A method for separating and purifying bromine

Abstract

The present invention belongs to the field of chemical technology and specifically relates to a method for separating and purifying bromine, comprising the following steps: mixing Rhodococcus erythropolis and Bacillus cereus, inoculating the mixture into a culture medium, and preparing a bacterial suspension; adding the bacterial suspension to bromine-containing wastewater in proportion, subjecting the biologically treated bromine-containing wastewater to multi-stage filtration and electrodialysis concentration to obtain a concentrated solution; transferring the concentrated solution to a reactor, adding a catalyst and a capture agent, and dynamically introducing liquid ozone to obtain an oxidized solution; pumping the oxidized 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; transferring the packing to a desorption tank, and the bromine vapor generated during the desorption process is condensed and then enters a capture tank, where it is collected by condensation to obtain high-purity liquid bromine. This method solves the problems of chlorine gas escape risk, residual organic solvents, and low bromine yield in the prior art.

Description

Technical Field

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

[0002] Bromine is an important chemical raw material, widely used in the preparation of inorganic bromides, bromates, and bromine-containing organic compounds. It has significant applications in the pharmaceutical, pesticide, and dye industries. The preparation of aromatic organic bromides produces large amounts of industrial wastewater containing bromides such as hydrobromic acid, sodium bromide, and potassium bromide. Effectively extracting bromine from this wastewater would significantly reduce production costs and bring significant economic and social benefits.

[0003] However, existing bromine purification technologies, such as chlorine oxidation and extraction-distillation, have numerous drawbacks. Chlorine oxidation poses a safety hazard due to chlorine gas leakage, and bromine readily undergoes reversible hydrolysis with water during the reaction, producing hypobromous acid and hydrobromic acid. This reduces bromine yield and increases the difficulty of subsequent separation and purification. Extraction-distillation also suffers from high energy consumption and residual organic solvents. Summary of the Invention

[0004] The object of the present invention is to provide a method for separating and purifying bromine in view of the deficiencies in the prior art, so as to solve the problems of chlorine gas leakage risk, residual organic solvent and low bromine yield in the prior art. In order to achieve the above object, the present invention provides a method for separating and purifying bromine, comprising the following steps:

[0005] 1) Mix Rhodococcus erythropolis and Bacillus cereus at a viable cell count ratio of 3.8-4.5:1, inoculate into culture medium, culture for 48 hours, collect the cells by centrifugation, and prepare a bacterial suspension;

[0006] 2) After filtration, the bromine-containing wastewater enters the bioreactor, where dilute hydrochloric acid solution or sodium bicarbonate solution is added to adjust the pH of the bromine-containing wastewater to 6.5-7.5. Bacterial suspension is added at 30%-45% of the volume of the bromine-containing wastewater, and the treatment is carried out for 24 hours at 35°C under the synergistic effect of microporous aeration and mechanical stirring;

[0007] 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 concentrated solution;

[0008] 4) Transfer the concentrated solution to a 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;

[0009] 5) After stirring, add 1.5-3 wt% of catalyst and 0.3-1.2 wt% of scavenger, introduce liquid ozone in a dynamic gradient, and perform oxidation at 20°C and 0.1 MPa pressure to obtain an oxidized liquid;

[0010] 6) The oxidizing liquid is pumped into the stripping tower for stripping. The generated bromine vapor is introduced into the adsorption tower and adsorbed by the packing inside the adsorption tower;

[0011] 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. It is condensed and collected to obtain high-purity liquid bromine.

[0012] Preferably, the filler of the adsorption tower is COF-TzDa adsorbent.

[0013] Preferably, the catalyst is a FeCl3 / CuBr2 composite catalyst.

[0014] Preferably, the mass ratio of FeCl3 to CuBr2 is 3:1.

[0015] Preferably, the capture agent is aminated sodium lignin sulfonate.

[0016] Preferably, the mass fraction of the sulfuric acid is 98%.

[0017] Preferably, the viable bacteria count of the bacterial suspension is ≥1×10 6 CFU / mL.

[0018] Preferably, the stripping temperature of the stripping tower is 50° C. and the gas flow rate is 0.8 L / min.

