Bromine separation and purification method

Abstract

The invention belongs to the technical field of chemical engineering, and particularly relates to a bromine separation and purification method which comprises the following steps: mixing rhodococcus erythropolis and bacillus cereus, and inoculating a culture medium with the mixture to prepare a bacterial suspension; adding the bacterial suspension into the bromine-containing wastewater in proportion, performing multi-stage filtration on the bromine-containing wastewater subjected to biological treatment, and performing electrodialysis concentration to obtain a concentrated solution; transferring the concentrated solution to a reaction kettle, adding a catalyst and a trapping agent, and dynamically introducing liquid-phase ozone in a gradient manner to obtain an oxidized solution; the oxidation liquid is pumped into a gas stripping tower for gas stripping, and generated bromine vapor is introduced into an adsorption tower and adsorbed by filler in the adsorption tower; and transferring the filler to a desorption tank, condensing bromine vapor generated in the desorption process, feeding the condensed bromine vapor into a trapping tank, and condensing and collecting the condensed bromine vapor to obtain high-purity liquid bromine. The method solves the problems of chlorine escape risk, organic solvent residue, low bromine yield and the like in the prior art.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical engineering, and particularly relates to a method for separating and purifying bromine. Background Art

[0002] Bromine is an important chemical raw material, which is widely used in the preparation of inorganic bromides, bromates and bromine-containing organic compounds, and has important applications in industries such as pharmaceuticals, pesticides, and dyes. During the preparation of aromatic organic bromides, a large amount of industrial wastewater containing bromides such as hydrobromic acid, sodium bromide, and potassium bromide is generated. If bromine can be effectively extracted from these wastewaters, the production cost will be significantly reduced, and significant economic and social benefits will be brought.

[0003] However, existing bromine purification technologies, such as chlorine oxidation method and extraction-distillation method, have many deficiencies. The chlorine oxidation method has potential safety hazards of chlorine leakage, and during the reaction process, bromine is prone to reversible hydrolysis reaction with water to generate hypobromous acid and hydrobromic acid, resulting in a decrease in bromine yield and increasing the difficulty of subsequent separation and purification. The extraction-distillation method has problems such as high energy consumption and residual organic solvents. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for separating and purifying bromine in view of the deficiencies of the prior art, so as to solve problems such as the risk of chlorine leakage, residual organic solvents, and low bromine yield existing in the prior art. To achieve the above purpose, the present invention provides a method for separating and purifying bromine, which includes the following steps: 1) Mix Rhodococcus erythropolis and Bacillus cereus in a ratio of viable cell count (3.8 - 4.5):1, inoculate them into a culture medium, centrifuge and collect the bacterial cells after culturing for 48 hours, and prepare a bacterial suspension; 2) The bromine-containing wastewater enters a bioreactor after filtration, and dilute hydrochloric acid solution or sodium bicarbonate solution is added to adjust the pH of the bromine-containing wastewater to 6.5 - 7.5. The bacterial suspension is added in an amount of 30% - 45% of the volume of the bromine-containing wastewater, and it is treated for 24 hours under the combined action of microporous aeration and mechanical stirring at 35°C; 3) After the bromine-containing wastewater after biological treatment is subjected to multi-stage filtration, it is concentrated by electrodialysis to a Br - concentration ≥ 0.5 g / L to obtain a concentrated solution; 4) Transfer the concentrated solution to a reaction kettle, slowly add sulfuric acid to adjust the pH to 2.5 - 4.5, control the temperature ≤ 40°C, and stir for 30 minutes; 5) After the stirring ends, add 1.5 - 3 wt% catalyst and 0.3 - 1.2 wt% scavenger, and introduce liquid-phase ozone dynamically in a gradient manner, and carry out oxidation at 20°C and a pressure of 0.1 MPa to obtain an oxidation solution; 6) Pump the oxidation solution into a stripping tower for stripping, and the generated bromine vapor is introduced into an adsorption tower and adsorbed by the packing inside the adsorption tower; 7) Transfer the packing of the adsorption tower to the desorption tank. The bromine vapor generated during the desorption process enters the capture tank after condensation, and high-purity liquid bromine is obtained after condensation and collection.

[0005] Preferably, the packing of the adsorption tower is a COF-TzDa adsorbent.

[0006] Preferably, the catalyst is an FeCl3 / CuBr2 composite catalyst.

[0007] Preferably, the mass ratio of FeCl3 to CuBr2 is 3:1.

[0008] Preferably, the capturant is sodium aminated lignosulfonate.

[0009] Preferably, the mass fraction of sulfuric acid is 98%.

