CN109692575B

CN109692575B - Double-chamber membrane capacitance deionization device

Info

Publication number: CN109692575B
Application number: CN201811558299.7A
Authority: CN
Inventors: 刘勇; 袁勋
Original assignee: Qingdao University of Science and Technology
Current assignee: Qingdao University of Science and Technology
Priority date: 2018-12-19
Filing date: 2018-12-19
Publication date: 2021-07-23
Anticipated expiration: 2038-12-19
Also published as: CN109692575A

Abstract

The invention belongs to the technical field of membrane capacitance deionization devices, and discloses a double-chamber membrane capacitance deionization device. The membrane capacitance deionization device is of a double-chamber structure, and the first chamber and the second chamber are respectively provided with water flow channel diaphragms at the upper end and the lower end of an anion/cation exchange membrane, so that raw water flows in a snake shape in the water flow channel diaphragms of the double chambers. The membrane deionization device has small mass transfer resistance, low desalting energy consumption and better desalting effect.

Description

Double-chamber membrane capacitance deionization device

Technical Field

The invention relates to a membrane capacitance deionization device, in particular to a double-chamber membrane capacitance deionization device.

Background

With the rapid development of the first and second industries and the growing population since the second industrial revolution, the global availability of fresh water resources and the growing demand of fresh water resources for human beings have become one of the main contradictions in the 21 st century. At present, all countries start to relieve the water resource crisis by reasonably utilizing and saving water, but conceivably, the solution is a temporary solution and a permanent solution. Therefore, how to effectively utilize four fifths of the area of ocean and lake water (i.e. seawater and brackish water) on the earth becomes an effective way for fundamentally solving the contradiction. At present, the problems of solid suspended matters, sterilization and the like of seawater and brackish water are provided with very mature technical means, and the only technical problem to be solved is to realize the desalination of the seawater and the brackish water under the condition of reasonable energy consumption.

The existing mature desalination methods for solving the above problems include the following: distillation, ion exchange, reverse osmosis, electrodialysis, and the like. With the increasing demand of human society for novel desalination technologies with high efficiency, green, low energy consumption and no secondary pollution, the Capacitive Deionization (CDI) technology has rapidly developed into a very potential desalination technology by virtue of its advantages of high efficiency, energy saving, green and no secondary pollution since the last 60 th century. The capacitive deionization technology uses a material with a large specific surface area as a capacitor electrode, uses an electric double layer generated on the surface during electrode polarization as a storage medium, and uses electric field force as a driving force to realize the aim of desalination. In the desalination process, in order to prevent the electrochemical process such as water electrolysis and the like, the voltage applied on the surface of the electrode is generally controlled below 1.23V, and it is the low-voltage operation mode that determines that the capacitive deionization technology has obvious energy consumption advantage compared with other electro-desalting technologies (such as electrodialysis); meanwhile, unlike chemical desalting processes (such as ion exchange methods), capacitive deionization technology does not need a complicated chemical regeneration process, and only needs to short-circuit devices to realize electrode regeneration, so that secondary pollution is avoided; with the thermal desalination technology (such as distillation and flash evaporation), capacitive deionization has higher energy utilization rate, and due to the above advantages, the design of the capacitive deionization unit module has become a research hotspot.

However, in the capacitive deionization process, since ions generally exist in the form of ion pairs, they do not ideally realize heterogeneous electrode adsorption, in other words, some anions are carried by cations to move to the vicinity of the negative electrode, and at the same time some cations are carried by anions to move to the vicinity of the positive electrode ("same ion adsorption"), which undoubtedly hinders the capacitive deionization process, resulting in low adsorption efficiency thereof, so that the capacitive deionization module has to be enlarged, and it is difficult to realize "flow-through" (single pass) treatment. In order to solve the problem, researchers have proposed a solution, that is, an ion exchange Membrane is added on the surface of a Capacitive deionization electrode, and the selective permeability of the ion exchange Membrane to ions is utilized to effectively inhibit the 'same ion adsorption', which is called a Membrane Capacitive Deionization (MCDI) system; for example, chinese patent CN101337717A discloses a high-efficiency energy-saving type double-chamber diaphragm capacitive deionization apparatus, which adds an ion exchange membrane between the diaphragm and the electrode, thereby greatly reducing the energy consumption and cost of the device, and chinese patent CN104817143A discloses an induction type membrane electro-adsorption module, wherein only the upper and lower metal plates are connected with a power supply, and the ion exchange membrane is added to realize low-energy desalination.

