Treatment process for recovering isopropyl bromide from bromine-containing wastewater

Abstract

The invention discloses a treatment process for recovering isopropyl bromide from bromine-containing wastewater, and belongs to the technical field of bromine-containing wastewater recovery. The method comprises the following process steps: (1) introducing pretreated bromine-containing wastewater into an electrolysis device, and electrolyzing the bromine-containing wastewater; (2) collecting oxygen generated in the anode region and hydrogen generated in the cathode region, filtering and separating the electrolyzed bromine-containing wastewater through an ultrafiltration system to obtain filtrate, adding an extraction agent into the filtrate, stirring and mixing, and recovering bromine from an extraction phase; and (3) mixing sulfur and recycled bromine at 80 DEG C for 30 minutes, dropwise adding an isopropanol solution, and reacting at 75 DEG C for 1-2 hours to obtain isopropyl bromide. In the process of recovering isopropyl bromide from bromine-containing wastewater, flocculation and photocatalytic degradation of organic matters in the bromine-containing wastewater can be realized through the iron anode, and meanwhile, high-value hydrogen and oxygen are recovered.

Description

Technical Field

[0001] The invention belongs to the technical field of bromine-containing wastewater recovery, and in particular relates to a treatment process for recovering isopropyl bromide from bromine-containing wastewater. Background Art

[0002] Bromine-containing compounds are important fine chemicals, widely used as pharmaceutical intermediates, dye intermediates, gasoline additives, agricultural chemicals, flame retardants, and developers, etc. Isopropyl bromide is an important raw material in the etherification process of oxadiazon, and its purchase cost is relatively high. If it can be recycled from bromine-containing wastewater, the cost will be greatly reduced.

[0003] Patent CN 109456141 B reports a method for preparing isopropyl bromide from oxadiazon etherification wastewater. The method successfully prepares isopropyl bromide from oxadiazon etherification wastewater through the steps of neutralization; filtration and water washing; distillation and concentration; and synthesis. However, a large amount of concentrated acid is used during the operation, and the equipment occupies a large area, which affects its further promotion and use.

[0004] Therefore, it is necessary to provide a treatment process for recovering isopropyl bromide from bromine-containing wastewater which is green, simple in process, and occupies a small area. Summary of the invention

[0005] The object of the present invention is to provide a treatment process for recovering isopropyl bromide from bromine-containing wastewater to solve the problem of excessive use of strong acid in the process of recovering isopropyl bromide from bromine-containing wastewater in the background art.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A treatment process for recovering isopropyl bromide from bromine-containing wastewater comprises the following steps:

[0008] Step (1): passing the pretreated bromine-containing wastewater into an electrolysis device to electrolyze the pretreated bromine-containing wastewater;

[0009] Step (2): collecting oxygen generated in the anode region and hydrogen generated in the cathode region, filtering and separating the bromine-containing wastewater after electrolysis through an ultrafiltration system to obtain a filtrate, adding an extractant to the filtrate and stirring and mixing, and recovering bromine from the extract phase;

[0010] Step (3): Mix sulfur and recovered bromine at 80° C. for 30 minutes, then drop isopropanol solution into it, and control the temperature at 75° C. to react for 1-2 hours to obtain isopropyl bromide.

