A device and method for removing alkaline cations in a total organic carbon measuring instrument

Abstract

The present invention provides a device and method for removing alkaline cations in a total organic carbon measuring instrument. The device comprises an anode electrode, a cathode electrode, and a proton exchange membrane and a cation exchange membrane arranged between the two electrodes. The proton exchange membrane is arranged adjacent to the anode electrode to form a first cavity with the anode electrode; the cation exchange membrane is arranged adjacent to the cathode electrode to form a second cavity with the cathode electrode; a third cavity is formed between the proton exchange membrane and the cation exchange membrane, and the device also comprises a circulation pump for circulating a fluid through the first cavity and the second cavity, so that the fluid circulates in the first and second cavities and feed water is introduced into the third cavity. The present invention removes alkaline cations in feed water through the exchange membrane theory, with high efficiency. The treated feed water is then subjected to total organic carbon measurement, and the measurement result is more accurate.

Description

Technical Field

[0001] The invention relates to the field of total organic carbon measurement, in particular to a device and method for removing alkaline cations in a total organic carbon measuring instrument. Background Art

[0002] At present, there are two major methods for detecting total organic carbon content, namely dry method and wet method. Although the dry method is fast, it has low selectivity for carbon dioxide and low analytical accuracy. The wet method mainly oxidizes organic carbon in water samples into carbon dioxide through ultraviolet light or oxidizing agents. This method has high selectivity for carbon dioxide and good analytical sensitivity and accuracy. The total organic carbon (TOC) content in the feed water of thermal power plants is low, so the wet method is the most appropriate choice. However, because the boiler feed water samples of power plants contain more ammonia, the TOC device using the wet method is within the detection range, but due to the presence of ammonia nitrogen, ultraviolet light or oxidizing agents can oxidize ammonia nitrogen into nitrate nitrogen and nitrite nitrogen, which seriously affects the conductivity.

[0003] At present, there are biological, physical and chemical methods for removing ammonia nitrogen. Although the biological treatment process has low cost, good removal effect, clean and environmentally friendly, the nitrogen cycle of the overall process is relatively long, and more human intervention is required in the nitrogen cycle pathway. The current conventional method of directly removing ammonia nitrogen is concentration and purification. Concentration includes ion exchange, capacitive deionization and electrodialysis, and purification includes struvite precipitation, stripping and membrane separation. Because single ammonia removal has more or less defects, it is necessary to find a method to improve the efficiency of ammonia nitrogen removal and reduce energy consumption.

[0004] There is a capacitive deionization method in the prior art, which uses the surface of a static electrode to adsorb ions in water. It can remove cations such as ammonia nitrogen during the desalination process, but it also removes anions, including carbonate ions and bicarbonate ions, which results in a loss of some organic carbon content. The TOC instrument measures the treated desalted water, which will cause errors in the TOC indication. In addition, the traditional capacitive deionization method will result in low current efficiency due to the common ion effect, and the fixed electrode has limited absorption capacity, so the electrode needs to be replaced within a certain period of time. Summary of the invention

[0005] In order to solve the above-mentioned problems of the prior art, the present invention provides an alkaline cation removal device and method, which is based on electrochemistry and ion exchange membrane theory and flowing electrode capacitance (FCDI) theory, and removes other cations such as ammonium ions in the feed water without removing anions. It is set in a TOC instrument to reduce the detection error of TOC.

[0006] The technical solutions adopted are as follows:

[0007] A basic cation removal device in a total organic carbon measuring instrument comprises an anode electrode, a cathode electrode, and a proton exchange membrane and a cation exchange membrane arranged between the two electrodes, wherein the proton exchange membrane is arranged adjacent to the anode electrode, and a first cavity is formed between the proton exchange membrane and the anode electrode; the cation exchange membrane is arranged adjacent to the cathode electrode, and a second cavity is formed between the proton exchange membrane and the cathode electrode; a third cavity is formed between the proton exchange membrane and the cation exchange membrane, and water is supplied to flow into the third cavity, and a circulation pump is also included for circulating fluid through the first cavity and the second cavity;

[0008] Furthermore, the fluid includes an electrolyte and / or an active material and / or a conductive additive material.