The structure of the dual-chamber membrane capacitive deionization device added with the ion exchange membrane is basically the same as that of fig. 1, however, the prior membrane capacitive deionization system has the following technical problems: firstly, ions must pass through an ion exchange membrane, which undoubtedly increases the mass transfer resistance of the ions moving in the solution, thereby improving the specific energy consumption of desalination (energy consumption for removing ions per unit mass) to a certain extent; secondly, due to the addition of the ion exchange membrane, ions also need to pass through the ion exchange membrane in the regeneration and desorption process, so that the electrode regeneration process cannot be completed through simple short circuit, reverse voltage needs to be applied, the energy consumption is further improved, and the inconvenience is brought to the energy recovery; contact resistance is generated by the contact of the ion exchange membrane and the surface of the electrode, so that part of energy is consumed in the form of heat energy, and the desalting efficiency of capacitive deionization is also hindered.

In conclusion, the double-chamber membrane capacitance deionization device which can avoid huge mass transfer resistance caused by that all ions pass through the ion exchange membrane, reduce desalination energy consumption to the maximum extent and improve desalination effect has great significance.

Disclosure of Invention

The invention provides a double-chamber membrane capacitor deionization device, aiming at solving the technical problems of large mass transfer resistance, high desalination energy consumption and poor desalination effect of the membrane capacitor deionization device in the prior art.

In order to solve the technical problems, the invention adopts the following technical scheme:

the utility model provides a two-chamber membrane capacitance deionization device, deionization device is two cavity structures, first cavity and second cavity set up rivers passageway diaphragm respectively at anion/cation exchange membrane's upper and lower both ends, make raw water be snakelike flow in the rivers passageway diaphragm of two-chamber.

Specifically, the first chamber comprises a first collector, a first electrode material, a first diaphragm, an anion/cation exchange membrane, a first diaphragm, a first electrode material and a common collector which are sequentially stacked up and down; the second chamber comprises the common collector, a second electrode material, a second diaphragm, an anion/cation exchange membrane, a second diaphragm, a second electrode material and a second collector which are sequentially stacked up and down.

The first collector, the common collector and the second collector are connected to the positive/negative pole of the DC power supply. If the ion exchange membrane of the first chamber is an anion exchange membrane, the ion exchange membrane of the second chamber is a cation exchange membrane, the first collector is connected with the anode of one direct current power supply, the second collector is connected with the anode of the other direct current power supply, and the common collector is respectively connected with the cathodes of the two direct current power supplies. If the ion exchange membrane of the first chamber is a cation exchange membrane, the ion exchange membrane of the second chamber is an anion exchange membrane, and the connection relation between each collector and the positive/negative electrodes of the two direct current power supplies is just opposite.

The collector is not particularly limited as long as it is made of a material having good chemical inertness and conductivity, and preferably, the first collector, the common collector, and the second collector provided by the present invention are plates made of graphite or titanium.

The electrode material is a carbon material with good electrochemical conductivity, high specific surface area and proper pore size distribution, preferably, the first electrode material and the second electrode material provided by the invention are carbon material films prepared from one or more of activated carbon, carbon fiber, carbon nanotube or graphene, and the carbon material films can be prepared by blade coating and other modes.

The diaphragm material needs to be made of cloth or grid made of good insulating materials, and preferably, the first diaphragm and the second diaphragm provided by the invention are selected from non-woven fabric, glass fiber cloth, polyester net or nylon net; the thickness of the first diaphragm and the second diaphragm is 100-200 mu m, and the density is larger than 300 meshes.

Preferably, the dual-chamber membrane capacitive deionization device provided by the invention further comprises reinforcing plates which are arranged above the first chamber and below the second chamber for reinforcing.

Compared with the prior art, the dual-chamber membrane capacitive deionization device provided by the invention has the following advantages: compared with the traditional single-chamber membrane capacitance deionization device, 50% of ions do not need to pass through an ion exchange membrane, so that the ion movement resistance is reduced, and low-energy-consumption desalination is finally realized; after the traditional single-chamber membrane capacitor deionization is split into double chambers, secondary treatment is equivalently carried out, the adsorption capacity of a device can be improved, and the desalting efficiency can be improved; secondly, the double-chamber membrane capacitive deionization device takes a diaphragm between an electrode material and an ion exchange membrane as a water flow channel and adopts a snake-shaped water flow flowing mode; compared with the traditional membrane capacitance deionization device, the water flow mode has obvious contact time advantage, namely, the water flow has more opportunities of contacting and adsorbing electrode materials, and the desalination efficiency of raw water is further improved; and thirdly, in the double-chamber membrane capacitive deionization device, water flows between the ion exchange membrane and the electrode, so that the regeneration process is not required to be completed through reverse voltage, and the contact resistance is inhibited, thereby further reducing the energy consumption.