[0019] After adopting the above technical solution, the beneficial effects of the present invention are:

[0020] The present invention not only solves the problems of chlorine gas leakage risk, organic solvent residue and low bromine yield in existing bromine purification technologies, but also demonstrates significant advantages in 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 DESCRIPTION

[0021] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with 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 the need for some of these specific details. The following description of the embodiments is merely to provide a better understanding of the present invention by illustrating examples of the present invention.

[0022] The present invention provides a method for separating and purifying bromine. The specific steps and technical details are as follows.

[0023] Step 1: Bacterial community construction

[0024] A mixed bacterial population of Rhodococcus erythropolis (LSSE8-1, deposit number CGMCC NO.0643) and Bacillus cereus (ATCC2, deposit number CICC NO.10352) was inoculated into LB liquid culture medium and cultured with shaking at a constant temperature of 37°C for 48 hours to ensure that the bacteria reached the end of the logarithmic growth phase and to maximize the bacterial density.

[0025] The mixed bacterial species in the right proportions optimize the bacterial community's treatment efficiency for bromine-containing wastewater through synergistic action. Rhodococcus erythropolis metabolizes and secretes dehalogenases (such as hydrolytic halogen hydrolases, oxidase-type dehalogenases, etc.), which can break the C-Br bond in halogenated hydrocarbons (such as bromobenzene, methyl bromide, etc.) to generate Br - Bacillus cereus metabolizes and secretes esterases and amidases to degrade bromine-containing ester compounds (such as brominated phthalates) and release Br through hydrolysis. - , and generate small molecular organic acids for bacterial metabolism. The carboxyl and phosphate groups on the surface of the bacterial community absorb heavy metal ions (such as Mg) through electrostatic adsorption. 2+ 、Fe 3+ etc.), reducing the interference of heavy metals on subsequent oxidation reactions and promoting Br - enrichment.

[0026] After the culture is completed, high-speed centrifugation at 10,000 r / min for 20 minutes is used to remove impurities in the culture medium and concentrate the bacteria. The centrifuged bacteria are resuspended in sterile physiological saline and the viable cell count is ≥1×10 6 CFU / mL bacterial suspension. This concentration range can balance bacterial activity and wastewater treatment efficiency, avoiding excessive bacterial growth and waste of resources.

[0027] Step 2: Biological pretreatment

[0028] After filtration, the bromine-containing wastewater enters the bioreactor. Dilute hydrochloric acid or sodium bicarbonate solution is added to adjust the pH of the bromine-containing wastewater to 6.5-7.5 to maintain efficient bacterial metabolism. A certain proportion of bacterial suspension is added according to the volume of the bromine-containing wastewater. The treatment is carried out for 24 hours at 35°C, with microporous aeration and mechanical stirring (180 rpm).

[0029] Step 3: Electrodialysis Concentration

[0030] After biological treatment, the bromine-containing wastewater is filtered through multiple stages and concentrated to Br using bipolar membrane electrodialysis. - The concentration is ≥0.5g / L, and a concentrated solution is obtained.

[0031] Under the action of electric field, Br in wastewater - Directed migration toward the anode, Na +The metal ions migrate towards the cathode. - Enters the acid chamber (anode side) through the anion exchange membrane and reacts with H + Combine to form HBr. HBr is a strong acid and completely dissociates into H + and Br - , so the acid chamber is actually high concentration Br - and H + Br - It is continuously enriched in the anode chamber, providing high-concentration substrates for subsequent oxidation reactions.

[0032] Bipolar membrane electrodialysis can not only concentrate Br - , and can also achieve a certain degree of purification, providing high-quality raw materials for subsequent oxidation to prepare Br2. - The cation exchange membrane limits the migration direction of cations and reduces the amount of metal ions (such as Ca 2+ Mg 2+ ) contamination of acid chamber products.

