Method for extracting bromine from bromine-containing water sample through electrooxidation

Abstract

The invention relates to a method for extracting bromine from a bromine-containing water sample through electrooxidation, in particular to a method for extracting bromine from brine containing various impurity ions, especially high-concentration Cl <-> ions and low-concentration Br <-> ions, which is mainly used for reducing the interference of the Cl <-> ions and improving the recovery rate of the Br <-> ions by selecting a proper oxidation potential. The process is used for optimally selecting the oxidation potential of bromine ions so as to achieve high-recovery-rate bromine extraction, and comprises the following steps: 1) adjusting the pH value of a bromine-containing water sample to be acidic; 2) carrying out electrochemical oxidation on the bromine-containing water sample subjected to acid adjustment to convert bromine ions into bromine gas; and 3) blowing the generated bromine gas to the absorption device through the aeration device. The hydrogen bromide solution is introduced to adjust the pH of the absorption product solution to be acidic, so that bromate is converted into bromide, and finally, a high-quality sodium bromide product can be obtained.

Description

Technical Field

[0001] The invention relates to a method for extracting bromine by electrochemical oxidation, and belongs to the technical field of extracting bromine by electrochemical oxidation. Background Art

[0002] Bromine, known as the "marine element", has strong oxidizing properties, active chemical properties and high flame retardant properties. It can be used for water disinfection and sterilization; active additives in industries such as rubber, synthetic fibers and dyes; as well as in the fields of construction, fuel and electronic products. In addition, bromine-containing compounds and their derivatives can be used as intermediates in organic synthesis and catalytic reactions. With the rapid development of my country's economy and science and technology, the demand for fine chemicals related to bromine and bromide has increased year by year. Therefore, on the one hand, it is necessary to find more sources of bromine production, and on the other hand, it is necessary to develop new bromine extraction technologies.

[0003] Bromine is mainly present as Br - Bromine ions exist in the ocean, salt lakes, and groundwater in dispersed forms. The content of bromide ions in seawater is low (about 65 mg / L). The bromine content in underground brine and salt lake brine is much higher than that in seawater (about 0.1-2 g / L), but the resources are scattered. In view of the above situation, the main methods for extracting bromine in industrial applications are air blowing and steam distillation. The air blowing method does not require high raw materials and is easy to automate, but its product purity is low, the equipment occupies a large area, and the safety and environmental protection costs are high. Steam distillation is suitable for extracting bromine in areas with dispersed brine resources. The process is simple and the raw material consumption is low, but the huge steam consumption leads to high separation costs, and the high temperature of steam easily causes bromine hydrolysis, thereby reducing the yield. Therefore, researchers have vigorously studied other new methods for extracting bromine, including solvent extraction, resin adsorption and membrane separation, but they are currently facing problems such as extractant pollution, short adsorbent life and poor selectivity, and membrane pollution, and cannot be industrialized in the short term.

[0004] In recent years, electrochemical oxidation bromine extraction technology has also been studied and promoted. This technology can be used to regulate Br - Electrochemical redox potential of conversion to Br2 The bromine extraction technology can obtain bromine with higher purity. It has the advantages of environmental protection, safety, low energy consumption and high value-added products. It can avoid the problems encountered in traditional bromine extraction methods, such as oxidant consumption, chemical pollution, high cost and high risk, and has great research significance and development prospects.

[0005] However, bromine-containing water samples contain many impurity ions, especially Cl - Existence The redox potential of Cl is not much different from that of bromine. Therefore, the potential regulation selection in the electrochemical oxidation method for bromine extraction should ensure that Br- can be quickly and completely oxidized to Br2, and at the same time ensure that Cl - It should not be oxidized to Cl2, and electrolysis of water should be avoided. And according to the different properties of water samples, the potential of electrochemical oxidation bromine extraction needs to be adjusted accordingly. To this end, this patent focuses on exploring the redox potential for obtaining the best bromine extraction rate when electrochemically oxidizing bromine from bromine-containing water samples of different properties. Summary of the invention

[0006] The technical problem to be solved by the present invention is that when bromine is extracted from a bromine-containing water sample containing impurity ions by electrochemical oxidation, the impurity ions compete with the oxidation of bromide ions on the surface of the working electrode, resulting in problems such as long reaction time, generation of by-products, and low bromine extraction efficiency.

