CN113426495A - Device and method for enhancing performance of desalination cell by using ion exchange mixed bed - Google Patents

Device and method for enhancing performance of desalination cell by using ion exchange mixed bed Download PDF

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Publication number
CN113426495A
CN113426495A CN202110654139.8A CN202110654139A CN113426495A CN 113426495 A CN113426495 A CN 113426495A CN 202110654139 A CN202110654139 A CN 202110654139A CN 113426495 A CN113426495 A CN 113426495A
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feed liquid
electrolyte
ion exchange
electrode
chamber
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杨涛
林鹏
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Hohai University HHU
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Hohai University HHU
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J47/00Ion-exchange processes in general; Apparatus therefor
    • B01J47/02Column or bed processes
    • B01J47/04Mixed-bed processes
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/42Treatment of water, waste water, or sewage by ion-exchange
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/42Treatment of water, waste water, or sewage by ion-exchange
    • C02F2001/427Treatment of water, waste water, or sewage by ion-exchange using mixed beds

Abstract

The device comprises at least two electrode chambers for filling electrolyte, a plurality of groups of material liquid chambers which are connected in parallel and used for filling material liquid and at least two diaphragms, wherein each electrode chamber comprises at least one electrolyte inlet, at least one electrolyte outlet and at least one electrode, each material liquid chamber is a material liquid flowing area and comprises at least one material liquid inlet and at least one material liquid outlet, an ion exchange mixed bed is filled in each material liquid chamber, the ion exchange mixed bed is formed by mixing an anion exchanger and a cation exchanger, each material liquid chamber is arranged between every two adjacent electrode chambers, and the diaphragms are respectively arranged between each material liquid chamber and between each material liquid chamber and each electrode chamber. The ion exchange mixed bed is cheap and safe, can effectively enhance the ionic conductivity of the low-salinity feed liquid, thereby reducing the energy consumption of the desalination cell, improving the desalination rate and the feed liquid recovery rate, and has practical significance for the popularization and the application of the flow desalination cell.

Description

Device and method for enhancing performance of desalination cell by using ion exchange mixed bed
Technical Field
The invention belongs to the technical field of electrochemical desalination, and particularly relates to a device and a method for enhancing the performance of a desalination cell by using an ion exchange mixed bed.
Background
Water shortage has become a common facing problem worldwide. On one hand, with the continuous development of social economy, the demand of human beings on water resources is increasing, and on the other hand, due to extreme climate caused by environmental pollution and global climate change, fresh water resources are in short supply day by day. 71 percent of the area of the world is covered by water, but the fresh water resource which is practically available for human is extremely limited, and the seawater desalination and utilization become important ways for solving the water crisis. The existing common desalination technologies comprise reverse osmosis, multistage flash evaporation, multi-effect evaporation, electrodialysis and the like, but have the problems of strict requirement on feed water pretreatment, secondary pollution, low recovery rate, scaling, high energy consumption, high construction cost, high maintenance difficulty and the like. Therefore, a desalination technology which is more environment-friendly, energy-saving, higher in recovery rate and convenient to maintain is needed.
Desalination cells are an electrochemical desalination technology developed in recent years, and a great deal of research has proved the feasibility of the desalination cells in the field of seawater desalination. The desalination cell works at normal temperature and normal pressure, the requirement on water inlet pretreatment is low, and the construction cost and the maintenance cost are reduced. The device is an energy storage device, and in the desalting and concentrating processes, along with the storage and release of energy, most of input electric energy can be recycled without an additional energy recovery device, so that low-energy-consumption desalting is realized. Compared with other desalination cells in the form of solid electrodes, the flow type electrode adopted by the flow desalination cell has the advantages of high desalination rate, low cost, small equipment volume and the like, and can better meet the requirements of practical application.
Essentially, the energy consumption and desalination rate of a desalination cell depend on its internal resistance, and the internal resistance is greatly influenced by the salinity of seawater. In the working process of the desalting cell, the concentration process of the seawater is a process of increasing salinity and reducing internal resistance, which is beneficial to reducing desalting energy consumption; in the desalination process, the salinity of the seawater is reduced, the internal resistance is increased, and the discharge voltage is reduced or the charging voltage is increased, so that the desalination energy consumption is increased rapidly, the desalination rate is reduced rapidly, and the total soluble solid content of the effluent is difficult to reduce to the drinking water standard. In addition, this problem also causes problems such as low salt rejection rate and low recovery rate. Although the salinity of effluent and the desalting energy consumption can be greatly reduced by reducing the charging and discharging current, the desalting rate is also reduced. Therefore, a simple, cheap and effective method is needed to increase the desalination rate of the desalination cell in the desalination process and reduce energy consumption.
Disclosure of Invention
The technical problem to be solved is as follows: aiming at the technical problems, the invention provides a device and a method for enhancing the performance of a desalination cell by using an ion exchange mixed bed, which simply and effectively solve the problem of the increase of the internal resistance of the cell when the salinity of a feed liquid is reduced, can greatly improve the desalination rate and the desalination rate of the desalination cell, reduce the desalination energy consumption and promote the practical application of the desalination cell in the field of desalination and desalination.
