CN112281180A - Method for preparing chlorine by electrolyzing concentrated seawater through bipolar membrane - Google Patents
Method for preparing chlorine by electrolyzing concentrated seawater through bipolar membrane Download PDFInfo
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- CN112281180A CN112281180A CN202011060341.XA CN202011060341A CN112281180A CN 112281180 A CN112281180 A CN 112281180A CN 202011060341 A CN202011060341 A CN 202011060341A CN 112281180 A CN112281180 A CN 112281180A
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/24—Halogens or compounds thereof
- C25B1/26—Chlorine; Compounds thereof
Abstract
The invention discloses a method for preparing chlorine by electrolyzing concentrated seawater through a bipolar membrane, which comprises the following steps: (1) pretreating the concentrated seawater to reduce the concentration of calcium and magnesium ions in the seawater to below 10 ppm; (2) taking an electrolysis device with a bipolar membrane as a diaphragm, introducing concentrated seawater pretreated in the step (1) into an anode chamber of the electrolysis device, introducing a NaOH solution into a cathode chamber, starting a direct-current power supply to carry out electrolysis, splitting water into hydrogen ions and hydroxide ions on the bipolar membrane under the action of a direct-current electric field, respectively introducing the generated hydroxide ions and hydrogen ions into the anode chamber and the cathode chamber to react, finally generating effective chlorine in the anode chamber, and obtaining hydrogen and a sodium hydroxide solution in the cathode chamber. The invention does not need to arrange a chlorine gas separation device, so that the chlorine gas directly reacts in the anode chamber solution to generate the effective chlorine, and the device is relatively simple.
Description
Technical Field
The invention belongs to the technical field of water treatment and chlorine preparation, and particularly relates to a method for preparing effective chlorine by electrolysis in an electrolytic cell with a bipolar membrane as a diaphragm.
Background
The seawater desalination is one of important methods for solving global water resource shortage, and the concentrated seawater is a byproduct of the seawater desalination, is concentrated water formed by reverse osmosis of seawater, contains a large amount of chloride ions, has the concentration of about 3 percent, and is a natural bittern resource. Because the salt content is high, direct discharge can cause certain influence on the environment, so the method can be recycled by a series of process methods, such as concentration salt preparation, bipolar membrane electrodialysis acid and alkali preparation, lithium extraction, bromine extraction and the like, and the electrolytic preparation of available chlorine is an important process.
The available chlorine is chlorine gas, hypochlorous acid, hypochlorite and other oxidizing chlorine, and is commonly used as disinfectant, bactericide and bleaching agent.
The methods for producing chlorine by electrolysis in industry include mainly a non-diaphragm method, a diaphragm method and an ion membrane method. The diaphragm-free method mainly has the problems of low effective chlorine concentration, high energy consumption, more side reactions, easy scaling of electrodes and the like. The ion membrane method gradually replaces other two technologies due to the advantages of high yield of available chlorine, low energy consumption, high current efficiency and the like, and becomes the dominant process for preparing chlorine by electrolysis. The bipolar membrane is one kind of ionic membrane, has the characteristic of decomposing water into hydrogen ions and hydroxyl ions, and is mainly applied to the fields of electrodialysis and the like. In recent years, attention has been paid to the application of bipolar membranes to electrolysis.
Disclosure of Invention
The invention aims to provide a method for preparing chlorine by electrolyzing concentrated seawater by using an electrolysis device with a bipolar membrane as a diaphragm, wherein effective chlorine is directly obtained in an anode chamber, and alkali liquor obtained in a cathode chamber can be recycled.
A method for preparing chlorine by electrolyzing concentrated seawater through a bipolar membrane comprises the following steps:
(1) pretreating the concentrated seawater to reduce the concentration of calcium and magnesium ions in the seawater to below 10 ppm;
(2) taking an electrolysis device with a bipolar membrane as a diaphragm, introducing concentrated seawater pretreated in the step (1) into an anode chamber of the electrolysis device, introducing a NaOH solution into a cathode chamber, starting a direct-current power supply to carry out electrolysis, splitting water into hydrogen ions and hydroxide ions on the bipolar membrane under the action of a direct-current electric field, respectively introducing the generated hydroxide ions and hydrogen ions into the anode chamber and the cathode chamber to react, finally generating effective chlorine in the anode chamber, and obtaining hydrogen and a sodium hydroxide solution in the cathode chamber.