[0007] A method for extracting bromine from a bromine-containing water sample by electro-oxidation comprises the following steps:

[0008] Step 1, adjusting the pH of the bromine-containing water sample to acidic;

[0009] Step 2, electrochemically oxidizing the acid-adjusted bromine-containing water sample to convert bromide ions into bromine gas;

[0010] Step 3, blowing the generated bromine gas to the absorption device through the aeration device.

[0011] Bromine-containing aqueous samples are any solution containing impurity ions and bromide ions.

[0012] The bromine-containing water sample is one of seawater, salt lake brine, underground brine, oil and gas field produced water, and mother liquor after seawater salt production.

[0013] Impurity ions in bromine-containing water samples include but are not limited to Li + 、Na + , K + , Ca 2+ Mg 2+ 、Co3 2- , Cl - .

[0014] The pH range of bromine-containing water samples after adjustment with acid is 2 to 5.

[0015] The pH range of bromine-containing water samples after adjustment with acid is 2 to 3.

[0016] During the electrochemical oxidation process, the cathode electrolyte is selected from one or a mixture of sodium chloride solution, sodium sulfate solution, and bromine-containing water sample (more preferably sodium sulfate solution), and the concentration range of the electrolyte is controlled to be 1g / L~10g / L (more preferably 1g / L~2g / L) or the conductivity range is 1mS / cm~10mS / cm (more preferably 1mS / cm~3mS / cm), and the adjusted pH range is 2~5 (more preferably 2~3).

[0017] The acid is an organic acid or an inorganic acid, selected from sulfuric acid, hydrochloric acid, nitric acid, citric acid, acetic acid or a mixture thereof (more preferably sulfuric acid).

[0018] The working electrode is one of a graphite electrode, a carbon electrode, a platinum electrode, and a titanium electrode (more preferably a graphite electrode); the reference electrode is one of an Ag / AgCl electrode, a saturated calomel electrode, and a mercurous sulfate electrode (more preferably an Ag / AgCl electrode); the counter electrode is one of a platinum electrode, a titanium electrode, a stainless steel electrode, and a graphite electrode (more preferably a titanium electrode).

[0019] The tail gas absorption liquid of the absorption device is one or a mixture of NaOH, KI, SO2, Na2CO3 or low-temperature bromine salt solution. The effective ion concentration of the absorption liquid is equal to or greater than Br in the bromine-containing water sample. - concentration.

[0020] The selected range of the electrical redox potential is 1.01V to 1.22V (vs. Ag / AgCl).

[0021] During the electrochemical oxidation process, the membrane between the electrodes is one of a proton exchange membrane, a cation exchange membrane and an anion exchange membrane.

[0022] Adjusting the pH of bromine-containing water samples to 2-5 with acid is helpful to avoid the generated Br2 being disproportionated to Br under neutral or alkaline conditions. - BrO - and BrO3 - , thereby ensuring that Br2 is blown into the absorption liquid as much as possible.

[0023] By regulating Br - The oxidation potential of Br in bromine-containing water samples - The ions are oxidized to Br2, and then the air pump is used to blow the Br2 in the water sample into the tail gas absorption liquid for collection. By comparing the bromine removal effects of different oxidation potentials, working electrodes of different areas, and different reaction times, the optimal experimental conditions for electro-oxidation bromine extraction are obtained, and data support is provided for future two-electrode system bromine extraction. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 : Installation diagram;