The technical scheme is as follows: the device comprises at least two electrode chambers for filling electrolyte, a plurality of groups of feed liquid chambers which are connected in parallel and used for filling feed liquid, and at least two diaphragms, wherein each electrode chamber comprises at least one electrolyte inlet, at least one electrolyte outlet and at least one electrode, each feed liquid chamber is a feed liquid flowing area and comprises at least one feed liquid inlet and at least one feed liquid outlet, an ion exchange mixed bed is filled in each feed liquid chamber, the ion exchange mixed bed is formed by mixing an anion exchanger and a cation exchanger, each feed liquid chamber is arranged between every two adjacent electrode chambers, and the diaphragms are respectively arranged between each feed liquid chamber and each feed liquid chamber, between each feed liquid chamber and each electrode chamber, are used for separating the electrode chambers and the feed liquid chambers and play a role in ion selective permeation.
Preferably, the mass ratio of the anion exchanger to the cation exchanger is A: b, wherein A is more than or equal to 0 and less than or equal to 10000, B is more than or equal to 0 and less than or equal to 10000, A and B are not 0 at the same time, the situation that only anion exchange resin or cation exchange resin is added exists, or the anion exchange resin or the cation exchange resin is amphoteric ion exchange resin, and the situation also only needs to adopt one resin; the anion exchanger is at least one of strong base type anion exchange resin, weak base type anion exchange resin, amphoteric ion exchange resin, anion exchange fiber and amphoteric ion exchange fiber, and the cation exchanger is at least one of strong acid type cation exchange resin, weak acid type cation exchange resin and cation exchange fiber.
Preferably, the ion exchange mixed bed is an ion exchange mixed bed in which a chlorine type anion exchange resin and a sodium type cation exchange resin are mixed in a mass ratio of 1.5: 1.
Preferably, the electrode is a composite electrode formed of at least one material selected from graphite felt, graphite paper, carbon paper, activated carbon fiber, carbon felt, carbon cloth, glassy carbon, magnesium, aluminum, zinc, iron, tin, lead, copper, silver, bismuth, platinum and gold, and preferably graphite felt and zinc.
Preferably, the diaphragm is at least one of a homogeneous cation exchange membrane, a homogeneous anion exchange membrane, a heterogeneous cation exchange membrane, a heterogeneous anion exchange membrane, a ceramic membrane and an organic polymer membrane, and the diaphragms on two sides of the ion exchange mixed bed are preferably a heterogeneous cation exchange membrane and a heterogeneous anion exchange membrane.
Preferably, the feed liquid is seawater, brackish water, wastewater containing heavy metal ions, sewage or artificially prepared solution containing charged particles, preferably NaCl solution, the electrolyte is at least one of anion storage electrolyte and cation storage electrolyte, and the anion storage electrolyte does not participate in oxygen reduction reaction, and electron gain and loss are generated by cations or electroneutral substances, including Zn2+、Fe2+/Fe3+、Sn2+/Sn4+、Pb2+、Cu2+/Cu+、Ag+、Ni2+、Co2+/Co3+、Mn2+/Mn3+/Mn4+/Mn7+、Cr2+/Cr3+、Ti3+/Ti4+Or V2+/V3+/V4+/V5+Metal ions and ions of the metal ions complexed with the respective complexing agent, 4-hydroxy-piperidinol oxides or methyl viologens, preferably containing Zn2+ZnCl of2A solution; the cation in the cation storage electrolyte does not participate in redox reaction, and electron gain and loss are generated by anions or electric neutral substances, including Br2/Br-、I-/I3 -、[Fe(CN)6]4-/[Fe(CN)6]3-Sulfides, polysulfides, quinone derivatives, alloxazine derivatives, flavin derivatives, viologen derivativesOr ferrocene derivatives, preferably containing I-/I3 -NaI/NaI of (A)3And (3) solution.
Preferably, the electrolyte further comprises a conductive agent, and the conductive agent is NaCl or NH4Cl、KCl、Na2SO4、NaNO3And at least one of sodium acetate and sodium citrate, which does not participate in the redox reaction.
Preferably, the concentration of the feed liquid is 0.002-2 mol/L, the concentration of the electrolyte is 0.001-10 mol/L, and the content of the conductive agent is 0-2 mol/L.
The method for enhancing the performance of the desalination cell by using the ion exchange mixed bed by the device comprises the following steps: by adopting the device, the feed liquid is circularly injected into the feed liquid chamber, the electrolyte is circularly injected into the electrode chamber, the desalting cell structure is operated to desalt the feed liquid, and the operation is stopped when the feed liquid reaches a preset conductivity value.
The device is applied to the fields of seawater and brackish water desalination and heavy metal ion removal in water.
The principle of the invention is as follows: the ion exchange mixed bed is filled in the feed liquid chamber of the flow desalting cell to reduce the internal resistance, when the salinity of the feed liquid in the flow desalting cell is low, the conductivity of the feed liquid is poor, the internal resistance of the cell is high, and the ion conductivity of the feed liquid with low salinity can be increased by filling the ion exchange mixed bed in the feed liquid chamber, so that the internal resistance of the desalting cell is reduced, the desalting energy consumption is reduced, and the desalting rate is increased.