[0010] Preferably, the viable count of the bacterial suspension ≥ 1×10 6 CFU / mL.

[0011] Preferably, the stripping temperature of the stripping tower is 50°C and the gas flow rate is 0.8 L / min.

[0012] After adopting the above technical solution, the beneficial effects of the present invention are as follows: The present invention not only solves the problems of chlorine gas escape risk, organic solvent residue, and low bromine yield in the existing bromine purification technology, but also shows significant advantages in terms of environmental protection and safety, yield improvement, purity optimization, and industrialization potential, providing a new technical path for the efficient and green preparation of bromine. Detailed Embodiments

[0013] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the objectives, technical solutions, and advantages of the present invention clearer, the following will further describe the present invention in detail with reference to specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be implemented without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present invention by showing examples of the present invention.

[0014] The present invention provides a method for separating and purifying bromine, and the following are its specific steps and technical details.

[0015] Step 1. Bacterial community construction Use a mixed flora of Rhodococcus erythropolis (LSSE8-1, preservation number CGMCC NO.0643) and Bacillus cereus (ATCC2, preservation number CICC NO.10352). Inoculate it into LB liquid medium and culture it with shaking at a constant temperature of 37°C for 48 hours to ensure that the bacteria reach the end of the logarithmic growth phase and maximize the viable cell density.

[0016] The proportionally mixed strains optimize the treatment efficiency of the flora for bromine-containing wastewater through synergy. Rhodococcus erythropolis metabolizes and secretes dehalogenases (such as hydrolytic halohydrolases, oxidative dehalogenases, etc.), which can break the C-Br bond in halogenated hydrocarbons (such as bromobenzene, bromomethane, etc.) to generate Br - and non-toxic hydrocarbons. Bacillus cereus metabolizes and secretes esterase and amidase to degrade bromine-containing ester compounds (such as bromophthalate), and releases Br through hydrolysis reaction - and generates small molecule organic acids for the metabolism and utilization of the flora. Functional groups such as carboxyl groups and phosphate groups on the surface of the flora adsorb heavy metal ions (such as Mg 2+ 、Fe 3+ etc.) through electrostatic adsorption, reduce the interference of heavy metals on subsequent oxidation reactions, and at the same time promote the enrichment of Br - .

[0017] After the culture is completed, centrifuge at a high speed of 10000 r / min for 20 minutes to remove impurities in the culture solution and concentrate the bacteria. Resuspend the centrifuged bacteria in sterile normal saline to prepare a bacterial suspension with a viable bacteria count ≥ 1×10 6 CFU / mL. This concentration range can balance the activity of the flora and the wastewater treatment efficiency, and avoid waste of resources caused by excessive bacteria.

[0018] Step 2. Biological pretreatment The bromine-containing wastewater enters the bioreactor after filtration, and the pH of the bromine-containing wastewater is adjusted to 6.5 - 7.5 by adding dilute hydrochloric acid solution or sodium bicarbonate solution to maintain the efficient metabolism of the strains. Add a certain proportion of the bacterial suspension according to the volume of the bromine-containing wastewater, and treat it for 24 hours under the combined action of microporous aeration and mechanical stirring (180 rpm) at 35°C.

[0019] Step 3. Electrodialysis concentration After the bromine-containing wastewater treated biologically is filtered through multiple stages, it is concentrated to a Br - concentration ≥ 0.5 g / L by bipolar membrane electrodialysis to obtain the concentrated solution.

[0020] Under the action of the electric field, Br in the wastewater - migrates directionally to the anode, and metal ions such as Na + migrate directionally to the cathode. Br - enters the acid chamber (anode side) through the anion exchange membrane and combines with H +Combined to generate HBr. HBr is a strong acid and completely dissociates into H + and Br - , so the acid chamber actually exists in the form of high-concentration Br - and H + . Br - continually accumulates in the anode chamber, providing a high-concentration substrate for subsequent oxidation reactions.

[0021] Bipolar membrane electrodialysis can not only concentrate Br - , but also achieve a certain degree of purification, providing high-quality raw materials for subsequent oxidation to prepare Br2. The anion exchange membrane allows monovalent anions such as Br - to pass through, reducing the impurity content; the cation exchange membrane restricts the migration direction of cations, reducing the contamination of metal ions (such as Ca 2+ , Mg 2+ ) to the products in the acid chamber.

[0022] Step 4. Oxidation reaction Transfer the concentrated solution to a reaction kettle, slowly add 98% sulfuric acid (mass fraction) to adjust the pH to 2.5 - 4.5, control the temperature ≤ 40°C, and stir for 30 minutes. After stirring, add 1.5 - 3 wt% catalyst and 0.3 - 1.2 wt% scavenger, and dynamically and gradiently introduce liquid-phase ozone, and carry out oxidation at 20°C and 0.1 MPa pressure to obtain an oxidation solution.

