1. A multi-stage electrodeionization device, comprising: n processing units which are sequentially connected in series are arranged according to the flow direction of the desalted liquid, wherein N is a natural number more than 1;

for any processing unit, the front-stage processing unit of the processing unit is connected in series with the front-stage waterway of the processing unit, and the rear-stage processing unit of the processing unit is connected in series with the rear-stage waterway of the processing unit;

each treatment unit comprises a pair of electrode pairs and at least one bipolar membrane between two electrodes forming the electrode pairs, and the total amount of the same type of ion exchange groups in all the bipolar membranes in one treatment unit is defined as an effective value of the treatment unit;

the effective value of any processing unit is not less than that of any post-processing unit, and the effective value of at least one processing unit is greater than that of at least one post-processing unit.

2. The multi-stage electrodeionization apparatus of claim 1, wherein: the total amount of the similar ion exchange groups is at least one of the total amount of the cation exchange groups in the cation exchange membrane and the total amount of the anion exchange groups in the anion exchange membrane.

3. The multi-stage electrodeionization apparatus of claim 1, wherein: the total amount of cation exchange groups per square centimeter of cation exchange membrane of at least one bipolar membrane in at least one treatment unit is greater than or equal to the total amount of anion exchange groups per square centimeter of anion exchange membrane.

4. The multi-stage electrodeionization apparatus of claim 3, wherein: the total amount of cation exchange groups per square centimeter of cation exchange membrane of at least one bipolar membrane in at least one treatment unit is 1.05-10 times of the total amount of anion exchange groups per square centimeter of anion exchange membrane.

5. The multi-stage electrodeionization apparatus of claim 4, wherein: the total amount of cation exchange groups per square centimeter of cation exchange membrane of at least one bipolar membrane in at least one treatment unit is 2.5-4 times of the total amount of anion exchange groups per square centimeter of anion exchange membrane.

6. The multi-stage electrodeionization apparatus of claim 1, wherein: the thicknesses of the cation exchange membrane and the anion exchange membrane of each bipolar membrane in any one treatment unit are respectively not less than the thicknesses of the corresponding cation exchange membrane and anion exchange membrane in each bipolar membrane in any subsequent treatment unit;

at least one thickness of the cation exchange membrane or the thickness of the anion exchange membrane of each bipolar membrane in at least one treatment unit is larger than the thickness of the corresponding cation exchange membrane or anion exchange membrane of each bipolar membrane in any subsequent treatment unit at the later stage.

7. The multi-stage electrodeionization apparatus of claim 1, wherein: the cation exchange membrane in the bipolar membrane is formed by compounding a plurality of proton cation exchange membranes.

8. The multi-stage electrodeionization apparatus of claim 1, wherein: the anion exchange membrane in the bipolar membrane is formed by compounding a plurality of sub-anion exchange membranes.

9. The multi-stage electrodeionization apparatus of claim 1, wherein: the thickness of the cation exchange membrane dry membrane sheet and the thickness of the anion exchange membrane dry membrane sheet which form the same bipolar membrane are respectively 0.1 mm-5 mm and 0.1 mm-5 mm.

10. The multi-stage electrodeionization apparatus of claim 9, wherein: the thickness of the cation exchange membrane dry membrane sheet and the thickness of the anion exchange membrane dry membrane sheet which form the same bipolar membrane are respectively 0.5 mm-4 mm and 0.5 mm-4 mm.

11. The multi-stage electrodeionization apparatus of any one of claims 1 to 10, wherein: the number of bipolar membranes in any one treatment unit is not less than that in any subsequent post-treatment unit, and the number of bipolar membranes in at least one treatment unit is greater than that in at least one subsequent post-treatment unit.

12. The multi-stage electrodeionization apparatus of any one of claims 1 to 10 wherein: a pair of electrode pairs in which at least one processing unit is present includes a porous electrode.

13. The multi-stage electrodeionization apparatus of any one of claims 1 to 11, wherein: the porous electrode is provided with a porous material.

14. The multi-stage electrodeionization apparatus of claim 13, wherein: the porous material has a porous structure with pore sizes between 0.5 and 50 nanometers.

15. The multi-stage electrodeionization apparatus of claim 13, wherein: the porous material is one or more of activated carbon, carbon black, carbon nanotubes, graphite, carbon fibers, carbon cloth, carbon aerogel, metal powder, metal oxides and conductive polymers.

16. The multi-stage electrodeionization apparatus of claim 13, wherein: the porous electrode is also provided with a current collector which is laminated with the porous material.

17. The multi-stage electrodeionization apparatus of claim 16, wherein: the material of the current collector is selected from one or more of metal, metal alloy, graphite, graphene, carbon nanotube and conductive plastic.

18. The multi-stage electrodeionization apparatus of claim 13, wherein: the porous electrode is also provided with an ion exchange membrane, and the porous material and the ion exchange membrane are arranged in a stacked mode.

19. The multi-stage electrodeionization apparatus of claim 18 wherein: the ion exchange membrane in the porous electrode is an anion exchange membrane or a cation exchange membrane.

20. The multi-stage electrodeionization apparatus of claim 19, wherein:

a porous electrode having a cation exchange membrane, defined as an anode membrane electrode; the other porous electrode has an anion exchange membrane, defined as a negative membrane electrode;

the anion-exchange membrane in the bipolar membrane closest to the anode electrode faces the anode electrode;

the cation-exchange membrane in the bipolar membrane closest to the cathode electrode faces the cathode electrode.

21. A water treatment apparatus characterized by: having a multi-stage electrodeionization apparatus as claimed in any one of claims 1 to 20.

Background

A novel household water purifier uses an electrodeionization technology and is based on the principle of ion exchange. Ion exchange is one of the methods for extracting or removing ions from a liquid stream using ion exchange materials. Currently, ion exchange has been widely used for water purification and softening; desalting seawater and brackish water; refining and decolorizing solution (such as sugar solution). Ion exchange materials another important form, in addition to the widely used ion exchange resin beads or powders, is an ion exchange membrane, which is a thin film made of a high molecular material containing ion exchange groups. Those containing all cation exchange groups are called cation exchange membranes (positive membranes), and those containing all anion exchange groups are called anion exchange membranes (negative membranes).