[0033] Step 4: Oxidation reaction

[0034] Transfer the concentrated solution to a reactor and slowly add 98% sulfuric acid (mass fraction) dropwise to adjust the pH to 2.5-4.5. Control the temperature to ≤40°C and stir for 30 minutes. After stirring, add 1.5-3wt% catalyst and 0.3-1.2wt% scavenger. Dynamically introduce liquid ozone in a gradient manner. Oxidation is carried out at 20°C and 0.1MPa pressure to obtain an oxidized solution.

[0035] The dynamic gradient regulation of liquid ozone includes the following stages:

[0036] 1) For 0 to 30 minutes, continuously introduce liquid ozone at a concentration of 180 mg / L to rapidly oxidize Br - To HBrO, the Br2 path is formed preferentially during the initial high activity stage, and the total amount of ozone is the theoretical molar amount (based on the Br in the concentrated solution). - 0.6 times of the molar amount of

[0037] 2) For 30 to 120 minutes, continuously introduce liquid ozone at a concentration of 120 mg / L, with a total amount of 0.4 times the theoretical amount, to reduce ineffective ozone consumption;

[0038] 3) From 120 to 150 minutes, introduce liquid ozone at a concentration of 100 mg / L in a pulsed manner with a pulse frequency of 30 seconds every 10 minutes to maintain the oxidation requirements of the terminal reaction.

[0039] Ozone molecules (O3) decompose under acidic conditions to generate hydroxyl radicals and oxygen molecules, which further oxidize Br- , generating hypobromous acid (HBrO), the reaction equation is as follows:

[0040]

[0041] Subsequently, HBrO is further oxidized to Br2 by O3, and the reaction equation is as follows:

[0042]

[0043] The catalyst is a FeCl3 / CuBr2 composite catalyst, with a mass ratio of FeCl3 to CuBr2 of 3:1, loaded on a molecular sieve carrier. 3+ Reacts with O3 to form Fe 2+ and hydroxyl radicals, Fe 2+ Reoxidized by O3 to Fe 3+ , forming a circulating catalytic system and improving the utilization rate of O3. 3+ / Cu 2+ The synergistic effect of Br - →HBrO→Br2) instead of BrO3 - indirect pathway to inhibit the formation of harmful by-products.

[0044] Amine sodium lignin sulfonate is used as a capture agent to adsorb intermediate products (such as HBrO, BrO - ), to prevent further oxidation to form bromate (BrO3 - Amine sodium lignin sulfonate can also be used as a free radical scavenger to capture the hydroxyl radicals or superoxide radicals produced in the reaction, thus avoiding non-selective oxidation caused by excessive O3 (such as the generation of BrO3 - ), maintain Br - → Efficient conversion of Br2.

[0045] Step 5: Gas stripping and adsorption

[0046] The oxidized mixed liquor is pumped into a ceramic corrugated plate packed tower, with a controlled stripping temperature of 50°C and an air flow rate of 0.8 L / min. Air is introduced from the bottom of the tower, countercurrently contacting the mixed liquor. Br2 vapor rises with the airflow to the top of the tower, and the stripping residue is returned to the oxidation step for recycling. The top outlet is connected to the bottom of the adsorption tower via an insulated pipe to prevent condensation of Br2 vapor during transport. Bromine vapor is introduced from the bottom of the adsorption tower at a flow rate of 0.8 L / min, with an adsorption temperature of 25-30°C and a bed pressure drop of ≤5 kPa. Breakthrough (indicating the inability to effectively adsorb the target substance) is considered achieved when the outlet Br2 concentration is ≥5% of the inlet concentration.

[0047] The adsorption bed of the adsorption tower is filled with COF-TzDa as an adsorbent, and its preparation includes the following steps:

[0048] 1) 2,5-Dimethoxyterephthalaldehyde and 4,4',4'',4'''-(pyrene-1,3,6,8-tetraynyl)tetraphenylamine (CAS 1610471-69-6) were dissolved in a 1,3-dichlorobenzene / 1-butanol mixed solvent (volume ratio 3:1) at a solid-to-liquid ratio of 1:6 (g / mL) at a molar ratio of 1:1. The mixture was transferred to an autoclave and subjected to solvothermal reaction at 120°C for 72 hours to produce an alkyne-bridged COF (covalent organic framework) as a black powder.