[0023] The dynamic gradient adjustment of liquid-phase ozone includes the following stages: 1) 0 - 30 minutes, continuously introduce liquid-phase ozone with a concentration of 180 mg / L to rapidly oxidize Br - to HBrO, using the initial high-activity stage to preferentially form the Br2 path, and the total ozone amount is 0.6 times the theoretical molar amount (based on the molar amount of Br - in the concentrated solution); 2) 30 - 120 minutes, continuously introduce liquid-phase ozone with a concentration of 120 mg / L, and the total amount is 0.4 times the theoretical amount, reducing the consumption of ineffective ozone; 3) 120 - 150 minutes, pulse-introduce liquid-phase ozone with a concentration of 100 mg / L, and the pulse frequency is to introduce for 30 seconds every 10 minutes to maintain the oxidation demand of the terminal reaction.

[0024] Ozone molecules (O3) decompose under acidic conditions to generate hydroxyl radicals and oxygen molecules, and the hydroxyl radicals further oxidize Br - , generating hypobromous acid (HBrO), and the reaction equation is as follows:

[0025] Subsequently, HBrO is further oxidized by O3 to Br2, and the reaction equation is as follows:

[0026] The catalyst is a FeCl3 / CuBr2 composite catalyst with a mass ratio of FeCl3 to CuBr2 of 3:1, which is supported on a molecular sieve carrier. Fe 3+ reacts with O3 to generate Fe 2+ and hydroxyl radicals. Fe 2+ is re-oxidized by O3 to Fe 3+ , forming a cyclic catalytic system and improving the utilization rate of O3. The synergistic effect of Fe 3+ / Cu 2+ preferentially catalyzes the direct oxidation path of O3 (Br - →HBrO→Br2), rather than the indirect path of generating BrO3 - , inhibiting the generation of harmful by-products.

[0027] Sodium aminated lignosulfonate is used as a scavenger to adsorb intermediate products (such as HBrO, BrO - ) through electrostatic interaction, preventing them from being further oxidized to form bromate (BrO3 - ). Sodium aminated lignosulfonate can also act as a free radical scavenger to capture hydroxyl radicals or superoxide radicals generated in the reaction, avoiding non-selective oxidation caused by excessive O3 (such as the generation of BrO3 - ), and maintaining the efficient conversion of Br - →Br2.

[0028] Step Five: Stripping and Adsorption Pump the oxidized mixed solution into a ceramic corrugated plate packing tower, control the stripping temperature at 50°C, and the air flow rate at 0.8 L / min. Air is blown in from the bottom of the tower and contacts the mixed solution countercurrently. The Br2 vapor rises to the top of the tower with the air flow, and the stripping residue liquid returns to the oxidation step for cyclic treatment. The outlet of the top of the tower is connected to the bottom of the adsorption tower through a heat-insulated pipeline to avoid the condensation of Br2 vapor during transportation. The bromine vapor is introduced into the bottom of the adsorption tower at a flow rate of 0.8 L / min, control the adsorption temperature at 25 - 30°C, and the bed pressure drop ≤ 5 kPa. When the Br2 concentration at the outlet ≥ 5% of the inlet concentration, it is regarded as breakthrough (indicating that the target substance can no longer be effectively adsorbed).

[0029] The adsorption bed of the adsorption tower is filled with COF-TzDa as the adsorbent, and its preparation includes the following steps: 1) According to a molar ratio of 1:1, dissolve 2,5-dimethoxyterephthalaldehyde and 4,4',4'',4'''-(pyrene-1,3,6,8-tetrayl)tetraaniline (CAS 1610471-69-6) in a mixed solvent of 1,3-dichlorobenzene / 1-butanol (volume ratio 3:1), with a solid-liquid ratio of 1:6 (g / mL). Transfer it to a high-pressure reactor and carry out a solvothermal reaction at 120 °C for 72 hours to generate a black powdery alkyne-bridged COF (covalent organic framework material); 2) According to a solid-liquid mass ratio of 1:10 (g / mL), immerse the COF in a Na2S solution, stir at 50 °C for 12 hours, filter and wash with deionized water until neutral, and then dry in vacuum at 60 °C to obtain COF-TzDa modified with thioether bonds.

