Method for extracting 2, 4-dibromophenol from tetrabromobisphenol A production wastewater

Abstract

The invention relates to the technical field of production wastewater, in particular to a method for extracting 2, 4-dibromophenol by using tetrabromobisphenol A production wastewater, which comprises the following steps: acidizing and filtering the tetrabromobisphenol A production wastewater, and extracting and separating the obtained filtrate by using carbon disulfide as an organic solvent to obtain a carbon disulfide solution with high organic concentration; then distilling the carbon disulfide solution with high organic concentration, synchronously separating out 2, 4-dibromophenol and tribromophenol while realizing conversion of carbon disulfide into a gaseous state according to a distillation boiling point, and further cooling the obtained mixed filtrate to obtain 2, 4-dibromophenol. The method is favorable for realizing resource recycling of the tetrabromobisphenol A wastewater, reducing the COD (Chemical Oxygen Demand) organic content of the wastewater, reducing the pressure and load of a subsequent water treatment system, and providing an achievable path for recycling dibromophenol generally existing in tetrabromobisphenol A production enterprises.

Description

Technical Field

[0001] The invention relates to the technical field of production wastewater, and in particular to a method for extracting 2,4-dibromophenol by utilizing tetrabromobisphenol A production wastewater. Background Art

[0002] 2,4-Dibromophenol is an organic compound that is widely used in the fields of chemical industry, medicine, pesticide, etc. In the chemical industry, due to its good stability and solubility, it is often used as a flame retardant, preservative and antioxidant; in the pharmaceutical field, it is widely used as a disinfectant and antibacterial agent; in the pesticide field, it is often used to prepare insecticides, fungicides and herbicides.

[0003] During the production process of tetrabromobisphenol A, a large amount of wastewater is generated. The wastewater contains a large amount of organic matter. By lowering the pH value, a large amount of organic matter insoluble in an acidic environment can be precipitated, but 2,4-dibromophenol cannot be separated in this form. Therefore, it not only causes a waste of resources, but also increases the cost of subsequent water treatment. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the related art. To this end, the object of the present invention is to provide a method for extracting 2,4-dibromophenol using tetrabromobisphenol A production wastewater.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A method for extracting 2,4-dibromophenol using tetrabromobisphenol A production wastewater comprises the following steps: S100, adjusting the pH of wastewater generated in the production process of tetrabromobisphenol A to a pH of 3 to 5, filtering the wastewater to obtain a first filtrate; Among them, 2,4-dibromophenol is extracted from the wastewater obtained in the production process of tetrabromobisphenol A. The main components of inorganic salts contained in the raw material are sodium sulfate and sodium bromide, the inorganic solvent is water, and the organic components contained are tetrabromobisphenol A, dibromo-4-hydroxybenzaldehyde, 2,4,6-tribromophenol, 2,4-dibromophenol, 2,6-dibromophenol, bisphenol A, chlorobenzene, etc., among which 2,4-dibromophenol accounts for about 5% to 8% of the wastewater mass; the pH of the wastewater is adjusted to precipitate the acid-insoluble substances; S200, adding an alkaline solution to the first filtrate to adjust the pH to 6.5-7.5, filtering to obtain a second filtrate; S300, introducing carbon disulfide solution into the second filtrate at a temperature of 15°C to 35°C, stirring, standing, and separating to obtain a lower layer solution; starting stirring to fully disperse and mix the solution, and the upper layer aqueous solution continues to participate in the water treatment system; S400, heating, stirring, and evaporating the lower layer solution obtained in step S300 to obtain a third filtrate; S500, cooling, filtering, and drying the third filtrate obtained in step S400 to obtain 2,4-dibromophenol.

[0006] Preferably, in step S100, the pH of the wastewater is adjusted using any one of a dilute sulfuric acid solution, a hydrochloric acid solution and a nitric acid solution.

[0007] Preferably, in step S200, the alkaline solution is one or more of a sodium hydroxide solution, a sodium carbonate solution and a sodium bicarbonate solution.

[0008] Preferably, in step S300, the volume of carbon disulfide added is 15% to 30% of the volume of the wastewater. In this step, the proportion of carbon disulfide added should not be too high, and the above addition ratio is sufficient to achieve the extraction and migration of 2,4-dibromophenol, and a too high proportion of carbon disulfide solution will additionally absorb other trace organic matter. At the same time, the proportion of carbon disulfide added should not be too low, otherwise it is difficult to ensure the extraction effect.

[0009] Preferably, in step S300, the volume of carbon disulfide added is 20% to 26% of the volume of the wastewater.

[0010] Preferably, in step S300, the stirring time is 30 min to 50 min, and the standing time is 30 min to 40 min.

[0011] Preferably, the steam generated by evaporation in step S400 is collected and cooled to obtain carbon disulfide for further recycling.

[0012] Preferably, in step S400, the temperature is raised to 42° C. to 50° C. For the remaining liquid in the reactor after evaporation, the temperature is maintained between 42° C. and 50° C. during the filtration operation, which is conducive to ensuring the recovery rate.

[0013] Preferably, in step S400, the lower layer solution is heated by a temperature increasing reactor.