Has the advantages that:
(1) the ion exchange mixed bed adopted by the invention can obviously improve the ionic conductivity of the low-salinity feed liquid and reduce the internal resistance of the desalting cell, thereby greatly improving the desalting speed and reducing the desalting energy consumption, and the lower the salt content of the feed liquid, the more obvious the beneficial effect is.
(2) The use of the ion exchange mixed bed can reduce the salinity of the feed liquid to a quite low level (for example, below 100 mg/L NaCl), thereby greatly improving the salt rejection rate; meanwhile, the desalination cell can concentrate the feed liquid to a quite high salt content (for example, more than 60 g/L NaCl), so that the recovery rate is greatly improved, and the discharge of concentrated wastewater is reduced.
(3) The method and the device have strong operability and easy implementation, and the filled ion exchange mixed bed can continuously work without regeneration.
(4) The ion exchange mixed bed adopted by the invention is composed of ion exchange resin and ion exchange fiber which have high commercialization degree, low price and no harm, and the cost increased by adopting the ion exchange mixed bed is extremely low.
(5) The method and the device provided by the invention are suitable for most electrolytes, have strong universality and can promote the practical application of the desalting battery.
Drawings
FIG. 1 is a schematic structural diagram of a double-electrode chamber, a single feed liquid chamber and a mixed ion exchange bed filled in the feed liquid chamber;
FIG. 2 is a schematic structural diagram of a double-electrode chamber, a multi-feed chamber and an ion exchange mixed bed filled in the feed chamber;
FIG. 3 is a schematic diagram of the structure of a double-electrode chamber, a multi-feed chamber and a part of feed chamber filled with an ion exchange mixed bed;
FIG. 4 is a schematic diagram of a structure with two or more electrode chambers, wherein the feed chamber can be one or more, and can be viewed as a result of connecting a plurality of structures shown in FIG. 3 in series;
FIG. 5 is a schematic diagram of a structure of a double electrode chamber, a double feed chamber and a part of the feed chamber filled with an ion exchange mixed bed, and is an example of the situation shown in FIG. 3;
FIG. 6 is a graph showing the change of charge/discharge potential and the change of salt content in the feed liquid in comparative example 1 and example 1, in which a is a current density of 1.5 mA/cm2The time charge and discharge potential variation process and the salt content variation process of the feed liquid are shown in the graph, b is the current density of 2.0 mA/cm2A graph of the change process of the charging and discharging potential and the change process of the salt content of the feed liquid is shown;
FIG. 7 is a graph showing the relationship between specific energy consumption and salt content in the feed liquid in comparative example 1 and example 1, wherein a is the magnitude of current density of 1.5 mA/cm2The specific energy consumption and the salt content of the feed liquid are related, b is the current density of 2.0 mA/cm2Specific energy consumption per hourA relation graph with the salt content of the feed liquid;
FIG. 8 is a graph showing the relationship between the desalination rate and the current density and the salt content in the case of using a 1 g/L NaCl solution as a feed liquid in comparative example 1 and example 1, wherein a is a graph showing the relationship between the desalination rate and the current density and the salt content in the case of using a 1 g/L NaCl solution as a feed liquid in comparative example 1, and b is a graph showing the relationship between the desalination rate and the current density and the salt content in the case of using a 1 g/L NaCl solution as a feed liquid in example 1;
FIG. 9 is a graph showing the change of salt content in comparative example 2 and example 2 when 10 g/L NaCl solution was used as the feed solution;
FIG. 10 is a graph showing the change of constant current charge and discharge potentials of comparative example 3 and example 3 using 35 g/L, 20 g/L, 10 g/L, and 5 g/L NaCl solutions as the feed chambers, in which a is a graph showing the change of constant current charge and discharge potentials of comparative example 3 using 35 g/L, 20 g/L, 10 g/L, and 5 g/L NaCl solutions as the feed chambers, and b is a graph showing the change of constant current charge and discharge potentials of example 3 using 35 g/L, 20 g/L, 10 g/L, and 5 g/L NaCl solutions as the feed chambers;
the numerical designations in the drawings represent the following: 1. an electrode chamber a; 2. electrode chambers b (when the number of the electrode chambers is plural, each electrode chamber can be respectively filled with the same or different electrolyte); 3. feed liquid chambers (when the number of the feed liquid chambers is multiple, feed liquid with different concentrations and different flow rates can flow through each feed liquid chamber); 4. an ion exchange membrane a; 5. ion exchange membrane b (4 and 5 are opposite in permselectivity, if 4 represents an anion exchange membrane, then 5 represents a cation exchange membrane, if 5 represents a cation exchange membrane, then 4 represents an anion exchange membrane); 6. an electrode a; 7. electrode b (6 and 7 may be the same or different electrodes); 8. an electrolyte inlet a; 9. an electrolyte outlet a; 10. an electrolyte inlet b; 11. an electrolyte outlet b; 12. an ion exchange mixed bed; 13. a feed liquid inlet; 14. and a feed liquid outlet.
Detailed Description
The invention is further described below with reference to the accompanying drawings and specific embodiments.
