Single-stage high-fold salt concentration method based on membrane capacitive deionization technology

Abstract

The present invention provides a single-stage high-fold salt concentration method based on membrane capacitance deionization technology, comprising the following steps: S1. introducing a liquid to be treated and charging the electrode with a forward voltage, and when the amount of electricity in the electrode reaches 80-100% of the capacity of the electrode, stopping introducing the liquid to be treated; S2. introducing a concentrated liquid mother liquor and discharging the electrode with a reverse voltage, and when the amount of electricity in the electrode reaches 50-70% of the capacity of the electrode, stopping introducing the concentrated liquid mother liquor; S3. introducing a liquid to be treated and charging the electrode with a forward voltage, and when the amount of electricity in the electrode reaches 80-100% of the capacity of the electrode, stopping introducing the liquid to be treated; looping steps S2 and S3 until the liquid to be treated is treated; wherein the capacity of the electrode is the amount of electricity that the electrode has when it reaches an adsorption saturation state. The single-stage high-fold salt concentration method couples the electrosorption process with membrane separation, and has a strong ability to adjust the water and salt migration flux in the concentration stage.

Description

Technical Field

[0001] The invention relates to the technical field of membrane separation, in particular to a single-stage high-fold salt concentration method based on membrane capacitance deionization technology. Background Art

[0002] Industrial production activities represented by mining, thermal power, metallurgy and other industries are important guarantees for social operation and economic development, but they also inevitably produce a large amount of saline wastewater. In order to meet the needs of sustainable development and environmentally friendly social development, the concept of zero liquid discharge of industrial wastewater has been proposed. The level of salt concentration technology has a significant impact on the reduction of high-salinity water, equipment investment and operating cost control, and plays a vital role in sewage treatment and resource utilization, especially in recent years It has been widely used in near-zero wastewater discharge projects.

[0003] Traditional heat-driven salt concentration technologies such as evaporation ponds and multi-effect evaporation are gradually running counter to the development concept of carbon emission reduction in the wastewater treatment industry under the background of carbon neutrality due to problems such as large land occupation, high investment cost, and high operating energy consumption. Thanks to the introduction of membrane separation technologies such as microfiltration, nanofiltration, reverse osmosis and electrodialysis, low energy consumption and high-value salt recovery in the salt concentration process have been achieved, effectively reducing the cost of water treatment and salt recovery. However, due to the limited strength of filtration membranes and the insufficient ability of ion exchange membranes to adjust the water-salt migration flux, it is difficult to obtain high-concentration brine based on membrane separation technology. Summary of the invention

[0004] Based on this, it is necessary to provide a single-stage high-fold salt concentration method based on membrane capacitive deionization technology that can achieve effective desalination of saline wastewater and simultaneously concentrate the salt in a high-concentration brine in a single stage.

[0005] The present invention provides a single-stage high-fold salt concentration method based on membrane capacitive deionization technology, comprising the following steps:

[0006] S1. Passing the liquid to be treated and charging the electrode with a forward voltage, when the charge of the electrode reaches 80 to 100% of the capacity of the electrode, stopping passing the liquid to be treated;

[0007] S2. The concentrated liquid mother liquor is introduced and the electrode is discharged by a reverse voltage. When the charge of the electrode reaches 50 to 70% of the capacity of the electrode, the introduction of the concentrated liquid mother liquor is stopped;

[0008] S3. The treated liquid is introduced and the electrode is charged with a forward voltage, when the charge of the electrode reaches 80 to 100% of the capacity of the electrode;

[0009] Repeat step S2 and step S3 until the liquid to be treated is completely treated;

[0010] The capacity of the electrode is the amount of electricity the electrode has when it reaches an adsorption saturation state.

[0011] In some embodiments, the porosity of the electrode is 5-70%.

[0012] In some embodiments, the thickness of the electrode is 0.5-5 mm.

[0013] In some embodiments, the forward voltage has a voltage value of 0.8V to 1.6V.

[0014] In some embodiments, the reverse voltage has a voltage value of 0.5 to 4.0V.