Drawings

FIG. 1 is a schematic diagram of a prior art membrane capacitive deionization unit;

FIG. 2 is a schematic structural diagram of a dual-chamber type membrane capacitor deionization apparatus according to an embodiment of the present invention;

FIG. 3 is a graph comparing the instantaneous change in conductivity of a desalination process of a dual chamber membrane capacitive deionization unit according to the present invention and a conventional membrane capacitive deionization unit;

FIG. 4 is a diagram showing the desalination energy consumption of a dual-chamber membrane capacitive deionization apparatus according to the present invention and a conventional membrane capacitive deionization apparatus;

FIG. 5 is a graph of specific energy consumption and water flux for desalination processes of a dual chamber membrane capacitive deionization unit provided by the present invention and a conventional membrane capacitive deionization unit.

Detailed Description

The invention discloses a double-chamber membrane capacitance deionization device, and the technical personnel can realize the appropriate modification of parts by taking the contents as reference. It is expressly intended that all such similar substitutes and modifications which would be obvious to those skilled in the art are deemed to be included in the invention. While the methods and applications of this invention have been described in terms of preferred embodiments, it will be apparent to those of ordinary skill in the art that variations and modifications in the methods and applications described herein, as well as other suitable variations and combinations, may be made to implement and use the techniques of this invention without departing from the spirit and scope of the invention.

Example 1

As shown in fig. 2, the present invention provides a dual-chamber membrane capacitive deionization apparatus, wherein the deionization apparatus has a dual-chamber structure, and the first chamber and the second chamber are respectively provided with water flow channel diaphragms at the upper and lower ends of an anion/cation exchange membrane, so that raw water flows in a serpentine shape in the water flow channel diaphragms of the dual-chamber. Specifically, the first chamber comprises a first collector 1, a first electrode material 2, a first diaphragm 3, an anion exchange membrane 8, the first diaphragm 3, the first electrode material 2 and a common collector 4 which are sequentially stacked up and down; the second chamber comprises the common collector 4, a second electrode material 5, a second diaphragm 6, a cation exchange membrane 9, a second diaphragm 6, a second electrode material 5, a motor and a second collector 7 which are sequentially stacked up and down; the first collector electrode 1, the common collector electrode 4, and the second collector electrode 7 are connected to the positive/negative electrode of a dc power supply; the thickness of the first diaphragm and the second diaphragm is 100-200 mu m, the density is larger than 300 meshes, and reinforcing plates for reinforcing are arranged above the first chamber and below the second chamber.

The first collector electrode, the common collector electrode and the second collector electrode are made of graphite or titanium plates; the first electrode material and the second electrode material are carbon material films prepared from one or more of activated carbon, carbon fiber, carbon nano tube or graphene; the first membrane and the second membrane are selected from non-woven fabric, glass fiber cloth, polyester net or nylon net.

Example 2

A NaCl solution with a concentration of 3000mg/L is passed through the first diaphragm at the upper end of the first chamber described in embodiment 1 from a water storage tank of 20L by using a constant flow pump, and the conductivity is measured and converted into the concentration at the water outlet of the second diaphragm at the lower end of the second chamber, when the concentration at the water outlet is stable, a direct current voltage of 1.2V is applied between three collectors, when the concentration returns to the initial concentration again, the collector is in an adsorption period, at this time, the collector is in a short circuit, the concentration change condition of the treatment process is shown as a solid line in fig. 3, and the dotted line in fig. 3 is a conductivity change curve of the desalination process of the conventional membrane-capacitor deionization membrane.

The data in fig. 3 shows that the ion concentration of both devices starts to decrease and slowly rises to the initial value after the external voltage is applied, the adsorption process is completed, and after the two electrodes are short-circuited, the ion concentration is rapidly increased, the regeneration of the electrodes is realized.