The reaction in the anode chamber is as follows:
2Cl-→Cl2+2e-；Cl2+H2O→HClO+HCl；NaOH+Cl2→NaClO+HCl；
the reaction in the cathode chamber is: h++2e-→H2。
The effective chlorine obtained in the anode chamber can be directly applied to disinfection and can also be further reacted with sodium hydroxide to generate sodium hypochlorite which can exist stably.
Preferably, the pretreatment method of the concentrated seawater comprises the following steps:
firstly, adding sodium hydroxide and sodium carbonate into concentrated seawater by a double-alkali chemical precipitation method to obtain calcium carbonate and magnesium hydroxide precipitates, removing most calcium and magnesium ions in the concentrated seawater, and simultaneously adjusting the pH to 6-7, so that the scaling problem can be effectively avoided;
and then, the calcium and magnesium ions and high-valence metal ions in the concentrated seawater are removed through adsorption of ion exchange resin, and the calcium and magnesium ions in the concentrated seawater are reduced to below 10ppm, so that the water quality requirement of the electrolyzed inlet water of the ion membrane is met.
In the invention, the adding amount of the sodium hydroxide and the sodium carbonate is excessive, namely more than the theoretical amount of the sodium hydroxide and the sodium carbonate required by calculation according to the content of calcium and magnesium ions in the concentrated seawater, so as to remove the calcium and magnesium ions in the concentrated seawater as far as possible.
In the present invention, the ion exchange resin is used for removing calcium and magnesium ions and high-valence metal ions, so that any ion exchange resin satisfying the above requirements is suitable, for example, 732 cation exchange resin, CH-93 chelate ion exchange resin, etc. The adsorption conditions can be determined according to the use requirements of the ion exchange resin and the concentration requirements of the final calcium and magnesium ions.
The invention provides an electrolysis device with a bipolar membrane as a diaphragm, which comprises: the device comprises an electrolytic cell, a bipolar membrane, an anode plate, a cathode plate, a direct current power supply, a circulating chamber and a metering pump; the electrolytic bath is divided into an anode chamber and a cathode chamber by the bipolar membrane, and the upper end and the lower end of the anode chamber and the lower end of the cathode chamber are respectively provided with a water outlet and a water inlet which are connected with the anode circulating chamber and the cathode circulating chamber by pipelines; the cathode chamber is provided with an exhaust port for discharging hydrogen, and the anode chamber is closed to enable chlorine to react in the solution to generate effective chlorine.
Preferably, the anode plate material is a mesh metal DSA, and the cathode plate material is a mesh titanium electrode plate.
Preferably, the bipolar membrane is one of a BP-1 type bipolar membrane (ASTOM Co, Japan) or an FBM type bipolar membrane (Fuma-Tech Co, Germany).
Preferably, when the direct current power supply carries out electrolysis, the distance between the electrode plates is 1-10cm, and the current density is 100--2The flow rate of each chamber is 20-50L/h, and the electrolysis temperature is controlled to be 15-35 ℃.
Preferably, the NaOH solution is introduced into the cathode chamber at an initial concentration of 0.05-2 mol/L.
Compared with the traditional ionic membrane electrolysis method, the method has the beneficial effects that: the invention does not need to arrange a chlorine gas separation device, so that the chlorine gas directly reacts in the anode chamber solution to generate the effective chlorine, and the device is relatively simple.
Drawings
FIG. 1 is a process flow diagram of the present invention.
FIG. 2 is a schematic view of an electrolysis apparatus according to the present invention.
Detailed Description
The invention will be further described with reference to the accompanying drawings.
Example 1
The pretreatment method of concentrated seawater (wherein the concentration of calcium ions is 552.38ppm, the concentration of magnesium ions is 1615.12ppm, and the concentration of NaCl is about 1.5%) is shown in figure 1. firstly, by a double-alkali chemical precipitation method, sodium hydroxide and sodium carbonate reagents are added into the concentrated seawater, 5.5g of sodium hydroxide and 1.5g of sodium carbonate are added into each liter of concentrated seawater, so that most of calcium and magnesium ions and polyvalent metal ions in the concentrated seawater are precipitated, and calcium carbonate and magnesium hydroxide are generated. Then, suspended matters in the sediment and the concentrated seawater are removed through suction filtration, and meanwhile, the pH value is adjusted to 6-7, so that the scaling problem can be effectively avoided. Further, the high-valence metal ions such as calcium, magnesium and the like in the concentrated seawater are further reduced in concentration by adsorbing through CH-93 ion exchange resin at the room temperature of 25 ℃ and controlling the flow rate to be 10BV/h, so that the water inlet requirement of electrolysis is met.