[0025] Figure 2 :flow chart. DETAILED DESCRIPTION

[0026] The present invention relates to a method for extracting bromine from a water sample containing impurity ions and Br-, specifically a method for extracting bromine from a water sample containing impurity ions and Br- safely, without pollution, with low energy consumption, and producing high value-added products, providing a new method for extracting bromine / removing bromine from brine, thereby solving the problems of high energy consumption and environmental pollution of traditional bromine extraction methods, and finding the optimal process conditions for electro-oxidation bromine extraction, thereby achieving the purpose of high bromine extraction rate. The present invention specifically relates to a method and device for electro-oxidation bromine extraction from a bromine-containing water sample, specifically to extracting bromine from a bromine-containing water sample. - Ions and other ions (including but not limited to Li + 、Na + , K + , Ca 2+ Mg 2+ 、Co3 2- , Cl - ) from water samples containing a variety of impurity ions, especially high concentrations of Cl - ions and low concentrations of Br - Extraction of bromine from brine containing ions is mainly achieved by selecting a suitable oxidation potential to reduce Cl - ions and increase the Br - Method for ion recovery rate. A process for optimizing the oxidation potential of bromide ions to achieve high recovery rate of bromine extraction, comprising: 1) adjusting the pH of a bromine-containing water sample to acidic; 2) electrochemically oxidizing the acidified bromine-containing water sample to convert bromide ions into bromine gas; 3) blowing the generated bromine gas to an absorption device through an aeration device. The present invention introduces a hydrogen bromide solution to adjust the pH of the absorption product solution to acidic, thereby converting bromate into bromide, and finally obtaining a high-quality sodium bromide product.

[0027] The ions to be extracted from the water sample in the present invention are bromide ions, and the raw material source of the water sample here can be concentrated seawater, salt lake brine, underground brine, underground brine in oil and gas fields, and mother liquor after seawater salt production. In my country, industrial production of extracting bromine from bromine-containing water samples mainly adopts air blowing method and steam distillation method, both of which require the introduction of chlorine to oxidize bromide ions into bromine gas, and the latter has a high concentration requirement for raw material bromine. Although both methods have been mature and industrialized, problems such as chemical agent pollution, high production cost and high energy consumption have not been solved for a long time.

[0028] The technical concept of this patent is: - Oxidation to Br 2In the process, electrochemical control of Br- oxidation is adopted to avoid the use of chlorine or other expensive oxidants to oxidize Br-, reducing the production cost of bromine extraction and environmental pollution. - The electro-oxidation potential ranges from 1.00V to 1.35V (vs. NHE), which greatly reduces the energy consumption of bromine extraction.

[0029] Example 1

[0030] The bromine-containing water sample used in this embodiment has a light yellow transparent liquid appearance, and the main ions contained therein are lithium ions, sodium ions, potassium ions, calcium ions, boron elements, bromide ions, chloride ions and carbonate ions, and the ion concentrations are 57.47 mg / L, 127.6 g / L, 1.663 g / L, 37.19 mg / L, 113.7 mg / L, 502 mg / L, 155.687 g / L and 2.411 g / L, respectively, and the pH is 13. The pH is adjusted to 2-3 with concentrated sulfuric acid, and then 200 mL is taken and placed in the anode chamber. The electrolyte in the cathode chamber is a sodium sulfate solution of the same pH and volume, and the conductivity range of the cathode liquid is 3 mS / cm-10 mS / cm. The working electrode is a graphite electrode, and the counter electrode is a titanium electrode. The size range of the two electrodes is from 1 cm*1 cm to 2 cm*3 cm. The reference electrode is an Ag / AgCl electrode. Electro-oxidation process parameters: Potential setting range is 1.01-1.22V (vs.Ag / AgCl), air aeration volume is 2-8mL / min, electro-oxidation ends after 6h, 8h or 10h, and aeration is stopped after 30min. Detect the bromide ion concentration in the tail liquid and the absorption liquid. When the size of the anode and cathode electrodes is 2cm*3cm, the oxidation potential is 1.2V, the aeration volume is 8mL / min, the cathode conductivity is 10mS / cm, the reaction time is 10h, and the bromine extraction rate is maintained between 62% and 69%.

[0031] Example 2

[0032] The bromine-containing water sample used in this embodiment is the same as that in Example 1. The experimental parameters are set according to the optimal experimental conditions in Example 1. 100 cycles of bromine extraction experiments are performed. The experimental results show that the cycle stability of the graphite electrode is good, and the bromine extraction rate is maintained at about 65%.