[0009] Furthermore, the active material is (10-20)% (w / v) activated carbon; the conductive additive material is an electron mediator, and salt is added to the electrolyte.

[0010] Furthermore, an anion exchange resin is provided on the flow path of the fluid flowing from the second cavity into the first cavity.

[0011] Furthermore, there is an adsorption chamber in the middle of the third cavity, which mainly allows the feed water to stay in the adsorption zone to complete the adsorption of alkaline ions and cations.

[0012] Furthermore, the thickness of the first, second and third cavities are all 0.01-1 mm.

[0013] The present invention also discloses a method for using the alkaline cation removal device, which comprises the following steps:

[0014] S1: applying voltage or current between the anode electrode and the cathode electrode;

[0015] S2: the fluid is introduced into the first cavity, the fluid flows into the second cavity after flowing into the first cavity, and then returns from the second cavity to the first cavity, and the circulation is carried out in this way; or the fluid is introduced into the second cavity first, the fluid enters the second cavity and then enters the first cavity, and then returns from the first cavity to the second cavity for circulation, and the circulation is realized by a circulation pump arranged outside the cavity;

[0016] S3: continuously supplying ion-containing feed water to the third chamber;

[0017] The hydrogen ions in the first cavity enter the third cavity through the proton exchange membrane and combine with the anions in the third cavity. The alkaline cations in the third cavity enter the second cavity through the cation exchange membrane and combine with the hydroxide in the second cavity. The feed water with the alkaline ions removed flows out of the third cavity.

[0018] Furthermore, the anode electrode 1 and the cathode electrode 2 are connected via a constant current power supply, the voltage of the constant current power supply is (1-2) V, and the current density is (20-35) A / m 2 .

[0019] Furthermore, the water supply flow rate is (0.5-1.8) mL / min.

[0020] Furthermore, the fluid passes through an anion exchange resin, and the hydroxide ions generated between the cathodes regenerate the anion exchange resin, and the anions generated by the regeneration of the anion exchange resin enter the electrolyte.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. Introduce an alkaline cation removal device into the TOC instrument manufactured based on the wet method principle to remove ammonia nitrogen from the feed water to avoid affecting the conductivity of the test feed water;

[0023] 2. The alkaline cation removal device is designed based on electrochemistry and ion exchange membrane theory and the flowing electrode capacitance (FCDI) theory. It removes other cations such as ammonium ions in the feed water without removing anions. It will not remove carbon-containing anions such as carbonate, and will not affect the detection results of total organic carbon. The total organic carbon content of the treated feed water is tested to make the test data more accurate.

[0024] 3. The fluid circulates in the first and second chambers through the circulation pump and can be reused repeatedly to reduce energy consumption and improve efficiency.

[0025] 4. During the external circulation process between the cathode and cathode of the electrode, the anion exchange resin will pass through. When the current is passed, the hydroxide ions generated between the cathodes regenerate the anion exchange resin, and the anions regenerated by the anion exchange resin enter the electrolyte. It can not only maintain the stability of the pH of the electrolyte, but also increase the ions of the electrolyte and improve the conductivity of the conductive liquid.

[0026] 5. The present invention adopts the flow electrode capacitor (FCDI), which uses the charge in the dynamically flowing electrode slurry to adsorb ions in the water, and also uses a part of the electrodialysis principle to remove ions to improve the adsorption efficiency. Moreover, the FCDI includes two modules, one for removing alkaline cations and the other for regenerating the flow electrode and producing high-concentration brine. Therefore, the electrode loss in the present invention is small and does not need to be frequently replaced. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the alkaline cation removal device of the present invention;

[0028] Figure 2This is a schematic diagram of the TOC device detection process;

[0029] Among them, there are an anode electrode 1, a cathode electrode 2, a proton exchange membrane 3, a cation exchange membrane 4, a first cavity 5, a second cavity 6, a third cavity 7, an anion exchange resin 8, a fluid 9, and a circulation pump 10. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with specific embodiments.