[0015] In some embodiments, the concentration of the soluble ionic substances contained in the concentrated mother liquor is 50 to 200 g / L; optionally, the soluble ionic substances include one or more of NaCl, LiCl, NaNO3, NH4Cl and NaH2PO4.

[0016] In some embodiments, the concentration of NaCl contained in the liquid to be treated is less than 10 g / L.

[0017] In some embodiments, the concentration of NaCl contained in the liquid to be treated is 2-5 g / L.

[0018] In some embodiments, the device used in performing the method is a membrane capacitor deionized salt concentration device;

[0019] Optionally, the membrane capacitor deionized salt concentration device comprises a cathode side housing, a cathode side silicone gasket, a cathode titanium sheet current collector, a cathode electrode, a cation exchange membrane, a flow channel separator, an anion exchange membrane, an anode electrode, an anode titanium sheet current collector, an anode side silicone gasket and an anode side housing, which are arranged in sequence;

[0020] The cathode titanium sheet current collector is located between the cathode side silicone gasket and the cathode electrode and penetrates the upper part of the cathode side silicone gasket, and the cathode electrode is embedded in the groove of the cathode side silicone gasket; the anode titanium sheet current collector is located between the anode side silicone gasket and the anode electrode and penetrates the upper part of the anode side silicone gasket, and the anode electrode is embedded in the groove of the anode side silicone gasket;

[0021] It also includes a water inlet that sequentially penetrates the cathode side shell, the cathode side silicone gasket and the lower part of the cation exchange membrane; and a water outlet that sequentially penetrates the anode side shell, the anode side silicone gasket and the upper part of the anion exchange membrane.

[0022] In some embodiments, the method for preparing the anode electrode and / or the cathode electrode comprises:

[0023] The activated carbon, conductive carbon black, polytetrafluoroethylene and solvent are mixed, rolled, dried and cut to obtain the anode electrode and / or the cathode electrode;

[0024] Optionally, the solvent includes one or more of ethanol and dimethylformamide.

[0025] The single-stage high-multiple salt concentration method based on membrane capacitive deionization technology provided above, when the liquid to be treated is first introduced, the electrode performs high-capacity adsorption to a near-saturated state, and then when the concentrated liquid mother liquor is introduced, the electrode is discharged with a reverse voltage, so that the electrode releases part of the electricity and performs low-capacity desorption of salt and concentrates it into the concentrated mother liquor, and when the liquid to be treated is introduced again, the electrode is charged with a forward voltage, so that the electrode recovers to a near-saturated state and performs low-capacity adsorption, and the low-capacity adsorption and low-capacity desorption processes are cycled in the subsequent process until the liquid to be treated is completely treated. The first high-capacity adsorption helps to increase the ion chemical potential in the electrode to balance the concentration difference on both sides of the membrane, which is conducive to continuously reducing the water permeation rate; the subsequent low-capacity adsorption and low-capacity desorption cycles can ensure a high concentration ratio, high charge efficiency, and high effluent quality in the concentration stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of a membrane capacitor deionized salt concentration device;

[0027] Figure 2 It is a data diagram of the power-on method of the membrane capacitor deionized salt concentration device;

[0028] Figure 3 For Figure 2 Schematic diagram of adsorption and salt concentration results under the power-on method shown;

[0029] Figure 4 For Figure 2 A schematic diagram of a curve showing changes in the concentration of the liquid to be treated and the concentrated liquid mother liquor with the charge amount in each cycle under the charging method shown;

[0030] Figure 5 For Figure 2 Schematic diagram of the concentration results of the treated liquid and the treated concentrated liquid mother liquor after each cycle under the power-on method shown;

[0031] Figure 6 For Figure 2 Schematic diagram of the pH results of the treated liquid and the treated concentrated liquid mother liquor after each cycle under the power-on method.