[0011] The present invention provides a treatment process for recovering isopropyl bromide from bromine-containing wastewater, wherein the bromine-containing wastewater contains bromide ions, COD and other suspended matter. If the unreacted isopropyl bromide in the waste liquid is directly recovered, the yield is negligible, so it is electrolyzed into bromine, and isopropyl bromide is further synthesized to achieve high-value recycling of the waste liquid. Therefore, the bromine-containing wastewater is first pretreated to remove the macromolecular suspended matter and particulate matter therein, and then the small particle suspended matter is removed by a flotation device, and the pretreated bromine-containing wastewater enters the electrolysis device. The electrolysis device adopts a dual anode and a single cathode setting. During the electrolysis process, the graphite cathode electrolyzes water to generate hydrogen, and the graphite anode reacts with bromide ions to generate bromine element, and generates oxygen when the waste liquid environment is alkaline. At the same time, the iron anode is electrolyzed into divalent iron or trivalent iron to flocculate with organic matter, and finally forms Fe 3 O 4 After the electrolysis is completed, the electrocoagulation precipitation and the bromine-containing waste liquid after electrolysis are separated by ultrafiltration membrane, and the generated gas in each electrode area is collected. The filtrate after ultrafiltration separation is mixed with the extractant for extraction, and the obtained bromine is added to the distillation tower containing sulfur and isopropanol to further synthesize isopropyl bromide.

[0012] Among them, the pretreatment in step (1) is to filter through a coarse grid with a gap of 10 mm and a fine grid with a gap of 2 mm, enter the flotation device to remove small suspended particles, and then enter the buffer tank.

[0013] Wherein, the bromine-containing wastewater in step (1) is oxadiazon etherification wastewater.

[0014] Wherein, the electrolysis in step (1) is performed by direct current electrolysis, the voltage between the anode and the cathode is 1.8-4.5V; the time is 12-24h; and the temperature is 50°C.

[0015] Wherein, the electrolysis device in step (1) is an ion exchange membrane electrolyzer, which is mainly composed of an anode, a cathode, an ion exchange membrane, and an electrolyzer frame.

[0016] Furthermore, the ion exchange membrane electrolyzer is a three-chamber ion exchange membrane electrolyzer, and each zone allows liquid electrolyte to flow freely through.

[0017] Furthermore, the ion exchange membrane electrolyzer is one of an inert asbestos membrane, a perfluorinated cation membrane or a perfluorinated anion membrane.

[0018] Furthermore, the anode is composed of an iron anode and a graphite anode.

[0019] Furthermore, the cathode is a graphite cathode.

[0020] Wherein, the step (2) of collecting the oxygen generated in the anode region and the hydrogen generated in the cathode region is to collect the oxygen from above the graphite anode and collect the hydrogen from above the graphite cathode after the electrolysis is completed.

[0021] Among them, the reactions occurring in the anode and cathode regions are:

[0022] anode:

[0023] 2Br - -2e - →Br 2 (1)

[0024] 4OH - -4e - →2H 2 O+O 2 (2)

[0025] cathode:

[0026] 2H + +2e - →2H 2 ↑ (3)

[0027] 2H 2 O+2e - →2H 2 ↑+OH - (4)

[0028] Regardless of whether the initial pH of the bromine-containing wastewater is acidic or alkaline, the pH after the reaction is complete is around 8, which fully meets the water quality discharge standard of pH 6-9.

[0029] The purpose of the ultrafiltration separation in step (2) is to remove organic matter and macromolecular substances precipitated by electrolytic flocculation of the iron anode.

[0030] The ultrafiltration separation in step (2) uses a Koch KOCH-MP8081-102 ultrafiltration membrane (molecular weight cutoff of 100,000), with an operating temperature of 30° C. and a pressure of 0.2 MPa.

[0031] Wherein, the extractant in step (2) is carbon tetrachloride or p-xylene.

[0032] Wherein, the method for recovering bromine in step (2) is distillation at 60° C. for 30 min.

[0033] Wherein, the volume ratio of the bromine-containing wastewater to the extractant is 600:200.

[0034] Wherein, the usage ratio of the sulfur, the recovered bromine and the isopropanol solution in step (3) is 12g:155g:160mL.

[0035] Furthermore, the purity of the sulfur is 99%, and the isopropanol solution is an isopropanol aqueous solution with a volume ratio of 95%.