[0049] 2) COF was immersed in Na2S solution at a solid-liquid mass ratio of 1:10 (g / mL), stirred at 50°C for 12 hours, filtered, washed with deionized water until neutral, and dried in a vacuum at 60°C to obtain thioether-modified COF-TzDa.

[0050] The sulfide bonds in COF-TzDa contain lone pairs of electrons, and bromine vapor is electrophilic. The lone pairs of sulfur atoms interact with the empty orbitals in the bromine molecules, forming S-Br chemical bonds. As a covalent organic framework, COF-TzDa possesses a highly ordered porous structure and a large surface area, providing abundant adsorption sites for bromine vapor, allowing bromine molecules to fully contact and adsorb on the COF-TzDa surface.

[0051] Step 6: Thermal desorption

[0052] The adsorbed COF-TzDa filler was transferred to a desorption tank and evacuated to ≤10 Pa. The saturated COF was heated to 120°C (at a heating rate of 5°C / min) under vacuum for 30 minutes. Bromine vapor generated during the desorption process condensed and entered a collection tank, where it was collected and condensed to yield high-purity liquid bromine. The desorbed COF-TzDa filler was ultrasonically cleaned in a 60% isopropanol aqueous solution (3:2 by volume) for 20 minutes, dried at 60°C, and then reused.

[0053] In order to facilitate further understanding of the present invention, several embodiments of the present invention are given below.

[0054] Example 1

[0055] This embodiment provides a method for separating and purifying bromine, comprising the following steps:

[0056] 1) Mix Rhodococcus erythropolis and Bacillus cereus at a viable count of 3.8:1, inoculate into culture medium, and after culturing for 48 hours, collect the cells by centrifugation to prepare a bacterial suspension;

[0057] 2) After filtration, the bromine-containing wastewater enters the bioreactor, where dilute hydrochloric acid solution or sodium bicarbonate solution is added to adjust the pH of the bromine-containing wastewater to 6.5-7.5. Bacterial suspension is added at 30% of the volume of the bromine-containing wastewater and treated at 35°C for 24 hours under the synergistic effect of microporous aeration and mechanical stirring;

[0058] 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 concentrated solution;

[0059] 4) Transfer the concentrated solution to a 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;

[0060] 5) After stirring, 1.5 wt% FeCl3 / CuBr2 composite catalyst and 0.3 wt% aminated sodium lignin sulfonate were added, and liquid ozone was introduced in a dynamic gradient to carry out oxidation at 20°C and 0.1 MPa pressure to obtain an oxidized liquid;

[0061] 6) The oxidizing liquid is pumped into the stripping tower for stripping. The generated bromine vapor is introduced into the adsorption tower and adsorbed by the packing inside the adsorption tower;

[0062] 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, liquid bromine with a purity of 99.3% is obtained.

[0063] Example 2

[0064] This embodiment provides a method for separating and purifying bromine, comprising the following steps:

[0065] 1) Mix Rhodococcus erythropolis and Bacillus cereus at a viable count of 4:1, inoculate into culture medium, and after culturing for 48 hours, collect the cells by centrifugation and prepare a bacterial suspension;

[0066] 2) After filtration, the bromine-containing wastewater enters the bioreactor, where dilute hydrochloric acid solution or sodium bicarbonate solution is added to adjust the pH of the bromine-containing wastewater to 6.5-7.5. Bacterial suspension is added at 40% of the volume of the bromine-containing wastewater and treated at 35°C for 24 hours under the synergistic effect of microporous aeration and mechanical stirring;

[0067] 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 concentrated solution;

[0068] 4) Transfer the concentrated solution to a 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;

[0069] 5) After stirring, add 2 wt% FeCl3 / CuBr2 composite catalyst and 0.5 wt% aminated sodium lignin sulfonate, and introduce liquid ozone in a dynamic gradient to carry out oxidation at 20°C and 0.1 MPa pressure to obtain an oxidized liquid;

[0070] 6) The oxidizing liquid is pumped into the stripping tower for stripping. The generated bromine vapor is introduced into the adsorption tower and adsorbed by the packing inside the adsorption tower;

[0071] 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, liquid bromine with a purity of 99.8% is obtained.

