CN106865675B - A kind of extraction and dephenolization method of phenol-containing wastewater - Google Patents

Abstract

The invention provides an extraction and dephenolization method for phenol-containing wastewater, comprising the following steps: performing multi-stage countercurrent extraction with an extraction agent at a temperature of 20-35° C. to obtain an extraction phase and a raffinate phase, and the extraction agent For cyclic ketones, the pH value of phenol-containing wastewater is 6-7. The extraction and dephenolization method of the invention has a removal rate of more than 96.5% for phenols in phenol-containing wastewater, and more phenols can be recovered; at the same time, the removal rate of polyphenols in phenols is remarkable, and phenols remain in wastewater. The concentration is greatly reduced, which is beneficial to the subsequent biochemical treatment, improves the quality of biochemical effluent, and greatly reduces the difficulty of wastewater reuse and treatment; the operating conditions of the equipment are changed little, which is conducive to rapid application to the extraction and dephenolization process.

Description

A kind of extraction and dephenolization method of phenol-containing wastewater

technical field

The invention belongs to the technical field of wastewater treatment, and in particular relates to a method for extracting and dephenolizing phenol-containing wastewater.

Background technique

Phenols are oxygen-containing derivatives of aromatic hydrocarbons, which are highly toxic and difficult to degrade. Direct discharge will cause serious pollution to water bodies. Phenol-containing wastewater mainly comes from the production process of coal chemical industry, petrochemical industry, dyestuff, organic pesticides, etc., especially coal chemical industry, which not only has a large amount of wastewater, but also has high phenol content. At home and abroad, the treatment of phenol-containing wastewater has been paid great attention, and a lot of research has been carried out, but the main industrial application is the extraction method.

Extractive dephenolization includes physical extraction and complex extraction. There are many types of extractants available, such as butyl acetate, methyl isobutyl ketone, diisopropyl ether, methyl tert-butyl ether, n-octanol, toluene, Physical extractants such as anthracene oil, or complex extractants such as trioctylphosphine oxide, trialkylphosphine oxide, tributyl phosphate, and trioctylamine. The distribution coefficient of complex extraction method is higher than that of physical method, and the extraction effect is good, but due to the difficulty in recovering the extractant, there are few industrial applications. Taking into account factors such as dephenolization efficiency, extraction agent recovery, and operating costs, physical extraction methods are currently mainly used, and the extraction agents are mainly methyl isobutyl ketone and diisopropyl ether.

Compared with diisopropyl ether, methyl isobutyl ketone has a certain improvement in the distribution coefficient of unit phenol and polyhydric phenol. Therefore, when methyl isobutyl ketone is used as the extractant, the dephenolization rate of phenol-containing wastewater is greatly improved. reached about 93%. However, the distribution coefficient of methyl isobutyl ketone to polyphenols is not high. For example, the distribution coefficient of resorcinol is about 18, and the distribution coefficient of phloroglucinol is about 5, which makes it difficult to further improve the removal of wastewater. Phenol rate.

Judging from the current implementation standards of environmental protection regulations, due to the country's increasing emphasis on environmental protection, in order to protect the environment and water resources and reduce pollution, the discharge standards are also becoming stricter. Upgrade to Tier 1 emission standards. For new coal chemical enterprises, it is often required to have zero discharge of wastewater, which puts forward high requirements for wastewater treatment and reuse. If the phenols can be removed as much as possible through pretreatment such as extraction, it will undoubtedly greatly reduce the pressure of biological treatment, which is of great significance to the subsequent advanced treatment and reuse of sewage, removal of organic matter in high-concentration brine and fractional crystallization. Therefore, it is particularly important to develop extractants with higher partition coefficients and higher removal rates for phenols.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a method for extraction and dephenolization of phenol-containing wastewater, which can have higher removal efficiency for phenols in wastewater.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is:

A method for extraction and dephenolization of phenol-containing wastewater, comprising the following steps: performing multi-stage countercurrent extraction on phenol-containing wastewater with an extraction agent at a temperature of 20-35° C. to obtain an extraction phase and a raffinate phase, and the extraction agent is cyclic ketones , the PH value of phenol-containing wastewater is 6-7.