In the prior art multi-stage electrodeionization device, the treatment performance of each stage of treatment unit on liquid is basically consistent. The device of this kind of structure, after multistage electrodeionization device long-time operation, preceding stage membrane stack performance decay is extremely fast, greatly influences the income water quality and the life of back stage membrane stack to influence multistage electrodeionization device's wholeness ability, system water rate is low.

Therefore, it is necessary to provide a multi-stage electrodeionization device and a water treatment apparatus thereof to overcome the deficiencies of the prior art.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a multistage electrodeionization device and water treatment equipment with the same, which can solve the problem that the performance of a preceding stage membrane stack is rapidly reduced due to single structure of a bipolar membrane stack in the prior art, and improve the whole water preparation rate by improving the desalination rate and the water preparation rate of the preceding stage membrane stack.

The object of the invention is achieved by the following technical measures.

Providing a multi-stage electrodeionization device, wherein N processing units which are sequentially connected in series are arranged according to the flow direction of desalted liquid, and N is a natural number more than 1;

for any processing unit, the front-stage processing unit of the processing unit is connected in series with the front-stage waterway of the processing unit, and the rear-stage processing unit of the processing unit is connected in series with the rear-stage waterway of the processing unit;

each treatment unit comprises a pair of electrode pairs and at least one bipolar membrane between two electrodes forming the electrode pairs, and the total amount of the same type of ion exchange groups in all the bipolar membranes in one treatment unit is defined as an effective value of the treatment unit;

the effective value of any processing unit is not less than that of any post-processing unit, and the effective value of at least one processing unit is greater than that of at least one post-processing unit.

Preferably, in the multi-stage electrodeionization device, the total amount of the like ion exchange groups is at least one of the total amount of cation exchange groups in the cation exchange membrane and the total amount of anion exchange groups in the anion exchange membrane.

Preferably, in the multi-stage electrodeionization device, the total amount of cation exchange groups per square centimeter of cation exchange membrane of at least one bipolar membrane in at least one treatment unit is greater than or equal to the total amount of anion exchange groups per square centimeter of anion exchange membrane.

Preferably, in the multi-stage electrodeionization device, the total amount of cation exchange groups per square centimeter of cation exchange membrane of at least one bipolar membrane in at least one treatment unit is 1.05-10 times of the total amount of anion exchange groups per square centimeter of anion exchange membrane.

Preferably, in the multistage electrodeionization device, the total amount of cation exchange groups per square centimeter of cation exchange membrane of at least one bipolar membrane in at least one treatment unit is 2.5-4 times that of anion exchange groups per square centimeter of anion exchange membrane.

Preferably, in the multistage electrodeionization device, the thicknesses of the cation exchange membrane and the anion exchange membrane of each bipolar membrane in any one treatment unit are respectively not less than the thicknesses of the corresponding cation exchange membrane and anion exchange membrane of each bipolar membrane in any subsequent post-treatment unit;

at least one thickness of the cation exchange membrane or the thickness of the anion exchange membrane of each bipolar membrane in at least one treatment unit is larger than the thickness of the corresponding cation exchange membrane or anion exchange membrane of each bipolar membrane in any subsequent treatment unit at the later stage.

Preferably, in the multistage electrodeionization apparatus, the cation exchange membrane of the bipolar membrane is a composite of a plurality of cation exchange membranes.

Preferably, in the multistage electrodeionization apparatus, the anion exchange membrane of the bipolar membrane is formed by combining a plurality of sub-anion exchange membranes.

Preferably, in the multi-stage electrodeionization device, the thickness of the cation exchange membrane dry membrane sheet and the thickness of the anion exchange membrane dry membrane sheet which form the same bipolar membrane are respectively 0.1mm to 5mm and 0.1mm to 5 mm.

Preferably, in the multi-stage electrodeionization device, the thickness of the cation exchange membrane dry membrane sheet and the thickness of the anion exchange membrane dry membrane sheet which form the same bipolar membrane are respectively 0.5mm to 4mm, and 0.5mm to 4 mm.

Preferably, in the above multistage electrodeionization device, the number of bipolar membranes in any one treatment unit is not less than the number of bipolar membranes in any subsequent treatment unit, and the number of bipolar membranes in at least one treatment unit is greater than the number of bipolar membranes in at least one subsequent treatment unit.

Preferably, the multi-stage electrodeionization apparatus comprises a porous electrode in a pair of electrode pairs in which at least one treatment unit is present.

Preferably, in the multi-stage electrodeionization device, the porous electrode is provided with a porous material.

Preferably, in the multi-stage electrodeionization device, the porous material has a porous structure with a pore size of 0.5 to 50 nm.

Preferably, in the above multistage electrodeionization device, the porous material is one or more of activated carbon, carbon black, carbon nanotubes, graphite, carbon fibers, carbon cloth, carbon aerogel, metal powder, metal oxide and conductive polymer.

Preferably, in the multistage electrodeionization device, the porous electrode further includes a current collector, and the current collector is stacked on the porous material.

Preferably, in the above multistage electrodeionization device, the material of the current collector is selected from one or more of metals, metal alloys, graphite, graphene, carbon nanotubes and conductive plastics.

Preferably, in the multistage electrodeionization device, the porous electrode is further provided with an ion exchange membrane, and the porous material and the ion exchange membrane are stacked.

Preferably, in the multistage electrodeionization device, the ion exchange membrane in the porous electrode is an anion exchange membrane or a cation exchange membrane.

Preferably, in the above multistage electrodeionization apparatus, one of the porous electrodes has a cation exchange membrane, defined as an anode membrane electrode; the other porous electrode has an anion exchange membrane, defined as a negative membrane electrode;

the anion-exchange membrane in the bipolar membrane closest to the anode electrode faces the anode electrode;

the cation-exchange membrane in the bipolar membrane closest to the cathode electrode faces the cathode electrode.