[0030] The thioether bonds in COF-TzDa contain lone pairs of electrons, and bromine vapor has electrophilicity. The lone pairs of electrons on the sulfur atom can interact with the empty orbitals in the bromine molecule to form S-Br chemical bonds. As a covalent organic framework material, COF-TzDa has a highly ordered porous structure and a large specific surface area, providing abundant adsorption sites for bromine vapor, enabling bromine molecules to fully contact and adsorb on the surface of COF-TzDa.

[0031] Step Six: Thermal Desorption Transfer the COF-TzDa filler after adsorption to a desorption tank and evacuate to ≤10 Pa. Heat the adsorption-saturated COF to 120 °C (heating rate 5 °C / min) under vacuum conditions and maintain for 30 minutes. The bromine vapor generated during the desorption process enters the collection tank after condensation, and high-purity liquid bromine is obtained after condensation and collection. The desorbed COF-TzDa filler is immersed in a 60% isopropyl alcohol aqueous solution (volume ratio 3:2) and ultrasonically cleaned for 20 minutes, and then dried at 60 °C for recycling.

[0032] To facilitate a further understanding of the present invention, several embodiments of the present invention are given below.

[0033] Example 1 This example provides a method for separating and purifying bromine, including the following steps: 1) Mix Rhodococcus erythropolis and Bacillus cereus according to the viable cell count of 3.8:1, inoculate them into a culture medium, centrifuge and collect the bacterial cells after culturing for 48 hours, and prepare a bacterial suspension; 2) The bromine-containing wastewater enters the bioreactor after filtration, add dilute hydrochloric acid solution or sodium bicarbonate solution to adjust the pH of the bromine-containing wastewater to 6.5 - 7.5, add the bacterial suspension according to 30% of the volume of the bromine-containing wastewater, and treat it for 24 hours under the synergistic action of microporous aeration and mechanical stirring at 35 °C; 3) After the bromine-containing wastewater after biological treatment is filtered through multiple stages, it is concentrated by electrodialysis to Br -The concentration is ≥ 0.5 g / L to obtain a concentrated solution; 4) Transfer the concentrated solution to a reaction kettle, slowly add sulfuric acid dropwise to adjust the pH to 2.5 - 4.5, control the temperature ≤ 40 °C, and stir for 30 minutes; 5) After the stirring ends, add 1.5 wt% FeCl3 / CuBr2 composite catalyst and 0.3 wt% aminated sodium lignosulfonate, dynamically introduce liquid-phase ozone in a gradient manner, and perform oxidation at 20 °C and 0.1 MPa pressure to obtain an oxidized solution; 6) Pump the oxidized solution into a stripping tower for stripping. The generated bromine vapor is introduced into an adsorption tower and adsorbed by the packing inside the adsorption tower; 7) Transfer the packing of the adsorption tower to a desorption tank. The bromine vapor generated during the desorption process enters the collection tank after condensation, and after condensation and collection, liquid bromine with a purity of 99.3% is obtained.

[0034] Example 2 This example provides a method for separating and purifying bromine, including the following steps: 1) Mix Rhodococcus erythropolis and Bacillus cereus in a live bacteria count ratio of 4:1, inoculate them into a culture medium, centrifuge and collect the bacterial cells after culturing for 48 hours, and prepare a bacterial suspension; 2) The bromine-containing wastewater enters a biological reactor after filtration. Add dilute hydrochloric acid solution or sodium bicarbonate solution to adjust the pH of the bromine-containing wastewater to 6.5 - 7.5, add the bacterial suspension according to 40% of the volume of the bromine-containing wastewater, and treat it for 24 hours under the combined action of microporous aeration and mechanical stirring at 35 °C; 3) After the bromine-containing wastewater after biological treatment is filtered through multiple stages, it is concentrated by electrodialysis to Br - The concentration is ≥ 0.5 g / L to obtain a concentrated solution; 4) Transfer the concentrated solution to a reaction kettle, slowly add sulfuric acid dropwise to adjust the pH to 2.5 - 4.5, control the temperature ≤ 40 °C, and stir for 30 minutes; 5) After the stirring ends, add 2 wt% FeCl3 / CuBr2 composite catalyst and 0.5 wt% aminated sodium lignosulfonate, dynamically introduce liquid-phase ozone in a gradient manner, and perform oxidation at 20 °C and 0.1 MPa pressure to obtain an oxidized solution; 6) Pump the oxidized solution into a stripping tower for stripping. The generated bromine vapor is introduced into an adsorption tower and adsorbed by the packing inside the adsorption tower; 7) Transfer the packing of the adsorption tower to a desorption tank. The bromine vapor generated during the desorption process enters the collection tank after condensation, and after condensation and collection, liquid bromine with a purity of 99.8% is obtained.