In the comparative examples and comparative examples of the present specification, the anion-storing electrolyte is specifically 0.3 mol/L ZnCl2 + 1 mol/L NH4Electrolysis of aqueous Cl solution with stored cationThe liquid is specifically 0.3 mol/L I2+ 1.2 mol/L NaI aqueous solution (or 0.3 mol/L NaI)3+ 0.9 mol/L aqueous NaI solution); the flow desalting battery module is made of polytetrafluoroethylene, a pipeline for conveying and storing the anionic electrolyte and the feed liquid is a silicone tube, and a pipeline for conveying and storing the cationic electrolyte is a fluorine rubber tube; the flow channels in each feed chamber of the assembled flow desalination cell are about 3.3 cm by 1 cm and have a volume of about 10 cm3(ii) a The electrode in the anion storage electrode chamber is a zinc sheet with the thickness of 0.3 mm, the electrode in the cation storage electrode chamber is a graphite felt with the thickness of 2 mm, and after the fixation, the effective areas of the electrodes are all 7 cm2(ii) a The circulating pumps of the feed liquid and the two electrolytes are peristaltic pumps, the flow rate of the feed liquid is set to be 30 mL/min, and the flow rates of the electrolytes are both set to be 13 mL/min; the ion exchange membranes are respectively an AMI-7001 heterogeneous anion exchange membrane and a CMI-7000 heterogeneous cation exchange membrane, and the ion exchange mixed bed is formed by mixing chlorine type 717 anion exchange resin and sodium type 732 cation exchange resin in a mass ratio of 1.5: 1; before the ion exchange mixed bed is used, the feed liquid to be desalted needs to be washed for a period of time, so that the influence of ions released by the ion exchange mixed bed on the salt content of the feed liquid is reduced; the conductivity change of the feed liquid is recorded by a conductivity meter, the charging and discharging process of the battery is controlled by a double constant potential rectifier, and the current and potential change is recorded.
FIG. 1 shows a flow desalting cell with the simplest structure, which adopts a configuration of 'anion storage electrolyte-anion exchange membrane-ion exchange mixed bed-cation exchange membrane-cation storage electrolyte'. The electrode chamber a 1 and the electrode chamber b 2 are respectively filled with anion-storage electrolyte and cation-storage electrolyte (the electrolyte enters the electrode chamber from an electrolyte inlet a 8 and an electrolyte inlet b 10 and flows out from an electrolyte outlet a 9 and an electrolyte outlet b 11), and the electrode a 6 and the electrode b 7 are respectively made of zinc sheets and graphite felts. After the feed liquid chamber 3 is filled with the ion exchange mixed bed 12, feed liquid is injected and filled (the feed liquid enters the feed liquid chamber from the feed liquid inlet 13 and flows out from the feed liquid outlet 14), a load is connected between the two electrodes, the flow desalting cell discharges, Zn loses electrons and is oxidized into Zn2+And Cl is taken out from the feed liquid chamber 3 through the ion exchange membrane a 4 (anion exchange membrane)-(ii) a While, I in the vicinity of the graphite felt3 -To obtain electrons which are reduced to I-Na is taken out of the feed liquid chamber 3 through an ion exchange membrane b 5 (cation exchange membrane)+Thereby desalinating the feed liquid in the feed liquid chamber 3 (reducing the salt content), which is accompanied by the release of electrical energy. Applying a power supply between the electrodes to make Zn2+Reduction to Zn, I-Oxidation to I3 -And then the feed liquid is concentrated (the salt content is increased), the process is accompanied with the input of electric energy, and the energy consumption for desalting is that the input electric energy is subtracted from the output electric energy. The ion exchange resin has the function of serving as a solid ion conductor to enhance the ion conductivity in the feed liquid chamber when the feed liquid is low and the ion conductivity is weak.
When the feed chamber has more than one compartment, as shown in fig. 2, the ion exchange mixed bed 12 may be filled in each feed chamber 3. Since concentration of the feed liquid is a process of increasing conductivity, ion exchange packed beds may be omitted in the concentration process, as shown in fig. 3, an ion exchange mixed bed 12 is packed only in a part of the feed liquid chamber 3 where the desalination process occurs, fig. 4 is a schematic structural diagram of two or more electrode chambers, and the feed liquid chamber 3 may be one or more than one, and may be a result of connecting a plurality of structures shown in fig. 3 in series. To illustrate this method of use more specifically, a flow desalination cell structure as shown in fig. 5 is assembled, and a structure of "cation-storage electrolyte-cation exchange membrane-anion exchange membrane-ion exchange mixed bed-cation exchange membrane-cation-storage electrolyte" is adopted, that is, the first feed chamber 3 from left to right is not filled with the ion exchange mixed bed 12, and the second feed chamber 3 is filled with the ion exchange mixed bed 12, wherein both electrodes 6, 7 are graphite felt, and the structure belongs to one example of the scenario shown in fig. 3. During operation, the positive electrode of the external power supply can be connected with the electrode 6, the negative electrode is connected with the electrode 7, and I near the electrode 6-Oxidation to I3 -The electrode chamber 1 discharges Na to the first feed liquid chamber+(ii) a While I in the vicinity of the electrode 73 -To obtain electrons which are reduced to I-Taking in Na from the second feed chamber 3+Under the action of electric field and ion exchange membrane, the second oneCl in the feed chamber 3-Moving directionally into the first feed chamber, the whole is shown as the first feed chamber 3 is concentrated, the second feed chamber 3 is desalted, and the ion exchange mixed bed 12 can only play a role in the feed chamber 3 where desalting occurs. Then the electrolyte in the electrode chamber 1 and the electrolyte in the electrode chamber 2 are continuously exchanged through a circulating pump, so that the reaction can be continuously carried out.