[0036] Wherein, the reaction equation for preparing isopropyl bromide by recovering bromine is:

[0037] 6(CH 3 ) 2 CH 2 OH+3Br 2 +S→6(CH 3 ) 2 CH 2 Br+H 2 O+H 2 SO 4

[0038] Beneficial effects of the present invention:

[0039] 1. The present invention uses an iron electrode as an anode for electric flocculation, and does not need to add additional flocculants, so as to achieve flocculation of organic pollutants in bromine-containing wastewater, thereby saving costs and avoiding the introduction of impurity elements.

[0040] 2. The present invention adopts a dual anode strategy to produce oxygen and bromine at the graphite anode and hydrogen at the graphite cathode while achieving flocculation at the iron anode, thereby realizing the collection and utilization of additional high-value gases.

[0041] 3. The experimental device adopted by the present invention is simple and convenient, occupies little space, and is convenient for promotion and use.

[0042] 4. The process adopted by the present invention is simple and green, does not require the addition of corrosive substances such as strong acids and alkalis, avoids corrosion damage to the reaction device, and is relatively friendly to the environment.

[0043] 5. The present invention uses an iron anode to flocculate organic matter. During the consumption of the iron anode, FeOOH and Fe 3 O 4 They all have photocatalytic properties and can react with flocculated organic matter under light to degrade it into small molecules or even CO 2 and H 2 O. DETAILED DESCRIPTION

[0044] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] Example 1

[0046] This embodiment provides a treatment process for recovering isopropyl bromide from bromine-containing wastewater, comprising the following steps:

[0047] The bromine-containing wastewater treated in this example is oxadiazon etherification wastewater, with a bromide ion content of 5300 mg / L and a COD content of 1535 mg / L. The oxadiazon etherification wastewater is filtered through a coarse mesh with a gap of 10 mm and a fine mesh with a gap of 2 mm, and then enters the flotation device to remove small suspended particles, and then enters the buffer tank.

[0048] This embodiment uses iron and graphite as dual anodes, graphite as cathode, and the ion exchange membrane is asbestos diaphragm.

[0049] First, 600 mL of pretreated oxadiazon etherification wastewater was measured and added into a sealed three-chamber ion exchange membrane electrolyzer. The electrolysis reaction was carried out at a temperature of 50°C and a voltage of 1.8 V for 24 hours. After the reaction, oxygen was collected above the graphite anode and hydrogen was collected from above the graphite cathode. At a temperature of 30°C and a pressure of 0.2 MPa, filtration was carried out using a Koch KOCH-MP8081-102 ultrafiltration membrane. 200 mL of carbon tetrachloride and the bromine-containing wastewater separated by ultrafiltration were stirred at 400 r / min for 10 minutes to extract bromine. The extract phase and the aqueous phase were allowed to stand to separate, and bromine was obtained by distillation at 60°C for 30 minutes.

[0050] Mix 12 g of 99% pure sulfur and 155 g of recovered bromine at 80°C for 30 min, add 160 mL of 95% by volume isopropanol aqueous solution, control the temperature at 75°C to react for 1 h, and obtain isopropyl bromide.

[0051] Example 2

[0052] This embodiment provides a treatment process for recovering isopropyl bromide from bromine-containing wastewater, comprising the following steps:

[0053] The bromine-containing wastewater treated in this example is oxadiazon etherification wastewater, with a bromide ion content of 5300 mg / L and a COD content of 1535 mg / L. The oxadiazon etherification wastewater is filtered through a coarse mesh with a gap of 10 mm and a fine mesh with a gap of 2 mm, and then enters the flotation device to remove small suspended particles, and then enters the buffer tank.

[0054] In this embodiment, iron and graphite are used as dual anodes, graphite is used as cathode, and the ion exchange membrane is a perfluorinated cationic membrane.