Example 3

The inventors simply scaled up the apparatus of example 1 and performed a multi-mode performance test (10 sets): connecting 10 groups of the double-chamber membrane capacitor deionization devices described in embodiment 1 in series, connecting 10 groups of traditional membrane capacitor deionization devices in series, respectively passing NaCl solution with concentration of 1000, 2000 and 3000mg/L from a 20L water storage tank through 10 groups of the double-chamber membrane capacitor deionization device series modules and the traditional membrane capacitor deionization device series modules by using a constant flow pump, measuring conductivity at a water outlet and converting the conductivity into concentration, applying 1.2V direct-current voltage between three collecting electrodes when the concentration of the water outlet is stable, and testing current and voltage (used for calculating energy consumption) in the treatment process between the modules; the energy consumption ratio of the module and the traditional membrane capacitance deionization device in the invention for processing a unit cubic meter of NaCl solution to 500mg/L is shown in FIG. 4; fig. 4 shows that the dual-chamber membrane capacitive deionization apparatus provided by the present invention has absolute energy consumption advantages at each concentration compared to the conventional membrane capacitive deionization apparatus, and the energy consumption per ton treatment is respectively: 0.25, 0.49 and 1.05 kWh.

Example 4

The inventors further scaled the device of example 1 to a larger module size and performed a multi-module performance test (20 modules): 20 groups of double-chamber membrane capacitor deionization devices are connected in series, 20 groups of traditional membrane capacitor deionization devices are connected in series, NaCl solution with the concentration of 3000mg/L is respectively led to pass through 20 groups of double-chamber membrane capacitor deionization device series modules and 20 groups of traditional membrane capacitor deionization device series modules from a 20L water storage tank at the flow rate of 20-60ml/min by a constant flow pump, and the conductivity is measured at the water outlet and converted into the concentration, when the concentration of the water outlet is stabilized at 3000mg/L, constant current of 0.5-2.5A is applied between the three collectors to control the desalination concentration difference to be 500, 1000, 2000mg/L, and the current and voltage during the treatment were tested between modules (for calculating energy consumption), the specific energy consumption (J/mg) and water flux (μm/s) of the desalination treatment of the dual-chamber membrane capacitive deionization apparatus of the present invention and the conventional membrane capacitive deionization apparatus are shown in fig. 5; fig. 5 shows that as the current applied to the module increases, the overall treatment flux of the module increases greatly, however, the specific energy consumption of the treatment increases at the same time, and on the premise of realizing a certain water flux, the treatment concentration difference increases, and the specific energy consumption of the treatment of the module also increases; it is clear that the dual chamber membrane capacitive deionization unit provided by the present invention has an absolute advantage in specific energy consumption over the conventional membrane capacitive deionization unit, while achieving the same concentration and water flux.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A dual chamber membrane capacitive deionization device, comprising: the deionization device is of a double-chamber structure, and the first chamber and the second chamber are respectively provided with water flow channel diaphragms at the upper end and the lower end of the anion/cation exchange membrane, so that raw water flows in a snake shape in the water flow channel diaphragms of the double chambers; the first chamber comprises a first collector, a first electrode material, a first diaphragm, an anion/cation exchange membrane and a first diaphragm which are sequentially stacked up and down, the first electrode material and a common collector; the second chamber comprises the common collector, a second electrode material, a second diaphragm, an cation/anion exchange membrane, a second diaphragm, a second electrode material and a second collector which are sequentially stacked up and down; the first collector electrode, the common collector electrode, and the second collector electrode are connected to a positive/negative electrode of a direct current power supply.

2. The dual chamber membrane capacitive deionization device of claim 1 wherein: the first collector electrode, the common collector electrode and the second collector electrode are plates made of graphite or titanium.

3. The dual chamber membrane capacitive deionization device of claim 1 wherein: the first electrode material and the second electrode material are carbon material films prepared from one or more of activated carbon, carbon fiber, carbon nano tube or graphene.

4. The dual chamber membrane capacitive deionization device of claim 1 wherein: the first membrane and the second membrane are selected from non-woven fabric, glass fiber cloth, polyester net or nylon net.

5. The dual-chamber membrane capacitive deionization device of claim 1 or 4 wherein: the thickness of the first diaphragm and the second diaphragm is 100-200 mu m, and the density is larger than 300 meshes.

6. The dual chamber membrane capacitive deionization device of claim 1 wherein: the device also comprises reinforcing plates which are arranged above the first cavity and below the second cavity and play a reinforcing role.