[0032] in, Figure 1Middle: 1-water inlet; 2-cathode side shell; 3-cathode side silicone gasket; 4-cathode titanium sheet lead; 5-cathode electrode; 6-cation exchange membrane; 7-channel separator; 8-anion exchange membrane; 9-anode electrode; 10-anode titanium sheet lead; 11-anode side silicone gasket; 12-anode side shell; 13-water outlet. DETAILED DESCRIPTION

[0033] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0035] In the present invention, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0036] In the present invention, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0037] In this article, when referring to the unit of a data range, if there is a unit only after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 0.5-5mm means that the units of the left endpoint "2" and the right endpoint "5" are both mm (millimeter).

[0038] Only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and likewise any upper limit can be combined with any other upper limit to form an unspecified range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.

[0039] If there is no special description, all embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution. If there is no special description, all technical features and optional technical features of the present invention can be combined with each other to form a new technical solution.

[0040] The invention provides a single-stage high-fold salt concentration method based on membrane capacitance deionization technology, comprising the following steps: S1. introducing a liquid to be treated and charging an electrode with a forward voltage, and when the amount of electricity in the electrode reaches 80-100% of the capacity of the electrode, stopping introducing the liquid to be treated; S2. introducing a concentrated liquid mother liquor and discharging the electrode with a reverse voltage, and when the amount of electricity in the electrode reaches 50-70% of the capacity of the electrode, stopping introducing the concentrated liquid mother liquor; S3. introducing a liquid to be treated and charging the electrode with a forward voltage, and when the amount of electricity in the electrode reaches 80-100% of the capacity of the electrode, stopping introducing the liquid to be treated; and repeating steps S2 and S3 until the liquid to be treated is completely treated; wherein the capacity of the electrode is the amount of electricity the electrode has when it reaches an adsorption saturation state.

[0041] It should be noted that the electrode reaching the adsorption saturation state means that the electrode adsorbs NaCl to the saturation state. "Single-stage high-fold salt concentration" means that the NaCl in the liquid to be treated is directly concentrated into the concentrated liquid mother liquor. After the liquid to be treated undergoes a desalination and concentration cycle, the NaCl concentration contained therein is less than 0.5g / L, which meets the reuse standard. After the concentrated liquid mother liquor undergoes a desalination and concentration cycle, the concentration of soluble ionic substances contained therein increases, and the concentration of soluble ionic substances contained in the concentrated liquid mother liquor is 50-200g / L.

[0042] When the treated liquid is passed into step S1, the electrode is charged with a forward voltage so that the charge of the electrode reaches 80-100% of the capacity of the electrode; for example, it can be 82-100%, 82-97%, 85-95%, 88-92%, 90-92% or 80-91%, etc., without specific limitation.

[0043] When the concentrated mother liquor is introduced in step S2, a reverse voltage is used to discharge the electrode so that the charge of the electrode reaches 50-70% of the capacity of the electrode; for example, it can be 52-67%, 55-65%, 52-63%, 55-60%, 58-60%, 55-58% or 50-66%, etc., without specific limitation.

[0044] When the treated liquid is introduced in step S3, the electrode is charged with a forward voltage so that the charge of the electrode reaches 80-100% of the capacity of the electrode; for example, it can be 82-100%, 82-97%, 85-95%, 88-92%, 90-92% or 80-91%, etc., without specific limitation.

[0045] It should be noted that in both step S1 and step S3, a forward voltage is used to charge the electrode, and in step S2, a reverse voltage is used to discharge the electrode. In step S1 and step S3, the electrode can adsorb salt, and in step S2, the electrode can desalinate into a concentrated liquid mother liquor.