[0055] First, 1200 mL of pretreated oxadiazon etherification wastewater was measured and added into a sealed three-chamber ion exchange membrane electrolyzer. The electrolysis reaction was carried out at a temperature of 50°C and a voltage of 3V for 18 hours. After the reaction, oxygen was collected above the graphite anode and hydrogen was collected from above the graphite cathode. At a temperature of 30°C and a pressure of 0.2 MPa, filtration was carried out using a Koch KOCH-MP8081-102 ultrafiltration membrane. 400 mL of p-xylene and the bromine-containing wastewater separated by ultrafiltration were stirred at 400 r / min for 10 minutes to extract bromine. The extract phase and the aqueous phase were allowed to stand to separate, and bromine was obtained by distillation at 60°C for 30 minutes.

[0056] Mix 12 g of 99% pure sulfur and 155 g of recovered bromine at 80° C. for 30 min, drop 160 mL of 95% by volume isopropanol aqueous solution into it, control the temperature at 75° C. to react for 1.5 h to obtain isopropyl bromide.

[0057] Example 3

[0058] This embodiment provides a treatment process for recovering isopropyl bromide from bromine-containing wastewater, comprising the following steps:

[0059] The bromine-containing wastewater treated in this example is oxadiazon etherification wastewater, with a bromide ion content of 5300 mg / L and a COD content of 1535 mg / L. The oxadiazon etherification wastewater is filtered through a coarse mesh with a gap of 10 mm and a fine mesh with a gap of 2 mm, and then enters the flotation device to remove small suspended particles, and then enters the buffer tank.

[0060] In this embodiment, iron and graphite are used as dual anodes, graphite is used as cathode, and the ion exchange membrane is a perfluorinated anion membrane.

[0061] First, 1800 mL of pretreated oxadiazon etherification wastewater was measured and added into a sealed three-chamber ion exchange membrane electrolyzer. The electrolysis reaction was carried out for 12 hours at a temperature of 50°C and a voltage of 4.5V. After the reaction, oxygen was collected above the graphite anode and hydrogen was collected from above the graphite cathode. At a temperature of 30°C and a pressure of 0.2Mpa, filtration was carried out using a Koch KOCH-MP8081-102 ultrafiltration membrane. 600 mL of carbon tetrachloride and the bromine-containing wastewater separated by ultrafiltration were stirred at 400r / min for 10 minutes to extract bromine, the extract phase and the aqueous phase were allowed to stand to separate, and the recovered bromine was obtained by distillation at 60°C for 30 minutes.

[0062] Mix 12 g of 99% pure sulfur and 155 g of recovered bromine at 80°C for 30 min, drop 160 mL of 95% by volume isopropanol aqueous solution into it, control the temperature at 75°C to react for 2 h, and obtain isopropyl bromide.

[0063] Comparative Example 1

[0064] This embodiment provides a treatment process for recovering isopropyl bromide from bromine-containing wastewater, comprising the following steps:

[0065] Compared with Example 1, on the basis of Example 1, iron and graphite as dual anodes are replaced by aluminum and graphite as dual anodes, and the remaining raw materials and preparation steps are the same as those in Example 1.

[0066] Comparative Example 2

[0067] This embodiment provides a treatment process for recovering isopropyl bromide from bromine-containing wastewater, comprising the following steps:

[0068] Compared with Example 1, on the basis of Example 1, iron and graphite as dual anodes are replaced by two graphites as anodes, and the remaining raw materials and preparation steps are the same as those in Example 1.

[0069] The performance tests were performed on the isopropyl bromide prepared in Examples 1 to 3 and Comparative Examples 1 to 2.

[0070] The yield of isopropyl bromide was calculated according to the amount of isopropyl alcohol solution, according to n (isopropyl alcohol): n (isopropyl bromide) = 1:1.