[0035] Example 3 This example provides a method for separating and purifying bromine, including the following steps: 1) Mix Rhodococcus erythropolis and Bacillus cereus at a viable cell count ratio of 4.5:1, inoculate them into a culture medium, centrifuge and collect the cells after culturing for 48 hours, and prepare a cell suspension; 2) The bromine-containing wastewater enters the bioreactor after filtration, add dilute hydrochloric acid solution or sodium bicarbonate solution to adjust the pH of the bromine-containing wastewater to 6.5 - 7.5, add the cell suspension according to 45% of the volume of the bromine-containing wastewater, and treat it for 24 hours under the combined action of micro-aeration and mechanical stirring at 35°C; 3) After multi-stage filtration of the bromine-containing wastewater after biological treatment, it is concentrated by electrodialysis to a Br - concentration ≥ 0.5 g / L to obtain a concentrated solution; 4) Transfer the concentrated solution to a reaction kettle, slowly add sulfuric acid to adjust the pH to 2.5 - 4.5, control the temperature ≤ 40°C, and stir for 30 minutes; 5) After the stirring ends, add 3 wt% FeCl3 / CuBr2 composite catalyst and 1.2 wt% aminated lignosulfonate, dynamically introduce liquid-phase ozone in a gradient manner, and carry out oxidation at 20°C and 0.1 MPa pressure to obtain an oxidation solution; 6) Pump the oxidation solution into a stripping tower for stripping, and the generated bromine vapor is introduced into an adsorption tower and adsorbed by the packing inside the adsorption tower; 7) Transfer the packing of the adsorption tower to a desorption tank, and the bromine vapor generated during the desorption process enters the capture tank after condensation, and is collected by condensation to obtain liquid bromine with a purity of 99.7%.

[0036] According to the embodiments of the present invention as described above, these embodiments do not describe all the details in detail, nor limit the invention to only the specific embodiments. Obviously, according to the above description, many modifications and changes can be made. The present specification selects and specifically describes these embodiments in order to better explain the principle and practical application of the present invention, so that those skilled in the art can make good use of the present invention and its modified use based on the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for separating and purifying bromine, characterized in that: The steps include: 1) Mix Rhodococcus erythropolis and Bacillus cereus at a ratio of 3.8-4.5:1, inoculate into the culture medium, collect the cells by centrifugation after culturing for 48 hours, and prepare a bacterial suspension; 2) After filtration, the bromine-containing wastewater enters the bioreactor, adds dilute hydrochloric acid solution or sodium bicarbonate solution to adjust the pH of the bromine-containing wastewater to 6.5-7.5, adds bacterial suspension at 30%-45% of the volume of the bromine-containing wastewater, and treats for 24 hours at 35°C under the synergistic effect of microporous aeration and mechanical stirring; 3) After biological treatment, the bromine-containing wastewater is filtered through multiple stages and concentrated to Br by electrodialysis. - Concentration ≥ 0.5 g / L, to obtain a concentrated solution; 4) Transfer the concentrated solution to the reactor, slowly add sulfuric acid to adjust the pH to 2.5-4.5, control the temperature to ≤40°C, and stir for 30 minutes; 5) After stirring, add 1.5-3wt% catalyst and 0.3-1.2wt% capture agent, introduce liquid ozone in a dynamic gradient, and perform oxidation at 20°C and 0.1MPa pressure to obtain an oxidized liquid; 6) The oxidizing liquid is pumped into the stripping tower for stripping, and the generated bromine vapor is introduced into the adsorption tower and adsorbed by the filler inside the adsorption tower; 7) The packing of the adsorption tower is transferred to the desorption tank. The bromine vapor generated during the desorption process is condensed and then enters the capture tank. After condensation and collection, high-purity liquid bromine is obtained.

2. The method for separating and purifying bromine according to claim 1, characterized in that: The filler of the adsorption tower is COF-TzDa adsorbent.

3. The method for separating and purifying bromine according to claim 1, wherein: The catalyst is a FeCl3 / CuBr2 composite catalyst.

4. The method for separating and purifying bromine according to claim 3, wherein: The mass ratio of the FeCl3 to CuBr2 is 3:

1.

5. The method for separating and purifying bromine according to claim 1, wherein: The capture agent is aminated sodium lignin sulfonate.

6. The method for separating and purifying bromine according to claim 1, wherein: The mass fraction of the sulfuric acid is 98%.

7. The method for separating and purifying bromine according to claim 1, wherein: The number of viable bacteria in the bacterial suspension is ≥ 1×10 6 CFU / mL.

8. The method for separating and purifying bromine according to claim 1, wherein: The stripping temperature of the stripping tower is 50° C., and the gas flow rate is 0.8 L / min.

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