Example 1
(1) The structure of the flow desalination cell shown in fig. 1 was assembled.
(2) NaCl solutions of 5 g/L, 4 g/L, 3 g/L, 2 g/L, 1 g/L, 0.8 g/L, 0.6 g/L, 0.4 g/L and 0.2 g/L are respectively prepared as feed liquids, the feed liquid chambers are respectively filled with the NaCl solution with the concentration gradient, the two electrode chambers are respectively filled with the anionic electrolyte and the cationic electrolyte, the electrolyte and the feed liquid are kept still, two ends of each electrode are connected with a double potentiostat, the internal resistance of the battery is analyzed by an impedance spectroscopy analysis method, and specific results are shown in Table 1.
(3) Selecting 5 g/L NaCl solution as feed liquid for desalination, wherein the dosage of the feed liquid is 50 mL, and circularly conveying the feed liquid by using a peristaltic pump; 100 mL of each of the anion storage electrolyte and the cation storage electrolyte are circularly conveyed by a peristaltic pump; adopting a constant current charging and discharging mode, and setting the current density to be 1.5 mA/cm2(the current is 10.5 mA), discharging for 12 h; during the discharge period, the salt content of the feed liquid is uniformly reduced along with the time, the internal resistance is increased, the output potential is continuously reduced, if the potential between the electrodes is reduced to 0V, the discharge is stopped in advance, and the charging is converted; the charging current is 1.5 mA/cm2And stopping charging after the concentration of the feed liquid is recovered to 5 g/L, and recording the salt content of the feed liquid and the potential change between the electrodes in the process. The discharge and charge potentials were set to 2.0 mA/cm, respectively2(current 14 mA), the procedure was repeated and the salinity of the feed solution and the change in the potential between the electrodes were recorded, and the results are shown in FIG. 6; and calculating and drawing the relation between the specific energy consumption of the flow desalting cell and the salt content of the feed liquid according to the calculation, and the result is shown in figure 7.
(4) Selecting 1 g/L NaCl solution as feed liquid for desalination, wherein the dosage of the feed liquid is 50 mL, and circularly conveying the feed liquid by using a peristaltic pump; 100 mL of each of the anion storage electrolyte and the cation storage electrolyte are circularly conveyed by a peristaltic pump; the constant potential discharge mode is adopted, the discharge potential is 0V, the salt content of the feed liquid and the current density change process in the process are recorded, the relation between the desalination rate and the salt content of the feed liquid is calculated and drawn according to the change process, and the result is shown in figure 8.
Comparative example 1
(1) The flow desalination cell structure shown in fig. 1 was assembled, but the feed liquid chamber 3 was not filled with an ion exchange mixed bed.
(2) NaCl solutions of 5 g/L, 4 g/L, 3 g/L, 2 g/L, 1 g/L, 0.8 g/L, 0.6 g/L, 0.4 g/L and 0.2 g/L are respectively prepared as feed liquids, the feed liquid chambers are respectively filled with the NaCl solution with the concentration gradient, the two electrode chambers are respectively filled with the anionic electrolyte and the cationic electrolyte, the electrolyte and the feed liquid are kept still, two ends of each electrode are connected with a double potentiostat, the internal resistance of the battery is analyzed by an impedance spectroscopy analysis method, and specific results are shown in Table 1.
(3) Selecting 5 g/L NaCl solution as feed liquid for desalination, wherein the dosage of the feed liquid is 50 mL, and circularly conveying the feed liquid by using a peristaltic pump; 100 mL of each of the anion storage electrolyte and the cation storage electrolyte are circularly conveyed by a peristaltic pump; adopting a constant current charging and discharging mode, and setting the current density to be 1.5 mA/cm2(the current is 10.5 mA), discharging for 12 h; during the discharge period, the salt content of the feed liquid is uniformly reduced along with the time, the internal resistance is increased, the output potential is continuously reduced, if the potential between the electrodes is reduced to 0V, the discharge is stopped in advance, and the charging is converted; the charging current is 1.5 mA/cm2And stopping charging after the concentration of the feed liquid is recovered to 5 g/L, and recording the salt content of the feed liquid and the potential change between the electrodes in the process. The discharge and charge potentials were set to 2.0 mA/cm, respectively2(current 14 mA), the procedure was repeated and the salinity of the feed solution and the change in the potential between the electrodes were recorded, and the results are shown in FIG. 6; and calculating and drawing the relation between the specific energy consumption of the flow desalting cell and the salt content of the feed liquid according to the calculation, and the result is shown in figure 7.