[0046] Understandably, when single-stage high-fold salt concentration is performed, the liquid to be treated is first introduced and the electrode is charged with a forward voltage so that the charge of the electrode reaches 80-100% of the charge of the electrode when it is in an adsorption saturation state, that is, when the liquid to be treated is introduced for the first time, the electrode performs high-capacity adsorption to a near-adsorption saturation state; then the concentrated liquid mother liquor is introduced and the electrode is discharged with a reverse voltage so that the charge of the electrode reaches 50-70% of the charge of the electrode when it is in a saturated adsorption state, that is, when the concentrated liquid mother liquor is introduced, the electrode releases part of the charge and performs low-capacity desorption to concentrate the salt on the electrode into the concentrated liquid mother liquor, thereby realizing low-capacity desorption of the electrode; when the liquid to be treated is introduced again, the electrode is charged with a forward voltage so that the charge of the electrode is restored to 80-100% of the charge of the electrode when it is in a saturated state, that is, when the liquid to be treated is introduced, the electrode is again charged with part of the charge and performs low-capacity adsorption at the same time; in the subsequent process, the low-capacity adsorption and low-capacity desorption processes of the electrode are cycled until the liquid to be treated is completely treated.

[0047] The first high-capacity adsorption of the electrode by the liquid to be treated helps to improve the ion chemical potential in the electrode to balance the concentration difference on both sides of the membrane, which is conducive to continuously reducing the water permeation rate; the subsequent cycle of low-capacity adsorption and low-capacity desorption of the electrode can ensure high concentration rate, high charge efficiency and high water quality in the low-capacity desorption stage. At the same time, this method has low operating energy consumption.

[0048] It should be noted that this single-stage high-multiple salt concentration method couples the electrosorption process with the membrane separation process, and has a strong ability to adjust the water and salt migration flux in the concentration stage.

[0049] In some embodiments, the porosity of the electrode is 5-70%, for example, 10-70%, 15-65%, 20-60%, 25-55%, 30-50%, 35-45%, or 35-40%, etc. The low porosity of the electrode helps to reduce the water penetration rate, making the salt concentration process efficient and sustainable.

[0050] It should be noted that the electrodes include a cathode electrode and an anode electrode, and the porosity of the cathode electrode and the anode electrode is independently 5 to 70%.

[0051] In some embodiments, the thickness of the electrode is 0.5 to 5 mm; for example, it can be 0.5 to 4.5 mm, 1 to 4 mm, 1.5 to 3.5 mm, 2 to 3 mm, or 2.5 to 3 mm, etc., without limitation. The thick electrode helps to store a large amount of ions, making the salt concentration process continuous and efficient.

[0052] It should be noted that the thickness of the cathode electrode and the anode electrode are each independently 0.5 to 5 mm.

[0053] In some embodiments, the forward voltage is 0.8 to 1.6 V; for example, it can be 0.9 to 1.6 V, 0.9 to 1.5 V, 1.0 to 1.4 V, 1.1 to 1.3 V, 1.2 to 1.3 V or 0.8 to 1.2 V, etc., without limitation. Using a forward voltage within the above range helps to increase the electrode adsorption rate, adsorption amount and maintain a high coulombic efficiency, and also helps to maintain the pH of the effluent.

[0054] In some embodiments, the reverse voltage has a voltage value of 0.5 to 4.0 V; for example, it may be 1.0 to 4.0 V, 1.5 to 3.5 V, 2.0 to 3.0 V, 2.5 to 3.0 V, 2.0 to 2.5 V or 0.5 to 3.5 V, etc., without limitation. Using a reverse voltage with a voltage value in the above range helps to increase the concentration rate and concentration ratio of the salt.

[0055] In some embodiments, the concentration of the soluble ionic substance contained in the concentrated liquid mother liquor is 50-200 g / L; for example, it can be 60-200 g / L, 70-190 g / L, 80-180 g / L, 90-170 g / L, 100-160 g / L, 110-150 g / L, 120-150 g / L or 130-140 g / L, etc., without specific limitation. When the concentration of the soluble ionic substance contained in the concentrated liquid mother liquor is within the above range, the concentration ratio of the salt concentration stage is high, and the overall operation water yield is high.

[0056] Optionally, the soluble ionic substances include one or more of NaCl, LiCl, NaNO3, NH4Cl and NaH2PO4.

[0057] In some embodiments, the concentration of NaCl contained in the liquid to be treated is less than 10 g / L; for example, it may be 9 g / L, 8 g / L, 7 g / L, 6 g / L, 5 g / L, 4 g / L, 3 g / L, 2 g / L or 1 g / L. Preferably, the concentration of NaCl contained in the liquid to be treated is 2 to 5 g / L.