The concentration of NaCl in the pretreated concentrated seawater is about 3 percent; the calcium ion concentration is 2.58ppm, and the removal rate is 99.53 percent; the concentration of magnesium ions in the pretreated concentrated seawater is 2.26ppm, and the removal rate is 99.86%.
FIG. 2 shows an ionic membrane electrolysis apparatus, which is different from other ionic membrane electrolysis apparatuses, and in the present invention, a BP-1 type bipolar membrane (ASTOM Co, Japan) is used as an electrolysis diaphragm instead of a common perfluorosulfonic acid cation exchange membrane. The electrolysis device consists of a direct current power supply 6, a cathode plate 2, an anode plate 3, a bipolar membrane 1, a cathode chamber 4, an anode chamber 5, a cathode circulating chamber 7, an anode circulating chamber 8 and metering pumps 9 and 10. Wherein the bipolar membrane 1 separates the anode chamber 5 from the cathode chamber 4, and the upper end and the lower end of the anode chamber 5 and the lower end of the cathode chamber 4 are respectively provided with a water outlet and a water inlet which are connected with the anode circulating chamber 8 and the cathode circulating chamber 7 through pipelines. The cathode chamber is provided with an exhaust port for discharging hydrogen. The anode plate material is a net-shaped metal DSA, and the cathode plate material is a net-shaped titanium electrode plate.
Specifically, the cathode plate is connected with the cathode of the direct current power supply, and the anode plate is connected with the anode of the direct current power supply. Introducing the pretreated concentrated seawater (the NaCl concentration is about 30g/L) into an anode circulation chamber, and feeding the pretreated concentrated seawater into an anode chamber through a metering pump for electrolysis. 0.5M sodium hydroxide solution was added to the cathode recycle chamber and fed into the cathode chamber through a metering pump for electrolysis. The volume ratio of the electrolyte in the cathode chamber to the electrolyte in the anode chamber is 1: 1. The flow rates of the cathode chamber and the anode chamber are both 30L/h.
The pretreated concentrated seawater enters the anode chamber through the anode circulating chamber to be electrolyzed, and chloride ions in the concentrated seawater are reduced into effective chlorine. And (3) adding a dilute sodium hydroxide solution into the cathode circulating chamber, reacting in the cathode chamber to generate hydrogen and an alkali solution with higher concentration, wherein the hydrogen can be directly discharged from an exhaust port, and the alkali solution can be recycled.
Condensed water reflux is arranged in the anode circulating chamber and the cathode circulating chamber, and the electrolysis temperature is controlled to be about 25 ℃ at room temperature. Control electricityThe source is a steady current, and the current density is 100--2The distance between the electrode plates is 5cm, and the electrolysis time is 120 min.
The final effective chlorine concentration in the anode chamber can reach 1.152%, and the energy consumption is 59.58 kwh.kg-1An available chlorine.
Example 2
Instead of the commonly used cation-exchange membrane of perfluorosulfonic acid, a bipolar membrane of the FBM type (Fuma-Tech co, Germany) was used as the electrolytic membrane. The rest is the same as example 1.
The concentration of the available chlorine finally obtained in the anode chamber can reach 1.032%, and the energy consumption is 60.34 kwh.kg < -1 > of the available chlorine.
The bipolar membrane is adopted as the electrolytic diaphragm, and the characteristics of water decomposition on the bipolar membrane are utilized to generate hydroxyl ions, so that the generation of sodium hypochlorite is facilitated. Compared with the traditional ionic membrane electrolysis, the device does not need to be provided with a chlorine separation device, is simpler and easier, is favorable for realizing the resource utilization of concentrated seawater and realizes sustainable production.
Claims (8)
1. A method for preparing chlorine by electrolyzing concentrated seawater through a bipolar membrane comprises the following steps:
(1) pretreating the concentrated seawater to reduce the concentration of calcium and magnesium ions in the seawater to below 10 ppm;
(2) taking an electrolysis device with a bipolar membrane as a diaphragm, introducing concentrated seawater pretreated in the step (1) into an anode chamber of the electrolysis device, introducing a NaOH solution into a cathode chamber, starting a direct-current power supply to carry out electrolysis, splitting water into hydrogen ions and hydroxide ions on the bipolar membrane under the action of a direct-current electric field, respectively introducing the generated hydroxide ions and hydrogen ions into the anode chamber and the cathode chamber to react, finally generating effective chlorine in the anode chamber, and obtaining hydrogen and a sodium hydroxide solution in the cathode chamber.