[0014] Preferably, in step S500, the temperature is reduced to 30°C to 35°C, which can effectively improve the purity of the final product.

[0015] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: The invention provides a method for extracting 2,4-dibromophenol by using tetrabromobisphenol A production wastewater. After the tetrabromobisphenol A production wastewater is acidified and filtered, the obtained filtrate is extracted and separated by using carbon disulfide as an organic solvent to obtain a carbon disulfide solution with a high organic concentration. The carbon disulfide solution with a high organic concentration is then distilled. When the carbon disulfide is converted into a gaseous state according to the distillation boiling point and precipitated, 2,4-dibromophenol and tribromophenol are precipitated simultaneously. The obtained mixed filtrate is further cooled to obtain 2,4-dibromophenol.

[0016] The present invention provides a method for extracting 2,4-dibromophenol by utilizing tetrabromobisphenol A production wastewater, which is beneficial to realizing resource recovery and utilization of tetrabromobisphenol A wastewater, recovering 2,4-dibromophenol, reducing COD organic content of wastewater, reducing pressure and load of subsequent water treatment systems, and providing a feasible path for the recovery and treatment of dibromophenol commonly existing in tetrabromobisphenol A production enterprises.

[0017] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0019] In the following examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all available from commercial sources unless otherwise specified.

[0020] Example 1 The wastewater obtained in the production process of tetrabromobisphenol A is used as raw material. The main inorganic salt components contained in the raw material are sodium sulfate (about 2% by mass) and sodium bromide (about 0.6% by mass), the inorganic solvent is water (about 84% by mass), and the organic components contained are tetrabromobisphenol A (about 4% by mass), dibromo-4-hydroxybenzaldehyde (about 0.6% by mass), 2,4,6-tribromophenol (about 0.6% by mass), 2,4-dibromophenol (about 5% by mass), 2,6-dibromophenol (about 3% by mass), bisphenol A (about 0.05% by mass), chlorobenzene (about 0.15% by mass), etc., among which 2,4-dibromophenol accounts for about 4% to 8% of the wastewater mass. Add dilute sulfuric acid solution to the above waste water (200 g) to adjust the pH to about 3.5, filter the organic insoluble matter precipitated in the process by using a filtering device, and adjust the first filtrate obtained after filtration to neutrality by using a sodium hydroxide solution. In the process, the precipitated organic insoluble matter (5.22 g) is mainly composed of tetrabromobisphenol A and 2,4,6-tribromophenol, wherein the precipitation amount of tetrabromobisphenol A is 40% to 60%, and the precipitation amount of tribromophenol is 80% to 100%, and a second filtrate (216.35 g) is obtained; Pure carbon disulfide solution (48.07 g) was introduced into the second filtrate, and the addition ratio of carbon disulfide was 22% of the volume ratio of the second filtrate. Stirring was started to fully disperse and mix the above two solutions. The stirring mixing time was 35 minutes. The temperature of the reaction system was maintained at 25°C. After stirring, it was allowed to stand for 30 minutes before separation. After separation, the oil phase lower layer solution (65.07 g) was obtained. The upper aqueous solution was circulated to the wastewater system to continue to participate in the water treatment system. Carbon disulfide was used as a solvent in the lower layer solution, and the main organic components were organic substances such as 2,4,6-tribromophenol, 2,4-dibromophenol, 2,6-dibromophenol and chlorobenzene.

[0021] The lower layer solution is passed into the temperature-raising reactor for temperature-raising operation, stirring is started, the rotation speed is maintained at 100 rpm, the system temperature is maintained at 45°C, the obtained volatile vapor is collected and the gas is cooled with cooling water. This part of the gas is mainly carbon disulfide, which is used for further recycling. After the evaporation of the evaporation system is completed, a total of carbon disulfide condensate (47.85g) is obtained. The reaction temperature of the system is maintained at 45°C, and the remaining material in the reactor is filtered to obtain a third filtrate (10.5g). The third filtrate is mainly composed of 2,4-dibromophenol, a small amount of chlorobenzene and water, and the filter cake (6.52g) is mainly composed of tribromophenol and 2,6-dibromophenol.

[0022] The third filtrate was further cooled to 32° C. and filtered to obtain a filter cake. The filter cake was dried to obtain 2,4-dibromophenol (9.32 g) with a purity of 91.2%.