[0058] In some embodiments, the device used to perform the single-stage high-fold salt concentration method is a membrane capacitor deionization salt concentration device.

[0059] Optionally, the membrane capacitor deionized salt concentration device includes a cathode side shell, a cathode side silicone gasket, a cathode titanium sheet lead, a cathode electrode, a cation exchange membrane, a flow channel separator, an anion exchange membrane, an anode electrode, an anode titanium sheet lead, an anode side silicone gasket and an anode side shell which are arranged in sequence; the cathode titanium sheet lead is located between the cathode side silicone gasket and the cathode electrode and penetrates the upper part of the cathode side silicone gasket, and the cathode electrode is embedded in the groove of the cathode side silicone gasket; the anode titanium sheet lead is located between the anode side silicone gasket and the anode electrode and penetrates the upper part of the anode side silicone gasket, and the anode electrode is embedded in the groove of the anode side silicone gasket; it also includes a water inlet that penetrates the cathode side shell, the cathode side silicone gasket and the lower part of the cation exchange membrane in sequence; and a water outlet that penetrates the anode side shell, the anode side silicone gasket and the upper part of the anion exchange membrane in sequence.

[0060] It should be noted that the above components can be fixed and tightened by bolts after being assembled in sequence.

[0061] When single-stage high-fold salt concentration is performed, the liquid to be treated and the concentrated liquid mother liquor enter alternately from the lower water inlet, pass through the flow channel screen, and flow out from the upper water outlet. The electrode is connected to a constant voltage power supply to provide a stable voltage to drive salt ions into or out of the electrode to achieve desalination and concentration. The conductivity meter detects the concentration changes of the fresh water and concentrated water pools in real time to evaluate the desalination and concentration effects; the balance records the mass transfer information of the device quality monitoring operation stage in real time.

[0062] In some embodiments, the method for preparing the anode electrode and / or the cathode electrode comprises:

[0063] The activated carbon, conductive carbon black, polytetrafluoroethylene and solvent are mixed, rolled, dried and cut to obtain the anode electrode and / or the cathode electrode; optionally, the solvent includes one or more of ethanol and dimethylformamide.

[0064] As an example, the following method can be used to prepare the anode electrode and / or cathode electrode: activated carbon, conductive carbon black and polytetrafluoroethylene are mixed in a mass ratio of 8:1:1, and an appropriate amount of anhydrous ethanol is dropped and stirred continuously until it becomes a clay-like state; the clay-like electrode is rolled into a uniform sheet with a thickness of 5 mm by a roller press and then transferred to an oven and dried at 80°C for 24 hours; the dried sheet electrode is cut into square blocks with a size of 50*50*5 mm, and is pressed at 10 MPa for 10 minutes along a thickness of 5 mm by a tablet press to obtain a dense electrode block.

[0065] The technical solution is described in detail below in conjunction with specific embodiments.

[0066] Example

[0067] Use Figure 1The membrane capacitor deionization salt concentration device shown in the figure performs desalination and salt concentration on the treated liquid with a NaCl concentration of 2g / L. Figure 1 As shown, the membrane capacitor deionized salt concentration device includes a cathode side shell 2, a cathode side silicone gasket 3, a cathode titanium sheet lead 4, a cathode electrode 5, a cation exchange membrane 6, a flow channel separator 7, an anion exchange membrane 8, an anode electrode 9, an anode titanium sheet lead 10, an anode side silicone gasket 11 and an anode side shell 12 which are arranged in sequence; the cathode titanium sheet lead 4 is located between the cathode side silicone gasket 3 and the cathode electrode 5 and penetrates the upper part of the cathode side silicone gasket 3, and the cathode electrode 5 is embedded in the groove of the cathode side silicone gasket 3; the anode titanium sheet lead 10 is located between the anode side silicone gasket 11 and the anode electrode 9 and penetrates the upper part of the anode side silicone gasket 11, and the anode electrode 9 is embedded in the groove of the anode side silicone gasket 11; it also includes a water inlet 1 and a water outlet 13, the water inlet 1 sequentially penetrates the cathode side shell 2, the cathode side silicone gasket 3 and the lower part of the cation exchange membrane 6; the water outlet 13 sequentially penetrates the anode side shell 12, the anode side silicone gasket 11 and the upper part of the anion exchange membrane 8.