2. The method of claim 1, wherein: the pretreatment method of the concentrated seawater comprises the following steps:
firstly, adding sodium hydroxide and sodium carbonate into concentrated seawater by a double-alkali chemical precipitation method to obtain calcium carbonate and magnesium hydroxide precipitates, removing most calcium and magnesium ions in the concentrated seawater, and simultaneously adjusting the pH value to 6-7;
then, the calcium and magnesium ions and high-valence metal ions in the concentrated seawater are removed by adsorption through ion exchange resin, and the calcium and magnesium ions in the concentrated seawater are reduced to be below 10 ppm.
3. The method of claim 2, wherein: the ion exchange resin is 732 cation exchange resin or CH-93 chelating ion exchange resin.
4. A method according to any one of claims 1 to 3, wherein: the electrolytic device with the bipolar membrane as the diaphragm comprises: the device comprises an electrolytic cell, a bipolar membrane, an anode plate, a cathode plate, a direct current power supply, a circulating chamber and a metering pump; the electrolytic bath is divided into an anode chamber and a cathode chamber by the bipolar membrane, and the upper end and the lower end of the anode chamber and the lower end of the cathode chamber are respectively provided with a water outlet and a water inlet which are connected with the anode circulating chamber and the cathode circulating chamber by pipelines; the cathode chamber is provided with an exhaust port for discharging hydrogen, and the anode chamber is closed to enable chlorine to react in the solution to generate effective chlorine.
5. The method of claim 4, wherein: the anode plate material is a net-shaped metal DSA, and the cathode plate material is a net-shaped titanium electrode plate.
6. A method according to any one of claims 1 to 3, wherein: the bipolar membrane is a BP-1 type bipolar membrane or an FBM type bipolar membrane.
7. A method according to any one of claims 1 to 3, wherein: when the direct current power supply carries out electrolysis, the distance between the electrode plates is 1-10cm, and the current density is 100-2000A/m-2The flow rate of each chamber is 20-50L/h, and the electrolysis temperature is controlled to be 15-35 ℃.
8. A method according to any one of claims 1 to 3, wherein: the initial concentration of NaOH solution introduced into the cathode chamber is 0.05-2 mol/L.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2022119407A1 (en) * | 2020-12-03 | 2022-06-09 | 한국에너지기술연구원 | Seawater electrolysis apparatus and seawater electrolysis fuel cell link system comprising same |
| CN117222779A (en) * | 2021-04-30 | 2023-12-12 | 迪诺拉永久电极股份有限公司 | Method and apparatus for producing sodium hypochlorite solution |
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| KR101361651B1 (en) * | 2012-09-27 | 2014-02-12 | (주) 테크윈 | A device using electrolyzer with a bipolar membrane and the method of producing hypochlorite solution and hydrogen gas thereby |
| JP2016168542A (en) * | 2015-03-12 | 2016-09-23 | 株式会社東芝 | Device and method for generating electrolytic water |
| CN110577229A (en) * | 2018-06-08 | 2019-12-17 | 江苏久吾高科技股份有限公司 | Waste salt recycling method and device |
| CN210458375U (en) * | 2019-05-21 | 2020-05-05 | 中国水利水电科学研究院 | Device for producing sodium hypochlorite disinfectant by electrolyzing seawater |
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2020
- 2020-09-30 CN CN202011060341.XA patent/CN112281180A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101361651B1 (en) * | 2012-09-27 | 2014-02-12 | (주) 테크윈 | A device using electrolyzer with a bipolar membrane and the method of producing hypochlorite solution and hydrogen gas thereby |
| JP2016168542A (en) * | 2015-03-12 | 2016-09-23 | 株式会社東芝 | Device and method for generating electrolytic water |
| CN110577229A (en) * | 2018-06-08 | 2019-12-17 | 江苏久吾高科技股份有限公司 | Waste salt recycling method and device |
| CN210458375U (en) * | 2019-05-21 | 2020-05-05 | 中国水利水电科学研究院 | Device for producing sodium hypochlorite disinfectant by electrolyzing seawater |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2022119407A1 (en) * | 2020-12-03 | 2022-06-09 | 한국에너지기술연구원 | Seawater electrolysis apparatus and seawater electrolysis fuel cell link system comprising same |
| CN117222779A (en) * | 2021-04-30 | 2023-12-12 | 迪诺拉永久电极股份有限公司 | Method and apparatus for producing sodium hypochlorite solution |
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