containing wastewater.

Claims

1. A method for separating phenol from phenol-containing wastewater using an imidazolyl ionic liquid, characterized in that: The following steps are involved: Step (1): using an imidazole-based 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 has been removed and a lower ionic liquid phase containing phenol; Step (2): adding ethyl acetate as a stripping agent to the lower phenol-containing ionic liquid phase, stirring and standing to separate the layers, the upper layer is the stripping agent phase containing phenol, and the lower layer is an imidazole-based ionic liquid extractant, which can be regenerated and used; Step (3): adding phenol model oil in the same mass ratio as that in step (1) to the imidazole-based ionic liquid extractant, and performing cyclic extraction, the number of cycles being 4-10 times; and distilling the phenol-containing stripping agent phase to obtain product phenol and stripping agent ethyl acetate, and the stripping agent ethyl acetate can be reused.

2. The method for separating phenol from phenol-containing wastewater using an imidazolyl ionic liquid according to claim 1, characterized in that: The mass ratio of the imidazolyl ionic liquid to the phenol-containing wastewater is 1:5-1:

30.

3. The method for separating phenol from phenol-containing wastewater using an imidazolyl ionic liquid according to claim 1, characterized in that: In step (2), ethyl acetate is added as a stripping agent to the lower phenol-containing ionic liquid phase, wherein the mass ratio of ethyl acetate as the stripping agent to the lower phenol-containing ionic liquid phase is 1:1-1:

10.

4. The method for separating phenol from phenol-containing wastewater using an imidazolyl ionic liquid according to claim 1, characterized in that: The imidazolyl ionic liquid is 1-butyl-3-methylimidazolium chloride, and the structural formula is as follows:

5. The method for separating phenol from phenol-containing wastewater using an imidazolyl ionic liquid according to claim 1, characterized in that: The pH of the phenol-containing wastewater is 4-7.

6. The method for separating phenol from phenol-containing wastewater using an imidazolyl ionic liquid according to claim 1, characterized in that: The extraction temperature is 25-50°C.

7. The method for separating phenol from phenol-containing wastewater using an imidazolyl ionic liquid according to claim 1, characterized in that: The extraction time is 1-7 min.

8. The method for separating phenol from phenol-containing wastewater using an imidazole-based ionic liquid according to claim 1, characterized in that: The extraction rate of phenol in step (1) is 79.08%-99.99%; 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 separating phenol from phenol-containing wastewater using an imidazolyl ionic liquid according to claim 1, 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 solutions are used to simulate phenol-containing wastewater, 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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