(4) Selecting 1 g/L NaCl solution as feed liquid for desalination, wherein the dosage of the feed liquid is 50 mL, and circularly conveying the feed liquid by using a peristaltic pump; 100 mL of each of the anion storage electrolyte and the cation storage electrolyte are circularly conveyed by a peristaltic pump; the constant potential discharge mode is adopted, the discharge potential is 0V, the salt content of the feed liquid and the current density change process in the process are recorded, the relation between the desalination rate and the salt content of the feed liquid is calculated and drawn according to the change process, and the result is shown in figure 8.
TABLE 1
Salt content (mg/L) Comparative example 1 internal resistance (Ω) EXAMPLE 1 internal resistance (omega)
5000 21.7 18.2
4000 25.0 19.2
3000 28.0 19.7
2000 36.4 21.4
1000 56.7 25.1
800 69.2 27.0
600 85.1 30.0
400 105 33.4
200 209 45.1
The data of comparative example 1 and example 1 were analyzed. According to table 1, as the salt content of the feed liquid decreases, the internal resistance of the desalination cells in comparative example 1 and example 1 increases, while the internal resistance of the desalination cell in example 1 is always lower than that in comparative example 1 and the increase is lower than that in comparative example 1, which shows that when the salt content of the feed liquid is lower, the internal resistance can be reduced by filling the ion exchange mixed bed in the flow desalination cell, and the effect is more remarkable as the salt content of the feed liquid is lower. According to the figures 6 and 7, in the constant current charging and discharging process, the change interval of the salt content of the feed liquid comprises 1000-5000 mg/L, and when the current density is the same, the desalination rate of the comparative example 1 and the desalination rate of the example 1 are the same; the potential in the discharging process is lower than that in the charging process, and the internal resistance of the battery is increased along with the reduction of the salt content of the feed liquid, so that the discharging potential is reduced, the charging potential is increased, namely the electric energy output is reduced, the electric energy input is increased, and the specific energy consumption is increased along with the reduction of the salt content; the high current density charging and discharging can cause the discharge potential to be reduced and the discharge potential to be increased, so the specific energy consumption is higher than that of the low current density charging and discharging; the specific energy consumption of example 1 was lower than that of comparative example 1 at different current densities, since the ion exchange packed bed reduced the internal resistance of the cell, resulting in a reduction in energy consumption. According to FIG. 8, during the desalting process by short-circuit discharge of 1000 mg/L NaCl solution, the potential difference between the electrodes is constant at 0V, and the electric energy released by the batteries in comparative example 1 and example 1 is used for overcoming the internal resistance of the batteries; the desalination rate is positively correlated with the current, the lower the salt content of the feed liquid is, the higher the internal resistance of the cell is, the lower the current is, and the lower the desalination rate is; the addition of the ion exchange mixed bed reduces the internal resistance of the cell, increases the short circuit current, and thus increases the desalination rate. In conclusion, the ion exchange packed bed can reduce the desalting energy consumption and improve the desalting rate by enhancing the ionic conductivity and reducing the internal resistance of the flow desalting cell. To better illustrate the universality of this process, comparative example 2 and example 2 were set up, i.e., scenarios where more than one feed chamber, only a portion of the feed chamber, was filled with an ion exchange mixed bed.
Example 2
(1) The structure of the flow desalination cell shown in fig. 5 was assembled.
(2) Through a proper pipeline connection method, cation-storage electrolyte enters the electrode chamber 2 from the electrolyte inlet 10, flows out from the electrolyte outlet 11 after filling the electrode chamber 2, enters the electrode chamber 1 from the electrolyte inlet 8, flows out from the electrolyte outlet 9, and circulates the process by using a peristaltic pump, wherein the dosage of the cation-storage electrolyte is 100 mL; the feed liquid is 10 g/L NaCl solution, the first feed liquid chamber is filled with the feed liquid, the feed liquid inlet and outlet are sealed, the feed liquid is used as concentrated water and is kept still, and the using amount is about 10 mL; the feed liquid in the second feed liquid chamber was circulated by a peristaltic pump in an amount of 50 mL, and the recovery rate was set to 50/(50+10) =0.833 as water for desalination.
(3) The constant potential charging mode is adopted, the charging potential is 1.2V, the change process of the salt content of the desalinated water is recorded, and the result is shown in figure 9.
Comparative example 2
(1) The flow desalination cell structure shown in fig. 5 was assembled, but the second feed chamber was not filled with an ion exchange mixed bed.
(2) Through a proper pipeline connection method, cation-storage electrolyte enters the electrode chamber 2 from the electrolyte inlet 10, flows out from the electrolyte outlet 11 after filling the electrode chamber 2, enters the electrode chamber 1 from the electrolyte inlet 8, flows out from the electrolyte outlet 9, and circulates the process by using a peristaltic pump, wherein the dosage of the cation-storage electrolyte is 100 mL; the feed liquid is 10 g/L NaCl solution, the first feed liquid chamber is filled with the feed liquid, the feed liquid inlet and outlet are sealed, the feed liquid is used as concentrated water and is kept still, and the using amount is about 10 mL; the feed liquid in the second feed liquid chamber was circulated by a peristaltic pump in an amount of 50 mL, and the recovery rate was set to 50/(50+10) =0.833 as water for desalination.