The invention provides a multistage electrodeionization device, which is provided with N processing units which are sequentially connected in series according to the flow direction of desalted liquid, wherein N is a natural number more than 1; for any processing unit, the front-stage processing unit of the processing unit is connected in series with the front-stage waterway of the processing unit, and the rear-stage processing unit of the processing unit is connected in series with the rear-stage waterway of the processing unit; each treatment unit comprises a pair of electrode pairs and at least one bipolar membrane between two electrodes forming the electrode pairs, and the total amount of the same type of ion exchange groups in all the bipolar membranes in one treatment unit is defined as an effective value of the treatment unit; the effective value of any processing unit is not less than that of any post-processing unit, and the effective value of at least one processing unit is greater than that of at least one post-processing unit. This multistage electrodeionization device, it is high through setting up the desalination at the water route front end, the preceding stage processing unit that the system water yield is big, improve the income water quality and the life of rear stage processing unit by a wide margin, solved multistage electrodeionization device long-time operation back, the fast problem of preceding stage processing unit performance decay, and play the guard action to the rear stage processing unit, thereby improve multistage electrodeionization device's whole desalination and system water yield, the life of extension complete machine, it is extravagant to reduce water resources, can reduce the filter core size simultaneously, make equipment structure compact, be applicable to industry and domestic water and handle.

It is another object of the present invention to avoid the disadvantages of the prior art and to provide a water treatment apparatus having a multi-stage electrodeionization device. This water treatment facilities can avoid among the prior art because bipolar membrane processing unit single structure, preceding stage processing unit's the fast problem of performance decline, through the desalination and the system water rate that improve preceding stage processing unit to improve multistage electrodeionization device's whole system water rate, reduce water wasting of resources, can reduce filter core size simultaneously, make equipment structure compact, be applicable to industry and domestic water and handle.

The object of the invention is achieved by the following technical measures.

A water treatment apparatus is provided having a multi-stage electrodeionization device.

The invention provides water treatment equipment which is provided with a multi-stage electrodeionization device. The multi-stage electrodeionization device is provided with N processing units which are sequentially connected in series according to the flow direction of desalted liquid, wherein N is a natural number more than 1; for any processing unit, the front-stage processing unit of the processing unit is connected in series with the front-stage waterway of the processing unit, and the rear-stage processing unit of the processing unit is connected in series with the rear-stage waterway of the processing unit; each treatment unit comprises a pair of electrode pairs and at least one bipolar membrane between two electrodes forming the electrode pairs, and the total amount of the same type of ion exchange groups in all the bipolar membranes in one treatment unit is defined as an effective value of the treatment unit; the effective value of any processing unit is not less than that of any post-processing unit, and the effective value of at least one processing unit is greater than that of at least one post-processing unit. This water treatment facilities with multistage electrodeionization device, it is high through setting up the desalination at the water route front end, the preceding stage processing unit that the system water yield is big, improve the income water quality and the life of back stage processing unit by a wide margin, the long-time back of moving of multistage electrodeionization device has been solved, the fast problem of preceding stage processing unit performance decay, and play the guard action to back stage processing unit, thereby improve multistage electrodeionization device's whole desalination and system water yield, the life of extension complete machine, it is extravagant to reduce water resources, can reduce the filter core size simultaneously, make equipment structure compact, be applicable to industry and domestic water treatment.

Drawings

The invention is further illustrated by means of the attached drawings, the content of which is not in any way limiting.

FIG. 1 is a schematic diagram of a bipolar membrane.

Fig. 2 is a schematic structural view of a multistage electrodeionization apparatus of embodiment 1 of the present invention.

FIG. 3 is a schematic diagram of a desalination state of a treatment unit.

FIG. 4 is a schematic illustration of the regeneration state of the processing unit of FIG. 3.

FIG. 5 shows the results of the experiment on the long-term desalting performance of the treating unit A in example 5 of the present invention.

FIG. 6 shows the results of the experiment on the long-term desalting performance of the treating unit B in example 5 of the present invention.

FIG. 7 shows the results of the experiment on the long-term desalting performance of the treating unit C in example 5 of the present invention.

FIG. 8 shows the results of the experiment on the long-term desalting performance of the treating unit D in example 5 of the present invention.

FIG. 9 is a schematic view showing the desalination state of the treatment unit of the multistage electrodeionization apparatus of example 11 of the present invention.

FIG. 10 is a schematic view showing the desalination state of the treatment unit of the multistage electrodeionization apparatus of example 11 of the present invention.

FIG. 11 is a schematic view showing the desalination state of the treatment unit of the multistage electrodeionization apparatus of example 12 of the present invention.

In fig. 1 to 11, there are included:

electrode 100, electrode 200,

A bipolar membrane 300, a cation exchange membrane 310, an anion exchange membrane 320,

Processing units 61, 62, 63,

A current collector 130, a porous material 110, an anion exchange membrane 120 of a porous electrode,

A current collector 230, a porous material 210, a cation exchange membrane 220 of the porous electrode.

Detailed Description

The invention is further illustrated by the following examples.

Reference herein to "deionization" is to the removal of ions from the liquid to be treated, including anions and cations in various valence states. In most cases, "deionization" has the same meaning as "desalination". In some cases, deionization is also referred to as demineralization.

Example 1.

A multi-stage electrodeionization apparatus, as shown in FIG. 1, is provided with N treatment units connected in series in sequence in the direction of flow of desalted liquid, N being a natural number greater than 1. The number of N can be set and selected according to needs, such as 2 to 100, and can also be set to other needed numbers.

For any one processing unit, a waterway (also referred to as a former waterway) connected in series in front of the processing unit is a former processing unit of the processing unit, and a waterway (also referred to as a latter waterway) connected in series behind the processing unit is a latter processing unit of the processing unit.

Each treatment unit comprises a pair of electrode pairs and at least one bipolar membrane between two electrodes forming the electrode pairs, and the total amount of the same type of ion exchange groups in all the bipolar membranes in one treatment unit is defined as the effective value of the treatment unit.

The effective value of any processing unit is not less than that of any post-processing unit, and the effective value of at least one processing unit is greater than that of at least one post-processing unit.

In the multi-stage electrodeionization device of the present embodiment, the treatment unit is the smallest unit capable of performing water purification treatment, and includes at least one pair of electrodes and a plurality of bipolar membranes disposed between the two electrodes. The processing unit, the external pipeline, the power supply and the like constitute an electrodeionization device, which is a device capable of independently purifying water.