[0068] Use Figure 2 The charge and discharge control method shown in the figure operates the membrane capacitor deionization salt concentration device to achieve single-stage high-fold concentration of salt in the treated liquid. During desalination treatment, the treated liquid enters from the water inlet 1, and at the same time, the anode electrode 9 and the cathode electrode 5 are charged 280C with a forward voltage of 1.4V to make the electrodes adsorb to a near-saturated state. The treated liquid flows out from the water outlet 13 through the flow channel partition 7, achieving high-capacity first adsorption to obtain the treated liquid.

[0069] Then, a concentrated liquid mother liquor with a NaCl concentration of 200 g / L is introduced from the water inlet 1, and at the same time, a reverse voltage of 1.4 V is used to discharge the anode electrode 9 and the cathode electrode 5 by 80C, so that the NaCl adsorbed by the electrode can quickly migrate to the concentrated liquid mother liquor, and the concentrated liquid mother liquor flows out from the water outlet 13 through the flow channel partition 7, realizing low-capacity concentration, that is, low-capacity desorption of the electrode.

[0070] In the subsequent 20 adsorption and concentration cycles, the liquid to be treated is introduced from the water inlet 1 during the adsorption stage, and the anode electrode 9 and the cathode electrode 5 are charged 80C with a forward voltage of 1.4V to allow the electrodes to adsorb the NaCl contained in the liquid to be treated. In the concentration stage of the 1st to 10th cycles, the concentrated liquid mother liquor is a 100g / L NaCl solution, and in the concentration stage of the 11th to 20th cycles, the concentrated liquid mother liquor is a 200g / L NaCl solution; at the same time, in the concentration stage of the 1st to 20th cycles, after the concentrated liquid mother liquor is introduced from the water inlet 1, the anode electrode 9 and the cathode electrode 5 are discharged 80C with a reverse voltage of 1.4V to discharge the NaCl adsorbed by the electrodes into the concentrated liquid mother liquor.

[0071] In the above desalination process, the amount of salt adsorbed and concentrated by the electrode in the adsorption stage and concentration stage is as follows: Figure 3 As shown by Figure 3 It can be seen that the amount of adsorbed salt and the amount of concentrated salt in the electrode during the adsorption stage and the concentration stage reached a balance, and the cycle stability was good. In the 11th to 20th cycle, the salt circulation amount was slightly reduced compared with the 1st to 10th cycle due to the change of the concentrated liquid mother liquor to 200g / LNaCl solution, indicating that the increase in concentration has a significant inhibitory effect on the ion discharge electrode. Figure 4 As shown, the membrane capacitor deionized salt concentration device of the present invention can still achieve stable desalination and concentration effects.

[0072] In the above concentration process, the concentration results of the liquid to be treated and the concentrated liquid mother liquor after each cycle are shown in the figure below: Figure 5 As shown. Figure 5 It can be seen that after each cycle, the concentration of NaCl contained in the treated liquid to be treated can be lower than 0.5 g / L, reaching the reuse standard; and the concentration of the treated concentrated liquid mother liquor is higher than the concentration of the concentrated liquid mother liquor introduced during the cycle, or although the concentration of the treated concentrated liquid mother liquor is equal to the concentration of the concentrated liquid mother liquor introduced during the cycle, the volume of the treated concentrated liquid mother liquor increases, indicating that a high-concentration concentrated liquid can be stably produced in the above desalination process.

[0073] In the above desalination process, the pH results of the treated liquid and the treated concentrated liquid mother liquor after each cycle are as follows: Figure 6 As shown by Figure 6 It can be seen that the pH values ​​of the treated liquid to be treated and the treated concentrated liquid mother liquor are both stable in a near-neutral state, indicating that the single-stage high-fold salt concentration method of the present invention has a high effluent quality in the desalination and salt concentration stages.