(3) The constant potential charging mode is adopted, the charging potential is 1.2V, the change process of the salt content of the desalinated water is recorded, and the result is shown in figure 9.
As can be seen from FIG. 9, during potentiostatic operation, the salt content of the feed solutions of example 2 and comparative example 2 both decreased, and when the salt content was below 5500 mg/L, the salt content decrease rate of comparative example 2 began to decrease, while the salt content decrease of example 2 remained stable; the salt content of the same feed liquid is reduced from 10000 mg/L to 500 mg/L, the time consumed by comparative example 2 is 318 min, the time consumed by example 2 is 474 min, and the desalting rate of example 2 is higher.
Example 3
(1) The structure of the flow desalination cell shown in fig. 1 was assembled.
(2) 35 g/L, 20 g/L, 10 g/L, 9 g/L, 8 g/L, 7 g/L, 6 g/L and 5 g/L of NaCl solution are respectively prepared as feed liquid, the feed liquid chambers are respectively filled with the NaCl solution with the concentration gradient, the two electrode chambers are respectively filled with anion electrolyte and cation electrolyte, the electrolyte and the feed liquid are kept still, two ends of each electrode are connected with a double potentiostat, the internal resistance of the battery is analyzed by an impedance spectroscopy analysis method, and specific results are shown in Table 2.
(3) Selecting 35 g/L NaCl solution as feed liquid for desalination, wherein the dosage of the feed liquid is 50 mL, and circularly conveying the feed liquid by using a peristaltic pump; 100 mL of each of the anion storage electrolyte and the cation storage electrolyte are circularly conveyed by a peristaltic pump; adopting constant current charge and discharge mode, setting current density at 0.5 mA/cm2、1.0 mA/cm2、1.5 mA/cm2、2.0 mA/cm2(the current is respectively 3.5 mA, 7.0 mA, 10.5 mA and 14 mA), the charging and discharging time is 1 h respectively, and the charging and discharging potential change during the recording period. The above steps were repeated with 20 g/L, 10 g/L, and 5 g/L NaCl solution, and the results are shown in FIG. 10.
Comparative example 3
(1) The flow desalination cell structure shown in fig. 1 was assembled, but the feed liquid chamber 3 was not filled with an ion exchange mixed bed.
(2) 35 g/L, 20 g/L, 10 g/L, 9 g/L, 8 g/L, 7 g/L, 6 g/L and 5 g/L of NaCl solution are respectively prepared as feed liquid, the feed liquid chambers are respectively filled with the NaCl solution with the concentration gradient, the two electrode chambers are respectively filled with anion electrolyte and cation electrolyte, the electrolyte and the feed liquid are kept still, two ends of each electrode are connected with a double potentiostat, the internal resistance of the battery is analyzed by an impedance spectroscopy analysis method, and specific results are shown in Table 2.
(3) Selecting 35 g/L NaCl solution as feed liquid for desalination, wherein the dosage of the feed liquid is 50 mL, and circularly conveying the feed liquid by using a peristaltic pump; 100 mL of each of the anion storage electrolyte and the cation storage electrolyte are circularly conveyed by a peristaltic pump; adopting constant current charge and discharge mode, setting current density at 0.5 mA/cm2、1.0 mA/cm2、1.5 mA/cm2、2.0 mA/cm2(the current is respectively 3.5 mA, 7.0 mA, 10.5 mA and 14 mA), the charging and discharging time is 1 h respectively, and the charging and discharging potential change during the recording period. The above steps were repeated with 20 g/L, 10 g/L, and 5 g/L NaCl solution, and the results are shown in FIG. 10.
TABLE 2
Salt content (mg/L) Comparative example 3 internal resistance (omega) EXAMPLE 3 internal resistance (omega)
35000 10.7 13.0
20000 13.3 14.5
10000 16.1 16.3
9000 17.5 17.1
8000 18.3 17.2
7000 18.9 17.7
6000 20.0 17.8
5000 21.8 18.2
The data of comparative example 3 and example 3 were analyzed. According to Table 2, as the salt content of the feed liquid is reduced, the internal resistance of the desalination cell in comparative example 3 and the internal resistance of the desalination cell in example 3 are increased, and when the concentration is not lower than 10 g/L, the internal resistance of the desalination cell in comparative example 3 is lower than that of example 3; when the concentration is less than 10 g/L, the internal resistance of the desalting cell in comparative example 3 is higher than that in example 3. According to FIG. 10, when the concentration is not less than 10 g/L, the charging potential of example 3 is slightly higher than that of comparative example 3, and the discharging potential of example 3 is slightly lower than that of comparative example 3, so that the energy consumption of example 3 is slightly higher than that of comparative example 3; when the concentration is less than 10 g/L, the charge potential is lower and the discharge potential is higher in the example than in comparative example 3, and thus the energy consumption of example 3 is lower than in comparative example 3. According to the analysis results of comparative example 3 and example 3, when the feed is the NaCl solution of 10 g/L or more, the effect of the ion exchange mixed bed on the reduction of the internal resistance of the desalination cell is insignificant, and at this time, the conductivity of the NaCl solution itself is high, and the contribution of the ion exchange mixed bed to the conductivity of the desalination cell is insignificant, so the ion exchange mixed bed is not suitable for the high salt content feed.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.