As shown in fig. 1, the bipolar membrane 300 is composed of a cation exchange membrane 310 and an anion exchange membrane 320 which are combined together, and there is no flow channel between the cation exchange membrane 310 and the anion exchange membrane 320 which form the same bipolar membrane.

The term "in series" as used herein means that the flow direction of the effluent is determined based on the flow of the flow path. For example, if two process units are connected in series, the produced fluid from the flow channel of the previous process unit enters the flow channel of the next process unit.

The configuration of a multi-stage deionization apparatus shown in fig. 2 will be described as an example, the multi-stage deionization apparatus includes three processing units, i.e., a processing unit 61, a processing unit 62, and a processing unit 63, and the three processing units 61, 62, and 63 are connected in series. In desalination, a liquid flow first enters the processing unit 61 to be desalinated, a liquid produced from the processing unit 61 enters the processing unit 62 to be desalinated, a liquid produced from the processing unit 62 enters the processing unit 63 to be desalinated, and pure water is discharged after being desalinated by the processing unit 63.

Processing unit 61 is a preceding-stage processing unit with respect to processing unit 62, and processing unit 63 is a subsequent-stage processing unit; with respect to the processing unit 61, the processing unit 62 and the processing unit 63 are both post-stage processing units; similarly, the processing unit 61 and the processing unit 62 are both preceding-stage processing units with respect to the processing unit 63.

Two bipolar membranes 300 are contained in each processing unit in fig. 2, and it should be noted that the number of processing units constituting the multi-stage deionization apparatus is not limited to three in fig. 1, and may be set to other numbers as needed. The number of the bipolar membranes 300 contained in each processing unit may be the same or different, and may be three or another number, without being limited to the manner of fig. 2.

The working process of the processing unit is described by taking the processing unit at one stage as an example. As shown in fig. 3 and 4, the treatment unit is provided with an electrode 100, an electrode 200, and two bipolar membranes 300 between the electrode 100 and the electrode 200, each bipolar membrane 300 being composed of a cation exchange membrane and an anion exchange membrane that are combined together. The electrode can be a metal electrode such as a ruthenium yttrium electrode, a carbon electrode, a graphite electrode, a capacitance electrode, etc., and the bipolar membrane is a commercially available bipolar membrane. The desalting process of the treatment unit is shown in FIG. 3. When desalination is carried out for a while, reverse-polarity regeneration is required to release ions in water adsorbed on the bipolar membrane, as shown in FIG. 4. Different treatment units are connected in series to form the integral multi-stage electrodeionization device, and the principle that desalination or regeneration is respectively carried out in each treatment unit is the same in the desalination or regeneration process.

The cation exchange membrane contains cation exchange groups, and the anion exchange membrane contains anion exchange groups. The cation exchange group can adsorb positive salt ions in raw water and displace hydrogen ions, and the anion exchange group can adsorb negative salt ions in raw water and displace hydroxide ions. The higher the content of ion exchange groups in the bipolar membrane is, the stronger the bipolar membrane has the adsorption capacity on salt ions in raw water, so that the desalting capacity of the bipolar membrane is stronger.

The total amount of the same type of ion exchange groups in all the bipolar membranes in one treatment unit is defined as an effective value of the treatment unit, and the total amount of the same type of ion exchange groups is selected from at least one of the total amount of cation exchange groups in a cation exchange membrane and the total amount of anion exchange groups in an anion exchange membrane. One parameter index or two parameter indexes can be selected to be compared and judged at the same time, if the total amount of cation exchange groups in the cation exchange membrane is taken as a comparison parameter, the total amounts of the cation exchange groups of all the bipolar membranes in the treatment units at the front stage and the rear stage are compared; if the total amount of the anion exchange groups in the anion exchange membrane is taken as a comparison parameter, comparing the total amount of the anion exchange groups of all the bipolar membranes in the treatment units at the front stage and the rear stage; if the total amount of the cation exchange groups in the cation exchange membrane and the total amount of the anion exchange groups in the anion exchange membrane are used as comparison parameters, the total amounts of the cation exchange groups of all bipolar membranes at the previous and next stages are compared, and meanwhile, the total amounts of the anion exchange groups of all bipolar membranes in the treatment units at the previous and next stages are compared, and a comparison conclusion is obtained under the condition that the total amounts of the cation exchange groups and the anion exchange groups in the treatment units at the previous and next stages are simultaneously satisfied.

The effective value of any one processing unit is not less than that of any subsequent post-processing unit, and the effective value of at least one processing unit is greater than that of at least one subsequent post-processing unit. When the total ion exchange group amount of the front-stage treatment unit is larger than that of the rear-stage treatment unit, the front-stage treatment unit has higher desalination rate than that of the rear-stage treatment unit, and the water production amount is larger.

Therefore, the multi-stage electrodeionization device has high total desalination amount at the front end of the water channel, and correspondingly, the water production amount of the front treatment unit is large. The preceding stage processing unit that the system water yield is big improves the income water quality and the life of back level processing unit by a wide margin, has solved multistage electrodeionization device long-time operation back, the fast problem of preceding stage processing unit performance decay to play the guard action to back level processing unit, thereby improve multistage electrodeionization device's whole desalination and system water rate, the life of extension complete machine, reduce water resource waste, can reduce the filter core size simultaneously, make equipment structure compact, be applicable to industry and domestic water treatment.

Example 2.

A multi-stage electrodeionization device is sequentially provided with a plurality of treatment units according to the flow direction of desalination, each treatment unit contains the same number of bipolar membranes, and the cation exchange membranes of each bipolar membrane face to electrodes with the same polarity.

The effective value in each preceding-stage processing unit is larger than that of the succeeding-stage processing unit adjacent thereto in terms of the flow direction of the desalted water.