[0074] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0075] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A single-stage high-fold salt concentration method based on membrane capacitive deionization technology, characterized in that: The steps include: S1. Passing the liquid to be treated and charging the electrode with a forward voltage, when the charge of the electrode reaches 80 to 100% of the capacity of the electrode, stopping passing the liquid to be treated; S2. The concentrated liquid mother liquor is introduced and the electrode is discharged by a reverse voltage. When the charge of the electrode reaches 50 to 70% of the capacity of the electrode, the concentrated liquid mother liquor is stopped; S3. Passing the liquid to be treated and charging the electrode with a forward voltage, when the charge of the electrode reaches 80 to 100% of the capacity of the electrode, stopping passing the liquid to be treated; Repeat step S2 and step S3 until the liquid to be treated is completely treated; The capacity of the electrode is the amount of electricity the electrode has when it reaches adsorption saturation state; the concentration of NaCl in the liquid to be treated is less than 10g / L, the concentration of soluble ionic substances in the concentrated liquid mother liquor is 50-200g / L, and the porosity of the electrode is 30-50%.

2. The single-stage high-fold salt concentration method based on membrane capacitive deionization technology according to claim 1, characterized in that: The thickness of the electrode is 0.5-5 mm.

3. The single-stage high-fold salt concentration method based on membrane capacitive deionization technology according to claim 1, characterized in that: The forward voltage has a voltage value of 0.8 to 1.6V.

4. The single-stage high-fold salt concentration method based on membrane capacitive deionization technology according to claim 1, characterized in that: The reverse voltage has a voltage value of 0.5 to 4.0V.

5. The single-stage high-fold salt concentration method based on membrane capacitive deionization technology according to claim 1, characterized in that: The soluble ionic substances include one or more of NaCl, LiCl, NaNO3, NH4Cl and NaH2PO4.

6. The single-stage high-fold salt concentration method based on membrane capacitive deionization technology according to claim 1, characterized in that: The concentration of NaCl contained in the liquid to be treated is 2-5 g / L.

7. The single-stage high-fold salt concentration method based on membrane capacitive deionization technology according to any one of claims 1 to 6, characterized in that: The device used in carrying out the method is a membrane capacitor deionized salt concentration device.

8. The single-stage high-fold salt concentration method based on membrane capacitive deionization technology according to claim 7, characterized in that: The membrane capacitor deionized salt concentration device comprises a cathode side shell, a cathode side silica gel gasket, a cathode titanium sheet current collector, a cathode electrode, a cation exchange membrane, a flow channel separator, an anion exchange membrane, an anode electrode, an anode titanium sheet current collector, an anode side silica gel gasket and an anode side shell, which are arranged in sequence; The cathode titanium sheet current collector is located between the cathode side silicone gasket and the cathode electrode and penetrates the upper part of the cathode side silicone gasket, and the cathode electrode is embedded in the groove of the cathode side silicone gasket; the anode titanium sheet current collector is located between the anode side silicone gasket and the anode electrode and penetrates the upper part of the anode side silicone gasket, and the anode electrode is embedded in the groove of the anode side silicone gasket; It also includes a water inlet that sequentially penetrates the cathode side housing, the cathode side silica gel gasket and the lower portion of the cation exchange membrane; And, a water outlet sequentially penetrates the anode side shell, the anode side silica gel gasket and the upper part of the anion exchange membrane.

9. The single-stage high-fold salt concentration method based on membrane capacitive deionization technology according to claim 8, characterized in that: The method for preparing the anode electrode and / or the cathode electrode comprises: The activated carbon, conductive carbon black, polytetrafluoroethylene and solvent are mixed, rolled, dried and cut to prepare the anode electrode and / or the cathode electrode.

10. The single-stage high-fold salt concentration method based on membrane capacitive deionization technology according to claim 9, characterized in that: The solvent includes one or more of ethanol and dimethylformamide.

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