The aforementioned cyclic ketones are cyclohexanone or 2-methylcyclohexanone.

The content of unit phenol in the above-mentioned phenol-containing wastewater is 4500-8500 mg/L, and the content of polyphenol is 3500-9500 mg/L.

The volume ratio of the above-mentioned extractant to the phenol-containing wastewater is 1:3-9.

Preferably, the volume ratio of the above-mentioned extractant to the phenol-containing wastewater is 1:5-7.

Preferably, the above-mentioned multi-stage countercurrent extraction is a three-stage countercurrent extraction.

The above-mentioned extraction and dephenolization method also includes entering the extraction phase into a rectifying tower to separate to obtain crude phenol and an extractant, or obtaining sodium phenate and an extractant through alkali washing, and entering the raffinate phase into a stripper to recover the residual extractant.

Compared with the prior art, the advantages of the present invention are: the removal rate of the phenols in the phenol-containing wastewater by the extraction and dephenolization method of the present invention reaches more than 96.5%, and more phenols can be recovered; The removal rate of polyphenols is remarkable, and the concentration of residual phenols in wastewater is greatly reduced, which is conducive to subsequent biochemical treatment, improves the quality of biochemical effluent, and greatly reduces the difficulty of wastewater reuse treatment; the operating conditions of the equipment are changed little, and there are It is beneficial to be quickly applied to the extraction and dephenolization process.

Detailed ways:

The present invention will be described in detail below with reference to the examples, but these examples are not intended to limit the present invention.

A method for extraction and dephenolization of phenol-containing wastewater, comprising the following steps: subjecting phenol-containing wastewater to three-stage countercurrent extraction with an extraction agent at a temperature of 20-35° C. to obtain an extraction phase and a raffinate phase, and the extraction agent is cyclic ketones , preferably cyclohexanone or 2-methylcyclohexanone, the pH value of phenol-containing wastewater is 6-7, the content of unit phenol in phenol-containing wastewater is 4500-8500mg/L, and the content of polyphenol is 3500-9500mg/L L, the volume ratio of extractant to phenol-containing wastewater is 1:3-9, preferably 1:5-7.

After extraction and dephenolization, the extraction phase is sent to a rectifying tower to separate crude phenol and extractant, or sodium phenolate and extractant are obtained by alkaline washing, and the raffinate phase is sent to a stripper to recover the residual extractant, so as to improve the resource utilization of waste water. Use level.

For physical extraction, the principle that the extractant extracts phenol from water is mainly that the two can form hydrogen bonds, which requires the extractant to have a strong polarity, but water is also a highly polar substance that can form with phenols. With strong hydrogen bonds, it is limited to increase the extraction efficiency solely by increasing the polarity of the extractant. From the point of view of intermolecular forces, the extraction of phenols by extractants, one is the formation of hydrogen bonds with each other, and the hydrophobic interaction between the other extractant and phenols, or similar compatibility cannot be ignored. According to this principle, if the non-polar end of the extractant has a ring like phenols, the effect of similar compatibility can be enhanced, thereby improving the extraction effect of phenols.

The present invention will be described in further detail below by means of examples.

Example 1

A method for extraction and dephenolization of phenol-containing wastewater, comprising the following steps: using cyclohexanone as an extractant at a temperature of 30° C. for phenol-containing wastewater with a unit phenol content of 5500 mg/L and a polyphenol content of 4600 mg/L A three-stage countercurrent extraction was performed to obtain an extract phase and a raffinate phase. Among them, the pH value of phenol-containing wastewater is 6.5, and the volume ratio of extractant to phenol-containing wastewater is 1:6.

The raffinate phase was detected, and the residual concentration of unit phenol was 85 mg/L, the residual concentration of polyphenol was 180 mg/L, and the concentration of total phenol was 265 mg/L. The calculation shows that the removal rate of unit phenol is 98.5%, the removal rate of polyphenol is 96.0%, and the removal rate of total phenol is 97.4%.