The multi-stage electrodeionization device gradually reduces the total salt treated by each stage of treatment unit along the desalting direction. The multistage electrodeionization device ensures that the water production amount of the treatment unit is larger when the treatment unit is closer to the front side through the effective value of the treatment unit. The water inlet quality and the service life of the rear-stage treatment unit are greatly improved, the problem that the performance of the front-stage treatment unit is quickly attenuated after the multi-stage electrodeionization device runs for a long time is solved, and the rear-stage treatment unit is protected, so that the overall desalination rate and water production rate of the multi-stage electrodeionization device are improved, the service life of the whole machine is prolonged, the waste of water resources is reduced, the size of a filter element can be reduced, the equipment is compact in structure, and the multi-stage electrodeionization device is suitable for industrial and domestic water treatment.

In this embodiment, the bipolar membranes are provided in the same number for each treatment unit. In practice, the number of bipolar membranes arranged in the front and rear stages may be different.

Example 3.

A multi-stage electrodeionization apparatus having the same other features as in example 1 or 2 except that: the total amount of cation exchange groups per square centimeter of cation exchange membrane of at least one bipolar membrane in at least one treatment unit is greater than or equal to the total amount of anion exchange groups per square centimeter of anion exchange membrane. Generally, to maintain equilibrium, the total amount of cation exchange groups per square centimeter of cation exchange membrane in a conventional bipolar membrane is equal to the total amount of anion exchange groups per square centimeter of anion exchange membrane.

However, the bipolar membrane with the total amount of cation exchange groups per square centimeter of cation exchange membrane being larger than the total amount of anion exchange groups per square centimeter of anion exchange membrane is adopted as part of the bipolar membrane in the treatment unit, so that the long-term working performance of the bipolar membrane can be improved, and the condition that the treatment unit interrupts water production due to frequent electrode reversal regeneration is reduced.

In order to achieve a total amount of cation exchange groups per square centimeter of cation exchange membrane in the bipolar membrane cation exchange membrane that is greater than the total amount of anion exchange groups per square centimeter of anion exchange membrane, two approaches may be used. By the method, the total amount of cation exchange groups per square centimeter of cation exchange membrane is increased in the same bipolar membrane, the number of anions in the anion exchange membrane is kept unchanged, the long-term working performance of the bipolar membrane can be improved by the asymmetric bipolar membrane, and the condition that a treatment unit interrupts water production due to frequent electrode reversal regeneration is reduced. In the second mode, increasing both the total amount of cation exchange groups per square centimeter of cation exchange membrane and the total amount of anion exchange groups per square centimeter of anion exchange membrane in the same bipolar membrane can also improve the long-term performance of the bipolar membrane, but is less convenient than the first mode.

It should be noted that all of the processing units at the preceding stage may employ such an asymmetric bipolar membrane, or only some of the membranes may employ an asymmetric bipolar membrane. Generally, the effect is better when several processing units at the front end of the flow channel adopt the asymmetric bipolar membrane. The asymmetrical bipolar membrane can be arranged in part of the processing units, or can be arranged in all the processing units.

The multistage electrodeionization device of the embodiment can improve the overall desalination rate and the water production rate of the multistage electrodeionization device, prolong the service life of the whole machine, reduce water resource waste, reduce the size of a filter element, enable the equipment structure to be compact, and is suitable for industrial and domestic water treatment. The long-term working performance of the bipolar membrane can be improved, and the condition that a processing unit interrupts water production due to frequent reverse electrode regeneration is reduced.

Example 4.

A multi-stage electrodeionization apparatus having the same other features as in example 3 except that: the method is characterized in that the thicknesses of the cation exchange membrane and the anion exchange membrane of each bipolar membrane in any one treatment unit are respectively not less than the thicknesses of the corresponding cation exchange membrane and anion exchange membrane of each bipolar membrane in any subsequent post-treatment unit. And at least one of the thicknesses of the cation exchange membrane or the anion exchange membrane of each bipolar membrane in at least one treatment unit is larger than the thickness of the corresponding cation exchange membrane or anion exchange membrane of each bipolar membrane in any subsequent treatment unit at the later stage.

On the premise that the same membrane area and the same unit area have the same number of ion exchange groups, the thickness of the membrane is increased, and the number of the ion exchange groups in the ion exchange membrane can be correspondingly increased.

Therefore, the multistage electrodeionization device of the embodiment can improve the overall desalination rate and water production rate of the multistage electrodeionization device, prolong the service life of the whole machine, reduce water resource waste, and simultaneously reduce the size of the filter element, so that the device has a compact structure, and is suitable for industrial and domestic water treatment. The long-term working performance of the bipolar membrane can be improved, and the condition that a processing unit interrupts water production due to frequent reverse electrode regeneration is reduced.

Example 5.

A multi-stage electrodeionization apparatus having the same other features as in example 4 except that: the cation exchange membrane in the bipolar membrane is formed by compounding a plurality of proton cation exchange membranes. The anion exchange membrane in the bipolar membrane is formed by compounding a plurality of sub-anion exchange membranes.

The cation exchange membrane of the processing unit membrane can be formed by laminating a plurality of sub-cation exchange membranes. The anion exchange membrane of the same bipolar membrane can be formed by laminating a plurality of sub-anion exchange membranes. On the premise that the area of the membrane, the number of ion exchange groups contained in unit area and the thickness of each membrane are the same, the total amount of the ion exchange groups of the ion exchange membrane can be directly changed through the number of the superposed sub-ion exchange membranes.

In the embodiment, the pre-stage treatment units A, B, C, D were selected as the treatment units for salt rejection experiments, wherein,

the bipolar membrane A of the treatment unit A is formed by hot-pressing and laminating 1 piece of cation exchange membrane and 1 piece of anion exchange membrane; the bipolar membrane B of the treatment unit B is formed by hot-pressing and laminating 2 sheets of cation exchange membranes and 2 sheets of anion exchange membranes; the bipolar membrane C of the treatment unit C is formed by hot-pressing and laminating 1 piece of cation exchange membrane and 2 pieces of anion exchange membrane; the bipolar membrane D of the treatment unit D is formed by hot-pressing and attaching 2 sheets of cation exchange membranes and 1 sheet of anion exchange membranes; all bipolar membranes had a membrane area of 0.2m²All the cation exchanger and the anion exchange membrane have the same thickness. The experimental steps are as follows: the 4 kinds of treatment units were installed in the electrodeionization apparatus, and then 750ppm NaCl solution was introduced into the treatment units A, B, C, and D at a flow rate of 0.5L/min, and the NaCl solution was passed through at once, and the salt rejection rates of the 4 kinds of treatment units as a function of time were as shown in FIGS. 5 to 8. The scheme of the invention is a processing unit B and a processing unit D.