[0031] refer to Figure 1 , 2 The present invention provides an alkaline cation removal device in a total organic carbon measuring instrument, comprising an anode electrode 1 and a cathode electrode 2. The anode electrode 1 undergoes an oxidation reaction to release electrons, and hydrogen ions are generated near the anode after water electrolysis. The cathode electrode 2 undergoes a reduction reaction to receive electrons, and hydroxide ions are generated near the cathode after water electrolysis.

[0032] A proton exchange membrane 3 and a cation exchange membrane 4 are arranged between the two electrodes. The proton exchange membrane 3 is arranged adjacent to the anode electrode 1, and a first cavity 5 is formed between the proton exchange membrane 3 and the anode electrode 1; the cation exchange membrane 4 is arranged adjacent to the cathode electrode 2, and a second cavity 6 is formed between the cathode electrode 2; the proton exchange membrane 3 only allows protons to pass, i.e. hydrogen ions, and does not allow other cations and anions to pass. The cation exchange membrane only allows cations to pass, and does not allow anions to pass. A third cavity 7 is formed between the proton exchange membrane 3 and the cation exchange membrane 4, and water is supplied to flow in.

[0033] The thickness of the first, second and third cavities are all 0.01-1 mm.

[0034] The invention also includes a circulation pump 10 for circulating the fluid 9 through the first cavity and the second cavity. The circulation pump 10 is a magnetic pump that can circulate the fluid. An anion exchange resin 8 is arranged on the path through which the fluid from the second cavity to the first cavity flows. The hydroxide ions generated between the cathodes regenerate the anion exchange resin, and the anions regenerated by the anion exchange resin enter the electrolyte. The fluid can be reused repeatedly to reduce energy consumption and improve efficiency.

[0035] In addition, the present invention also relates to a method for removing alkaline cations, comprising the following steps:

[0036] S1: applying voltage or current between anode electrode 1 and cathode electrode 2;

[0037] S2: Fluid is introduced into the first cavity, and the fluid flows into the second cavity after flowing into the first cavity, and then returns to the first cavity from the second cavity, and circulates in this way; or fluid is first introduced into the second cavity, and the fluid enters the first cavity after entering the second cavity, and then returns to the second cavity from the first cavity to circulate, and the circulating flow is achieved by a circulating pump 10 arranged outside the cavity; no matter which cavity the fluid flows into first, it is only necessary to ensure that the fluid circulates in the first and second cavities.

[0038] S3: continuously introducing ion-containing feed water into the third chamber 7;

[0039] The hydrogen ions in the first cavity enter the third cavity through the proton exchange membrane and combine with the anions in the third cavity. The alkaline cations in the third cavity enter the second cavity through the cation exchange membrane and combine with the hydroxide in the second cavity. The feed water with the alkaline ions removed flows out of the third cavity.

[0040] A constant current power supply can be used to connect the anode electrode 1 and the cathode electrode 2. Preferably, the voltage of the constant current power supply can be (1-2) V, and the current density can be (20-35) A / m 2 .

[0041] Preferably, the fluid 9 includes an electrolyte and / or an active material and / or a conductive additive. The active material is (10-20)% (w / v) activated carbon; the conductive additive is an electron mediator, and salt is added to the electrolyte. Adding the above substances to the fluid can enhance the conductivity, increase the rate and efficiency of the electrochemical reaction, improve the interface stability, and enhance the electrolyte's ability to wet the electrode and the diaphragm.

[0042] There is an adsorption chamber in the middle of the third cavity, which mainly allows the feed water to stay in the adsorption zone to complete the adsorption of alkaline ions and cations.

[0043] After the anode and cathode electrodes are energized, the fluid flows through the first and second chambers, and hydroxide ions and hydrogen are generated near the cathode electrode, that is, in the second chamber; hydrogen ions and oxygen are generated near the anode electrode, that is, in the first chamber. Then, the feed water containing ions is passed into the third chamber. As a preferred method, the feed water flow rate is (0.5-1.8) mL / min.