[0023] Example 2 The wastewater obtained in the production process of tetrabromobisphenol A is used as raw material. The main inorganic salt components contained in the raw material are sodium sulfate (about 2% by mass) and sodium bromide (about 0.6% by mass), the inorganic solvent is water (about 84% by mass), and the organic components contained are tetrabromobisphenol A (about 4% by mass), dibromo-4-hydroxybenzaldehyde (about 0.6% by mass), 2,4,6-tribromophenol (about 0.6% by mass), 2,4-dibromophenol (about 5% by mass), 2,6-dibromophenol (about 3% by mass), bisphenol A (about 0.05% by mass), chlorobenzene (about 0.15% by mass), etc., among which 2,4-dibromophenol accounts for about 4% to 8% of the wastewater mass. Add dilute sulfuric acid solution to the above wastewater (1000g) to adjust the pH to about 3.5, filter the organic insoluble matter precipitated in the process by using a filtering device, and adjust the first filtrate obtained after filtration to neutrality by using a sodium hydroxide solution. In the process, the precipitated organic insoluble matter (27.35g) is mainly composed of tetrabromobisphenol A and 2,4,6-tribromophenol, wherein the precipitation amount of tetrabromobisphenol A is 40% to 60%, and the precipitation amount of tribromophenol is 80% to 100%, and a second filtrate (1063.13g) is obtained; Pure carbon disulfide solution (265.78 g) was introduced into the second filtrate, and the addition ratio of carbon disulfide was 25% of the volume ratio of the second filtrate. Stirring was started to fully disperse and mix the above two solutions. The stirring mixing time was 35 minutes. The temperature of the reaction system was maintained at 25°C. After stirring, it was allowed to stand for 35 minutes before separation. After separation, the oil phase lower layer solution (320.31 g) was obtained. The upper aqueous solution was circulated to the wastewater system to continue to participate in the water treatment system. Carbon disulfide was used as a solvent in the lower layer solution, and the main organic components were organic substances such as 2,4,6-tribromophenol, 2,4-dibromophenol, 2,6-dibromophenol and chlorobenzene.

[0024] The lower layer solution is passed into the temperature-raising reactor for temperature-raising operation, stirring is started, the rotation speed is maintained at 110 rpm, the system temperature is maintained at 44°C, the obtained volatile vapor is collected and the gas is cooled with cooling water. This part of the gas is mainly carbon disulfide, which is used for further recycling. After the evaporation of the evaporation system is completed, a total of carbon disulfide condensate (246.25g) is obtained. The reaction temperature of the system is maintained at 45°C, and the remaining material in the reactor is filtered to obtain a third filtrate (45.88g). The third filtrate is mainly composed of 2,4-dibromophenol, a small amount of chlorobenzene and water, and the filter cake (28.23g) is mainly composed of tribromophenol and 2,6-dibromophenol.

[0025] The third filtrate was further cooled to 32° C. and filtered to obtain a filter cake. The filter cake was dried to obtain 2,4-dibromophenol (40.06 g) with a purity of 89.35%.

[0026] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for extracting 2,4-dibromophenol from tetrabromobisphenol A production wastewater, characterized in that: The steps include: S100, adjusting the pH of wastewater generated in the production process of tetrabromobisphenol A to a pH of 3 to 5, filtering the wastewater to obtain a first filtrate; S200, adding an alkaline solution to the first filtrate to adjust the pH to 6.5-7.5, filtering to obtain a second filtrate; S300, introducing carbon disulfide solution into the second filtrate at a temperature of 15°C to 35°C, stirring, standing, and separating the liquids to obtain a lower layer solution; S400, heating, stirring, and evaporating the lower layer solution obtained in step S300 to obtain a third filtrate; S500, cooling, filtering, and drying the third filtrate obtained in step S400 to obtain 2,4-dibromophenol.

2. The method for extracting 2,4-dibromophenol from tetrabromobisphenol A production wastewater as claimed in claim 1, characterized in that: In step S100, the pH value of the wastewater is adjusted by using any one of a dilute sulfuric acid solution, a hydrochloric acid solution and a nitric acid solution.

3. The method for extracting 2,4-dibromophenol from tetrabromobisphenol A production wastewater as claimed in claim 1, characterized in that: In step S200, the alkaline solution is one or more of a sodium hydroxide solution, a sodium carbonate solution and a sodium bicarbonate solution.

4. The method for extracting 2,4-dibromophenol from tetrabromobisphenol A production wastewater as claimed in claim 1, characterized in that: In step S300, the volume of carbon disulfide added is 15% to 30% of the volume of the wastewater.

5. The method for extracting 2,4-dibromophenol from tetrabromobisphenol A production wastewater as claimed in claim 4, characterized in that: In step S300, the volume of carbon disulfide added is 20% to 26% of the volume of the wastewater.

6. The method for extracting 2,4-dibromophenol from tetrabromobisphenol A production wastewater as claimed in claim 1, characterized in that: In step S300, the stirring time is 30 min to 50 min, and the standing time is 30 min to 40 min.

7. The method for extracting 2,4-dibromophenol from tetrabromobisphenol A production wastewater as claimed in claim 1, characterized in that: The steam generated by evaporation in step S400 is collected and cooled to obtain carbon disulfide.

8. The method for extracting 2,4-dibromophenol from tetrabromobisphenol A production wastewater as claimed in claim 1, characterized in that: In step S400, the temperature rises to 42°C to 50°C.

9. The method for extracting 2,4-dibromophenol from tetrabromobisphenol A production wastewater as claimed in claim 1, characterized in that: In step S400, the lower layer solution is heated by using a temperature increasing reactor.

10. The method for extracting 2,4-dibromophenol from tetrabromobisphenol A production wastewater according to claim 1, characterized in that: In step S500, the temperature is reduced to 30°C to 35°C.