Long-term performance test results of the treatment unit: the salt rejection of treatment unit a decayed from 48% -52% to 38% -52% after 300 minutes and to 26% -43% after 900 minutes. The desalination rate of the treatment unit B is maintained above 80% in 1100 minutes and slowly decays to 70% -80% after 1200 minutes. The desalination rate of the treatment unit C decays from more than 70% to 65% -80% after 400 minutes, and slowly decays to 40% -60% after 1200 minutes. The salt rejection of the treatment unit D was maintained at 70% or more for 1700 minutes. According to experimental results, the bipolar membrane design of the treatment unit B and the treatment unit D in the scheme of the invention can achieve the best long-term desalting effect, namely the larger the total amount of ion exchange groups of all bipolar membranes per square centimeter of ion exchange membranes in the treatment unit is, the better the long-term desalting effect is; furthermore, the total amount of cation exchange groups of all bipolar membranes per square centimeter of cation exchange membranes in the treatment unit is larger than that of anion exchange groups per square centimeter of anion exchange membranes, and the long-term desalting effect is optimal.

The multistage electrodeionization device of this embodiment, it is high through setting up the desalination at the water route front end, make the big preceding stage processing unit of water yield, improve the income water quality and the life of rear stage processing unit by a wide margin, solved multistage electrodeionization device long-time operation back, the fast problem of preceding stage processing unit performance decay, and play the guard action to rear stage processing unit, thereby improve multistage electrodeionization device's whole desalination and system water yield, the life of extension complete machine, it is extravagant to reduce water resources, can reduce the filter core size simultaneously, make equipment structure compact, be applicable to industry and domestic water treatment.

Example 6.

A multi-stage electrodeionization apparatus having the same other features as any one of embodiments 1 to 5 except that: the total amount of cation exchange groups per square centimeter of cation exchange membrane of at least one bipolar membrane in at least one treatment unit is 1.05-10 times of the total amount of anion exchange groups per square centimeter of anion exchange membrane. Under the condition that the total amount of the anion and cation exchange groups of the bipolar membrane is in the proportion, the long-term desalting effect of the treatment unit is good, and the production cost can be controlled.

The multistage electrodeionization device of this embodiment, it is high through setting up the desalination at the water route front end, make the big preceding stage processing unit of water yield, improve the income water quality and the life of rear stage processing unit by a wide margin, solved multistage electrodeionization device long-time operation back, the fast problem of preceding stage processing unit performance decay, and play the guard action to rear stage processing unit, thereby improve multistage electrodeionization device's whole desalination and system water yield, the life of extension complete machine, it is extravagant to reduce water resources, can reduce the filter core size simultaneously, make equipment structure compact, be applicable to industry and domestic water treatment.

Example 7.

A multi-stage electrodeionization apparatus having the same other features as in example 1 except that: the total amount of cation exchange groups per square centimeter of cation exchange membrane of at least one bipolar membrane in at least one treatment unit is 2-5 times of the total amount of anion exchange groups per square centimeter of anion exchange membrane. Under the condition that the total amount of the anion and cation exchange groups of the bipolar membrane is in the proportion, the long-term desalting effect of the treatment unit is good, and the production cost can be effectively controlled.

The multistage electrodeionization device of this embodiment, it is high through setting up the desalination at the water route front end, make the big preceding stage processing unit of water yield, improve the income water quality and the life of rear stage processing unit by a wide margin, solved multistage electrodeionization device long-time operation back, the fast problem of preceding stage processing unit performance decay, and play the guard action to rear stage processing unit, thereby improve multistage electrodeionization device's whole desalination and system water yield, the life of extension complete machine, it is extravagant to reduce water resources, can reduce the filter core size simultaneously, make equipment structure compact, be applicable to industry and domestic water treatment.

Example 8.

A multi-stage electrodeionization apparatus having the same other features as in examples 1 to 7 except that: the thickness of the cation exchange membrane dry membrane sheet and the thickness of the anion exchange membrane dry membrane sheet which form the same bipolar membrane are respectively 0.1 mm-5 mm and 0.1 mm-5 mm. The thickness is the conventional specification of a commercial ion exchange membrane, the reasonable volume of the treatment unit can be controlled, and the water purification requirement is met.

The multistage electrodeionization device of this embodiment, it is high through setting up the desalination at the water route front end, make the big preceding stage processing unit of water yield, improve the income water quality and the life of rear stage processing unit by a wide margin, solved multistage electrodeionization device long-time operation back, the fast problem of preceding stage processing unit performance decay, and play the guard action to rear stage processing unit, thereby improve multistage electrodeionization device's whole desalination and system water yield, the life of extension complete machine, it is extravagant to reduce water resources, can reduce the filter core size simultaneously, make equipment structure compact, be applicable to industry and domestic water treatment.

Example 9.

A multi-stage electrodeionization apparatus having the same other features as in example 1 except that: the thickness of the cation exchange membrane dry membrane sheet and the thickness of the anion exchange membrane dry membrane sheet which form the same bipolar membrane are respectively 0.5 mm-4 mm and 0.5 mm-4 mm. The thickness is the conventional specification of a commercial ion exchange membrane, the reasonable volume of the treatment unit can be effectively controlled, and the requirement of water purification is met.

The multistage electrodeionization device of this embodiment, through set up the total height of desalination at the water route front end, make the big preceding stage processing unit of water yield, improve the income water quality and the life of rear stage processing unit by a wide margin, solved multistage electrodeionization device long-time operation back, the fast problem of preceding stage processing unit performance decay, and play the guard action to rear stage processing unit, thereby improve multistage electrodeionization device's whole desalination and system water yield, the life of extension complete machine, it is extravagant to reduce water resources, can reduce the filter core size simultaneously, make equipment structure compact, be applicable to industry and domestic water treatment.