Example 2

A method for extraction and dephenolization of phenol-containing wastewater, comprising the following steps: using cyclohexanone as an extractant at a temperature of 25° C. for phenol-containing wastewater with a unit phenol content of 8300 mg/L and a polyphenol content of 9300 mg/L A three-stage countercurrent extraction was performed to obtain an extract phase and a raffinate phase. Among them, the pH value of the phenol-containing wastewater is 7, and the volume ratio of the extractant to the phenol-containing wastewater is 1:7.

The raffinate phase was detected, and the residual concentration of unit phenol was 130 mg/L, the residual concentration of polyphenol was 350 mg/L, and the concentration of total phenol was 480 mg/L. The calculation shows that the removal rate of unit phenol is 98.4%, the removal rate of polyphenol is 96.2%, and the removal rate of total phenol is 97.2%.

Example 3

A method for extraction and dephenolization of phenol-containing wastewater, comprising the following steps: using cyclohexanone as an extractant at a temperature of 25° C. for phenol-containing wastewater with a unit phenol content of 4800 mg/L and a polyphenol content of 3500 mg/L A three-stage countercurrent extraction was performed to obtain an extract phase and a raffinate phase. Among them, the pH value of the phenol-containing wastewater is 6, and the volume ratio of the extractant to the phenol-containing wastewater is 1:5.

The raffinate phase was detected, and the residual concentration of unit phenol was 75 mg/L, the residual concentration of polyphenol was 130 mg/L, and the concentration of total phenol was 205 mg/L. The calculation shows that the removal rate of unit phenol is 98.4%, the removal rate of polyphenol is 96.3%, and the removal rate of total phenol is 97.5%.

Example 4

A method for extraction and dephenolization of phenol-containing wastewater, comprising the following steps: using 2-methylcyclohexane in the phenol-containing wastewater with a unit phenol content of 5300 mg/L and a polyphenol content of 4200 mg/L at a temperature of 35° C. The ketone is used as the extractant for three-stage countercurrent extraction to obtain the extract phase and the raffinate phase. Among them, the pH value of phenol-containing wastewater is 6.5, and the volume ratio of extractant to phenol-containing wastewater is 1:6.

The raffinate phase was detected, and the residual concentration of unit phenol was 133 mg/L, the residual concentration of polyphenol was 164 mg/L, and the concentration of total phenol was 297 mg/L. The calculation shows that the removal rate of unit phenol is 97.5%, the removal rate of polyphenol is 96.1%, and the removal rate of total phenol is 96.8%.

According to the above examples, it can be seen that the extraction and dephenolization method of the present invention has a removal rate of more than 96.5% for phenols in phenol-containing wastewater, which is better than the existing extraction effect, and the removal rate of polyphenols in phenols is remarkable. , more phenols can be recovered for recycling.

Claims (3)

1. The extraction dephenolization method of the phenol-containing wastewater is characterized by comprising the following steps: performing multi-stage countercurrent extraction on the phenolic wastewater at the temperature of 20-35 ℃ by using an extracting agent to obtain an extraction phase and a raffinate phase, wherein the extracting agent is cyclic ketone, and the pH value of the phenolic wastewater is 6-7; the content of the unit phenol in the phenol-containing wastewater is 4500-8500mg/L, and the content of the polyhydric phenol is 3500-9500 mg/L; the volume ratio of the extracting agent to the phenol-containing wastewater is 1: 5-7; the cyclic ketone is cyclohexanone or 2-methylcyclohexanone.

2. The method for extracting and dephenolizing phenolic wastewater according to claim 1, wherein the multistage countercurrent extraction is three-stage countercurrent extraction.

3. The method for extracting and dephenolizing phenolic wastewater according to claim 1, further comprising the steps of feeding the extract phase into a rectifying tower to separate crude phenol and an extracting agent, or feeding sodium phenolate and an extracting agent through alkali washing, and feeding the raffinate phase into a stripping tower to recover residual extracting agent.