[0071] The purity of isopropyl bromide was tested by gas chromatography, and the specific method was as follows: gas phase was split flow inlet; chromatographic column: 60m×0.32mm×1.8μm, SH-Rtx-624; column temperature: 40℃; inlet temperature: 180℃; carrier gas (hydrogen) flow rate: 30mL / min;

[0072] The method for measuring COD in bromine-containing wastewater is: potassium dichromate method, adding excess potassium dichromate to the bromine-containing wastewater solution, generating hexavalent chromium by oxidizing organic matter, and then converting hexavalent chromium into trivalent chromium, and calculating the COD value in the solution by measuring the absorbance value, and further calculating the COD removal rate in the bromine-containing wastewater. The results are shown in Table 1:

[0073]

[0074] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Yield of isopropyl bromide (%) 98.31 98.52 98.78 98.31 98.64 Purity of isopropyl bromide (%) 99.61 99.72 99.81 99.29 95.81 Removal rate of COD in bromine-containing wastewater (%) 98.1 98.3 98.8 95.8 62.1

[0075] As can be seen from Table 1, it can be seen from Examples 1-3 that the yield of isopropyl bromide is greater than 98.31%, the purity of isopropyl bromide is greater than 99.61%, and the COD removal rate in bromine-containing wastewater is greater than 98.1%. It can be seen from Comparative Examples 1-2 that the difference in the yield of isopropyl bromide is not large, but there is a difference in the purity of isopropyl bromide, and there is a large difference in the removal rate of COD in bromine-containing wastewater. This is because after the introduction of the iron and graphite dual anodes, the organic matter in the bromine-containing wastewater can be electrocoagulated, and the generated FeOOH and Fe 3 O 4It also has photocatalytic properties and can degrade organic matter in bromine-containing wastewater. Comparative Example 1 uses a dual anode of aluminum and graphite, which can only play a flocculation role but has no degradation properties. Comparative Example 2 uses two graphites as anodes, which improves the electrolysis yield, but has poor effects on COD removal rate and purity of isopropyl bromide in bromine-containing wastewater.

[0076] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0077] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for recovering isopropyl bromide from bromine-containing wastewater, characterized in that: The following steps are involved: Step (1): the pretreated bromine-containing wastewater is passed into an electrolysis device to electrolyze the bromine-containing wastewater; Step (2): collecting oxygen generated in the anode region and hydrogen generated in the cathode region, filtering and separating the bromine-containing wastewater after electrolysis through an ultrafiltration system to obtain a filtrate, adding an extractant to the filtrate and stirring and mixing, and recovering bromine from the extract phase; Step (3): mixing sulfur and recovered bromine at 80° C. for 30 min, then dropping isopropanol solution, controlling the temperature at 75° C. to react for 1-2 h to obtain isopropyl bromide; Wherein, the electrolysis device in step (1) is an ion exchange membrane electrolyzer, which is mainly composed of an anode, a cathode, an ion exchange membrane, and an electrolyzer frame.

2. A process for recovering isopropyl bromide from bromine-containing wastewater according to claim 1, characterized in that: The anode is composed of an iron anode and a graphite anode.

3. A process for recovering isopropyl bromide from bromine-containing wastewater according to claim 1, characterized in that: The electrolysis adopts direct current electrolysis, the voltage between the anode and the cathode is 1.8-4.5V, the time is 12-24h, and the temperature is 50°C.

4. A process for recovering isopropyl bromide from bromine-containing wastewater according to claim 1, characterized in that: The ion exchange membrane electrolyzer is a three-chamber ion exchange membrane electrolyzer, and each zone allows liquid electrolyte and gas phase to flow freely through.

5. A process for recovering isopropyl bromide from bromine-containing wastewater according to claim 1, characterized in that: The ion exchange membrane electrolyzer is one of an inert asbestos membrane, a perfluorinated cation membrane or a perfluorinated anion membrane.

6. A process for recovering isopropyl bromide from bromine-containing wastewater according to claim 1, characterized in that: The cathode is a graphite cathode.

7. A process for recovering isopropyl bromide from bromine-containing wastewater according to claim 1, characterized in that: The bromine-containing wastewater is oxadiazon etherification wastewater.

8. A process for recovering isopropyl bromide from bromine-containing wastewater according to claim 1, characterized in that: The extractant is carbon tetrachloride or p-xylene.