Example 10.

A multi-stage electrodeionization apparatus having the same other features as in any one of embodiments 1 to 9 except that: the number of bipolar membranes in any one treatment unit is not less than that in any subsequent post-treatment unit, and the number of bipolar membranes in at least one treatment unit is greater than that in at least one subsequent post-treatment unit. By designing the flow passages in the treatment units at the front and rear stages, the flow passages of the treatment units at the front stage are more, and the treated water amount is more. The problem of multistage electrodeionization device after long-time operation, preceding stage treatment unit performance decay is fast is solved to play the guard action to the processing unit of back stage, thereby improve multistage electrodeionization device's whole desalination and system water rate, the life of extension complete machine, reduce water wasting of resources, can reduce filter core size simultaneously, make equipment structure compact, be applicable to industry and domestic water and handle.

Example 11.

A multi-stage electrodeionization apparatus having the same other features as in any one of embodiments 1 to 10 except that: at least one porous electrode is included in a pair of electrode sets.

The pair of electrode groups may be composed of two porous electrodes, or may be composed of one porous electrode and one common electrode. Common electrodes such as metal electrodes, titanium electrodes with ruthenium-yttrium coatings, ruthenium-yttrium electrodes, carbon electrodes, graphite electrodes, etc.

Among them, the porous electrode may be composed of a porous material, or a porous material and a current collector laminated, or a current collector, a porous material, and an ion exchange membrane laminated in this order. The ion exchange membrane is an anion exchange membrane or a cation exchange membrane, and when the ion exchange membrane is contained, the ion exchange membrane in the porous electrode is close to the bipolar membrane. The cation exchange membrane or the anion exchange membrane in the porous electrode can be flexibly selected according to actual needs.

The porous material may be any electrically conductive material having a large specific surface, e.g. a specific surface of more than 100m²Conductive material per gram. In some embodiments, the porous material is a hydrophobic, electrically conductive material. The porous material has a porous structure with pore sizes between 0.5 and 50 nanometers. The porous material can be an electric conductor prepared from one or more of activated carbon, carbon black, carbon nanotubes, graphite, carbon fibers, carbon cloth, carbon aerogel, metal powder (such as nickel), metal oxide (such as ruthenium oxide) and conductive polymer. In one embodiment, the porous material is a sheet or plate structure made of activated carbon and having a thickness in the range of 100 to 5000 micrometers, preferably 200 to 2,500 micrometers, and the pore size of the activated carbon sheet structure is between 0.5 to 20 nanometers, preferably mesoporousBetween 1 and 10 nm.

The use of porous electrodes can mitigate the risk of fouling of the filter element. Since the ion exchange membrane contains or is adsorbed with ion charge units, when the amount of ions at the porous electrode is insufficient to complete the desorption process, the excess charge on the electrode is buffered by releasing the ions in the ion exchange membrane to help complete the desorption process. In this way, the risk of fouling is greatly reduced.

The current collector is used to connect to a wire or power source, also referred to as a "current collector". The current collector is formed of one or more materials selected from the group consisting of metals, metal alloys, graphite, graphene, carbon nanotubes, and conductive plastics. The current collector may be in any suitable form such as a plate, mesh, foil or sheet. In some embodiments, the current collector may be made of a metal or metal alloy, suitable metals include titanium, platinum, iridium or rhodium, etc., preferably titanium, and suitable metal alloys may be stainless steel, etc. In other embodiments, the current collector may be made of a conductive carbon material, such as graphite, graphene, carbon nanotubes, and the like. In other embodiments, the current collector is made of a conductive plastic material, such as a polyolefin (e.g., polyethylene), and conductive carbon black or metal particles, etc., may be mixed therein. In some embodiments, the current collector is a sheet or plate-like structure and may have a thickness in the range of 50 micrometers to 5 millimeters. In some embodiments, the current collector and the porous electrode have substantially the same shape and/or size.

When the porosity and conductivity of the porous material are sufficient, the current collector may not be provided when the porous material itself functions as the current collector.

Taking an example of a switching unit as shown in fig. 9 and 10, the switching unit includes two switching units,

an electrode pair consisting of a pair of porous electrodes 100, 200, which, due to the two porous electrodes, constitute a characteristic electrode group;

two bipolar membranes 300 arranged between the electrode pairs, wherein each bipolar membrane 300 is composed of a cation exchange membrane 310 and an anion exchange membrane 320 which are attached together, no flow channel is arranged between the cation exchange membrane 310 and the anion exchange membrane 320 which form the same bipolar membrane 300, and the arrangement modes of the two bipolar membranes 300 are the same;

and a flow channel formed between the electrode and the membrane stack or between the membrane stack and the membrane stack.

In the present embodiment, the porous electrode 100 is formed by laminating the current collector 130 and the porous material 110, and the porous electrode 100 is a cathode film electrode. The porous electrode 200 is formed by sequentially laminating a current collector 230 and a porous material 210, and the porous electrode 200 is an anode membrane electrode. The porous electrode can be formed by laminating and clamping a current collector and a porous material together without using a binder; or may be fixed by thermal bonding or bonded by an adhesive.

The cation exchange membrane or the anion exchange membrane in the porous electrode can be flexibly selected according to actual needs.

The bipolar membrane 300 is composed of a cation exchange membrane 310 and an anion exchange membrane 320 which are attached together, and the cation exchange membrane 310 and the anion exchange membrane 320 which form the same bipolar membrane are clamped tightly without a binder; the cation exchange membrane 310 and the anion exchange membrane 320 may be formed by thermal lamination. There is no flow channel between the cation exchange membrane 310 and the anion exchange membrane 320, and a flow channel is formed between the bipolar membrane or between the bipolar membrane and the electrode. The bipolar membranes sold in the market can be used as the bipolar membranes in the scheme, and the details are not repeated.