[0044] The hydrogen ions in the first cavity enter the third cavity through the proton exchange membrane, and combine with the anions in the third cavity. The combined hydride continues to remain in the third cavity. The cations in the third cavity, such as alkaline cations such as ammonium, will enter the second cavity through the cation exchange membrane, and combine with the hydroxide ions in the second cavity. The combined hydroxide remains in the second cavity and flows with the fluid. The fluid flows through the anion exchange resin. The hydroxide ions generated between the cathodes regenerate the anion exchange resin, and the anions generated by the regeneration of the anion exchange resin enter the electrolyte. It can not only maintain the stability of the pH of the electrolyte, but also increase the ions of the electrolyte and improve the conductivity of the conductive liquid.

[0045] By circulating the fluid in the first and second chambers through the circulation pump, the alkaline cations in the third chamber are continuously removed, which can reduce the detection error of the TOC instrument. The fluid is repeatedly recycled, which can reduce energy consumption and improve the removal efficiency without repeated replacement. At the same time, the saturated positive and negative electrode liquids can be fully mixed in the electrode renewal device. This mode is equivalent to short-circuiting the positive and negative electrodes. The ions adsorbed on the electrode surface are attracted by the opposite charges and separated from the double electric layer into the solution, completing the renewal of the electrodes while forming a concentrated solution.

[0046] refer to Figure 2 , which is the detection process of the TOC instrument. The water sample passes through the cation removal device, and then enters the TOC instrument for detection after the cations are removed. The processing unit of the TOC instrument performs data processing, and the water supply after the detection is discharged from the waste system.

[0047] The present invention verifies the removal efficiency of ammonium in the water after passing through the alkaline cation removal device. Three different water samples are taken, the initial ammonium ion concentration in the water samples is measured, and the ammonium ion concentration of the water samples after passing through the alkaline cation removal device is tested respectively to calculate the removal rate of ammonium ions. The calculation formula of the ammonium ion removal rate is: ammonium ion removal rate = (initial ammonium ion concentration - ammonium ion concentration after treatment) / initial ammonium ion concentration × 100%. Among them, the ammonium ion content is measured by Nessler's reagent spectrophotometry. The following table is an experimental table for detecting the removal rate of ammonium ions.

[0048] Initial ammonium ion concentration (ug / L) Ammonium ion concentration after treatment (ug / L) Ammonium ion removal rate (%) 10 0 100 20 0 100 40 0.264 99.34 80 0.712 99.11 160 1.584 99.01 280 3.276 98.83 400 5.4 98.65 500 7.2 98.56

[0049] From the test results, it can be seen that the alkaline cation removal device can successfully remove ammonium ions from the feed water, the conductivity is reduced, and the removal efficiency is high, up to 100%.

[0050] The alkaline cation removal device of the present invention is introduced into the TOC instrument, the standard TOC solution is processed, and the error of the TOC solution measurement is detected. The experimental steps are as follows:

[0051] Prepare standard TOC solution and add a certain amount of ammonia nitrogen;

[0052] The solution was tested using a TOC instrument that incorporated an alkaline cation removal device;

[0053] Record the concentration of TOC solution before and after the test and calculate the error.

[0054] The following table is an experimental table of measurement errors obtained by applying the alkaline cation removal device to the total organic carbon measurement instrument;

[0055] Standard TOC solution concentration (ug / L) Ammonia nitrogen concentration (ug / L) TOC test results (ug / L) Indication error (%) 490 10 489.922 0.02 480 20 479.928 0.02 460 40 460.128 0.03 420 80 420.507 0.12 340 160 341.012 0.30 220 280 222.104 0.96 100 400 103.268 3.27 0 500 3.645 /

[0056] The removal device provided by the present invention removes other cations such as ammonium ions in the feed water without removing anions, and will not remove carbon-containing anions such as carbonate, and will not affect the detection result of total organic carbon. The total organic carbon content of the treated feed water is detected, and the detected data is more accurate. It can be seen from the table that the error of the TOC instrument test is low after the alkaline ions are removed, and the indication error is between 0.02% and 3.27%, which can better and accurately reflect the real TOC value.