[0072] Example 3

[0073] This embodiment provides a method for separating and purifying bromine, comprising the following steps:

[0074] 1) Mix Rhodococcus erythropolis and Bacillus cereus at a viable count of 4.5:1, inoculate into culture medium, and after culturing for 48 hours, collect the cells by centrifugation to prepare a bacterial suspension;

[0075] 2) After filtration, the bromine-containing wastewater enters the bioreactor, where dilute hydrochloric acid solution or sodium bicarbonate solution is added to adjust the pH of the bromine-containing wastewater to 6.5-7.5. Bacterial suspension is added at 45% of the volume of the bromine-containing wastewater and treated at 35°C for 24 hours under the synergistic effect of microporous aeration and mechanical stirring;

[0076] 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 concentrated solution;

[0077] 4) Transfer the concentrated solution to a 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;

[0078] 5) After stirring, 3 wt% FeCl3 / CuBr2 composite catalyst and 1.2 wt% aminated sodium lignin sulfonate were added, and liquid ozone was introduced in a dynamic gradient to carry out oxidation at 20°C and 0.1 MPa pressure to obtain an oxidized liquid;

[0079] 6) The oxidizing liquid is pumped into the stripping tower for stripping. The generated bromine vapor is introduced into the adsorption tower and adsorbed by the packing inside the adsorption tower;

[0080] 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, liquid bromine with a purity of 99.7% is obtained.

[0081] While the embodiments of the present invention are described above, these embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to make good use of the present invention and its modifications and uses. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection 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 viable cell count ratio of 3.8-4.5:1, inoculate into culture medium, culture for 48 hours, collect the cells by centrifugation, and prepare a bacterial suspension; 2) After filtration, the bromine-containing wastewater enters the bioreactor, where dilute hydrochloric acid solution or sodium bicarbonate solution is added to adjust the pH of the bromine-containing wastewater to 6.5-7.

5. Bacterial suspension is added at 30%-45% of the volume of the bromine-containing wastewater, and the treatment is carried out 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 concentrated solution; 4) Transfer the concentrated solution to a 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, 1.5-3 wt% FeCl3 / CuBr2 composite catalyst and 0.3-1.2 wt% aminated sodium lignin sulfonate are added, with the mass ratio of FeCl3 to CuBr2 being 3:

1. Liquid phase ozone is introduced in a dynamic gradient, and oxidation is carried out at 20°C and 0.1 MPa pressure to obtain an oxidized liquid. The dynamic gradient adjustment of the liquid phase ozone includes the following stages: From 0 to 30 minutes, liquid ozone with a concentration of 180 mg / L is continuously introduced for rapid oxidation, and the Br2 path is preferentially formed in the initial high activity stage. The total amount of ozone is Br in the concentrated liquid. - 0.6 times the molar amount; For 30 to 120 minutes, continuously introduce liquid ozone with a concentration of 120 mg / L, the total amount of Br in the concentrated liquid - 0.4 times the molar weight, reducing invalid ozone consumption; From 120 to 150 minutes, liquid ozone with a concentration of 100 mg / L was pulsed in, with a pulse frequency of 30 seconds every 10 minutes to maintain the oxidation requirements of the terminal reaction; 6) The oxidizing liquid is pumped into a stripping tower for stripping, and the generated bromine vapor is introduced into an adsorption tower. The bromine vapor is introduced from the bottom of the adsorption tower at a flow rate of 0.8 L / min. The adsorption temperature is controlled at 25-30°C, the bed pressure drop is ≤5 kPa, and breakthrough is considered when the outlet Br2 concentration is ≥5% of the inlet concentration. The bromine vapor is adsorbed by the packing inside the adsorption tower, and the packing component of the adsorption tower is COF-TzDa adsorbent; 7) The adsorbed COF-TzDa filler is transferred to a desorption tank, evacuated to ≤10Pa, and heated to 120°C at a heating rate of 5°C / min. The bromine vapor generated during the desorption process is condensed and enters a capture tank to obtain high-purity liquid bromine.

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

3. 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.

4. 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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