In this embodiment, there are two bipolar membranes 300 between the porous electrodes 100 and 200, the arrangement directions of the two bipolar membranes 300 are the same, and the same arrangement direction means that the cation exchange membranes 310 of each bipolar membrane 300 are oriented in the same direction, and certainly the corresponding anion exchange membranes 320 of each bipolar membrane 300 are also oriented in the same direction. It should be noted that the number of the bipolar membranes 300 is not limited to two in this embodiment, and can be flexibly set according to actual needs, and the number of the bipolar membranes 300 between the general electrode pairs is 1-50, or even more.

The desalination process of the treatment unit is shown in fig. 9, and after desalination is carried out for a period of time, reverse-pole regeneration is required to release ions in water adsorbed on the bipolar membrane, as shown in fig. 10.

In the manner of this example, desalination and regeneration can be achieved. Under the desalting condition, the porous material can adsorb anions and cations in raw water, and has no selectivity and the adsorption efficiency of about 50 percent. Under the regeneration condition, anions and cations in the porous material can be desorbed into the flow channel to realize the regeneration.

In the embodiment, the treatment unit prepares water simultaneously in all single channels during water preparation, and no concentrated water is generated. During regeneration, the regeneration can be realized by reversing the poles, and the regeneration process is also carried out in a single channel. Therefore, the waterway structure is simple.

Because the membrane area of the bipolar membrane is repeatedly utilized, the speed and the efficiency of the ion exchange are greatly improved by the electrolytic ion exchange mode. Therefore, the treatment unit adopts the structure of the porous electrode and the bipolar membrane, can avoid the problems of gas and scale formation caused by the hydrolysis of polar water in the prior art, can improve the desalination rate, and has the characteristics of high water making rate and less water resource waste. Compared with the common electrode, the whole desalting efficiency of the processing unit adopting the porous electrode can be improved by more than 8 percent.

The multistage electrodeionization device of this embodiment, it is high through setting up the desalination at the water route front end, make the big preceding stage processing unit of water yield, improve the income water quality and the life of rear stage processing unit by a wide margin, solved multistage electrodeionization device long-time operation back, the fast problem of preceding stage processing unit performance decay, and play the guard action to rear stage processing unit, thereby improve multistage electrodeionization device's whole desalination and system water yield, the life of extension complete machine, it is extravagant to reduce water resources, can reduce the filter core size simultaneously, make equipment structure compact, be applicable to industry and domestic water treatment.

Example 12.

A multi-stage electrodeionization apparatus having the same other features as in any one of embodiment 11 except that: the porous electrode 100 of the processing unit is formed by sequentially laminating a current collector 130, a porous material 110 and an anion exchange membrane 120, and the porous electrode 100 is a cathode membrane electrode; the porous electrode 200 is formed by stacking a current collector 230, a porous material 210, and a cation exchange membrane 220 in this order, and the porous electrode 200 is an anode membrane electrode, as shown in fig. 11. The porous electrode can be formed by overlapping and clamping a current collector, a porous material and an ion exchange membrane together without using a binder; or may be fixed by thermal bonding or bonded by an adhesive.

Experiments show that the porous electrode not only solves the problem of gas generation of the metal electrode, but also can realize the design of independent water outlet of the electrode chamber flow passage. And compared with the common electrode, the electrodeionization device adopting the porous electrode has the advantages that the whole desalting efficiency can be improved by more than 10 percent, and the desalting efficiency is greatly improved. This is because the porous electrode can adsorb ions of raw water, and this adsorption efficiency is higher than the ion exchange efficiency of the bipolar membrane. It can be seen that the electrodeionization apparatus of this example using porous electrodes is excellent in overall performance.

The multistage electrodeionization device of this embodiment, it is high through setting up the desalination at the water route front end, make the big preceding stage processing unit of water yield, improve the income water quality and the life of rear stage processing unit by a wide margin, solved multistage electrodeionization device long-time operation back, the fast problem of preceding stage processing unit performance decay, and play the guard action to rear stage processing unit, thereby improve multistage electrodeionization device's whole desalination and system water yield, the life of extension complete machine, it is extravagant to reduce water resources, can reduce the filter core size simultaneously, make equipment structure compact, be applicable to industry and domestic water treatment.

Example 13.

A multi-stage electrodeionization apparatus having the same other features as in any one of embodiments 1 to 12 except that: n processing units are sequentially connected in series, and N is a natural number greater than 1. Each treatment unit comprises a pair of electrode pairs and at least one bipolar membrane between two electrodes forming the electrode pairs, and the total amount of the same type of ion exchange groups in all the bipolar membranes in one treatment unit is defined as the effective value of the treatment unit.

There is at least one processing element whose valid value is greater than or equal to the valid values of the other processing elements.

The multistage electrodeionization device of the present embodiment can treat a large amount of water by the treatment unit having a large effective value, and can distribute the treatment of the water flow.

Example 14.

A water treatment apparatus having a multi-stage electrodeionization device as claimed in any one of embodiments 1 to 8, for use in industrial or domestic water treatment. Examples of uses of industrial water treatment facilities mentioned herein include, but are not limited to, industrial sewage treatment, municipal sewage treatment, seawater desalination, brine treatment, river and lake water treatment, cheese whey demineralization, and the like. The industrial water treatment apparatus includes, in addition to the bipolar membrane electrodeionization device of an embodiment of the invention, one or more of, for example, a flocculation and/or coagulation unit, an advanced oxidation unit, an adsorption unit, an electrolysis unit, a membrane separation unit (including one or more of microfiltration, ultrafiltration, nanofiltration and reverse osmosis).

The household water treatment equipment of the embodiment of the invention generally comprises one or more of an ultrafiltration unit, a nanofiltration unit, an activated carbon adsorption unit and an ultraviolet sterilization unit in addition to the multistage electrodeionization device of the embodiment of the invention.

This water treatment facilities, it is high through setting up the desalination at the water route front end, the preceding stage processing unit that the system water yield is big, improve the income water quality and the life of rear stage processing unit by a wide margin, after having solved the long-time operation of multistage electrodeionization device, the fast problem of preceding stage processing unit performance decay, and play the guard action to the rear stage processing unit, thereby improve multistage electrodeionization device's whole desalination and system water yield, the life of extension complete machine, it is extravagant to reduce water resources, can reduce the filter core size simultaneously, make equipment structure compact, be applicable to industry and domestic water and handle.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.