[0033] Comparative Example 1

[0034] The difference from Example 1 is that the main ions contained in the bromine-containing water sample used in this comparative example are lithium ion, sodium ion, potassium ion, calcium ion, magnesium ion, boron element, bromide ion, chloride ion and carbonate, and the ion concentrations are 102.9 mg / L, 150.7 g / L, 3.518 g / L, 39.7 mg / L, 41.1 mg / L, 172.3 mg / L, 750 mg / L, 168.9 g / L and 245 mg / L, respectively, and the pH is 8. The experimental parameters are set with reference to the optimal experimental conditions in Example 1, and the bromine extraction rate is between 66% and 72%.

[0035] Comparative Example 2

[0036] The difference from Example 1 is that the bromine extraction methods used in this comparative example are the reagent oxidation method and the two-electrode system bromine extraction method. The bromine extraction rates and costs of different bromine extraction methods are shown in the following table.

[0037] Table 1. Comparison of different bromine extraction methods

[0038]

Claims

1. A method for extracting bromine from bromine-containing water by electro-oxidation, characterized in that: The steps include: Step 1, adjusting the pH of the bromine-containing water sample to acidic; Step 2, electrochemically oxidizing the acid-adjusted bromine-containing water sample to convert bromide ions into bromine gas; Step 3, blowing the generated bromine gas to the absorption device through the aeration device.

2. The electro-oxidation method for extracting bromine from bromine-containing water sample according to claim 1, characterized in that: Bromine-containing aqueous samples are any solution containing impurity ions and bromide ions.

3. The method for extracting bromine from bromine-containing water sample by electro-oxidation according to claim 2, characterized in that: The bromine-containing water sample is one of seawater, salt lake brine, underground brine, oil and gas field produced water, and mother liquor after seawater salt production.

4. The electro-oxidation method for extracting bromine from bromine-containing water sample according to claim 3, characterized in that: Impurity ions in bromine-containing water samples include but are not limited to Li + 、Na + , K + , Ca 2+ Mg 2+ 、Co3 2- , Cl - .

5. The method for extracting bromine from bromine-containing water sample by electro-oxidation according to claim 1, characterized in that: The pH range of bromine-containing water samples after adjustment with acid is 2 to 5.

6. The method for extracting bromine from bromine-containing water sample by electro-oxidation according to claim 1, characterized in that: During the electrochemical oxidation process, the cathode electrolyte is selected from one or a mixture of sodium chloride solution, sodium sulfate solution, and bromine-containing water sample, and the concentration range of the electrolyte is controlled to be 1g / L~10g / L or the conductivity range is 1mS / cm~10mS / cm, and the adjusted pH range is 2~5.

7. The method for extracting bromine from bromine-containing water sample by electro-oxidation according to claim 1, characterized in that: The acid is an organic acid or an inorganic acid, selected from sulfuric acid, hydrochloric acid, nitric acid, citric acid, acetic acid or a mixture of several thereof.

8. The method for extracting bromine from bromine-containing water sample by electro-oxidation according to claim 1, characterized in that: The working electrode is one of a graphite electrode, a carbon electrode, a platinum electrode, and a titanium electrode; the reference electrode is one of an Ag / AgCl electrode, a saturated calomel electrode, and a mercurous sulfate electrode; the counter electrode is one of a platinum electrode, a titanium electrode, a stainless steel electrode, and a graphite electrode.

9. The method for extracting bromine from bromine-containing water sample by electro-oxidation according to claim 1, characterized in that: The tail gas absorption liquid of the absorption device is one or a mixture of NaOH, KI, SO2, Na2CO3 or low-temperature bromine salt solution. The effective ion concentration of the absorption liquid is equal to or greater than Br in the bromine-containing water sample. - concentration.

10. The method for extracting bromine from bromine-containing water sample by electro-oxidation according to claim 1, characterized in that: The selection range of the electric redox potential is 1.01V to 1.22V; during the electrochemical oxidation process, the membrane between the electrodes is one of a proton exchange membrane, a cation exchange membrane and an anion exchange membrane.

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