[0057] The above content is only a detailed description of the present invention, and the present invention cannot be considered to be limited to the above description. For those skilled in the art to which the present invention belongs, some improvements or substitutions can be made without departing from the inventive concept of the present invention, but all of them belong to the protection scope of the present invention.

Claims

1. A device for removing alkaline cations in a total organic carbon measuring instrument, characterized in that: The invention comprises an anode electrode (1), a cathode electrode (2), and a proton exchange membrane (3) and a cation exchange membrane (4) arranged between the two electrodes. The proton exchange membrane (3) is arranged adjacent to the anode electrode (1) and forms a first cavity (5) with the anode electrode (1); the cation exchange membrane (4) is arranged adjacent to the cathode electrode (2) and forms a second cavity (6) with the cathode electrode (2); a third cavity (7) is formed between the proton exchange membrane (3) and the cation exchange membrane (4) and is supplied with water flowing therein. The invention also comprises a circulation pump (10) for circulating a fluid (9) through the first cavity and the second cavity.

2. The alkaline cation removal device according to claim 1, characterized in that: The fluid (9) includes an electrolyte and / or an active material and / or a conductive additive.

3. The alkaline cation removal device according to claim 1, characterized in that: The fluid (9) comprises an active material; or an active material and an electrolyte; or an active material and a conductive additive; or an active material, an electrolyte and a conductive additive, wherein the active material is (10-20)% (w / v) activated carbon.

4. The alkaline cation removal device according to claim 1, characterized in that: An anion exchange resin (8) is provided on the path through which the fluid flowing from the second cavity into the first cavity flows.

5. The alkaline cation removal device according to claim 1, characterized in that: There is an adsorption chamber in the middle of the third cavity, which mainly allows the feed water to stay in the adsorption zone to complete the adsorption of alkaline ions and cations.

6. The alkaline cation removal device according to claim 1, characterized in that: The thickness of the first, second and third cavities are all 0.01-1 mm.

7. A method for removing alkaline cations using the device according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: applying a voltage or current between the anode electrode (1) and the cathode electrode (2); S2: introducing a fluid into the first cavity, the fluid flows into the first cavity and then into the second cavity, and then returns from the second cavity to the first cavity, and so on, in a cycle; or introducing a fluid into the second cavity first, the fluid enters the second cavity and then into the first cavity, and then returns from the first cavity to the second cavity, and the cycle is achieved by a circulation pump (10) arranged outside the cavity; S3: continuously introducing ion-containing feed water into the third chamber (7); The hydrogen ions in the first cavity enter the third cavity through the proton exchange membrane and combine with the anions in the third cavity. The alkaline cations in the third cavity enter the second cavity through the cation exchange membrane and combine with the hydroxide in the second cavity. The feed water with the alkaline ions removed flows out of the third cavity.

8. The method for removing alkaline cations according to claim 7, wherein: The anode electrode (1) and the cathode electrode (2) are connected via a constant current power supply, wherein the voltage of the constant current power supply is (1-2) V and the current density is (20-35) A / m 2 .

9. The method for removing alkaline cations according to claim 7, wherein: The flow rate of the water supply is (0.5-1.8) mL / min.

10. The method for removing alkaline cations according to claim 7, wherein: The fluid (9) passes through the anion exchange resin (8), and the hydroxide ions produced between the cathodes regenerate the anion exchange resin.

11. The alkaline cation removal device according to claim 1, characterized in that: The fluid (9) includes a conductive additive material; or a conductive additive material and an electrolyte; Or a conductive additive material and an active material; or an active material, an electrolyte and a conductive additive material, wherein the conductive additive material is an electron mediator.

12. The alkaline cation removal device according to claim 1, characterized in that: The fluid (9) includes an electrolyte; or a conductive additive material and an electrolyte; or an electrolyte and an active material; or an active material, an electrolyte and a conductive additive material, wherein a salt is added to the electrolyte.

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