Claims (10)

1. The device for enhancing the performance of the desalination cell by using the ion exchange mixed bed is characterized by comprising at least two electrode chambers for filling electrolyte, a plurality of groups of feed liquid chambers which are connected in parallel and used for filling feed liquid and at least two diaphragms, wherein each electrode chamber comprises at least one electrolyte inlet, at least one electrolyte outlet and at least one electrode, each feed liquid chamber is a feed liquid flowing area and comprises at least one feed liquid inlet and at least one feed liquid outlet, the ion exchange mixed bed is filled in each feed liquid chamber, the ion exchange mixed bed is formed by mixing an anion exchanger and a cation exchanger, each feed liquid chamber is arranged between every two adjacent electrode chambers, and the diaphragms are respectively arranged between each feed liquid chamber and between each feed liquid chamber and each electrode chamber.
2. The apparatus of claim 1, wherein the mass ratio of the anion exchanger to the cation exchanger is A: b, wherein A is more than or equal to 0 and less than or equal to 10000, B is more than or equal to 0 and less than or equal to 10000, and A and B are not 0 at the same time; the anion exchanger is at least one of strong base type anion exchange resin, weak base type anion exchange resin, amphoteric ion exchange resin, anion exchange fiber and amphoteric ion exchange fiber, and the cation exchanger is at least one of strong acid type cation exchange resin, weak acid type cation exchange resin and cation exchange fiber.
3. The apparatus of claim 1, wherein the ion exchange mixed bed is a mixed ion exchange bed in which a chlorine type anion exchange resin and a sodium type cation exchange resin are mixed in a mass ratio of 1.5: 1.
4. The apparatus of claim 1, wherein the electrode is a composite electrode formed of at least one material selected from graphite felt, graphite paper, carbon paper, activated carbon fiber, carbon felt, carbon cloth, glassy carbon, magnesium, aluminum, zinc, iron, tin, lead, copper, silver, bismuth, platinum, and gold.
5. The apparatus of claim 1, wherein the membrane is at least one of a homogeneous cation exchange membrane, a homogeneous anion exchange membrane, a heterogeneous cation exchange membrane, a heterogeneous anion exchange membrane, a ceramic membrane, and an organic polymer membrane.
6. The apparatus as claimed in claim 1, wherein the feed solution is seawater, brackish water, waste water containing heavy metal ions, sewage, or artificially prepared solution containing charged particles, and the electrolyte is at least one of an anion-storage electrolyte and a cation-storage electrolyte, and the anion in the anion-storage electrolyte does not participate in oxygen reduction reaction, and electron gain and loss are generated by cations or electroneutralics, including Zn2+、Fe2+/Fe3 +、Sn2+/Sn4+、Pb2+、Cu2+/Cu+、Ag+、Ni2+、Co2+/Co3+、Mn2+/Mn3+/Mn4+/Mn7+、Cr2+/Cr3+、Ti3+/Ti4+Or V2 +/V3+/V4+/V5+Metal ions, ions formed by complexing the metal ions with various complexing agents, 4-hydroxy-piperidinol oxide or methyl viologen; the cation in the cation storage electrolyte does not participate in redox reaction, and electron gain and loss are generated by anions or electric neutral substances, including Br2/Br-、I-/I3 -、[Fe(CN)6]4-/[Fe(CN)6]3-A sulfide, a polysulfide, a quinone derivative, an alloxazine derivative, a flavin derivative, a viologen derivative or a ferrocene derivative.
7. The apparatus as claimed in claim 6, wherein the electrolyte further comprises a conductive agent, the conductive agent is NaCl, NH4Cl、KCl、Na2SO4、NaNO3At least one of sodium acetate and sodium citrate.
8. The apparatus as claimed in claim 7, wherein the concentration of the feed liquid is 0.002-2 mol/L, the concentration of the electrolyte is 0.001-10 mol/L, and the content of the conductive agent is 0-2 mol/L.
9. The method for enhancing the performance of a desalination cell by using an ion exchange mixed bed based on the device of claim 1, is characterized by comprising the following steps: the apparatus of claim 1, wherein the feed liquid is circulated and injected into the feed liquid chamber, the electrolyte is circulated and injected into the electrode chamber, the desalination cell is operated to desalinate the feed liquid, and the operation is stopped when the feed liquid reaches a preset conductivity value.
10. The use of the apparatus of claim 1 in the fields of desalination of sea water and brackish water, removal of heavy metal ions from water.
CN202110654139.8A 2021-06-11 2021-06-11 Device and method for enhancing performance of desalination cell by using ion exchange mixed bed Pending CN113426495A (en)

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JPH11313699A (en) * 1998-02-05 1999-11-16 Japan Organo Co Ltd Desalting method
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JP2000301156A (en) * 1999-04-19 2000-10-31 Japan Organo Co Ltd Electric deionized water making apparatus and water passing method using the same
CN1769193A (en) * 2005-09-12 2006-05-10 张贵清 Electric deionisation method and apparatus for producing superpure water using separation bed
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